The orientation-preservation conditions and approximation errors of a dual-parametric bi-quadratic finite element method for the computation of both radially symmetric and general nonsymmetric cavity solutions in nonlinear elasticity are analyzed. The analytical results allow us to establish, based on an error equidistribution principle, an optimal meshing strategy for the method in cavitation computation. Numerical results are in good agreement with the analytical results.
Introduction. Void formation on nonlinear elastic bodies under hydrostatic tension was observed and analyzed through a defect model by Gent and Lindley [8].Ball [2] established a perfect model and studied a class of bifurcation problems in nonlinear elasticity, in which voids form in an intact body so that the total stored energy of the material is minimized in a class of radially symmetric deformations. The work stimulated an intensive study on various aspects of radially symmetric cavitations (see, e.g., Sivaloganathan [19], Stuart [25], and a review paper by Horgan and Polignone [10], among many others).Müller and Spector [16] later developed a general existence theory in nonlinear elasticity that allows for cavitation, which is not necessarily radially symmetric, by adding a surface energy term. Sivaloganathan and Spector [21] deduced the existence of hole creating deformations without the need for the surface energy term under the assumption that the points (a finite number) at which the cavities can form are prescribed. Optimal locations where cavities can arise are also studied analytically [22,23] and numerically [14].Numerically computing cavities based on the perfect model of Ball is very challenging, due to the so-called Lavrentiev phenomenon [11]. Though there are numerical methods developed to overcome the Lavrentiev phenomenon in some nonlinear elasticity problems [1,3,12,17,18], they do not seem to be powerful enough for the cavitation problem. On the other hand, some numerical methods (see, e.g., [13,14,26]) have been successfully developed for cavitation computation on general domains with single or multiple prescribed defects, based on the defect model or the regularized perfect model [9,19,20]. In these models, one considers minimizing the total elastic energy of the form