Stresses In Welded Joints Research Articles

Accuracy improvement of X-ray residual stress measurement in welds of Ni based alloy by two-dimensional detector with multiaxial rocking

In materials such as Ni based alloys, the microstructures are formed by monophase solidification without solid state transformation. It is difficult to obtain the welding residual stress by X-ray diffraction because of the preferred orientation of the unidirectional solidification and the grain growth in the heat affected zone. To exclude their effect, a method that records the diffraction peaks in a two-dimensional detector combined with multiaxial rocking is proposed. It is clarified that the equilibrium of shrinkage and the recovery of strain during the thermal cycle determines the site of the maximum tensile stress. In addition, dynamic recrystallisation, which occurs during welding, contributes to the decreased residual stress at the fusion line. If the spatial resolution of the proposed and the conventional measurement methods can be correlated, the results of each method agree well. Therefore, the proposed method is an effective tool for measuring the residual stress in welded joints of Ni based alloy.

Accuracy Improvement of X-Ray Stress Measurement on GTA Weld of Type 600 Ni Based Alloy

In materials such as Ni-based alloys, the microstructures are formed by mono-phase solidification without solid-state transformation. Measuring the welding residual stress by X-ray diffraction is difficult because of the preferred orientation of the unidirectional solidification and the grain growth in the heat-affected zone. To exclude these effects, a method that records the diffraction peaks in a two-dimensional detector combined with multi-axial rocking is proposed. It is clarified that the equilibrium of shrinkage and the recovery of strain during the thermal cycle determines the site of the maximum tensile stress. In addition, dynamic re-crystallization, which occurs during solidification, contributes to the decreased residual stress at the fusion line. If the spatial resolution of the proposed and the conventional measurement methods can be correlated, the results of each method agree well. Therefore, the proposed method is an effective tool for measuring the residual stress in welded joints of Ni-based alloy.

Bucket wheel failure caused by residual stresses in welded joints

Cracks in the welded joints on the bucket wheel (BW) body of the bucket wheel excavator (BWE) SRs 1300 were discovered after merely 1800 h of operation. Investigations are carried out in order to detect the causes of cracks occurrence and thus prevent possible heavy damages to the machine. Working stresses in the BW body are defined by using FEM. Methods of strain gauges are used for the experimental stress analysis in real working conditions. Measurements of welding residual stresses are carried out by applying the centre hole drilling method. Additionally, experimental investigations defined the chemical composition, tensile properties, hardness, impact toughness, as well as the susceptibility to cracking (measurement of residual hydrogen, FISCO, Tekken and CTS methods). External loads induced by the resistance-to-excavation are determined by following a model that encompasses all relevant structural parameters and also the BWE duty cycle parameters. By using FEM, it was identified that the maximum values of equivalent stress in the zones of cracks occurrence are lower than the allowable values. This conclusion is confirmed by measurements. The measured values of welding residual stresses reach the value of yield strength in critical zones. Non-compliances during grooving (clearance in the root is substantially larger than the prescribed one) caused large filler material deposition and heat input. Such welded joints are susceptible to cold cracking. Based on the results of the numerical–experimental analysis, findings show that in critical zones the combination of working (dynamic) and residual (static) stress can be above the limit lines of modified Goodman’s diagrams i.e. that the fatigue safety of the BW body structure was insufficient.

Specific features of the stressed state and estimation of the lifetime of stamped-and-welded elbows used in hot reheat steam lines of 500-MW power units

Results obtained from calculations of the stressed and strained state of stamped-and-welded elbows having geometrical peculiarities in the zone of weld joints are presented. It is shown that relatively low calculated stresses in weld joints correspond to the actual degree of microdamage in elbows that have been in operation for 164000 h. Recommendations for extending the service life of elbows are given.

Using electronic speckle interferometry for the accurate determination of the residual stresses in welded joints and structural members

Using electronic speckle interferometry for the accurate determination of the residual stresses in welded joints and structural members

Residual stresses in welded joints of high-strength steels

By using a “GLEEBLE-3800” complex, we perform the experimental investigations of the dynamics of changes in the yield strength of the metal of the heat-affected zone (HAZ) in low-carbon high-strength steels for various rates of cooling of the welded joints. The influence of the rate of energy input and thermal welding cycles on the formation of residual stresses in welded joints of steels with different chemical compositions and properties is determined both experimentally and numerically. The relationship between the residual stresses, modes of heat input, and the period of holding of the HAZ metal at temperatures above the point AC3 is established.

Cruciform fillet welded joint fatigue strength improvements by weld metal phase transformations

ABSTRACTArc welding typically generates residual tensile stresses in welded joints, leading to deteriorated fatigue performance of these joints. Volume expansion of the weld metal at high temperatures followed by contraction during cooling induces a local tensile residual stress state. A new type of welding wire capable of inducing a local compressive residual stress state by means of controlled martensitic transformation at relatively low temperatures has been studied, and the effects of the transformation temperature and residual stresses on fatigue strength are discussed.In this study, several LTTW (Low Transformation‐Temperature Welding) wires have been developed and investigated to better characterize the effect of phase transformation on residual stress management in welded joints. Non‐load‐carrying cruciform fillet welded joints were prepared for measurement of residual stresses and fatigue testing. The measurement of the residual stresses of the three designed wires reveals a compressive residual stress near the weld toe. The fatigue properties of the new wires are enhanced compared to a commercially available wire.

Residual stresses in welded joints in 1460 aluminium alloy

Residual stresses in welded joints in 1460 aluminium alloy

Measuring stresses in welded joints by the remagnetisation loss method

(2007). Measuring stresses in welded joints by the remagnetisation loss method. Welding International: Vol. 21, No. 2, pp. 139-141.

Determination of Welding Residual Stresses with Help of the Micromagnetic Measurement Method

The micromagnetic measurement method is a well known technique for a qualitative estimation of residual stresses in ferromagnetic materials. The application due to the advantages of a fast and manageable use is hindered by the high complexity of the calibration procedure for the quantitative residual stress determination when additionally a changing microstructure influences the measured signals. Therefore basic investigations were performed for the residual stress determination of welded joints by the micromagnetic method. A multi-parameter approach by using different micromagnetic techniques was evaluated by a linear regression analysis. For each structural steel a regression polynomial can be calculated for the residual stress determination of differently welded specimens. The accuracy of the prediction depends on the magnetization direction. The experimental results show, that this strategy enables a useful possibility of an easier method for the determination of residual stresses in welded joints.

溶接材料の相変態挙動を利用した溶接継手の残留応力低減効果に関する検討―溶接時における温度・ミクロ組織・熱応力履歴の数値シミュレーションとその応用に関する研究 （第２報）―

Residual stress in welded joints by using a new weld metal with the property of low-temperature phase transformation is numerically analyzed. 10 % Nickel and 10 % Chromium are involved in the developed welding material for producing the property of martensitic phase transformation at a low temperature and for generating compressive residual stress. A fillet-welded joint between plate and stiffener is used for the numerical simulation of the thermal elastic-plastic finite-element analysis with coupling phase transformation effect. Moving heat source is considered by using the gradual deposition of the finite-element during welding process. Distribution of the computed residual stress mostly agrees with the measuring values by strain gauge. Compressive residual stress distributes in the weld metal for both longitudinal and transverse directions with weld line. The effects of the material of weld metal and welding pass sequence on residual stress are then investigated. Residual stresses on the weld toe and root are improved lower by using the low-temperature transformation weld wire than the conventional one, regardless of the sequence of welding deposition. It is found that the weld metal with property of low-temperature phase transformation is effective to reduce residual stress near weld metal.

Diffraction Measurements of Residual Macrostress and Microstress Using X-Rays, Synchrotron and Neutrons

The present paper reviews some recent developments of the measurements of the macrostress and microstress by diffraction using X-rays, synchrotron and neutrons especially in Japan. These three methods are based on the same principle of the diffraction of crystals, and have different advantages. The conventional X-rays detect the stress very near the surface, while the neutron diffraction takes the stress in the interior of the materials. High-energy X-rays from synchrotron sources have the penetration depth in between and are suitable for the measurement of subsurface stresses. After describing the developments of the fundamentals of the methods, the paper covers the recent applications of the diffraction methods to the residual stress analysis in textured thin films, the nondestructive determination of the subsurface distribution of residual stress in shot-peened materials, local stress measurements near the crack tip, the stress measurements of single crystals, macrostress and microstress measurements in composites, and the determination of the internal distribution of the residual stress in welded joints.

Residual stress relief in MAG welded joints of dissimilar steels

This paper addresses the relief of residual stress in welded joints between austenitic and non-alloyed ferritic–pearlitic steels. A series of similar and dissimilar steel joints based on the 18G2A (ferritic–pearlitic) and 1H18N10T (austenitic) steels were produced, some of which were stress relieved by annealing and some by mechanical prestressing. For the as-welded and stress relieved test joints the residual stresses were measured by trepanning. To aid the interpretation of these results, 2D plane stress finite element analysis has been performed to simulate the residual stress relieving methods. Analysis of the results has shown that thermal stress relieving of welded joints between dissimilar steels is not effective and may even increase residual stresses, due to the considerable difference in thermal expansion of the joined steels. It was found that, for the loads imposed, the effectiveness of the mechanical stress relieving of dissimilar steel welded joints was much lower than that of similar steel joints.

Residual Stresses in Welded Joints – Sources and Consequences

Residual stresses in welded joints are a consequence of hindered shrinkage of the heated zones and in materials like steels where phase transformations occur of the combined effect of hindered volume expansion. With these two elementary processes any residual stress distribution can be described conclusively if the cooling conditions and the material properties like the transformation behaviour are known. The grade of restraint of the weld seam is the most important boundary condition which is responsible for the opportunity that high residual stresses may occur. The grade of restraint is given by the ratio between the heated zones and the apparent colder material and is not primarily depending on the size of a component. Every way to reduce the grade of restraint offers principally the possibility of an increasing distortion. Many experiments show, that a certain control of the welding parameters which should be carefully adjusted on the properties of each material enables a combination of favourable strength and toughness properties with acceptable residual stresses.

Determination of the Residual Stresses in Weld Joints of Different Steels

Determination of the Residual Stresses in Weld Joints of Different Steels

An efficient approach for computing residual stresses in welded joints

Although the finite element method has emerged as one of the most attractive approaches for computing residual stresses in welded joints, its application to practical analysis and design problems has been hampered by computational difficulties. These difficulties do not arise in modeling the complex constitutive response of melting and solidifying metal; rather, they occur mostly because of the enormous computational size of any practical problem resulting primarily from the three-dimensional (3D) modeling of a welding process. Although two-dimensional (2D) modeling has been used widely in residual stress problems, current belief holds that 2D analysis cannot render accurate residual stresses that occur due to welding. This study investigates the residual stress fields in a welded T-joint, comparing those computed by 3D models with those computed by 2D models. The study shows that the temperature distribution in the central zone of the joint can be captured successfully by a 2D finite element model and a technique that takes into account the heat transfer balance and welding speed. The residual stresses in the plane of the 2D model computed by this method show fairly good agreement with those computed by the 3D model. More substantial differences are observed in the out-of-plane stresses, which are attributed primarily to the different mechanical boundary conditions in the out-of-plane direction of the 2D and the 3D models. All analyses in this investigation are performed with the finite element code ABAQUS.

Prevention of damage to welded joints of 12Kh18N10T steel in production of potassium nitrate

We analyzed damage to welded joints of pipes made of 12Kh18N10T steel in working media for the production of potassium nitrate. We showed that the corrosion cracking of objects was caused by the action of chlorides in technological solutions under a high level of residual postwelded stresses in welded joints. We give some recommendations for the prevention of the corrosion cracking of welded joints of pipelines and pressure filters.

Effect of the optimum thermal welding conditions on residual strains and stresses in welded joints in Zr-2.5% Nb alloy

Effect of the optimum thermal welding conditions on residual strains and stresses in welded joints in Zr-2.5% Nb alloy

Thermoacoustic method for relaxation of residual stresses in welded joints

We propose a thermoacoustic method for the relaxation of residual stresses in welded joints, present a block diagram of a generator of local thermoacoustic pulses designed for implementation of this method, and describe our experiment aimed at relaxation of residual tensile stresses.

Calculation of the residual stresses in welded joints of hard alloys with steels by the boundary elements method

Calculation of the residual stresses in welded joints of hard alloys with steels by the boundary elements method