Finite Element Simulation And Experiment Of Muscle Soft Tissue In Puncture Process

Cytopathology is the main method to diagnose cancer.The first step is to obtain tissue samples of target organs.Because of its advantages,the first choice of clinical tissue samples is biopsy.Puncture biopsy is a method that uses hollow puncture to insert target soft tissue,cut off a small amount of tissue samples and save them in the cavity of needle core.In clinical practice,the sampling accuracy and efficiency of biopsy are not satisfactory.It is often necessary to sample several times to obtain a more ideal tissue sample.It can be seen that with the development of technology,the introduction of puncture simulation into minimally invasive surgery improves the accuracy and success rate of puncture operation to a certain extent,reduces the pain of patients during the operation,and speeds up the rehabilitation process of patients.In this thesis,the finite element simulation of muscle tissue puncture process is studied,the precise puncture simulation model is established,and the puncture parameters are optimized,which greatly improves the accuracy of muscle tissue puncture simulation process,and provides powerful data and model support for the contact between muscle tissue and instruments in virtual surgery.Firstly,the constitutive equation and parameters of muscle tissue were selected.Three typical constitutive equations based on invariant model and one based on tensile model are selected for comparison among a variety of hyperelastic models.Through the improvement of the fixture of universal testing machine and the proper treatment of sample pieces,the tensile experiment,compression experiment and uniaxial stress relaxation experiment of muscle tissue are carried out respectively to obtain the stress-strain curve of muscle tissue and the stress-strain curve of muscle tissue The viscoelastic characteristic curve affected by time,and the hyperelastic and viscoelastic constitutive equations are fitted by the experimental data,and the constitutive equation suitable for muscle tissue is obtained,which provides the experimental data basis for the definition of material attributes of puncture simulation soft tissue.Secondly,aiming at the problem of sampling accuracy of biopsy,a two-dimensional finite element model of flexible needle was established to verify the accuracy of the model.Set up the puncture experiment platform,compare the simulation model of different puncture needle diameter under the same puncture speed with the experiment,and verify the correctness of the proposed puncture simulation method.The deformation,stress nephogram and simulation results of the flexible needle under different puncture parameters are compared and analyzed to achieve the purpose of reasonably planning the puncture route and improving the puncture accuracy.The results show that the diameter,speed,rotation angle and depth of the puncture needle have influence on the deformation of the flexible needle.In order to get a larger deformation path of the puncture needle in the tissue,a smaller diameter,speed and rotation angle can be used.Finally,aiming at the problem of tissue deformation in the process of puncture biopsy,a method of defining the fracture characteristics of muscle tissue material in the simulation process is proposed.The double line cohesion model is used to simulate the fracture of muscle tissue and puncture needle in contact,and a three-dimensional puncture finite element model is established to analyze the deformation of muscle tissue.According to the actual shape of puncture needle and muscle tissue,the three-dimensional finite element model of puncture is defined,and the reasonable contact characteristics,fracture criteria and mesh division between cutter and muscle tissue are set up.The simulation of puncture of muscle tissue under different puncture diameter,puncture depth and puncture speed is carried out,and the stress nephogram and reaction force under different parameters are compared and analyzed.According to the simulation results,in a certain range,choosing a smaller needle diameter and a larger puncture speed can effectively control the soft tissue deformation during the puncture biopsy operation,so as to achieve the purpose of wound healing and pain relief.