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起落架40CrNi2Si2MoVA钢螺桩断裂分析 总被引:1,自引:1,他引:0
起落架40CrNi2Si2MoVA钢螺桩在安装一段时间后发生了断裂。为确定螺桩断裂的原因,对断裂螺桩断口宏微观形貌、断裂螺桩及对比件的氢含量、材料的性能以及表面损伤等因素进行了检查,并对电镀工艺进行了评定。结果表明,裂纹主要起源于第一螺纹根部的机械损伤部位,源区以沿晶断裂特征为主,断裂件含氢量较高。综合分析认为。螺桩断裂性质为氢致延迟断裂,表面机械损伤对氢吸收和扩散的促进作用和40CrNi2Si2MoVA钢材料高强度所致的高氢脆敏感性是导致断裂的主要原因。 相似文献
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分析长圆螺纹套管接头工厂端发生脱扣事故的原因。观察失效试样的宏观形貌,检测套管材质的理化性能,对比分析脱扣接箍不同位置的外径、失效试样螺纹锥度,并对同批次套管试样进行实物对比试验,对螺纹接头进行拉伸条件下的有限元模拟分析。结果显示:失效套管材料屈服强度小于API Spec 5CT—2011标准要求值;螺纹接头工厂端上扣位置满足相关标准要求;脱扣接箍不同位置外径差异较小;脱扣接箍工厂端螺纹锥度波动范围较大;有限元力学模拟分析反推接头工厂端不会在上扣痕迹位置发生脱扣失效。长圆螺纹套管接头工厂端发生滑脱失效的主要原因是套管材料屈服强度偏低和现场浮动上扣导致螺纹接头发生松动。 相似文献
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发动机连杆螺栓发生断裂失效,通过断口宏微观观察、金相组织检查、硬度及拉伸性能测试、螺纹尺寸测量和化学成分分析,对连杆螺栓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;螺栓的金相组织及化学成分未见异常,硬度及拉伸性能符合要求,螺纹尺寸不符合标准要求。综合分析认为:螺栓发生松动是螺栓断裂的根本原因;螺栓松动与装配时预紧力过小和螺纹直径偏小有关。针对断裂原因,提出了预防措施。 相似文献
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柴油机排气管IN718合金螺栓使用过程中发生早期断裂,通过化学成分检测、拉伸试验、金相分析、断口形貌观察、析出相透射电镜观察等手段从螺栓材料组织结构、制造工艺两个方面探究了断裂失效的原因。结果表明,螺栓断裂的主要原因为滚压螺纹后表面处于高能状态,螺纹根部在随后的时效处理时析出大量纳米相,螺牙根部表层脆化所致。 相似文献
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目的 为了提高螺栓连接结构的可靠性,分析剪切激励下螺栓连接结构松动失效机理,并研究润滑脂对螺栓连接松动行为的影响。方法 基于自主设计的试验装置,开展了剪切激励下螺栓连接结构的松动试验,分析了两种润滑脂(MoS2润滑脂和锂基润滑脂)对螺栓连接结构松动行为的影响,试验结束后使用扫描电子显微镜分析螺纹表面的损伤情况。结果 在相同预紧力条件下,使用润滑脂的螺栓连接结构初始预紧力矩可降低30%~40%。螺栓连接结构所承受的剪切载荷存在门槛值,即当剪切载荷低于门槛值时,连接结构不会完全松动。在螺栓前三圈接触螺纹表面添加润滑脂(局部润滑),门槛值降低;在螺栓全部接触螺纹表面均添加润滑脂(完全润滑),门槛值进一步降低。当承受载荷幅值低于门槛值时,局部润滑有利于防松,螺栓连接结构的松动程度可降低20%以上。结论 螺纹接触界面的微观滑移和微动磨损是螺栓连接结构松动的主要原因,在螺纹接触界面添加润滑脂可有效减缓螺纹表面的微动磨损。 相似文献
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周健波 《特种铸造及有色合金》2012,32(9):818-820
压铸件螺纹脱模是压铸模设计的难点之一.针对压铸件内部有间断的部分内螺纹,设计了内斜滑块脱螺纹机构.内斜滑块在推杆作用下推出压铸件的同时,沿动模型芯导滑槽向内移动并脱出螺纹.在分析压铸件工艺性基础上,设计了模具结构,论述了模具工作原理,并给出了工艺参数.模具工作可靠,生产效率高,成形工件满足质量要求. 相似文献
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某U型螺栓在重载汽车底盘耐久试验过程中发生断裂失效,失效行驶总里程约为2100 km。本文通过断口分析和理化检验确定U型螺栓断裂失效的原因,同时讨论了螺纹表面黑色组织的形成原因及其对断裂失效的影响,并提出了针对黑色组织的改善措施。U型螺栓在服役过程中发生松动,导致其受到周期性冲击应力的作用,这是发生疲劳断裂失效的主要原因;同时,螺纹表面深度8~15μm的网状黑色组织,也促进了裂纹的萌生和扩展。 相似文献
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介绍了螺纹板切槽模的设计,以及模具中易损部件的结构和固定方式,不需从压力机上拆卸模具,就可完成易损部件的更换修理,从而提高模具及设备使用效率,降低生产成本。 相似文献
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《Science & Technology of Welding & Joining》2013,18(8):622-629
AbstractThe influence of threaded and wear simulated (half thread) tools on the mechanical properties of dissimilar Al alloy friction stir spot welds is investigated. With lower tool rotational speed settings, the failure loads of Al 5754/Al 6111 lap joints made using a threaded tool were clearly higher than that of a half thread tool. However, the failure load of the joints made using a half thread tool increased when the tool rotational speed increased, and finally, as the rotational speed was further increased, the failure load became almost the same as the failure load of joints made using a threaded tool. In Al 5052/Al 6061 butt joints made using the threaded and half thread tools, the area of the stir zone on the bonded cross-section corresponded with the actual bonded region on the fracture surface. Therefore, the thread on the rotating pin has limited influence on the mechanical properties of the friction stir spot lap joints. 相似文献
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Tubing thread inspection by magnetic flux leakage 总被引:2,自引:0,他引:2
The failure of the oil well tubing thread is a very serious problem which may result in accidents and repairs during well servicing. Routine inspections on the threads are thus necessary. This paper proposes a local magnetic flux leakage testing method to inspect the end of the pieces and introduces a certain kind of tubing thread testing equipment based on the magnetic flux leakage theory. The equipment consists of four key components—magnetizer, magnetic field inducer, linear scanner and synchronous sampling controller. The equipment can inspect and prevent tubing thread failures occurring in practice, such as rupture, thread abrasion, crack in the thread root, variations of the taper angle in the thread area, etc. It can meet the testing requirements of the tubing thread and has very wide application perspective. 相似文献
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针对油套管螺纹区的结构特点和缺陷特征,介绍了几种油套管螺纹区漏磁检测的实验方法、装置和实验结果。对远场磁场检测方法、带浮动的以及不带浮动的开放式漏磁检测方法进行了对比分析,总结出了一种方便、可行的油套管螺纹漏磁检测方法。 相似文献
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Development of ultrasonic thread root rolling technology for prolonging the fatigue performance of high strength thread 总被引:2,自引:0,他引:2
Minglong Cheng Deyuan ZhangHuawei Chen Wei Qin 《Journal of Materials Processing Technology》2014,214(11):2395-2401
Fatigue failure commonly occurs at mechanical products, especially the threaded joints with high stress concentration. Even though various high strength alloys are adopted, accidence due to fatigue failure of thread still happens. As a novel method to improve the thread fatigue life, ultrasonic thread root rolling (UTRR) process is developed in this paper. The configuration of the UTRR apparatus together with the principle of the UTRR is first introduced and described. Rolling experiments are then conducted on AerMer100 thread specimens by use of the UTRR process and conventional thread root rolling (CTRR) process respectively. Mechanical characteristics and fatigue properties for these treated specimens and untreated specimens are tested. Compared with CTRR, surface finish of thread root is farther improved from Ra 0.106 to Ra 0.051, and higher residual stress is achieved for UTRR. The depth of microstructure-refined zone induced in UTRR is about 20 μm, while that of CTRR is approximately 12 μm. These further enhanced mechanical properties greatly contribute to the improvement of fatigue performance, and it is well proved by fatigue results that an increase of about 7 times for fatigue life of AerMet100 specimens is achieved after UTRR, while only 3 times is achieved for CTRR. Striations from fracture surface explicitly confirm this result. 相似文献