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In order to predict the distortion generated by welding with high accuracy, distortion with fillet welding was measured by three-dimensional photographic measurement. Then, the experiment was simulated by three-dimensional thermal elastic-plastic analysis by FEM. The important matters that should be noted on predicting the distortion with high accuracy were shown by comparing with the results of the experiment and those of the analysis. The results of measuring temperature could be accurately simulated by non-steady state thermal conduction analysis based on FEM. In carrying out the elastic-plastic analysis, four conditions (equilibrium equation, constitutive equation, condition of compatibility and yield condition) should be satisfied. In welding, the temperature largely changed from a melting temperature to a room temperature. So, yield stress of materials largely changed, too. In particular, yield stress becomes about zero above 700℃. The analysis should be carried out under the yield condition that equivalent stress generated in temperature increment ∆T did not exceed yield stress of materials at high temperature above 700℃. It should be sufficiently recognized that the obtained results were not reliable if the yield condition was not satisfied. Angular distortion generated in fillet welding could be accurately predicted by regarding the weld metal as a deposited metal not assuming that a deposited metal zone was a simple triangle. Specifying an influence factor on longitudinal bending distortion was difficult because the absolute value was small. However, it was indicated that the reasonable result could be obtained by regarding the weld metal as a deposited metal because the absolute value of longitudinal bending distortion at pass ② (the second pass) of which restraint was severer became smaller than that at pass ① (the first pass).

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-A finite element dynamic simulation is performed to gain an insight about the stiffened blast wall structures subjected to blast loading. The simulation was verified using qualitative and quantitative comparisons for different materials. Based on in-depth examination of blast simulation recordings, dynamic behaviors occurred in the blast wall against the explosion are determined. Subsequent simulation results present that the blast wall made of the high performance steel performs much better in the shock absorption. In this paper, the existing finite element shock analysis using the LS-DYNA program is further extended to study the dynamic response of the stiffened blast wall made of the high-performance steel considering high strain-rate effects. The numerical results for various parameters were verified by comparing different material models with dynamic effects occurred in the stiffened blast wall from the explosive simulation. Keywords -Stiffened blast wall, High strain-rate effects, High performance steel, Explosive simulation

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