Pages 59-60
The revision of ISO 898-1 is now being worked out in ISO/TC 2/SC 1/WG9,in which the introduction of tensile testing method for full-size bolts has been discussed. The tensile testing was originally proposed to check the yield strength and the ductility of the cold forged products (property classes of 4.8,5.8 and 6.8) which cannot be measured by the test using machined test pieces, and the application is going to be expanded to all the property classes for better qualification of the property. The yield strength R_<pf> of full-size bolts is defined as the stress at 0.4% non-proportional elongation, and the permanent elongation at fracture A_f (%) is calculated based on the free thread length set to 1.2d. The aim of this paper is to clarify the relation between the properties on full-size bolts and those obtained from conventional tensile test using machined test pieces, and to propose the appropriate figures on values to be specified. The results from the round robin test conducted by the Japanese ISO/TC 2 Committee show that the test conditions including the type of testing machine affect R_<pf> and A_f values. The load/elongation curves derived from FEM analysis show the feature of those from full-size testing well, and the possibility to determine the detailed testing conditions is confirmed.
