This paper investigated the brittle fracture mechanism of a grade E cast steel knuckle that is one of the key components of the coupler for railway wagon. The fracture morphology mainly shows the characteristic of cleavage, quasi-cleavage fracture as well as a little ductile fracture, so the failure of the knuckle can be attributed to brittle fracture distinctly. Moreover, a welding repair area with high hardness is also found in the fracture region, which might initiate micro-cracks on the surface of the knuckle. As a result, it can be inferred that under an impact load that did not exceed material fracture limit, the micro-cracks initiated from weld repair zone propagated rapidly into the inner matrix by continuously fracturing the dendrites along shrinkage porosity regions until the knuckle failed instantly.
Les équipements sous pression sont soumis à de nombreuses sollicitations et leurs endommagements peuvent avoir des conséquences graves avec des impacts humain, industriel ou environnemental.
Différents outils sont aujourd’hui à notre disposition pour analyser ces dommages et aboutir au bon diagnostic. Ils nous guident également pour définir les actions préventives ou curatives à apporter pour autoriser la poursuite de l’exploitation de ces équipements.
Les spécialistes de l’analyse de défaillances au Cetim, régulièrement confrontés à ce genre de problématiques, vous feront part de leur expérience en s’appuyant sur des cas concrets.
Pour connaître le programme de la journée et s’inscrire : cliquez ici
In this essay, we will make a thorough study of the technical and administrative factors that contributed to the failure of the Shuttle Challenger project. Starting from paying attention from the planning stage, the implementation of the project, and even the consequences and further investigations, to be able to identify the lessons to be learned in both areas. It is expected that by completing this task, we can notice the critical factors that we need to pay particular attention to approaching ourselves as students that can develop projects successfully.
This paper, published on Engineering Failure Analysis, august 2017, présents corrosion failure analysis of an underground natural gas pipeline. The pipeline material grade is API 5L X65 with 10-in ID. The pipeline transfers multiphase fluid (gas, condensate, and water) from a gas well to a gas gathering plant, located 4200 m away from the well site. A portion of the line failed due to pitting corrosion under unknown circumstances. Based on visual and microscopic analyses and reviewing the background information, the following pitting corrosion sequences were identified: the oversized pipeline changed the dominant flow regime to “stratified”. In the stratified flow regime, the accompanying water phase accumulated in the pipelines’ low points. Considerable concentration of calcium ions along with high pH in CO2 media favored precipitation of calcium carbonate. The relatively thick scales adhered to the pipe surface were partially loosened and removed by the regional turbulent flow. This exposed the fresh steel surface to the corrosive media. The uncovered areas acted as the preferential anodic sites coupled with nearby large cathodic sites which were covered by scales and/or corrosion products. Under such conditions, pits emerged on the steel surface until one of them grew faster and failed the gas pipeline.
A thesis published by Conerstone : A Collection of Scholarly and Creative Works for Minnesota State University, Mankato.
Additive manufacturing (AM) also known as 3D printing has tremendous advancements in récent days with a vast number of applications in industrial, automotive, architecture, consumer projects, fashion, toys, food, art, etc. Composite materials are widely used in structures with weight as a critical factor especially in aerospace industry. Recently, additive manufacturing technology, a rapidly growing innovative technology, has gained lot of importance in making composite materials. The properties of composite materials depend upon the properties of constituent’s matrix and fiber. There is lot of research on effect of fiber orientation on mechanical properties of composite materials made using conventional manufacturing methods. It will be interesting and relevant to study the relationship between the fiber orientation and fiber volume with mechanical properties of additively manufactured composite materials. This thesis work presents experimental investigation of mechanical behavior like tensile strength and fatigue life with variation in fiber orientation and fiber volume fraction of 3D printed composite materials. The aim is to study the best combination of volume fraction of fiber and fiber orientation that has better fatigue strength for additive manufactured composite materials. Using this study, they can decide the type of orientation and volume percent for desired properties. This study also finds the range of fatigue limits of 3d printed composite materials .
Laminated glass is a simple sandwiched composite structure, while being widely used in the automotive industry as windshield glazings. It is considered to be safety glass due to its excellent performance in absorbing impact energy and bonding glass fragments. Meanwhile, the impact failure patterns of an automotive windshield glazing contribute to the traffic accident reconstruction. In recent decades, a growing interest has been devoted to the impact failure analysis of automotive laminated glass by means of numerical simulations. The purpose of this work is to present a comprehensive review concerning this aspect. We start by introducing six numerical algorithms for the modeling of the principal damage pattern, glass-ply cracking, followed by the introduction of material models for the plastic interlayer, PVB, and then address three numerical techniques for the adhesion modeling. Three kinds of laminated glass models are summarized. Finally, the performance of the numerical algorithms on the impact failure analysis of laminated glass in terms of glass-ply cracking and acceleration history is thoroughly discussed.
A new article in « Case Studies in Engineering Failure Analysis » published on Sciencedirect.com.
Gears are very reliable components and normally work 5 to 6 years without failure.
This article is a case study of failure analysis of a gearbox which was failed in three months after its installation. The problem was identified by maintenance engineers through vibration monitoring of gearbox.
An article published in « Materials Research« , april 2014.
An investigation was made to determine the causes of surface contact fatigue failure of a case hardened driver pinion located in the intermediate shaft of a reducer gearbox used in a sugar and alcohol mill. The examination of the component revealed the presence of a cemented layer substantially thicker than that generally specified for pinions devised for this application.
An interesting paper in « Engineering Failure Analysis »published on ScienceDirect.com.
Two different crane types suffered severe wind induced vibrations of tension bars for the counter weights during standstill periods. The vibrations led to fatigue fractures of tensions bars followed by collapses of the cranes. The parameters of wind speed and angle for the tension bar profiles were identified conducting comparative wind tunnel experiments. Recommendations for identification and prevention of wind induced galloping vibrations of tension bars were developed.