An Experimentally Validated Physics-Based Simulation Approach to Predict the Fracture of Shear Devices Used in Downhole Tools

Shear devices are used in the energy industry to control the actuations of downhole equipment. These devices must shear reliably at desired forces. The failure to do so leads to substantial non-productive time and workover. Due to design and environmental sensitivities, achieving reliable fracture of the shear devices is challenging. Design of Experiment (DOE) method with a numerical damage model was used to understand design sensitivities which enable reliable performance of shear devices. In doing so, a temperature-dependent elastoplastic ductile damage model was constructed and calibrated for a metal material. The maximum shear stress (MSS) damage model, calibrated with a single uniaxial tension test, demonstrated good performance in capturing the complex variation in critical failure strain. Implementation of the MSS damage model in FEA facilitated accurate prediction of crack initiation and propagation in shear devices. The numerical DOE studies on shear devices were conducted by changing various critical parameters, including shear plane, contact angle, engagement length, boundary conditions, and cross-sectional diameter. The results were validated through a series of experimental tests. The simulated shears closely matched testing results, usually within 10%, and the predicted fracture surface profiles and fragments aligned well with experimental observations. The modeling technique was extended to case studies on actual shear devices, and experimental results were replicated accurately.