切应力对牛骨蠕变变形的影响研究

On the Influence of Shear Stress on Creep Deformation of Bovine Bone

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。

Bone especially wet bone may produce creep deformation when subjected to a constant load.In order to determine whether the shear stress influences bone creep deformation,real-time measurement of sample deflection curve was carried out by applying a concentrated load and a uniform load on thin plate bone samples,respectively.Results show that under constant load condition,deflection of bone samples increase continually with time,reflecting a typical creep character.There are two notable facts in experiment：the creep deformation caused by concentrated force is much greater than that caused by uniform load,and the creep displacement of wet bone is approximately 7times greater than that of dry bone.Analysis consider that the effect on sample＇s viscoelasticity not only due to the normal stress but also due to the shear stress.The creep displacement produced by shear stress is approximately 0.85 times of normal stress.