We consider mixed finite element methods with exact symmetric stress tensors. We derive a new quasi-optimal a priori error estimate uniformly valid with respect to the compressibility. For the a posteriori error analysis we consider the Prager-Synge hypercircle principle and introduce a new estimate uniformly valid in the incompressible limit. All estimates are validated by numerical examples.

翻译：我们考虑使用精确对称应应力计的混合有限要素方法。 我们得出一种新的准最佳的先验错误估计,对于压缩性来说是完全有效的。 对于后验错误分析来说,我们考虑的是 Prager-Synge 超循环原则,并在不可压缩极限中引入一个统一有效的新估计。所有估计都用数字示例验证。