LPGタンク隅肉溶接部の疲労挙動について

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In view of safety design against fatigue failure in cylindrical storage tank of low temperature use, low cycle and low temperature fatigue behaviour of shell to annular tee-fillet welded joint in tank was investigated experimentally and analytically, in case of liquefied propane gas tank, using a displacement-controlled bend test of model specimens. The experiments and analyses were done either by strain and displacement measurements around weld toe in annular plate under cyclic deformation or by finite element analysis mainly to clarify quantitatively the effects of type of weld joint as well as dimensions of weld joint, including the effects of annular plate thickness, on the fatigue crack initiation life of tank. Principal results obtained are as follows. (1) In bend test of model specimen, a distribution of strain range in front of weld toe indicates that its maximum value is found at weld toe as far as the deformation range examined, although maximum value of strain distribution is found at 5-10mm distant from weld toe under large extent of deformation. (2) Experiments and analyses show that there is no difference practically between fillet weld joint and full penetration joint in cyclic deformation as well as in fatigue strength. (3) The expression of evaluating the fatigue crack initiation life in the displacement controlled bend test of model specimen was derived in terms of weld joint parameters, which is [numerical formula] where N_c,._p, t. SL denotes fatigue crack initiation life, weld toe radius, displacement range at the loading point, annular plate thickness, and leg length of shell plate respectively. (4) By introducing a parameter _<s-A>, an angle which defines an extent of deformation around weld toe, the fatigue crack initiation life in tank is predicted from the results on model specimen. (5) The finite element analysis shows that as to the bend test on model specimen, the increase of annular plate thickness decreases the initiation life in displacement controlled test, and increases it in load controlled test. However, the incorporation of the results on model specimen to the behaviour in deformation of the tank indicates that these two express-ions are essentially the same as far as the fatigue crack initiation in tank concerned. As of now, it seems that the thicker the annular plate becomes the longer the fatigue crack initiation life in this type of tank.
社団法人日本船舶海洋工学会の論文

LPGタンク隅肉溶接部の疲労挙動について

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