Application of analytical methods for predicting the structures of steel phase transformations in welded joints

The paper presents the feasibility the prediction of phase structures of the medium carbon S355 steel under the transformations running in welding process by using analytical methods. The relationships proposed here allow to specify start and finish temperatures of phase transformations in the case of formation of bainite, ferrite, pearlite and martensite structures at various cooling rates v8/5 (t8/5) as well. Continuous-Cooling-Transformation (CCT) diagram and volumetric fractions of each steel phases possible to occur are determined in function of cooling rates. Analytically obtained values are compared with results obtained by dilatometric research. Correctness of applied analytical methods in this field has been verified when the structure compositions formed in the heat affected zone (HAZ) of electric arc butt-welded sheets made of the S355 steel were predicted

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

The Influence of Welding Heat Source Inclination on the Melted Zone Shape, Deformations and Stress State of Laser Welded T-Joints

The paper concerns the numerical analysis of the influence for three different of welding heat source inclinations on the weld pool shape and mechanical properties of the resulting joint. Numerical analysis is based on the experimental tests of single-side welding of two sheets made of X5CrNi18-10 stainless steel. The joint is made using a laser welding heat source. Experimental test was performed for one heating source inclination. As a part of the work metallographic tests are performed on which the quality of obtained joints are determined. Numerical calculations are executed in Abaqus FEA. The same geometrical model is assumed as in the experiment. Material model takes into account changing with temperature thermophysical properties of austenitic steel. Modeling of the motion of heating source is performed in additional subroutine. The welding source parameters are assumed in accordance with the welding process parameters. Numerical calculations were performed for three different inclinations of the source. One inclination is consistent with experimental studies. The performed numerical calculations allowed to determine the temperature field, shape of welding pool as well as deformations and stress state in welded joint. The obtained results are compared to results of the experiment

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

Computer analysis of thermal phenomena and deformation in lap joint welded by a laser beam

Laser welding technology is applied to many types of welded joints. The determination of the influence of technological parameters on the properties of resulting joint is a significant problem for technologists. Numerical estimation of the shape of the weld and its deformation is important in the initial stage of construction design. The paper concerns computer analysis of thermal and mechanical phenomena in laser welded lap joint made of austenitic steel. Three dimensional discrete model of analyzed lap joint is created in Abaqus FEA engineering software. Numerical analysis takes into account temperature dependent thermomechanical properties of austenitic steel. The movable heat source power distribution is modelled using Gaussian distribution. Computational model takes into account the gap between the joined plates. Temperature distribution in analysed joints is presented on the basis of performed numerical simulations. The shape and size of the fusion zone as well as deformation of the joint are estimated

Development of mathematical and numerical models for the analysis of overlap laser beam welding of dissimilar materials

The welding process of dissimilar materials causes a lot of technological issues related to different properties of materials of joined elements. Thermal conductivity is one of most important factors influencing the deformation of the weld. The change of thermal conductivity in the function of the temperature can produce various strains that cannot be predicted during construction design. Different structures of materials appear during joining of dissimilar materials as well as different characteristic zones of the joint and its mechanical properties. The most important is the proper identification of joint zones and the size of deformation at the production stage of welded construction. This work presents the numerical analysis of physical phenomena in overlap welding of two sheets made of S355 carbon steel and 304 austenitic steel using a laser beam. A three-dimensional discrete model is developed taking into account thermophysical properties changing with temperature. Temperature distribution and the shape of the welding pool is predicted on the basis of performer computer simulations. The influence of thermal load on the formation of stress and strain fields is determined

Computer analysis of thermal phenomena and deformation in lap joint welded by a laser beam

Laser welding technology is applied to many types of welded joints. The determination of the influence of technological parameters on the properties of resulting joint is a significant problem for technologists. Numerical estimation of the shape of the weld and its deformation is important in the initial stage of construction design. The paper concerns computer analysis of thermal and mechanical phenomena in laser welded lap joint made of austenitic steel. Three dimensional discrete model of analyzed lap joint is created in Abaqus FEA engineering software. Numerical analysis takes into account temperature dependent thermomechanical properties of austenitic steel. The movable heat source power distribution is modelled using Gaussian distribution. Computational model takes into account the gap between the joined plates. Temperature distribution in analysed joints is presented on the basis of performed numerical simulations. The shape and size of the fusion zone as well as deformation of the joint are estimated

Computer simulations of thermal phenomena in surface heating process using the real distribution of Yb:YAG laser power

This work concerns mathematical and numerical modelling of temperature field during Yb:YAG laser heating of sheets made of S355 steel with the motion of liquid steel in the fusion zone taken into account. Laser power distribution and the caustics are determined on the basis of the geostatistical kriging method. Temperature field and melted material velocity field in the fusion zone are obtained from the numerical solution of continuum mechanics equations using projection method and finite volume method. Numerical algorithms are implemented into computer solver using ObjectPascal programming language. Computer simulations of Yb:YAG laser heating process are performed for different process parameters. Characteristic zones of experimentally obtained cross sections of heated elements are compared to numerically predicted fusion zone and heat affected zone

Computer simulations of thermal phenomena in surface heating process using the real distribution of Yb:YAG laser power

This work concerns mathematical and numerical modelling of temperature field during Yb:YAG laser heating of sheets made of S355 steel with the motion of liquid steel in the fusion zone taken into account. Laser power distribution and the caustics are determined on the basis of the geostatistical kriging method. Temperature field and melted material velocity field in the fusion zone are obtained from the numerical solution of continuum mechanics equations using projection method and finite volume method. Numerical algorithms are implemented into computer solver using ObjectPascal programming language. Computer simulations of Yb:YAG laser heating process are performed for different process parameters. Characteristic zones of experimentally obtained cross sections of heated elements are compared to numerically predicted fusion zone and heat affected zone

Numerical Prediction of Strength of Socket Welded Pipes Taking into Account Computer Simulated Welding Stresses and Deformations

The paper presents a numerical model based on the finite element method (FEM) to predict deformations and residual stresses in socket welding of different diameter stainless steel pipes made of X5CrNi18-10 steel. The next part of the paper concerns the determination of strength properties of a welded joint in terms of a shear test. A thermo-elastic–plastic numerical model is developed using Abaqus FEA software in order to determine the thermal and mechanical phenomena of the welded joint. This approach requires the implementation of moveable heat source power intensity distribution based on circumferentially moving Goldak’s heat source model. This model is implemented in the additional DFLUX subroutine, written in Fortran programming language. The correctness of the assumed model of thermal phenomena is confirmed by examinations of the shape and size of the melted zone. The strength of the welded joint subjected to shear is verified by performing a compression test of welded pipes as well as computer simulations with validation of the computational model using the Dantec 3D image correlation system