Deformation Of Welded Joints Research Articles

Effects of different friction stir welding processes on residual stress and deformation of Ti62A alloy joints

Residual stress induced by welding easily causes deformation and even fracture failure in welded structures. In this paper, a three-dimensional thermal-mechanical coupling finite element model of friction stir welding (FSW) was developed. The effects of different welding processes, namely conventional friction stir welding (C-FSW), stationary shoulder friction stir welding (SS-FSW), and bobbin tool friction stir welding (BT-FSW), on the temperature, residual stress, and deformation of welded joints were investigated by employing a heat source model and a force model to the welding analysis. The results reveal that a discernible disparity in temperature gradient is observed in the region ahead of the tool and behind it among various welding processes. The peak values of longitudinal residual stress along the surface and bottom paths of SS-FSW are reduced by 35.7% and 34.1%, respectively. In addition, the deformation at the initial end of the weld is slightly larger than that at the final end along the welding direction in three welding processes. Compared with other FSW processes, SS-FSW exhibits the smallest deformation, which is advantageous for improving assembly accuracy and enhancing the load-bearing capacity of weldments. The above results provide an important theoretical reference for the FSW process optimization of Ti62A alloy.

A rigid-flexible coordinated method to control weld residual stress and deformation during local PWHT for ultra-large pressure vessels

Local post welding heat treatment (PWHT) is a feasible method to eliminate weld residual stress for ultra-large pressure vessels. This paper is focused on the discussion of weld residual stress and deformation for the typical ultra-large mechanical penetration inserted plate (MPIP) during the local PWHT. The reason why the MPIP subjected to local PWHT causes cracking is clarified. A rigid-flexible coordinated control method is proposed to prevent cracking during local PWHT for the ultra-large pressure vessels. The results show that the inconsistent deformation and greater stress concentration in weld toe are the main reason to result in cracking during PWHT. The axial stresses and radial deformation in the welded joints can be reduced by the rigid-flexible coordinated control method. The axial stress is changed to compressive stress, and the radial deformation is reduced by about 58%. And the inconsistent deformation in welded joints during the heat treatment can be obviously improved, which is of great significance to ensure the safe service for ultra-large pressure vessels.

Evaluation of the modes effectiveness of concomitant vibration processing of the AMg6 alloy welded joints

ABSTRACT At present, vibration treatment combined with the arc welding process is used for responsible welded structures with strict requirements for dimensional stability and mass. Vibration processing mode was set by amplitude and frequency. The efficiency of combined vibration treatment was estimated by the level of reduction of residual stresses and residual deformations of welded joints of AMg6 alloy. The region of optimal regimes is found.

Analysis of Ultimate Load-Carrying Capacity of Combined Connection with Bolts and Welds

In this paper, load-carrying and deformation capacity of tension lap splices that have both welds and bolts acting in the same shear plane are studied using numerical method. The failure criterion of bolts and welds are given based on the finite element calculation and compared with existing experiment results, it shows that the established numerical model is correct and reliable. The strength of longitudinal welds and the bearing capacity of the high-strength bolts before slipping can be fully used in the combined joints, the bolts and welds fail almost simultaneously. The deformation of welds in combined connections is less uniform than its’ deformation in welded joints as the welds fails, and it causes the deformation of welds as failure is larger in combined connections than in welded connections. The deformation capacity of the combined joint are slightly increased contrasted with bolts joint and welds joint because of the interplay of bolts and welds acting in the same shear plane. The strengths of welds and bolts performed in combined connections can reach 0.95 and the deformation of combined connection is increased at least 1.10 times as the welds connection or the bolts connection.

Hybrid inversion method and sensitivity analysis of inherent deformations of welded joints

In order to efficiently predict the welding deformation of large and complex welded structures based on the inherent deformation method, it is necessary to obtain the inherent deformations of each weld seam beforehand. In this paper, a new method was proposed to inverse inherent deformations by combining inherent deformation method and complex method. The validity of the proposed hybrid inversion method was proved by the comparison with the results of thermal-elastic-plastic (TEP) model the effectiveness of which had been demonstrated by the welding deformation and residual stress obtained from the butt-welded experiment. And the independence of the method on initial value is verified by inversion results using different initial complex shapes. Finally, the sensitivity analysis of inherent deformations was also carried out, and the analysis result shows that longitudinal shrinkage, transverse shrinkage and transverse curvature have a more significant effect on calculation accuracy than longitudinal curvature for the present welded plates.

The influence of joining technique on the deformation of laser welded T-joints

T-joints are often used in large-scale welded constructions. The use of a laser beam for welding allows to create joints using various techniques. Used welding method affects the shape and size of heat affected zone, deformation of welded elements and consequently the quality of the joint. This work concerns the numerical modeling of the size of heat affected zone and welding deformations in T-joint obtained with two different welding techniques: single-side fillet T-joint and butt welded T-joint, called I-core welded joint. Numerical simulations are carried out in the commercial Abaqus FEA software, supplemented by an additional numerical subroutines which enabled the analysis of thermomechanical phenomena occurring in welding process. Mathematical model of a moveable welding source and the description of heat source positioning relative to the edges of the connected elements are described in numerical subroutines. The material parameters of austenitic steel are taken into account. The size of deformations of welded joints are determined as well as the influence of two different joininig techniques of T-joint on the amount of generated welding deformations are analyzed and compared.

Numerical Analysis and Experimental Research on Deformation of Flat Made of TIG Welded 0H18N9 Steel

The paper presents a numerical analysis of deformations of TIG welded flat made of stainless steel 0H18N9. Numerical simulations of temperature field, stress and deformations of welded joints is carried out using Abaqus/FEA engineering software. Goldak's mathematical model is used to describe the distribution of moveable heat source power. The numerical analysis takes into account temperature dependant thermo-mechanical properties of welded steel. Presented results of calculations include temperature field, stress and deformations in welded joint. The results of numerical calculation are compared with experimental results.

The Plastic Deformation of RFSSW Joints During Tensile Tests / Deformacja Plastyczna Wybranych Połączeń RFSSW Podczas Rozciągania

The dynamic development of the friction stir welding (FSW) technology is the basis for the design of durabe joints inter alia in the aviation industry. This technology has a prospective application, especially for the aluminum alloys. It is suitable for a broad spectrum of permanent joints. The joints obtained by FSW technology are characterized by good mechanical properties. In this paper, the friction stir spot welding joints were analysed. The example of a structure made using this technology were presented. The lap joints made of 2mm Al 6061-T6 sheets were the investigation subject. The different spot welds arrangements were analysed. The tensile test were performed with optical deformation measurement system, which allow to obtain the plastic deformation field on the sample surface. The plastic strain graphs for the characteristic line passing through the maximum deformation were registered and presented. The experimental results were compared to the FEM numerical analysis. The numerical models were built with 3D-solid elements. The boundary conditions, material properties and geometry of the joints were identical as during experimental investigation. The mechanism of deformation of welded joints during tensile test was described and explained. It has been found that the arrangement of the spot welds with respect to the tensile direction has an important influence on the behaviour and deformation of lap joint.