Review on the prediction of residual stress in welded steel components

Residual stress after welding has negative effects on the service life of welded steel components or structures. This work reviews three most commonly used methods for predicting residual stress, namely, empirical, semi-empirical and process simulation methods. Basic principles adopted by these methods are introduced. The features and limitations of each method are discussed as well. The empirical method is the most practical but its accuracy relies heavily on experiments. Mechanical theories are employed in the semi-empirical method, while other aspects, such as temperature variation and phase transformation, are simply ignored. The process simulation method has been widely used due to its capability of handling with large and complex components. To improve its accuracy and efficiency, several improvements need to be done for each simulation aspect of this method

The influence of chemistry inhomogeneity on microstructure development and residual stress

The chemistry distribution is of importance in the welding process. By varying the chemical composition, the evolution of microstructure and the residual stress change correspondingly. To examine the effect of chemistry, a three-dimensional metallo-thermo-mechanical model is created. The model is established according to a bead-on-plate welding experiment. Samples of S700 steel are manufactured by gas metal arc welding (GMAW). In total, three welds with three heat inputs were conducted so that different chemistries are obtained. The final weld geometry and the uniform chemistry in the fusion zone (FZ) are predicted by the software SimWeld. The parameters in the double ellipsoidal heat source are also calibrated by SimWeld. An inhomogeneous chemistry field is created using the data predicted by SimWeld and the chemical composition of base material (BM), and is further imported to the coupled model by writing user subroutine in ABAQUS. The metallurgical algorithm is implemented in the same way for calculating the phase volume fraction using both the homogeneously and the inhomogeneously distributed chemistry fields. After the temperature and microstructure are determined, the mechanical analysis is conducted using linearly interpolated material properties. Finally, the results of microstructure distribution and the residual stress predicted for homogeneous and inhomogeneous field are compared to clarify the influence of chemical composition

Quantitative description between pre-fatigue damage and residual tensile properties of P92 steel

The alteration of material tensile properties is inevitable after material subjects to irreversible damage. This paper is devoted to quantify the influence of pre-fatigue damage on the residual tensile properties of P92 steel. Various pre-fatigue tests followed by uniaxial tensile tests are conducted at 650 degrees C. Results indicate that higher strain amplitude of pre-fatigue loading leads to reduction in residual yield stress and ultimate tensile stress (UTS). In addition, the evolution of yield stress and UTS in terms of pre-fatigue lifetime fraction shows two stages, namely initial rapid degradation stage and linear decreasing stage. The microstructure observation manifests that the growth of martensite lath width and the decline of dislocation density during pre-fatigue loadings contribute to the degradation of subsequent tensile strength. However, the reduction in dislocation density plays a dominant role. Furthermore, a pre-fatigue damage definition is proposed. The variations of residual yield stress and UTS can be described linearly with respect to the defined pre-fatigue damage. The newly proposed linear relationships are convenient for practical application