Some simple questions regarding engineering like whats yielding, strength to weight ratio and plastic deformat

Question

Some simple questions regarding engineering like whats yielding, strength to weight ratio and plastic deformation?
What is point load and distributed load?

Answer 1

Yielding:
The phenomenon executed by most of the solids after the stress crosses a certain value called Yield Stress. During yielding the solid undergo large deformations for small increase in stress. Ductile materials execute a substantial yielding before breakage.

Strength to weight ratio:
Suppose the failure strength (say, tensile) of a material is equal to 'S' and its weight is 'W'. Then strength to weight ratio is S/W. Higher value of S/W means the material is strong and also light.

Plastic deformation:
Same as yielding. However, it starts (with reference to Tensile Test) before Yield Point, just after Elastic Limit is crossed. A body which undergoes plastic deformation acquires a permanent set. This means even after unloading the body will not have zero strain but a certain residual strain.

Point load and distributed load:
It is impossible to apply (also called concentrated load) to a body in reality. When you press the paper with a needle then you may think that you are applying a point load. But even the needle point has a finite area however small it may be.

Now, come to the concerned topic. A force which THEORETICALLY (IDEALY) acts at a point is called a point load and the force which acts over a certain length of area / volume (THEORETICALLY line) is called distributed load.

Hope, I have made it clear!