石膏-微米厚度刨花腕部骨伤固定夹板的制造工艺

骨伤科固定材料研究的一直是骨伤科中最基本和最活跃的领域。从最初的手制夹板到石膏绷带、热塑夹板、高分子绷带等材料的发明与应用,都在骨伤科固定性能上有了长足的进步,给骨伤科的救治带来了更加有效的手段和方法。本研究开发一种新型医用材料石膏-微米厚度刨花腕部骨伤固定夹板。石膏-微米厚度刨花腕部     

STRENGTH PROPERTIES OF ROCK MASS WITH BIDIRECTIONAL INTERMITTENT CROSS JOINTS

In this paper,the strength properties of rock mass withrows of intermittent bidirectional cross joints by simulating models arediscussed.Work has been done on finding the failure mechanism of therock mass as well as the influence of joint direction and lateral pressureon tne strength of the rock mass.At the end of the paper,model testresults ahd FEM analyses are presented and strength criteria for thiskind of rock mass are proposed.     

THE MIXED MODE FRACTURE CRITERION OF BRITTLE ROCK UNDER COMPRESSION-SHEAR STRESS STATE

In this paper the test results of mixed mode fracture of three kinds of brittle rock under two kinds of stress paths are reported. The fracture mechanism and failure patterns of brittle lock under different stress paths are discussed. Theory analysis and test results show that the Compression- Shear fracture criterion of brittle rock can be expressed:     

A STUDY ON FRACTURE MECHANICS OF BRITTLE MATERIAL WITH PER-CRACKS

In this paper the fracture process of specimen,with single crack, double cracks and triple cracks is observed and analysed. The experimental results show that the fracture process of specimen is different because of the differention of the number, the distance and the type of array of cracks. And the fracture propagation of specimen with triple cracks and double cracks is foundmentally the same.     

汽轮机叶片断裂机理分析

对汽轮机断裂叶片进行了现场调研、断口扫描电镜、能谱及金相组织分析。结果表明,在安装过程的焊接工序时,汽轮机叶片前缘与电焊条瞬时接触,导致局部组织过热、过烧。工作时,在交变离心拉应力作用下该损伤区域成为裂纹源。在交变载荷的持续作用下,裂纹从源区缓慢疲劳扩展至一定深度,而后在其前沿形成的平面应变应力状态下快速脆性扩展,直至在巨大离心拉应力作用下作极快切向扩展而导致最终的瞬时断裂。     

弹簧垫圈断裂原因分析

通过宏观检验观察、化学成分分析、硬度测试、金相检验和断口分析等方法对弹簧垫圈的断裂原因进行分析。结果表明:该弹簧垫圈热处理时产生淬火裂纹,镀锌时氢原子在裂纹尖端偏聚,这两种因素的共同作用导致弹簧垫圈在装配预紧过程中发生脆性断裂。     

Elastic_Brittle Fracture Analysis of Micro_Crackin Concrete Loaded by Stretching Stresses

The concrete is a typical brittle material.The fracture and propagating failure of the micro-crack in loaded concrete are very important problem in civil engineering.In this paper,from the equilibrium differential equations and failure criterion,the elastic-brittle static fracture analysis of the plane stress micro-crack in concrete loaded by stretching stresses was done near crack line.The relations between the stretching stresses and the length of brittle fracture zone on the crack line were obtained.     

水轮机顶盖部分螺栓断裂后剩余螺栓的强度分析

针对水轮发电机组由于顶盖连接螺栓断裂而导致水淹厂房等严重事故的问题,建立了某电站实际顶盖及螺栓的模型并进行有限元分析.基于Ansys,采用有限单元法求解静力学基本方程,计算得到各种工况下螺栓的应力分布;研究了某混流式水轮机顶盖全部螺栓正常工作时的强度,对部分螺栓断裂后剩余螺栓的强度进行了分析,对比了螺栓在断裂数量为1,2,4,8根以及断裂位置为90°对称分布、邻近分布、180°分布时的应力情况.计算结果表明:部分螺栓断裂后,由于偏载和突变,其余螺栓的最大应力值都会升高;螺栓断裂个数越多,断裂螺栓的分布位置越邻近,则其余螺栓强度越不足.当断裂螺栓数量为4根且处于邻近分布位置时,剩余螺栓的最大应力为744.03 MPa,十分接近螺栓材料的极限容许应力744 MPa;当断裂螺栓处于邻近分布位置且数量达到8根时,剩余螺栓的最大应力达776.21 MPa,增幅达19.69%,已远远超过材料极限容许应力,威胁电站安全运行.     

Experimental Study on Flexural Toughness and Fatigue Property of Polypropylene (PP) Fiber Reinforced Cement-stabilized Macadam

By four-point bending test and fatigue test,the authors studied the flexural toughness and fatigue property of semi-rigid base course of cement-stabilized macadam with and without polypropylene(PP) fiber.Some significant data about these two kinds of material have been obtained,such as the load-deflection curves,toughness index according to the standard methods of JCI and ASTM C1018-97,the fatigue lifetime under different stress levels and the fatigue lifetime regression equation.The results show that the reinforcing effect of the PP fiber is remarkable;the bending strength,ultimate deformability,JCI toughness index,ASTM C1018-97 toughness index and fatigue life of cement-stabilized macadam with PP fiber are increased by about 10%,150%,67.7%,36.1%~79.8%,and 126%~352%,respectively,when the volume fraction of PP fiber is only 0.077%.At the same time,the authors revealed the toughness improving mechanism and the anti-fatigue mechanism of the fiber in such material based on the fracture mechanics theory.