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ANSYS/LS-Dyna Drop Simulations for Stryker Orthopaedics

Stryker Orthopaedics, a leading developer of orthopaedic joint replacement devices, was interested in studying how shock loads in a knee joint can affect the way a patient "feels" the joint as they walk.  Thus began Stryker's search for materials that would not only provide the excellent wear properties expected of their joints, but also offer superior damping characteristics.  To this end, Stryker Orthopaedics developed a drop test rig used to quantify the damping behavior of their proposed materials.  While the rig provided some raw transmissibility data, it did not produce the damping coefficients they needed for future full joint models, nor did it provide the insight Stryker needed to quantify the effect of stiffness and damping on the shock response of a material.

Based on Stryker's positive experiences with prior modeling and training provided by CAE Associates, CAE Associates was chosen to develop and validate a modeling tool for this purpose.  Specifically, Stryker needed models they could use to determine material damping coefficients, measure the relative influence of different modeling parameters, and calibrate these parameters. 

Drop Test Rig
ANSYS/LS-Dyna Model (Quarter Symmetry)

CAE Associates responded by developing models with the ANSYS/LS-Dyna software that precisely simulated the drop test rig.  Damping coefficients, contact parameters, mesh density, and other parameters were calibrated to the test data, providing necessary information on how to build full joint models that will produce an accurate shock response.  The models also provided valuable insight into the relative influence of different material and model parameters on the shock response of the material.

Stryker Orthopaedics believes that these models provide a valuable complement to the drop test data they are now using in the design of new joint replacement devices.

Impact and Reaction Force vs. Time