RESUMO
Objective To determine the hyperelastic constitutive equation of biological soft tissues and study the mechanical responses during the clamping process of biological tissues. Methods The destructive uniaxial tensile test was performed on fresh porcine liver and the uniaxial tension experiment was simulated in ABAQUS. The hyperelastic constitutive equation of porcine liver was determined by comparing the simulation results with the experimental data. Based on this equation, the sharp teeth-shaped and wave-shaped chucks were used to simulate the clamping process. Results The simulation results of the tensile experiment with the 4th-order Ogden model were in good agreement with the experimental data. The results of tissue clamping simulation showed that stress concentration was more likely to occur when the sharp teeth-shaped chuck was adopted. Conclusions The 4th-order Ogden model can be used to describe the hyperelasticity of porcine liver and determine the relevant para-meters. Using the sharp-shaped chuck is more likely to cause tissue clamping damage, and there is a linear relationship between tissue stress and clamping feed distance. These research findings provide references for the design of surgical clamp.
RESUMO
Objective To establish the cutting force model of biopsy needle from the aspect of cutting mechanics and to reveal the relationship between cutting force of the needle and geometry of the needle tip. Methods Based on the traditional theory of metal cutting, a mathematical model of biopsy needle geometry was established. The needle cutting edge was divided into a series of elementary cutting tools (ECTs) with varying inclination and normal rake angles. The oblique cutting experiment was performed on the soft tissue cutting setup and a functional cutting force model was developed based on these ECTs. Results The force model could predict the cutting force of biopsy needle well. When the bevel angle ξwas 30°, 45° and 60°, the experimental forces of 18 G biopsy needle were 1.33, 1.38, and 1.56 N, respectively, while the predicted values were 1.29, 1.43, and 1.52 N, respectively. The relative error was less than 5%. Conclusions This cutting force model of biopsy needle quantitatively describes the relationship between the cutting force and geometry of the needle tip. The results can be used for the design and evaluation of new needle, and preoperative planning of needle insertion trajectory.