Variation in Functional Properties of Shape Memory Materials under Use of Long Duration

本文研究了形状记忆合金（SMA）和形状记忆聚合物（SMP）的功能性能、形状记忆合金（SMA）的疲劳性能和形状记忆聚合物（SMP）长时间保持在固定形状下的变形性能。所得结果可总结如下。(1)应力控制条件下SMA的子环加载过程中，加载过程中出现了恒应变下的应力松弛和恒应力下的蠕变变形。卸料压力机出现应力恢复和蠕变恢复。这些伪粘弹性行为是由温度变化引起的马氏体相变引起的。(2)研制了一种新型SMA钢丝交变平面弯曲疲劳试验机。通过对SMA丝的旋转弯曲疲劳、脉动平面弯曲疲劳和交变平面弯曲疲劳的最大应变，系统地表达了应变比对疲劳寿命的影响。新研制的超弹性薄壁…More管的疲劳寿命比钢丝短。薄管的疲劳裂纹产生于内表面。在薄管中，由于疲劳引起的断口比例很小。(3)对于新研制的高弹性细丝，在应力水平为1400 MPa、应变量为4%时，应力-应变曲线基本为直线。疲劳性能不依赖于温度和频率。弹性模量是不锈钢的四分之一。该高弹性细丝作为医用导丝具有较高的性能。(4)高温加载SMP泡沫，低温保持变形形状，保温6个月后，不依赖最大应变，形状固形率和形状恢复率均大于98%。(5)如果在高温下保持SMP泡沫的变形形状，会发生二次形状形成，导致形状恢复不完全。形状不可恢复率随保温温度、保温应变和保温时间成比例增大。少

In the present study, functional properties of shape memory alloy (SMA) and shape memory polymer (SMP), fatigue properties of SMA and deformation properties of SMP held at the fixed shape for a long duration were investigated. The results obtained can be summarized as follows.(1)In the subloop loading of SMA under the stress-controlled conditions, stress relaxation under constant strain and creep deformation under constant stress appear in the loading process. Stress recovery and creep recovery appear in the unloading press. These pseudoviscoelastic behaviors are induced due to the martensitic transformation based on variation in temperature.(2)An alternating-plane bending fatigue testing machine for an SMA wire was newly developed. The influence of strain ratio on fatigue life is systematically expressed by using maximum strain for rotating-bending, pulsating-plane bending and alternating-plane bending fatigue of an SMA wire. Fatigue life of a newly developed superelastic thin-walled … More tube is shorter than that of a wire. Fatigue crack of a thin tube initiates on an inner surface. The ratio of fracture surface due to fatigue in a thin tube is small.(3)With respect to a newly developed highelastic thin wire, the stress-strain curve is almost straight till a stress level of 1400 MPa and an amount of strain of 4%. The fatigue property does not depend on temperature and frequency. Modulus of elasticity is one fourth of that of stainless steel. The highelastic thin wire has high performance for a medical guide wire.(4)If an SMP foam is loaded at high temperature and the deformed shape is held at low temperature, both ratios of shape fixity and shape recovery are larger than 98 % without depending on maximum strain after holding for six months.(5)If the deformed shape of an SMP foam is held at high temperature, secondary shape forming occurs, resulting in imperfect shape recovery. The ratio of shape irrecoverableness increases in proportion to shape-holding temperature, shape-holding strain and shape-holding time. Less