alleryStart learning →The 3D equation of equilibrium in a body (without body forces) is:
Aσ_ij = ε_ij
Bσ_ij = const
C∂σ_ij/∂x_j = 0 — divergence of stress tensor vanishes (Cauchy)
D∇·u = 0
Answer & Solution
Correct answer: C. ∂σ_ij/∂x_j = 0 — divergence of stress tensor vanishes (Cauchy)
For an infinitesimal element in static equilibrium without body forces (gravity, etc.), the sum of internal-force contributions from neighboring elements must balance: $\partial \sigma_{ij}/\partial x_j = 0$ (j summed via Einstein notation).
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