Advanced Materials Research Vols. 139-141

Abstract: Needle deflection and soft tissue deformation are the most important factors that affect accuracy in needle insertion. Based on the quasi-static thinking and needle forces, an improved virtual spring model and a finite element method are presented to analyze needle deflection and soft tissue deformation when a needle is inserted into soft tissue. According to the spring model, the trajectory of the needle tip is calculated with MATLAB using different parameters. With the superposed element method, the two and three dimensional quasi-static finite element models are created to simulate the dynamic process of soft tissue deformation using ANSYS software. The two methods will be available for steering the flexible needle to hit the target and avoid the obstacles precisely in the robot-assisted needle insertion.

Abstract: To accurately and effectively simulate large deformation is one of the major challenges in numerical modeling of metal forming. In this paper, an adaptive local meshless formulation based on the meshless shape functions and the local weak-form is developed for the large deformation analysis. Total Lagrangian (TL) and the Updated Lagrangian (UL) approaches are used and thoroughly compared each other in computational efficiency and accuracy. It has been found that the developed meshless technique provides a superior performance to the conventional FEM in dealing with large deformation problems for metal forming. In addition, the TL has better computational efficiency than the UL. However, the adaptive analysis is much more efficient using in the UL approach than using in the TL approach.

Abstract: A simulation model of the condenser in a 600MW supercritical thermal power plant was developed by using Matlab/Simulink. The important parameters such as condenser pressure, hot well water temperature and cooling water temperature were calculated by using this model. The simulation results under different operating conditions were compared with design parameters, and the relative errors were within -0.2% and +0.2%. This shows that the simulation model developed in this paper is reasonable. The dynamic performance and off-design performance of the condenser were studied by using the simulation model, which would be useful for the optimal operation of the condenser. The model of the condenser, which was developed based on the modular modeling method, would be an important basis for the simulation of the whole power plant.

Abstract: In this paper, we propose a fast approach to simulate the dynamic behavior of skeletal muscles based on bio-mechanical and anatomical properties. In contrast to physically accurate deformation, this simulation achieves faster and better simulation of skeletal muscles, with the cost of unnoticeable visual accuracy. Internal constrains are generated to conserve linear and angular momentum which is essential for cloth self-collision. Deformation constraints are defined by using the muscle force-length relationship serve as Control Axial Curve, which constrainedly generates the active and passive force of the muscles to drive skeletal motion during the deformation process. This approach generates realistic visual effect, and manages the deformation of muscles on the basis of the bio-mechanical properties with fast speed. We have demonstrated the simulation by creating a musculoskeletal model of the upper limb.

Abstract: A two-variable nonlinear mathematical model of V-shape linear ultrasonic motor (LUSM) has been presented. The relations of LUSM speed characteristics and its control variables are nonlinear, which are serious problems for accurate speed control. This paper presents a mathematical model based on Hammerstein model, which is composed of a steady-state nonlinear part and a linear dynamics part. The steady-state nonlinear part is represented by a hyperbolic tangent function, and the linear dynamics part is represented by a first order transfer function. In order to identify the coefficients of the steady-state nonlinear function, Uniform Design was used to design experiment, the nlinfit and polyfit function of Matlab software was used to deal with the experiment results. The comparisons between the estimated speed with using the proposed mathematical model and actual speed in different conditions were conducted. Comparisons results indicate good performance of developed model with respect to the experimental data.

Abstract: In order to investigate the influence rules between the jet nozzle of fire water monitor and the jet performances, two typical jet nozzle, the spray jet and direct jet nozzle was designed to analysis the jet flow characteristics. Flow simulation of the jet nozzle was completed using fluent kits. The outlet velocity of the spray jet nozzle and direct jet nozzle were investigated in detail, and the influence rules of the nozzle structure on the outlet velocity was also discussed. The simulation results show that the steady velocity of the jet nozzle is about 34m/s that coinciding the contour magnitude, and the better extended length of the direct jet nozzle is about 50mm length that can improve the jet performances. The results can verify the reasonableness of the designed nozzle, it also can optimize the nozzle structure and increase the jet performance of the fire water monitor.

Abstract: In this work, the prediction and analysis of cutting forces in helical ball-end milling operations is presented. The cutting forces model for helical end-mills is based on the oblique cutting theory and the geometric relations of the ball-end milling process. The helical flutes are divided into small differential oblique cutting edge segments. According to the transformation relationship between the local and global coordinate system of the cutter, the differential cutting force of cutting element is obtained by two coordinate conversions from the orthogonal cutting force. The total cutting force of helical ball-end milling is the sum of the cutting force in whole cutting field of the miller. As a result, the predicted cutting forces show an agreement with the values from the cutting experiments.

Abstract: . An analytical model is developed for the prediction of residual stresses in burnishing. The model is simplified as a concentrated force pressing on elastic-plastic half-space using the solution to the Boussinesq-Flament problem. The treated material admits the elastic-plastic properties with hardening using a power law constitutive relation. Trial computation using Johnson-Cook model on AISI 1042 steel is presented and the results are verified with the experimental results given by Bouzid’s previous work. The residual stresses in the feed direction show the same trend with the experimental results while some differences still exist near the surface because of the concentrated normal force assumption and such stresses increase with the increase of burnishing force, decrease with the increase of depth and turn to zero beyond the plastic deformation boundary.

Abstract: Vibration Assisted Burnishing (VAB) is an advanced burnishing form incorporating dynamic force resulting from vibration into burnishing not only to change the loading type and contact method to greatly reduce friction and wear, but also to produce an excellent nanocrystalline surface by severe plastic deformation induced by high speed impact. The expression describing the relation between decrease of surface roughness and ball burnishing force is given. The dynamic model of ball VAB is established. The relations between VAB depth, VAB force and VAB time and their maximum values are derived, and the required maximum power of the vibration generator is then obtained. The theoretical equivalent burnishing force of ball VAB is only about 47.55% that of conventional burnishing, which prove validity of ball VAB.

Abstract: The paper designed a straw crusher device based on genetic optimization design method. Firstly, straw crusher device math model was build. Secondly, taking the cutter shaft as optimized object, the cutter shaft in the working device axis diameter, internal diameter and ratio were set as variables, and taking the lightest quality of cutter shaft as the objective function, to build the mathematical model of straw crusher. Then combined with the GA optimum design method, straw crusher optimization design model and simulation model were optimized. Lastly, the structural parameters of straw crusher and satisfactory results were get. The article improves the efficiency of design and the quality of product; it also provides a new kind of design method for agricultural machinery.