Analysis Of Geometrical Characteristics And Soil Cut Function Of Claws Of Mole Rats

Soil-burrowing animals have excellent living ability and biological systems through the evolution upon millions of years for adapting their living surroundings. These soil-burrowing animals, such as pangolin, dung beetle and mole cricket. have better functions in biomechanics, which resulted in a lower cutting resistance and a reduced soil adhesion. Mole rat, a typical soil-burrowing animals, is called as"living grab"because its high working efficiency during digging precedure. The claws of mole rats are its main digging or cutting organs. It is important to understand the geometrical and mechanical characteristic of the claws of the mole rat.The claws of mole rat(Talpa moschatus)were examined. The geometrical characters of the claws were analyzed using optic stereoscope. The reversing engineering method was used for measuring the digital data and reconstructing the CAD models of the claws. The profiles of the claws were quantitatively analyzed by the software of reversing engineering. The finite element method (FEM) was utilized to simulate the interaction of the claws agaisnt soil.A typical claw was determined as a research object based on the observation and analysis of the claws of mole rats using a stereoscope.A 3D laser scanner was used to measure the digital data of the claws of the mole rat. Three small steel balls with a radius of 1.47mm were utilized during the measurement to ensure that the data obtained from different scanning angle and at different time can be unified. The comparative analysis was conducted for the different data point clouds with varied scanning steps and the scanning direction.In order to obtain the holistic shape data obtained through the appropriate scanning step and scanning angle. A scanning step of 0.05mm was used.The scanning data point clouds were processed using special software of reverse engineering. The procedure included deleting error points manually, smoothing the scanning data and sampling characteristic points from the scanning point clouds. Gaussian filter was used for smoothing and Chordal deviation method was used for sampling. Based on the reconstruction model of three placements, the scanning data obtained from different angle and different direction were positioned and conformed. The point-curve-surface method was used to reconstruct the geometrical configuration of the claws of the mole rat. Then, some specific methods were used to evaluate the quality of the reconstructed geometrical surface, including the difference between the original point clouds and the reconstructed surfaces, the surface smoothness and the multi-surface continuity.Several cross-section data points were extracted from the scanning point clouds of the claws of the mole rat. The cross-section data points of e claws of the mole rat were extracted along longitudinal direction and transverse direction respectively using the reverse engineering software. The Least Square fitting method was used to analyze the cross-section data for fitting mathematical models and the fitted curves were expressed by Gaussian equations and Polynomial equations respectively. The fitting precisions were expressed through comparative analysis. The curvature and second derivative values of the fitted curves were calculated and the graphs were plotted and analyzed.Nonlinear analysis was taken in the finite element method. The main steps includes: changing the type of the reconstructed model into IGS format, and then input it into the software Pro/E to form an entity and draw the soil model. The models of the claws and the soil used were inputed to software ANSYS by changing the format into IGES type. At this time, the model of interaction between the claws of mole rat and soil was obtained. In the software of ANSYS, the element type, material and some parameters were defined, the model was meshed, limited conditions were added and resolution parameters were setup.Afterwards, the procedure of the interaction of the claw against soil can be simulated. The simulation results were analyzed through post-process functions of ANSYS. 3D disturbing nephogram and 3D stress nephogram were obtained.This research works, such as analysis of the shape and configuration and thier geometrical digital data, reconstructed 3D model and simulation and the finite element analysis of the procedure of the interaction of the claws against soil. It would provide certain foundation for improving the designof the soil-cutting tool.