Morera's stress functions

Morera's stress functions [mȯ′rer·əz ′stres ‚fəŋk·shənz]

(mechanics)

Three functions of position, ψ₁, ψ₂, and ψ₃, in terms of which the elements of the stress tensor σ of a body may be expressed, if the body is in equilibrium and is not subjected to body forces; the elements of the stress tensor are given by σ₁₁= -2∂²ψ₁/∂x₂∂x₃, σ₂₃= ∂²ψ₂/∂x₁∂x₂+ ∂²ψ₃/∂x₁∂x₃, and cyclic permutations of these equations.