Evaluation of various schemes for quasi-static boundary element analysis of polymers

Abstract

The behaviour of polymers under quasi-static load is analysed by various boundary element schemes. Linear viscoelasticity, for which the correspondence principle applies, is assumed. The problem is first solved in the Laplace transform domain with the time-dependent response determined by numerical inversion. A solution is also obtained directly in the time domain using fundamental solutions for unit step load excitation. Two alternative time-domain schemes, applied until recently only to dynamic problems, are adapted to quasi-static conditions. Both are based on a reciprocity relation involving Riemann convolutions and use fundamental solutions for a Dirac impulse excitation. The second of those schemes, however, uses only the Laplace transforms of these fundamental solutions, which are directly formed from the corresponding elasticity solutions and thus not specific to the viscoelastic model used. Rapid derivation of time-dependent fundamental solutions for general standard linear solids enhances the applicability of time domain methods. Computer codes based on the different algorithms are developed and applied to benchmark problems in order to assess their relative accuracy, versatility and efficiency. The various BEM predictions are generally consistent and reliable. The numerical instability of the last, so called, mixed method is minimised through appropriate choice of modelling parameters