Shape memory polymers (SMPs) are a class of soft active materials that have the ability to retain one or multiple temporary shapes and exhibit deformation as a response to stimuli. The temporary shapes involved can be very complex but SMPs can recover large amounts of strains as compared to other smart materials. They have a wide range of applications in fields as diverse as healthcare, transportation, energy generation, etc. and their mechanism can be easily altered. Hence, there is an increasing need to model their behavior. This paper discusses the behavior of a thermally activated subclass of SMPs in which the temporary shape is fixed by a crystalline phase and the return to original shape is due to the transition of this crystalline phase. We simulate its thermo-mechanical behavior using a framework based on the theory of multiple natural configurations. Viscoelastic effects have been incorporated using a rate type model along with the anisotropy of the crystalline phase. The model has been applied to boundary value problems of homogeneous deformations such as uniaxial extension of dual shape and triple shape memory polymers under controlled stress and strain conditions. The model has also been applied to boundary value problems related to inhomogeneous deformations such as circular shear, inflation, and extension of a hollow cylinder. The effects of parameters such as temperature, external stress, crystallinity, shear modulus and relaxation time on the nonlinear deformation have been studied. The results are found to be consistent with the experimental data and show how the complicated thermo-mechanical behavior and shape memory effect are influenced by these parameters.

形状记忆聚合物 (SMP) 是一类柔软的活性材料，能够保持一个或多个临时形状，并表现出对刺激的反应。所涉及的临时形状可能非常复杂，但与其他智能材料相比，SMP 可以恢复大量应变。它们在医疗保健、交通运输、能源生产等领域有着广泛的应用，并且它们的机制可以很容易地改变。因此，越来越需要对他们的行为进行建模。本文讨论了 SMP 的热激活子类的行为，其中临时形状由晶相固定，而恢复原始形状是由于该晶相的转变。我们使用基于多种自然配置理论的框架来模拟其热机械行为。粘弹性效应已使用速率类型模型与结晶相的各向异性结合在一起。该模型已应用于均匀变形的边界值问题，例如在受控应力和应变条件下双形状和三重形状记忆聚合物的单轴延伸。该模型也已应用于与非均匀变形相关的边界值问题，例如圆形剪切、膨胀和空心圆柱体的延伸。研究了温度、外应力、结晶度、剪切模量和松弛时间等参数对非线性变形的影响。