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骨尤其是湿骨,在恒定载荷作用下会发生蠕变变形。为了确定切应力是否影响骨的蠕变变形,采用对骨薄板试样分别施加集中载荷和均布载荷的方式,测量试样挠度实时的变化曲线。结果显示,在载荷恒定时,骨试样的挠度随时间不断增加,体现了典型的蠕变特性。集中荷载下骨的蠕变变形远大于均布荷载下骨的蠕变变形,湿骨的蠕变位移比干骨高近7倍。分析认为,对试样粘弹性性质的影响不仅有正应力的作用,也有切应力的作用;切应力产生的蠕变变形约为正应力所产生蠕变变形的0.85倍。
Bones, especially wet bones, undergo creep deformation under constant load. In order to determine whether the shear stress affects the creep deformation of the bone, a real-time curve of the deflection of the sample is measured by applying concentrated loads and uniform loads respectively on the thin-plate specimens. The results show that at constant load, the deflection of the bone sample increases with time, reflecting the typical creep characteristics. The creep deformation of bone under concentrated load is much larger than the creep deformation of bone under uniform load. The creep displacement of wet bone is nearly 7 times higher than that of dry bone. The analysis shows that the influence on the viscoelastic properties of the sample is not only the function of normal stress but also the effect of shear stress. The creep deformation caused by shear stress is about 0.85 times of the creep deformation caused by normal stress.