SAINT-VENANT''S TORSION PROBLEM WITH STRESS FUNCTION IN THE FORM OF A THIRD DEGREE POLYNOMIAL
应力函数或扭曲函数爲三次多项式形式的扭转问题

The free torsion problem, solved by Saint-Venant with semi-inverse method, is well known in the theory of elasticity. "In this paper we discuss this problem systematically by considering a cylindrical bar whose cross section is a simply connected region under twist moment M, and assume that the stress function ψ is in the form of a third degree polynomial.