某核电机组柴油机紧固螺柱断裂原因分析

某核电机组柴油机紧固螺柱在回装过程中发生断裂。采用宏观观察、化学成分分析、金相检验、硬度测试、扫描电镜分析和能谱分析等方法对螺柱断裂原因进行了分析。结果表明:由于螺柱材料淬火温度控制不正确、淬火冷速不合适,导致螺柱中形成了淬火裂纹,在回装过程中的安装扭矩作用下,螺柱在淬火裂纹处发生一次性过载断裂。     

涡轮部件及螺柱标准件同轴度测量系统

根据涡轮部件及螺柱标准件的同轴度测量需求,研制了一套测量涡轮部件及螺柱标准件同轴度的检具,并创建了基于LabVIEW的测量软件。对涡轮部件及螺柱标准件的同轴度进行了实际测量,并进行了测量不确定度评定。研究结论表明,同轴度的测量结果达到预定的技术要求,所研制的同轴度测量系统适用于涡轮部件及螺柱标准件的同轴度测量。     

高强度螺柱断裂原因

某高强度螺柱在服役10个月后发生断裂,采用宏观观察、化学成分分析、扫描电镜分析、金相检验以及力学性能测试等方法对螺柱断裂原因进行了研究。结果表明：在较大交变载荷的作用下,断裂螺柱螺纹牙底的折叠位置萌生裂纹并扩展,最终发生疲劳断裂。     

某卡箍连接片断裂失效分析

通过宏观分析、扫描电镜及能谱分析、金相分析、化学成分分析、力学性能试验及受力分析等方法对卡箍连接片断裂失效原因进行了分析。结果表明:该卡箍连接片失效模式为高温蠕变断裂;导致其断裂的主要原因是装配条件下连接片承受的应力水平较高,在实际工作温度中存在较大的高温蠕变断裂风险;建议根据实际工况选用抗高温蠕变性能良好的材料。     

某连接舱断裂失效分析

某连接舱在颤振试验过程中在槽底拐角过渡处发生断裂,分析后认为连接舱断裂性质为脆性断裂;断裂原因是材料组织不良导致材料韧性、塑性较差.建议改进变质处理工艺改善材料组织.     

碳纤维织物复合材料螺柱-柱销连接结构研究

在综合分析各种复合材料连接结构的基础上,针对复合材料构件高承载轴向连接要求,提出了织物复合材料螺柱-柱销连接结构,并实验研究了织物复合材料的挤压强度,测试了螺柱-柱销连接结构的承载能力.试验结果表明,织物复合材料的最大挤压强度为887 MPa,高于0/90纤维层板复合材料的挤压强度;织物复合材料螺柱-柱销连接结构在薄壁复合材料构件的轴向连接方面,与传统的金属端框连接形式相比,接头质量效率高,成型工艺简便,具有较大的应用潜力.     

涡轮部件及螺柱标准件同轴度测量检具达国际先进水平

<正>近日,上海市计量测试技术研究院设计了一套涡轮部件及螺柱标准件同轴度测量检具,能够对没有顶尖孔的涡轮部件和螺柱标准件螺纹的中径位置和圆柱部分的同轴度进行测量,技术指标达到国际先进水平,已申请发明专利一项。在机动车制造业,涡轮部件及螺柱标准件是涡轮增压器与变速箱中的关键部件,对其尺寸的精度要求很高。涡轮部件螺纹的中径位置和圆柱部分的同轴度对保证涡轮增压器的密封性有很重要的作用。在变速箱装配过程中,螺柱标准件的应用十     

柴油机42CrMo钢螺柱早期断裂原因分析

某柴油机喷油器的42CrMo合金结构钢螺柱出现早期断裂,通过宏观分析、化学成分分析、硬度测试、金相检验、工艺分析、再回火试验等方法,对螺柱断裂原因进行了分析。结果表明:回火温度过低,显微组织转变不充分,造成螺柱硬度、抗拉强度过高,氢脆敏感性增大,同时螺纹表面质量差加剧了应力集中,两者共同作用导致了螺柱的氢致延迟断裂。     

某直升机连接螺栓断裂原因

某型直升机固定尾减速机钛合金内侧压板的3件35Ni4Cr2MoA钢连接螺栓在试车时发生了断裂。通过宏观观察、断口分析、金相检验、力学性能试验和氢含量测试等方法,分析了连接螺栓的断裂原因。结果表明:连接螺栓的失效模式为疲劳断裂,压板孔壁与螺栓杆部的局部挤压损伤形成了疲劳裂纹源,试车过程中裂纹不断扩展,最终导致了连接螺栓的断裂。     

某型飞机起落架的连接螺栓断裂失效分析

应用扫描电镜、光学显微镜和硬度等检测手段,对连接螺栓断裂原因进行了探讨.结果表明,由于装配在螺栓上的球形衬套的强度严重不足,造成了螺栓受力不均匀,导致螺栓大应力疲劳失效.     

汽轮机高压外缸结合面双头螺栓断裂分析

某电厂汽轮机高压外缸结合面双头20Cr1Mo1VTiB钢螺栓在安装时发生断裂,通过断口分析、化学成分分析、金相检验以及力学性能测试等方法对螺栓的断裂原因进行了分析。结果表明:该螺栓钢存在严重的显微组织缺陷,力学性能指标不符合技术条件要求,减弱了螺栓的承载能力,螺纹处的应力集中效应会加剧螺栓的缺口敏感性,导致螺栓在安装时于螺纹处发生脆性断裂。     

卡车转向横拉杆球头销断裂分析

某卡车转向横拉杆球头销装车使用后立即发生断裂,对其进行了理化检验和模拟试验。结果表明:失效球头销装车前其颈部就已存在很深的初始裂纹,这是导致其装车使用后立即发生过载断裂的直接原因;球头销颈部的初始裂纹产生在棒料冷拔阶段。     

钻杆接头断裂原因分析

通过断口分析、金相检验、化学成分分析和力学性能测试等方法对钻杆接头断裂原因进行了分析。结果表明:钻杆接头在使用过程中受到了环境中硫化氢的腐蚀,发生了硫化氢应力腐蚀开裂,随着裂纹扩展最终导致断裂。     

Brittle Fracture of a Lifting Stud During Assembly Operations

A lifting stud from a stator frame broke during assembly operations. The part was hot rolled from a 50 W grade low-carbon steel (according to the Canadian standard CSA G40.21-04), which is the equivalent of AISI 1022 grade. Complete metallurgical characterization of the material showed that the chemical and mechanical requirements of the aforementioned standard were met. Moreover, the tensile testing showed that the material had good ductility. Fractographic investigation, both at the macroscale and microscale levels, indicated that the lifting stud failed under bending overload, in a brittle mode. It was found that brittle behavior of the ductile material was caused by the sudden application of the load combined with triaxial stresses promoted by the threaded geometry.     

同轴单搭接接头破坏过程研究

在实验所得结果之基础上研究了预偏角对单搭接胶接接头破坏机制的影响,用弹塑性有限元法模型得到了不同裂纹长度时接头整体和胶层中心等效应力沿裂纹尖端的分布,并研究了外载大小、裂纹长度对应力强度因子的影响.结果表明,同轴接头和标准接头的破坏均从胶层界面开始,但同轴接头以形成较多小裂纹为主,而标准接头中裂纹沿着胶层向中部扩展,最终导致破坏;随裂纹长度的增加,接头上等效应力渐增,胶层中心峰值应力也增大,裂纹尖端的应力远高于其他部位;当裂纹扩展到临界尺寸时,接头会迅速破坏.     

Fracture path prediction of diamond segment in a marble cutting disc

This study investigates the fracture path behaviour of diamond segments that have been brazed on a marble cutting disc. The segments are braze‐joined using the oxy‐gas welding technique. The micro‐structure of the brazing zone and the disc were investigated using standard metallographic techniques and scanning electron microscope (SEM). Additionally, we used numerical modelling to study crack growth at the welding zone. Two dimensional linear elastic fracture mechanics principles were used to analyze propagation behaviour of the crack. Stress intensity factors were calculated using displacement correlation method. It was deduced from the SEM analysis of the fractured segment surface that the fracture occurred in the diamond segment due to stress concentration near the sharp corners of the diamond particles that are embedded into the matrix. The existence of such sharp artefacts within the matrix leads to the formation of cracks.     

Three-Dimensional Finite Element Analysis of Prosthetic Finger Joint Implants

The purpose of this study was to develop high resolution three-dimensional (3D) finite element (FE) models of the Swanson^® (No. 2) and NeuFlex^® (No. 10) joint implants to: simulate implant function; evaluate stress distributions and bending stiffness of these implants; and assess their comparative potential for fracture and range of motion (ROM) in flexion and extension. Geometric representations of the implants accurate to within 20 μm were achieved using digital laser imaging technology. Images were transferred to ANSYS 5.7 using appropriate interfacing software and 3D FE models of the implants were constructed. Hyperelastic material properties of the silicone elastomers were derived experimentally from uniaxial tensile tests on implant sections. Both implants experienced maximum von Mises stresses at 90° of flexion and minimum stresses at the neutral position of flexion (Swanson: 0°, NeuFlex: 30°). Within the reported functional ROM (33°–73°), the NeuFlex implant exhibited lower maximum von Mises stress and bending stiffness than the Swanson. The Swanson implant, which has a straight hinge, exhibited lower peak stresses and bending stiffness than the NeuFlex for flexion less than 20°. Areas of high von Mises stress for the Swanson implant included the stem–hinge junction and the peripheral zone of the body of the hinge, corresponding to clinical reports of fractures. In the NeuFlex implant, the maximum stress occurred on the dorsal surface of the hinge. Bending stiffness of the NeuFlex implant was modelled to be substantially less than that of the Swanson throughout the functional ROM (33°–73° of flexion). The resting position of the Swanson implant is at 0° of flexion. A moment was required to extend the NeuFlex implant from 30° to 0° of flexion. These results suggest that the NeuFlex may potentially facilitate flexion of the metacarpophalangeal (MP) joint, whereas the Swanson may promote a more extended position of the joint.     

IF钢压薄滚焊接头断裂机理

研究了ＩＦ钢压薄滚焊接头断裂的机理，结果发现，裂纹首先在熔合底部的熔核区以微孔聚合的方式形成，并向粗晶区扩展，然后裂纹在粗晶区内一沿一定的解理面扩展，最后在部分再结昌区以滑移面分离的方式断裂。     

某电传操纵系统弹簧拉杆可调叉形接头断裂原因

某飞机电传操纵系统弹簧拉杆可调叉形接头在运行过程中发生断裂,通过宏微观分析和金相检验等方法对拉杆接头的断裂原因进行了分析。结果表明:拉杆接头断裂为疲劳断裂,断裂的根本原因是其显微组织不均匀的同时出现了魏氏组织,使接头的抗疲劳性能严重降低,导致疲劳裂纹的萌生与扩展;而拉杆的受力不均匀则加速了其疲劳裂纹的扩展。     

汽车雨刮器刮杆接头断裂失效分析

某汽车雨刮器上的刮杆接头在进行12h的连续雪堵试验后发生断裂失效。为查明断裂原因,对刮杆接头进行了宏观分析、断口分析、化学成分分析、硬度测试以及金相检验。结果表明:该刮杆接头内侧R凸角的台阶处存在机械损伤缺陷,裂纹源萌生于此机械损伤缺陷处,加之R凸角台阶的应力集中效应,故在连续雪堵试验时刮杆接头发生一次性大应力断裂。