scholarly journals Study on Life Model of MOV Based on Multiple Parameters and Surge History

2021 ◽  
Author(s):  
RUAN Xiaofei ◽  
Shaoyun JIN ◽  
WEN Weigang ◽  
CHENG Weidong
Keyword(s):  
Life Prediction ◽  
Residual Life ◽  
Cumulative Effect ◽  
Degradation Process ◽  
Life Assessment ◽  
Lightning Protection ◽  
Multiple Parameters ◽  
History Information ◽  
Life Model ◽  
Metal Oxide Varistor

Abstract With the advance of intelligent operation and maintenance in china railways, the requirement of condition monitoring and remaining life prediction for lightning protection equipment has become increasingly urgent. MOV(Metal Oxide Varistor) is the key component of railway surge protector, and it is necessary to study the description model of its degradation process. The output of the model that uses a single parameter to characterize degradation is more prone to contingency, and cannot truly and fully reflect the life state of the MOV. The degradation of MOV is a cumulative effect, and its life model should consider the surge history information. In view of the above problems, a prediction model of the residual life value of MOV is given by combining various degradation related parameters and surge history. Firstly, nine degradation related parameters are fused to construct degradation core. Then, the degradation core and surge history are fused through Markov chain to build a life model of MOV. Then, the model is calibrated with experimental data. Finally, the model is validated and analyzed by experiments. The model can describe the degradation process of MOV more comprehensively and accurately, and can predict the residual life value at the same time, and it has potential application in the life assessment of surge protective devices.

Residual life assessment method for polymethyl methacrylate

2020 ◽  
Vol 16 (4) ◽  
pp. 679-687
Author(s):  
Tao Wei ◽  
Sijin Zhao ◽  
Zongzhan Gao ◽  
Ke Zhang ◽  
Wenxuan Gou ◽  
...  
Keyword(s):  
Linear Relationship ◽  
Polymethyl Methacrylate ◽  
Life Prediction ◽  
Residual Life ◽  
Assessment Method ◽  
Life Assessment ◽  
Key Factors ◽  
Content Type ◽  
Nonlinear Fitting ◽  
The Relationship

PurposeFatigue and creep are the key factors for the failure of polymethyl methacrylate (PMMA) in the engineering structure, so a great of quantity attention is focused on the life prediction under the creep and fatigue conditions. This paper aims to mainly summarize the traditional life assessment method (S–N curve), life assessment method based on crazing density and life assessment method based on transmittance. S–N curve and classical creep curve are introduced on the traditional life assessment method; the variation of the craze density with the logarithm of cyclic numbers is given in different fatigue load. A linear relationship is obtained, and a higher stress leads to a higher slope, suggesting a faster growth of craze. Furthermore, a craze density model is purposed to describe this relationship; the variation of craze density with the time at different creep load is given. The craze density has two obvious stages. At the first stage, craze density ranged from approximately 0.02 to 0.17, and a linear relationship is obtained. In the following stage, a nonlinear relationship appears till specimen rupture, a new creep life model is proposed to depict two stages. The relationship between transmission and time under creep load is shown. With increasing of time, the transmittance shows a nonlinear decrease. Through polynomial nonlinear fitting, a relationship between the transmittance and residual life can be obtained. To provide reference for the life assessment of transparent materials, the paper compares three life assessment methods of PMMA.Design/methodology/approachThis paper uses the traditional life assessment method (S–N curve), life assessment method based on crazing density, life assessment method based on transmittance.FindingsThe variation of the craze density with the logarithm of cyclic numbers is given in different fatigue loads. A linear relationship is obtained, and a higher stress leads to a higher slope, suggesting a faster growth of craze. Furthermore, a craze density model is proposed to describe this relationship, and the variation of craze density with the time at different creep loads is given. The craze density has two obvious stages. The relationship between transmission and time under creep load is shown. With increasing of time, the transmittance shows a nonlinear decrease. Through polynomial nonlinear fitting, a relationship between the transmittance and residual life can be obtained.Originality/valueFatigue and creep are the key factors for the failure of PMMA in the engineering structure, so a great of quantity attention is focused on the life prediction under the conditions of creep and fatigue. This paper mainly summarizes traditional life assessment method (S–N curve), life assessment method based on crazing density and life assessment method based on transmittance.

scholarly journals Fatigue life prediction of mechanical structures under stochastic loading

2018 ◽  
Vol 157 ◽  
pp. 02024 ◽  
Author(s):  
Bohuš Leitner ◽  
Lucia Figuli
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Residual Life ◽  
Steel Structure ◽  
Degradation Process ◽  
Bearing Steel ◽  
Damage Function ◽  
Operating Conditions ◽  
Fatigue Life Prediction ◽  
Load Bearing

Problems of fatigue life prediction of materials and structures are discussed in the paper. Service loading is assumed as a continuous loading process with possible discontinuous events, which are caused by various operating conditions. The damage in a material is due to a cumulative degradation process. The damaging process is then represented either by rain-flow matrices or by a fatigue damage function which is derived using some hypothesis of a fatigue failure criterion. Presented theoretical procedure enables a very effective estimation of a service life and/or reliable evaluation of residual life of any structures under various types of loading and environmental conditions. This approach creates a good basis for powerful expert systems in structural and mechanical engineering. The aim of the paper is to present briefly some results of analysis of load-bearing steel structure loads of special railway crane PKP 25/20i which was utilized in some specific ad relatively hard operating conditions. Virtual models of the structure were being used in an analysis of acting working dynamics loads influence to be able to forecast fatigue life of load-bearing of the crane jib.

Detection of Creep Degradation on Collapsed Membrane Wall From P265GH Pressure Purpose Steel by Ultrasonic Testing

2018 ◽  
Author(s):  
Tomáš Zavadil
Keyword(s):  
Ultrasonic Testing ◽  
Residual Life ◽  
Degradation Process ◽  
Pressure Vessels ◽  
Ultrasonic Waves ◽  
Life Assessment ◽  
Creep Failure ◽  
Thermally Induced ◽  
Residual Life Assessment ◽  
Creep Degradation

Creep failure of the pressure vessels operated at high temperatures in power and petrochemical industry is a frequent reason of its collapse. Some ultrasonic properties, as the ultrasonic waves’ velocity, are sensitive to change of material properties due to thermally induced degradation processes, especially plastic deformation. The article discusses possible applications of ultrasonic testing to detect creep degradation process based on results of measurements performed on collapsed membrane wall from P265GH pressure purpose steel. The methodology may help with selection of potentially critical areas on pressure equipment under operation prior its further investigation while performing e.g. residual life assessment.

Predicting the Residual Life of Plant Equipment—Why Worry?

1985 ◽  
Vol 107 (3) ◽  
pp. 213-217 ◽  
Author(s):  
C. E. Jaske
Keyword(s):  
Life Prediction ◽  
Residual Life ◽  
Life Assessment ◽  
Case Histories ◽  
Life Estimation ◽  
Remaining Service Life ◽  
Critical Issues ◽  
Plant Equipment ◽  
Residual Life Assessment

Predicting the residual life of plant equipment that has been in service for 20 to 30 years or more is a major concern of many industries. This paper reviews the reasons for increased concern for residual-life assessment and the general procedures used in performing such assessments. Some examples and case histories illustrating procedures for assessing remaining service life are discussed. Areas where developments are needed to improve the technology for remaining-life estimation are pointed out. Then, some of the critical issues involved in residual-life assessment are identified. Finally, the future role of residual-life prediction is addressed.

A criterion of crazing density for the residual life assessment of PMMA during creep

2015 ◽  
Vol 11 (4) ◽  
pp. 517-526 ◽  
Author(s):  
Zongzhan Gao ◽  
Qinghai Li ◽  
Yi Wang
Keyword(s):  
Design Methodology ◽  
Room Temperature ◽  
Residual Life ◽  
Life Assessment ◽  
Initiation Time ◽  
Creep Life ◽  
Content Type ◽  
Life Model ◽  
Residual Life Assessment ◽  
New Criterion

Purpose – A series of creep experiments were carried out to study a new criterion for creep residual life assessment of PMMA (MDYB-10) with various stresses level at room temperature. A macroscopical creep life model based on abundant experiments results was researched first. The model included three phases which are described by the Chen theory, Norton formula and exponential expression, respectively. The paper aims to discuss these issues. Design/methodology/approach – During the creep experiments, the simple optical testing instrument was used to observe the crazing initiation and quantify the crazing damage density in the specimens. Findings – It was shown that the initiation time of crazing damage depended on the stress level, and the crazing damage density increased non-linearly with experiment time. The crazing initiation time equation and damage density equations were expressed. Originality/value – Comprehensive consideration of the creep life model and crazing density evolution equation, a new criterion for creep residual life assessment was introduced. The criterion could be applied to assess the residual life for MDYB-10 by measuring the crazing damage density.

Sign in / Sign up

Export Citation Format

Share Document