Development of a New Testing Machine for Torque/Clamp Force Testing for Threaded Fasteners in Accordance with ISO 16047

Abstract

ISO 16047 was published in 2005, where test method and conditions to quantify the tightening characteristics for threaded fasteners are specified. However, there is no testing apparatus applicable to various types of threaded fasteners due to the constraint on the accuracy of ±2% of the values to be measured. The goal of this study is to develop a new tightening testing machine to be used for the torque/clamp force testing in accordance with ISO 16047. In this study, the load/torque cell system having new constructions with piezoelectric force sensors were developed and evaluated, which can be used to measure the clamp force and torques acting on bolt shank and on bearing surfaces, respectively. The piezoelectric sensor has the merits in terms of the resolution of the measurement and its high rigidity. However, experience shows that there are some disadvantages as well to be removed to achieve the measurement with sufficient accuracy. Experimental and analytical considerations have been performed to seek the root causes that may generate the measuring error. Consequently, the possibility to exclude such bad effects as the crosstalk and the drift of the sensitivity was confirmed, and the appropriate design concepts and parameters were proposed.

Keywords

• fixing element
• threaded fastener
• bolt/nut assembly
• torque/clamp force testing
• tightening testing machine
• load/torque cell system
• piezoelectric force sensor