VISCOELASTIC PROPERTIES OF WET CORTICAL BONE .1. TORSIONAL AND BIAXIAL STUDIES
VISCOELASTIC PROPERTIES OF WET CORTICAL BONE .1. TORSIONAL AND BIAXIAL STUDIES
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DOI：
10.1016/0021-9290(79)90016-2
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发表时间：
1979-01-01
影响因子：
2.4
通讯作者：
STERNSTEIN, SS
中科院分区：
文献类型：
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作者：
LAKES, RS;KATZ, JL;STERNSTEIN, SS
频率在2倍之间的动态模量。在林格氏溶液中，测量了10-3和100 Hz以及1和105 s之间的松弛模量，作为温度、应变水平和叠加轴向载荷的函数。在体温下，动态损耗正切从100 Hz时的0.009增加到1 Hz时的0.013，再增加到0.1 Hz以下的0.025。剪切模量在80 a时间尺度上的总变化为15-35%，这种变化大部分发生在长时间的松弛中。牛骨虽然较硬，但表现出与人骨相似的粘弹性行为。非线性粘弹性响应表现为等时剪切模量随应变水平的增加，在应变大于10-4时较为明显，在动态试验中不如松弛试验明显。长时间的恢复比放松慢，但总是渐进地接近完成。这种效应在人骨中很小，在牛骨中可以忽略不计，但由于扭转样品上轴向应力的叠加而加剧。进行了双轴实验，因为体内的骨骼受到比单轴拉伸或剪切更复杂的应力。17.2 MN/m2的轴向拉伸应力使人骨的高频损耗切线增加0.simeq。将剪切模量改变0.simeq。1.5%;在22.1 MN/m2的轴向应力作用下，牛骨的剪切模量变化0.6%。粘弹性响应的温度依赖性被发现是热流变复杂的。显然，骨实验必须在体温下进行，以与体内情况相关。时间-温度叠加对骨骼的有效性有疑问。
The dynamic moduli for frequencies between 2 .times. 10-3 and 100 Hz and the relaxation modulus between 1 and 105 s were measured in torsion for human and bovine cortical bone kept wet in Ringer''s solution, as a function of temperature, strain level and a superposed axial load. At body temperature, the dynamic loss tangent increased from 0.009 at 100 Hz to 0.013 at 1 Hz to 0.025 below 0.1 Hz. The total change in shear modulus over 8 decades of time scale was 15-35%, most of this change occurring at long times in relaxation. Bovine bone, although stiffer, exhibited viscoelastic behavior similar to that of human bone. Nonlinear viscoelastic response, in the form of the isochronous shear modulus increasing with strain level, became apparent for strains above 10-4, and was less pronounced in dynamic tests than in relaxation. Recovery at long times occurred more slowly than relaxation, but always approached completion asymptotically. This effect, small in human bone and negligible in bovine bone, is accentuated by the superposition of an axial stress on the torsion sample. Biaxial experiments were performed, since bones in the body are subjected to stresses which are more complex than uniaxial tension or shear. An axial tensile stress of 17.2 MN/m2 increased the high frequency loss tangent of human bone by .simeq. 20% and changed the shear modulus by .simeq. 1.5%; for bovine bone, the shear modulus was changed by 0.6% by an axial stress of 22.1 MN/m2. The temperature dependence of the viscoelastic response was found to be thermorheologically complex. Apparently bone experiments must be done at body temperature to be relevant to the in vivo situation. Time-temperature superposition is of questionable validity for bone.