Article

REVIEW OF DELAYED TANK CAR FAILURES.

January 1981

Authors:

The purpose of this study is to summarize the observations that have been made in conducting investigations of tank cars that have ruptured after being involved in derailments. The primary cars involved are the 112A340W or 400W (jumbo) cars containing 125 cubic meters (33,000 gallons) of liquified gas, such as ammonia or propane. The general characteristics of tank car fractures and the general fracture patterns observed in tank cars are described. Also, one specific type of fracture, the delayed fracture of a tank car due to mechanical damage is described. In addition, the results of recent research on the failure of mechanical damage defects is described.

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Article

Significance of embedded non-planar defects in transmission-pipeline girth welds - part 2

May 1995

This paper present girth-weld-defect research activity which lead to a new, three-tier, system of guidelines for setting girth-weld-defect-acceptance levels and limits. Based on the research, it was found that no pipeline failures were reported which initiated at buried or non-planar flows. Failure modes commonly referred to were surface cracks of various kinds, planar flaws, and fatigues ... [Show full abstract] failures. Evidently, fracture in pipeline girth weld is a rare occurrence and when it does not happen, it is generally attributable to sub-critical crack growth leading to final fracture. However, such failures are associated with surface cracks, frequently initiated by mechanical damage. Generally, brittle fractures are initiated directly from non-planar embedded defects in steel, but are characterized by prior sub-critical crack growth initiated at the non-planar defects.

Article

Flaw analyses of vintage LPG carafes in use in Argentine households

August 2002 · Engineering Failure Analysis

This paper discusses the failure of a vintage 10 kg LPG balloon or carafe, manufactured in 1968, and the following experimental study of material properties and fabrication procedures of other vessels of similar age. It is concluded that many of the carafes present fabrication and in-service defects, especially in the circumferential welds, that can become critical. Continuing use of these ... [Show full abstract] vessels is potentially dangerous, especially when the effectiveness of the post weld stress relief treatment can not be guaranteed.

Conference Paper

Full-text available

Numerical Analysis of the Effect of position and size of Crack on the Stress Intensity Factor (Case...

December 2017

A. Aid

The goal of this work is to analyze the severity of crack defects and to study the degree of damage of structures under various loading condition. The 2D FEM based on the computation of the J integral and the stress intensity factors (SIF) were used to analyze the fracture behavior of these structures. The effect of the position and size of the crack on the J integral and the (SIF) values were ... [Show full abstract] highlighted. The crack located in different position in the specimen. The obtained results by various methods show that the numerical analysis gave a good correlation of theoretical results.

Article

Full-text available

Behaviour of high-strength bolts at elevated temperatures under double-shear loading

September 2017 · ce/papers

During fire events, connections in steel structures may be subjected to large unanticipated deformations and loads. These fire effects can produce failures of connections, including local buckling of the connection zone, rupture of connection plates, shear rupture of bolts, and bolt tear‐out rupture of beam webs. Thus, a key issue in evaluating the response of structural systems to fire effects ... [Show full abstract] is the proper representation of material behaviour, including fracture, at elevated temperatures. Temperature‐dependent material behaviour of structural steel plates has been studied by many researchers, both experimentally and numerically. However, the behaviour of structural steel bolts at elevated temperatures, especially under shear loading, is not well established in the literature. This paper presents results from recently conducted tests of high‐strength structural bolts subject to double shear loading at elevated temperatures. The parameters varied between tests included the bolt grade, bolt diameter, and temperature. Bolt grades A325 and A490 were tested. For each bolt grade, three different diameters were tested (19 mm, 22 mm, 25 mm) at five different temperatures (20 °C, 200 °C, 400 °C, 500 °C, and 600 °C). Three tests were conducted for each combination of parameters. Degradation in the mechanical and material properties were characterized. In addition, a new component‐based model for high‐strength bolts was developed based on the experimental data. The component‐based model is shown to accurately account for the temperature‐dependent degradation of bolt shear strength and stiffness, while also providing the capability to model load reversal.

Article

Cracking analysis of cold-crimp shell

March 2013

By means of fracture failure in the process of cold-crimp shell by Thk. 90mm Q345R plate to macroscopic examination, chemical analysis, mechanical testing, metallurgical analysis and fracture analysis. The results showed that the plate surface defects and defects in parts hydrogen damage in shell of cold-crimp process fracture of the reasons.

Article

21316 Tensile and Bending Strength of Elastic Adhesive Joint for Plastic Material

March 2008 · The Proceedings of Conference of Kanto Branch

In this study, the tensile and bending tests were carried out to examine the strength characteristics of elastic adhesive joint for acrylic material with different adhesive layer thickness. At first, the failure stress of tensile test was compared with that of bending test. While the failure stress depends on the adhesive thickness for both tests, there was found an obvious difference in the ... [Show full abstract] failure stress between above two tests. However, the difference becomes small if the mean stress on tensile site is used in bending test. Besides, maximum energy density of bending test coincides with that of tensile test if it is defined at final separation. The optical examination upon failure surface shows that the tensile site of bending test is occupied by damage zone around many small bubbles. It was found that the tensile and bending strength characteristics of adhesive joint are common in several points.

Article

STUDY OF ADHESIVE JOINT FAILURES BY EVAPORATIVE RATE ANALYSIS

January 1969

Evaporative rate analyses using Carbon-14- tagged radioactive chemicals are used to identify the location of fracture in ruptured adhesive-bonded joints. Evidence is shown for both adhesive failure and adhered failure (surface layer failure).

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Full-text available

Critical damage value of AZ31B magnesium alloy with different temperatures and strain rates

January 2015 · Rare Metals

The uniaxial tensile tests were carried out at temperature ranging from room temperature (RT) to 523 K under strain rates of 0.001, 0.010 and 0.100 s−1 to obtain the flow stress of AZ31B magnesium alloy. The tensile tests were simulated by the finite element method (FEM) to calculate the critical damage values (D c) of the Cockcroft–Latham criterion to predict the occurrence of fracture defects. ... [Show full abstract] Finally, the effects of temperature and strain rate on D c were analyzed to predict the critical damage value’s evolution. The results demonstrate that the critical damage value changes in the range of 0.188–0.718. It increases as strain rate decreases at constant temperature, and increases with the increase of temperature under certain strain rate, but is more sensitive to the temperature.

Article

A study on the Creep Behavieo of Rene 80 Superalloy

January 1993 · Korean Journal of Materials Research

The effects of atmosphere on the creep rupture properties of Ni-base superalloy Ren6 80 were investigated. Creep rupture tests were performed at , 657MPa and 982%, 157MPa under Ar gas atmospheres. Creep rupture mode and rupture properties (rupture life and elongation) were similar in two different atmospheres under the condition of , 657MPa. However, the results at , 157MPa showed different creep ... [Show full abstract] rupture mode and life between air and Ar gas atmospheres. In air, it was shown that creep cracks were initiated at surface-exposed grain boundaries and propagated along grain boundaries. In Ar gas atmosphere, the cracks were initiated at inner grain boundaries and coalesced to surface cracks which cause cup-and-cone type fracture. Due to protective oxide layer formation, air test showed longer rupture life than Ar test.

Article

419 Prediction of Creep Rupture Lifetime in Unidirectional Composites

November 2006 · The Proceedings of the Materials and processing conference

Delayed fracture occurs in unidirectional composites as a result of accumulation of micro-damages, such as fiber breakage or time-dependent interfacial debonding. In this study, the creep rupture lifetime in unidirectional composites is predicted under consideration of the propagation of interfacial debonding and its effect on rupture lifetime and damage accumulation is examined. Predictions were ... [Show full abstract] performed for two cases that stress concentration on intact fiber adjacent to broken fiber is not taken into account or taken into account. For former case, the decrease in rupture strain due to time-dependent propagation of interfacial debonding is formulated. For latter case, Monte-Carlo simulation under consideration of interfacial debonding propagating fiber breakage point is performed. As a result, the propagation of stress concentration region is observed and it is thought to be dominant factor for time-dependent damage accumulation in unidirectional composites.

Article

Failure criteria for linear elastic materials with U-notches

September 2006 · International Journal of Fracture

This paper provides a simple, albeit accurate, criterion for prediction of the rupture loads of brittle, or quasi-brittle, U-notched samples, where linear elastic fracture mechanics is not applicable because blunted notches do not exhibit stress singularities. Good agreement is found between numerical predictions and experimental results. The results of fracture tests from 18 different ceramic ... [Show full abstract] materials and a polymer (at −60°C) are summarized and are used as a reference for checking the fracture criterion. Seven fracture criteria are reviewed and it is shown that all can be recast into the proposed criterion.

Article

Failure mechanisms of reed valves in refrigeration compressors

April 1999 · Wear

W. A Glaeser

Four examples of reed valve failures in refrigeration systems are described. Failure in each case was by fracture of one or more reeds in the valves. Most of the failures could be diagnosed as impact fatigue in nature. The fatigue originated at surface damage on the reed–valve contact surface resulting from impact and reed twisting. One failure could be traced to defects in the casting containing ... [Show full abstract] the valve seats.