チタン材料の接触熱抵抗の測定とボルト締結体への応用

抄録

Titanium and titanium alloys have a lot of excellent characteristics when used for the parts and components of machines and structures. As for bolted joints, however, they are used only for some limited cases because of the high cost. Their specific characteristics, e.g., low weight and high resistance to corrosion, are highly attractive from the engineering point of view. In this paper, thermal contact coefficients at the interface composed of titanium and titanium alloys are measured, and the empirical equations for evaluating the coefficients are derived in the same form proposed in the previous papers. Then, heating experiments of bolted joints, tightened by titanium bolts, are conducted to examine how the bolt preloads vary when subjected to thermal loads, and the bolt preload variations are compared to the case tightened by carbon steel bolts. In the next place, aiming at a broader use of titanium and titanium alloy bolts, numerical analyses are performed to demonstrate the effectiveness of those bolts by incorporating the foregoing thermal contact coefficients into the finite element formulation. The numerical results are favorably in good agreement with the experimental ones, and they suggest that threaded fasteners made of titanium alloys can be favorably applied to the joints whose clamping forces are likely to decrease when subjected to thermal loads.