Explanation: True stress is shown with symbol σT. It is given by expression σT = P / Ai here P is load and Ai is an instantaneous or true area of cross section.

Explanation: True strain is given by ƐT = ln (L/L0). It is smaller than the engineering strain. It can be illustrated by ƐT = ln (1 + Ɛ) expression.

Explanation: ƐT = ln (1 + Ɛ). Here ƐT is a true strain and Ɛ is engineering strain. This expression can be calculated using ƐT = ln (L/L0) expression.

Explanation: σT = σ (1 + Ɛ). Here σT is true stress, σ engineering stress and Ɛ is engineering strain. It is applicable before onset of necking.

Explanation: Plastic instability is characteristic of ductile materials. It is expressed as dP = 0. Here dP is change in load due to strain hardening.

Explanation: Plastic instability condition is given by dP = 0. It can be further simplified in dσT/dƐT = σT. Which means the slope of the true stress strain curve equals the true stress at the point.

Explanation: The true area of cross section at any load in the plastic range is smaller. While it is larger for original value. So true value is always higher.

Explanation: metal forming processes are extrusion, drawing, rolling, etc. True stress is considered to be more important than engineering stress. To correlate the theory for different forms of loading, true values are preferred.

Explanation: Instantaneous area decreases continuously with strain in the plastic range. So true stress curve continuously rises. It rises till the breaking point.

Explanation: Points on the true stress strain curve lie on the left of the conventional stress strain curve. It is up to onset of necking. This can be obtained by superimposing both the curves.

Explanation: Materials generally have very low elastic strain. It may be approximately 0.1%. On strains above it, materials deform permanently.

Explanation: True stress is affected by strain hardening. So it varies from material to material. It is because an instantaneous area is taken into account.