AN IMPROVED MICROMETER DEVICE FOR ACCURATE MEASUREMENT OF OUTSIDE DIAMETER OF THIN WALLED STAINLESS TUBES FOR THE PURPOSE OF MEASURING RESIDUAL STRESS

摘要

The present invention relates to an improved micrometer device for accurate measurement of residual stress in thin-walled stainless tubes, the residual stress measurement involving twin measurement of outside diameter of the tube before and after slitting of the tube along its length at 180° to the weld seam, the twin measurement values of the outside diameter (d0, d1) being applied to a formula provided in the ASTM A 1928 standard which output the value of the residual stress, a V-anvil type micrometer (2) is disposed on a micrometer stand (3) to provide rigidity of the device; the width of the anvil of the V-anvil micrometer (2) is extended on one side compared to the normal width so that the extension is enabled to support the full-length of the tube (1); the V-anvil is electrically insulated including provision of an electrical circuit which ensures a contact signal between the micrometer and the tube (1) via sounding a buzzer (5).