what is stress defects?

Question

Please give me the details of stress defects to the metal workpiece in milling operation and ways to prevent it. Thanks.

Answer 1

In a milling machine stress can develop due to following factors:

1. High RPM of the cutter.
2. High feed rate.
3. Shaky table.
4. Shaky workpiece, clamping force not correct.
5. Cutter having blunt or built up edges.

The above will develop hairline cracks if the material is too hard or will leave chatter marks.

Refer milling machine manual for correct feed and rpm to reduce the stresses onto the workpiece.

Answer 2

when metal workpiece is under use some defects are caused due to following reasons:
1.tensile force acting on metal when increases its elastic limit
permanent deformation in metal takes place.
2.due to excessive heating shape of workpiece changes.
3.when metal workpiece is open to air corrosion may take place.
preventive measures:
1.use such metallurgical combi. which has high elastic limit.
2.use metallurgical combi. having highest melting point.
3.use anticorrodive materials.
problems:anticorrodive metals are very costly such as gold,platinum.