压力容器和管道失效预测模型

综合评述了压力容器与管道的失效预测模型,介绍了一些较为广泛应用的压力容器和管道部件的失效预测模型。     

纤维缠绕玻璃钢管道的渗漏判据

本文通过对无矩层合板细观应变的有限元分析,求得层合板的最大应变集中系数。利用细观力学分析结果,建立了无矩层合板的树脂开裂宏观力学判据。利用该判据建立了管道的渗漏判据。并分析了纤维含量、温差、管径对渗漏压力的影响情况。      

水下爆炸作用下金属材料动态失效判据

该文章对某金属材料制成的圆筒形试件进行水下近距爆炸试验,得到了水下近距爆炸条件下材料的动态断裂应变,结合能量方法,给出了水下近距爆炸时材料的动态屈服强度,并和静态拉伸试验及霍普金森拉杆试验（SHTB）结果对比,比较了屈服强度、极限拉伸应变和能量吸收率等参数,并探讨了SHTB试验所得失效判据在水下爆炸对某金属材料制成的圆筒形试件进行水下近距爆炸试验,得到水下近距爆炸条件下材料的动态断裂应变,结合能量方法,给出水下近距爆炸时材料的动态屈服强度,并和静态拉伸试验及霍普金森拉杆试验（SHTB）结果对比,比较屈服强度、极限拉伸应变和能量吸收率等参数,并探讨SHTB试验所得失效判据在水下爆炸条件下的适用性。对比材料失效判据常规研究方法和水下爆炸实际效果,对于船体及其模型的结构抗爆设计和评估具有参考价值。条件下的适用性。该文章创新的对比了材料失效判据常规研究方法和水下爆炸实际效果,对于船体及其模型的结构抗爆设计和评估具有参考价值。     

管道连接头腐蚀失效分析

对石化厂管道连接头腐蚀泄漏失效进行了检查和分析，冷凝气体的液体介质含有Cl^-1和S^-2是产生点和晶间腐蚀的根源。错用钢材及运行后未及时清洗管道是导致点蚀和晶间腐蚀最终引起泄漏失效的主要原因。     

加氢精制装置高压临氢管道失效原因分析

某炼油厂柴油加氢精制装置的高压临氢管道在使用过程中突然爆炸起火.对该管道的失效原因进行较详尽分析后指出:由于管道长期在H2、H2S、高温、高压等恶劣工作环境下服役,材料受到氢腐蚀导致材质劣化使管道爆裂失效.严格按照Nelson曲线选用适宜的材料可以延长管道的使用寿命.     

油气管道失效分析与完整性管理

论述了油气管道的失效模式和失效原因,以及完整性管理的概念、流程和关键技术.对失效分析和完整性管理的关系进行了讨论,认为失效分析是油气管道完整性管理的基础;完整性管理是油气管道失效分析的延伸,是全面、科学有效的预测、预防管道失效的措施.     

过热蒸汽管道失效原因分析

本文针对某失效过热蒸汽管道,阐述了蒸汽管道常见的失效形式,并从微观和宏观角度出发,对失效管道的化学成分、机械性能、金相组织等理化检验及断口分析方面展开研究,从而准确判断过热蒸汽管道的失效原因。     

海洋石油平台井口管道腐蚀失效研究

海洋采油平台井口管道是腐蚀高发部位,一旦出现井口管道腐蚀失效现象,那么后果不堪设想。本文首先分析了海洋石油采油平台腐蚀特点,阐述了海洋石油采油平台井口管道的布置设计,同时,以某一实倒为例,就海洋石油平台井口管道腐蚀失效进行研究。     

Assessment on failure pressure of high strength pipeline with corrosion defects

An accurate prediction on the failure pressure of line pipe is very important in the engineering design and integrity assessment of oil and gas transmission pipelines. This paper analytically investigates the failure pressure of line pipes with or without corrosion defects, and focus on the high strength steels. Based on von Mises strength failure criterion, a classic strength failure criterion, the failure pressure of end-capped and defect-free pipe p_M is theoretically deduced with the strain hardening material. In order to derive a general solution for corrosion defect assessment of high strength pipelines, an extensive series of finite element analyses on various elliptical corrosion defects was performed. Finally, a new formula for predicting the failure pressure of corroded pipe in the material of high strength steels is formulated, based on the FE models and p_M, and is validated using 79 groups of full-scale burst test data, which contain the low, middle and high strength pipeline. The results indicated that the proposed formula for predicting the failure pressure is closely matches the experimental data for the high strength steels.     

Cone bit bearing seal failure analysis based on the finite element analysis

Failure analysis of cone bit bearing seals is important in reducing production cost and preventing in-service component failure. However, a generally accepted criterion for their failure has not yet been established because of complexities in both their material properties and the environment. In this study, a two-dimensional axisymmetric finite element analysis (FEA) numerical model was established. FEA software was developed based on the Mooney–Rivlin constitutive model of the rubber material, and the penalty function contact algorithm. The distributions of stress, strain and contact pressure were analyzed to establish their effect on failure. The locations and causes of the failure and preventive measures were determined by comparison with an actual failure case. It was found that stress concentration and uneven pressure distribution occur at the seal. Rubber rings are highly and unequally compressed. Metal ring structure mainly determines sealing performance. To reduce the occurrence of failure, the structure must be improved by: designing an appropriate angle-tapered metal ring end face structure instead of a plane to change the trend in pressure distribution, increasing the contact area of the metal ring end face to reduce contact pressure and make the contact pressure distribution more uniform to reduce sealing surface wear, reducing the radial thickness to reduce the compression of the rubber ring, and improving back support structures to reduce the stress concentration. Results from the study can prevent and minimize risk for future failures to increase bit life and reduce drilling costs.     

Design optimization of composites using genetic algorithms and failure mechanism based failure criterion

In this paper, minimum weight design of composite laminates is presented using the failure mechanism based (FMB), maximum stress and Tsai–Wu failure criteria. The objective is to demonstrate the effectiveness of the newly proposed FMB failure criterion (FMBFC) in composite design. The FMBFC considers different failure mechanisms such as fiber breaks, matrix cracks, fiber compressive failure, and matrix crushing which are relevant for different loading conditions. A genetic algorithm is used for the optimization study. The Tsai–Wu failure criterion over predicts the weight of the laminate by up to 86% in the third quadrant of the failure envelope compared to FMB and maximum stress failure criteria, when the laminate is subjected to compressive–compressive loading. It is found that the FMB and maximum stress failure criteria give comparable weight estimates. The FMBFC can be considered for use in the strength design of composite structures.     

An evaluation of failure criteria for matrix induced failure in composite materials

This paper reports on work being undertaken in the Cooperative Research Centre for Advanced Composite Structures Ltd. (CRC-ACS) to develop improved techniques for predicting the failure of composite materials. The procedures being investigated include a maximum strain criterion for fibre failure. For failure of the resin a new approach, which includes determination of the residual stresses due to manufacturing, is being trialed. This work closely parallels the new criteria proposed by Gosse and Hart-Smith [AIAA/CRC-ACS text on composite materials, submitted for publication] and we have subsequently replaced a simple stress criterion for matrix failure with their proposals based on strain invariants. The new procedures are applied to the failure of laminates in bolted joints with complex steered fibre patterns. Thermal residual stress was included to predict the matrix failure of T-section laminates under loads that open the angle between the flanges and the web. Here a transverse tension stress criterion was used.     

Failure analysis of carbon steel pipes used for underground condensate pipeline in the power station

In this paper, the cause of failure of an ASTM A53 Grade B carbon steel pipe was investigated. The investigated ASTM A53 Grade B pipe was used for a condensate pipeline and was found to be cracked after six months in service. The failed parts were investigated by means of stereoscopic microscope, optical microscope, scanning electron microscope equipped with energy dispersive X-ray spectroscopy micro-analysis, spark emission spectrometer, tension tester and Vickers hardness tester, in order to identify the failure causes and to suggest preventive solutions. A specially instrumented indentation tester was used for the measurement of residual stress on welding seam. The study shows that failure was mainly due to stress corrosion cracking caused by chloride and tensile residual stress on the welding seam due to insufficient heat input or low compression, etc during welding processing.     

Investigation of failure criteria for a sharp notch

In this study, a method of evaluating the static strength of a V-shaped notch based on the singular stress field at the notch tip is studied. The singular stress fields is defined by two parameters, and , which correspond to the intensities of symmetric stress field and the skew-symmetric field, respectively. Four kinds of fracture criteria are considered; two of them are based on the tensile strength σ _B and the other two are based on the fracture toughness K _IC . The usefulness of the criteria is investigated through the experimental results carried out on plane specimens of acrylic resin having a sharp notch for various notch configurations such as the opening angle, the inclined angle and the notch depth. It is shown that the criteria using stress intensity factor and the energy release rate not sensitive to the length of the virtual crack .     

A failure criterion for brittle elastic materials under mixed-mode loading

The failure criterion of Leguillon at reentrant corners in brittle elastic materials (Leguillon 2002, Eur J Mech A/Solids 21: 61–72; Leguillon et al. (2003), Eur J Mech A—Solids 22(4): 509–524) validated in (Yosibash et al. 2004, Int J Fract 125(3–4): 307–333) for mode I loading is being extended to mixed mode loading and is being validated by experimental observations. We present an explicit derivation of all quantities involved in the computation of the failure criterion. The failure criterion is validated by predicting the critical load and crack initiation angle of specimens under mixed mode loading and comparison to experimental observations on PMMA (polymer) and Macor (ceramic) V-notched specimens.     

Application of the point stress criterion to the failure of composite pinned joints

An analysis was performed to evaluate the bearing strength of pin-loaded composite joints using a two parameter characteristic curve model. This model involves determination of characteristic dimensions in tension and compression and based on this model, a two-dimensional stress analysis was used to determine the stress distribution around the fastener hole. In this analysis, characteristic dimensions in tension and compression were evaluated using the point stress failure criterion and joint bearing failure evaluated using the Yamada-Sun failure criterion. Results were compared with available experimental data for joints made from AS4/3501-6 graphite epoxy composite laminates and good correlation observed when evaluated as function of edge distance to hole diameter. However, the analysis yields conservative results when joint strength is evaluated as a function of plate width to hole diameter.     

Crankshaft failure analysis of a boxer diesel motor

This paper reports a failure mode analysis of a boxer diesel engine crankshaft. Crankshafts are components which experiment severe and complex dynamic loadings due to rotating bending combined with torsion on main journals and alternating bending on crankpins. High level stresses appear on critical areas like web fillets, as well as the effect of centrifugal forces and vibrations. Since the fatigue fracture near the crankpin-web fillet regions is one of the primary failure mechanisms of automotive crankshafts, designers and researchers have done the best for improving its fatigue strength. The present failure has occurred at approximately 2000 manufactured engines, and after about 95,000 km in service. The aim of this work is to investigate the damage root cause and understand the mechanism which led to the catastrophic failure. Recommendations for improving the engine design are also presented.