An Efficient Asymptotic Approach for Assessing Fatigue Reliability

1999 ◽  
Vol 121 (2) ◽  
pp. 220-224 ◽  
Author(s):  
J. Tang
Keyword(s):  
Random Process ◽  
Fatigue Failure ◽  
Equivalent Stress ◽  
Iteration Algorithm ◽  
Fatigue Reliability ◽  
Design Choice ◽  
Process Reliability ◽  
Cumulative Fatigue Damage ◽  
Technical Model ◽  
Technical Reliability

By applying the cumulative fatigue damage to the random process reliability problem, and the introduction of a proposed concept of unified equivalent stress mean level in fatigue life prediction, a technical reliability model for the random process problem under fatigue failure is proposed. The technical model emphasizes efficiency in the design choice and focuses on the accuracy of the results. Based on this model, an asymptotic method for fatigue reliability under random process loading is developed. The proposed method uses the recursive iteration algorithm to achieve results which include reliability and its corresponding mission life. The method reconciles the requirement of accuracy and efficiency for the random process reliability problems under fatigue failure. The accuracy and analytical and numerical efforts required are compared. Through numerical example, the advantage of the proposed method is demonstrated.

scholarly journals Evaluation of contact fatigue risk of a carburized gear considering gradients of mechanical properties

Friction ◽  
2019 ◽  
Vol 8 (6) ◽  
pp. 1039-1050
Author(s):  
Wei Wang ◽  
Huaiju Liu ◽  
Caichao Zhu ◽  
Jinyuan Tang ◽  
Chenxu Jiang
Keyword(s):  
Mechanical Properties ◽  
Fatigue Failure ◽  
Equivalent Stress ◽  
Contact Fatigue ◽  
Surface Hardness ◽  
Engineering Practice ◽  
Case Hardening ◽  
Failure Risk ◽  
Spalling Failure ◽  
Carburized Gear

AbstractCarburized gears are widely used in geared machines such as wind turbines. Contact fatigue problems occur in engineering practice, reducing reliabilities of machines. Contact fatigue failures are related to many factors, such as gradients of mechanical properties of the hardening layer. In this work, an elastic-plastic contact model of a carburized gear is developed based on the finite element method to evaluate contact fatigue failure risk, considering variations in hardness and strength. The Dang Van multiaxial equivalent stress is calculated via Python coding within the Abaqus framework. The gradient of yield strength along the depth from case to core is considered. The concept of local material fatigue failure risk is defined to evaluate the probability of pitting failure. The effects of design factors, such as the case hardening depth (CHD), surface hardness, and contact pressure on fatigue failure risk, are studied. As the CHD increases or the surface hardness decreases, the risk of deep spalling failure reduces. The increase in surface hardness leads to a decreased risk of pitting failure, while the variation in CHD hardly affects the pitting failure risk.

Fatigue Reliability Based Optimal Replacement Decision of Mechanical Components

2004 ◽  
Author(s):  
Jun Tang ◽  
Young Ho Park
Keyword(s):  
Decision Making ◽  
Fatigue Life ◽  
Random Process ◽  
Fatigue Failure ◽  
Cumulative Damage ◽  
Analytical Models ◽  
Damage Distribution ◽  
Optimal Replacement ◽  
The Mean ◽  
Mechanical Components

This paper introduces a maintenance decision-making strategy in the general area of replacement and reliability of mechanical components. The decision-making strategy involves the optimization of replacement interval based on fatigue failure of mechanical components. This new approach is based on the cumulative damage distribution function for evaluating mean fatigue life. By using the approach, the analytical expressions for the mean and the variance of the cumulative damage distribution under both stationary narrow-band and stationary wide-band random process are provided. The mean value and variance of the fatigue life distribution are thus evaluated to determine the optimal replacement intervals under fatigue failure. An algorithm of evaluating the mean and standard deviation of fatigue life is also presented. Therefore, the reliability of a component under random cyclic loading for a specified duration is quantified accordingly. Even though the new method introduces a great deal of complexity in the analytical models, this method can efficiently determine replacement intervals for component whose operating costs increases with use and replacement intervals for component subject to failure induced by the random process. An example is presented to demonstrate the application of the present method.

Fatigue Analysis of Pure Waterjet Nozzle-A CFD and FEA Approach

2011 ◽  
Vol 328-330 ◽  
pp. 1359-1364
Author(s):  
Quan Chang Li ◽  
Kai He ◽  
Ru Xu Du
Keyword(s):  
Stress Distribution ◽  
Fatigue Failure ◽  
Equivalent Stress ◽  
Element Analysis ◽  
Cavitation Damage ◽  
Theoretical Predictions ◽  
Incremental Sheet Metal Forming ◽  
Failure Point ◽  
Computational Fluid Dynamics Cfd ◽  
Velocity Pressure

The utilization of pure waterjet for Incremental Sheet Metal Forming (ISMF) is growing. However, the fatigue of pure waterjet nozzle is not fully clear. In the current study, based on the computational fluid dynamics (CFD) and finite element analysis (FEA), the fatigue failure of pure waterjet nozzle was simulated and analyzed. The influence of uneven equivalent stress distribution and generation of cavitation on nozzle fatigue failure was discussed. The results obtained from two simulations (velocity, pressure) show a good agreement with the theoretical predictions, which indicates that the approach based on CFD and FEA is absolutely feasible. Due to the uneven equivalent stress distribution, there is the first failure point inside the nozzle, which reduces the whole life of the nozzle. The unreasonable nozzle structure is one of main causes of cavitation generation; cavitation damage is reduced by optimizing the structure to improve the overall life of the nozzle.

Effect of Welding Procedure on Main Girder Fatigue Property

2014 ◽  
Vol 496-500 ◽  
pp. 666-672
Author(s):  
Gang Shen ◽  
Dong Xiang ◽  
Nan Liu ◽  
Peng Mou ◽  
Yong Yang ◽  
...  
Keyword(s):  
Fatigue Failure ◽  
Manufacturing Industry ◽  
Fatigue Property ◽  
Vertical Force ◽  
Bridge Crane ◽  
Fatigue Reliability ◽  
Welding Joint ◽  
Welding Procedure ◽  
Main Girder ◽  
Crack Position

Hoisting machinery is an important part of the equipment manufacturing industry, and the general bridge crane is the most widely used hoisting machinery. The main girder of bridge crane is the main load-bearing structure. Further, fatigue failure of main girder usually occurs not on the material itself but in the welding joint. The article has carried out three groups of experiments, which are experiment on fatigue property under vertical force, experiment on fatigue property under the comprehensive function of vertical force and horizontal force and experiment on failure mode of main girder under the prefabricated crack, to further discuss the effect of welding procedure on main girder fatigue property. Finally the following three conclusions are obtained. Firstly, the crack occurs closely to the middle position of welding place of the lower board and the main web, with the trend of scaling up along the main web perpendicular to the welding place. Secondly, the crack occurs on the main web close to the upper board, with the two-way expansion trend. Thirdly, fatigue failure cracks do not occur in the welding joint except the prefabricated crack position close to the square steel rail after the cyclic loading of two million times on main girder, which indicates that the uniformity of welding quality has an importance influence on the fatigue reliability of the whole main girder.

Fatigue Life of Thread Connection for Casing Drilling under Tension and Torsion

2008 ◽  
Vol 33-37 ◽  
pp. 255-260
Author(s):  
Feng Hui Wang ◽  
Qiong Wu ◽  
Ying Xi Wu ◽  
Sheng Yin Song
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Fatigue Failure ◽  
Equivalent Stress ◽  
Equivalent Strain ◽  
Test Machine ◽  
Proportional Loading ◽  
Thread Connection ◽  
Good Agreement ◽  
Casing Drilling

Casing drilling technique which has been dramatically developing is a revolution in petroleum industry and has aroused great concerns. The fatigue failure of casing thread connection is a critical issue for using. Therefore, to study the fatigue failure of casing connection is an important issue for understand the life of casing drilling. For the notched element, how to estimate the life and which parameter (equivalent stress, equivalent strain ,or the strain in the root )represent the damage under fatigue condition is still a problem. The purpose of this paper is to investigate the fatigue life of notch element under multiaxial stresses and to find out the damage parameter so as to predict the life of notch element. First specimen were machined with the same notch geometer dimension as the casing thread connection, fatigue tests with tension and torsion loading were carried out by fatigue test machine , for stress levels designed to obtain S-N lifetime curve. The stress and strain for the connections subjected to proportional loading were analyzed by elastic-plastic finite element method. The stress-strain state for notched specimens subjected to constant amplitude proportional multiaxial loadings was also calculated and analyzed by the finite element model. Take the equivalent stress, equivalent strain and the strain by FEM in the root into the prediction model, the strain by FEM has a good agreement with the experiment.But the results from the equivalent stress and equivalent strain also in good agreement with the experiment and is thought to be a simple prediction way.

Steel Fatigue Curves and its Impact on Bridge Performance

2014 ◽  
Vol 638-640 ◽  
pp. 1741-1744
Author(s):  
Liang Hong ◽  
Yu Hai
Keyword(s):  
Reinforced Concrete ◽  
Fatigue Failure ◽  
Fatigue Tests ◽  
Fatigue Reliability ◽  
Cross Sectional ◽  
Bending Fatigue ◽  
Hot Air ◽  
Fatigue Damage Accumulation ◽  
Bridge Performance ◽  
Metal Materials

Fatigue of steel and other metal materials focused on fatigue strength and fatigue damage accumulation in two ways. Continuous hot air axially deformed bars fatigue tests showed that fatigue failure often occurs at the maximum defect reinforced, and bending fatigue tests of reinforced concrete structures, fatigue failure often occurs in areas of reinforced concrete curved split effective cross-sectional area decreases place. This paper studies the construction of reinforced fatigue effect on the structural performance and the fatigue reliability theory has some theoretical significance.

Piston Engine Connecting Rod Transient Dynamic Finite Element Analysis and Maintenance Strategy

2014 ◽  
Vol 484-485 ◽  
pp. 272-276
Author(s):  
Fa Jun Ding
Keyword(s):  
Finite Element ◽  
Equivalent Stress ◽  
Fatigue Reliability ◽  
Connecting Rod ◽  
Piston Engine ◽  
Transient Dynamic Analysis ◽  
Element Analysis ◽  
Time Curve ◽  
Transient Dynamic ◽  
Maximum Equivalent Stress

Connecting rod is the very important connection and force bearing parts of piston engine crank mechanism; work in the role of various kinds of alternating stress. Taking a general rod from Lycoming IO-360-A1B6 aero-piston engine as the analysis object, first, a 3-D finite element model of the rod is established in ANSYS Workbench. And then, considering the influence of gas pressure in cylinder after ignition acting on the connecting rod under engines rated speed conditions, through the transient dynamic analysis, find in all load steps, the maximum equivalent stress occurred at the transition zone between the shaft and little head, and received the maximum equivalent stress versus time curve, to provide numerical basis for improving high-cycle fatigue reliability of the rod. Finally, according to equivalent stress contours of the rod when gas in cylinder peak pressure occurs, initially identified rods hazardous areas,to provide foundation for the development of standard repair process.

A Multiaxial Fatigue Reliability Analysis Method of Casing Drilling in Casing String

2011 ◽  
Vol 347-353 ◽  
pp. 1749-1753
Author(s):  
Ping Wang ◽  
Zhan Qu ◽  
Jiong Zhang ◽  
Jian Bing Zhang ◽  
Liang Wang
Keyword(s):  
Fatigue Life ◽  
Equivalent Stress ◽  
Multiaxial Fatigue ◽  
Analysis Method ◽  
Fatigue Reliability ◽  
Combined Stress ◽  
Biaxial Fatigue ◽  
Von Mises Equivalent Stress ◽  
Von Mises ◽  
Stress Criteria

The Von Mises equivalent stress criteria is used to equivalent convert and correct the uniaxial and biaxial fatigue reliability experimental study of the casing material. And the probabilistic fatigue P–S–N curve of the casing is gained. The fatigue limit and fatigue life in test is equivalent convert to actual casing by combined stress correction factor. A multiaxial fatigue life calculation formula is proposed by correcting the probabilistic fatigue P–S–N curve.

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