scholarly journals Influence of Weld Parameters on the Fatigue Life of Deck-Rib Welding Details in Orthotropic Steel Decks Based on the Improved Stress Integration Approach

2019 ◽  
Vol 9 (18) ◽  
pp. 3917 ◽  
Author(s):  
Baoya Cao ◽  
Youliang Ding ◽  
Zhao Fang ◽  
Fangfang Geng ◽  
Yongsheng Song
Keyword(s):  
Fatigue Life ◽  
Mesh Size ◽  
Structural Stress ◽  
Partial Penetration ◽  
Full Penetration ◽  
Integration Approach ◽  
Treatment Type ◽  
Manufacturing Errors ◽  
Stress Integration ◽  
Orthotropic Steel Decks

Fatigue cracks in orthotropic steel decks (OSDs) have been a serious problem of steel bridges for a long time. The structural stress approach is an important approach for fatigue life evaluation of welded structures. Firstly, two parameters and the mesh sensitivity of the stress-based integration equivalent structural stress approach (stress integration approach for short) are analyzed in this paper. Then, the applicability of the master S-N curve is verified based on experimental data of the deck-rib welding details in OSDs. Finally, the multi-scale finite element model (FEM) of Jiangyin Bridge is established, and the bridge fatigue life calculation steps based on the stress integration approach are given. The influence of the slope of the master S-N curve at high cycles on the bridge fatigue life is discussed. Further, the weld parameter influences on the bridge fatigue life are analyzed, as including the following: (1) The determination of the influence of the weld size changes caused by weld manufacturing errors on the bridge fatigue life; (2) the proposal of a new grinding treatment type, and the analysis of influence of the grinding radius on fatigue life; and (3) a comparison of the fatigue life of the deck-rib welding details under 80% partial penetration and 100% full penetration. The results show that the structural stress calculated by the stress integration approach does not change significantly with the parameters of the isolation body width w and the distance δ between the crack propagation surface and the reference surface. To simplify the calculation, δ is set as 0, and w can be set as the mesh size along the weld length direction. The mesh size of the stress integration approach is recommended as 0.25 times the deck thickness. The slope of the master S-N curve at high cycles significantly affects the bridge fatigue life, and a slope of 5 is reasonable. The weld parameter studies for the deck-rib welding details in the OSD of Jiangyin Bridge show that the change of weld size caused by manufacturing errors can obviously affect the bridge fatigue life, and the fatigue life of five different weld types varies from 51 years to 113 years. The new grinding treatment type, without weakening the deck, is beneficial to improving the bridge fatigue life. The fatigue life increases by approximately 5% with an increase of the grinding radius of 2 mm. The fatigue life of 80% partial penetration is slightly higher than that of 100% full penetration.

Structural Stress Based Fatigue Life Evaluation for Heat Exchanger Motor Operated Valve

2006 ◽  
Vol 110 ◽  
pp. 39-44
Author(s):  
Yoon Suk Chang ◽  
H.K. Kim ◽  
Jae Boong Choi ◽  
Young Jin Kim
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Heat Exchanger ◽  
Mesh Size ◽  
Structural Stress ◽  
New Approach ◽  
Life Evaluation ◽  
Local Stresses ◽  
Fatigue Life Evaluation ◽  
Structural Stresses

In ASME Sec. III ‘design by analysis’ approach, stresses are generally calculated by finite element method and compared to corresponding stress limits after categorizing those components. However, in order to obtain optimum results, time consuming and expensive manipulations are required owing to its mesh size dependency and complicate stress categorization. In this paper, a new approach based on structural stress is proposed to resolve the issues and applied to a heat exchanger motor operated valve. At first, the technical bases and specific features of structural stress approach are briefly discussed. Secondly a series of finite element analyses are carried out to show the limitations of current ASME approaches and to get basic data for the proposed approach. Finally, a structural stress concentration factor of motor operated valve is determined after comparison of local stresses and structural stresses, and utilized for fatigue life evaluation. Since the results show a promising applicability, it seems that the structural stress based approach can be utilized for fatigue life evaluation of components with complex geometries.

Development of a High Cycle Fatigue Life Prediction Model for Thin Film Silicon Structures

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Chia-Cheng Chang ◽  
Sheng-Da Lin ◽  
Kuo-Ning Chiang
Keyword(s):  
Thin Film ◽  
Fatigue Life ◽  
Life Prediction ◽  
Microelectromechanical Systems ◽  
Fatigue Testing ◽  
Mesh Size ◽  
Prediction Equation ◽  
Frequency Effect ◽  
Element Analysis ◽  
Solution Type

The fatigue characteristics of microelectromechanical systems (MEMS) material, such as silicon or polysilicon, have become very important. Many studies have focused on this topic, but none have defined a good methodology for extracting the applied stress and predicting fatigue life accurately. In this study, a methodology was developed for the life prediction of a polysilicon microstructure under bending tests. Based on the fatigue experiments conducted by Hocheng et al. (2008, “Various Fatigue Testing of Polycrystalline Silicon Microcantilever Beam in Bending,” Jpn. J. Appl. Phys., 47, pp. 5256–5261) and (Hung and Hocheng, 2012, “Frequency Effects and Life Prediction of Polysilicon Microcantilever Beams in Bending Fatigue,” J. Micro/Nanolithogr., MEMS MOEMS, 11, p. 021206), cantilever beams with different dimensions were remodeled with mesh control technology using finite element analysis (FEA) software to extract the stress magnitude. The mesh size, anchor boundary, loading boundary, critical stress definition, and solution type were well modified to obtain more correct stress values. Based on the new stress data extracted from the modified models, the optimized stress-number of life curve (S–N curve) was obtained, and the new life-prediction equation was found to be referable for polysilicon thin film life prediction under bending loads. After comparing the literature and confirming the new models, the frequency effect was observed only for the force control type and not for the displacement control type.

STRUCTURAL STRESS METHOD FOR FATIGUE DESIGN OF CONCRETE FILLED STEEL TUBULAR T-JOINTS UNDER AXIAL LOADING

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Idris A. Musa
Keyword(s):  
Fatigue Life ◽  
Three Dimensional ◽  
Axial Loading ◽  
Fe Model ◽  
Structural Stress ◽  
Stress Concentrations ◽  
Engineering Structures ◽  
T Joints ◽  
Tubular Joints ◽  
Concrete Filling

Steel tubular structural members are being widely used in various engineering structures. The steel tubular joints will have fatigue problem when subjected to repetitive loading. Fatigue strength is one of the key factors that control the design of steel tubular joints in structures subjected to frequent loading. Research has shown that concrete filling of the steel tubes can effectively reduce stress concentrations at the joint. In this study, the structural stress method which involves the through-thickness stress distribution, has been employed to estimate the fatigue life of concrete filled steel tubular (CFST) T-joints under axial loading in the brace. A Finite Element (FE) model has been developed using ABAQUS. The three-dimensional 8-node hexahedral element has been employed in the FE model. The structural stresses have been extracted and the fatigue life of the joint has been estimated. The results have been verified using experimental results reported in the literature. The current study showed that the structural stress method can effectively predict reliable fatigue life in concrete filled steel tubular (CFST) T-joints.

Outline of the Recent Consolidated Revision of EN13445-3, Clause 18 and Related Annexes: Detailed Assessment of Fatigue Life

2019 ◽  
Author(s):  
Jürgen Rudolph ◽  
Guy Baylac ◽  
Ralf Trieglaff ◽  
Rüdiger Gawlick ◽  
Michael Krämer ◽  
...  
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Assessment Method ◽  
Structural Stress ◽  
Critical Plane ◽  
Fatigue Assessment ◽  
European Working ◽  
Critical Plane Approach ◽  
Detailed Assessment

Abstract The European Pressure Vessel Standard EN 13445 (harmonized Standard acc. to PED 2014/68/EU) provides in its Part 3 (Design) a simplified method for fatigue assessment (Clause 17) and a detailed method of fatigue assessment (Clause 18). While the new revision of Clause 17 has already been adopted, Clause 18 “Detailed Assessment of Fatigue Life” is now available as a consolidated revision in inquiry phase. This major and comprehensive revision has been developed within the framework of the European working group CEN/TC 54/WG 53 – Design methods and constitutes a crucial step towards a modern and user-friendly engineering fatigue assessment method. The overall structure and amendments of Clause 18 are to be presented. All these amendments aim at a significant increase in user friendliness and clear guidelines for application. The following items are to be mentioned in that context: • Fatigue assessment of welded components based on structural stress and structural hot-spot stress approaches, • Detailed guidelines for determining relevant stresses and stress ranges, • Cycle counting proposals in the context of the fatigue assessment method including a critical plane approach. The fatigue assessment of welded components is separated from the fatigue assessment of un-welded parts as it has already been done in previous versions with respective methodological differences. Stress analyses for clause 18 are usually based on detailed finite element analyses (FEA). As an essential amendment for the user, the determination of structural stress ranges for the fatigue assessment of welds is further detailed in a new appropriate annex. Different applicable methods for the determination of structural stresses are explained in connection with the requirements of the finite element models and analyses. The cycle counting issue is comprehensively treated in the context of different design and operation situations (design transients, operational stress-time-histories). The description is detailed towards a critical plane approach. Detailed proposals for implementation in an algorithmic programming framework are given making the described methods ready to use.

Prediction of Low Cycle Fatigue Life Using Cycles Jumping Integration Scheme

2015 ◽  
Vol 784 ◽  
pp. 308-316 ◽  
Author(s):  
Carl Labergere ◽  
Khemais Saanouni ◽  
Zhi Dan Sun ◽  
Mohamed Ali Dhifallah ◽  
Yisa Li ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Mesh Size ◽  
Loading Path ◽  
Integration Scheme ◽  
Model Parameters ◽  
Cycle Fatigue ◽  
316L Steel ◽  
Fully Coupled ◽  
Full Loading

In this paper, cycles jumping scheme integration is used to numerically integrate fully coupled constitutive equations in order to predict the low cycle fatigue life under cyclic loading. This procedure avoids the calculation of the full loading cycles (some millions of loading cycles) while considering the transient stages due to the hardening (at the beginning) and the high damage-induced softening during the last tens of loading cycles. The model parameters have been identified using the results obtained from a 316L steel cylindrical specimen subject to symmetric tension-compression loading path. The effects of the specimen size as well as the mesh size on the fatigue life prediction are investigated.

Evaluation of the Influence of a Planned Interference Fit on the Expected Fatigue Life of a Conjugate Cam Mechanism- A Case Study

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Pau Català ◽  
Maria Antònia De los Santos ◽  
Joaquim M. Veciana ◽  
Salvador Cardona
Keyword(s):  
Fatigue Life ◽  
Dynamic Model ◽  
Contact Forces ◽  
Surface Finishing ◽  
Automatic Process ◽  
Interference Fit ◽  
Cam Mechanism ◽  
Experimental Apparatus ◽  
Manufacturing Errors ◽  
Lubrication Conditions

Due to dynamic effects, clearances, manufacturing and assembly errors in form-closed cam mechanisms, the follower jump can also occur. For conjugate cam mechanisms a technique to avoid the follower jump without the use of a spring involves making the conjugate cam profiles bigger than the kinematical ones by adding an external offset. This strategy produces an interference fit between the conjugate cam profiles and the follower train. This paper presents an ordered procedure to study the influence that the planned interference fit has on the evaluation of the contact forces, the expected fatigue life of the rollers, contact pressures and the lubrication conditions. The study is based on a conjugate cam mechanism with translational roller followers used in a real automatic process for manufacturing muselets. A three-degree-of-freedom dynamic model is proposed and the Hertzian theory for general profiles is used to model the nonlinear contact stiffness between the cams and the crowned rollers. The dynamic model predicts that it is difficult to obtain conjugate cam mechanisms with an infinite expected fatigue life of the rollers just by considering typical achievable manufacturing errors or clearances, and as happens in reality, a set-up process is highly recommended. The procedure is also tested with measured manufacturing errors on a coordinate measure machine—CMM—and with measured radial internal clearances for the rollers measured by an experimental apparatus. Also, to evaluate lubrication conditions, surface finishing measurements have been taken of the cams and the rollers with a surface profiler.

The Finite Element Research of Fatigue Properties of Steel Q345 Butt Welded Joint

2014 ◽  
Vol 670-671 ◽  
pp. 1087-1090
Author(s):  
Wei Ping Ouyang ◽  
Liang Sheng Chen ◽  
Xiu Dong Xu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Life ◽  
Stress Distribution ◽  
Welded Joint ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Structural Stress ◽  
Design Development ◽  
Stress Theory

The research of fatigue properties of the butt welded joint, though a large number of fatigue tests are need to be carried out, has significant influence to hoisting equipment’s design, development and using safety. This paper conducted a study on simulating the fatigue properties of widely used steel Q345 butt welded joint’s by finite element method based on the improved linear equivalent structural stress theory. The originally massive amount of fatigue tests and data processing could be saved. In order to ensure the accuracy of the fatigue modeling, a batch of Q345 butt welded joints were prepared for the fatigue tests which is used to contrast with the modeling result. The stress distribution under different load situation and the fatigue life of the joints, which have profound reference significance to hoisting machinery industry, can be acquired through modeling.

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