Our experiments show for both uniaxial extension and compression that the post-yield stress relaxation can be slower than the pre-yield stress relaxation on all time scales. Such phenomena reveal that high stresses may result from chain tension due to large deformation of the chain networking in glassy polymers. In combination with molecular dynamics (MD) simulation, we demonstrate that even in the case of compression the stress buildup stems from the mechanical resistance against the lateral expansion of the chain network, which produces bond distortion such as bond stretching. As further evidence of how chain network dictates the mechanical responses, it is shown that significant network deformation produced by large deformation can suppress segmental relaxation in compression. Thus, the present study has made a first combination of experiment and MD simulation to elucidate (a) the remarkable effects that the chain network has in response to large post-yield deformation and (b) the direct (indirect) chain-network contributions to the macroscopic stress in extension (compression).

我们的实验表明，对于单轴延伸和压缩，在所有时间尺度上，屈服后应力松弛都可能比屈服前应力松弛慢。这种现象表明，由于玻璃状聚合物中链网的大变形，链张力可能导致高应力。结合分子动力学（MD）模拟，我们证明即使在压缩的情况下，应力累积仍来自对链状网络横向膨胀的机械阻力，而机械阻力会产生诸如键拉伸之类的键变形。作为链网络如何决定机械响应的进一步证据，研究表明，由大变形产生的显着网络变形可以抑制压缩过程中的分段松弛。从而，