共查询到18条相似文献,搜索用时 62 毫秒
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脆性材料在双向应力下的断裂和失效研究 总被引:2,自引:0,他引:2
采用热力学方法对脆性薄片试样成功地进行了双向和单向平面拉伸试验,通过观察和记录试片中心的直通裂纹的扩展和断裂过程,测试出玻璃和陶瓷薄片的断裂韧性在双向和单向拉伸载荷时的差别.结果表明双向拉伸使裂纹阻力增强,平行于裂纹的应力对裂纹扩展有影响.该研究表明,对线弹性材料在双向载荷作用下,传统的应力强度因子准则不适用.裂纹张开的应变依赖性被证实在双向应力的断裂评价中. 相似文献
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为研究锻造过程中脆性夹杂边物周围区域的应力场对其边界裂纹形成的影响,给出了平均应力度的定义及计算解析式,以平均球应力度为判据,研究了应力场对脆性夹杂物边界裂纹的影响规律.数值模拟结果表明:脆性夹杂物边界裂纹对平均球应力度的相关度高,将其作为一个参数来表征应力场对脆性夹杂物边界裂纹形成的影响规律是可行的;随平均球应力度代数值的减小,脆性夹杂物边界裂纹的尺寸减小,当平均球应力度代数值小于-2.3时,脆性夹杂物边界无裂纹形成.在Gleeble-3180热模拟试验机上,利用专门的试件和型砧进行了1 220℃热压缩变形试验,通过扫描电镜观察了试件内部脆性夹杂物边界裂纹的形成规律,试验结果与数值模拟结果吻合. 相似文献
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基于定长裂缝试件的脆性材料尺寸效应实验方法 总被引:6,自引:0,他引:6
由于脆性或准脆性材料内各类微缺陷的影响,材料的力学性能,如名义破坏应力, 刚度以及断裂韧性等随试件的大小而改变,具有明显的尺寸效应。通常情况下,描述材料尺寸效应的Bazant尺寸效应律是建立在一系列相似试件的基础上通过实验方法确定的。 本文提出了一种新的用含固定长度裂缝试件测定断裂韧性和有效断裂过程区大小的实验方法和计算公式。与相似试件测定方法相比,实验结果吻合很好。根据本文提出的定长裂缝试件实验方法,在保证与相似试件相同脆性指数范围的前提下,可以用小试件进行测量。 相似文献
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自增强厚壁筒残余应力和温度应力下应力强度因子的计算 总被引:1,自引:1,他引:0
本文用权函数法计算了自增强残余应力和温度应力下厚壁筒的应力强度因子,导得了适用于各种材料、自增强度、裂纹深度、温度和尺寸的厚壁筒应力强度因子的计算公式,编制了计算程序,方便于工程应用。 相似文献
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在脆性材料的超精加工中,一个十分重要的现象是材料由脆性状态向可延展性状态的转变.为了成功地时脆性材料进行钻石切削加工以获得镜面表面,两种状态转变点的确定十分关键.本文阐述研究这一转变的实验技术,并讨论表面生成的机理.发现在脆性材料的钻石切削中,刀具磨损是一个严重后果.建议今后的研究应集中在这一领域. 相似文献
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Abstract: The present work concerns the assessment of residual stresses (RS) in a component for thermonuclear applications, made by casting of copper on a carbon fibre‐reinforced carbon composite and intended to be subjected to severe cycles of thermal, mechanical and neutron loads. The magnitude of RS left at the interface between the two materials in the production process, due to thermal expansion mismatch, has to be carefully assessed. In the present investigation, the likely spatial distribution of the RS has been predicted first using numerical analysis and has been validated experimentally, then, on the basis of the results of indentation tests performed at the micron scale on the metal layer. It is shown that this simple and fast methodology can return reliable results in the present context. 相似文献
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硬脆材料的旋转超声辅助加工 总被引:1,自引:0,他引:1
光学玻璃、功能晶体、工程陶瓷等硬脆材料具有高强度、耐高温、耐磨损等优良的物理和机械性能,目前已被广泛应用于航空航天、汽车、军工等领域.但由于这些材料具有较高的硬度和脆性,难以用传统的加工方法进行加工,从而在很大程度上制约了这些材料的进一步推广和应用.旋转超声辅助加工技术由于其特殊的加工性能,具有切削力小、低切削热等优点,适应于各种硬脆材料的加工,因此得到了广泛的应用和迅速的发展,在硬脆难加工材料的制造领域已经占据了重要的地位.本文回顾了旋转超声辅助加工技术的发展历程和特点,介绍了旋转超声辅助加工的机理及工艺设备的研究进展,并对旋转超声辅助加工技术和设备的发展趋势进行了展望. 相似文献
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Abstract: The evaluation of residual stresses is an important aspect in many engineering applications, such as surfaces produced by mechanical or thermal treatment processes or even thin films deposited on substrates. Currently, there are several techniques for residual stress measurement. However, its application is limited by problems associated with the precision and simplicity of measurement, as well as their applicability to a wide variety of materials and situations. Indentation tests are widely used in determining the mechanical properties of materials, so it is very important to assess their sensitivity to the presence of residual stresses. In this context, recourse to numerical simulation of indentation testing proves to be an important tool to study the effect of residual stresses in the determination of hardness and modulus as well as the actual determination of residual stresses. This paper investigates the influence of the presence of equibiaxial residual stresses in the indentation test results. It proposes a methodology for reverse analysis to determine the sign and value of the equibiaxial residual stresses present in the surface of materials, from depth‐sensing indentation results. For applying this methodology, the elastic and plastic behaviour of the material must be previously determined. 相似文献
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Xiuqing Qian Yanping Cao Jianyu Zhang Dierk Raabe Zhenhan Yao Binjun Fei 《计算机、材料和连续体(英文)》2008,7(1):33-42
In this work, an inverse approach based on depth-sensing instrumented indentation tests is proposed to determine the Young's modulus, yield strength and strain hardening exponent of the materials for which the elastoplastic part of the stress-strain curve can be described using a power function. Numerical verifications performed on typical engineering metals demonstrate the effectiveness of the new method. The sensitivity of the method to data noise and some experimental uncertainties are also discussed, which may provide useful information for the application of the method in practice. 相似文献
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目的 在不同形状的压痕条件下,对瓦楞纸箱进行抗压试验,研究纸箱的变形情况和抗压能力。方法 首先设计无压痕纸箱、一字型压痕箱、八字型压痕箱以及菱形压痕箱;其次将各种压痕形状下的纸箱,利用纸箱抗压试验机进行空箱抗压实验,记录各自的最大压溃力;最后对实验数据进行分析,明确抗压强度与压痕形状的关系。结果 不同压痕形状对瓦楞纸箱的抗压强度有不同程度的影响,其中菱形影响最大。菱形压痕通过阻碍纸箱变形趋势可提高瓦楞纸箱的抗压强度。结论 在瓦楞纸箱侧板上通过施加阻碍纸箱工字型变形的压痕(如菱形压痕),可以增加瓦楞纸箱的抗压强度,对瓦楞纸箱的生产设计具有参考意义。 相似文献