The strain amplification sensor: A 3D-printable stand-alone strain gauge for low-cost monitoring

Abstract

Current in situ strain sensing techniques focus on determining accurate, time-histories of strain utilizing fairly complex sensing, compensation, data processing, and powering arrangements. A simpler and lower-cost strain sensing approach would open up more opportunities to use strain measurements to support engineering decision making. This work explores a fully mechanical, ultra-low cost strain sensor printed using additive manufacturing techniques.The accuracy of current additive manufacturing techniques are discussed, and the performance of the sensor in terms of accuracy, measurement repeatability, and batch-to-batch manufacturing variability are studied. An example of using the proposed sensor to measure transient thermal weld stresses is presented.Overall, the key challenge to such a sensor is shown to be the accuracy of pin and slot print features and the resulting slip and friction introduced into the sensor. A properly calibrated design printed with current state-of-the-art machines is shown to be capable of resolving strain changes on the order of one micro strain with good repeatability.

Misconceptions about temperature compensation in experimental stress analysis

“…The current temperature compensation technique is based on the Wheatstone bridge shown in Figure 1 within the resistance strain instrument. With the corresponding connections it is not only possible to increase the accuracy of structural strain testing but also to eliminate structural temperature strains [6,7]. In the case of the 1/4 bridge, the working gauge R1 is attached to the surface of the component, meanwhile a dummy gauge R2 is attached to a temperature compensation block.…”

Region-based online flaw detection of 3D printing via fringe projection

“…The proposed approach provides qualitative in-process information regarding residual stresses and part porosity. In addition, the use of strain gages mounted on the build platform measure the strains and residual stress in the metal components [6]. The strain changes in a build platform can be measured when SLS-induced layers are successively milled off.…”