On the Influence of Welding Residual Stresses on the Dynamic Behavior of Structures (original) (raw)
Related papers
Assessment of Welding Residual Stresses in Rectangular Plates Using Vibration Data
A new hybrid numerical/experimental technique for stress assessment, which explores the influence of stresses on dynamic responses of structures, is used for the identification of weld-induced residual stresses in rectangular plates. This technique, named SIFDRIM (Stress Identification from Dynamic Responses-Inverse Method), consists of using modal properties, like a set of natural frequencies, to identify the parameters of a given mode for the stress distribution over the plate. A parameterized stress model suitable to the case of welding residual stresses is presented, in terms of a differential equation that relates Airy's stress function to the plastic strains resulting from the welding process. From this stress function, the stress components y x σ σ , and xy τ (assuming plane stress state) can be assessed. To demonstrate the feasibility of the method, it is used tor the assessment of stresses in a TIG (GTAW) welded thin rectangular steel plate, based on experientally measured natural frequencies and numerically computed weldinduced stress distributions obtained from the literature.
The utilization of thick steel plates, to construct built-up structural components, has become a common practice in modern steel construction around the world. This is due to the need to build taller structures. Additionally, the design specifications require subjecting the structural components of these structures to extreme loading due to earthquakes, wind and/or blast. In thick plates, due to high restraints and long welding time, the welding process induces stresses in adjoined steel plates. The likelihood of occurrence of cracks and dislocations in these plates depends on the plate thickness. These cracks and dislocations may propagate under these induced stresses. In this paper, a detailed finite element model is developed to simulate the welding process of heavy built-up box sections. The simulation is divided into two phases: 1) heat flow and temperature distribution through the welding process; 2) temperature data from phase one are transferred to a stress analysis model th...
Identification of welding residual stresses in rectangular plates using vibration responses
Inverse Problems in Science and Engineering, 2006
A novel hybrid numerical/experimental identification procedure for the assessment of weldinginduced residual stresses in rectangular plates is proposed and evaluated. This procedure explores the influence of the stress state on the dynamic responses of structural components, according to the so-named stress-stiffening effect. The technique consists in using a set of experimental natural frequencies of the welded plate and a mathematical model relating the residual stresses to the natural frequencies to formulate an optimization problem. The cost function represents the differences between the experimental and model-predicted dynamic responses and the design variables are interpreted as parameters of the mathematical model describing the stress distribution over the plate. A parameterized stress model suitable to the case of welding residual stresses is presented in terms of a differential equation that relates an Airy's stress function to the plastic strains resulting from the welding process. From this stress function, the stress components x , y and xy (assuming plane stress state) are computed. Genetic Algorithms are used to solve the numerical optimization problem. To demonstrate the feasibility of the method, it is used for the assessment of residual stresses generated by TIG (GTAW) welding of a thin rectangular steel plate, for which experimentally measured natural frequencies and numerically computed residual stress distributions are available in the literature.
Structures, 2020
As a sequel to another paper of the authors on welding-induced initial deformations [1], this paper aims to obtain a direct measurement database of welding-induced residual stresses in a full-scale steel stiffened plate structure and also to study the applicability of computational models to predict them. A full-scale steel stiffened plate structure in association with plate panels in bottom structures of an as-built containership carrying 1,900 TEU was fabricated using exactly the same welding technology as used in today's shipbuilding industry. The X-ray diffraction method was employed to measure the residual stress distributions in the plating. In addition to simple formula estimations, computational models using the three-dimensional thermo-elastic-plastic finite element method were applied to predict the residual stress distributions. A comparison between full-scale measurements, numerical predictions and simple formula estimations was made. Details of the full-scale measurements are documented as they can be useful to validate the computational models formulated by other researchers.
In many industries, especially accurate industries such as gas turbine and aerospace, welding technology is used to weld thin parts during assembling process. Due to uneven heating and cooling during the welding process, welded parts are prone to sever distortions and/or non-desirable residual stresses. The distortion causes problem in shape in assembly and when residual stresses combined with applied stresses, unexpected failure occurs often. In this paper, three dimensional sequentially thermal-mechanical analysis is used to simulate welding process in Nical base super alloy plates (INCONEL718) for predicting the temperature field, distortion and residual stresses. The study was carried out on butt welded joint with 2 mm thickness, using a commercial Finite Element (FE) package (ABAQUS). The obtained results are compared to numerical and experimental results obtained by other researchers. In order to control the distortion, it was proposed to carry out the welding process on several steps with different sequences. The cases of the welding sequences are: one step in one direction, two steps in two directions and four steps in two directions the study successfully predicted temperature and residual stress in the welded plates. Moreover, it was found that the more the steps of the welding process the less the distortion takes place in the plates.
DETERMINATION OF RESIDUAL STRESSES OF WELDED JOINTS PREPARED UNDER
Welded joints are used for construction of many structures. Welding is a joining or repair process which induces high residual stress field, which combines with stresses resulting from in-service loads, strongly influencing in-service behavior of welded components. When compared with stresses due to service loads, tensile residual stress reduces crack initiation life, accelerates growth rate of pre-existing or service-induced defects, and increases the susceptibility of structure to failure by fracture. Also, welding residual stresses are formed in a structure as a result of differential contractions which occur as the weld metal solidifies and cools to ambient temperature.
A one-dimensional model for the prediction of residual stress and its relief in welded plates
International Journal of Mechanical Sciences, 1996
The simulation of the welding process by means of continuum mechanics models has a very high cost both in input data preparation time and in computing time required for the integration of the complex thermoelastoplastic equations involved in solids with temperature dependent properties. For this reason, the plates in this study will be visualized as formed by a certain number of bars that can carry out elastoplastic behaviour and having temperature dependent properties. The thermal loads are simulated by analytical singular solutions, the thermomechanical problem being solved by means of an incremental algorithm of high efficiency. An excellent agreement has been found between the results numerically predicted and those previously obtained with an experimental technique and the Finite Element Method. Finally, the one-dimensional model developed here is used to predict the effects of a local heat treatment on the residual stresses originated by the welding. The versatility and rapidity of the use of this model makes it specially suitable to be used as a tool to select among different stress relieving procedures.
FINITE ELEMENT MODEL TO PREDICT RESIDUAL STRESSES IN MIG WELDING
The objective of this research is to simulate the complex arc welding process by using the finite element method(ANSYS)[]. After the model is built and verified, the main objective of the research is to study the effects of varying the welding process parameters on the thermo-mechanical responses. In addition to that, the aim of this research is also to find a relationship between welding parameters and thermo-elastoplastic responses. In this research paper, the responses of single pass corner-joint of arc welding are evaluated through the finite element software (ANSYS). The study of this research paper covers only the effects of varying heat input, welding speed on the thermo mechanical responses of the weldment after cooling down to room temperature
Residual deflection due to restrained shrinkage of longitudinal welds is calculated in the case of an asymmetric I-section crane runway girder. The residual welding compression stresses decrease the load-carrying capacity of a welded I-section compression strut in a significant measure. The effective width of a welded stiffened plate should be calculated considering residual welding stresses. The fatigue strength of welded joints is influenced by residual welding stresses significantly. These effects are illustrated by numerical examples.
The International Journal of Advanced Manufacturing Technology, 2013
Effects of three different plate boundary constraints on the residual stress field and deformation are investigated numerically during butt-joint welding. For the numerical solution of the heat transfer equations, the finite element method is used to predict the temperature profile as well as residual stress field due to three different plate boundary conditions. The distortion of the welded plate is modeled as a nonlinear problem in geometry and material, adopting a finite element solution based upon the thermo-elastic-plastic large deflection theory. High-strength shipbuilding steel AH36 with temperature-depending material properties and nonlinear stress-strain material properties (bilinear isotropic hardening option uses the von Mises yield criteria) are assumed for the numerical analysis. For verifying the results, the temperature profile is compared with the result obtained in a previous research. In the mechanical analysis, three different boundary conditions are applied. Effects of plate thickness, plate width, and mesh model on the residual stress with boundary constraint are studied.