On the use of quartz crystals in dynamic stress and force transducers

An important consideration in determining the veracity of data obtained from X-cut quartz crystals used to measure nominally one-dimensional load states is the role which spatial nonuniformity of the normal stress distribution on the crystal will play in determining the transducer output signal. This role was found to be minor both for crystals located 0.74 mm below a surface subjected to impact by spherical steel strikers and for 25.4-mm-diam crystals positioned in a 12.7-mm-diam Hopkinson bar through which a longitudinal wave was travelling. Load transducers utilizing two crystals to eliminate undesirable signals arising from bending of the crystal were also studied by attaching these devices to plates and subjecting them to dynamic loading by steel spheres. While bending effects were successfully eliminated, it was found that the method of transducer attachment may give rise to additional unwanted signals associated with other modes of crystal deformation.