复合材料带缠绕成型工艺参数耦合机制及优化

基于复合材料缠绕成型工艺过程研究,分别对成型过程中紧密接触与自粘接过程进行理论分析,提出影响复合材料缠绕制品质量的关键工艺参数:缠绕温度、缠绕压力和缠绕张力;以层间剪切强度(ILSS)为优化目标,根据响应面法Box-Behnken Design(BBD)原理设计实验,建立工艺参数耦合对剪切强度的回归模型,通过对残差、方差(ANVOA)、预测值与实际值对比等检验分析,验证回归模型的可靠性及有效性,进而获得缠绕成型最优工艺参数。结果表明:在最优工艺参数作用下,层间剪切强度达到22.9 MPa,缠绕制品结合强度最高。     

基于响应面遗传算法的低碳钢激光切割工艺分析及参数优化

为了研究光纤激光加工工艺对Q235低碳钢板切割质量的影响,采用1000 W光纤激光切割机对3 mm厚低碳钢板切割质量影响规律进行了研究.设计了Box-Behnken实验,使用粗糙度仪和高精度电子秤完成了切面粗糙度和试样挂渣量的测量,研究了在氧气熔化切割方式下激光功率、切割速度、激光频率、激光占空比和辅助气体压力等工艺参...     

Effects of process parameters on periodic impact force exerting on cutting tool in ultrasonic vibration-assisted oblique turning

During ultrasonic vibration-assisted machining, the large impact force induced by tool-workpiece reengagement (TWR) is an important factor that affects tool chipping. However, mechanical analysis into process factors that affect the impact force and their influencing mechanisms are insufficient. Herein, a prediction model for the instantaneous cutting force during both TWR and the stable turning process, which depends on the process parameters and material properties, is firstly proposed based on the kinematic and dynamic analysis of ultrasonic vibration-assisted oblique turning (UVAOT). The results calculated using the developed cutting force model agree well with the experimental results presented in the literature. Next, the linear change law of the instantaneous cutting force with cutting time during the actual TWR is clarified using the proposed model. The effect of the UVAOT process parameters on the average impact force during the periodic TWR process is discussed, and the influence mechanism is analyzed from the perspective of mechanics. A positive linear correlation is discovered between the feed speed and average impact force. The ultrasonic amplitude and cutting speed do not significantly affect the average impact force of the new sharp cutting tools. These findings are consistent with the experimental observations of tool chipping and are applicable to select process parameters for reducing tool chipping during UVAOT.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00398-x     

Predictive modelling of turning operations using response surface methodology,artificial neural networks and support vector regression

This paper focuses on developing empirical models for predicting surface roughness, tool wear and power required in turning operations. These response parameters are mainly dependent upon cutting velocity, feed and cutting time. Three competing data mining techniques, response surface methodology (RSM), artificial neural networks (ANN) and support vector regression (SVR), are applied in developing the empirical models. The data of 27 experiments have been used to generate, compare and evaluate the proposed models of tool wear, power required and surface roughness for the selected tool/material combination. Testing results demonstrate that the models developed in this research are suitable for predicting the response parameters with a satisfactory goodness of fit. It has been found that ANN and SVR models are much better than regression and RSM models for predicting the three response parameters. Finally, some future research directions are outlined.     

响应面分析法优化不锈钢激光切割工艺参数

为了获得良好的不锈钢激光切割质量,确定合理的切割工艺参数,本文以3 mm厚304不锈钢为研究对象,采用响应面法进行试验方案的设计和分析,利用超景深显微镜进行了试样表面切缝宽度、表面纹理最大峰值、挂渣量的测量,利用最小二乘法进行数据处理,研究了激光功率(X₁)、切割速度(X₂)、离焦量(X₃)以及辅助气体压力(X₄)对不锈钢切割表面切缝宽度、表面纹理最大峰值、挂渣量的影响规律,并基于响应面法得到了3个响应目标的预测函数.实验结果表明:X₂=2.48 m/min,X₃=-1.05 mm,X₄=1 MPa时,随着激光功率的增加,切缝宽度不断增大;X₁=300 W, X₄=1.2 MPa时,随着切割速度的加快切缝宽度逐渐减小,随着离焦量的增大切缝宽度先减小后增大;X₁=300 W,X₃=0 mm,X₄=1.40 MPa时表面纹理的最大波峰值RZ随着激光功率、离焦量以及切割速度的增大先减小后增大。以切缝宽度最窄、表面纹理最大峰值最小、挂渣量最少为响应目标确定了3 mm厚304不锈钢激光切割的最佳工艺参数为X₁=365.86 W,X₂=2.75 m/min,X₃=0 mm,X₄=1.4 MPa。试验验证发现:切缝宽度、表面纹理最大峰值、挂渣量的预测误差应分别控制在8.4%~12.7%、21%~24.9%、16.7%~19.5%。     

The impact of surface integrity by hard turning versus grinding on rolling contact fatigue – Part I: Comparison of fatigue life and acoustic emission signals

Hard turning and grinding are finishing processes for the manufacture of precision components, such as bearings, gears and cams. However, the effects of distinct surface integrity by hard turning versus grinding on rolling contact life are poorly understood. Four representative surface types were prepared: as-turned, as-ground, turned and polished and ground and polished. Surface integrity was characterized by surface topography, microstructure and micro/nanohardness. Fatigue tests were performed with an acoustic emission sensor and the signal processing software. The surface topographies show that skewness of the as-ground surface is much more negative than the as-tuned one while other surface parameters are equivalent. The turned surface has a thicker strain hardened zone and a thinner thermal affected zone than those of the ground one. The ground surface has higher micro- and nanohardness on surface and in the subsurface than the turned one. The amplitude of acoustic emission signal is the most stable and sensitive signal to fatigue failure. The turned surface may have a longer life (> 84%) than the ground one with equivalent surface finish. The fatigue lives of the bearing assembly are nearly identical for the turned surface versus the polished surface and the turned polished surface versus the ground and polished surface. In addition, polishing may not necessarily improve fatigue life of the machined surface, but increase bearing assembly life as much as 40%.     

Solving the optimal process target problem using response surface designs in heteroscedastic conditions

The contemporary industrial environment continues to rely on the identification of the optimal process target as a means to minimise the product defect rate and ultimately reduce manufacturing costs. Within the context of the optimal process target problem, this paper will offer three distinct contributions. First, a review of literature associated with the process target problem indicates that most research work assumes a known process distribution mean and variance prior to the identification of optimal settings. In contrast, this paper will incorporate the use of response surface designs into solving the process target problem, thus removing the need to make assumptions regarding the process parameters. Second, most research regarding the development of response surface designs either assumes that the same number of observations are made on a quality characteristic of interest, or model error always exhibits a uniform pattern of constant variance. This paper, however, will incorporate alternative modelling techniques to investigate instances when these assumptions are not present, thus broadening the scope of the process target problem. Finally, most research in this area focuses on the determination of the optimal process mean; in this paper, however, we propose a model for simultaneously determining the optimal process mean and variance.     

Well-designed WO3/Activated carbon composite for Rhodamine B Removal: Synthesis,characterization, and modeling using response surface methodology

This study focuses on the preparation of WO₃ oxide nanoparticle/Activated carbon composite (WO₃/AC) for Rhodamine B (RhB) adsorption. The prepared samples were characterized using X-Ray Energy Dispersive Spectroscopy (EDS) and Scanning Electron Microscopy (SEM), Brunauer–Emmett–Teller surface area (BET), Raman Spectroscopy and Thermogravimetric analyses (ATG-ATD). Adsorption experiments of RhB onto WO₃/AC were carried out in a batch reactor and different operational parameters were investigated. The RhB adsorption process was well fitted by pseudo-second-order kinetic and Langmuir isotherm models (1666.67mg.g^?1). Moreover, the values of thermodynamic parameters indicate the spontaneous, endothermic and physisorption adsorption nature. Finally, adsorption mechanism was proposed on the basis Raman analyses before and after adsorption.     

Optimisation of cutting parameters for burr minimization in face-milling operations

Burrs formed during face milling operations can be very difficult to characterize since there exist several parameters which have complex combined effects that affect the cutting process. Many researchers have attempted to predict burr characteristics including burr size and shape, using various experimental parameters such as cutting speed, feed rate, in-plane exit angle, and number of inserts. However, the results of these studies tend to be limited to a specific process parameter range and to certain materials. In this paper, the Taguchi method--which is a systematic optimisation method for design and analysis of experiments--is introduced to acquire optimum cutting conditions for burr minimization. In addition, analysis of variance (ANOVA) is employed to study more detailed performance characteristics. Experimental verifications are provided to show the effectiveness of this approach.     

Optimization of process parameters for transalkylation of toluene to xylene using response surface methodology

ABSTRACT

H-beta zeolite was modified by the ion exchange method to replace its H⁺ ions with Ce⁴⁺ ions. The catalytic performance of this cerium exchanged beta zeolite was evaluated for vapor phase transalkylation of 1,2,4 TMB (1,2,4 trimethylbenzene) with toluene for the production of xylene in a fixed bed, down-flow reactor. The modified zeolite was found to be highly active for this transalkylation reaction. The response surface methodology (RSM) is used for designing the experiments. The effect of three important reaction parameters viz. temperature, reactant ratio, and space time on response variables (toluene conversion and xylene selectivity) is studied and discussed. All the three selected reaction parameters were found to be significant for the toluene conversion; whereas, xylene selectivity was not much influenced by the temperature. The optimum values of the reaction parameters predicted by the model (temperature: 409.7°C, reactant ratio: 2.024, and space time: 4.451) were validated by an experimental run. The results of the experimental run were in close agreement with the model predicted results.     

用玻璃粉作粘结剂制备碳纳米管厚膜及其场发射特性

研究了用涂敷法制备的碳纳米管（CNT）厚膜及其场发射特性,裂解法获得的碳纳米管与玻璃粉等混合、研磨,直接涂敷在Si基底上,经烧结后制成碳纳米管厚膜,二极结构测量的结果表明,碳纳米管厚膜有较低的开启电场（1.0～1.25V/μm）,场强为5V/μm时,电流密度达到了50μA/cm^2.该工艺的烧结过程应控制好,加热时间稍长会使CNT厚膜的场发射性能很快下降,时间过长会使CNT处在厚膜表面之下,无法有效发射电子.浆料中的玻璃粉比例增大时,碳纳米管阴极的场发射性能会有所降低.     

Influence of carbon nanotube concentration and sonication temperature on mechanical properties of HDPE/CNT nanocomposites

Carbon nanotube (CNT) reinforced high-density polyethylene (HDPE) composites were prepared by a melt mixing procedure. The mechanical properties were analyzed using a central composite design where key factors were CNT concentration and sonication temperature during the sample preparation process. The results indicated that the optimum values were 0.8 wt% for the concentration of CNT and 55°C for the sonication temperature. The samples obtained at optimal conditions were systematically studied. Nanoindentation analysis showed an increase of 43% in Vickers hardness of the nanocomposite when compared to pure polymer. The improvement on the mechanical property is related to changes in the thermo-physical and viscoelastic properties of the nanocomposite.     

Optimization of multi-pass turning operations using genetic algorithms for the selection of cutting conditions and cutting tools with tool-wear effect

A new genetic algorithms-based method is applied for the optimization of cutting conditions and the selection of cutting tools in multi-pass turning operations. A new methodology for the allocation of total depth of cut in multi-pass turning operations is also developed. A comprehensive optimization criterion for multi-pass turning operations is developed and used as the objective function integrating the contributing effects of all major machining performance measures in all passes. The effect of progressive tool wear in optimization processes for multi-pass turning operations is included. Presented case studies demonstrate the application of the new methodology for optimal allocation of total depth of cut as well as optimization of cutting conditions and the selection of cutting tool inserts, and offer a comparison between optimization processes with and without the effect of tool wear in all passes.     

Optimization of the cutting process of multi-wall carbon nanotubes for enhanced dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) were fabricated based on multi-wall carbon nanotube (MWCNT)-TiO₂ photo-anodes, which were prepared by the procedures of cutting MWCNTs and subsequent immobilization TiO₂ on MWCNTs. Through a detailed study, we found that cut-MWCNTs with proper ultrasonication time (2 h) and proper content (0.075%) resulted in 58 and 40% increase in short-circuit photocurrent and overall energy conversion efficiency, respectively, compared with that of a DSSC using only TiO₂ photo-anode. The enhancement of cut-MWCNTs for DSSC was attributed to the introduction of percolative conductive paths which facilitate the rapid electron transfer.     

Optimization of correlated multi-response quality engineering by the upside-down normal loss function

Most of the published literature on robust design is basically concerned with a single response. However, the reality is that common industrial problems usually involve several quality characteristics, which are often correlated. Traditional approaches to multidimensional quality do not offer much information on how much better or worse a process is when finding optimal settings. Köksoy and Fan [Engineering Optimization 44 (8): 935–945] pointed out that the upside-down normal loss function provides a more reasonable risk assessment to the losses of being off-target in product engineering research. However, they only consider the single-response case. This article generalizes their idea to more than one response under possible correlations and co-movement effects of responses on the process loss. The response surface methodology has been adapted, estimating the expected multivariate upside-down normal loss function of a multidimensional system to find the optimal control factor settings of a given problem. The procedure and its merits are illustrated through an example.     

Study of the ability to field emission from diamond-like carbon layers and carbon nanotubes

The aim of this work was to study the relationship between parameters of the electron field emission and the film deposition method. In this study two methods were applied: classical radio frequency plasma-assisted chemical vapor deposition (RF PACVD) to produce diamond-like carbon (DLC) layers and chemical vapor deposition (CVD) to produce carbon nanotubes (CNT). DLC layers were grown on n-type silicon substrates and CNT were grown on n-type and p-type silicon substrates.Atomic force microscopy (AFM) and Raman spectroscopy were used to investigate the physical and chemical parameters of DLC films after deposition process. The electrical parameters of capacitors with the DLC layer as an insulator were extracted from the capacitance-voltage (C-V) and current-voltage (I-V) characteristics. Measurements of the field emission were performed after characterization of the layer properties.     

一种基于CVD法的纳米碳管微观分析及场致发射特性的研究

将化学气相沉积法（CVD）制备的纳米碳管提纯后，用透射电镜（TEM）观测了它的微观结构，通过实验对纳米碳管在不同温度下生长的结构特性进行了分析比较，得出了纳米碳管生长的最佳温度为750℃；并对纳米碳管粉体的拉曼（Raman）光谱进行了分析，得到了与透射电镜观测相一致的结论；最后测试了纳米碳管的场致发射特性．     

激光透射连接PET的工艺参数建模与优化

为了获得激光透射连接聚对苯二甲酸乙二酯薄板的最佳工艺参数,采用响应曲面法对影响激光透射连接质量的四个主要影响因素即激光功率、扫描速度、压紧力、扫描次数进行建模与优化。利用Design Expert软件分析了主要工艺参数对连接质量的影响,并获得了最佳工艺参数:激光功率33.2W、扫描速度9 mm/s、压紧力0.45 MPa、扫描次数3。最后,把响应曲面所建立数学模型的预测结果与试验的实际结果进行对比,发现两者吻合良好。     

碳纳米管场发射阴极的制备及其场发射特性

采用电泳法将碳纳米管组装到电化学淀积的银台阵列上作为场发射阴极并研究了它的场发射特性.场发射特性测试结果表明:该阴极具有优异的场发射特性,开启电场为2.8V/μm,在应用电场为5.5V/μm时,发射电流密度达到1.7mA/cm2.具有优异的发射性能的原因可以归结到银台的边缘和银台类山状的表面增强了碳纳米管的场致电子发射.该阴极制备工艺简单、发射特性优异,且容易实现大面积制备,可以应用到大面积场发射显示器件中.     

Effect of patterned and aligned carbon nanotubes on field emission properties

The field emission (FE) properties of carbon nanotubes (CNTs) films with different morphologies were simulated and examined. Based on the FE mechanism of aligned CNTs’ emitter the theoretical analysis exhibited the following relations: the FE enhancement factor with the distance between the emitters, the electric field with work function, and the work function with FE enhancement factor. Using the structure-induced CNTs growing method and theoretical results the direction of aligned CNTs could be controlled and the special morphology with different aligned CNTs’ film could be fabricated. Comparing to the experimental results (the medium density and patterned CNTs’ emitters) with the theoretically calculating results the I-V curves had the same trend with only 0.05 mA deviation. Based on the better experimental methods and means the accurate of formula could be further improved by modified the FE properties (Φ, β).