Abstract
There are several tightening methods for the bolted jonts such as the torque control, the angle control, and etc.According to JISB 1083, the tightening coefficient Q (Fmax/Fmin) by the angle control method is smaller than the torque control method. It means that there are possibilities to adopt smaller size bolts. To determine tightening specifications of the angle control method, it is important to understand the relationships between the tightening angles θ[°] and the bolt axial forces F[kN]. In the tightening process, the relationships show closely liner characteristic after the snag points. It was previously shown that the values of inclinations dF/dθ[kN/°] obtained by the simplified calculation formulas or FEM analyses are larger than by physical tests. As the reasons, the approach of interfaces ζ[μm] caused by deformations of fine surface roughness on the each contact surface are considered. In this study, the tightening tests using steel(S45C), aluminum alloy(A6061-T6) and spheroidal graphite iron casting(FCD450) with different surface roughness as clamped prats are conducted. As a result, it is shown that the value of dF/dθ[kN/°] in case of the surface roughness 20μmRz is smaller than in case of 10μmRz, and that the value of dF/dθ[kN/°] in case of combination of A6061-T6 and S45C is smaller than in case of FCD450 and S45C, even if the surface roughness at the contact surface is same.
