scholarly journals Discussions on the Prediction of Fatigue Life of Mechanical Structure and the Reliability Method

2018 ◽  
Keyword(s):  
Fatigue Life ◽  
Mechanical Structure ◽  
Reliability Method

The Fatigue Reliability Evaluation & Improvement of the Single-Arm Subway Current Collector

2012 ◽  
Vol 215-216 ◽  
pp. 826-831 ◽  
Author(s):  
Yu Chen ◽  
Zhi Ming Liu ◽  
Qiang Li
Keyword(s):  
Fatigue Life ◽  
Calculation Result ◽  
Dynamic Stress ◽  
Current Collector ◽  
Reliability Evaluation ◽  
Fatigue Reliability ◽  
Railway Vehicles ◽  
Load Spectra ◽  
Reliability Method

This study developed a fatigue reliability method for evaluating and improving the key parts on railway vehicles, which was applied to real structures. The study involved a type of single-arm current collector, while its contact shoe often collapsed in operation and needs improvements. The dynamic stress data from the actual line was tested and converted to load spectra based on damage consistency rule, and then the fatigue life of the contact shoe structure was achieved. The calculation result comes to correspond to its operation life. Based on the method, an improving plan for the structure was developed under optimizing algorithms.

Prediction Approach for Corrosion Fatigue Life of Aircraft Structure Based on Probabilistic Fracture Mechanics

2006 ◽  
Vol 324-325 ◽  
pp. 943-946
Author(s):  
Xiao Ming Tan ◽  
Yue Liang Chen ◽  
Ping Jin
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Corrosion Fatigue ◽  
Failure Process ◽  
Short Crack ◽  
Aircraft Structure ◽  
Probabilistic Fracture Mechanics ◽  
Fracture Failure ◽  
Reliability Method ◽  
Prediction Approach

The corrosion, corrosion fatigue and fracture failure process of aircraft structure is directly concerned with combined effect of many factors, such as load, material characteristics, corrosive environment and so on. The process is very complicated, and there is typical randomness. Based on probabilistic fracture mechanics, with consideration of the limitation of the conventional probabilistic approaches for prediction of corrosion fatigue life of aircraft structure at present, and a new reliability approach under loading spectrum was proposed, in which corrosion damage and fatigue crack damage was united as a same damage parameter. Short crack and long crack growth behavior was separately discussed, and influence of short crack aspect ratio on structure life was discussed. The Advanced First-Order Reliability Method, Importance Sampling Method and iteratively advanced Second-Order Reliability Method were used to compute the fracture failure probability. The results show that the model is feasible. By sensitivity analysis of random parameter, the important parameter was obtained, which helped to monitor the structure fatigue life.

scholarly journals Fatigue life assessment method of in-service mechanical structure

2021 ◽  
Vol 13 (2) ◽  
pp. 168781402199652
Author(s):  
Xiqiang Ma ◽  
Fang Yang ◽  
Jishun Li ◽  
Yujun Xue ◽  
Zhiqiang Guan
Keyword(s):  
Elastic Modulus ◽  
Fatigue Life ◽  
Modulus Of Elasticity ◽  
Evaluation Model ◽  
Assessment Method ◽  
Operating Conditions ◽  
Life Assessment ◽  
Model Parameters ◽  
Mechanical Structure ◽  
Proposed Model

The most usual failure mode of any mechanical structure is fatigue, which is characterized by an important feature of the decrease of elastic modulus of the material. In this paper, a fatigue life evaluation model based on equivalent elastic modulus is proposed for in-service mechanical structure. In the proposed model, parameters that represent the operating conditions of the mechanical structure, such as load, vibration, and shaft torque, etc., are used as the generalized load. To replace the fatigue stress, the statistical method is used here, which is also used in the conventional fatigue analysis method. The structural strain is also measured simultaneously. Using the statistical theory, the equivalent modulus of elasticity is formulated based on the relationship of stress, strain, and modulus of elasticity. To validate the proposed model, an online fatigue damage experiment has been conducted. The experimental results have been compared with that of the fatigue life prediction model with good agreement. It is expected that the methodology proposed in this paper will be widely used.

Estimation of Probability of Fatigue Failure on Tubular Joints

2021 ◽  
Author(s):  
N. Lokesh ◽  
S. Nallayarasu ◽  
S. Karunanithi
Keyword(s):  
Fatigue Life ◽  
Failure Mode ◽  
Fatigue Failure ◽  
Limit State ◽  
Probabilistic Approach ◽  
Fatigue Crack Initiation ◽  
High Stress ◽  
State Function ◽  
Reliability Method

Abstract Fatigue is generally considered the most critical failure mode in mechanical and structural systems. Due to high-stress concentrations, welded joints represent the most common fatigue crack initiation in steel structures susceptible to fatigue. In India, especially in western offshore, there are about 300 platforms, and 50% of them have reached their design life but still operating due to existing oil and gas reserves. Fatigue prediction in offshore structures is an extremely complicated process involving many factors such as complicated geometry, material, loading, and environment. These uncertainties are modelled as random variables. The assessment of failure probabilities takes a basis to formulate a limit state function for the relevant failure mode and deterioration mechanisms. The fatigue failure assessment based on a simplified probabilistic approach using the application of reliability-based procedures such as the First Order Reliability Method (FORM) is a useful tool. In the simplified fatigue assessment method, the two-parameter Weibull distribution is used to model the long-term distribution of fatigue stresses. Reliability of tubular joint using known fatigue life is an important factor in decision making for life extension of aged platforms. The methodology adopted in this study uses the linear damage accumulation model of Palmgren-Miner, double slope S-N curve, and one-to-one transformation of the probability density functions of long-term stress range and uncertainties to obtain the probability of fatigue failure as a function of the service life from known fatigue life.

An Efficient Algorithm Based on First Order Reliability Method for Fatigue Reliability Analysis of Mechanical Components

2002 ◽  
Author(s):  
Jun Tang ◽  
Young Ho Park
Keyword(s):  
Fatigue Life ◽  
Reliability Analysis ◽  
Search Algorithm ◽  
Strain History ◽  
Fatigue Reliability ◽  
First Order Reliability Method ◽  
Reliability Factor ◽  
First Order ◽  
Reliability Method ◽  
Mechanical Components

The method for fatigue reliability analysis of mechanical components using the First-Order Reliability Method (FORM) reconciles accuracy and efficiency requirements for random process reliability problems under fatigue failure. However, the algorithm for solving FORM is still complex and time consuming. In this paper, the FORM that utilizes an efficient search algorithm is proposed for reliability assessment of the strain-based fatigue life. Using the proposed method, a family of reliability-defined ε-Nf curves, referred to as R-ε-Nf curves, is constructed. An empirical mean stress modified strain-life equation is also used as the performance function. The primary focus of this effort has been the implementation of the new algorithm of FORM to define reliability factors used in modifying the conventional ε-Nf curve to create a family of R-ε-Nf curves, based on the unique reliability factor rule. The proposed method employs the inverse FORM algorithm to achieve computational results, including reliability and the corresponding fatigue life. The method enables the application of fatigue life design for a given cyclic stress and/or strain history. A numerical example is presented to demonstrate the proposed method.

An Efficient Methodology for Fatigue Reliability Analysis of Mechanical Components Based on the Stress-Life Prediction Approach

2003 ◽  
Author(s):  
Jun Tang ◽  
Young Ho Park
Keyword(s):  
Fatigue Life ◽  
Reliability Analysis ◽  
Life Prediction ◽  
Failure Modes ◽  
Theoretical Background ◽  
Fatigue Reliability ◽  
Integrated Method ◽  
Reliability Method ◽  
Mechanical Components ◽  
Prediction Approach

An efficient methodology for fatigue reliability assessment and its corresponding fatigue life prediction of mechanical components using the First-Order Reliability Method (FORM) is developed in this paper. Using the proposed method, a family of reliability defined S-N curves, called R-S-N curves, can be constructed. In exploring the ability to predict spectral fatigue life and assessing the corresponding reliability under a specified dynamics environment, the theoretical background and the algorithm of a simple approach for reliability analysis will first be introduced based on fatigue failure modes of mechanical components. It will then be explained how this integrated method will carry out the spectral fatigue damage and failure reliability analysis. By using this proposed methodology, mechanical component fatigue reliability can be predicted according to different mission requirements.

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