Cutting parameter optimization for one-step shaft excavation technique based on parallel cutting method

The outcome of the cutting blasting in a one-step shaft excavation is heavily related to the cutting parameters used for parallel cutting method. In this study, the relationships between the cutting parameters（such as the hole spacing L and the empty hole diameter D） and damage zones were investigated by numerical simulation. A damage state index γ was introduced and used to characterize the crushing and crack damage zones through a user-defined subroutine. Two indices, i.e., η1 and η2 that can reflect the cutting performance, were also introduced. The simulation results indicate that an optimal value of L can be obtained so that the η1 and η2 can reach their optimal states for the best cutting performance. A larger D results in better cutting performance when the L value maintains its best. In addition, the influences of the loading rate and the in-situ stress on the cutting performance were investigated. It is found that an explosive with a high loading rate is suit for cutting blasting. The propagation direction and the length of the tensile cracks are affected by the direction and the magnitude of the maximum principal stress.

Effects of Cutting Parameters on Tool Insert Wear in End Milling of Titanium Alloy Ti6A14V

Titanium alloy is a kind of typical hard-to-cut material due to its low thermal conductivity and high strength at elevated temperatures, this contributes to the fast tool wear in the milling of titanium alloys. The influence of cutting conditions on tool wear has been focused on the turning process, and their influence on tool wear in milling process as well as the influence of tool wear on cutting force coefficients has not been investigated comprehensively. To fully understand the tool wear behavior in milling process with inserts, the influence of cutting parameters on tool wear in the milling of titanium alloys Ti6A14V by using indexable cutters is investigated. The tool wear rate and trends under different feed per tooth, cutting speed, axial depth of cut and radial depth of cut are analyzed. The results show that the feed rate per tooth and the radial depth of cut have a large influence on tool wear in milling Ti6A14V with coated insert. To reduce tool wear, cutting parameters for coated inserts under experimental cutting conditions are set as： feed rate per tooth less than 0.07 mm, radial depth of cut less than 1.0 mm, and cutting speed sets between 60 and 150 m/min. Investigation on the relationship between tool wear and cutting force coefficients shows that tangential edge constant increases with tool wear and cutter edge chipping can lead to a great variety of tangential cutting force coefficient. The proposed research provides the basic data for evaluating the machinability of milling Ti6A14V alloy with coated inserts, and the recommend cutting parameters can be immediately applied in practical production.

Investigation and Mathematical Modelling of Optimized Cutting Parameters for Surface Roughness of EN-8 Alloy Steel

The work done in this work deals with the efficacy of cutting parameters on surface of EN-8 alloy steel.For knowing the optimal effects of cutting parameters response surface methodology was practiced subjected to central composite design matrix.The motive was to introduce an interaction among input parameters,i.e.,cutting speed,feed and depth of cut and output parameter,surface roughness.For this,second order response surface model was modeled.The foreseen values obtained were found to be fairly close to observed values,showed that the model could be practiced to forecast the surface roughness on EN-8 within the range of parameter studied.Contours and 3-D plots are generated to forecast the value of surface roughness.It was revealed that surface roughness decreases with increases in cutting speed and it increases with feed.However,there were found negligible or almost no implication of depth of cut on surface roughness whereas feed rate affected the surface roughness most.For lower surface roughness,the optimum values of each one were also evaluated.

A Cutting Parameter Optimization System Design Based on Mathematical Models and Databases of Parameters

To solve the problem of difficulty in selecting NC cutting parameters by the redundancy technique, a method is put forward to optimize cutting parameters based on a revolutionary mathematical model and a revolutionary cutting parameters database. By use of fuzzy inference rules, it can not only make the method itself evolved and updated, but also ensure data to be correct and feasible from the two optimization routes. Practical running and testing proved that this method can facilitate for the user to select parameters and greatly improve the processing efficiency.

基于达索平台的雄安东西轴明挖隧道BIM技术研究

为提高雄安东西轴地下明挖隧道设计效率与质量,开展基于达索平台的BIM(Building Information Modeling)设计研究。提出明挖隧道BIM设计流程,对其主体结构、围护结构、防水、接口、钢筋等进行BIM参数化设计。采用Composer软件实现BIM设计交底,并对成果数据进行集成与共享,实现从设计阶段向施工阶段精度为LOD3.5的BIM成果交付,为后续相关工程的BIM设计应用提供参考。

High speed cutting of AZ31 magnesium alloy

Using LBR-370 numerical control lathe,high speed cutting was applied to AZ31 magnesium alloy.The influence of cutting parameters on microstructure,surface roughness and machining hardening were investigated by using the methods of single factor and orthogonal experiment.The results show that the cutting parameters have an important effect on microstructure,surface roughness and machine hardening.The depth of stress layer,roughness and hardening present a declining tendency with the increase of the cutting speed and also increase with the augment of the cutting depth and feed rate.Moreover,we established a prediction model of the roughness,which has an important guidance on actual machining process of magnesium alloy.

Study on Cutting Force,Cutting Temperature and Machining Residual Stress in Precision Turning of Pure Iron with Different Grain Sizes

Pure iron is one of the difficult-to-machine materials due to its large chip deformation,adhesion,work-hardening,and built-up edges formation during machining.This leads to a large workpiece deformation and challenge to meet the required technical indicators.Therefore,under varying the grain size of pure iron,the influence of cutting speed,feed,and depth of cut on the cutting force,heat generation,and machining residual stresses were explored in the turning process to improve the machinability without compromising the mechanical properties of the material.The experimental findings have depicted that the influence of grain size on cutting force in the precision turning process is not apparent.However,the cutting temperature and residual stress of machining fine-grain iron were much smaller than the coarse grain at all levels of cutting parameters.

Comparison of two Nd:YAG laser posterior capsulotomy: cruciate pattern vs circular pattern with vitreous strand cutting

AIM： To investigate the effects and safety of neodymium： yttrium-aluminium-garnet（Nd：YAG） laser posterior capsulotomy with vitreous strand cuttingMETHODS： A total of 40 eyes of 37 patients with symptomatic posterior capsular opacity（PCO） were included in this prospective randomized study and were randomly subjected to either cruciate pattern or round pattern Nd：YAG posterior capsulotomy with vitreous strand cutting（modified round pattern）. The best corrected visual acuity（BCVA）, intraocular pressure（IOP）, refractive error, endothelial cell count（ECC）, anterior segment parameters, including anterior chamber depth（ACD） and anterior chamber angle（ACA） were measured before and 1 mo after the laser posterior capsulotomy. RESULTS： In both groups, the BCVA improved significantly（P〈0.001 for the modified round pattern group, P=0.001 for the cruciate pattern group）; the IOP and ECC did not significantly change. The ACD significantly decreased（P〈0.001 for both） and the ACA significantly increased（P=0.001 for the modified round pattern group and P=0.034 for the cruciate group）. The extent of changes in these parameters was not significantly different between the groups.CONCLUSION： Modified round pattern Nd：YAG laser posterior capsulotomy is an effective and safe method for the treatment of PCO. This method significantly changes the ACD and ACA, but the change in refraction is not significant. Modified round pattern Nd：YAG laser posterior capsulotomy can be considered a good alternative procedure in patients with symptomatic PCO.

LOOK-AHEAD ALGORITHM FOR VELOCITY CONTROL BASED ON PARAMETERIZED CURVE INTERPOLATOR

To avoid suffering gouge and transient overshooting in high speed cutting machining, a novel parametefized curve interpolator model with velocity look-ahead algorithm is proposed. Based on a prearrangement step interpolation algorithm for parameterized curves and considering high curvature points, parameterized curve tool path is divided into acceleration segments and deceleration segments by look-ahead algorithm. Under condition of characteristics of acceleration and deceleration stored in control system, deceleration before high curvature points and acceleration after high curvature points are realized in real-time in high speed cutting machining. Based on new parameterized curve interpolator model with velocity look-ahead algorithm, a real cubic spline is machined simulativly. The simulation results show that velocity look-ahead algorithm improves velocity changing more smoothly.

Numerical simulation of cutting process of the slice components cutting machine

By the use of ANSYS/LS-DYNA FEA software,numerical simulation on the cutting process of cutting plates with a reamer was carried out in the paper. The logical improvement was brought forward and the phenomenon of stress concentration was deceased by weighted analysis. The effects of different cut velocities and cutting thickness on life-spans of reamers were investigated, and the cutting parameters were optimized to satisfy the cutting precision and cutting efficiency. The study will provide a guide for the practical production.

OPTIMAL CONTROL OF CNC CUTTING PROCESS

The intelligent optimizing method of cutting parameters and the cutting stable districts searching method are set up. The cutting parameters of each cutting pass could be optimized automatically, the cutting chatter is predicted through setting up the dynamic cutting force AR(2) model on line, the spindle rotation speed is adjusted according to the predicting results so as to ensure the cutting system work in stable district.

Solution and Analysis of Chatter Stability for End Milling in the Time-domain

In this paper, the instantaneous undeformed chip thickness is modeled to include the dynamic modulation caused by the tool vibration while the dynamic regenerative effects are taken into account. The numerical method is used to solve the differential equations goveming the dynamics of the milling system. Several chatter detection criteria are applied synthetically to the simulated signals and the stability diagram is obtained in time-domain. The simulation results in time-domain show a good agreement with the analytical prediction, which is validated by the cutting experiments. By simulating the chatter stability lobes in the time-domain and analyzing the influences of different spindle speeds on the vibration amplitudes of the tool under a Fixed chip-load condition, conclusions could be drawn as follows： In rough milling, higher machining efficiency can be achieved by selecting a spindle speed corresponding to the axial depth of cut in accordance with the simulated chatter stability lobes, and in Fmish milling, lower surface roughness can be achieved by selecting a spindle speed well beyond the resonant frequency of machining system.

VIBRATION IN HIGH-SPEED MILLING OF THIN-WALLED COMPONENTS

To investigate the vibration principle in machining thin-walled components, a dynamic model for end milling of flexible structures is built based on considering the variations in the dynamic chip thickness and the differences between up-milling and down-milling. Two milling experiments verify the model. Experimental results show that the model can predict the milling force and displacements simultaneously in the dynamic milling process.

不同形状截割头截齿排列的参数化设计

通过对螺旋升角的定义,建立截割头包络面螺旋线的数学模型,提出等螺旋升角的截齿排列理论,给出不同形状截割头包络面母线的截齿空间位置模型。通过编制程序进行实例设计,获得两种不同形状的截割头及其截齿的排列和切屑图。结果表明,该模型设计的截齿排列分布均匀,截线距从截割头大端向小端递减,各截齿的切削面积均匀,截齿受力状况良好,满足截齿排列的要求,为截割头设计及截齿排列的参数化奠定了基础。

干式滚齿刀具的参数化设计及优化

对干式滚齿切削加工刀具的参数化设计及其优化设计进行了分析研究.以干式滚齿的滚刀为研究对象,以最高生产率为目标函数,建立了考虑机床、刀具、加工工艺等多种因素的限制为约束条件的滚刀结构参数及切削用量优化的数学模型,通过该模型中切削用量的变化实现了干式滚刀刀具结构的优化设计.开发了干式滚齿切削加工刀具的参数化设计及其优化设计的应用软件系统,并实现了干式滚刀零件图的绘制.

盾构刀盘设计系统开发

为快速准确地完成不同类型和尺寸盾构刀盘的设计,根据刀盘自身机械数据结构和施工过程的数据关系,结合刀具破岩机制实验数据和刀盘三维参数化机械模型和结构分析模型,利用VB完成刀盘参数化建模系统的开发,方便了刀盘设计人员准确且快速地完成各种不同地层、不同规格盾构刀盘的设计及分析。

单体型组装最大片段割参数化精确算法

单体型能提高复杂疾病全基因组关联分析的能力,可直接用生物实验测定单体型费用太高.随着DNA测序技术的发展,计算机算法被广泛用于从个体基因组测序片段上构建单体型,即单体型组装.最大片段割是最近提出的一个单体型组装优化模型,是NP-难的,目前没有实用精确算法.最近参数计算理论利用实际计算中的小参数特征为NP-难问题求解提供了一条新思路.本文根据实际测序数据覆盖了两个或多个杂合单核苷酸多态性位点(SNP)的片段的测序深度较小的特点,对跨一个具体SNP位点的所有片段划分进行枚举,提出一个参数化的动态规划算法求解其精确解.大量测试结果表明该算法比已有的启发式算法有更高的单体型重建精度.

纵轴式掘进机截齿排列的参数化设计

为了解决掘进机截割头截齿排列理论缺乏、难度大,设计水平低、截割性能差等问题,建立了截齿排列的参数化理论,讨论了包络面、等升角螺旋线、母线的连接、螺旋线上截齿的分布等问题。利用MATLAB GUIDE语言编制计算机程序,设计了"截割头形状设计"面板、"螺旋线设计"面板、"截齿分布"面板、对外接口等截齿排列参数化软件模块,并以实例介绍了纵轴式掘进机截割头截齿排列的参数化实现。结果表明,该方法丰富了截齿排列理论,使设计水平和工作效率明显提高。

基于法矢调整的浮雕曲面粘贴算法

浮雕是一类将细节附着在平面或曲面背景上的复杂曲面,设计时其背景大多为平面,应用时根据需要将其粘贴在不同的三维产品表面上,这就是浮雕曲面的粘贴问题。将浮雕和目标物体均用三角网格模型表示,提取粘贴的区域作为目标曲面并将其参数化到一个平面上,建立浮雕附着的平面与目标曲面之间的关系,然后设计一种法矢调整算法使得浮雕在目标曲面上变形较小,最后将浮雕和目标曲面合成为一个完整的三角网格。所提算法不仅适合形状变化平缓、曲率小的目标曲面,对于曲率大的目标曲面也有较好的粘贴效果。

基于ADAMS的模切机双肘杆机构优化设计研究

利用MSC.ADAMS对模切机双肘杆机构进行了参数化建模,通过建立双肘杆机构优化目标函数,实现了双肘杆机构的结构尺寸参数化优化分析,并进行了相关的运动学、动力学仿真。优化结果表明,减小动平台与水平方向的震动偏角和在水平方向的位移,将大大提高模切速度、精度和整机的稳定性。