Resistance spot welding of two steel sheets is carried out in lap joint configuration by using a welding current of $$3$$ $$KA$$ and a weld time of $$0.2s.$$ A molten weld nugget of volume $$20m{m^3}$$ is obtained. The effective contact resistance is $$200\mu \Omega .$$ The material properties of steel are given as (i) latent heat of melting $$1400$$ $$kJ/kg,$$ (ii) density $$8000$$ $$kg/{m^3},$$ (iii) melting temp $${1520^ \circ }C$$, (iv) specific heat $$0.5$$ $$kJ/kgC.$$ The ambient temp is $$20C.$$

Heat (Joules) dissipated to the base metal will be (neglecting all other heat losses)

Diamond cutting tools are not recommended for machining of ferrous metals due to

In an orthogonal machining operation , the tool life obtained is $$10min$$ at a cutting speed of $$10m/min,$$ while at $$75m/min$$ cutting speed, the tool life is $$30min$$. The value of index (n) in the Taylor's tool life equation is

An orthogonal operation is carried out at $$20m/min$$ cutting speed, using a cutting tool of rake angle $$15deg$$. The chip thickness is $$0.4mm$$ and uncut chip thickness is $$0.2mm.$$

The shear angle (in degrees) is