a In the measurement of strains why is it preferable to meas

(a) In the measurement of strains, why is it preferable to measure stains at 60° to each other [6 marks] [6 marks] [6 marks] Outline how principal stresses can be determined from measured strains. (c) Briefly discuss how principal stresses can be used in a multi-axial failure assessment.

Solution

(1) Answer:- For 60 degree

_x = _a

_y = 1/2 * (2_a + 2_c – _a)

_xy = 2/3 * ( _c - _b)

For above equation we use 60 degree angle for correct measurement of strain.

(2) Answer:- Principle stresses :-

    ()₁ = E/(1 – ²) * ( ₁ + ₂)

()₂ = E/(1 – ²) * ( ₂ + ₁ )

By help of above equation we can measure principle stresses.

(3) Answer:-

Multi axial stresses:- The state of stress and strain at a point in the body can be described by six stress component (_x ,_y ,_z ,_xy ,_xz ,_yz ).

Multi axial states of stress are very common and multi axial strain is difficult to avoid.