缓冲蓄压器端盖开裂失效分析

通过宏观检验、化学成分分析、金相检验、断口分析以及能谱分析等方法,并结合零件实际情况综合分析的方法,对某型飞机缓冲蓄压器端盖开裂失效的原因进行了分析。结果表明:该端盖开裂属性为应力腐蚀开裂,而锻件表面微裂纹和氯元素沉积引起的腐蚀是造成端盖应力腐蚀开裂的主要原因。     

某高速动车组牵引电机非传动端盖开裂原因分析

某高速动车组在行驶12×105 km后进行检修时发现组内多件牵引电机非传动端盖在与传感器壳体的配合面处出现裂纹,通过宏观观察、X射线检测、残余应力测试、断口宏微观分析、能谱分析、金相检验、化学成分分析、拉伸试验等方法,对端盖开裂原因进行了分析。结果表明:端盖裂纹为固溶热处理工序时发生过烧,在后期加工应力的作用下引起的沿晶开裂。最后提出了相应的工艺改进建议。     

某余热锅炉集箱端盖断裂脱落原因分析

对某余热锅炉省煤器集箱端盖在运行24个月后发生整体断裂脱落事故进行了分析,通过对失效端盖进行宏观分析、化学成分分析、硬度测试、金相检验、扫描电镜以及能谱分析,找出了端盖断裂失效原因。结果表明:端盖失效性质为腐蚀疲劳断裂;端盖内的运行介质中含有具有腐蚀性的氯离子,在较高温度和应力作用下促使端盖内壁产生裂纹,并在集箱内温度波动造成的热疲劳应力作用下快速扩展最终导致端盖断裂脱落。     

阶梯形零件拉深工艺及模具设计

通过对端盖加工工艺进行分析,介绍了端盖拉深模具结构及工作过程,并进行了工艺计算,提出了拉深凹模和凸模的设计方法,保证了端盖拉深成形的顺利进行.     

新疆天龙公司自备电厂1号机振动测试分析

新疆天龙公司自备电厂1号发电机自2002年4月投运以来,机组运行稳定,只是发电机励端端盖振动较大.东方电机股份有限公司于××年7月5日至7月27日对发电机进行了全面的振动测试分析,查明了振动原因,并根据现场实际情况进行了处理,其后励端端盖振动有明显好转.     

某高压换热器热电偶管嘴开裂原因分析

对某柴油加氢装置高压换热器热电偶管嘴开裂原因进行了系统的测试与分析,包括宏观分析、成分检测、金相组织分析、断口及EDX分析等,对开裂原因进行了讨论,并针对失效原因提出了相应的建议措施。     

316L不锈钢波纹管膨胀节开裂原因分析与预防

某厂的316L不锈钢波纹管膨胀节在使用近3a(年)发生了穿透性开裂。采用化学成分分析、宏观及微观检验等方法对该波纹管膨胀节开裂的原因进行了分析。结果表明:氯化物应力腐蚀开裂是该波纹管开裂的主要原因,并提出了相应的预防措施。     

滑油散热器进油管嘴裂纹分析

某直升机用主减速器滑油散热器装机使用一段时间后,在进油管嘴与散热器焊接处出现渗油,检查发现该处存在裂纹。通过断口宏、微观形貌观察以及焊缝截面金相检验,确定了进油管嘴的开裂性质和开裂原因。结果表明:主减速器滑油散热器进油管嘴的裂纹性质为高周疲劳裂纹,管嘴开裂与其结构设计不合理有关;通过减小管嘴长度和增加端盖厚度,可以有效地避免进油管嘴的开裂失效。     

矿山支护用热轧36U型钢开裂分析

通过分析化学成分、显微组织和夹杂物对矿山支护用热轧36U型钢开裂的原因进行了分析。结果表明:非金属夹杂物是导致36U型钢开裂的主要原因,基体中带状组织严重,并存在异常贝氏体组织均能引起钢材开裂。并提出了预防措施。     

圆刀片淬火裂纹分析及防止措施

通过金相组织检测等方法对刀片淬火开裂原因进行分析,并根据分析结果提出了改进措施,防止续开裂的发生。     

应用于铯喷泉钟的磁屏蔽系统的设计

高质量磁屏蔽系统是铯喷泉钟的重要部件之一。首先给出评定磁屏蔽效果的3个指标,即磁场均匀区长度、磁场均匀区起点位置和磁屏蔽效率。在此基础上,讨论了利用有限元计算3层磁屏蔽系统的层间径向间距、轴向间距、端盖孔套管长度和端盖连接方式对磁屏蔽的影响,给出了相应的优化参数,并对比了按优化参数设计的3层磁屏蔽与原有4层磁屏蔽系统用有限元计算的磁屏蔽效果。有限元计算结果为中国计量科学研究院新铯喷泉钟磁屏蔽系统的技术设计提供了理论指导。     

Fatigue failure of weld joint of afterburner fuel manifold of a jet engine

A fighter aircraft met with an incident during a routine flight operation wherein pilot noticed a thin trail of smoke coming out from the tail end of the aircraft. Post landing inspection revealed that there was fire in the afterburner section of the aircraft. On investigation, it was discovered that there was a fatigue crack in one of the weld joint of the afterburner fuel manifold which resulted in fuel leakage in the form of streaks. The localized over temperature thus generated was responsible for melting of diffuser casing, adjustable nozzle casing, heat shield and hydraulic pipelines. Through detailed investigation, the sequence of failure in the engine was established. The contributing factors for fatigue cracking of the weld of the fuel manifold were identified and remedial measures suggested for prevention of similar failures.     

Split Ends and Cracking Problem During Hot Rolling of Continuously Cast Steel Billets

The paper presents a detailed analysis of split end and cracking problems that occurred during hot rolling of thermomechanically treated (TMT) grade steel bars. The major analytical tool was a multiscan computer-controlled ultrasonic image analysis system for analysis of the defects observed on transverse cut slices of the billets under investigation. The possible reasons for billet cracking during hot rolling such as a low Mn/S ratio, high casting speed, high degree of superheat, and high inclusion content in steel were analyzed. Additionally in the process parameters such as low roll diameter, high friction, and low reduction ratio were also analyzed. The cracking appeared to be associated with large surface/internal defects, axial porosity, off-centered cavities/porosities, off-centered cracks, and inclusion bands. The analysis results suggested methods to prevent such defects in continuously cast steel billets and to reduce/eliminate split end problems. The casting parameters should include: (a) Mn/S ratio >35, (b) degree of superheat <60 °C, and (c) casting speed: <3.0 m/min, where roll radius and initial thickness of the workpiece should be optimized.     

Inductance of magnetically shielded air-core coils of circular cross section

An expression for the inductance of shielded cylindrical air-core solenoids of arbitrary diameter to length ratio is developed. Three shielding configurations are investigated: 1) the use of a coaxial-concentric magnetic shield, 2) the coaxial magnetic shield with conducting end plates, 3) the coaxial magnetic shield with conducting end rings. Case 2) is solved in closed form by separation of variables, and from this result a method is given for predicting the length of the coaxial magnetic shield required to contain the field for the three cases.     

高压换热器U形管管口开裂分析

对高压换热器U型管泄漏进行了化学成分分析、力学性能测试、显微组织和断口的宏微观分析。检验结果显示，换热管材料的化学成分和力学性能符合相关标准的要求，显微组织正常；换热器管口开裂为连多硫酸应力腐蚀开裂。     

9Cr2Mo钢转向辊调质开裂原因分析

通过化学成分分析、宏观和微观检验对9Cr2Mo钢辊身近端部纵向开裂的原因进行了分析。结果表明：材料化学成分超标、内裂纹的存在、原始组织晶粒粗细差异都对裂纹的形成产生了直接影响。最后根据分析结果制订了改进措施。     

微流星及空间碎片高速撞击航天器风险度分析

给出了微流星及空间碎片高速撞击航天器风险分析的方法 ,并采用风险分析软件 ,以柱状近地轨道航天器为例 ,对不同防护结构方案、航天器的飞行姿态、防护屏的厚度以及航天器的运行时间等因素对航天器不发生穿孔损伤的影响进行了分析 ,给出了分析的结果     

超高强钢前纵梁零件冲压开裂分析与处理

目的解决780 MPa级别超强度钢板冷冲压生产汽车前纵梁时发生的冲压开裂问题。方法通过网格应变分析技术和仿真分析,研究该零件冲压开裂的原因,分析引起开裂的因素,基于CAE模型系统,研究压边力、模具间隙、坯料尺寸、材料性能对开裂的影响规律。结果降低压边力和增加模具间隙均能减轻开裂,但是无法消除冲压开裂;坯料尺寸缩小可以消除冲压开裂,但是优化坯料尺寸需要改变模具上的坯料定位器,同时增大起皱风险;通过提升材料性能可以消除开裂。结论考虑最终各方案成本,选择性能优异的材料进行生产,将冲压开裂率降低至0.6%,满足了冲压要求。     

Computational analysis of a sandwich shield with free boundary inserted fabric at high velocity impact

In this paper, a novel hybrid composite shield to protect space structures from hypervelocity impact of micrometeoroid and space debris is proposed. The finite-element model of the proposed shield was constructed and finite-element analysis was conducted to approximate the energy absorption rate. Before the final model analysis, analysis of each component including the aluminum plate (front plate), PMMA plate (rear plate), and intermediate layer of fabric was performed, verifying the finite-element model of each component. The material properties used in the analysis were predicted material property values for high strain rates. The analysis results showed that, other than the fabric, the energy absorption rate of each component was in agreement. Afterwards, the finite-element model of the hybrid composite shield was constructed, where it was analyzed for the constrained and unconstrained fabric boundary condition cases. Through the finite-element analysis, the fiber pullout mechanism was realized for the hybrid shield with free boundary inserted fabric, and it was observed that this mechanism led to energy absorption increase.     

胶层厚度对碳纤维/双马来酰亚胺树脂复合材料平-折-平混合连接接头力学性能的影响

以碳纤维/双马来酰亚胺(BMI)树脂复合材料平-折-平(FJF)连接接头为对象,通过试验对比分析了特定胶层厚度下碳纤维/BMI树脂复合材料FJF连接接头的静强度和疲劳性能,并探究了胶层厚度对碳纤维/BMI树脂复合材料FJF混合接头力学性能的影响。利用背面应变技术对碳纤维/BMI树脂复合材料FJF混合接头搭接区端部胶层开裂进行监测。利用有限元软件ABAQUS对不同胶层厚度下碳纤维/BMI树脂复合材料FJF混合接头搭接区胶层应力分布进行了分析。结果表明,碳纤维/BMI树脂复合材料FJF混合接头的平均拉伸极限载荷、搭接区端部胶层开裂平均循环次数和平均疲劳寿命均随着胶层厚度在0.1~0.3 mm范围内增加而增大。不同胶层厚度的碳纤维/BMI树脂复合材料FJF混合接头均经历相同的失效阶段,即搭接区胶层端部开裂,胶层沿搭接区断裂扩展,最终靠近加载端孔边拉伸断裂,呈±45°断口。随着胶层厚度在0.1~0.3 mm范围的增加,搭接区端部胶层剥离应力、剪切应力及孔边胶层压缩应力均减小。在胶层厚度为0.1~0.3 mm范围内,剪应力是胶层破坏的控制因素。