Mechanical Prasad

Environmental Science Project

noreply@blogger.com (Prasad Ghorpade) — Fri, 02 Nov 2012 10:31:00 +0000

CLIMATE CHANGE: PAST, PRESENT & FUTURE
Ocean currents transport heat around the Earth and influence regional climate as they warm or cool the air above the seas. The major surface ocean currents travel in the same direction as the major wind belts because the wind pushes the seawater. For example, the westerly winds drag North Pacific water from west to east, while the trade winds move surface currents from east to west both north and south of the equator. When these currents run into continents, the Coriolis effect causes them to turn right in the Northern Hemisphere and left in the Southern Hemisphere. The currents flow along the continents until they run into an east-west moving current going in the opposite direction. The result is surface currents that travel in loops called gyres, which rotate clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.

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The North Atlantic gyre has an enormous influence on the climate of northern Europe. At the southern part of this gyre, seawater is warmed by the Sun as it moves from east to west across the equator. When it hits the Americas, the current turns right (north) and becomes the Gulf Stream, swift warm water current that raises air temperatures along the eastern United States and southeastern Canada. At the northern part of the gyre, the Gulf Stream swings right, away from North America and toward Europe, where it divides into two segments. One segment Moves south toward Africa, completing the gyre, while the other moves north, along Great Britain and Norway. The northern current, called the North Atlantic Drift, brings fairly warm Gulf Stream water into the northern latitudes. This current creates air temperatures in the North Atlantic that are 5°F to 11°F (3° to 6°C) warmer than those of other regions at the same latitudes. As a result, although London is at 51° north latitude, several degrees farther north than Quebec, Canada, its climate is much more temperate: Rain instead of snow predominates in London during winter. Besides influencing air temperature, ocean currents also affect precipitation levels because warm water currents bring more moisture and therefore more rain to a region than do cold currents.

CLIMATE CHANGE: PAST, PRESENT & FUTURE

TABLE OF CONTENTS
CHAPTER NO. TITLE PAGE NO.

ABSTRACT v
LIST OF TABLE vii
LIST OF FIGURES vii

1. INTRODUCTION 01

1.1 Earth’s Atmosphere 01
1.2 Earth’s Energy Balance 03
1.3 What Shapes A Region’s Climate? 04
A) Latitude 04
B) Atmospheric Circulation 04
C) The Effects Of The Ocean On Climate 05
D) Altitude And Albedo 07
1.4 The Carbon Cycle 08

2. NATURAL CAUSES OF CLIMATE CHANGE 11
2.1 Milankovitch Cycles 11
2.2 Human Causes Of Climate Change 13
2.3 Land Use Changes 14
2.4 Global Dimming 14

3. CLIMATE CHANGE THROUGH EARTH HISTORY 16

3.1 Ancient Climate 16
3.2 Paleocene Eocene Thermal Maximum 16
3.3 The Pleistocene Ice Ages 17

4. CLIMATE CHANGE IN HUMAN HISTORY 19

5. CLIMATE NOW 23
5.1 Recent Climate 23
5.2 Causes Of Recent Climate Change 25

6. EFFECTS OF CLIMATE CHANGE ON THE  ATMOSPHERE AND HYDROSPHERE 28
6.1 Effects Of Climate Change On Cryosphere 28
6.2 Effects Of Climate Change On Oceans 29

7. THE TIPPING POINT 31
7.1 What Is The Tipping Point? 31
7.2 The Loss Of Major Ice Sheets And Rising Sea Level 31
7.3 An Ice Age For Europe 32
7.4 Species Extinctions 32
7.5 Human Civilization 34
CONCLUSION 36
REFERENCE 37

Clamping Fixtures

noreply@blogger.com (Prasad Ghorpade) — Thu, 01 Nov 2012 12:53:00 +0000

Simple plate Clamp

Retractable Strap Clamp

Pivoted Clamps

Pivoted Two-way Clamp

Hinged Clamp

Abrasive Flow Machining

noreply@blogger.com (Prasad Ghorpade) — Thu, 25 Oct 2012 00:27:00 +0000

Abrasive ﬂow machining (AFM) is the removal of material by a viscous, abrasive medium ﬂowing, under pressure, through or across a work piece. Generally, the putty-like medium is extruded through or over the workpiece with motion usually in both directions. Aluminum oxide, silicon carbide, boron carbide, or diamond abrasives are used. The movement of the abrasive matrix erodes away burrs and sharp corners and polishes the part.

Engineering Project For PPT

noreply@blogger.com (Prasad Ghorpade) — Mon, 08 Oct 2012 08:22:00 +0000

Ion Propulsion for Deep Space Exploration

Abstract – Day by day, as we are using natural resources and depleting them at very fast rate knowing that we have only one home “The Earth” to live on. So all research now concentrated to find places for development of our civilization other than earth. Only problem is that other planets are so far from us that it took months & years to reach them. Some are outside of solar system and it took thousands of years to reach them. Is there any technology which will avail us to go faster than ever in space? Answer is “Ion Propulsion”. In the year 1998 NASA tested it practically, project named as “DS1 i.e. Deep Space 1”.

Conventional rocket burns fuel at the rate of 10,000 kg/sec. to escape in space, so we have to build rockets with 1,000,000 kg fuel capacity. Almost all energy lost to give the thrust to weight of fuel itself. And all this fuel gets burned out in merely 2 minutes!

The ion propulsion system on DS1 carries about 81.5 kilograms of xenon propellant, and it takes about 20 months of thrusting to use it all. It increases the speed of the spacecraft by 4.5 km/s or about 16,200 kilometers per hour. If we had the same amount of chemical propellant, it would provide only one tenth as much velocity increment. By using Ion Propulsion for long time say 10-15 years our spacecrafts may attain incredible speed of 100km/sec and more.

Technology is still under development, may be my grand children’s and yours will live in different future than our imagination, and somewhere else other than Planet Earth.

What is a propellant?

Rockets work because every action has an equal and opposite reaction (according to Sir Issac Newton's third principle). In order for.....

the rocket to rush forward, something has to rush backwards. That thing is the propellant. The propellant is a material that spews out of the back of the spacecraft giving it thrust, or a push forward.

Often the propellant is a kind of fuel which is burned with an oxidizer to produce large volumes of very hot gas. These gasses expand until they rush out of the back of the rocket, making thrust. Sometimes the propellant is not burned, but pushed directly out of the spacecraft, making thrust. In ion propulsion, the propellant is made of electrically charged atoms, which are magnetically pushed out of the back of the spacecraft. For smaller attitude control thrusters, a compressed gas is pushed out of the spacecraft.

How do conventional rockets work?

Conventional rockets are the kind of rockets you imagine if you think of the space shuttle lifting off, There is a huge rumble and great clouds of gasses and flame, which provide a huge amount of thrust to push something off of Earth into space.

Conventional rockets, like any rocket, jet airplane, firework or released balloon, work through a phenomenon called propulsion. Basically, the rocket is pushed forward because material is streaming out of the back of it. Most conventional rockets work through superheated gasses being pushed out of the back of them. These gasses are formed by burning fuel in the presence of oxygen, or another substance called an oxidizer that allows burning to happen.

How does propulsion work?

Propulsion moves things like spacecraft or jet planes forward by pushing something out of the back. Think of a balloon that you blow up and then release. The air rushing out of the back pushes the balloon forward. This happens because of a phenomenon described by Sir Issac Newton: "every action has an equal and opposite reaction."

What is an atom?

An atom a fundamental piece of matter. (Matter is anything that can be touched physically.) Everything in the universe (except energy) is made of matter, and, so, everything in the universe is made of atoms.

An atom itself is made up of three tiny kinds of particles called subatomic particles: protons, neutrons, and electrons. The protons and the neutrons make up the center of the atom called the nucleus and the electrons fly around above the nucleus in a small cloud. The electrons carry a negative charge and the protons carry a positive charge. In a normal (neutral) atom the number of protons and the number of electrons are equal. Often, but not always, the number of neutrons is the same, too.

The negative electrons are attracted to the positive nucleus by the same electrical force which causes magnets to work. That's what keeps the atom together.

What is an ion?

An ion is a charged atom or molecule. It is charged because the number of electrons do not equal the number of protons in the atom or molecule. An atom can acquire a positive charge or a negative charge depending on whether the number of electrons in an atom is greater or less then the number of protons in the atom.

When an atom is attracted to another atom because it has an unequal number of electrons and protons, the atom is called an ION. If the atom has more electrons than protons, it is a negative ion, or ANION. If it has more protons than electrons,it is a positive ion.

How are atoms charged?

A charged atom has either too many or too few electrons. In DS1, atoms are heated until they are very high energy and unstable. The are then hit by electrons that are discharged by a cathode ray in the thruster chamber. When the electrons hit the atoms in the chamber, they cause some of the electrons in the atoms to be stripped or knocked away. The mass of superheated, charged atoms with disassociated electrons becomes a plasma.

When one or more electrons is knocked off of an atom, it becomes positively charged. It is now an positive ion. A negative ion can be made by adding an electron to an atom.

What is plasma?

Plasma is considered the fourth state of matter. The three other states are solid, liquid, and gas. Plasma is a cloud of protons, neutrons and electrons where all the electrons have come loose from their respective molecules and atoms, giving the plasma the ability to act as a whole rather than as a bunch of atoms. A plasma is more like a gas than any of the other states of matter because the atoms are not in constant contact with each other, but it behaves differently from a gas. It has what scientists call collective behavior. This means that the plasma can flow like a liquid or it can contain areas that are like clumps of atoms sticking together.

How can something as small as an atom move a space craft?

Anything with a propulsion system works when something (usually a gas--sometimes a liquid) pushes out of it. This makes thrust. Any gas or liquid is made of atoms, so jet engines, the space shuttle, and Fourth of July fireworks are all pushed forward by atoms shooting out of them.

Everything from fireworks to space shuttles are moved by atoms. There are two important factors: how many atoms are being used and how fast they are going. In space shuttle launches, the fuel flow rate at launch is about 10 tons a second. This means that for each second of the launch a space shuttle burns 10 tons of fuel. That's a huge amount of atoms! By contrast, Deep Space 1 will carry about 81.5 kilograms (179 pounds) of propellant total, and it will take about 20 months of thrusting to use all of that. That's millions of times fewer atoms. DS1 is able to make thrust using many millions fewer atoms for fuel because it accelerates them to a much higher speed before shooting them out.

How does DS1's engine work?

DS1 is a real spacecraft that launched on October 24, 1998.

DS1's engine makes thrust by magnetically charging atoms and then repelling them from the spacecraft. This stream of atoms spewing out the back of the thruster pushes DS1 forward. Solar power provides the energy. The process is like this:

1. Xenon atoms are injected into the propulsion chamber. They are heated and bombarded with electrons until they form a plasma, with electrons separated from the cores of the atoms, which become xenon ions.

2. The positively charged xenon ions move towards the back of the chamber.

3. Once they are between the positive and negative grids at the very back of the chamber, they are electrostatically accelerated away from the positive grid and towards the negative one.

4. Since the push from the positive grid on the positive ions is much greater than the pull of the negative grid towards the positive ions, they shoot past the negative grid and out into space at a high speed.

5. The expelled ions propel the ship forward.

6. Electrons are shot from a cathode towards the ions behind the ship. The ions are neutralized, and the xenon atoms float away.

Where does DS1 get its electricity?

DS1 has solar panels that collect the Sun's light energy and convert it into electricity. The more light they receive, the more electricity they can make. If the panels get turned away from the Sun, even by a small amount, the efficiency of the solar collectors greatly decreases.

In most circumstances, all efforts are made to keep the solar panels pointed directly at the Sun. When it isn't possible to point the panels straight at the Sun (such as when the probe is hidden from the Sun by a planet or meteorite, or is forced to point in a different direction for a science experiment) DS1 switches to batteries for its power. When the solar panels are directly facing the Sun, there is often more electricity made than can be used at that moment. The batteries are charged during those times. New in DS1 is technology called a solar concentrator, which is a kind of lens that intensifies the amount of light getting to the solar panels. This makes the solar panels much more useful.

As a spacecraft gets farther from the Sun, it's solar panels can make less and less electricity. Usually by the time a spacecraft gets to Mars, there isn't enough light to make electricity. DS1's power will drop off after DS1 gets past Mars.

How fast can the ion engine go?

The ion engine has a small amount of thrust, so it takes a long time to get up to speed. When the ion propulsion system begins operation, DS1 will be in LEO (low Earth orbit) and moving at a slow stately pace (for spacecraft) of about 17,000 mph. The ion engine will then take 15 months and increase the speed of the satellite by 8000 miles per hour. This will top the satellite out at around 25,000 mph after about 15 months.

Why do ion engines need a vacuum to work?

Ion propulsion engines work because you can make a plasma in the chamber. This means that electricity has to flow through the chamber. Air is an insulator, which means that it keeps electricity from flowing. Ion propulsion can only work when there is little or no air pressure in the chamber. The amount of pressure is important because a gas can only ionize, or become electrically charged, at low pressures. This is because the more gas or air there is in the chamber, the more the electrons that are suppose to ionize the atoms in the chamber bump into the air and not the atoms. A vaccuum is a totally empty space--there is no air pressure to stop the electrons if there is no air.

What is the difference between an ion engine and a conventional one?

Both kinds of rockets move the ship forward by making thrust. This thrust is made by propelling matter out of the back of the ship. Ion engines are different from chemical engines (engines that work by burning liquid or solid fuel) in where they get their energy and how they produce thrust.

Chemical engines work by combining fuel with an oxidizer. That makes a gas that expands and rushes out the back of the engine, making thrust. Chemical engines are mass-limitedengines. What this means is that how much power a chemical engine has depends on is how much fuel and oxidizer the rocket can carry. When the propellant runs out then the rocket cannot go any faster.

However, ion engines work differently than chemical engines. Ion engines take very small amounts of gas and accelerate it to very high speeds, unlike chemical engines which take large amounts of gas and spew it out at a slow speed. This means that an ion engine uses a lot less fuel. Ion engines are limited by energy, not by mass. Therefore "running out of gas" is not a large problem with ion engines. The limit for ion engines is usually where to get all the electricity to feed the ion engine. Ion engines are limited by how much energy (electricity) that a rocket can carry or how much energy the solar panels can collect.

Why does DS1 have two types of propulsion?

DS1 carries two different propulsion systems:

• Solar-powered ion propulsion system--this pushes DS1 forward.

• Hydrazine control thrusters--these help steer DS1.

DS1 systems serve different purposes. The ion propulsion engine serves to push DS1 forward more quickly so that DS1 can get to where it needs to go in time to meet the objects in space it is supposed to meet. The hydrazine thrusters are used to control the spacecraft's attitude (the direction it is pointing in 3 dimensions). Once the spacecraft is pointed in a different direction, the main thruster can push it in that new direction.

DS1 cannot do both jobs with one kind of thruster. It is not possible to change the direction of the Solar Ion Propulsion thrust so it cannot be used for changing the ship's attitude. The hydrazine thrusters are not strong enough to be the main thruster. They will not increase DS1's speed enough to get it to where it is going.

Sheet-Metal Gears

noreply@blogger.com (Prasad Ghorpade) — Wed, 08 Aug 2012 16:43:00 +0000

Sheet-Metal Gears, Sprockets, Worms, And Ratchets For Light Loads :
When a speciﬁed motion must be transmitted at intervals rather than continuously, and the loads are light, these mechanisms are ideal because of their low cost and adaptability to mass production.

1) The sheet-metal wheel gear meshes with a wide-face pinion, which is either extruded or machined. The wheel is blanked with teeth of conventional form.

2) A sheet metal cup with indentations replacing worm-wheel teeth, meshes with a standard coarse-thread screw.

3) The pinion is a sheet metal cup with rectangular holes serving as teeth. The meshing gear is sheet metal, blanked with specially formed teeth. The pinion can be attached to another sheet metal wheel by prongs, as shown, to form a gear train......

4) The pinion mates with round pinson a circular disk made of metal, plastic or wood. The pins can be attached by staking or with threaded fasteners.

5) The horizontal wheel with waves on its out rim replacing teeth, meshes with either one or two sheet-metal pinions. They have specially formed teeth and are mounted on intersecting axes.

6) Two bevel-type gears, with specially formed teeth, are mounted on 90° intersecting axes. They can be attached by staking them to hubs.

7) The blanked and formed bevel-type gear meshes with a machined or extruded pinion. Conventional teeth can be used on both the gear and pinion.

8) The blanked, cup-shaped wheel meshes with a solid pinion on 90° intersecting axes.

9) Two blanked gears, conically formed after blanking, become bevel gears meshing on a parallel axis. Both have specially formed teeth.

10) A blanked wheel, with specially formed teeth, meshes with a helical spring mounted on a shaft, which serves as the worm.

11) This worm wheel is blanked from sheet metal with specially formed teeth. The worm is a sheet-metal disk that was split and helically formed.

12) Blanked ratchets with one-sided teeth are stacked to ﬁt a wide-sheet-metal ﬁnger when single thickness is inadequate. The ratchet gears can be spot-welded.

13) To avoid stacking, a single ratchet is used with a U-shaped ﬁnger, also made of sheet metal.

14) This wheel is a punched disk with square-punched holes serving as teeth. The pawl is spring steel.

15) This sheet-metal blanked pinion, with specially formed teeth, meshes with windows blanked in a sheet metal cylinder. They form a pinion-and-rack assembly

16) For a wire chain as shown, the sprocket is made by bending out punched teeth on a drawn cup.

Special Screw Arrangements

noreply@blogger.com (Prasad Ghorpade) — Tue, 17 Jul 2012 15:40:00 +0000

Differential, duplex, and other types of screws can provide slow and fast feeds, minute adjustments, and strong clamping action.

1) Rapid and slow feed. With left- and right-hand threads, slide motion with the nut locked equals LA plus LB per turn; with the nut ﬂoating, slide motion per turn equals LB. Extremely ﬁne feed with a rapid return motion is obtained when the threads are differential.

2) Differential clamp. This method of using a differential screw to tighten clamp jaws combines rugged threads with high clamping power. Clamping pressure, P = Te [R(tan (Fi) + tan (alpha)], where T = torque at handle, R = mean radius of screw threads, Fi = angle of friction (approx. 0.1), Alpha = mean pitch angle or screw, and e = efﬁciency of screw generally about 0.8).

3) Extremely small movements. Microscopic measurements, for example, are characteristic of this arrangement. Movement A is equal to N(LB X Lt ) 12(Pi)R, where N equals.....................
the number of turns of screw C.

4) Bearing adjustment. This screw arrangement is a handy way for providing bearing adjustment and overload protection.

5) Shock absorbent screw. When the springs coiled as shown are used as worm drives for light loads, they have the advantage of being able to absorb heavy shocks.

6) Backlash elimination. The large screw is locked and all backlash is eliminated when the knurled screw is tightened; ﬁnger torque is sufﬁcient.

7) High reduction of rotary motion to ﬁne linear motion is possible here. This arrangement is for low forces. Screws are left and right hand. LA = LB plus or minus a small increment. When LB = 1/10 and LA = 1/10.5, the linear motion f screw A will be 0.05 in. per turn.When screws are the same hand, linear motion equals LA + LB.

Latch, Toggle, And Trigger Devices

noreply@blogger.com (Prasad Ghorpade) — Mon, 11 Jun 2012 10:52:00 +0000

Also look for amazing post

Types Of Rivet Heads And Rivet Joints

A latch mounted on a cocking lever allows both levers to be reached at the same time with one hand. After release, the cocking spring initiates clockwise lever movement; then gravity takes over.

A disk-shaped cocking has a tension spring resting against the cylindrical hub. Spring force always acts at a constant radius from the lever pivot point.

A sleeve latch

(A) as an L-shaped notch. A pin in the shaft rides in a notch. Cocking requires a simple push and twist action.

(B) The Latch and plunger depend on axial movement for setting and release. A circular groove is needed if the plunger is to rotate.

A geared cocking device has a ratchet ﬁxed to a pinion. A torsion spring exerts clockwise force on the spur gear; a tension spring holds the gar in mesh. The device is wound by turning the ratchet handle counterclockwise, which in turn winds the torsion spring. Moving the release-lever permits the spur gear to unwind to its original position without affecting the ratchet handle.

In this overcenter lock

(A) clockwise movement of the latching lever cocks and locks the slide. A counterclockwise movement is
required to release the slide.

(B) A latching-cam cocks and releases the cocking lever with the same counterclockwise movement as (A)

A spring-loaded cocking piece has chamfered corners. Axial movement of the push-rod forces the cocking piece against a spring-loaded ball or pin set in a frame.When cocking builds up enough force to overcome the latch-spring, the cocking piece snaps over to the right. The action can be repeated in either direction.

A ﬁring-pin mechanism has a beveled collar on a pin. Pressure on the trigger forces the latch down until it releases the collar when the pin snaps out, under the force of cocking the spring.
A reset spring pulls the trigger and pin back. The latch is forced down by a beveled collar on a pin until it snaps back, after overcoming the force of the latch spring. (A latch pin retains the latch if the trigger and ﬁring pin are removed.)

Cam-guided latch

(A) has one cocked, and two relaxed positions,

(B) Simple overcenter toggle action.

(C) An overcenter toggle with a slotted link.

(D) A double toggle action often used in electrical switches.

An identically shaped cocking lever and latch

(A) allow their functions to be interchangeable. The radii of the sliding faces must be dimensioned for a mating ﬁt. The stepped latch

(B) offers a choice of several locking positions.

Electrically Driven Hammers

noreply@blogger.com (Prasad Ghorpade) — Mon, 21 May 2012 12:44:00 +0000

The application of controlled impact forces can be as practical in specialized stationary machinery as in the portable electric hammers shown here. These mechanisms have been employed in vibrating concrete forms, nailing machines, and other special machinery. In portable hammers they are efﬁcient in drilling, chiseling, digging, chipping, tamping, riveting, and similar operations where quick, concentrated blows are required. The striker mechanisms illustrated are operated by springs, cams, magnetic force, air and vacuum chambers, and centrifugal force. The drawings show only the striking mechanisms.

This spring-operated hammer with a cam and rocker for the return stroke has a screw for adjusting the blow to be imparted

This combination of mechanical, pneumatic, and spring action is included in this hammer.

The striker has no mechanical connection with the reciprocating drive in this hammer.

Two electromagnets operate this hammer. The weight of the blows can be controlled by varying the electric current in the coils or timing the current reversals by an air-gap adjustment of the contacts.

This spring-operated hammer includes a shaft rotating in a female cam to return the striker.

This spring-operated hammer has two ﬁxed rotating-barrel cams. They return the striker by means of two rollers on the opposite sides of the striker sleeve. Auxiliary springs prevent the striker from hitting the retaining cylinder. A means of rotating the tool, not shown, is also included in this hammer.

Two steel balls rotated in a divided cylinder and steered by an edge cam develop centrifugal force to strike blows against the tool holder. The collar is held clear of the hammer by a compression spring when no tool is in the holder. A second spring cushions the blows when the motor is running, but the tool is not held against the work.

A free-driving throw of the cam-slotted striker is produced by the eccentric stud roller during contact between points A and B of the slot. This accelerates the striker beyond the tangential speed of the roller for an instant before the striker is picked up for the return stroke.

The centrifugal force of two oppositely rotating weights throws the striker assembly of this hammer. The power connection is maintained by a sliding-splined shaft. The guide, not shown, prevents the rotation of the striker assembly

Water jet machine

noreply@blogger.com (Prasad Ghorpade) — Sat, 07 Apr 2012 20:06:00 +0000

It is hard to believe that a jet of water can cut steel and granite. However, in scientific terms, it is explainable, where a stream of water is propelled at high pressure (2000 to 8000 bar) through a converging nozzle to give a coherent jet of water of high speed of 600–1400 m/s. At the target, the kinetic energy (KE) of the jet is converted spontaneously to high-pressure energy, inducing high stresses exceeding the flow strength of target material, causing mechanical abrasion.

Simplified layout of WJM equipment:

A typical ultrahigh-pressure water-jet cutting system consists of two stages of pumping equipment, a high-pressure water-jet delivery system, a mechanical manipulator for motion control, and a discharge catcher system. The ﬁrst stage of pumping is carried out by a radial displacement pump, which can pressurize the hydraulic oil up to 3000 lb/in2 (20.7 megapascals). The hydraulic oil then drives an intensiﬁer pump. The typical intensiﬁcation ratio of this piston type of pump is 1:20, which is the area ratio of two ends of the piston. The intensiﬁer pump can pressurize water up to 60,000 lb/in2 (414 MPa). The tap water supplied to the intensiﬁer pump passes through several stages of ﬁlters (10-0.5-micrometer range) at a boosted water-feed pressure of 80 lb/in2 (0.555MPa). The high-pressure water from the intensiﬁer pump is channeled through an accumulator to level off pressure ﬂuctuations created by the plunger motion of the pump. The pressurized water is then carried to a cutting station by means of stainless-steel high-pressure tubing and swivel joints or by a ﬂexible high-pressure hose which can withstand pressures up to 100,000 lb/in2 (690 MPa).

The high-pressure water delivered to a nozzle assembly is ﬁrst converted into a high-speed jet through an oriﬁce assembly which houses an on–off control valve and oriﬁce. The jet created through the oriﬁce can be manipulated by motion-control equipment such as a robot or x-y table to cut a desired shape of work piece.

A mixture of water and abrasives is used for cutting hard materials. Garnet is the most commonly used abrasive in industrial cutting operations. Other abrasives such as aluminum oxide, silicon carbide, silica sand, glass bead, and steel grit are also used in special-purpose cutting and cleaning operations. The rate of workpiece erosion, and therefore the cutting efﬁciency, is very dependent on the material used. Aluminum oxide is an ideal abrasive for cutting brittle materials such as advanced ceramics and stones, yielding a twofold increase in cutting power as compared to garnet. However, aluminum oxide is not much more effective than garnet for cutting ductile materials. The abrasive size and ﬂow rate also greatly affect the quality of the cut surface as well as the cutting efﬁciency. The range of mesh sizes commonly used for industrial applications is 50–120 (particle size 300-125 µm or 0.012–0.005 in.), and the range of abrasive ﬂow rates is 0.5–1.5 lb/min (3.8–11.4 g/s).

WJM has the following advantages:

• Water is cheap, nontoxic, and can be easily disposed and recirculated.

• The process requires a limited volume of water (100–200 L/h).

• The tool (nozzle) does not wear and therefore does not need sharpening.

• No thermal degrading of the work material, as the process does not generate heat. For this reason, WJM process is best suited for explosive environments.

• It is ideal for cutting asbestos, glass fiber insulation, beryllium, and fiber-reinforced plastics (FRP), because the process provides a dustless atmosphere. For this reason, the process is not hazardous and is environmentally safe.

• The process provides clean and sharp cuts that are free from burrs. It is applicable for laser-reflective materials such as glass, copper, and aluminum.

• Starting holes are not needed to perform the cut.

• Wetting of the WP material is minimal.

• Noise is minimized, as the power unit and intensifier can be kept away from the cutting station.

• Although AJM is commonly used to cut only brittle materials, it is able to machine both brittle and ductile materials.

• The WP is subjected to a limited mechanical stress, as the force exerted by the jet does not generally exceed 50 N.

• In WJM, cutting is performed without the need of using elaborate fixturing of the WP.

• WJM approaches the ideal single-point tool.

WJM has the following disadvantages:

• WJM is unsafe in operation if safety precautions are not strictly followed.

• The process is characterized by high production cost due to The high capital cost of the machine and The need for highly qualified operators

• WJM is not adaptable to mass production because of the high maintenance requirement

WJM is used in many industrial applications comprising the following:

1. Cutting of metals and composites applied in aerospace industries.

2. Underwater cutting and ship building industries.

3. Cutting of rocks, granite, and marble.

4. It is ideal in cutting soft materials such as wood, paper, cloth, leather, rubber, and plastics.

5. Slicing and processing of frozen foods, backed foods, and meat. In such cases, alcohol, glycerin, and cooking oils are used as alternative cutting fluids.

6. WJM is also used in

-Cleaning, polishing, and degreasing of surfaces

-Removal of nuclear contaminations

-Cleaning of tubes and castings

-Surface preparation for inspection purposes

-Surface strengthening

-Deburring

Bibliography.

McGraw-Hill - Encyclopedia of Science and Tech 10th Edition Vol 19 U-ZYG (pp. 418/19)

Machining Technology Machine Tools and Operations- Helmi A. Youssef (pp. 396-399)

Abrasive Jet Machine

noreply@blogger.com (Prasad Ghorpade) — Sat, 07 Apr 2012 07:47:00 +0000

Abrasive jet machining (AJM) is the removal of material through the action of a focused, high-velocity stream of ﬁne grit or powder-loaded gas. The gas should be dry, clean, and under modest pressure. The mixing chamber sometimes uses a vibrator to promote a uniform ﬂow of grit. The hard nozzle is directed close to the workpiece at a slight angle. In abrasive jet machining (AJM), a fine stream of abrasives is propelled through a special nozzle by a gas carrier (CO2, Ni, or air) of pressure ranging from 1 to 9 bar. Thus, the abrasives attain a high speed ranging from 150 to 350 m/s, exerting impact force and causing mechanical abrasion of the WP (target material). The WP is positioned from the nozzle at a distance called the stand-off distance (SOD), or the nozzle-tip distance (NTD) as shown.

In AJM, Al2O3 or SiC abrasives of grain size ranging from 10 to 80 µm are used. The nozzles are generally made of tungsten carbides (WC) or synthetic sapphires of diameters 0.2–2 mm. To limit the jet flaring, nozzles may have rectangular orifices ranging from 0.1 × 0.5 mm to 0.18 × 3 mm.

shows a typical workstation of AJM, which is connected to a gas supply (gas bottles or compressed air). The carrier gas must not l are excessively when discharged from nozzle to atmosphere. Furthermore, it should be nontoxic, cheap, available, and capable of being dried and filtered. Air is widely used owing to its availability. In small stations, CO2 and N2 gas bottles are commonly used. After filtering, the pressure of the compressed gas of 7–9 bars is regulated, to suit the working conditions. The gas is then introduced in to the mixing chamber containing the abrasives. The chamber is equipped with a vibrator providing an amplitude ξ of 1–2 mm at a frequency from 5 to 50 Hz. The abrasive flow rate is controlled through the adjustment of ξ and fr From the mixing chamber, the gas/abrasive mixture is directed to the nozzle that directs the jet onto the target or WP. The jet velocity of 150–350 m/s depends upon the gas pressure at the nozzle, the orifice diameter of the nozzle, and the mixing ratio. The flow rate of a typical working station is about 0.6 m3/h, which is controlled through a foot control valve.

The nozzle is mounted in a special fixture, and sometimes held in hand, depending on the type of operation required (cutting, trimming, engraving, frosting, or cleaning). When machining thin-walled fragile materials, it may be necessary to control the relative motion between the nozzle and the work by a cam and pantograph, depending upon the required size and shape of cut. The AJM-station must be equipped with a vacuum dust collector to limit the pollution. Strict measures and precautions should be undertaken in case of machining toxic materials such as beryllium to collect produced dust and debris.

Advantages of AJM include the following:

-Capable of producing holes and intricate shapes in hard and brittle materials.

-Used to cut fragile materials of thin walls.

-Heat-sensitive materials such as glass and ceramics can be machined without affecting their physical properties and crystalline structure, as no or little heat is generated during

machining.

-Safe to operate.

-Characterized by low capital investment and low power consumption.

-Can be used to clean surfaces, especially in areas that are inaccessible by ordinary methods.

-The produced surfaces after cleaning by AJM are characterized by their high wear resistance.

Limitations of AJM include the following:

-The application of AJM is restricted to brittle materials. It is not recommended for machining soft and malleable materials.

-Abrasives cannot be reused because they lose their sharpness and hence their cutting

ability.

-Nozzle clogging occurs if i ne grains having a diameter dg <10 µm are used.

-The process accuracy is poor due to the l aring effect of the abrasive jet.

-Deep holes are produced by signii cant taper.

-Sometimes, machined parts have to undergo an additional operation of cleaning to get rid of grains sticking to the surface.

-Excessive nozzle wear causes additional machining cost.

-The process tends to pollute the environment.

Nontraditional machining processes

noreply@blogger.com (Prasad Ghorpade) — Fri, 06 Apr 2012 23:58:00 +0000

Nontraditional, or non-conventional, machining processes are material-removal processes that have recently emerged or are new to the user. according to their primary energy mode; that is, mechanical, electrical, thermal, or chemical......

Nontraditional processes provide manufacturing engineers with additional choices or alternatives to be applied where conventional processes are not satisfactory, such as when

• Shapes and dimensions are complex or very small
• Hardness of material is very high ( 400 HB)
• Tolerances are tight and very ﬁne surface ﬁnish is desired
• Temperature rise and residual stresses must be avoided
• Cost and production time must be reduced

Abrasive Flow Machining

Abrasive Jet Machining

Water-jet machining

Merchant’s Circle Diagram

noreply@blogger.com (Prasad Ghorpade) — Sun, 01 Apr 2012 11:45:00 +0000

In orthogonal cutting when the chip flows along the orthogonal plane, πO, the cutting force (resultant) and its components PZ and PXY remain in the orthogonal plane. Fig is schematically showing the forces acting on a piece of continuous chip coming out from the shear zone at a constant speed. That chip is apparently in a state of equilibrium.

The circle(s) drawn taking R or R1 as diameter is called Merchant’s circle which contains all the force components concerned as intercepts. The two circles with their forces are combined into one circle having all the forces contained in that as shown by the diagram called Merchant’s Circle Diagram (MCD)

The significance of the forces displayed in the Merchant’s Circle Diagram are :

PS – the shear force essentially required to produce or separate the chip from the parent body by shear

Pn – inherently exists along with PS
F – friction force at the chip tool interface
N – force acting normal to the rake surface
PZ – main force or power component acting in the direction of cutting velocity

The magnitude of PS rovides the yield shear strength of the work material the nature and degree of p under the cutting condition. The values of F and the ratio of F and N indicate interaction like friction at the chip-tool interface. The force components PX, PY, PZ are generally obtained by direct measurement. Again PZ helps in determining cutting power and specific energy requirement. The force components are also required to design the cutting tool and the machine tool.

Pro E Wildfire Tutorial Open And Closed Sweep

noreply@blogger.com (Prasad Ghorpade) — Mon, 12 Mar 2012 11:04:00 +0000

This Tutorial Deals With Open & Closed Sweep in Pro e Wildfire 5.0
Both Options are used for different types of applications, You can see the basic difference between two commands.

Engineering Project For Final Year

noreply@blogger.com (Prasad Ghorpade) — Mon, 12 Mar 2012 10:21:00 +0000

PAPER CUTTING AND REWINDING MACHINE
TIME REQ. 1-1.5 Month
Expence: Rs. 20,000/-

There was a auction of one paper mill named ‘Maharudra Paper mill Pvt. Ltd.’ And unfortunately we saw that add and as it is near to our college we go there to see how was the setup of any paper mill. That time first we saw the paper re-winding machine And wanting someone to explain working. So by some reference We got the address of Mr. G.S. Ghorpade, The chairmen of ‘SAMADHAN MACHINE TOOLS’. We discussed with him and convinced him to guide us to Modify the machine. So he says yes to not only guide us but also to give us free machining charges. It look like dream come true that we got the help of such experienced person. The conventional paper re-winding machine was 9-10 feet in length, 6 feet in width and almost 6 feet in height. It also facilitate complex mechanisms.

MODIFICATIONS DESIGNED BY US

The floor space acquired by the machine is too large thus we decided to cut the length of machine up to 6 feet and also height up to 4.5 feet and put the width as it is because it is the size of standard paper. (But as our project is a demo project we decided to take the width 3 feet.)

Then they have also used the complex mechanism for......

mounting the roll which is to be re-wounded. So we decide to use the Self aligning bearing with extended inner ring for easy mounting and un mounting. Then we see there a cutter and roll adjustment for cutting paper Which add extremely high wt. to machine and decided to give some new design which is also

discussed .

Then as they are using the motor mounting outside the structure it consumes

much more floor space and also create difficulties in operating the break. So we are

Giving the motor mounting adjustment within the structure itself. Above and other

modifications are explained in sequence with the structure fabricating process in the

report.

Actual Machine
For More Details And Drawings Contact Us HERE

Pro E Wildfire Tutorial Sweep tool

noreply@blogger.com (Prasad Ghorpade) — Sat, 10 Mar 2012 12:33:00 +0000

A sweep feature is created by sketching or selecting a trajectory and then sketching a section to follow along it. Generally sweep tool is used to sweep a single section through/ along a Single Trajectory.

Pro E Wildfire Tutorial Basic Sketcher Environment

noreply@blogger.com (Prasad Ghorpade) — Fri, 09 Mar 2012 12:27:00 +0000

This Tutorial Deals With The Basic sketcher Environment in Pro e Wildfire 5.0
All the basic sketching commands like Lines, Rectangles, Circles & its types, Curves And Chamfer Are shown by drawing them.

Thirteen Limiters Prevent Overloading

noreply@blogger.com (Prasad Ghorpade) — Mon, 30 Jan 2012 08:49:00 +0000

These 13 “safety valves” give way if machinery jams, thus preventing serious damage.

1) A shear pin is a simple and reliable torque limiter. However, after an overload, removing the sheared pin stubs and replacing them with a new pin can be time consuming. Be sure

that spare shear pins are available in a convenient location.

2) Friction clutch torque limiter. Adjustable spring tension holds the two friction surfaces together to set the overload limit. As soon as an overload is

removed, the clutch reengages. A drawback to this

design is that a slipping clutch can destroy itself if it

goes undetected.

3) Mechanical keys. A spring holds a ball in a dimple in the opposite face of this torque limiter until an overload forces it out. Once a slip begins, clutch face wear can be

rapid. Thus, this limiter is not recommended for machines

where overload is common.........

4) A cylinder cut at an angle forms a torque limiter. A spring clamps the opposing-angled cylinder faces together, and they separate from angular alignment under overload conditions. The spring tension sets the load limit.

5) A retracting key limits the torque in this clutch. The ramped sides of the key-way force the key outward against an adjustable spring. As the key moves outward, a rubber pad or another spring forces the key into a slot in the sheave. This holds the key out of engagement and prevents wear. To reset the mechanism, the key is pushed out of the

slot with a tool in the reset hole of the sheave.

6) Disengaging gears. The axial forces of a spring and driving arm are in balance in this torque limiter. An overload condition overcomes the force of the spring to slide the gears out of engagement. After the overload condition is removed, the gears must be held apart to prevent them from being stripped.With the driver off, the gears can safely be reset.

7) A cammed sleeve connects the input and output shafts of this torque limiter. A driven pin pushes the sleeve to the right against the spring.When an overload occurs, the driving pin drops into the slot to keep the shaft disengaged. The limiter is reset by turning the output shaft backwards.

8) A magnetic ﬂuid is the coupler in this torque limiter. The case is ﬁlled with a mixture of iron or nickel powder in oil. The magnetic ﬂux passed through the mixture

can be controlled to vary the viscosity of the slurry. The ability to change viscosity permits the load limit to be varied over a wide range. Slip rings carry electric current to the vanes to create the magnetic ﬁeld.

9) A ﬂuid is the coupling in this torque limiter. Internal vanes circulate the ﬂuid in the case. The viscosity and level of the ﬂuid can be varied for close control of the maximum load. The advantages of this coupling include smooth torque transmission and low heat rise during slip

10) The shearing of a pin releases tension in this coupling. A toggle-operated blade shears a soft pin so that the jaws open and release an excessive load. In an alternative design, a spring that keeps the jaws from spreading replaces the shear pin.

11) A spring plunger provides reciprocating motion in this coupling. Overload can occur only when the rod is moving to the left. The spring is compressed under an overload condition.

12) Steel shot transmits more torque in this coupling as input shaft speed is increased. Centrifugal force compresses the steel shot against the outer surfaces of the case, increasing the coupling’s resistance to slip. The addition of more steel shot also increases the coupling’s resistance to slip.

13) A piezoelectric crystal produces an electric signal that varies with pressure in this metal-forming press.When the ampliﬁed output of the piezoelectric crystal reaches a present value corresponding to the pressure limit, the electric clutch disengages. A yielding ring controls the compression of the piezoelectric crystal.

Welding

noreply@blogger.com (Prasad Ghorpade) — Mon, 26 Dec 2011 22:09:00 +0000

While Choosing Right Value From Below Tables It Must Be Kept In Mind That, Here:

t is the throat thickness = 0.707 s.
s is the size of weld
Complete Design Process Is On Page "Fillet Weld Design" & "Fillet Weld Design Special Cases"

Look For Other Design Process

1) Simple Fillet Weld Design
2) Fillet Weld Design Special cases

fillet welding

noreply@blogger.com (Prasad Ghorpade) — Mon, 26 Dec 2011 22:00:00 +0000

1) Circular fillet weld subjected to torsion:
Consider a circular rod connected to a rigid plate by a fillet weld as shown in Fig.

Let
d = Diameter of rod,
r = Radius of rod,
T = Torque acting on the rod,
s = Size (or leg) of weld,
t = Throat thickness,
**J = Polar moment of inertia of the
**For Values Of Section Modulus/ Polar Modulus Of various weld sections see the Post "Weld Design Data"

weld section =

We know that shear stress for the material,

This shear stress occurs in a horizontal plane along a leg of the fillet weld. The maximum shear occurs on the throat of weld which is inclined at 45° to the horizontal plane.

∴ Length of throat,

and maximum shear stress,

2) Circular fillet weld subjected to bending moment:

Consider a circular rod connected to a rigid plate by a fillet weld as shown in Fig.

Let
d = Diameter of rod,
M = Bending moment acting on the rod,
s = Size (or leg) of weld,
t = Throat thickness,
**Z = Section modulus of the weld section

**For Values Of Section Modulus/ Polar Modulus Of various weld sections see the Post "Weld Design Data"

We know that the bending stress,

This bending stress occurs in a horizontal plane along a leg of the fillet weld. The maximum bending stress occurs on the throat of the weld which is inclined at 45° to the horizontal plane.

∴ Length of throat,

and maximum bending stress,

3) Long fillet weld subjected to torsion:

Consider a vertical plate attached to a horizontal plate by two identical fillet welds as shown in Fig.

Let
T = Torque acting on the vertical plate,
l = Length of weld,
s = Size (or leg) of weld,
t = Throat thickness, and
**J = Polar moment of inertia of the weld section

**For Values Of Section Modulus/ Polar Modulus Of various weld sections see the Post "Weld Design Data"

J For both sides of weld,

It may be noted that the effect of the applied torque is

to rotate the vertical plate about the Z-axis through its mid

point. This rotation is resisted by shearing stresses developed between two fillet welds and the horizontal

plate. It is assumed that these horizontal shearing stresses vary from zero at the Z-axis and maximum

at the ends of the plate. This variation of shearing stress is analogous to the variation of normal stress

over the depth (l) of a beam subjected to pure bending.

∴ Shear stress,

The maximum shear stress occurs at the throat and is given by

Look For Other Design
1) "Weld Design Data"
2) Fillet Weld Design Special cases

CNC programming

noreply@blogger.com (Prasad Ghorpade) — Mon, 26 Dec 2011 11:30:00 +0000

These CNC computers don’t have to be fast, as you see. It is more likely to run one program anyway. It won’t be the type of computer that has to multitask like Windows. The CNC control computer of the CNC machining process will basically be used to read the G-Code that was written in the CAM stage of the CNC machining process. One other thing that you have to put in mind is that the CNC control computer is going to be in a rugged environment.

Expect your CNC control computer to be covered in dust because they will be near your work environment. They are usually beside the machines that spew dirt and dust when products are being manufactured. The CNC control computers for the CNC machining process will cost your around fifty to a thousand dollars depending on the computer. If you’re getting the low end, prehistoric computers then spare change in your pocket would do.

The CNC control software in the CNC machining process is the software that will read the G-Code program. You’ve got the hardware, now its time to get your hands on the software that will run your G-Code.

You Can Ask For The Download Link Of Complete CNC Manual In Engg. Ebooks Page. Find The Name Of Book In Mechanical Engineering Section There And Send Mail Request By Following The Instructions On Engg. Ebook Page.

What is Single Slider Crank Chain

noreply@blogger.com (Prasad Ghorpade) — Sun, 25 Dec 2011 11:30:00 +0000

A single slider crank chain is a modification of the basic four bar chain. It consist of one sliding pair and three turning pairs. It is,usually, found in reciprocating steam engine mechanism. This type of mechanism converts rotary motion into reciprocating motion and vice-versa. In a single slider crank chain, the links 1 and 2, links 2 and 3, and links 3 and 4 form three turning pairs while the links 4 and 1 form a sliding pair.

The link 1 corresponds to the frame of the engine, which is fixed. The link 2 corresponds to the crank; link 3 corresponds to the connecting rod and link 4 corresponds to cross-head. As the crank rotates, the cross-head reciprocates in the guides and thus the piston reciprocates in the cylinder. By fixing, in turn, different links in a kinematic chain, an inversion is obtained and we can obtain as many mechanisms as the links in a kinematic chain. It is thus obvious, that four inversions of a single slider crank chain are possible. These inversions are found in the following mechanisms.

1) Inversion Pendulum pump

In this mechanism, the inversion is obtained by fixing the cylinder or link 4 (i.e. sliding pair), as shown in Fig. In this case, when the crank (link 2) rotates, the connecting rod ....

Read Complete Article >>

2) Inversion Oscillating cylinder engine

The arrangement of oscillating cylinder engine mechanism, as shown in Fig. is used to convert reciprocating motion into rotary motion. In this mechanism, the link 3 forming the turning pair is fixed...

Read Complete Article >>

3) Inversion Rotary internal combustion engine

Sometimes back, rotary internal combustion engines were used in aviation. But now-a-days gas turbines are used in its place. It consists of seven cylinders in one plane and all revolves about fixed centre D, as shown in Fig. while the crank (link 2) is fixed....

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4) Inversion Crank and slotted lever quick return motion mechanism

This mechanism is mostly used in shaping machines, slotting machines and in rotary internal combustion engines. In this mechanism, the link AC (i.e. link 3) forming the turning pair is fixed, as shown in Fig. The link 3 corresponds to the connecting rod of a reciprocating steam engine....

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5) Inversion Whitworth quick return motion mechanism

This mechanism is mostly used in shaping and slotting machines. In this mechanism, the link CD (link 2) forming the turning pair is fixed, as shown in Fig. The link 2 corresponds to a crank in a reciprocating steam engine. The driving crank CA (link 3) rotates at a uniform angular speed....

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7 Types Of Welding Processes

noreply@blogger.com (Prasad Ghorpade) — Fri, 23 Dec 2011 20:54:00 +0000

Processes based on heat to join and sever metals. Welding and cutting are grouped together because, in many manufacturing operations, severing precedes welding and involves the same production personnel. Welding is one of the joining processes, others being Riveting, bolting, gluing, and adhesive bonding.

The American Welding Society’s deﬁnition of welding is “a metal-joining process wherein coalescence is produced by heating to suitable temperatures with or without the application of pressure, and with or without the use of ﬁller metal.” Brazing is deﬁned as “a group of welding processes wherein coalescence is produced by heating to suitable temperature and by using a ﬁller metal, having a liquids above 800◦ F and below the solidus of the base metals. The ﬁller metal is distributed between the closely ﬁtted surfaces of the joint by capillary attraction.” Soldering is similar in principle, except that the melting point of solder is below 800◦ F. The adhesion of solder depends not so much on alloying as on its keying into small irregularities in the surfaces to be joined. For comparison of metal joints.

Please Visit:

1) A resistance Spot welding

Process in which coalescence is produced by the ﬂow of electric current through maintained at all times during the heating cycle to the resistance of metals held together under pressure. A low-voltage, high-current energy source is required. Usually the upper electrode moves and applies the clamping force

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2) Gas tungsten-arc welding

Inert-gas shielding is essential with tungsten electrodes; consequently the term “gas tungsten-arc welding” (GTAW) is used. A common electrode diameter is 1/8 in. (3.2 mm) for 150 A. The process is adapted to welding thin material, 1/8 in. (3.2 mm) thick and less, and to the root, or ﬁrst pass, because the operator can control penetration more readily than with most other arc welding processes.

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3) Gas metal-arc welding

Inert-gas-shielded metal-arc welding with consumable, continuous electrodes (called GMAWfor gas metal-arc welding) requires no ﬂux and produces welds without a slag cover. The arc is in an atmosphere of argon or heliumsupplied at 5–100 ft3/h (0.14–2.8 m3/h) from the gas cup of the torch.

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4) Submerged-arc welding

This process is performed with a continuous electrode and a granular ﬂux com- posed of silicates with or without deoxidizers and alloying elements. The ﬂux is piled to a depth of 1/2 to 2 in. (12.7 to 50.8 mm) along the joint. The arc melts some of the ﬂux and is submerged in the liquid slag so produced. Although submerged-arc welding often uses current of about 40 nanometers, it can use as much as 400 nm, far above that usable in any other arc welding process.

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5) Shielded metal-arc welding

Shielded metal-arc welding. This arc welding process is by far the most widely used of the various electric-arc welding processes. Like the other electric-arc welding processes, it employs the heat of the electric arc to bring the work to be welded and a consumable electrode to a molten state.

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6) Flux-cored arc welding

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You Might Also Like Weld Joint Design Processes

Flux-cored arc welding.

noreply@blogger.com (Prasad Ghorpade) — Fri, 23 Dec 2011 20:47:00 +0000

Flux-cored arc welding is somewhat like submerged arc and shielded metal-arc welding except that the ﬂux is encased in a metal sheath instead of being laid over the wire. Although wire is automatically fed from a coil, the equipment is portable and more versatile than submerged-arc. The weld metal is shielded by the melted ﬂux and by a gaseous medium, either externally supplied or evolved from the ﬂux. The two principal variations in the process employ a gas-shielded electrode that requires additional shielding in the form of CO2 around the arc and weld puddle, or a self-shielded electrode that generates its own shielding (no external shielding gas is supplied.

The classiﬁcation system for ﬂux-cored electrodes follows the general pattern used in other ﬁller metal classiﬁcations. In a typical designation, E70T-1, the preﬁx E indicates an electrode as in other electrode classiﬁcation systems; the number 70 refers to the minimum as-welded tensile strength in 1000-lb/in. 2 (6,895-MPa) units, the letter T indicates that the electrode is of tubular construction (is a ﬂux-cored electrode), the sufﬁx 1 places the electrode in a particular grouping based on the chemical composition of deposited weld metal, method of shielding, and adaptability of the electrode for single- or multiple pass use.

How To Clamp Various Workpieces

noreply@blogger.com (Prasad Ghorpade) — Thu, 22 Dec 2011 22:02:00 +0000

The clamping points should be provided with ample radius to make the clamp operable even if there is variation in the workpiece. Heel pin pressure surface should also be made spherical to permit some tilting of the clamp

Misalignment between the clamp surface and the clamping nut due to tilting of the clamp can be countered by use of spherical washers between the clamp and the nut. As washers are used in pairs, the two washers have matching male and female spherical seats. The spherical bearing allows the washers to tilt with respect to each other. The lower female washer tilts with the clamp while the upper male washer below the nut remains square to the nut. The spherical seat transmits the clamping pressure from the nut to the clamp.

A clamp with a cylindrical washer.

In multiple clamping, a pivoted equalizer is used for clamping two unequal workpieces...

simultaneously. The equalizer clamp pivots around the pin to suit the workpieces.

The equalizer principle can be extended to facilitate clamping of many even number of workpieces simultaneously by a single clamp.

Laterally Loaded Vertical Piles

noreply@blogger.com (Prasad Ghorpade) — Tue, 20 Dec 2011 17:46:00 +0000

Vertical-pile resistance to lateral loads is a function of both the flexural stiffness of the shaft, the stiffness of the bearing soil in the upper 4 to 6D length of shaft,

where D = pile diameter and the degree of pile-head fixity.

The lateral-load versus pile-head deflection relationship is developed from charted non dimensional solutions of Reese and Matlock. The solution assumes the soil modulus K to increase linearly with depth z; that is,

where = coefficient of horizontal subgrade reaction. A characteristic pile length T is calculated from

where EI = pile stiffness. The lateral deflection y of a pile with head free to move and subject to a lateral load Pt and moment Mt applied at the ground line is given by

where Ay and By are nondimensional coefficients. Nondimensional coefficients are also available for evaluation of pile slope, moment, shear, and soil reaction

along the shaft.

For positive moment,

Positive Mt and Pt values are represented by clockwise moment and loads directed to the right on the pile head at the ground line. The coefficients applicable to evaluation of pile-head deflection and to the maximum positive moment and its approximate position on the shaft, z/T, where z = distance below the ground line, are listed in Table below. The negative moment imposed at the pile head by pile-cap or another structural restraint can be evaluated as a function of the head slope (rotation) from

=rad represents the counterclockwise (+ ) rotation of the pile head and
= coefficients (see Table).

The influence of the degrees of fixity of the pile head on y and M can be evaluated by substituting the value of - Mt from the preceding equation into the earlier y and M equations. Note that, for the fixed-head case,