通过关键词查论文: Failure Analysis


作者: Yue Ting Niu, Xi Hui Mu, Xin Yong Qiao
摘要: Transmission casing fatigue fracture is one of the most serious failure of the transmission system in the form of tracked vehicles. This article through the analysis of materials and structural stress analysis of a typical fracture failure mechanism of the tracked vehicle transmission cabinet. And in obtaining the stress on the basis of load spectrum its fatigue life was calculated. The results show that in the structure of the stress concentration and cabinet material number ZL101 cast aluminum defects such as inclusions, porosity are the main cause of fatigue crack initiation and propagation.
作者: Yue Jun Zhang, Jin Fang Peng, Zhen Bing Cai, Min Hao Zhu
摘要: A railway axle operated over 6×105 km has been detected by varied micro-examination methods in detail. The examination of Leeb hardness tester results showed that the hardness of the press-fit seats presented higher hardness than that of other sites. According to the micro morphological analyses by optical microscope (OM), scanning electron microscope (SEM), energy dispersive X-ray spectrum (EDX), and profilometer on the surface at different press-fit seats, the most severe damage band was occurred at the inner edge of wheel seat near the gear seat. The transmission electron microscope (TEM) results indicated that the dislocation density of subsurface, beneath the axle surface about 20 μm, was much higher with a great deal of dislocation tangles, pile-ups and cellular structure formation. However, when the examination depth increased to 100 μm, no cellular structure can be founded, the dislocation density was very low, so the damage depth was less than 100 μm.
作者: George D. Quinn
摘要: The evolution of the science of fractography of brittle materials initially was driven by failure analysis problems. Early analyses focused on general patterns of fracture and how they correlated to the loading conditions. Many early documents are simply descriptive, but the curiosity of some key scientists and engineers was aroused. Scientific or engineering explanations for the observed patterns gradually were developed. Advances in microscopy and flaw based theories of strength and fracture mechanics led to dramatic advances in the state of the art of fractographic analysis of brittle materials. Introduction: This author was drawn backwards in time as he researched the current state of the art of fractographic analysis of brittle materials for his fractography guide book.[ ] Others have written about how the fractographic analysis of metals evolved (e.g., [ , , , ]), but there is no analogue for ceramics and glasses. The key scientists, engineers, and analysts who contributed to our field are shown in Fig. 1. Other work done by industry workers who were unable or loathe to publish is now lost, inaccessible, forgotten, or even discarded. It is the goal of this paper to review the key publications and mark the noteworthy advances in the field. Some deem fractography as the study of fracture surfaces, but this author takes a broader view. Fractography is the means and methods for characterizing fractured specimens or components and, for example, a simple examination of the fragments and how they fit together to study the overall breakage pattern is a genuine fractographic analysis.
作者: Dan Dan Wang, Jeffrey Lam, Zhi Hong Mai
摘要: Decapping is very important and essential for the MEMS failure analysis. Herein, we take a simple and environment friendly method to separate the device into MEMS and CMOS parts for CD measurements and failure analysis.
作者: Sanjeet Kumar, Deepak Kumar, Jayant Jain
摘要: Controlled friction and wear are the prime requirements of a braking system. The generation of wear debris depends on the brake materials properties, which in turn controls the tribological behavior. Present study deals with the performance evaluation and failure analysis of two commercial brake pads. Tribo Testing Rig (TTR) was used to evaluate the performance of brake. The tests were performed by making a tribo-pair of brake pad against the rotating disc with varying speed and pressure conditions. The wear response was quantified by mass loss, while the friction was measured in terms of coefficient of friction. Virgin and worn surfaces were analyzed using X-ray diffractometer (XRD), energy dispersive spectroscopy (EDAX) and Scanning electron microscope (SEM) to understand the wear and friction mechanisms. It was found that the type of constituents present in the brake-pad material and their spatial distribution plays an important role in controlling the wear and friction behavior. The high wear and friction was attributed to the presence of bulky particles of Fe and Si.
作者: Xiu Shan Sun, Vincent B.C. Tan, Yu Chen, Rajeev K. Jaiman, Tong Earn Tay
摘要: This paper proposes an efficient analytical failure analysis approach for multilayered composite risers used in the offshore oil industry. This approach is based on a layer-by-layer progressive damage model and a homogenization stress analysis method from which the discontinuous stresses through layers can be efficiently calculated. Different failure theories can be easily integrated into the approach to determine failure initiation in layers with different materials. Progressive failure analysis is based on layer-by-layer material degradation schemes, taking into consideration different failure modes such as yielding, fracture, matrix cracking, fiber broken, etc., in layers with different materials. In this approach, progressive failure information involving failed layers and their failure sequences as well as failure modes can be efficiently predicted for multilayered composite risers under given loading conditions. Failure envelopes of composite risers are generated for either initial failure or ultimate failure in different load spaces, and strengths of composite risers can be predicted under given load ratios. This analytical approach is efficient for failure analysis or strength prediction of composite risers with many layers because stress redistributions in all layers during failure progression can be easily and quickly calculated. A user-friendly interface based on Excel sheets is used to carry out this analytical failure analysis approach. Failure analyses of a 22-layer composite riser under several typical loading conditions are presented to demonstrate the application of the proposed approach. Initial and ultimate failure envelopes of the composite riser are shown in different force spaces. This failure analysis approach provides an efficient way for design of composite risers in the offshore oil and gas industry.
作者: H. Sepehri Amin, Ahmad Kermanpur, Saeed Ziaei-Rad, Hassan Farhangi, M. Mosaddeghfar
摘要: Several premature failures were occurred in the high-pressure section of an industrial gas turbine compressor due to the fracture of Titanium blade roots. In this work, the failure process of the compressor blades was investigated based on the experimental characterisation. Macro/microfractographic studies were carried out on the fracture surfaces. Optical and scanning electron microscopy of the blade airfoil and root were performed. Mechanical properties of the blade alloy were also evaluated and compared with the standard specifications. The experimental results showed no metallurgical and mechanical defects for the blade materials. Microstructures of the blade root and airfoil as well as the hardness and tensile properties were all comparable with those reported in the standard specification AMS 4928Q. Fractography experiments showed clearly multiple crack initiation sites and fatigue beach marks. Debris particles were observed on the fracture surface of samples and in the mouth of initiated cracks. The blade surface in contact to the disc in the dovetail region showed a higher surface roughness than the other surfaces. Based on the results obtained, the fretting fatigue mechanism was proposed for the premature failures. It was concluded that the stress concentration has been caused by either unsuitable curvature ratio of the disk dovetail, incorrect design of the blade or insufficient distance between the blade root and the disk in dovetail region.
作者: Fang Po Li
摘要: One drill pipe’ tool joint fractured rarely after just servicing ten days in drilling process of one natural gas well. Failure reason of tool-joint pin was researched through visual inspection, mechanical properties testing and working condition analysis. Results show that fracture failure reason is mainly due to the dramatic friction between the tool joint and the accumulated debris during the drill-string’s rotating process. Accumulated debris blocked mud’s circulation channel and leaded to poor circulation. The dramatic friction between the tool joint and accumulated debris leaded tool joint’s local temperature to risen significantly, and reduced its carrying capacity. In the end, tool joint fractured under the effect of tensile and torsional loads.
作者: Zdenek Cujan, Gabriel Fedorko
摘要: Industrial and commercial risks associated with the production, supply and commercialization of products and services provided by enterprise have effect not only on the enterprise run and its profitability, but in the extreme cause also on the viability and by that on the future of entire enterprise. Risk conditions create an assumption of enterprise crises which must be prevented.
作者: Adéla Podepřelová, Vratislav Mareš, Martin Kraus
摘要: The aim of the article is piston damage evaluation of a highly exposed combustion engine. The analysed piston was made of an AlSi-based alloy. Atypical damage, which occurred relatively early in the lifetime of the component, was evaluated by metallographic and fractographic analyses. The analysis took into account influences of mechanical and thermal fatigue processes in relation to the microstructure of the material. The metallographic observations of the microstructure revealed the occurrence of cracks extending over the secondary phases and precipitates. Cracks were initiated on the coarser Si phase particles. The crack initiation site is located at the root of the bridge between the sealing piston rings. The damage of the piston was metallographically documented in wide range.