scholarly journals Evaluation of residual stresses in a tube-to-plate welded joint

2019 ◽  
Vol 300 ◽  
pp. 19005 ◽  
Author(s):  
Andrea Chiocca ◽  
Francesco Frendo ◽  
Leonardo Bertini
Keyword(s):  
Residual Stresses ◽  
Numerical Simulations ◽  
Thermal Cycle ◽  
Transient Analysis ◽  
Welded Joint ◽  
Base Material ◽  
Welding Process ◽  
Deep Understanding ◽  
Experimental Tests ◽  
Temperature Dependent

A deep understanding of the manufacturing process is needed in order to achieve safety and quality requirements for parts and components; to this regard, residual stresses play an important role in welded structures. Residual stresses are mainly caused by the extremely severe thermal cycle to which the welded metal and base material are subjected to during welding process and their knowledge leads to a better static and fatigue assessment of welded joints. This work deals with the study of residual stresses for a tube to plate T-joint, made of S355JR carbon steel. The work was carried out by both numerical simulations and experimental tests. The numerical simulations were performed by Ansys FE code through a structural-thermal full transient analysis to evaluate stress, strain and temperature in each node at each step of the simulation. The “birth and death” method was employed, together with temperature-dependent material properties.A2Danda3D simulation were performed, in order to evaluate possible differences due to the welding process. Numerical results were compared to some preliminary measurements obtained through an incremental cut made on the plate.

Thermomechanical Model of Spot Welding for Calculating Residual Stresses

2003 ◽  
Author(s):  
Lijun Xu ◽  
Jamil A. Khan
Keyword(s):  
Residual Stresses ◽  
Heat Generation ◽  
Spot Welding ◽  
Welding Process ◽  
Mechanical Analysis ◽  
Temperature Dependent ◽  
Thermomechanical Model ◽  
Faying Surface ◽  
Proposed Model ◽  
Electrode Interface

A comprehensive axisymmetric model of the coupled thermal-electrical-mechanical analysis predicting weld nugget development and residual stresses for the resistance spot welding process of Al-alloys is developed. The model estimates the heat generation at the faying surface, the workpiece-electrode interface, and the Joule heating of the workpiece and electrode. The phase change due to melting in the weld pool is considered. The contact area and its pressure distribution at both the faying surface and the electrode-workpiece interface are determined from a coupled thermal-mechanical model using a finite element method. The knowledge of the interface pressure provides accurate prediction of the interfacial heat generation. For the numerical model, temperature dependent thermal, electrical and mechanical properties are used. The proposed model can successfidly calculate the nugget diameter and thickness, and predict the residual stresses and the elastic-plastic deformation history. The calculated nugget shape and the deformation of sheets based on the model are compared with the experimental data. The computed residual stresses approach the distribution of experimental measurement of the residual stress.

FEATURES OF REPAIR OF WELDED STRUCTURES OF LARGE THICKNESSES FROM TITANIUM ALLOY VT6ch.

2021 ◽  
pp. 34-43
Author(s):  
A.V. Sviridov ◽  
◽  
М.S. Gribkov ◽  
Keyword(s):  
Titanium Alloy ◽  
Residual Stresses ◽  
Elemental Composition ◽  
Welded Joints ◽  
Mechanical Characteristics ◽  
Electron Beam Welding ◽  
Welded Joint ◽  
Vacuum Annealing ◽  
Base Material ◽  
Welded Structures

The technology of electron-beam welding (EBW) of structures of large thickness made of titanium alloy Ti–6Al–4V has been developed. A complex of metallographic studies of welded samples has been carried out. Tests to determine the mechanical characteristics of repair welded joints, that these joints made by EBW are equal in strength to the base material. The analysis of the level of residual stresses in various parts of the welded joint after repeated repair passes has been carried out. It was found that the subsequent vacuum annealing reduces the level of residual stresses in welded joints to 50 %. The analysis of the elemental composition showed that the elemental composition of the samples from the center of the weld to the base metal practically does not change for welding with the number of repeated passes up to 3.

Application of FIB/SEM/EBSD for Evaluation of Residual Strains and Their Relationship to Weld Metal Hydrogen Assisted Cold Cracking

2012 ◽  
Author(s):  
W. L. Costin ◽  
I. H. Brown ◽  
L. Green ◽  
R. Ghomashchi
Keyword(s):  
Residual Stresses ◽  
Weld Metal ◽  
Base Metal ◽  
Heat Affected Zone ◽  
Ion Beam ◽  
Base Material ◽  
Welding Process ◽  
Cold Cracking ◽  
Predictive Methods ◽  
Residual Strains

Hydrogen assisted cold cracking (HACC) is a welding defect which may occur in the heat affected zone (HAZ) of the base metal or in the weld metal (WM). Initially the appearance of HACC was associated more closely with the HAZ of the base metal. However, recent developments in advanced steel processing have considerably improved the base material quality, thereby causing a shift of HACC to the WM itself. This represents a very serious problem for industry, because most of the predictive methods are intended for prevention of HACC in the HAZ of the base metal, not in the weld metal [1]. HACC in welded components is affected by three main interrelated factors, i.e. a microstructure, hydrogen concentration and stress level [2–4]. In general, residual stresses resulting from the welding process are unavoidable and their presence significantly influences the susceptibility of weld microstructures to cracking, particularly if hydrogen is introduced during welding [5]. Therefore various weldability tests have been developed over the years which are specifically designed to promote HACC by generating critical stress levels in the weld metal region due to special restraint conditions [4, 6–8]. These tests were used to develop predictive methods based on empirical criteria in order to estimate the cracking susceptibility of both the heat-affected zone and weld metal [4]. However, although the relationship between residual stress, hydrogen and HACC has received considerable attention, the interaction of residual stresses and microstructure in particular at microscopic scales is still not well understood [5, 9–21]. Therefore the current paper focuses on the development and assessment of techniques using Focused Ion Beam (FIB), Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction for the determination of local residual strains at (sub) micron scales in E8010 weld metal, used for the root pass of X70 pipeline girth welds, and their relationship to the WM microstructure. The measurement of these strains could be used to evaluate the pre-existing stress magnitudes at certain microstructural features [22].

scholarly journals Effect of Laser Peening with a Microchip Laser on Fatigue Life in Butt-Welded High-Strength Steel

2021 ◽  
Vol 2 (4) ◽  
pp. 878-890
Author(s):  
Tomoharu Kato ◽  
Yoshihiro Sakino ◽  
Yuji Sano
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
High Strength Steel ◽  
Welded Joint ◽  
Base Material ◽  
High Strength ◽  
Microchip Laser ◽  
Laser Peening ◽  
Near Surface ◽  
Compressive Residual Stresses

Laser peening introduces compressive residual stresses on the surfaces of various materials and is effective in enhancing fatigue strength. Using a small microchip laser, with energies of 5, 10, and 15 mJ, the authors applied laser peening to the base material of an HT780 high-strength steel, and confirmed compressive residual stresses in the near-surface layer. Laser peening with a pulse energy of 15 mJ was then applied to fatigue samples of an HT780 butt-welded joint. It was confirmed that laser peening with the microchip laser prolonged the fatigue life of the welded joint samples to the same level as in previous studies with a conventional laser.

Analysis of Welded Joint Under Residual Stresses

2014 ◽  
Author(s):  
H. P. Jawale ◽  
Rahul Singh
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Welded Joint ◽  
Weld Zone ◽  
Welding Process ◽  
Fatigue Behaviour ◽  
Hole Drilling ◽  
Building Structures ◽  
Residual Stress Field ◽  
Stress Relieving

Welded joint is most commonly used for building structures and machine components. Welding process involves heating followed by uneven cooling causing residual stress field. In conjunction with stresses due to external loads, in-service behaviour is affected due to residual stress in welded components. It induces defects, also alters crack initiation life, fatigue behaviour, breaking strength, corrosion resistance and increases the susceptibility of structure to failure by fracture. The residual stress is function of cooling rate and the size of weld. The role of residual stress associated with welding is therefore very important while designing mechanical parts. Conventional methods like heat treatment and shot-peening techniques becomes difficult to be applied for reduction of residual stress in general purpose applications. The work presented in this paper describes the measurement of residual stress using stress relieving method, based on hole-drilling technique. Subsequently, residual stresses are relived and measured using strain rosette near the weld zone. These strains value is converted in to stress value. Residual stress is quantified with respect to yield strength, making it possible to be considered for safe designing of weld components.

Effect of the welding process on microstructure, microhardness and residual stresses of capacitor discharge stud welded joint

2021 ◽  
pp. 1-23
Author(s):  
Qian Zhang ◽  
Bao-Zhu Zhang ◽  
Yun Luo ◽  
Gang Yang ◽  
Hong-xiang Zheng
Keyword(s):  
Residual Stresses ◽  
Weld Joint ◽  
Weld Seam ◽  
Welded Joint ◽  
Weld Zone ◽  
Welding Process ◽  
Capacitor Discharge ◽  
Stud Welding ◽  
Carbon Plate ◽  
Extension Length

Abstract Capacitor discharge (CD) stud welding is a common and fast connection technology. This paper presents an experimental and simulation study of the stud weld joint of copper stud and carbon plate. An optimized stud welding process was proposed based on microstructure, microhardness and residual stresses of CD stud welded joint. The results show that a narrow weld seam with widmanstaten structure were formed because of quickly cooling. For the longer stud extension length, the width of weld zone becomes wider and the microstructure becomes more uniform. As the increase of welding voltage and stud extension length, the microhardness increases then decreases. However, the residual stresses are increased with welding voltage increases, while they are decreased with the increases of stud extension length. The optimized welding voltage and stud extension length should be designed to 90 V and 5 mm, respectively. This study will provide a great significance to the stud welding on site.

scholarly journals Simulation of Multipass Welding With Simultaneous Computation of Material Properties

2000 ◽  
Vol 123 (1) ◽  
pp. 106-111 ◽  
Author(s):  
Lars Bo¨rjesson ◽  
Lars-Erik Lindgren
Keyword(s):  
Residual Stresses ◽  
Microstructure Evolution ◽  
Material Properties ◽  
Base Material ◽  
Steel Plates ◽  
Filler Material ◽  
Temperature History ◽  
Temperature Dependent ◽  
Butt Welding ◽  
Thick Steel

Multipass butt welding of two 0.2 m thick steel plates has been investigated. The objective is to calculate residual stresses and compare them with measured residual stresses. The material properties depend on temperature and temperature history. This dependency is accounted for by computing the microstructure evolution and using this information for computing material properties. This is done by assigning temperature dependent material properties to each phase and applying mixture rules to predict macro material properties. Two different materials have been used for the microstructure calculation, one for the base material and one for the filler material.

High Temperature Fatigue of Welded Joints: Experimental Investigation and Local Analysis of Butt Welded Flat and Cruciform Specimens

2015 ◽  
Author(s):  
Kay Langschwager ◽  
Jürgen Rudolph ◽  
Alfred Scholz ◽  
Matthias Oechsner
Keyword(s):  
Thermal Loading ◽  
Welded Joint ◽  
Effective Strain ◽  
Mechanical Strain ◽  
Load Condition ◽  
Base Material ◽  
Welding Process ◽  
Image Correlation ◽  
Local Analysis ◽  
Weld Material

Austenitic stainless steel of type X6CrNiNb18-10 exhibits advantageous mechanical and chemical properties and is a common material for numerous applications in the nuclear power plant and chemical industries. Besides the mechanical strain induced by high pressure, the fatigue life in welded pipelines is affected by additional thermomechanical strains due to thermal loading. The welding process mainly determines the geometry and metallurgical constitution of the welded joint. Therefore, the butt welds additionally influence the strain gradient along the component and reduce its lifetime. While the base and weld material are similar, they show different softening and hardening behavior, especially at ambient temperature. Cyclic hardening occurs in the base material, whereas cyclic softening can be observed in the weld material. The hardness distribution along the welded joint reveals no clear differentiation of base material, the heat affected zone and weld material. The attributes of the individual materials cannot be transferred to the welded joint automatically. Thus, the analysis of the interaction between the materials along the welded joint is a main topic of this research. To this end, digital image correlation is used for different kinds of specimens and load conditions. The position along the testing area at which fatigue failure occurs depends on the specimen type and the load condition but not on the temperature. Further, isothermal and anisothermal fatigue tests on welded cruciform specimens are presented. The common practice of the effective strain is discussed for the analyzed conditions.

Finite Element Analysis of Residual Stresses in TT-Welded Joint of a Fixed Jacket Platform

2006 ◽  
Author(s):  
Kh. Rostami ◽  
A. R. M. Gharabaghi ◽  
M. R. Chenaghlou ◽  
A. Arablouei
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Thermal Stresses ◽  
Welded Joint ◽  
Welding Process ◽  
Element Analysis ◽  
Welded Steel ◽  
Buckling Strength ◽  
Structural Distortions ◽  
Weld Toe

Welded steel tubular joints are the kind of connections used extensively in the construction of fixed jacket platforms. The welding process creates considerable tensile residual stresses near the toe of TT-joint due to the rapid cooling and contraction of final welding layers. Welding produces thermal stresses that cause structural distortions, which influence the buckling strength of the structure. In this study thermal elasto-plastic analysis is carried out using ANSYS finite element techniques to evaluate the thermo-mechanical behavior and the residual stresses of the TT-joint. Moreover, the technique of element birth and death is employed to simulate the weld filler variation with time in TT-joint. The results show the considerable tensile residual stress near the weld toe that it may cause crack initiation in this region and threats the fatigue life of joint.

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