通过分析超声检测的国家与行业标准中校准试块与参考试块的结构和功能特征,结合无损检测课程中本科教学实验环节的实际教学目标,从多功能一体化的设计目标出发,设计了满足实验教学需求的试件.试件具备平面、圆柱面、矩形槽、平底孔、横孔、短横孔等典型特征,并避免了检测时试块功能特征之间的相互干扰,可用于直探头、斜探头及超声检测设备的分辨力、灵敏度、水平线性、垂直线性、斜探头入射点等的测定,以及模拟缺陷的检测.

In order to meet the needs of virtual reproduction of mandibular motion in medical field,a tracking and simulation system of mandibular movement based on single binocular vision system is proposed.The system consists of two CCD cameras and a DLP3000 projector.Using the structure of binocular vision measurement system,it has a measurement system based on binocular vision triangulation reconstruction and two systems of monocular structured light based on phase shift method.The calibration method adopts one position to calibrate multi positions,and it realizes the data registration and fusion.Getting the mandibular movement and jaw pad teeth of point cloud data,the standard point cloud model is regstraed with the acquired point cloud data,and import it into the simulation system.The experimental results show that this system achieves high precision virtual reproduction of the mandibular movement,which lays the foundation for the application of the next medical field.

Drilling experiments of titanium alloy Ti6Al4V were conducted. Taking the speed and feed as the process variables, a set of experimental cutting forces are obtained and compared. From the experimental results it is concluded that within the experimental extent the thrust force and torque of drilling process rises with the feed rate. The lower spindle speed resulted in the greater amount of thrust. Feed rates have greater influence on the thrust force than the spindle speed. The combination of greater feed rate and lower spindle speed results in the maximum amount of thrust. However, combination of greater feed rate and spindle speed resulted in maximum amount of torque.

Because of the specificity of the mechanical properties of carbon fiber reinforced plastics (CFRP) and titanium alloy stacks, more and more attention is given to it in the aerospace manufacturing industry, so the research on cutting force for drilling stacks becomes always a hot topic. The primary cutting edge is divided into a series of elements and the cutting process is simplified to oblique cutting of every element. The mathematical analysis is used with experience to build the drilling force prediction model for standard twist drill and the cutting force is simulated with MATLAB / Simulink. Comparing the results of simulation and experience, it comes to the conclusion that the prediction model above is effective.

工业机器人大多是由一系列连杆通过关节串联在一起的结构,因此刚性不足.进行制孔时,机器人容易受到切削力的作用产生振颤,影响到制孔精度.为进行机器人制孔过程动力学仿真,考虑机器人关节的柔性,将其简化成有刚度、阻尼的线性扭转弹簧,建立机器人动力学模型;采用数学分析和经验结合的方法,建立标准麻花钻的钻削力预测模型.以钻削力为末端外载荷,将两种模型联合,进行Simulink仿真.仅考虑制孔系统末端在钻头进给方向的动态变化,其导致进给量、钻削力的动态变化,这些将对机器人系统以及制孔质量产生影响.在某一位姿进行仿真,不同的钻削速度将会产生不同形式的关节变形以及钻削力变化,进而推测制孔系统振动效应,对提高机器人系统稳定性,提高制孔质量和精度有一定指导意义.

This paper presents analytical models dealing with time domain cutting forces and the time and frequency domain dynamics of helical milling operations. The cutting forces both on the side-cutting edges and on the end-cutting edges along the helical feed path are modelled by considering the tangential and the axial motions of the tool. The dual periodicity, which is caused by the spindle rotation, as well as the period of the helical feed of the cutting tool has been included. The models of the machining process dynamics and of the chatter stability problems are decomposed into two parts: the critical axial depth of cut, and the critical radial depth of cut, both of which are solved. The dynamics model allows the selection of processing parameters, including axial cutting depth, radial cutting depth, and spindle rotation velocity in the chatter-free zone and the prediction of chatter vibrations during helical milling. Experiments have also been performed for real machining observations in order to verify the chatter-free zone obtained from the analytical model.

Helical milling operations machining process parameters planning approach were pro‐posed based on analytical time domain cutting forces models and time and frequency domain dynamics models of the operations .The cutting forces both on the side cutting edges and on the bottom cutting edges along the helical feed path were defined by considering the circumferential feed motion and the axial feed motion of the tool .The dual periodicity which was caused by the spindle rotation ,as well as the period of the helical cutting fool feed was included .Both the critical axial cutting depth and the critical radial cutting depth were solved .The cutting force model and dynamics model allowed the planning of machining process parameters including axial cutting depth ,radial cutting depth ,circum‐ferential feed rate ,axial feed rate and spindle rotation velocity in the chatter free zone during helical milling .Experiments were also performed in order to verify the planned machining process parameters for helical milling .No chatter occurred during the experiments .The accuracy and precision of the ma‐chined surface ,including surface roughness ,roundness and cylindricity ,are equivalent to the boring process .

High power thermal source such as laser beam has been applied for softening the difficult-to-machine materials when it is combined with conventional machining processes, such as milling. Analytical model and finite element method (FEM) model for the simulation of the laser assisted milling process are presented. In the analytical model, the general solution of the temperature distributed for a moving heat source in a semi-infinite body is calculated. The impact of the initial temperature to the cutting forces are taken into account, based on Johnson-Cook material constitutive law. In the FEM model, Johnson-Cook material constitutive law and Johnson-Cook material failure criteria have been implied within the material model. Sequentially thermo-mechanical coupling FEM approach is adopted. Gauss laser beam heating process is modelled as heat flux load scanning along the workpiece material surface and the temperature field with respect to time has been simulated. Then the temperature distribution about a series of discrete time steps has been taken as the initial temperature condition to the corresponding machining process simulation steps. Finally, the laser assisted titanium alloy milling simulation results of the analytical model, the FEM model, and the published experimental results have been compared. That shows the FEM model predicting cutting zone temperature, stress, and cutting forces accurately and elaborately, while the analytical model predicting cutting forces and cutting zone temperature efficiently to a certain accurate extent.

Thermal energy sources have been applied for softening the difficult-to-machine material when it is combined with conventional machining processes. Cutting forces has been reduced during the process. To investigate the plastic deformation property of workpiece materials heated by thermal sources, and its influence to the cutting forces, the analytical model of orthogonal cutting is established. The impact of cutting speed and initial temperature of the shear banding to the cutting forces are taken account of, based on adiabatic shear banding model and Johnson-Cook material constitutive law. The shear banding average shear stress failure criteria has been proposed to decide the fracture between workpiece and chip. Simulation has been carried out and compared with experimental data of laser-heat assisted titanium alloy milling, showing good agreement.

Due to the low stiffness of the serial drilling robot,when the serial robot is drilling,some displacement of the robot will appear.Stiffness of the serial drilling robot plays a crucial role in hole quality.And therefore a method of identifying joint stiffness of robot with six rotation freedom have been researched.The link of the robot are assumed to be rigid.Using DenavitHartenberg-modified(D-H-m)method to establish the drive shaft coordinate system.And the Jacques than matrix of the robot with six rotating freedom have been acquired by using differential transformation method.Identifying joint stiffness considering the displacements of the robot end-effector for a applied load,and it acquires the stiffness matrix of the robot.Finally the three-dimension model of robot have been established,the assumption have been verified with finite element method.

Based on Johnson-Cook failure criterion,it establishes 2D orthogonal TC4 cutting model of the coupled temperature-mechanical stress,analyzes the distribution of surface residual stress under different cutting conditions.The results show that the surface residual stress of workpiece is tensile stress.Along the depth direction,the tensile stress is transformed to the compressive stress.Surface residual stress increases with the in-creasing of the cutting speed,in a certain range of rake angle,the tensile residual stress on the workpiece surface increases with rake angle at first and decreases subsequently,while decreases with the in-creasing of the relief angle.All cutting conditions have little influence on the thickness of the residual stress layer.

<正>飞机结构件的寿命在一定程度上决定了飞机整体的寿命。为了满足飞机高寿命的要求,可以通过各种技术改善结构件连接点的技术状态,如连接孔的孔径精度、表面质量、配合性质等。在飞机自动化柔性装配技术中,采用机器人实现飞机部件乃至整机制造中的钻孔和铆接,是提高钻孔和铆接质量的有效技术途径。国外自20世纪90年代起,就已经大规模开展飞机自动化装配技术的研究。采用数字化自动钻铆装备实现飞机大型构件的装配和联接是提高装配效率和质量的有效途径,也是航空制造业的重要发展趋势。

Simulations of cutting mechanism and drilling vibration of robot drilling are conducted by using FEM analysis software Deform-3D and Abaqus.The simulations of robot drilling forces are conducted and empirical formulas of robot drilling are fitted based on the data obtained from simulations.The simulations of robot mode,stiffness and damping ratio are conducted and proper robot drilling parameters are collected by the theory of chatter.The results indicate that the finite element method can efficiently solve the problem of robot drilling parameter optimization.

The kinematics of helical milling on a three-axis machine tool is first analysed. An analytical model dealing with time domain cutting forces is proposed in this paper. The cutting force model is established in order to accurately predict the cutting forces and torque during helical milling operations as a function of helical feed, spindle velocity, axial and radial cutting depth and milling tool geometry. The forces both on the side cutting edges and on the end cutting edges along the helical feed path are described by considering the tangential and the axial motion of the tool. The dual periodicity which is caused by the spindle rotation, as well as the period of the helical feed of the cutting tool, has been included. Both simulation and experiments have been performed in order to compare the results obtained from modelling with experiments.

In this paper Finite element methods (FEM) and cutting experiment were used to investigate the machinability of titanium alloy ZTC4 (cast Ti6Al4V). Machinability was evaluated as cutting force, temperature, and surface roughness. Two-dimension (2D) and three-dimension (3D) machining process FEM models were established. Material constitutive applied Johnson-Cook model synthesizing elastic and plastic deformation. Chip separated criteria adopted arbitrary Lagrangian Euler (ALE) algorithm. Heat generation source included the rake face chip flow under conditions of seizure and chip/tool friction, clearance face tool/workpiece friction. 3D discrete milling tool was modeled and the milling process was simulated. The ZTC4 milling experiments were designed and carried out with same cutting conditions of the 3D FEM simulation. The results of FEM simulation and the experiment were compared and analysed. The influences of the machining variables to the machinability of ZTC4 were discussed.

Helical milling operations are used to generate or enlarge boreholes by means of a milling tool. The bore diameter can be adjusted through the diameter of the helical path. The kinematics of helical milling on a three axis machine tool is analysed firstly. The relationships between processing parameters, cutting tool geometry characters with machined hole feature are formulated. The feed motion of the cutting tool has been decomposed to plane circular feed and axial linear motion. In this paper, the time varying cutting forces acted on the side cutting edges and end cutting edges of the flat end cylinder miller is analysed using a discrete method separately. These two components then are combined to produce the cutting force model considering the complicated interaction between the cutters and workpiece. The time varying cutting force model describes the instantaneous cutting force during processing. This model could be used to predict cutting force, calculate statics deflection of cutter and workpiece, and also could be the foundation of dynamics model and predicting chatter limitation of the helical milling operations. Keywords—Helical milling, Hole machining, Cutting force, Analytical model, Time domain

According to the weak stiffness and unmachined characteristic of the Ti-alloy structure part,a process of low immersion milling is proposed.Based on the stability prediction theory for low immersion milling,the stability lobe is drawn.Reasonable machining parameters are selected to avoid the chatter in milling.The paper provides an example for the application of this theory.

The flexible technological equipment of railway freight cars is a complex and large-scale system.The automatic control technology is one of its key technologies.According to the working condition and characteristic of the flexible technological equipment,a three-layer control structure based on Profibus is put forward.The control flow is also analyzed.Then the function and composition of main control elements are discussed.A drive method with "motor and elevator" is put forward.The positioning technology with PLC is researched.Based all of these the control system is integrated.Applied these technologies the flexible technological equipment for the frame of railway freight cars manufacturing is developed.The operation results show that the control system is reliable and the control accuracy is satisfied.

To solve problems such as cumbersome testing process of brake system parts and many testing equipments,flexible closed-loop control system was developed to test key parts in brake system.At first,general control platform was established based on flexible closed-loop control system,and then mathematical model of flexible closed solenoid valve was set up.Furthermore,main influencing factors to the testing bench's precision were analyzed and some measures were taken to improve testing accuracy.By using event-driven,software reuse and component connections,testing software for brake system parts performance was developed.Based on parts input,control mode and technical index of brake system,flexible closed-loop control system was used on testing bench of brake system parts.Finally,the results demonstrated that the flexible closed-loop control system was both effective and reliable with good applicability.

In this paper Finite Element Methods (FEM) were used to simulate the ultrasonic vibration Orthogonal cutting of titanium alloy Ti6Al4V. Machining conditions were similar to those used for manufacture. Material constitutive applied Johnson-Cook model combining elastic and plastic deformation, the material hardening for extreme shear strain and strain rate, material softening for adiabatic shear of chip flow-zone. Chip separated criteria adopted arbitrary Lagrangian Euler algorithm (ALE). Heat sources included the rake face chip flow under conditions of seizure and chip/tool friction, clearance face tool/workpiece friction. Thus, the orthogonal ultrasonic vibration machining of Ti6Al4V FEM models were established. The simulation results included the chip formation, the cutting force/stress and temperature distributions through the primary shear zone and the chip/tool contact region. The cutting force, cutting temperature of the ultrasonically and conventionally machining were compared. The reasons of the decrease of chip deformation coefficients, cutting force and temperature and the increase of shear angle in ultrasonic machining were discussed.