Fatigue Modeling for Elastic Materials With Statistically Distributed Defects

2007 ◽  
Vol 74 (6) ◽  
pp. 1125-1133 ◽  
Author(s):  
Ilya I. Kudish
Keyword(s):  
New York ◽  
Fatigue Resistance ◽  
Mechanical Design ◽  
Contact Fatigue ◽  
Local Stress ◽  
New Model ◽  
Structural Fatigue ◽  
Crack Distribution ◽  
Applied Loading ◽  
Material Fatigue

The paper is devoted to formulation and analysis of a new model of structural fatigue that is a direct extension of the model of contact fatigue developed by Kudish (2000, STLE Tribol. Trans., 43, pp. 711–721). The model is different from other published models of structural fatigue (Collins, J. A., 1993, Failure of Materials and Mechanical Design: Analysis, Prediction, Prevention, 2nd ed., Wiley, New York) in a number of aspects such as statistical approach to material defects, stress analysis, etc. The model is based on fracture mechanics and fatigue crack propagation. The model takes into account local stress distribution, initial statistical distribution of defects versus their size, crack location, and orientation, and material fatigue resistance parameters. The assumptions used for the new model derivation are stated clearly and their validity is discussed. The model considers the kinetics of crack distribution by taking into account the fact that the crack distribution varies with the number of applied loading cycles due to crack growth. A qualitative and quantitative parametric analysis of the model is performed. Some analytical formulas for fatigue life as a function of the initial defect distribution, material fatigue resistance, and stress state are obtained. Examples of application of the model to predicting fatigue of beam bending and torsion and contact fatigue for tapered bearings is presented.

scholarly journals A Unified Approach to Contact and Structural Fatigue

2005 ◽  
Author(s):  
Ilya I. Kudish
Keyword(s):  
Crack Propagation ◽  
Statistical Treatment ◽  
Three Dimensional ◽  
Contact Fatigue ◽  
Local Stress ◽  
Asymptotic Formulas ◽  
Structural Fatigue ◽  
Material Defects ◽  
Crack Mechanics ◽  
Stress States

A unified model of fatigue that is applicable to a variety of mechanical in nature fatigue phenomena including contact and structural fatigue is introduced. The model considers two- and three-dimensional stress states. The model is based on crack mechanics, kinetics of crack propagation, and statistical treatment of material defects. The foundation of the model follows from the analysis [1, 2], a model of contact fatigue [3], and the asymptotic formulas for the stress intensity coefficients (see [4]) developed earlier. The model takes into account the local stress distribution, initial statistical distribution of defects versus their size, defect location and crack propagation directions related to the specific stress state of the material, material fatigue resistance parameters, etc. The main assumptions used for the model derivation and their validity are discussed.

Enhancement of Rolling Contact Wear and Fatigue Resistance of Wheel Steel by Laser Dispersed Treatment

2014 ◽  
Vol 891-892 ◽  
pp. 1797-1802 ◽  
Author(s):  
Dong Fang Zeng ◽  
Lian Tao Lu
Keyword(s):  
Wear Rate ◽  
Fatigue Resistance ◽  
Rolling Contact Fatigue ◽  
Fatigue Crack Initiation ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Wheel Steel ◽  
Premature Failure ◽  
Contact Wear ◽  
Delamination Wear

Ferrite-pearlite steel is the most widely used material for railway wheel. However, such wheel steel can not meet the strict demands for rolling contact wear and fatigue resistance with the rising speed and weight of traffic. The aim of this paper is to improve the rolling contact wear and fatigue resistance of wheel steel by laser dispersed treatment. Such treatment creates isolated glazed regions on the surface layer of wheel steel, which are composed of fine martensite and retained autensite and have an avera0ge hardness of 762HV0.3. Compared with the conventional laser surface treatment technologies, such as laser hardening, laser melting, or laser cladding, which have been applied for improving rolling contact wear and fatigue resistance of wheel/rail, the multiple overlapping laser tracks that cause the premature failure are avoided by laser dispersed treatment. The wear rate and rolling contact fatigue life of treated and untreated wheel steel were evaluated and compared by Amsler twin-disc testing machines in dry and lubricated condition, respectively. The test results show that laser dispersed treatment improves the rolling contact wear and fatigue resistance of wheel steel. The stable wear rate of the laser treated wheel steel is about 0.3 times that of untreated wheel disc and the average rolling contact life of treated wheel steel is about double that of the untreated steel. Further investigations show that the glazed regions suppress the plastic deformation of wheel steel. This inhibits the treated wheel steel from delamination wear and delays the formation of fatigue crack initiation.

Influence of TiN coating thickness on the rolling contact fatigue resistance of austempered ductile iron

Wear ◽  
2016 ◽  
Vol 350-351 ◽  
pp. 82-88 ◽  
Author(s):  
Diego Alejandro Colombo ◽  
María Dolores Echeverría ◽  
Ricardo Cesar Dommarco ◽  
Juan Miguel Massone
Keyword(s):  
Fatigue Resistance ◽  
Coating Thickness ◽  
Ductile Iron ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Austempered Ductile Iron ◽  
Tin Coating ◽  
Contact Fatigue Resistance

Estimation of Maximum Pressure Stress Intensity in a Welding Tee

2018 ◽  
Vol 140 (2) ◽  
Author(s):  
Martin Blackman
Keyword(s):  
New York ◽  
Empirical Relationship ◽  
Local Stress ◽  
Pressure Vessels ◽  
Maximum Pressure ◽  
Element Analysis ◽  
Pipe Bend ◽  
Process Piping ◽  
American Society ◽  
Pressure Stress

The required thickness of welding tees is neither specified in ASME (2012, “Factory-Made Wrought Buttwelding Fittings,” American Society of Mechanical Engineers, New York, Standard No. B16.9-2012) nor is a clear calculation method provided in codes such as ASME (2016, “Process Piping,” American Society of Mechanical Engineers, New York, Standard No. B31.3-2016). This can lead to uncertainty regarding the pressure capacity of a tee fitting, particularly one that has suffered from erosion or corrosion. Code methods including area replacement (ASME, 2016, “Process Piping,” American Society of Mechanical Engineers, New York, Standard No. B31.3-2016) or pressure-area (ASME, 2015, “Boiler and Pressure Vessel Code Section VIII Division 2,” American Society of Mechanical Engineers, New York, Standard No. BPVC-VIII-2-2015; BSI, 2014, “Unfired Pressure Vessels Part 3: Design,” BSI, London, UK, Standard No. BS EN 13445-3) do not directly account for the effect which the curvature of the crotch region may have on the stress state in the tee. The approach adopted in this work is to liken the geometry of the tee crotch to the intrados of a torus or pipe bend. The shell theory applicable to the torus is adapted for the tee in order to derive a relationship for circumferential membrane stress. An equivalent tube radius is assigned by determining the local radius of shell curvature in the plane passing through the crotch center of the curvature. The actual stresses in the tee crotch are significantly reduced by the adjoining straight portions. This effect is difficult to quantify theoretically and has thus been investigated by means of finite element analysis (FEA)-based assessments. An empirical relationship was then established providing a conservative correlation between the theoretical stresses and the program calculated local stress intensities.

Micromechanics Modeling of Crack Initiation Under Contact Fatigue

1994 ◽  
Vol 116 (1) ◽  
pp. 2-8 ◽  
Author(s):  
W. Cheng ◽  
H. S. Cheng ◽  
T. Mura ◽  
L. M. Keer
Keyword(s):  
Crack Initiation ◽  
Surface Crack ◽  
Contact Fatigue ◽  
Contact Boundary ◽  
Dislocation Pileup ◽  
Near Surface ◽  
New Model ◽  
Crack Initiation Life ◽  
Micromechanics Modeling ◽  
Surface Crack Initiation

Using dislocation pileup theory, a model is given for the prediction of crack initiation life under contact fatigue. Near surface crack initiation is investigated by introducing the sliding contact boundary condition. Crack initiation originated at the surface and substrate are treated as extreme cases. The new model physically explains how a surface crack can be initiated and shows that the surface crack initiation life should be shorter than the subsurface crack initiation life under the same stress amplitude conditions. A discussion is given about the influence of residual stress, hardness, temperature, irreversibility of the plastic deformation, as well as other parameters that affect the crack initiation life. Preliminary comparisons show that the new model agrees well with the experimental observations of surface and near surface crack initiation.

Prediction of Equivalent Radial Loads for Tapered Roller Bearings

1996 ◽  
Vol 118 (3) ◽  
pp. 651-656
Author(s):  
Ted E. Bailey ◽  
Robert W. Frayer
Keyword(s):  
Fatigue Life ◽  
Rolling Contact Fatigue ◽  
Roller Bearing ◽  
Contact Fatigue ◽  
Subsequent Development ◽  
Rolling Contact ◽  
Tapered Roller Bearing ◽  
Applied Loading ◽  
Tapered Roller ◽  
Tapered Roller Bearings

Calculating the fatigue life of a tapered roller bearing has become a rather straightforward exercise thanks to the accumulation of rolling contact fatigue data and the subsequent development of formulation relating applied loading to bearing fatigue life. An integral part of the prediction process is to define an equivalent radial load (EQRL) by combining a bearing’s applied radial and thrust loading into a single entity. This paper reviews currently accepted formulation and offers a potentially more accurate alternative method for estimating the EQRL of a tapered roller bearing than does the current AFBMA standard.

Rolling contact fatigue resistance of PVD CrN and TiN coated austempered ductile iron

Wear ◽  
2013 ◽  
Vol 308 (1-2) ◽  
pp. 35-45 ◽  
Author(s):  
Diego Alejandro Colombo ◽  
María Dolores Echeverría ◽  
Sebastián Laino ◽  
Ricardo Cesar Dommarco ◽  
Juan Miguel Massone
Keyword(s):  
Fatigue Resistance ◽  
Ductile Iron ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Austempered Ductile Iron ◽  
Contact Fatigue Resistance
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