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《机械强度》2015,(5):904-909
提出了采用螺栓填充孔形式研究复合材料层合板连接接头孔边层间应力分布规律,并建立了含零厚度界面胶层的三维有限元模型对受面内拉伸载荷的层合板孔边层间应力进行求解。结果表明:层间正应力沿孔分布主要受螺栓夹持力影响,相同夹持力下,不同界面层的层间正应力集中在同一范围内波动;层间剪切应力既受到螺栓夹持力影响又与界面层的类型有关系,如[-45/90]和[0/-45]界面层层间剪切应力整体取值大于其他界面层;螺栓夹持力引起的层间正应力主要为压应力,对层间强度有益,但同时产生的层间剪切应力不利于层间强度的提高,因此存在合适的螺栓夹持力使复合材料接头具有良好的孔边层间强度。 相似文献
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针对CFRP沉头螺栓连接孔制孔几何误差对连接结构拉伸强度的影响规律开展了相关研究。为了更为准确预测连接结构的应力变化情况,首先基于准静态试验建立了TC4ELI钛合金的本构模型,并基于Hashin失效准则以及界面的双线性本构建立了复合材料模型,在此基础上形成了复合材料沉头螺栓连接结构的有限元模型,并针对3个主要的制孔误差对连接结构力学性能的影响进行了数值模拟以及实验验证。研究结果表明所建立的有限元模型能够较为准确地预测连接结构失效形式以及拉伸强度。其次,相较于沉头角度以及倒角半径误差,沉头深度几何误差对最终连接结构最大应力值的影响最为显著,同时锪窝孔尺寸上下偏差对连接结构拉伸性能的影响具有较为明显的差异性。 相似文献
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螺栓连接是飞机复合材料零件连接的主要方式,已有研究主要考虑复合材料细观结构、失效准则、接触属性和螺栓螺纹细节等方面,对于复合材料制孔中制孔垂直度偏差缺乏相应的研究。本文依据ASTM标准建立有限元仿真模型,研究制孔垂直度对连接强度的影响规律,并通过单向拉伸实验进行了对比验证。结果表明,复合材料制孔垂直度偏差会对螺栓连接强度产生影响。 相似文献
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为了研究复合材料层压板结构破坏机理及失效模式,本文开展了充填孔压缩试验,包括6个铺层顺序,2个试验环境.通过试验获得材料AC531/CCF8003种铺层比率、2种铺层厚度、2种试验环境和高温湿态多批次的充填孔压缩性能.试验结果表明,相比室温干态,高温湿态(70℃±3℃)的充填孔压缩强度值有明显降低.铺层比率(50/40/10)的试验件强度值升高约10%;厚的试验件相比薄试验件的强度高约15%~20%. 相似文献
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爆炸分离技术已发展成为航空发动机包容试验中复合材料叶片飞断控制的关键技术,为探究不同埋药槽深对碳纤维增强复合材料层合板爆炸分离损伤模式的影响,采用数值模拟和试验研究相结合的方法,研究层合板在爆炸作用下的损伤过程、加速度响应与动能变化趋势,分析了层合板爆炸分离的破坏模式和机理。结果表明:针对25 mm厚层合板,当两侧开槽深度为3 mm时,部分冲击波沿厚度方向形成压缩和拉伸波使纤维出现断裂损伤,部分反射拉伸波沿层间传播使层合板出现分层损伤,层合板未被切断;当两侧开槽深度增大到3.5 mm时,冲击波主要沿厚度方向形成压缩和拉伸波使纤维出现大面积断裂损伤,层合板被完整切断;爆炸产生的能量可以限制在局部范围内,传递给层合板的额外动能较小。该研究成果可为复合材料叶片的爆炸飞脱研究提供先验知识。 相似文献
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含孔复合材料层合板在压缩载荷下的三维逐渐损伤 总被引:7,自引:1,他引:6
通过逐渐损伤分析可以清楚地了解承载复合材料层合板内部损伤的产生及扩展过程,应用三维逐渐累积损伤理论和有限元分析技术,对不同材料不同宽孔比的含孔复合材料层合板在压缩载荷作用下的逐渐破坏过程进行分析,综合考虑了基体开裂、基纤剪切、分层及纤维断裂等四种复合材料层合板的主要破坏模式。在通用有限元分析软件ANSYS基础上进行二次开发,编制了参数化的分析模拟程序,该程序可以预测任意铺层角度和铺层厚度层合板在压缩载荷作用下的逐渐损伤破坏过程及最终失效载荷,通过与已有参考文献结果进行比较,验证了方法及程序的正确性。该程序可以较大程度地提高最终失效载荷的预测精度,为复合材料层合板结构的设计和使用提供了有力的技术支持。 相似文献
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针对电梯层门应用复合材料的强度特性问题,对层门门扇及筋板进行了复合材料反对称正交铺层设计,利用复合材料有限元法与Tsai-Wu强度失效准则,对其结构强度特性进行了研究。在层门型式试验验证有限元模型有效的基础上,分别选取单轴玻璃纤维环氧树脂(E-G)和碳纤维环氧树脂(E-C)材料,详细对比了不同层门门扇厚度、筋板个数对层门强度特性的影响。研究表明:在反正对称正交铺层设计下,E-G与E-C复合材料层门均可满足电梯层门设计要求,E-G与E-C复合材料横向压缩强度幅值数倍于横向拉伸强度,门扇内侧区域面内受最大拉伸应力,而外侧区域受最大压缩应力,其层门强度特性主要由横向应力分布主导;提高复合材料性能、门扇厚度和筋板个数目均可有效改善层门整体强度特性。 相似文献
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Fretting causes considerable reduction in the fatigue strength of a shrink-fit assembly and failures through fretting are as numerous as failures from normal fatigue. The purpose of this investigation was to determine the effect of contact pressure and slip amplitude on the fatigue limit, and a favourable value for overhang of hub and fillet radius with constant diameter ratio, at which fretting failure can be avoided and the maximum normal fatigue strength will be obtained. The torsional fatigue strength of shrink-fitted shaft couplings was estimated by tests performed by varying the overhang of the hub, the fillet radius of the shaft and the contact pressure of the shrink-fitted assembly. Press-fitting of the hub overhanging the shoulder was used to increase the contact pressure. The tests were performed using a grooved hub. These experiments showed that fretting was reduced with an increase in contact pressure, because the slip amplitude decreased. The shaft was fractured just inside the end of the fit by fretting fatigue with low contact pressure, but if the contact pressure was very high, the shaft fractured at the fillet by normal fatigue. The fretting fatigue limit at a constant diameter ratio increases with an increase in the fillet radius, and reaches its maximum value at a certain radius using the grooved hub. 相似文献
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Dong-Geon Kim In-Gul Kim Eun-Su Go Jong-Heon Kim 《Journal of Mechanical Science and Technology》2017,31(9):4093-4098
The wing structure of an aircraft also served as a fuel tank containing fluid. The fuel tank and joint structure are made up of composite structures. Hydrodynamic ram (HRAM) effect occurs when the explosion or high speed object passes through the aircraft wing and high pressure is generated in the fuel tank. High pressure can cause failure in the fuel tank and on joint structure as well as other aircraft wing structures. To ensure the aircraft survivability design, we shall examine the behavior of the joint structures in HRAM effect. In this study, static tensile tests were conducted on four kinds of composite T-joints. The failure behavior of the composite T-joints was examined using strain gauges and high speed camera. The failure stresses and failure pressure of the composite T-joints were calculated by FEA. We also examined the validity of the Finite element modeling by comparing the results of FEA and static tensile tests. 相似文献
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在某机载雷达的可靠性鉴定试验中,连接雷达与可靠性试验工装的螺栓发生了断裂.文中通过螺栓断口形貌观察、螺栓化学成分检验及螺栓金相组织检验等,对断裂螺栓进行了全面的分析,并通过有限元仿真模拟了该雷达在可靠性试验工况下断裂螺栓的应力分布.结果表明,断裂螺栓的化学成分及金相结构符合标准要求.螺栓断裂的主要原因是安装螺栓时施加的... 相似文献
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管轴压成形失稳起皱力学过程的研究 总被引:2,自引:0,他引:2
管轴压成形的先进性、优势及成形过程的成功实施受到变形区开裂和传力区起皱等失稳因素的制约,为此采用理论解析与试验相结合的方法,对失稳起皱的力学过程、影响因素及影响规律进行了研究,并给出了失稳判据,以实现稳定成形时变形参数的取值范围的确定。研究表明:成形过程的失稳起皱受到几何参数、材料参数及摩擦边界条件的共同作用。其中,模具圆角曲率半径是决定性因素,并且存在一个最大和最小圆角半径区域使成形过程顺利进行而不发生失稳起皱;增大管坯材料硬化指数,减小相对厚度及接触面的摩擦,有利于减少失稳的发生。对牌号为5052,原始管平均直径d_0=31.0mm,41.0mm铝管的应用表明所提出的判据是可靠实用的。 相似文献
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极限载荷和孔周应力是导致螺栓连接复合板失效的主要因素。基于Hashin失效准则和有限元模型建立螺栓连接复合板的渐进损伤有限元模型,通过位移载荷响应讨论预紧力、界面摩擦因数和孔隙变化对极限载荷的影响,分析不同铺层角下孔周应力分布规律。结果表明:随预紧力增大,螺栓连接复合板极限载荷先增大后减小,随摩擦因数增大,螺栓连接复合板极限载荷逐渐增大;不同孔隙下准线性阶段位移载荷响应基本一致,孔隙对极限载荷的影响主要体现在滑移阶段及剪切变形阶段;孔隙增大会减小螺栓与螺孔间的有效接触面积,影响螺栓连接的压力分布和强度;纤维铺层方向与应力分量同向时可有效减少外载荷导致的该方向应力分量的变化,且主应力分量皆在承压区域达到其最小值;应力分量方向与纤维铺层方向相同且该方向无外载荷作用时,应力分量随着角度从承压区到非承压区递增变化。 相似文献
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N. Tsushima 《摩擦学汇刊》2013,56(4):567-575
Crack propagations or failure modes in rolling element bearings, which had been difficult to explain via conventional crack propagation mechanisms such as the orthogonal shear stress mechanism, were discussed from the viewpoint of a tensile strain mechanism. Contact stresses are compressive in three axes, whose values differ from each other; then strain can be tensile in one of these directions, acting at a right angle to the direction of maximum compressive stress. A crack is considered to propagate by this tensile strain. When contact stress is small, a crack produced by some cause can propagate by this elastic tensile strain. When contact stress is large, residual tensile strain is produced by plastic deformation, which can also influence the crack propagation. Several failure modes of rolling element bearings, which had been difficult to explain, were explained by tensile strain. 相似文献
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利用ANSYS有限元分析软件,对法兰结构进行三维有限元计算,并采用对比试验验证了数值模拟的可靠性。数值计算给出了容器筒体发生塑性变形时法兰连接结构的详细的应力情况,得到以下结论:法兰张角是法兰系统整体强度和刚度的直观反映,可作为表示法兰失效的量化参数;法兰连接结构的最大应力出现在螺栓内侧及螺栓孔外侧靠筒体处;法兰环厚度是引起法兰结构受力变化最敏感的法兰尺寸,锥颈的宽度和法兰外径相对于法兰环厚度的变化对法兰强度的影响要小得多;螺栓孔中螺栓的位置和螺栓预紧力对孔周围的受力情况影响很大。这些结论为后续爆炸容器法兰结构设计及开展相关试验提供了可靠依据。 相似文献
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三维编织C/SiC复合材料拉伸损伤演化 总被引:1,自引:0,他引:1
利用声发射技术,对三维编织C/SiC复合材料在拉伸过程中损伤发展、演化进行了实验研究。实验采集了三维编织C/SiC复合材料拉伸过程的声发射信号。运用多参数分析法,分析了三维编织C/SiC复合材料拉伸损伤的声发射特性,宏观上揭示了材料拉伸损伤的发展、演化过程和规律。研究结果表明三维编织C/SiC复合材料拉伸损伤演化可被分为两个主要阶段,损伤初始阶段和损伤严重阶段。 相似文献
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Jing Yu Hongchao Zhang Dewei Deng Qianqian Liu Shengzhi Hao 《The International Journal of Advanced Manufacturing Technology》2016,87(5-8):1465-1474
Specimens of UNS S 31600 stainless steel with precast crack were treated under different discharge parameters. An elliptic hole formed ahead of the crack tip and the thermal compressive stress caused during electropulsing treatment cause the crack arresting. The factors affecting the curvature radius of the crack tip were studied. The crack arrest effect was examined by tensile test and fatigue test. Scanning electron microscopy (SEM), electro backscatter diffraction (EBSD), and transmission electron microscope (TEM) were employed to examine the changes of specimen before and after the treatment. The local recrystallization occurred around the crack tip. The experimental results indicate that the curvature radius of the crack tip is proportional to discharge parameter and crack length. The relationship between discharge parameter and the effectiveness of crack arrest can be obtained. 相似文献