Brain Tissue Mechanical Properties And Drawing Material Machinery Research

Drawing material is initial stage of the pathological research and forensicidentification. Whether the quality of drawing material is good or not has a seriousinfluence with the making process quality of tissue pathological section and theaccuracy of identification results. And whether the thickness of drawing sample isuniform or not has a serious impact on the work efficiency of forensic identificationand the description accuracy of pathological problems. However, almost all theforensic experts and related medical workers in the world use kitchen utensils tocutting when they draw materials on human tissues through investigation and noveltysearch. With continuously rising of medical disputes and highly increasing ofaccuracy requirements of autopsy identification results, special machine for drawingmaterial will be more and more popular. Therefore, to carry out the research ofdrawing material technology and mechanics on human tissue will provide morescientific methods to find out the cause of death and will provide more effectivescientific evidence for medical judicial identification.Consequently, this paper studies mechanical properties and drawing materialmachine of brain tissue on three aspects including biomechanical experiment, finiteelement simulation analysis and mechanical design to ensure that design of themachinery can effectively improve the quality of sliced brain, and to ensure that thethickness of cut sections is uniform. And thus provides more technical help forrelevant police personnel and medical practitioners. The main research contents andresults are as follows:First, this paper analyzes the structure characteristics of human brain tissue andmechanical properties of brain tissue effected by two kinds of fiber composition. Nextthis paper determines the method to increase brain tissue stiffness, contrastivelyanalyzes the fixing agent and the fixed principle of Faure Marin’s reagent, anddiscusses the5methods of improving material cutting quality.Second, this paper designs the fixtures required by experiments and does a seriesof biomechanics experiments using these fixtures, including time lag test, ultimatetensile strength test, stress relaxation and shear strength test. These experimentscontrastively analyses the differences and characteristics between with rupture of thecerebral convolutions and without rupture of the cerebral convolutions, and analysesidentification method when the specimen and fixture are separated in tensile test. Besides this paper fits the stress-strain relation function, constructs the stressrelaxation function, calculates the numerical range of tensile strength, shear strengthand elastic modulus, finds that the proportion of collagen fibers in the brain tissueare higher than elastic fibers.Then, The cutting principle of brain tissue and cutting force and energy during theactual cutting are discussed in detail. Two constants of Mooney-Rivlin model utilizedtensile test data are identified. Cutting dynamic simulation analysis of brain tissuemodel is conducted with the finite element method and experiment design. Simulationresults find that blade thickness has a significant influence on the strain effect of braintissue. The strain regression function is obtained by regression analysis, and thus threemain cutting parameters are optimized.Finally, this paper describes the general principles of the design of cuttinginstruments. The drawing material machine and its main mechanism are analyzed byusing the mechanical design software.The results of this study on the one hand can contribute to understanding thestatic and cutting dynamic characteristics of brain tissue. On the other hand, theresults can not only avoid stress concentration during actual operation process ofdrawing material, completely solve the problem that the thickness of samplingsections is not uniform, but also carry out the accurate description of samplingposition.