首页期刊导航|Engineering failure analysis
期刊信息/Journal information
Engineering failure analysis
Elsevier Science
Engineering failure analysis

Elsevier Science

1350-6307

Engineering failure analysis/Journal Engineering failure analysisSCIEIISTP
正式出版
收录年代

    (105809)Failure analysis on aluminum alloy drill pipe with pits and parallel transverse cracks

    Wanying LiuJinyu LiYu Zhong
    13页
    查看更多>>摘要：In recent years, aluminum alloy drill pipe are used more and more frequently in the exploration and development of the deep wells, ultra-deep wells and sour gas wells due to the high strength, light weight and corrosion resistance to H_2S and CO_2. However, the pitting and fracture failure sometimes occurred, resulting in giant economic losses and fatal disaster. In this study, the failure analysis of aluminum alloy drill pipe was addressed and the formation cause of the pits and parallel transvers cracks was investigated. Results show that the chemical composition and the regular mechanical properties (including tensile and impact properties) meet ISO 15546:2011 standard requirements. But the tensile strength of samples immersed in the mud environment is lower than that of ISO 15546:2011 standard requirements. Metallographic analysis results show intermittent ribbon Al_6(MnFe) solid solution, S (CuMgAl_2) phase and AlFeSi phase distributed on a solid solution. The failure cause of aluminum alloy drill pipe is mainly attributed to the brit-deness sensitivity of intermittent banded second phase and inclusions to corrosive media from mud environment. Cracks and pits are prone to generate here. XRD and EDS analysis results of corrosion products and the pits bottom show that the main corrosion products are Al_2O_3, Al_2S_3, AlPO_4, BaSO_4 and CaCl_5. S and Cl are from environment media. The microscopic morphology analysis results of the tensile and impact specimens fracture show that the fracture is the britde fracture caused by the environmental medium.
      原文链接:
    • NSTL
    • Elsevier

    (105819)Atmospheric plasma sprayed thick thermal barrier coatings: Microstructure, thermal shock behaviors and failure mechanism

    Shiqian TaoJiasheng YangFang Shao
    15页
    查看更多>>摘要：Advanced thick thermal barrier coatings (TTBCs) have attracted extensive attentions due to the embedded segmentation-crack structure and excellent thermal insulation performance. The thermal shock life and failure behaviors of advanced TTBCs still remain a challenge. The objective of this work is to well understand the effect of microstructure on the coating cracking behavior in atmospheric plasma sprayed TTBCs system, in which the extended Raman spectroscopy (RS) techniques are used to obtain an in-depth understanding on how the oxidation affects the stress distribution in coatings and in turn, the causes of the observed cracking. Results show that the TTBCs deposited by the highly purified feedstock exhibit excellent thermal shock life at 1100 °C due to the well-proportioned and compact structure and built-in vertical cracks. After thermal shock test, the broken regions usually occur at the horizontal cracks and vertical cracks area within top-coat, and top-coat/bondcoat interface, which may suggest that each structural mutation parts are prone to causing the TTBCs instabilities. Cracks are propagated and extended under thermal tensile stress. The coating failure is most possibly dominated by the accumulated residual stress generated due to thermal expansion mismatch between the substrate and top-coat. In addition, the good thermal shock resistance have a close relationship with the newly formed vertical cracks at the bottom of ceramic coating near the top-coat/bondcoat interface.
      原文链接:
    • NSTL
    • Elsevier

    (105847)Integrated empirical and numerical approach for stability and failure analysis of cut slopes in seismically active Uttarakhand Himalayan, India

    Hari Om SinghT.N. SinghK.H. Singh
    25页
    查看更多>>摘要：In the recent past, the upper range of the Himalayas witnessed numerous cases of disasters (such as Kedarnath tragedy) and was responsible for huge destructions and instability of many slopes along the National Highway (NH-7) Uttarakhand, India. The crucial part of the road passes through cut slopes comprised of highly jointed rock mass and strong variation to persistence, spacing, and degree of fracturing observed at different locations. As the area is located in the seismically active Lesser Himalayan region, where numerous slope failures of great magnitude may be anticipated. This study was carried out to predict the potential instability of eight different slopes along NH-7 from Kaudiyala to Karakot, Uttarakhand, using empirical and numerical methods. Preliminary stability assessment includes rock mass characterization, kinematic analysis, and continuous slope mass rating (CoSMR), where rocks are generally blocky (fair surface) and undergoes mostly wedge failure. CoSMR and Q_(slope), both indicate that three locations are partially stable, while the rest of the other locations are unstable. Results of newly developed [BQ] and [BQ]_(gsi) systems are closely associated and classify slopes under partially stable (class III & IV) and unstable (class V), respectively. Afterward, an exhaustive study was carried out with numerical methods to inquire into failure mechanism and associated damage zone. The factor of safety was estimated from limit equilibrium, finite element stress-based approach, and continuum finite element method, where the majority of slopes are critically stable and unstable except few stable slopes. Further, the application of seismic loading substantially incited the slope instability, and result shows that the reduction in a static factor of safety is ranging from 22.22 to 50%, with an average of about 34.24% using different numerical methods. Additionally, seismic forces also alter the profile of stress-strain, strength, displacements, and other parameters predicted under the condition of gravity. Nonlinear Generalized Hoek-Brown failure criterion supersedes Mohr-Coulomb criterion failure almost to each profile and provides most vulnerability and authentic result in seismically active jointed rocks of Himalayan.
      原文链接:
    • NSTL
    • Elsevier

    (105855)Effect of bond-line thickness and mode-mixity on the fracture behavior and traction separation law of Sn-0.7Cu solder joints

    Ved Prakash SharmaNaresh V. Datla
    16页
    查看更多>>摘要：In this research, cohesive parameters were extracted for Sn-0.7Cu/Cu solder joint failure. Double cantilever beam (DCB) specimens were used to study the fracture of the joint under both mode-1 and mixed-mode conditions. A bilinear traction separation law (TSL) was used to capture the failure of the joint. Increasing the bond-line thickness from 110 to 880 urn increased the critical energy release rate for crack initiation (G_(ci)) and maximum traction of the bilinear TSL. This increase in the G_(ci) was attributed to an increase in plastic zone area (PZA) ahead of the pre-crack tip. Varying the mode-mixity with phase angle (ψ) in the range of 0°-33° showed an insignificant change in G_(ci) and maximum traction of the bilinear TSL.
      原文链接:
    • NSTL
    • Elsevier

    (105902)The effect of excessive penetration of welding on sand erosion pattern due to high speed gas-solid flows in elbows and reducers

    F. HosseiniA.H. Meghdadi IsfahaniM. Davazdah Emami
    19页
    查看更多>>摘要：The aim of the current study is to investigate the effect of excessive penetration of welding and natural gas impurity particles on increasing erosion in elbows and reducers. To this end Euler-Lagrange model is used to simulate the two-phase solid-gas flow, the Discrete Phase Model (DPM), k-e turbulent model and DNV erosion model are used to model the solid particles, natural gas flow and erosion rate, respectively. Erosion in elbows occurs downstream of vertical welding while in reducers is weaker and occurs at the inlet. The results show that erosion rate increases by increasing excessive penetration, particles size, particles flow rate and natural gas flow rate. The effect of excessive penetration becomes more important in high speed flows containing solid particles, in such a way that reducing excess penetration from h = 3 mm to h = 0 mm, causes 45% reduction in erosion rate in elbows containing 20 m/s natural gas flows. Therefore, for high velocity impure gas flows, it is recommended to reduce the allowable excessive penetration in welding standards.
      原文链接:
    • NSTL
    • Elsevier

    (105813)Fracture mechanisms in rails with mechanically and thermomechanically-induced white etching layers under three-point bending

    Ba Hieu NguyenAli Al-JubooriHongtao Zhu
    13页
    查看更多>>摘要：White etching layers (WELs) on rail surfaces play a crucial role in dictating rail life and guaranteeing safety during transport. It has been reported that the presences of WELs correlate with wheel-rail tribological properties and rail defects, including squats and studs. It is impossible to directly measure fracture mechanisms in WELs when rails are in service because they are subject to numerous wheel passage cycles, and WELs are routinely spalled due to dynamic impact throughout their lifetime. Consequently, samples containing mechanically and thermomechanically-induced WELs, as well as WEL-free samples were sectioned from ex-service rails and subjected to three-point bending to investigate crack initiation in WELs and compare the subsequent propagation of cracks into the base material leading to fracture. The results show that WELs are subject to intergranular brittle fracture and promote ductile crack growth before macroscopic river-like cleavage failure. In contrast, the WEL-free rail fails via a mixed-mode of quasi-cleavage fracture. Mechanically-induced WELs are more detrimental to rail life compared to their thermomechanically-induced counterparts on account of the former's high hardness and ultrafine microstructure resulting in more severe and numerous cracks. Moreover, the heavily deformed pearlite at mechanically-induced WEL-base material interfaces contributes to the lower fracture resistance and enhanced crack penetration from WEL to rail.
      原文链接:
    • NSTL
    • Elsevier

    (105806)On the mechanical properties and damage mechanisms of short fibers reinforced composite submitted to hydrothermal aging: Application to sheet molding compound composite

    Sahbi TambouraAbir AbdessalemJoseph Fitoussi
    11页
    查看更多>>摘要：Sheet Molding compound (SMC) composites were subjected to water immersion tests in order to study their durability since such composites are of interest in automotive applications. Water sorption tests were conducted by immersing specimens in distilled water at 25-90°C for different time durations. In order to investigate the combined action of water and temperature over time on composite mechanical behavior, tensile tests and quasi-static loading were conducted. The mechanical properties of water immersed specimens were evaluated and compared alongside to dry composite behaviour. The tensile tests and quasi-static properties of the studied composite were found to decrease with the increase in moisture uptake. This decrease was attributed toinner structure degradations by means of osmosis phenomenon. It was shown that hydrothermal aging affects mainly the fiber/matrix interfacial zone while a good adhesion between the reinforcement and the matrix was observed for the virgin samples. In order to well understand the damage mechanisms, scanning electron microspy (in-situ three point bending) tests were performed on aged and non aged specimens. Damage mechanisms were identified for different material states. Results display clearly that damage evolution always begins at the interface regions. Furthermore, a quantitave analysis was performed at a local scale in a representative zone of the tensile area.
      原文链接:
    • NSTL
    • Elsevier

    (105905)Disaster mechanism of tunnel face with large section in sandy dolomite stratum

    Ping ZhouYifan JiangFeicong Zhou
    19页
    查看更多>>摘要：During the construction of tunnels in sandy dolomite strata, the frequent occurrence of catastrophic instability of the tunnel face has brought great challenges and risks to the on-site tunnel construction. Therefore, the mineral composition of dolomite is analyzed, and the sanding mechanism of dolomite is explored from macro, meso and micro levels. Secondly, the triaxial test is designed through the particle gradation obtained by the screening test to obtain the sandy dolomite parameters under different sanding conditions. After parameter calibration, a three-dimensional discrete element calculation model is established to simulate the excavation of dolomite tunnels with different sanding degrees in the longitudinal, vertical and horizontal paths, and the disaster characteristics and evolution mechanism of the local disaster in front of the tunnel face are obtained. Based on the macro level, dolomite sanding mainly experiences four stages: slight sanding, medium sanding, severe sanding and disaster. When the sanding degree is less than 20%, the failure zone of the surrounding rock in front of the tunnel face is smaller, the stress field can be stabilized in a short time, and only a small range of stress unloading will be generated due to excavation. When the sanding degree reaches 20%, the failure zone in front of the tunnel face rapidly develops forward and upward, and the stress in the longitudinal, vertical and horizontal paths all changes suddenly, and the dynamic arching effect is obvious. It implies that 20% sanding degree is the mutation point of the stability of the tunnel face. As the sanding degree of the fine particle increases, the development of catastrophic sand inrush on the tunnel face gradually becomes faster, and eventually tends to be stable, indicating that the water inrush and sand inrush on the tunnel face will develop faster and faster without treatment. The research results can provide basic data for tunnel face reinforcement in sandy dolomite stratum.
      原文链接:
    • NSTL
    • Elsevier

    (105883)A finite element-based analysis approach for computing the remaining strength of the pressure equipment with a local thin area defect

    Yen-Ju LuChen-Hua Wang
    15页
    查看更多>>摘要：Upon facing a pressure equipment with a structure defect and the subsequent question as to if the equipment is qualified for continuous operation, the answer often resorts to enough strength. However, strength of a pressure equipment is never defined clearly. In API 579, in order for a pressure equipment with a local thin area (LTA) defect to be accepted for continuing use in operation, the remaining strength factor (RSF) of the equipment must exceed 0.9. RSF is defined as the ratio of the plastic collapse load (PCL) of equipment with defect to that of the equipment without any damage. Hence, accurate evaluation of the plastic collapse load is of utter importance to judge fitness of the equipment. In this research, a finite element (FEM) based methodology has been devised to obtain an accurate estimation of the plastic collapse load.What needs to be established first is a finite element model for the whole, undamaged vessel as the main model and the other is the surrounding region encompassing the LTA defect as the submodel. Pressure loadings are incrementally and continuously applied to the main model through load steps until the model can no longer sustain, and the plastic collapse load is the maximum load that a structure can safely carry. The cut boundary data from the main model is then passed on to the sub-model, and calculation is resumed with the same load steps until the PCL of the LTA is obtained. Then RSF is determined as the PCL of the vessel with an LTA to that of the original, damage free vessel. API 579 and ASME FFS propose the use of RSF as an indicator for assessing fitness of an equipment. Concept-wise, the term RSF is not sophisticated and sometimes is treated as rough guidance for assessing the remaining strength of a structure. However, the same concept must be treated differently as it is applied to determine whether the defect is allowed and the remaining life is needed, which ought to be a finite element-based approach. In this research, it is achieved through: 1. Representing the defect in the form of a submodel consisting of SOLIDS element in order to process the area of varied thicknesses, and. 2. Computing the plastic collapse load for both the undamaged finite element model of SHELL elements and the submodel of SOLIDS elements simultaneously.
      原文链接:
    • NSTL
    • Elsevier

    (105893)Failure analysis of an advanced high-strength steel

    J.H. Ramirez-RamirezF.A. Perez-GonzalezO.J. Zapata-Hemandez
    11页
    查看更多>>摘要：The continuous demand for the reduction of emissions of green-house gases from the transport industry has been the driving force behind the development of stronger materials capable to reduce the weight of light and heavy-duty vehicles. Advanced high strength steels contain complex microstructures composed of a variety of hard and soft components obtained by tailoring their chemical composition and processing conditions. Unfortunately, such mixed microstructures may promote failure of steels during the manufacture of structural components. The use of commercial and in-house mathematical models, in conjunction with traditional techniques for failure analyses, can offer a better understanding of the phenomena taking place and contribute to reduce the risk of failure of such structural parts. An exercise carried out to determine the causes behind the failure of an advanced structural steel during forming is presented in this work with a demonstration of how mathematical models were used to present alternatives and solutions to avoid further incidents while processing.
      原文链接:
    • NSTL
    • Elsevier