Final answer:
The maximum and minimum stress levels are 280 MPa and -140 MPa, respectively. The stress ratio is -0.5, and the magnitude of the stress range is 420 MPa. This analysis is part of material science within mechanical engineering focused on fatigue and stress analysis.
Step-by-step explanation:
The subject matter is related to the field of material science and mechanical engineering, specifically related to the study of fatigue and stress analysis.
(a) Maximum and Minimum Stress Levels
To calculate the maximum and minimum stress levels, you add and subtract the stress amplitude from the mean stress, respectively.
Maximum stress (σ_max) = Mean stress (σ_m) + Stress amplitude (σ_a) = 70 MPa + 210 MPa = 280 MPa.
Minimum stress (σ_min) = Mean stress (σ_m) - Stress amplitude (σ_a) = 70 MPa - 210 MPa = -140 MPa (tensile to compressive).
(b) Stress Ratio
The stress ratio (R) is the ratio of the minimum stress to the maximum stress. R = σ_min / σ_max = -140 MPa / 280 MPa = -0.5.
(c) Magnitude of the Stress Range
The stress range (Δσ) is the difference between the maximum and minimum stresses. Δσ = σ_max - σ_min = 280 MPa - (-140 MPa) = 420 MPa.