Preface

Various standards and guidelines specify requirements for estimating and considering the uncertainty in measurement. In this regard, companies face various questions in implementing and certifying their quality management system.

The VDA Volume 5 [1] explains how to meet these various requirements for reproducible measurable characteristics.

The requirement for repeatably measurable characteristics is not met by static torques since the original condition is changed by tightening the bolted joint. The same applies to measurement methods where bolted joints are loosened and re-tightened.

Additional difficulties in evaluating the capability of measurement processes of static torques, are caused by the fact that the torque tolerance defined in tightening specifications for the dynamic assembly torques is often empirically not suited as the tolerance of the test value. This problem becomes even more obvious in case of torque-angle controlled tightening specifications. Due to the change of the reference quantity from torque to the applied angle, there is no suitable reference value available to evaluate the capability of the measurement processes.

These differences were the motivation to discuss the evaluation of the measurement process capability of torque inspection procedures for bolted joints in this VDA volume.