Optimization of tool geometry parameters for turning operations based on the response surface methodology

This investigation focuses on the influence of tool geometry on the surface finish obtained in turning of AISI 1040 steel. In order to find out the effect of tool geometry parameters on the surface roughness during turning, response surface methodology (RSM) was used and a prediction model was developed related to average surface roughness (Ra) using experimental data. The results indicated that the tool nose radius was the dominant factor on the surface roughness. In addition, a good agreement between the predicted and measured surface roughness was observed. Therefore, the developed model can be effectively used to predict the surface roughness on the machining of AISI 1040 steel with in 95% confidence intervals ranges of parameters studied.     

动态优化刮刀速度的新型涂层工艺

为提高活塞式无扰动涂层工艺的涂层质量,针对高分辨率激光快速成形系统涂层工艺中存在的涂层厚度随制件高度增加而变厚的问题,提出在制作过程中动态优化刮刀速度的涂层方法。研究刮刀速度、制件高度对涂层厚度的影响。采用面响应法,建立涂层厚度误差关于制件高度及刮刀速度的数学模型。根据该模型,在制作过程中随制件高度的变化,动态优化刮刀速度,实现涂层厚度均匀化。验证试验结果表明：与普通涂层工艺相比,新型涂层工艺将涂层厚度偏差由27 μm降为6.9 μm,解决了涂层厚度随制件高度增加而变厚的问题,实现涂层厚度的均匀化,提高堆积方向的制作精度。该涂层工艺也可应用于普通光固化激光快速成形系统中,解决制作陷阱结构时涂层厚度随制件高度变厚问题,因此该工艺对于光固化快速成形技术中提高堆积方向制作精度具有重要意义。     

Statistical investigation of die wear in metal extrusion processes

The aim of this paper is the statistical process control analysis of the tool wear evolution during metal extrusion process for better understanding the principal causes that generate the variability of such a complex phenomenon. The wear prediction is carried out using finite element simulation including the Archard wear model. The tool wear modeling is presented briefly as well as the response surface methodology. The study is based on the application of the central composites designs and allows for the analysis of the response (wear) sensitivity of the tool. The statistical investigation of the process makes it possible to study the influence of each process parameter on the response sensitivity.     

Application of response surface methodology in controller fine-tuning

Despite the developments in advanced control techniques, the traditional PID controller is still being used in the majority of industrial processes. However, due to process non-linearities and modelling difficulties, common tuning techniques often yield tuning parameters that are not optimum. The subsequent fine-tuning stage is time-consuming because it is performed by trial and error. Several researchers have suggested that a statistically designed, experimental approach to controller tuning may be fruitful, e.g. Box and Kramer [1].

Using Response Surface Methodology (RSM), a model of the system performance as a function of the tuning parameters can be obtained. RSM can systematically lead the operator to improved tuning and provide a picture of the sensitivity of the process to the tuning parameters. The application of this technique in the fine-tuning of a simulated and real-time process is shown.     

含诱导缺陷多边形薄壁管结构的优化设计

应用有限元法对薄壁结构在轴向冲击下进行了数值模拟,分析了薄壁管的截面形状、诱导孔尺寸对其结构的变形模式及吸能能力的影响。结果表明:薄壁管棱边上受到的冲击力较大,随着截面边数在一定范围内的增加,正多边形和星形多边形薄壁管的吸能指标参数呈递增的趋势。含诱导缺陷薄壁管的初始峰值力较之前降低了50%。若含诱导缺陷薄壁管长度不变,随着宽度的减小,薄壁管的吸能量、平均压缩力及比吸能逐渐增加。应用有限元分析结果并结合响应面法对含诱导缺陷薄壁管进行了优化设计,为诱导型薄壁吸能结构的优化设计提供初步的数据和分析结果。     

基于均匀试验设计的响应面方法及其在无人机一体化设计中的应用

将基于均匀设计的响应面方法引入复杂系统的优化设计中,避免了复杂系统常规设计方法计算量大,计算操作复杂的缺点,提高了计算效率。同时使试验数据均匀地分布在设计空间中,能全面反映设计对象的内在性质,为后续的回归分析提供了精度保证。将该方法用于某无人机机翼的气动、结构一体化设计,计算仿真表明了本方法的有效性。     

复杂工程系统优化设计面临的问题及解决方法

指出用常规优化方法对复杂工程系统进行优化设计时面临的效率、精度和复杂信息交换等三方面问题,并结合复杂工程系统的优化计算过程,详细分析产生这些问题的原因。采用响应面方法,构建一种逐步逼近的序列响应面迭代优化计算格式。该方法使优化进程中复杂的系统分析模型被响应面模型所取代;同时还构造了一个系统数据库,在每一迭代步都有新的数据加入到该数据库中,响应面模型根据扩展后的数据库不断更新从而逐步逼近真实模型。为在保证精度的前提下减少计算量,提供一种加入数据库中新数据的选取方法,利用此方法实现了一大型运输机机翼的气动-结构一体化优化设计,计算结果表明该方法的有效性。     

Optimization of contact forces in tailor-welded blanks forming process

To attain the objective of minimizing the harmful movement of the weld joint in tailor-welded blanks (TWBs) forming, a novel optimization methodology based on dynamic explicit finite element simulation is presented to determine optimum contact forces. In this methodology, forming limit diagram (FLD) models developed for different types of TWBs are treated as a criterion of constraint in optimizations. Due to the highly nonlinear nature of the forming process, response surface methodology (RSM) is utilized to construct sequential response surfaces to approximately describe the objective the constraint functions and the optimum contact forces of TWBs stamping are obtained with some successive iterations. However, a large number of numerical simulation runs are needed for optimization with higher-order approximate models or many design variables. To improve the efficiency of optimization, the space mapping (SM) technique utilizing surrogate models is integrated with RSM. Two examples are used to validate this algorithm: one optimization for TWBs stamping with the same thickness but different materials, and the other optimization for TWBs stamping with the same material but different thicknesses. The results demonstrate that the method is efficient and effective in solving contact forces optimization problems.     

Development of friction force model for mineral oil basestock containing palm olein and antiwear additive

Palm oil is also another choice of vegetable that is being eyed as a potential vegetable oil in the lubricating area. This paper presents a study of the development of a fiction force model for mineral oil basestock containing palm olein, and antiwear amine phosphate as additive, tested on a four-ball tribotester. The model is developed using terms of wear load, speed and operating time. These variables were investigated using the design of experiments and utilization of the response surface methodology (RSM). Moreover, the effect of palm oil on wear scars of material tested was also discussed. This paper shows palm olein itself indeed is a good antiwear lubricant compared to mineral oil basestock (SN500), but the use of additives shows an increase in better lubrication as smaller wear scars are found out from using palm olein in the test runs.     

Optimisation of machining parameters for turning operations based on response surface methodology

Design of experiments has been used to study the effect of the main turning parameters such as feed rate, tool nose radius, cutting speed and depth of cut on the surface roughness of AISI 410 steel. A mathematical prediction model of the surface roughness has been developed in terms of above parameters. The effect of these parameters on the surface roughness has been investigated by using Response Surface Methodology (RSM). Response surface contours were constructed for determining the optimum conditions for a required surface roughness. The developed prediction equation shows that the feed rate is the main factor followed by tool nose radius influences the surface roughness. The surface roughness was found to increase with the increase in the feed and it decreased with increase in the tool nose radius. The verification experiment is carried out to check the validity of the developed model that predicted surface roughness within 6% error.     

Analysis and optimization of micro-geometry of miniature spur gears manufactured by wire electric discharge machining

This paper reports about the analysis and optimization of micro-geometry parameters (i.e. total profile deviation ‘F_a’ and accumulated pitch deviation ‘F_p’) of the wire electric discharge machined (WEDMed) fine-pitch miniature spur gears made of brass. Effects of four WEDM process parameters namely voltage, pulse-on time, pulse-off time and wire feed rate on the micro-geometry of the miniature gears were analyzed by conducting the experiments designed using Box–Behnken approach of response surface methodology (RSM). Analysis of variance study found all four input parameters significant. Larger deviations in profile and pitch were observed with higher values of the voltage and pulse-on time, and with lower values of wire feed rate and pulse-off time. Multi-performance optimization of WEDM parameters was done using the desirability analysis to minimize profile deviation and pitch deviation simultaneously. The values of F_a and F_p of the gear obtained by the confirmation experiment conducted at the optimized WEDM parameters were as 11.5 μm and 9.1 μm respectively. These values categorize the WEDMed gear having DIN quality number as 7 and 5 respectively for profile and pitch which are better than those obtained by the conventional miniature gear manufacturing processes.     

Pneumatic gauge empirical-mechanistic modelling

Back-pressure gauge steady-state empirical-mechanistic modelling has been introduced. This technique contains gauge theoretic modelling and for model performance enhancement entertains empirical-mechanistic steady-flow models of gauge flow restrictors which are formulated as the mathematical products of available theoretical and polynomial empirical approximating functions. Flow restrictor discharge coefficient variations were considered as the polynomial empirical functions of the same variables as the theoretical functions. Motivated iteration procedure was employed for minimization of model errors. The comparison of modelling results and reference experimental data has revealed that the empirical-mechanistic modelling permits to attend minimized discrepancy from empirical evidence.     

The use of mixture experiments in tolerance allocation problems

The response surface methodology (RSM) approach can be used to determine the optimal component tolerances in an assembly. Frequently, response surface designs such as Box-Behnken design and central composite design are used in tolerance allocation problems. In this article, mixture experiments, which are essentially constructed for designing a blend composition, are proposed instead of response surface designs in order to observe the cost values. Also some advantages and disadvantages of mixture designs are discussed.     

基于响应面法的麦弗逊悬架优化设计

用响应面法对麦弗逊悬架结构参数进行优化设计。基于多刚体动力学软件ADAMS构建麦弗逊悬架模型;在ADAMS/Insight模块中用析出法得到影响各定位参数的主要因子;接着,采用响应面法建模的中心组合设计法仿真得到响应面模型方程。并依据结果进行悬架系统的优化研究。     

Statistical analysis of repeatability in laser percussion drilling

This study investigates the effect of six parameters in the repeatability of drilled holes in laser percussion drilling process by means of statistical techniques. Peak power, pulse width, pulse frequency, number of pulses, gas pressure and focal plane position were considered as independent process parameters. Experiments were designed with the aim of reducing the number of required experiments. The response surface method was used to develop the models for required responses. The significant factors in the process were selected based on the analysis of the variance (ANOVA). The experiments were conducted in mild steel sheet with a thickness of 2 mm. Each experiment was repeated 35 times in order to investigate the repeatability of the process. The equivalent entrance diameter, percentage of standard deviation of entrance diameter (%STD Eq Dia), circularity (ratio of minimum to maximum Feret’s diameter) and its standard deviation (STD circularity) were selected as process characteristics. The %STD Eq Dia and STD circularity, respectively, show the repeatability of equivalent diameter and circularity in the process. The results show that the process of drilling smaller hole diameters is more repeatable than drilling larger holes. Pulse width, gas pressure, focal plane position, peak power and number of pulses, respectively, have significant effect on the repeatability of hole diameter and circularity. Pulse frequency has no significant effect on the repeatability of the process.     

基于智能布点技术的近似模型优化研究及其在冲压成形中的应用

针对基于统计学原理试验设计方法的缺陷,采用一种基于设计变量边界条件以及最优样本信息的智能布点方法,并结合移动最小二乘的响应面近似模型优化方法对非线性问题进行求优。为了验证该方法的有效性,采用该方法对非线性测试函数进行了极值求解。同目前主流的试验设计方法相比,其求解精度以及响应面拟合精度都有一定的提高。将该方法应用于薄板冲压成形体系中拉延筋的优化,得到预期的结果,并成功地用于实际产品成形。     

Surface roughness prediction for the milling of Ti–6Al–4V ELI alloy with the use of statistical and soft computing techniques

This study focuses on Ti–6Al–4V ELI titanium alloy machining by means of plain peripheral down milling process and subsequent modeling of this process, in order to predict surface quality of the workpiece and identify optimal cutting parameters, that lead to minimum surface roughness. For the purpose of accomplishing this task a set of experiments were performed on a CNC milling centre and design of experiments based on Box Behnken Design (BBD) for a three factor and three level central composite design concept was conducted. Depth of cut, cutting speed and feed rate were selected as input parameters and surface roughness was measured after each experiment performed. At first, Response Surface Methodology (RSM) was employed for establishing a quadratic relationship between input and output parameters. Analysis of variance (ANOVA) was then conducted for the evaluation of the proposed formula. RSM was also used for the optimization analysis that followed for the determination of milling cutting parameters for minimum surface roughness. The analysis indicates that the use of BBD can reduce the number of experiments needed for modeling and optimizing the milling operation of Titanium alloys. Furthermore, this method is able to provide models that can reliably be used for any cutting conditions within the limits of the input data. Finally, Artificial Neural Networks (ANN) models were developed to allow for a more robust simulation model to be built and comparison between ANN and RSM models to be performed. From the presented results, for RSM, the mean square error and the correlation coefficient were determined to be 8.633 × 10⁻³ and 0.9713, respectively; for ANN models, the corresponding values were 2 × 10⁻³ and 0.9824, for the test group of the optimum model. Simulations indicated that, although input data were too few, a considerably reliable ANN model was able to be built and despite of its complexity compared to RSM model, it was proven to be superior in terms of prediction accuracy.     

响应面法优化火焰原子吸收仪检测Zn元素工作条件

采用响应面法优化火焰原子吸收仪检测Zn元素工作条件。通过在单因素基础上,用Design-Expert8.0软件中Box-Behnken Design试验设计研究灯电流、光谱通带、乙炔流量、燃烧器高度4个变量对Zn元素吸光度值的影响程度。用响应面法得出4个考察因素最优工作参数和吸光度预测值:灯电流1.0mA、光谱通带0.26nm、乙炔流量1302.01mL/min、燃烧器高度6.29mm,吸光度预测值0.356Abs。通过实验证实:吸光度真实值与预测值接近,对样品检测,样品平均回收率在93%~104%之间,RSD在0.18%~0.26%范围内。     

Damage identification by response surface based model updating using D-optimal design

Statistical tools, as well as mathematical ones, have been widely adopted and their performance has been shown in different engineering problems where randomicity usually exists. In the realm of engineering, merging statistical analysis into structural evaluation and assessment will be a tendency in the future. As a combination of mathematical and statistical techniques, response surface methodology has been successfully applied to design optimization, response prediction and model validation. This methodology provides explicit functions to represent the relationships between the inputs and outputs of a physical system, which is also a desirable advantage in damage identification. However, so far little research has been carried out in applying the response surface methodology to structural damage identification. This paper presents a damage identification method achieved by response surface based model updating using D-optimal designs. Compared with some common designs constructing response surfaces, D-optimal designs generally require a minimum number of numerical samples and this merit is quite desirable when analysts cannot obtain enough samples. In this study, firstly D-optimal designs are used to establish response surface models for screening out non-significant updating parameters and then first-order response surface models are constructed to substitute for finite element models in predicting the dynamic responses of an intact or damaged physical system. Three case studies of a numerical beam, a tested reinforced concrete frame and a tested full-scale bridge have been used to verify the proposed method. Physical properties such as Young’s modulus and section inertias were chosen as the input features and modal frequency was the only response feature. It has been observed that the proposed method gives enough accuracy in damage prediction of not only the numerical but also the real-world structures with single and multiple damage scenarios, and the first-order response surface models based on the D-optimal criterion are adequate for such damage identification purposes.