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Viskoelastic Behaviour

For a component subjected to a uniaxial force, the enginnering stress in the material is the applied force divided by the original cross-sectional area. The engineering strain changes with depending on the elasticity.

Polymeric material in axhibit mechanical properties which come some where between these two ideal cases and hence they termed viscoelastic . In a viscoelastic material th stress is a fuction of strain and time .

(Plastic Engineering , R. J. Crawford ,Second editon , pg 42)

Spark Erosion

A gap between two electrodes energized with electirc current causes sparking which erodes both the electrodes. Control of the gap and passing current facilitates control of the rate of spark erosion. One of the electrodes is subsitude with the workpiece tobe eroded. The other electorde serves as an erodnig , Electrical Discharge Machining , tool.

The metal is removed by the thermal effect of the current. The workpiece and the electrode , the discharge interface is submerged in dielectic liquid like paraffin or transformer oil.

(Machine tools handbook ; P H Joshi , pg. 84 2007)

Spin Forming

In this sheet metal forming process , a sheet metal disk is rotated in a special type of lathe tool , while a special forming tool is pressed against the rotating disk of metal in a rotary swaging operation , thus forming or spin drawing the part to the required shape against ist forming pattern. The process is limited to metal sections which are of a symemetrical , rotated section , such as bell shapes , cones parabolic sections and cylinders

(Electromechanical design handbook ; Ronald A. Walsh ,pg .12 3rd edition)

Laser Beam Welding

The laer is concentrated of coherent monochromatic radiation. The normal White light consists of a number of colours and a number of waves . As a result , it is not possible to collimate ordinary light without losing its intensity. Thus the laser beam is a high energy source of heat to melt the joint for fusion weldign in laser beam welding.

In solid state lasers , the light is emitted form a glass or a single crysrtal that is doped with transition element.

Laser beam welding can be used obtaining deeper penetration welds with dissimilar metals.

(Manufacturing technology: foundry, forming and welding ; P.N. Rao pg.434 Second Editon)