A plastic which behaves in accordance with a Kelvin-Voigt model is subjected to the stress history plot as shown in Figure 1, with σ1 = 20 MPa and t₁ = 200 s. Assuming that the Boltzmann Superposition Principle applies, calculate the strain in the material: (i) after 150 seconds (ii) after 250 seconds Data: spring constant (ε) = 20 GPa viscosity of the dashpot (n) = 1000 GPa.s. The Kelvin model: ɛ(t) = ½- (1 − e¯/), - where the symbols have their usual meanings. Stress, σ, (MPa) 25 0120 15 10 10 5 0 0 100 200 300 Time (s) Figure 1: Stress history plot

A 45° strain gauge rosette placed on a stainless steel structure results in the following values being determined for the maximum and minimum principal strains: €1 = 1,625.9 ×10–6 and €2 = -753.4 x10-6. Assuming plane stess, determine the factor of safety against the Tresca criterion. For stainless steel, use Young's modulus E = 196 GPa, Poisson's ratio v = 0.29 and yield stress oy = 1120 M Pa. Give your answer to 2 decimal places.

A bar BD is held in a horizontal position when there is no load by the steel wire AB. When a weight Wis added at C, also hanging from a steel wire CE, then point C is displace down by 0.025in. The cross-sectional area of the wires is 0.002in². The wires are made of a steel alloy with E = 29000ksi and σy = 70ksi. Calculate the strain in both wires, and the weight W. B A N E Parameter ft L_1 4 L_2 1 L_3 2 L_4 4 The strain in AB is € AB = The strain in CE is ECE = The weight W = 30 W cc 080 BY NO SA 2021 Cathy Zupke Xlb D in./in. in./in.

Consider the following strain state: [0.0016 0.0003 [0] = 0.0003 0.0008 0 0 0 0 0.0004] a. Determine the strain matrix for this strain state if the axes are rotated 30° counterclockwise around z-axis. b. Plot Mohr's circle for this strain state.