On Huang Zhuping's theorem for a lower displacement bound (Q1087385)

To use the MN theorem [\textit{W. J. Morales} and \textit{G. E. Nevill}, jun., AIAA J. 8, 2043-2046 (1970; Zbl 0215.576)], one must introduce an artificial time independent velocity field which satisfies simple conditions; in particular it must not change sign. Of several candidate fields, the one with smallest plastic dissipation rate would be chosen as preferable. When the artificial field is chosen with these considerations in mind, the conjecture it rests on will almost certainly be correct and it will give a valid lower bound with very little effort. Huang Zhuping's theorem [\textit{Huang Zhuping}, Mech., Res. commun. 12, 257-264 (1985; Zbl 0586.73154)] requires determining the velocity field corresponding to the upper bound on the response time. This may require much more effort, but there is then no uncertainty about the bound.