中文摘要：

通过数值模拟,结合前人实验结果,探索低温保存血管壁出现裂纹或断裂的机理;为血管低温保存的优化设计提供理论依据.使用有限差分方法求解焓法模型,自行编制程序,求解该非线性热-力耦合问题.得到了一般低温保存过程（降温-恒温-复温-恒温）中血管壁内部瞬态温度场与应力场;研究了降温速率、复温速率、降温终止温度等因素对该应力场变化历史的影响.结合前人实验结果,指出降温阶段血管最大轴向压应力的出现并非是导致血管内外壁出现裂纹的决定因素;复温初始阶段拉应力的出现才是导致血管内外壁出现裂纹的真正因素;分步复温实质上并非是缓解或者减少热应力,而是复温至某个温度区间,在血管弹性恢复至一定程度后,使其得以安全承受原本在脆性温区内不能承受的拉应力.

英文摘要：

The mechanism of the initialization of the cracks in the artery wall during cryopreservation was explored by using numerical simulation. A model based on the enthalpy theory was solved by using the finite difference method , and a simulation program was used to predict the transient thermal field and thermal stress field across the artery wall. The effects of cooling rates, warming rates, holding temperatures on these two fields were analyzed. Coupled with the experimental results of other researchers, the authors, theoretical predictions indicated that the appearance of the axial compressive stress during the initial period of the cooling process was not the governing factor that may cause the circumferential crack in the inner and outer vascular wall; instead, it was the axial tensile stress during the initial period of the warming process that may cause the cracks. Furthermore, the stress history in the multi-step warming methods was studied. Contrary to the common opinion, the results revealed that the multi-step method could not decrease the maximal stress while it could shift the temperature range containing the maximal stress from low temperature stage to a relatively high temperature stage. As the flexibility of the blood vessel was partially recovered in the relative high temperature stage, it could bear the maximal stress, while this could not be done if still left in the low temperature stage. The intrinsic feature of the multi-step warming method was revealed by this study.