Simulation of Strain Waves in Impact Driven Tools: Towards Virtual Testing of an Adjustable Substitute Workpiece

Workpieces used for testing impact driven tools, such as hammer drills, have
significant drawbacks. Natural materials, for example, are inhomogeneous, and
existing substitute workpieces cannot be adjusted to mimic different
applications. Developing a substitute workpiece that allows reproducible,
adjustable and realistic testing typically requires extensive physical testing,
which is time consuming and resource intensive. Virtual testing is an alternative,
but this approach relies on accurate determination of the load applied to the part.
The problem addressed in this contribution is that there is no known model
capable of simulating strain waves generated by impact mechanisms. To address
this, a procedure is presented for setting up and evaluating a finite element
simulation based on experimental measurements to obtain the load in the form
of strain waves. Based on this procedure, a simulation was set up on a hammer
drill and evaluated to show that it is capable of simulating the strain waves. The
comparison between the measured strain and the simulated strain showed that
the simulation achieved a relative root mean square error of less than 20% and a
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coefficient of determination of more than 85%, which is assumed a sufficient fit.
It has therefore been shown that a FEM simulation based on measurements using
the EPTA method can reproduce the strain waves on the tool of an impact driven
tool.