Engineering Materials Flashcards
Ferrous Materials
Cast iron, plain carbon steels, free cutting steels, and alloy steels form a major group of ferrous materials widely used for machine components.
Propotional Limit
It is observed from the diagram that stress-strain relationship is linear from point O to P. OP is a straight line and after point P, the curve begins to deviate from the straight line. Hooke’s law states that stress is directly proportional to strain. Therefore, it is applicable only up to point P.
Modulus of Elasticity
The modulus of elasticity or Young’s modulus (E) is the ratio of stress to strain up to point P. It is given by the slope of line OP. Therefore,
Elastic limit
Even if the specimen is stressed beyond point P and up to point E, it will regain its initial size and shape when the load is removed. This indicates that the material is in elastic stage up to point E. Therefore, E is called elastic limit..
ultimate tensile strength
U. The stress corresponding to point U is called ultimate strength. The ultimate tensile strength is the maximum stress that can be reached in the tension test.
yeild strength
Y. The stress corresponding to yield point Y is yield strength. the maximum stress at which a marked increase in elongation occurs without increase in the load.
Bhandari, V B. Design of Machine Elements (p. 21). Mc Graw Hill India. Kindle Edition.
necking
For ductile materials, the diameter of the specimen begins to decrease rapidly beyond maximum load point U. There is a localized reduction in cross-sectional area called ‘necking’.
Cast Iron
Suitable for casting
Grey Cast Iron designation
Grey Cast Iron by symbol FG followed by the tensile strength in n/mm2