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.

Fatigue Life Assessment of Boiler Components Under Cyclic Operating Conditions

2006 ◽  
Author(s):  
Jinhua Shi ◽  
William Bell ◽  
Alan M. Laird
Keyword(s):  
Fatigue Life ◽  
Cold Start ◽  
Assessment Method ◽  
Operating Conditions ◽  
Life Assessment ◽  
Steam Generators ◽  
Fatigue Life Assessment ◽  
Cyclic Operation ◽  
Start Up ◽  
High Temperature Components

A fatigue life assessment application has been implemented using the methodology given in the European Standard EN 12952-3. The assessment application can use data from the Distributed Control System (DCS) of the plant or, to improve accuracy, use component metal temperatures if thermocouples have been fitted across the component of interest. Fatigue assessments have been carried out on typical high temperature components in Heat Recovery Steam Generators (HRSGs) and a large coal fired boiler which were subject to cyclic operation. The assessments carried out used recorded plant operating DCS and thermocouple data and examined main cyclic events, e.g. shutdown/cold start-up cycle, etc. Detailed finite element analyses have also been conducted on a typical superheater header using as input the plant operating data. Calculated fatigue damage levels for both methods are compared and it is shown that comparable values are obtained. In addition, further assessment has been performed on a component where the period of operation included several shutdown/cold start cycles and many sub-cycles. On completion of the above studies, Mitsui Babcock have implemented the fatigue assessment method into a simple plant life monitoring system.

Reference Stress Based Assessment for Creep-Fatigue Life Under Multiaxial Condition

2014 ◽  
Author(s):  
Kenji Tokuda ◽  
Kimiaki Yoshida ◽  
Masataka Yatomi
Keyword(s):  
Fatigue Life ◽  
Creep Condition ◽  
Assessment Method ◽  
Life Assessment ◽  
Finite Element Analyses ◽  
Reference Stress ◽  
Creep Fatigue ◽  
Creep Fatigue Crack ◽  
Novel Model ◽  
Good Agreement

The reference stress method has been developed to assess the service life for many components under creep condition. However, in order to use the reference stress as a representative stress to assess the creep fatigue life, some modifications are needed. The σd approach based on reference stress, used in RCC-MR, is one of the most common method to assess creep fatigue crack incubation. The aim of this paper is to develop a novel model based on reference stress and the σd approach to estimate the life subjected to creep-fatigue interaction under multiaxial condition for defect free structures. Three kinds of circumferentially notched bar specimens were used in order to examine the creep-fatigue interaction under multiaxial conditions. Finite element analyses were conducted to develop a simplified life assessment method and to calculate the creep fatigue damage in the test specimens. The predicted creep fatigue lives are in good agreement with the experimental results using notched bar specimens of 316H stainless steel.

scholarly journals Fatigue Life Assessment Method for Prestressed Concrete Sleepers

2017 ◽  
Vol 3 ◽  
Author(s):  
Ruilin You ◽  
Dan Li ◽  
Chayut Ngamkhanong ◽  
Rims Janeliukstis ◽  
Sakdirat Kaewunruen
Keyword(s):  
Fatigue Life ◽  
Prestressed Concrete ◽  
Assessment Method ◽  
Life Assessment ◽  
Fatigue Life Assessment

Multiaxial Fatigue Life Assessment Method Based on the Mean Value of Modified Second Invariant of the Deviatoric Stress

2014 ◽  
Vol 224 ◽  
pp. 15-20
Author(s):  
Łukasz Pejkowski ◽  
Dariusz Skibicki
Keyword(s):  
Fatigue Life ◽  
Hydrostatic Stress ◽  
Assessment Method ◽  
Mean Value ◽  
Multiaxial Fatigue ◽  
Deviatoric Stress ◽  
Life Assessment ◽  
Fatigue Life Assessment ◽  
Fatigue Life Estimation ◽  
The Mean

Stress invariants approach to the multiaxial fatigue life estimation is generally based on the root mean square value of second invariant of the deviatoric stress amplitude and the value of hydrostatic stress. Such an approach omits a significant part of the information about multiaxial load history. It is particularly noticeable in case of non-proportional loadings, which lead to a reduction of fatigue life (i.e. [1–3]). In this work a new method based on the mean value of modified second invariant of the deviatoric stress has been presented.

A Study on the Fatigue Life Assessment for Urban EMU Structure

2007 ◽  
Vol 345-346 ◽  
pp. 283-286
Author(s):  
Jong Duk Chung ◽  
Jang Sik Pyun ◽  
Ouk Sub Lee
Keyword(s):  
Fatigue Life ◽  
Endurance Limit ◽  
Assessment Method ◽  
Cumulative Damage ◽  
Life Assessment ◽  
Random Load ◽  
Urban Transit ◽  
Fatigue Assessment ◽  
Fatigue Life Assessment ◽  
Approach Method

In these days, most urban railway vehicles have been serviced under the random load application. However, it is considered to be a major factor of safety to predict the fatigue life for structures. It is thus required that fatigue assessment method for cumulative damage approach while Korea domestic regulations practices only the only has endurance limit approach. With this endurance limit approach, fatigue life prediction is impossible. In this research, the fatigue assessment for urban transit structure by using of cumulative damage approach method and related theories are presented.

Life Assessment of a Coke Drum by Using the Thermal-Mechanical Fatigue Properties and Laser Scanning Approach

2020 ◽  
Author(s):  
Zhiyuan Han ◽  
Guoshan Xie ◽  
Zengchao Wang ◽  
Jianzhong Yin ◽  
Jin Shi
Keyword(s):  
Fatigue Life ◽  
Laser Scanning ◽  
Low Cycle Fatigue ◽  
Complex Loading ◽  
Operating Conditions ◽  
Life Assessment ◽  
Fatigue Properties ◽  
Element Analysis ◽  
Thermal Mechanical Fatigue ◽  
Mechanical Fatigue

Abstract Coke drums are critical equipments in delayed coking plants, which are operated under severe thermal-mechanical conditions by cyclic heating and quenching processes. Cracks are usually developed during service because of severe plastic deformation and low-cycle fatigue. Thus, the assessment of the deformation severity and remaining life is important for safety operating of the coke drums. This study investigated the bulging damage and fatigue life of 6 coke drums after 16 years and 22 years of service in China. A thermal-mechanical fatigue test were first performed to simulate complex loading condition experienced by the coke drum. The thermal-mechanical fatigue life curve of the fabrication material was obtained. Then, a internal laser scanning was employed to measure the deformation and bulges of drum shells. The finite element analysis was developed to calculate the cyclic stress and strain and bulging severity based on the laser mapping and operating conditions. The fatigue life of the coke drum was assessed by the Coffin-Manson-Basquin’s relationship. The life evaluation results of different methods were compared and analyzed. The results showed that a reasonable life of the coke drum can be obtained by using the thermal-mechanical fatigue properties and laser scanning approach.

Fractional Modeling Approach of Course Evaluation

2011 ◽  
Vol 219-220 ◽  
pp. 130-134
Author(s):  
Chun Na Zhao ◽  
Min Hua Wu ◽  
Yu Zhao ◽  
Ying Shun Li ◽  
Li Ming Luo
Keyword(s):  
Fractional Order ◽  
Evaluation Model ◽  
Course Evaluation ◽  
Model Parameters ◽  
Fractional Order Systems ◽  
Proposed Model ◽  
Fractional Modeling ◽  
Information Engineering ◽  
Normal University ◽  
Evaluation Work

Course evaluation is necessary means to ensure the improvement of course construction level. A new course evaluation model is proposed based on the fractional order systems in this paper. An algorithm for linear fractional order systems founded on Grunwald–Letnikov’s fractional calculus definition is described. The fractional evaluation model is composed of fractional order and common coefficient. Model parameters can be determined by a large number of data and mathematical statistics method. The proposed model was applied to actual course evaluation work of Capital Normal University Information Engineering College. The practicability and effectiveness of the method have been validated.

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