VDA Volume 5.2 - Capability of Measurement Processes for the Torque Inspection on Bolted Joints, 1st edition 2013

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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
specification XE "tightening specification" s 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.