基于正交切削模型的铣削加工残余应力预测方法

提出了一种基于正交切削模型的铣削加工残余应力预测方法.针对直齿圆柱铣刀建立了铣削加工的平面应变有限元模型,并通过分段曲线限定不同温度下应力与应变间的关系,详细表明材料的加工硬化规律.有限元模型采用相关的实验数据进行了验证.在铣削用量确定的前提下,通过对航空铝合金70507451进行加工模拟,研究了直齿圆柱铣刀前角对已加工表面残余应力的影响.     

试验设计法优化汽车内饰板成型工艺参数

注射成型生产中,塑件翘曲变形的大小是影响塑件质量的主要因素之一,以汽车内装饰板为例,对影响翘曲变形的主要加工参数进行试验设计,由直交表进行参数的编排,对试验数据计算出望小特性比值,以少量的试验次数获得最优化的成型加工参数组合,从而减少翘曲变形量,对注射生产提高塑件质量有重要的借鉴作用。     

Time-modulated CVD process optimized using the taguchi method

The Taguchi method is used herein to optimize the time-modulated chemical vapor deposition (TMCVD) process. TMCVD can be used to deposit smooth, nanocrystalline diamond (NCD) coatings onto a range of substrate materials. The implementation of the Taguchi method to optimize the TMCVD process can save time, effort, and money. The Taguchi method significantly reduces the number of experiments required to optimize a fabrication process. In this study, the effect of five TMCVD process parameters is investigated with respect to five key factors of the as-grown samples. Each parameter was varied at four different values (experimental levels). The five key factors, taking into consideration the experimental levels, were optimized after performing only 16 experiments. The as-grown films were characterized for hardness, quality, surface roughness, and microstructure using scanning electron microscopy, Raman spectroscopy, surface profilometry, and Vickers hardness testing. This paper was presented at the fourth International Surface Engineering Congress and Exposition held August 1–3, 2005 in St. Paul, MN.     

Application of orthogonal experimental design and Tikhonov regularization method for the identification of parameters in the casting solidificationp rocess

The inverse heat conduction method is one of methods to identify the casting simu-lation parameters. A new inverse method was presented according to the Tikhonov regularization theory. One appropriate regularized functional was established, and the functional was solved by the sensitivity coefficient and Newton-Raphson iteration method. Moreover, the orthogonal experimental design was used to estimate the ap-propriate initial value and variation domain of each variable to decrease the number of iteration and improve the identification accuracy and efficiency. It illustrated a detailed case of AI SiTMg sand mold casting and the temperature measurement ex- periment was done. The physical properties of sand mold and the interfacial heat transfer coefficient were identified at the meantime. The results indicated that the new regularization method was efficient in overcoming the ill-posedness of the inverse heat conduction problem and improving the stability and accuracy of the solutions.     

利用正交试验设计优化冷弯成形工艺参数

冷弯成形工艺参数的设计对冷弯成形产品质量有重要影响。本文对方矩形管冷弯成形过程中机架间距、摩擦因数和轧制速度的不同取值水平通过正交试验设计,利用Abaqus有限元软件的显式非线性动态分析对所设计试验仿真模拟,得到了每道次轧制过程中带钢边部最大纵向应变最小时各个道次3个工艺参数的最佳取值。并用优化后的参数进行仿真和验证,得到各道次带钢边部最大纵向应变比优化前要小,优化后第4~第10道次带钢纵向应变极值相对接近,产品边部拉伸小,并且边部拉伸分布比较均匀,有效改善了产品质量。     

The statistical modeling of surface roughness in high-speed flat end milling

Surface roughness is one of the most important requirements in machining process. The surface roughness value is a result of the tool wear. When tool wear increase, the surface roughness also increases. The determination of the sufficient cutting parameters is a very important process obtained by means of both minimum surface roughness values and long tool life. The statistical models were developed to predict the surface roughness.This paper presents the development of a statistical model for surface roughness estimation in a high-speed flat end milling process under wet cutting conditions, using machining variables such as spindle speed, feed rate, depth of cut, and step over. First- and second-order models were developed using experimental results of a rotatable central composite design, and assessed by means of various statistical tests. The highest coefficient of correlation (R_adj²) (88%) was obtained with a 10-parameter second-order model. Meanwhile, a time trend was observed in residual values between model predictions and experimental data, reflecting the probable effect of the tool wear on surface roughness. Thus, in order to enhance the estimation capability of the model, another independent variable was included into the model to account for the effect of the tool wear, and the total operating time of the tool was selected as the most suitable variable for this purpose. By inserting this new variable as a linear term into the model, R_adj² was increased to 94% and a good fit was observed between the model predictions and supplementary experimental data.In this study, it was observed that, the order of significance of the main variables is as X₅>X₃>X₄>X₁>X₂ (total machining time, depth of cut, step over, spindle speed and feed rate, respectively).     

制备纳米铝粉工艺参数的正交优化

试验选用无水乙醇为液相介质、聚乙烯吡咯烷酮(PVP)作为修饰剂,采用高能球磨法,成功制备出分散良好的纳米铝粉.通过正交试验,分析了球磨时间、铝粒的加入量、铝粒与修饰剂的质量比和转速四个工艺参数,对纳米铝粉的产率、产量和粉体的特征粒径D50的影响.结果表明:在本试验条件下,制备纳米铝粉的最佳工艺参数为:时间12 h,铝粒的加入量为20 g,铝粒与修饰剂的质量比为4∶1,转速为300 r/min.     

基于正交试验的气辅成型工艺优化

以加强筋为研究对象,对气辅成型中的熔体温度、熔体预注射量、气体注射压力、气体注射延迟时间、气体注射时间等影响气辅成型质量的主要参数进行数值模拟,并对影响塑件成型质量的相关工艺参数进行正交试验。先通过初步的五因素四水平L16(45)正交试验获得工艺参数的大致范围,然后在该基础上再进行改进的四因素三水平L9(34)正交试验,最终获得较好的工艺条件。     

3D welding and milling: part II—optimization of the 3D welding process using an experimental design approach

A process of combined additive and subtractive techniques for the direct freeform fabrication of metallic prototypes and tools is being developed by the authors. This hybrid process, called ‘3D welding and milling’, uses gas metal arc welding (GMAW) as an additive and conventional milling as a subtractive technique, thereby exploiting the advantages of both processes. In this paper, the results of the optimization of the deposition process using a statistical approach as well as the result of plastic injection molding with the inserts fabricated by this hybrid process are described. The result proves the applicability of the 3D welding and milling process for direct fabrication of metallic prototypes and tools.     

The effect of tool vibrations on the flank surface created by peripheral milling

Tool vibrations have a significant influence on the surface quality with respect to surface location error and roughness. Even chatter-free milling processes can produce a high surface location error since chatter-free does not necessarily mean vibration-free. This article describes a geometric model for predicting the surface formation resulting from peripheral milling processes when tool vibrations are present. This model enables one to predict and minimize the roughness and location error of the flank surface. Comparisons between simulations and experiments show the effectiveness of this modeling approach. An important result of this research is that it has shown that milling at a stability maximum does not generally yield the best surface quality.     

The use of experimental design method for the investigation of pitting potential of aluminum

The dependence of the pitting potential (E_p) of aluminum on chloride concentration, pH and the temperature of the solution was studied by the potentiodynamic method according to a statistical experimental design. The parameters of the statistical E_p model offered on the basis of Box‐Wilson experimental design method were evaluated with the use of the experimental data. Comparison of the predicted values from the model with the observed values showed that the model is a good fit. From the model equation the most noble E_p value of ? 420 mV was obtained when Cl^? ion concentration, temperature and pH of the solution were 57 ppm, 22°C, and 8.3 respectively. Box‐Wilson experimental design technique was proved to be applicable in modelling E_p of aluminum.     

基于稳健设计的钛合金波纹管超塑成形工艺

根据稳健设计中的响应面法—复合设计法,用MARC有限元分析软件模拟了钛合金波纹管超塑成形过程的胀形、合模和充满3个阶段。根据模拟结果得到了钛合金波纹管质量评价指标波峰最小厚度及其影响因素筒坯高度和胀形阶段成形气压之间的二元一次和二元二次多项式回归公式,从而实现了钛合金波纹管超塑成形工艺参数的稳健设计。Ti-6Al-4V双波DN250波纹管超塑成形实验证明了回归公式的准确性和复合设计法用于钛合金波纹管超塑成形过程的可行性。     

基于华中系统的模板开框宏程序设计

模板开框是模坯加工的重要环节,通常为保证一定精度采用自动编程数控加工完成。自动编程前期设置繁琐、程序手动修改不便,采用宏程序对开框加工进行分层切削控制、行切及环切刀路设计,通过同一程序实现不同尺寸,不同加工参数要求的加工,大大提高了加工效率,并解决了重复编程的问题。     

Use of Taguchi method to study a robust design for the sectioned beams curvature during rolling

Finite element DEFORM™ 3D software is employed to examine the plastic deformation behavior of V-sectioned and T-sectioned porous beams at the roll gap under various rolling conditions. The finite element code is based on a rigid–plastic model in which it is assumed that the rolls are rigid bodies and that the temperature change induced in the beams during rolling is sufficiently small that it can be ignored. The analytical model is used to systematically examine the effect of the inclination angle of the roll profile, the friction factors between the rolls and the beam, the roll radii and the angular speed of the upper and lower rolls on the curvature of the rolled beam, the rolling torque, the effective strain, the effective stress and the variation of density of the rolled product at the exit. The Taguchi method is employed to design the rolling parameters to optimize the curvature of the beams. The analytic results have shown that: (1) the inclination angle of the inner part (i.e. vacancy) of the upper roll, the friction factor of the lower roll, the angular velocity of the lower roll and the roll radii, respectively, all have a significant influence upon the curvature of the rolled V-sectioned product, κ = 1/r_a; (2) the reduction ratio of the porous beam, the friction factor of the lower roll, the angular velocity of the lower roll, and the roll radii, respectively, all have a significant influence upon the curvature of the rolled T-sectioned product, κ = 1/r_a.     

聚甲醛齿轮强度形成机理及工艺优化

以提高齿根弯曲强度为目标开展聚甲醛齿轮的力学性能测试,优化了齿轮强度计算方法,提高了弯曲强度计算结果的可靠性。对试验结果进行分析,得到了模具温度、熔体温度、保压压力、注射速度、冷却时间、保压速度对齿轮强度的影响程度及趋势,得出模具温度和熔体温度是影响聚甲醛齿轮强度的关键工艺参数,且模具温度的影响最显著,并对成型制品进行DSC测试,发现制品强度与结晶度密切相关,提高模具温度和熔体温度增强了制品的结晶度,也提高了制品的强度。     

A study on shrinkage compensation of the SLS process by using the Taguchi method

This paper proposes the test pieces of the X, Y, and Z axes to compensate for the distortion of the SLS parts resulting from the phase changes during the sintering process. In the case of the test pieces proposed for the compensation of the X and Y axes, the accurate rates of shrinkage can be measured with the reduction of curling that is obtained from the adjustment of the building orientation. A set of basic equations is suggested as a useful scale factor to adapt the shrinkage rate. The scale factors of the X, Y, and Z axes generated by the build-up of the compensation test pieces of each axis are required to satisfy the dimensional accuracy, even if there is any change in the build position and the size of the SLS parts in the chamber. A new approach is investigated that enables the operator to determine the optimal scale factors for an actual SLS process applying the Taguchi method.     

工艺参数对气辅注射制品翘曲的影响

基于气体辅助注射过程的数值模拟,利用Taguchi试验方法设计了L18(37)试验矩阵,采用标准方差分析方法,分析了GAIM工艺参数对制品翘曲的影响。研究表明:在所选择的工艺参数中,对翘曲影响权重依次为气体保压时间、熔体温度、预注射量、延迟时间、气体压力、注射时间和模具温度。此外,采用单因素法研究气体控制参数对制品翘曲的影响。结果表明:气体保压时间增加10 s,制品翘曲量减小36.9%;提高气体压力和增加延迟时间,制品翘曲量减小。     

Application of artificial neural network and Taguchi method to preform design in metal forming considering workability

This study describes a new method of perform design in muti-stage metal forming processes considering workability limited by ductile fracture. The finite element simulation combined with ductile fracture criterion has been performed in order to predict ductile fracture. The artificial neural network using the Taguchi method has been implemented for minimizing objective functions relevant to the forming process. The combinations of design parameters used in finite element simulation are selected by orthogonal array in statistical design of experiments. The orthogonal array and the result of simulation are used as train data for artificial neural networks. The cold heading process is taken as an example of designing preforms which do not form any fracture in the finished product. The results of analysis to validate the proposed design method are presented.     

基于正交设计的神经网络训练样本的选择方法及其在冷挤压工艺设计中的应用研究

冷挤压件的形状是制定冷挤压工艺方案时需要考虑的最重要的因素之一,基于目的性和方便性原则,该文针对冷挤压件的形状特征进行分类,并在此基础上分别建立基于正交实验设计的人工神经网络训练样本子集,最后将所有子集进行整合,形成初始训练测试样本集。结合典型冷挤压件,分析了采用正交设计方法选取人工神经网络训练样本的过程,研究了基于正交设计的人工神经网络的训练、测试方法,实现了基于人工神经网络的冷挤压工艺设计。     

Effect of annealing on the conversion of ZnS to ZnO nanoparticles synthesized by the sol-gel method using zinc acetate and thiourea

A systematic study is presented on the conversion of zinc sulfide to zinc oxide nanoparticles as a function of annealing temperature. Zinc acetate dihydrate (Zn(CH₃COO)₂.2H₂O) and thiourea (NH₂CSNH₂) are used as precursors to synthesize ZnS and then ZnO. The aqueous solution of the precursor was refluxed at 90 °C for over 12 h. The synthesized complex was then annealed at 300 °C, 500 °C, 700 °C, and 900 °C in air for one hour. From elemental analyses, it was found that the as-synthesized powder is a mixture of ZnS and ZnO, which annealing later converts to the zinc oxide phase only. The morphological observations revealed spherical particles of various sizes (20 nm to 300 nm) while increasing the annealing temperatures. A drastic change in the vibration bands is noticed with annealing. Photoelectron peaks related to sulfur and carbon are observed for synthesized powder, whereas, these peaks disappeared when annealed at 500 °C.