Crack modelling: A novel technique for the prediction of fatigue failure in the presence of stress concentrations

1997 ◽  
Vol 20 (1-2) ◽  
pp. 176-180 ◽  
Author(s):  
D. Taylor
Keyword(s):  
Fatigue Failure ◽  
Stress Concentrations ◽  
Novel Technique

Effect of Longitudinal Fastener Stiffness on Fastening System Loading - Initial Findings

2021 ◽  
Author(s):  
Christian J. Khachaturian ◽  
Marcus S. Dersch ◽  
J. Riley Edwards ◽  
Matheus Trizotto
Keyword(s):  
North America ◽  
Analytical Model ◽  
Fatigue Failure ◽  
Analytical Method ◽  
Vertical Load ◽  
Stress Concentrations ◽  
Laboratory Experimentation ◽  
The Past ◽  
Track Stiffness ◽  
Fatigue Failures

Abstract Over the past 20 years, there have been at least 10 derailments due to spike fatigue failures in North America. Researchers believe that fatigue failure is caused by a combination of lateral and longitudinal spike loading. The literature indicates the vertical load and fastener friction must be considered when estimating failure locations. Though the in-track vertical, lateral, and longitudinal fastener forces have been quantified at a location that has experienced spike failures, there is a need to account for additional fasteners and track locations. Fastening systems can affect track stiffness, thus, laboratory experimentation was performed to quantify stiffness of multiple fastening systems. This data was input into an analytical model which quantified the effect of stiffness on longitudinal fastener loading. The data indicate there is significant variance in fastening system stiffness within, and between, systems. However, this variation in fastener stiffness has a reduced effect on the load transferred to the fastening system. More work is needed to validate this in the lab or field given variability within a system could lead to stress concentrations that are not fully captured using the current idealized analytical method.

Calculation of the stress concentration factor in the welded tube junction subjected to combined loadings

2014 ◽  
Vol 11 (4) ◽  
pp. 339-348 ◽  
Author(s):  
A. Fouathia ◽  
A. Mekroud ◽  
K. Bellagh
Keyword(s):  
Stress Concentration ◽  
Fatigue Failure ◽  
Hot Spots ◽  
Combined Loading ◽  
Stress Concentrations ◽  
Tubular Joints ◽  
Out Of Plane ◽  
Welded Tube ◽  
Plane Bending ◽  
Shore Platforms

Fatigue failure caused by stress concentrations in tubular welded joints is observed in off shore platforms subjected to cyclic loading in corrosive marine environments. In some junctions, the stress concentration can induce a stress thirty times the nominal stress, and increase the risk of fatigue failure in tubular joints. Therefore, it is necessary to accurately assess the intensity of the stress concentrations to effectively deal with the problem of fatigue damage and lead to reliable tubular joints. This work aims to study the stress distribution and location of the "hot" spots in a Twelded tubular structure subjected to a combined loading of tension and bending (in-plane bending, out of plane bending and traction) to better simulate the actual loading.

A Novel Technique for Viewing Stress Distribution with Mechanoluminescence Materials

2008 ◽  
Vol 368-372 ◽  
pp. 1401-1404 ◽  
Author(s):  
Chen Shu Li ◽  
Chao Nan Xu ◽  
Hiroshi Yamada ◽  
Yusuke Imai ◽  
Hong Wu Zhang ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Numerical Calculation ◽  
Stress Concentration ◽  
Stress Distribution ◽  
Metal Substrate ◽  
Visualization Technique ◽  
Stress Concentrations ◽  
Novel Technique ◽  
Test Objects

We have successfully demonstrated that the stress distribution of a metal substrate can be directly displayed by coating SrAl2O4:Eu (SAO), a representative of strong mechanoluminescent materials, on the surface of test objects. An aluminum plate with SAO sensing film had been applied to experimental analysis of stress concentrations, and a numerical calculation via a finite element method confirmed that the observed real time mechanoluminescence images displayed the stress distribution. As a result, visualization of stress distribution on metal surface has been realized by ML images using SAO sensing film, and this novel visualization technique can be applied for viewing the stress concentration in various fields such as modeling, manufacturing and demonstration of an industrial product.

scholarly journals Common failures of ship propulsion shafts

Pomorstvo ◽  
2017 ◽  
Vol 31 (2) ◽  
pp. 85-90 ◽  
Author(s):  
Goran Vizentin ◽  
Goran Vukelić ◽  
Mateo Srok
Keyword(s):  
Failure Analysis ◽  
Fatigue Failure ◽  
General Description ◽  
Stress Concentrations ◽  
Propulsion Systems ◽  
Ship Propulsion ◽  
System A ◽  
Analysis Methodology ◽  
Fatigue Development ◽  
Marine Propulsion

This article aims to provide a critical review of the most common failures of ship propulsion systems as a crucial ship system, with emphasis on fatigue failure. The accent is given on the shaft of marine propulsion systems as a most common point of failures in the entire propulsion system. A general description of failure causes and failure analysis methodology is presented. Several representative case studies summaries for fatigue failure on critical points of the propulsion shaft are described. Torsional vibrations and geometric stress concentrations of the shaft are identified as the most common cause of fatigue failure. The importance of constant monitoring, measurement and data collection of fatigue indicators and indicative events that have influence on fatigue development is emphasized. Methods used in failure analysis are discussed and propositions for improvement are given, especially in terms of using numerical routines in failure prediction.

Study on the Mechanism of Fatigue Failure at Branch Connections Caused by Shell Mode Vibration

2017 ◽  
Author(s):  
Shunji Kataoka
Keyword(s):  
Fatigue Failure ◽  
Design Method ◽  
Acoustic Vibration ◽  
Beam Model ◽  
Stress Concentrations ◽  
Piping Systems ◽  
Mode Vibration ◽  
Rigid Model ◽  
Shell Vibration ◽  
Acoustic Fatigue

Acoustically induced vibration (AIV) is a vibration of piping systems caused by the acoustic loading generated mainly from pressure reducing devices. Recently, the capacities of the pressure reducing systems have been increased and some of the piping systems which are susceptible to acoustic fatigue, such as in flare and depressuring system. Demands on the development of reasonable design method for AIV is increasing. In this paper, the mechanisms of the fatigue failure of branch connection due to AIV were intensively studied. Firstly, the mechanism of the stress concentration was discussed. branch vibration caused by the shell mode vibration was assessed using several branch connection models, massless rigid model, fixed rigid model, and beam model. Next, the relationship between shell-vibration and stress concentrations is studied and re-organized based on acoustic vibration theories. Finally, the risk of the fatigue failure of the branch connection due to acoustic loading was discussed.

Sem Examinations of Glass Knives

1970 ◽  
Vol 28 ◽  
pp. 282-283
Author(s):  
J. Temple Black
Keyword(s):  
Plastic Deformation ◽  
Tensile Loading ◽  
Resultant Force ◽  
Stress Concentrations ◽  
Edge Chipping ◽  
Surface Flaws ◽  
Edge Defects ◽  
Microscopic Surface

There are two types of edge defects common to glass knives as typically prepared for microtomy purposes: 1) striations and 2) edge chipping. The former is a function of the free breaking process while edge chipping results from usage or bumping of the edge. Because glass has no well defined planes in its structure, it should be highly resistant to plastic deformation of any sort, including tensile loading. In practice, prevention of microscopic surface flaws is impossible. The surface flaws produce stress concentrations so that tensile strengths in glass are typically 10-20 kpsi and vary only slightly with composition. If glass can be kept in compression, wherein failure is literally unknown (1), it will remain intact for long periods of time. Forces acting on the tool in microtomy produce a resultant force that acts to keep the edge in compression.

Glass Knife Geometry as Seen by the SEM

1971 ◽  
Vol 29 ◽  
pp. 454-455
Author(s):  
J. Temple Black
Keyword(s):  
Low Cost ◽  
Amorphous Material ◽  
Stress Concentrations ◽  
Basic Tool ◽  
Tool Materials ◽  
Optical Inspection ◽  
Surface Flaws ◽  
Slip Planes ◽  
Glass Knife ◽  
Diamond Knife

In ultramicrotomy, the two basic tool materials are glass and diamond. Glass because of its low cost and ease of manufacture of the knife itself is still widely used despite the superiority of diamond knives in many applications. Both kinds of knives produce plastic deformation in the microtomed section due to the nature of the cutting process and microscopic chips in the edge of the knife. Because glass has no well defined slip planes in its structure (it's an amorphous material), it is very strong and essentially never fails in compression. However, surface flaws produce stress concentrations which reduce the strength of glass to 10,000 to 20,000 psi from its theoretical or flaw free values of 1 to 2 million psi. While the microchips in the edge of the glass or diamond knife are generally too small to be observed in the SEM, the second common type of defect can be identified. This is the striations (also termed the check marks or feathers) which are always present over the entire edge of a glass knife regardless of whether or not they are visable under optical inspection. These steps in the cutting edge can be observed in the SEM by proper preparation of carefully broken knives and orientation of the knife, with respect to the scanning beam.

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