Pseudo-shakedown phenomenon for the mass impact loading of plating

• Mass impact loading of ductile plates which cause pseudo-shakedown for repeated loadings.
• Clarification of the phenomenon of pseudo-shakedown.
• Repeated mass impacts when the masses accumulate on a plate as in cargo loading.
• Design recommendations for plates using asymptotic values from theoretical analysis.

The pseudo-shakedown phenomenon for the repeated and identical mass impact loadings on circular and rectangular plates, is studied using a rigid-plastic method of analysis. Comparisons are made with experimental data which has been published on the response of circular and square plates subjected to repeated mass impacts. Previous studies have explored the effect of only the current impact mass and ignored the accumulation of any masses from earlier impacts on a plate. This has led to a steady growth of the transverse displacements without the achievement of pseudo-shakedown. The effect of allowing the masses to accumulate on a plate surface, as, for example, in the loading of cargo in a hold, is shown to have an important influence on the behaviour. The asymptotic values of the associated expressions reveal that a pseudo-shakedown state is achieved for this case and has an associated modest value of the maximum permanent transverse displacement. The phenomenon of pseudo-shakedown is clarified and the equations are useful design tools for an estimate of the pseudo-shakedown behaviour of plating, which is loaded repeatedly with cargo and other masses in various practical situations.