scholarly journals Review of Fatigue Assessment Methods for Welded Steel Structures

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Boris Fuštar ◽  
Ivan Lukačević ◽  
Darko Dujmović
Keyword(s):  
Welded Joints ◽  
Fatigue Crack Initiation ◽  
High Stress ◽  
Steel Structures ◽  
Assessment Methods ◽  
Stress Concentrations ◽  
Additional Material ◽  
Welded Steel ◽  
Fatigue Assessment ◽  
Steel Joints

Due to high stress concentrations, welded joints represent the most common locations of fatigue crack initiation in steel structures that are prone to fatigue. Welding affects material properties by the process of heating, cooling, and combining basic and additional material. Since welding is the primary process of joining elements in steel structures, it is obvious that fatigue assessment during the design and maintenance process becomes inevitable. There are many fatigue assessment methods of welded joints, but their precision remains questionable. This paper represents a review of the most common fatigue assessment methods used for welded steel joints. As a result of this review, areas that require additional research are highlighted.

scholarly journals The peak stress method applied to the fatigue assessment of tube-tube steel joints with weld ends under multiaxial loadings

2019 ◽  
Vol 300 ◽  
pp. 19001
Author(s):  
Giovanni Meneghetti ◽  
Alberto Campagnolo ◽  
Michael Vormwald ◽  
Ehsan Shams
Keyword(s):  
Fatigue Strength ◽  
Welded Joints ◽  
Fatigue Crack Initiation ◽  
Peak Stress ◽  
Multiaxial Fatigue ◽  
Tube Steel ◽  
Fe Model ◽  
Present Contribution ◽  
Fatigue Assessment ◽  
Steel Joints

The Peak Stress Method (PSM) is an approximate, FE-oriented application of the notch stress intensity factor (NSIF) approach to fatigue design of welded joints, which is based on the singular linear elastic peak stresses calculated from FE analyses performed by using coarse mesh patterns. By adopting the averaged strain energy density (SED) as a fatigue strength criterion, a design stress (the equivalent peak stress) can be defined; in conjunction with a reference design curve previously defined, the fatigue strength assessment of welded joints subjected to multiaxial fatigue loadings can be performed. In the present contribution, the PSM has been applied to the fatigue assessment of tube-tube steel joints with weld ends, which have been fatigue tested in a previous contribution under combined loadings: namely pure axial, pure torsion and in-phase as well as out-of-phase axial-torsion loadings, all of which with two load ratios, i.e. R = 0 and R = -1. The experimental fatigue results have been re-converted in terms of equivalent peak stress by adopting a 3D FE model including an idealised weld end geometry. The equivalent peak stress has proved to assess the fatigue crack initiation location in agreement with experimental observations, moreover a quite good agreement has been obtained between the experimental results and the PSM-based design scatter band.

Thickness Effect Criterion for Fatigue Strength Evaluation of Welded Steel Structures

1993 ◽  
Vol 115 (1) ◽  
pp. 58-65 ◽  
Author(s):  
J. Yagi ◽  
S. Machida ◽  
M. Matoba ◽  
Y. Tomita ◽  
I. Soya
Keyword(s):  
Welded Joints ◽  
Steel Structures ◽  
Point Of View ◽  
Thickness Effect ◽  
Welded Steel ◽  
Cruciform Joints ◽  
Loading Mode ◽  
Heavy Section ◽  
Weld Profile ◽  
Steel Joints

From a practical point of view, some measures to reduce the thickness effect backed by a reasonable criterion are required for fabricating structures with heavy section plates. In this study, the thickness effect was investigated by systematic experiments on welded steel joints with thicknesses ranging from 10 to 80 mm. Cruciform joints and T-joints with improved weld by overall profiling or toe-grinding were tested under pulsating tension and under pulsating bending, respectively. These experimental results were analyzed together with the previous results of as-welded joints. As a result, it was concluded that the thickness effect exponents for various conditions may be classified into three categories according to the combination of joint type and loading mode. As-welded joints under bending stress have the steepest thickness effect exponent of −1/3, while as-welded joints under tension with an exponent of −1/5 is milder in thickness effect than that specified in the existing codes. If the weld profile is improved by grinding, the thickness effect becomes much milder to an exponent of −1/10. The as-weld joints with constant-sized attachments also have an exponent of −1/10. Furthermore, thickness effect dependence on fatigue life and thickness effect under random stress were investigated. Based on these results, this study proposes a new evaluation criterion for design purposes.

Fatigue Behaviour of Friction Stir Welded Steel Joints

2014 ◽  
Vol 891-892 ◽  
pp. 1488-1493 ◽  
Author(s):  
José Azevedo ◽  
Virgínia Infante ◽  
Luisa Quintino ◽  
Jorge dos Santos
Keyword(s):  
Base Material ◽  
Welding Process ◽  
Steel Structures ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Welded Steel ◽  
Shipbuilding Industry ◽  
Friction Stir ◽  
Steel Joints

The development and application of friction stir welding (FSW) technology in steel structures in the shipbuilding industry provide an effective tool of achieving superior joint integrity especially where reliability and damage tolerance are of major concerns. Since the shipbuilding components are inevitably subjected to dynamic or cyclic stresses in services, the fatigue properties of the friction stir welded joints must be properly evaluated to ensure the safety and longevity. This research intends to fulfill a clear knowledge gap that exists nowadays and, as such, it is dedicated to the study of welded steel shipbuilding joints in GL-A36 steel, with 4 mm thick. The fatigue resistance of base material and four plates in as-welded condition (using several different parameters, tools and pre-welding conditions) were investigated. The joints culminate globally with defect-free welds, from which tensile, microhardness, and fatigue analyses were performed. The fatigue tests were carried out with a constant amplitude loading, a stress ratio of R=0.1 and frequency between 100 and 120 Hz. The experimental results show the quality of the welding process applied to steel GL-A36 which is reflected in the mechanical properties of joints tested.

scholarly journals Capturing and Micromechanical Analysis of the Crack-Branching Behavior in Welded Joints

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1308
Author(s):  
Wenjie Wang ◽  
Jie Yang ◽  
Haofeng Chen ◽  
Qianyu Yang
Keyword(s):  
Crack Propagation ◽  
Welded Joints ◽  
High Stress ◽  
High Strength ◽  
Crack Branching ◽  
Stress Concentrations ◽  
Ductile Materials ◽  
Pulling Forces ◽  
Crack Propagation Process ◽  
Combined Action

During the crack propagation process, the crack-branching behavior makes fracture more unpredictable. However, compared with the crack-branching behavior that occurs in brittle materials or ductile materials under dynamic loading, the branching behavior has been rarely reported in welded joints under quasi-static loading. Understanding the branching criterion or the mechanism governing the bifurcation of a crack in welded joints is still a challenge. In this work, three kinds of crack-branching models that reflect simplified welded joints were designed, and the aim of the present paper is to find and capture the crack-branching behavior in welded joints and to shed light on its branching mechanism. The results show that as long as there is another large enough propagation trend that is different from the original crack propagation direction, then crack-branching behavior occurs. A high strength mismatch that is induced by both the mechanical properties and dimensions of different regions is the key of crack branching in welded joints. Each crack branching is accompanied by three local high stress concentrations at the crack tip. Three pulling forces that are created by the three local high stress concentrations pull the crack, which propagates along with the directions of stress concentrations. Under the combined action of the three pulling forces, crack branching occurs, and two new cracks initiate from the middle of the pulling forces.

Investigation of ductile fracture behavior of lap-welded joints with 460 MPa steel

2017 ◽  
Vol 21 (9) ◽  
pp. 1376-1387 ◽  
Author(s):  
Gang Shi ◽  
Yufeng Chen
Keyword(s):  
Ductile Fracture ◽  
Welded Joints ◽  
High Strength Steel ◽  
Fracture Behavior ◽  
Steel Structures ◽  
High Strength ◽  
Welded Steel ◽  
Fracture Parameters ◽  
Tension Tests ◽  
Micromechanics Models

Fractures in welded connections usually occurred at Earthquake. The lap-welded joints are an important type of welded connections in high strength steel structures. In this article, the ductile fracture behavior of lap-welded joints has been studied experimentally and numerically with 460 MPa steel. A series of coupon tests were used to determine two corresponding weld materials (ER55-D2 and ER55-G) mechanical properties. Two micromechanics models (void growth model and stress-modified critical strain models) had been calibrated by circumferentially notched tension specimens and calculated the fracture parameters numerically, which had been applied in predicting in five lap-welded joints. The experimental study showed that the fracture mode of 460 MPa lap-welded joints exhibited plastic damage under the tension tests. Numerical analysis of the fracture parameters also showed that the ductile fracture behavior of lap-welded joint with ER55-G was better. The study establishes an accurate numerical model for analyzing the ductile fracture behavior of Q460 high strength steel lap-welded joints that is applicable in predicting the fracture failure of welded steel structures.

Use of a Reductive Carbon Monoxide Atmosphere in Arc Welding of Microalloyed Steels

2019 ◽  
Vol 945 ◽  
pp. 543-548 ◽  
Author(s):  
E.A. Ivanaysky ◽  
A.V. Ishkov ◽  
A.A. Ivanaysky
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Welded Joints ◽  
Arc Welding ◽  
Microalloyed Steels ◽  
Metallographic Analysis ◽  
Welded Steel ◽  
Reducing Atmosphere ◽  
Oxidative Processes ◽  
Steel Joints

The possibility of making welded steel joints using arc welding in a reducing medium of carbon monoxide was studied. A method was proposed to eliminate its negative biological effect by heating the feed gas above its flash point, followed by oxidation till carbon dioxide was obtained. Welding modes have been selected to ensure the formation of a quality welded joint. Comparative studies of welded joints obtained using an oxidizing atmosphere of carbon dioxide and a reducing atmosphere of carbon monoxide were carried out. A chemical and metallographic analysis of welded joints was performed. The thermodynamic substantiation of chemical reactions in which carbon and microalloying additives can participate was presented. It was established that the main difference between the proposed welding method and those used at present was the suppression of oxidative processes in liquid metal due to the presence of a reducing atmosphere.

scholarly journals New And Existing Bridge Constructions - Increase of Fatigue Strength of Welded Joints by High Frequency Mechanical Impact Treatment

2013 ◽  
Vol 2 (1) ◽  
pp. 88-101
Author(s):  
Thomas Ummenhofer ◽  
Philipp Weidner ◽  
Tim Zinke
Keyword(s):  
Fatigue Strength ◽  
Welded Joints ◽  
High Frequency ◽  
Research Work ◽  
Steel Structures ◽  
Current Status ◽  
Small Scale ◽  
Welded Steel ◽  
Mechanical Impact ◽  
Existing Structures

Abstract Numerous studies at KIT prove that high frequency mechanical impact (HFMI) treatment is an efficient method for increasing the fatigue strength of welded steel structures. Within different research projects it was found that HFMI-methods can be used successfully for new and existing structures in order to extend the fatigue life. This paper gives an overview of the current status of existing steel bridges in Germany regarding aspects like bridge age distributions and traffic loads. Based on that overview welded joints susceptible to fatigue failure are identified. Using component-like small scale specimens, HFMI-methods were investigated within the objective of implementing an effective application for new and existing structures. Applying the fatigue test data observed, existing design proposals are evaluated and design recommendations for HFMI-treated joints are given. As a result of the research work, a transfer into practice has been realized and different applications are illustrated using the example of bridge constructions made of steel.

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