某车型底盘紧固螺柱零件断裂失效分析

汽车底盘系统联接方式的失效分析可以为车身底盘开发及其联接方式提供优化建议。用扫描电镜对断裂失效螺柱零件的形貌进行观察,形貌分析结果表明,螺柱的初始表面覆盖了氧化物,断口边缘的螺纹处存在损伤和二次裂纹;断口锈迹清洗后的形貌和能谱观察可见,在断口宏观形貌中存在贝纹线。通过扫描电镜放大形貌进一步发现,在裂纹源处存在二次裂纹和氧化物,在裂纹扩展区发现了疲劳辉纹的痕迹。综上,底盘紧固件螺纹的断裂失效原因是疲劳断裂。对螺柱的成分、金相和硬度检测进行分析可知,螺柱件的w(C)=0.385%,金相组织为回火索氏体,洛氏硬度为42HRC,符合螺柱材料使用标准要求。     

推流器耦合架螺栓断裂的原因

某推流器耦合架联接螺栓在运行过程中发生断裂;通过断口形貌观察、化学成分分析、硬度测试、显微组织分析、强度校核及有限元模拟分析了螺栓断裂的原因。结果表明:螺栓发生了疲劳断裂;在螺栓和螺母联接部位第一道螺纹根部的应力集中明显,在交变拉伸载荷作用下,该部位萌生裂纹并发生扩展,直到螺栓断裂;螺栓材料中镍和钼含量偏低、硬度偏高、组织中存在孔洞和夹杂物等缺陷、螺纹根部应力集中明显以及交变应力幅较大是导致螺栓疲劳断裂的主要因素。     

不锈钢螺柱的断裂失效现象及机制探讨

研究常用螺柱的断裂失效现象。采用扫描电子显微镜(SEM)Hitachi S-3400N对螺柱断口形貌进行观察,采用能谱仪(EDX)对第二相夹杂物进行分析;对螺柱进行受力分析,确定扭转断裂所需的应力,发现螺柱在低于其正常切应力状态下发生了扭转断裂失效;通过应力计算、形貌观察分析螺柱的断裂失效过程机制及失效机制。结果表明:存在于螺纹表面上的裂纹是导致螺柱扭转断裂的主要原因,即在长期使用过程中,螺柱表面因疲劳产生微裂纹,在剪切外力作用下,微裂纹扩展,导致螺柱在低于正常应力状态下,发生了断裂失效。断裂过程中,材料发生了剪切、拉伸、摩擦等现象。     

螺栓联接的可靠性设计

本文介绍螺栓联接的可靠性设计原理和方法,举例说明受预紧力和轴向变载荷的紧拉螺栓联接的可靠度计算,以及受横向变载荷的螺栓联接的剪切强度和挤压强度的可靠度计算。本文介绍的方法也适用于螺钉联接、双头螺柱联接和销钉联接等的可靠性设计。     

蓄能机组顶盖座环联接螺栓强度分析

螺栓联接作为水泵水轮机最重要的联接方式之一,要承受高强度的拉伸载荷与剪切载荷,为此螺栓需要进行预紧处理。在水泵水轮机运行过程中,往往会发生疲劳断裂的情况。本文结合水泵水轮机结构设计实例,分别采用《机械设计手册》、《VDI2230强度螺栓联接的系统计算》及有限元仿真对水泵水轮机顶盖座环联接螺栓进行了强度分析,并进行了横向比较,总结了三种校验方法的差异,为水泵水轮机螺栓强度校验提出了新的思路。     

某铁路用ω形弹条疲劳断裂原因

铁路用的一种ω形弹条在疲劳试验过程中当载荷循环约300万次时发生断裂,通过化学成分分析、硬度测试、显微组织和断口形貌观察等方法,分析了弹条的断裂原因。结果表明:ω形弹条在疲劳试验过程中因弹条尾部跟端支点处承受的交变载荷相对较大,容易产生较大的应力集中,且该处存在腐蚀坑缺陷,从而促进了疲劳裂纹的萌生和发展,最终导致弹条疲劳断裂失效。     

矿井高低压转换装置主控承载筒体与联接螺栓疲劳寿命计算

高低压转换装置的筒体和联接螺栓长期受到交变载荷以及管壁高压水流的影响,很容易出现疲劳,产生裂纹甚至断裂。文中对高低压转换装置在两种不同的工况条件下的筒体与联接螺栓部位进行有限元应力分析,找出应力集中最大的部位,即可能发生疲劳损伤最严重的部位,计算出此处筒体和联接螺栓的疲劳寿命并验证是否满足使用要求。这为高低压转换装置的正常检查、维修和进一步的优化改进提供理论依据。     

轴头联接螺栓断裂分析

针对球磨机运转时轴头联接螺栓常发生断裂的实际问题,根据线弹性理论,对轴头联接螺栓进行了力学分析,研究其应力分布规律,研究表明:轴头联接螺栓在循环的交变应力作用下,强度不足,引起疲劳断裂。     

双头螺柱断裂分析

风力发电机齿轮箱使用M30×280双头螺柱固定.安装过程中,常常在扭力还没有达到额定扭矩时便发生螺杆部分断裂.采用宏观断口观察、化学成分分析、扫描电镜断口观察和显微组织检验等方法,对断裂的双头螺柱进行了分析.结果表明:双头螺柱断裂的原因是由于螺柱原材料中存在横向裂纹,在安装过程中裂纹在拉应力的作用下扩展,以致发生断裂.     

超临界机组小汽轮机高调门调速油伺服阀螺栓断裂的原因

某电厂超临界机组小汽轮机高调门调速油伺服阀螺栓工作3.5a后发生断裂,采用化学成分分析、硬度检验、金相分析和断口分析等方法对断裂原因进行了分析。结果表明:螺栓的断裂性质为疲劳断裂,断口呈现多源特征;螺栓的螺纹部位存在多处机加工缺陷,疲劳裂纹在缺陷处萌生,在复杂疲劳载荷作用下扩展,当裂纹扩展到临界尺寸后出现失稳引起瞬时断裂;当一根螺栓疲劳断裂后,其他螺栓因承受的静载荷明显增大而发生瞬间过载断裂。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...