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Failure of Nylon Hinges 尼龙铰链失效
ASM Failure Analysis Case Histories: Automobiles and Trucks Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.auto.c0090466
{"title":"Failure of Nylon Hinges","authors":"","doi":"10.31399/asm.fach.auto.c0090466","DOIUrl":"https://doi.org/10.31399/asm.fach.auto.c0090466","url":null,"abstract":"\u0000 A production lot of mechanical hinges used in an automotive application had failed during incoming quality-control routine actuation testing. A change in part supplier had taken place between the approval of the prototype parts that performed acceptably and the receipt of the first lot of production parts. The mechanical hinges were specified to be injection molded from an impact-modified, 13% glass-fiber-reinforced nylon 6/6 resin. Investigation of samples representing the failed components and the original prototype parts included visual inspection, 118x SEM images, micro-FTIR, DSC analysis, and TGA. It supported the conclusion that the hinge assemblies failed through brittle fracture associated with stress overload during the actuation of the parts. The failed part material was found to be degraded, most likely occurring during the compounding of the resin or during the actual molding of the parts. While resins for both failed and non-failed parts produced results characteristic of a 13% glass-fiber-reinforced, impact-modified nylon 6/6, the failed part material, contained a significantly lower level of rubber, which rendered the parts less impact resistant and subsequently lowered the ductility of the molded hinge assemblies. No recommendations were made.","PeriodicalId":235345,"journal":{"name":"ASM Failure Analysis Case Histories: Automobiles and Trucks","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130889413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Relaxation of Nylon Wire Clips 放松尼龙线夹
ASM Failure Analysis Case Histories: Automobiles and Trucks Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.auto.c0090433
{"title":"Relaxation of Nylon Wire Clips","authors":"","doi":"10.31399/asm.fach.auto.c0090433","DOIUrl":"https://doi.org/10.31399/asm.fach.auto.c0090433","url":null,"abstract":"\u0000 A production lot of plastic wire clips was failing after limited service. The failures were characterized by excessive relaxation of the clips, such that the corresponding wires were no longer adequately secured in the parts. No catastrophic failures had been encountered. Parts representing an older lot, which exhibited satisfactory performance properties, were also available for reference purposes. The clips were specified to be injection molded from an impact-modified grade of nylon 6/6. However, the part drawing did not indicate a specific resin. Investigation included visual inspection, micro-FTIR in the ATR mode, and analysis using DSC. The spectrum representing the reference parts showed a relatively higher level of a hydrocarbon-based impact modifier, while the results obtained on the failed parts showed the presence of an acrylic-based modifier. Also, the reference clip thermogram showed a melting transition attributed to a hydrocarbon-based impact modifier. The conclusion was that the control and failed clips had been produced from two distinctly different resins. It appeared that the material used to produce the failed clips had different viscoelastic properties, which produced a greater predisposition for stress relaxation.","PeriodicalId":235345,"journal":{"name":"ASM Failure Analysis Case Histories: Automobiles and Trucks","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128970330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Stress-Corrosion Cracking of Carbon Steel Hoppers by Ammonium Nitrate Solution 碳钢料斗在硝酸铵溶液中的应力腐蚀开裂
ASM Failure Analysis Case Histories: Automobiles and Trucks Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.auto.c0091598
{"title":"Stress-Corrosion Cracking of Carbon Steel Hoppers by Ammonium Nitrate Solution","authors":"","doi":"10.31399/asm.fach.auto.c0091598","DOIUrl":"https://doi.org/10.31399/asm.fach.auto.c0091598","url":null,"abstract":"\u0000 After 10 to 20 months of service, the carbon steel hoppers on three trucks used to transport bulk ammonium nitrate prills developed extensive cracking in the upper walls. The prills were discharged from the steel hoppers using air superchargers that generated an unloading pressure of approximately 11 kPa (7 psi). Each hopper truck held from 9,100 to 11,800 kg (10 to 13 tons) of prills when fully loaded and handled approximately 90,700 kg (100 tons) per month. The walls of the hoppers were made of 2.7 mm (0.105 in.) thick flat-rolled carbon steel sheet of structural quality, conforming to ASTM A 245 (obsolete specification replaced by A 570 and A 611). Investigation (visual inspection and 100x micrographs polished and etched with nital) supported the conclusion that failure of the hoppers was the result of intergranular SCC of the sheet-steel walls because of contact with a highly concentrated ammonium nitrate solution. Recommendations included the cost-effective solution of applying a three-coat epoxy-type coating with a total dry thickness of 0.3 mm (0.013 in.) to the interior surfaces of the hoppers.","PeriodicalId":235345,"journal":{"name":"ASM Failure Analysis Case Histories: Automobiles and Trucks","volume":"229 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130940116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Fracture of Supplementary Axle-Support Channels for a Highway Trailer Caused by Restricting Welds 某公路挂车辅助轴支通道因限制焊缝而断裂
ASM Failure Analysis Case Histories: Automobiles and Trucks Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.auto.c0047521
{"title":"Fracture of Supplementary Axle-Support Channels for a Highway Trailer Caused by Restricting Welds","authors":"","doi":"10.31399/asm.fach.auto.c0047521","DOIUrl":"https://doi.org/10.31399/asm.fach.auto.c0047521","url":null,"abstract":"\u0000 A supplementary axle, which was used as an extension to a highway-trailer tractor to increase its load-bearing capacity, failed in service. The rolled steel channel extensions that secured the axle assembly to the tractor main-frame I-beams fractured transversely, with the crack in each instance initiating at a weld that joined the edge of the lower flange to the support bracket casting. The cracks propagated through the flange on each side until the effective cross-sectional area had been reduced sufficiently to bring about sudden and complete fracture of the remaining web and upper flange. Fatigue fracture was caused by a combination of high bending stresses in the bottom flanges of the channels due to the heavy load being carried, concentration of stresses due to the rapid change in section modulus of the channel at its point of attachment to the support-bracket casting, and brittleness of the high-hardness HAZ of the weld associated with the abnormally high carbon content in the central part of the channel. Welding of channel edges contributed to harmful gradients in section moduli and should be avoided in future assemblies.","PeriodicalId":235345,"journal":{"name":"ASM Failure Analysis Case Histories: Automobiles and Trucks","volume":"282 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123089063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Fisheye Blemishes in Two Motorcycle Components 两个摩托车部件的鱼眼缺陷
ASM Failure Analysis Case Histories: Automobiles and Trucks Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.auto.c9001625
S. Suess
{"title":"Fisheye Blemishes in Two Motorcycle Components","authors":"S. Suess","doi":"10.31399/asm.fach.auto.c9001625","DOIUrl":"https://doi.org/10.31399/asm.fach.auto.c9001625","url":null,"abstract":"\u0000 Two acrylic-coated polymeric motorcycle components exhibited fisheye blemishes after painting. SEM and EDS results showed relatively high levels of sulfur and chlorine associated with the blemishes in both parts. This suggested some adherent residual substances, possibly in the form of processing fluids and/or cleaning agents, were left on the surface just prior to painting and resulted in the observed fisheye blemishes. One of the components also showed evidence of mechanical damage, in addition to detectable iron, which suggests that the part surface may have been damaged from contact with a ferrous material, such as a steel chip.","PeriodicalId":235345,"journal":{"name":"ASM Failure Analysis Case Histories: Automobiles and Trucks","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122081485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Failure of High Tensile Bolts 高强度螺栓失效
ASM Failure Analysis Case Histories: Automobiles and Trucks Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.auto.c9001678
N. C. Kothari
{"title":"Failure of High Tensile Bolts","authors":"N. C. Kothari","doi":"10.31399/asm.fach.auto.c9001678","DOIUrl":"https://doi.org/10.31399/asm.fach.auto.c9001678","url":null,"abstract":"\u0000 Six galvanized high-tensile steel bolts were used to hold the wheels of a four-wheel drive vehicle. The right hand rear wheel of this vehicle detached causing the vehicle to roll and resulting in considerable damage to the body. The wheel was detached by shearing of four of the bolts and stripping the nuts from the other two bolts, which remained unbroken. SEM fractography of the fracture surfaces of the four broken bolts indicated that the failure was due to reversed bending fatigue. Optical microscopy indicated that the bolts were heat treated to a tempered martensite structure and that the nuts were manufactured from low carbon steel. The paper discusses the influence of the microstructure on the failure process the events surrounding the nature of incident and the analysis of in-service failure of the failed components utilizing conventional metallurgical techniques.","PeriodicalId":235345,"journal":{"name":"ASM Failure Analysis Case Histories: Automobiles and Trucks","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125487480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Diesel-Engine Crankshaft That Fractured in Fatigue Because of Subsurface Inclusions 由于地下夹杂物导致疲劳断裂的柴油机曲轴
ASM Failure Analysis Case Histories: Automobiles and Trucks Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.auto.c0047121
{"title":"Diesel-Engine Crankshaft That Fractured in Fatigue Because of Subsurface Inclusions","authors":"","doi":"10.31399/asm.fach.auto.c0047121","DOIUrl":"https://doi.org/10.31399/asm.fach.auto.c0047121","url":null,"abstract":"\u0000 A 1050 steel crankshaft with 6.4 cm (2.5 in.) diam journals that measured 87 cm (34.25 in.) in length and weighed 31 kg (69 lb) fractured in service. The shaft had been quenched and tempered to a hardness of 19 to 26 HRC, then selectively hardened on the journals to a surface hardness of 40 to 46 HRC. Visual inspection and 100x micrographs showed the fracture surface as having a complex type of fatigue failure initiated from subsurface inclusions in the transition zone between the induction-hardened surface and the softer core. The fractured shaft was examined for chemical composition and hardness, both of which were found to be within prescribed limits. This evidence supports the conclusions that the failure was caused by fatigue cracks that initiated in an area having an excessive amount of inclusions. The inclusions were located in a transition zone, which is a region of high stress. No recommendations were made.","PeriodicalId":235345,"journal":{"name":"ASM Failure Analysis Case Histories: Automobiles and Trucks","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117043658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Coolant Leakage Through a Cylinder-Head Exhaust Port Caused by Shrinkage Porosity 由缩孔引起的气缸盖排气口冷却液泄漏
ASM Failure Analysis Case Histories: Automobiles and Trucks Pub Date : 2019-06-01 DOI: 10.31399/asm.fach.auto.c0047263
{"title":"Coolant Leakage Through a Cylinder-Head Exhaust Port Caused by Shrinkage Porosity","authors":"","doi":"10.31399/asm.fach.auto.c0047263","DOIUrl":"https://doi.org/10.31399/asm.fach.auto.c0047263","url":null,"abstract":"\u0000 An engine cylinder head failed after operating just 3.2 km (2 mi) because of coolant leakage through the exhaust port. Visual examination of the exhaust ports revealed a casting defect on the No. 7 exhaust-port wall. A 0.9x examination of an unpolished, unetched longitudinal section through the defect indicated shrinkage porosity. This defect was found to interconnect the water jacket and the exhaust gas flow chamber. No cracks were found by magnetic-particle inspection. The gray iron cylinder head had a hardness of 229 HRB on the surface of the bottom deck. The microstructure consisted of type A size 4 flake graphite in a matrix of pearlite with small amounts of ferrite. this evidence supported the conclusion that the cylinder-head failure resulted from the presence of a casting defect (shrinkage) on the No. 7 cylinder exhaust-port wall interconnecting the water jacket with the exhaust-gas flow chamber. No recommendations were made.","PeriodicalId":235345,"journal":{"name":"ASM Failure Analysis Case Histories: Automobiles and Trucks","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129500612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Thermal Analyses of a Polymer Failure 聚合物失效的热分析
ASM Failure Analysis Case Histories: Automobiles and Trucks Pub Date : 1900-01-01 DOI: 10.31399/asm.fach.auto.c9001901
R. Kusy, J. Whitley
{"title":"Thermal Analyses of a Polymer Failure","authors":"R. Kusy, J. Whitley","doi":"10.31399/asm.fach.auto.c9001901","DOIUrl":"https://doi.org/10.31399/asm.fach.auto.c9001901","url":null,"abstract":"\u0000 Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to analyze an automotive polyoxymethylene (POM) sensor housing that was depolymerizing during service. It was found that a combination of heat, oxygen, and sulfuric acid attacked and caused premature failure of the part. POM should not be selected for automotive applications where elevated temperatures and acidic environments can exist. If exposure to acid is suspected, sodium bicarbonate should be applied to neutralize the surrounding environment, followed by copious quantities of water, and repeated until no effervescence is observed.","PeriodicalId":235345,"journal":{"name":"ASM Failure Analysis Case Histories: Automobiles and Trucks","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122370216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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