Abstract
Part qualifying testing is a critical part of product development especially for mission critical
components. This is more pronounced in cases where new manufacturing techniques such as
high speed machining, additive manufacturing and wire electrical discharge machining are applied.
Such techniques invariably modify the surface integrity of the components by introducing amongst
others residual stresses and altering surface roughness. If left unattended, this may affect the
performance of the product in service. Therefore, there is a need to qualify products before full
commercial production and to link the manufacturing strategy to anticipate in service part
performance. Endurance qualifying tests for certain products and components may include full
scale endurance testing and/or a machining strategy endurance evaluation by fatigue testing either
axially or in bending. Crack growth monitoring can be used to indicate the durability and
performance of the product. However, crack growth monitoring during axial or rotating bending
conditions is challenging and expensive. The aim of this paper is, therefore, to report on the
development of a compliance based crack monitoring technique that can reduce the cost and
improve the effectiveness of product qualifying tests. Tests are conducted on grade 5 titanium
alloy (Ti6Al4V) specimens produced using high speed turning. These are then subjected to a
rotating four point bending configuration test. Defect (crack) formation and growth (size) may then
be estimated by compliance (strain) monitoring. This technique was found to be a viable low cost
option for monitoring components during rotating bending conditions and to link the manufacturing
technique to part performance with specific reference to dynamic loading.