Repeatable System to Pre-Bend Blades for Accurate Cutting of Dumbbell-Shaped Specimens for Tensile Testing

Mechanical properties of soft tissues can be determined by performing uniaxial tensile tests on small specimens (i.e. test coupons). The ideal geometry for tensile testing is a dumbbell shape, but manufacturing a custom steel punch is costly and time intensive thus preventing the widespread adoption of dumbbell shaped coupons. The Print-A-Punch device, a 3D-printed cutting device assembled with standard fasteners and razors, was developed as an economical and reliable alternative. However, the use of straight blades in the device introduced dimensional errors in the gauge length of test coupons resulting in the need to pre-bend the blades to improve gauge length accuracy. The objective of this study was to develop and validate a device and method to pre-bend blades. The Bend-A-Blade system was developed to rapidly and accurately bend razor blades into a shape more consistent with dumbbell coupons. This system consists of 3D-printed plates and paddles for quick and economical fabrication. Validation using a custom MATLAB code found the use of pre-bent blades reduced error in the test coupon’s gauge length by 31% compared to straight blades. The use of bent blades allows for the Print-A-Punch device to fully provide an accurate and cost-effective solution to cut dumbbell coupons.