Three-dimensional land FD-CSEM forward modeling using edge finite-element method

A modeling tool for simulating three-dimensional land frequency-domain controlled-source electromagnetic surveys,based on a finite-element discretization of the Helmholtz equation for the electric fields,has been developed.The main difference between our modeling method and those previous works is edge finite-element approach applied to solving the three-dimensional land frequency-domain electromagnetic responses generated by horizontal electric dipole source.Firstly,the edge finite-element equation is formulated through the Galerkin method based on Helmholtz equation of the electric fields.Secondly,in order to check the validity of the modeling code,the numerical results are compared with the analytical solutions for a homogeneous half-space model.Finally,other three models are simulated with three-dimensional electromagnetic responses.The results indicate that the method can be applied for solving three-dimensional electromagnetic responses.The algorithm has been demonstrated,which can be effective to modeling the complex geo-electrical structures.This efficient algorithm will help to study the distribution laws of3-D land frequency-domain controlled-source electromagnetic responses and to setup basis for research of three-dimensional inversion.

Corner Transition Toolpath Generation Based on Velocity-Blending Algorithm for Glass Edge Grinding

Sharp corners usually are used on glass contours to meet the highly increasing demand for personalized products,but they result in a broken wheel center toolpath in edge grinding.To ensure that the whole wheel center toolpath is of G1 continuity and that the grinding depth is controllable at the corners,a transition toolpath generation method based on a velocity-blending algorithm is proposed.Taking the grinding depth into consideration,the sharp-corner grinding process is planned,and a velocity-blending algorithm is introduced.With the constraints,such as traverse displacement and grinding depth,the sharp-corner transition toolpath is generated with a three-phase motion arrangement and with confirmations of the acceleration/deceleration positions.A piece of glass with three sharp corners is ground on a three-axis numerical-control glass grinding equipment.The experimental results demonstrate that the proposed algorithm can protect the sharp corners from breakage efficiently and achieve satisfactory shape accuracy.This research proposed a toolpath generation method based on a velocity-blending algorithm for the manufacturing of personalized glass products,which generates the transition toolpath as needed around a sharp corner in real time.

Three-Dimensional Exact Solution for Dynamic Damped Response of Plates with Two Free Edges

A three-dimensional state space method has been developed for the calculation of dynamic response of plates with two free edges and two simply supported edges.A complex damping model was introduced, then the exact solutions which satisfy all the governing equations and boundary conditions were obtained.In order to overcome the difficulty of satisfying all the stress conditions at free edges, the displacement functions of free edges were assumed.The boundary conditions were strictly satisfied when the convergence rate was good.The computing time was evidently less than that of finite element method.The comparison of the solution with those of finite element method show that there is an excellent agreement for displacements.When the imaginary parts of normal stress deviated, the finite element results showed existence of shear stresses at top and bottom surfaces, and the boundary conditions of FEM model were not strictly satisfied.

Design Theory of Full Face Rock Tunnel Boring Machine Transition Cutter Edge Angle and Its Application

At present, the inner cutters of a full face rock tunnel boring machine (TBM) and transition cutter edge angles are designed on the basis of indentation test or linear grooving test. The inner and outer edge angles of disc cutters are characterized as symmetric to each other with respect to the cutter edge plane. This design has some practical defects, such as severe eccentric wear and tipping, etc. In this paper, the current design theory of disc cutter edge angle is analyzed, and the characteristics of the rock-breaking movement of disc cutters are studied. The researching results show that the rotational motion of disc cutters with the cutterhead gives rise to the difference between the interactions of inner rock and outer rock with the contact area of disc cutters, with shearing and extrusion on the inner rock and attrition on the outer rock. The wear of disc cutters at the contact area is unbalanced, among which the wear in the largest normal stress area is most apparent. Therefore, a three-dimensional model theory of rock breaking and an edge angle design theory of transition disc cutter are proposed to overcome the flaws of the currently used TBM cutter heads, such as short life span, camber wearing, tipping. And a corresponding equation is established. With reference to a specific construction case, the edge angle of the transition disc cutter has been designed based on the theory. The application of TBM in some practical project proves that the theory has obvious advantages in enhancing disc cutter life, decreasing replacement frequency, and making economic benefits. The proposed research provides a theoretical basis for the design of TBM three-dimensional disc cutters whose rock-breaking operation time can be effectively increased.

Analytical solutions for a uniformly loaded circular plate with clamped edges

A bi-harmonic potential function was constructed in this study. Love solution was employed to obtain analytical solutions of uniformly loaded plates with two different types of clamped edges. The treatment of clamped boundary conditions was the same as that adopted by Timoshenko and Goodier (1970). The analytical solution for the first type of clamped boundary condition is identical with that obtained by Luo et al.(2004), and the solutions for both types were compared with the FEM results and the calculations of thin plate theory.

基于驻留时间控制的压气机叶片前缘砂带磨削研究

提出了一种面向叶片前缘廓形精准控制的机器人砂带磨削加工方法.以轴流压气机叶片为研究对象,结合半赫兹接触理论和有限元仿真获取了柔性磨具和叶片前缘的接触区域内的应力分布,基于Preston方程求解材料去除函数.遍历刀位点对控制点的磨削深度,建立全局材料去除矩阵,搭建驻留时间求解非线性方程组.采用带有阻尼因子的Tikhonov正则化消除大型稀疏病态矩阵对求解精度波动的影响,将所求驻留时间转换为对应刀位点的进给速度,生成机器人加工代码.磨削试验结果表明,基于驻留时间控制的机器人砂带磨削方法能够实现给定允差范围内叶片前缘廓形的精准加工,型面误差可以控制在0.02mm以内.

激光改性超声振动磨削制孔加工参数优化分析

为提升孔径出孔端面的品质及其控制精度,在超声振动辅助下针对硬质材料激光改性磨削孔加工参数的优化进行试验与研究。通过运用旋转超声方法,显著提高加工效率,有效克服硬脆材料孔加工难度大的问题。为评判孔出口的质量水平(Hd值),分析了孔出口端面崩边区域的范围,并实际测量了孔截面的面积比,进一步探讨了激光改性磨削工艺参数对Hd值的影响。通过试验综合分析,确定最佳的激光改性磨削工艺参数范围:主轴转速为14000~16000 r/min,进给速度为0.5~0.7 mm/min,振幅为7~8μm。与传统的激光加工相比,在最优参数下超声辅助激光改性加工后的表面质量显著提高,划痕大幅减少,显著提升了加工质量。这项研究对于提高硬质材料激光改性磨削的质量具有重要的指导意义,并易于在实际生产中推广应用。

微晶玻璃超声辅助磨削制孔工艺参数对表面质量及出口崩边的影响研究

为研究微晶玻璃超声辅助磨削制孔过程中工艺参数对小孔内壁表面质量及出口崩边的影响,在超声振幅3μm、频率20 kHz条件下,采用有限元方法分析了加工过程中磨削力随着主轴转速、进给速度等工艺参数变化的规律。利用五轴加工机床分别开展了超声辅助磨削与普通磨削的加工试验,对比了工件表面粗糙度及出口崩边状况。结果表明:相同工艺参数下,超声辅助磨削相较于普通磨削,可显著减小磨削力,加工小孔的崩边尺寸更小,工件表面质量更好。

一种应用于碳化硅全自动减薄机的定位巡边方法

针对带平边的碳化硅晶片,在放到承片台上时,需要与承片台的平边重合,因此提出一种应用于碳化硅减薄机的定位巡边方法。此方法先在定位台上夹爪粗定位,然后旋转碳化硅晶片通过巡边传感器确定晶片的平边,最后旋转到设定的与承片台恰好重合的角度,完成定位巡边。此方法通过平边晶片与平边承片台的重合,使得吸附晶片的真空最大化,大大提升后续的磨削精度。通过磨削效果的对比,TTV由原来的4.4μm提升到1.5μm。

机器人自动磨抛飞机蒙皮切边去除深度工艺

根据Preston理论建立蒙皮切边材料去除深度摸型,确定影响材料去除深度工艺参数,获得工艺参数对材料去除深度的影响规律。采用单因素实验法通过Ansys有限元软件仿真和机器人磨抛实验验证模型的正确性,设计正交试验对工艺参数进行优化使达到预期去除深度。研究结果表明,工艺参数对材料去除深度的影响程度从大到小依次为接触力、百页轮转速、进给速度,经验证优化的参数组合去除材料深度达到预期要求,证明该模型的正确性。

可转位刀片周边过渡刃建模及磨削刀位计算方法

基于空间曲面成型理论,结合实际可转位刀片周边刃磨削系统,给出可转位刀片数学模型导入流程;提出一种可转位刀片周边圆弧过渡刃磨削刀位计算方法,实现非标可转位刀片的周边刃磨削代码的自动生成。通过仿真实验模拟加工,验证了建模方法的正确性。

立铣刀刃角的径向机器视觉在机测量

为提高企业磨削铣刀时的效率,对铣刀端齿研磨角度与铣刀螺旋线之间的关系进行研究,提出了一种基于机器视觉技术的立铣刀端齿磨削时刃角在机测量方法,通过铣刀径向拍照获取图像实现刀尖角度在机测量。采用模板匹配粗定位周刃交点位置确定ROI区域,通过亚像素轮廓提取,获取铣刀周刃交点的精确坐标,并根据该坐标与端面位置偏移量计算铣刀刀尖的角度。实验结果表明,该系统最大绝对误差为0.094°,且平均计算时间为0.086 s,符合企业误差不超过0.1°的要求。

刀剪机器人开刃砂轮修整补偿系统

针对目前刀剪开刃生产效率低、质量不稳定等问题,根据机器人开刃工艺特点,设计刀剪机器人开刃砂轮修整补偿系统。介绍了这一系统的工作原理,分析了机械机构。通过数控系统进行砂轮磨损自动修整,利用数据传输与机器人控制实现数据同步,达到砂轮修整值与机械臂补偿值一致。试验结果表明,刀剪机器人开刃砂轮修整补偿系统以修整砂轮代替补偿砂轮,解决以往砂轮磨损补偿方法的不足,能够可靠保证机器人连续开刃精度的一致性,有效提高生产效率。

船舶异形钢板自由边双面打磨装置设计

为提高船舶生产过程中对船用钢板打磨的生产效率,设计一种自动化装置,用于船舶异形钢板自由边打磨,通过3D相机技术和计算机视觉算法实现高精度的工件外轮廓信息收集和处理。该装置具备多项自动化功能,包括工件抓取、空间定位和双面打磨处理,实现全面自动化操作。研究成果显示,该装置能显著提高生产效率,实现了船舶异形钢板自由边打磨处理工序的全面自动化,提升船舶建造领域的自动化水平,对行业具有重要意义。

Effect of machining parameters on edge-chipping during drilling of glass using grinding-aided electrochemical discharge machining （G-ECDM）

The problem of eliminating edge-chipping at the entrance and exit of the hole while drilling brittle materials is still a challenging task in different industries. Grinding- aided electrochemical discharge machining （G-ECDM） is a promising technology for drilling advanced hard-to-ma- chine ceramics, glass, composites, and other brittle mate- rials. Edge-chipping at the entrance of the hole can be fully eliminated by optimizing the machining parameters of G-ECDM. However, edge-chipping at the exit of the hole is difficult to eliminate during the drilling of ceramics and glass. This investigation suggests some practical ways to reduce edge-chipping at the exit of the hole. For this pur- pose, a three-dimensional finite element model was developed, and a coupled field analysis was conducted to study the effect of four parameters, i.e., cutting depth, support length, applied voltage, and pulse-on time, on the maximum normal stress in the region where the edge- chipping initiates. The model is capable of predicting the edge-chipping thickness, and the results predicted by the model are in close agreement with the experiment results. This investigation recommends the use of a low voltage and low pulse-on time at the hole entrance and exit when applying G-ECDM to reduce the edge-chipping thickness. Moreover, the use of a full rigid support in the form of a base plate or sacrificial plate beneath the workpiece can postpone the initiation of chipping by providing support when the tool reaches the bottom layer of the workpiece, thereby reducing the edge-chipping thickness.

硬质合金弧面磨削方法试验研究

通过分析单颗磨粒运动轨迹、单颗磨粒工件接触面积和弧面磨削走磨法砂轮动态有效磨刃数之间的关系,建立了弧面磨削走磨法磨粒的运动轨迹和磨削动态有效磨刃数Nd方程,并利用试验验证了弧面磨削走磨法的有效性。结果表明:在同等磨削条件下,采用弧面磨削走磨法单件产品的加工时间是成形磨削法的37.5%,弧面磨削走磨法砂轮保持性是成形磨削法的2.3倍,弧面磨削走磨法在硬质合金弧面磨削加工方面有较大优势。

YAG晶体自旋转磨削过程崩边尺寸模型

YAG晶体具有高脆性和高硬度的特点,加工过程中容易产生边缘崩碎,严重影响晶体元件的使用精度和寿命。基于划痕断裂力学模型建立了考虑应变率效应的YAG晶体自旋转磨削过程工件崩边尺寸理论模型,并开展YAG晶体自旋转磨削实验对理论模型的可靠性进行了验证,同时分析了磨削工艺参数对崩边尺寸的影响规律。结果表明:理论模型预测结果与实验结果相近,模型可靠;随着砂轮转速的增加,崩边尺寸逐渐减小;随着工件转速和进给速度的增加,崩边尺寸逐渐增大。

基于机器视觉的砂轮轮廓形状检测方法

针对砂轮修整机在恶劣环境下无法对砂轮轮廓形状进行实时检测的问题,搭建了一种基于机器视觉的砂轮轮廓形状检测系统。使用基于边缘检测的背景分割算法设置ROI区域,图像在ROI内进行轮廓提取和三次样条插值补偿,获得完整的轮廓形状,再使用高斯拟合法进行亚像素边缘提取,获得更高精度的轮廓图像。实验表明:本系统可对光照变化范围在-200~150 Lux,轮廓缺失比少于25%的轮廓曲线进行完全补偿,单次图像处理用时在160ms之内,用于准确度检测的图像质量指数、像素值平方根误差、结构相似度、峰值信噪比的均值分别为0.5500、7803、7.24、0.0370,可实现加工过程中对砂轮轮廓形状的在线检测。

单颗团聚CBN磨粒磨削TC4钛合金表面创成机制

目的提出一种兼具耐磨性好、自锐性能优异的新型团聚CBN磨粒研制方法,解决单晶CBN磨粒因其力学特性各向异性而极易出现沿解理面大块破碎的问题,进而提升加工效率和磨削性能。方法利用模压成形和高温液相烧结技术,制备了综合性能优异的新型团聚CBN磨粒,探究磨粒结合界面形成机制,并通过单颗磨粒磨削TC4钛合金试验,综合对比团聚CBN磨粒与单晶CBN磨粒的磨损状态和磨痕形貌,探明团聚CBN磨粒的磨削性能优势。结果团聚CBN磨粒烧结界面新生成了TiB_(2)、TiB和TiN;优选的烧结工艺参数为800℃,保温时间为10 min;相比于单晶CBN磨粒,团聚CBN磨粒的耐磨性和锋利度显著提升,磨削加工效率和质量明显改善。结论由于团聚CBN磨粒内部微晶颗粒间金属结合剂的存在,提高了磨粒的断裂韧性,降低了因磨粒内部裂纹扩展而引起的宏观裂纹损伤深度,有效提升了磨粒的加工性能;磨削过程中随着磨粒的不断磨损,未出露的CBN晶粒逐渐参与磨削,确保了磨粒工作面有效磨粒数的动态平衡,有助于提升磨粒整体自锐能力。

基于法向恒力跟踪的船板打磨轨迹在线调整方法

机器人对船板零件自由边进行打磨时,初始打磨轨迹基于船板零件的三维几何模型生成。由于该三维几何模型与实际的船板零件存在一定偏差且船板刚性较大,文章设计了基于法向恒力跟踪控制的机器人打磨轨迹在线动态调整方法以保证自由边打磨质量。通过力位感知技术实时采集机器人打磨工具与待打磨船板零件之间的接触力信息;基于重力补偿与法向力分解算法,建立法向恒力跟踪下基于位置的阻抗控制模型以实时修整机器人的打磨轨迹,使其实时跟踪待打磨零件自由边。仿真结果表明:该方法可以很好地实现打磨轨迹的在线动态调整,使得调整后的打磨轨迹能够满足要求,保证船板零件自由边的打磨质量。