AXIAL FORCE MEASURING METHOD OF PLASTIC REGION CLAMPING BOLT

摘要

PURPOSE:To derive easily an axial force of a bolt clamped up to a plastic region by clamping the bolt to the plastic region, measuring a natural frequency of the bolt, subsequently, loosening the bolt, and measuring its natural frequency. CONSTITUTION:A head bolt 4 is clamped so that its axial force becomes about 0.5ton to 1.0ton, and in that state, a natural frequency Fp of the head bolt 4 is measured. At that time, a strain epsilonp detected by strain gauges 3, 3 is measured simultaneously, and basing on this strain epsilonp, the axial force of the head bolt 4 of the clamping time is derived exactly. Thereafter, in a state that its axial force becomes zero by loosening the head bolt 4, a natural frequency Fo of the head bolt 4 is measured. In this way, the axial force of the bolt clamped up to the plastic region can be derived easily by utilizing a relative characteristic of the natural frequency and the axial force of the bolt in the plastic region basing on Fo-Fp.