Abstract
Abstract Vibration measurement and signal analysis methods are common to evaluate the functionality and characteristics of technical components in different industrial and scientific areas. Modal analysis for example is a standard method to characterize the dynamic behavior of a structure and enables the development of validated bone models. The state of the art of analyzing bone structures does not include the modal damping, although it has a significant influence on the dynamic characteristics. Within the presented investigations, the modal analyses have been performed contactless with respect to excitation and response acquisition, which implies that there are no influences of shakers or sensor couplings. Therefore, an automatic impulse hammer and a 3D Scanning Laser Doppler Vibrometer were used for excitation and response detection. Various supports of the test specimens, surface pretreatments, excitation points and excitation impulses were examined to optimize the measurement setup and process. Experimental modal analysis data were analyzed by curve fitting methods to determine the modal parameters. To evaluate different structures and effects of damping, 3D printed artificial bones and animal in vitro bones were used to perform the measurements. To produce the cortical layer of the artificial bone models, volume models were generated based on medical image data and printed by polyamide-based selective laser sintering. The cancellous bone was represented by different foam fillings for the artificial bones. Thereby, the variation of the porosity was achieved by using different mixing ratios of polyurethane foam and hardener. Furthermore, the modal damping parameters were determined from the measurement of animal bones. The measurement time was optimized during the practical implementation of the parameter determination to minimize the influence of drying and decomposition processes on the measurement results.
Highlights
Simulations of a surgery on human specimens offer the opportunity to practice complex procedures in the advanced training of physicians
The challenges in terms of modal analyses using contactless excitation and response acquisition are discussed for bone measurements
Afterwards, three various synthetic bones are compared to demonstrate the possibility of the modification of modal parameters
Summary
Simulations of a surgery on human specimens offer the opportunity to practice complex procedures in the advanced training of physicians. The occurring fractures are not comparable (cf [1]) and in particular, the elastic properties and strength of common bone simulant material are described as insufficient [2]. Advanced models, such as the customized bone models of the distal femur of Wähnert et al [3] or the 3D-printed spine models of Hao et al [4] do not provide satisfactory results at present
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