Prediction Of Welding Deformations Of Ship Structures Based On Inherent Strain

Deformations of a welded ship structure injure the beauty of appearance of a structure and cause errors during the assembly of the structure. In addition, weld deformations reduce the strength of the structure. The correction of weld deformations requires reworks and decreases productivity. Therefore, developing a precise method to predict and control the deformations is essential.The equivalent load method based on the inherent strain is studied in this thesis. It is an efficient method for predicting the welding deformation of complicated structures. When using this method, the distribution of the inherent strain in the welded region and equivalent loads induced by the inherent strain must be calculated. Then the final deformations are calculated by finite element analysis. The main contents are as follows:1. An elastic plastic analysis model—bar-spring model is used in the method. Inherent strain is studied though the thermal history of strain. It is showed that the highest temperature and the degree of restraint change the distribution of the inherent strains in the welded region. The inherent strain is changed with the position.2. Three-dimensional transient temperature distributions and the highest temperature distributions are obtained by heat conduction analysis for bead-on-plate welding and fillet welding instead of experiential formulas used before. In the process of analysis, the temperature-dependent properties of materials are considered. The results in this thesis are supported by relevant references. Compare with the result of C.H.Lee' thesis, the error is 3.04%.3. Combining others' experimental results with finite element analysis by applying unit loads on structures, the internal restraint due to nonuniform distributions of temperature and the external restraint induced by the stiffness of structures and boundary conditions are studied in the thesis. The expression of degree of restraint during manufacturing is obtained. The nonlinear elastic modulus is discussed in the finite element analysis. Compare the results in this thesis with reference[82], the errors are 2.94%, 7.14%, 2.56%.4. The equivalent loads of welding region are derived by the integration of...