Improved solutions for job shop scheduling problems through genetic algorithm with a different method of schedule deduction

This paper details the studies on the use of single mesh size garnet abrasives in abrasive waterjet machining for cutting aluminum. The influence of three different single mesh size abrasives, pressure, traverse rate, and abrasive flow rate; on depth of cut, top kerf width, bottom kerf width, kerf taper, and surface roughness are investigated. Experiments designed using standard L9 orthogonal array and the analysis of variance helped in the determination of highly significant, significant and weakly significant cutting parameters. Single mesh size abrasives are found to yield decreased surface roughness than multi mesh size abrasives. Based on these studies, response equations are developed to predict the target parameters. Using single mesh abrasives, a practitioner not only can cut faster but also achieve reduced surface roughness.     

Effects of particle size, polishing pad and contact pressure in free abrasive polishing

The objective of this research is to better understand the mechanisms of material removal in the free abrasive polishing process. Experiments were carried out to understand the effects of particle size, polishing pad and nominal contact pressure on the wear rate and surface roughness of the polished surface. A theoretical model was developed to predict the relationship between the polishing parameters and the wear rate for the case of hard abrasive particles sandwiched between a soft pad and a workpiece (softer than the abrasive particles). Experimental results and theoretical predictions indicate that the wear rate increases with an increase in particle size, hardness of polishing pad and nominal contact pressure, and with a decrease in elastic modulus of the polishing pad. Surface roughness increases with an increase in particle size and hardness of polishing pad, and nominal contact pressure has little effect on the roughness. A dimensionless parameter, wear index which combines all of the preceding parameters, was introduced to give a semi-quantitative prediction for the wear rate in free abrasive polishing. It is also suggested that when polishing hard material, in order to achieve a high materials removal rate and a smooth surface, it is preferable to use diamond as the polishing particles because of their high deformation resistance.     

A review on the use of dielectric fluids and their effects in electrical discharge machining characteristics

Electrical discharge machining (EDM) is one of the earliest non-traditional machining processes. EDM process is based on thermoelectric energy between the work piece and an electrode. In electrical discharge machining (EDM), a process utilizing the removal phenomenon of electrical discharge in dielectric, the working fluid plays an important role affecting the material removal rate and the properties of the machined surface. Choosing the right dielectric fluid is critical for successful operations. This paper presents a literature survey on the use of dielectric fluids and also their effects in electrical discharge machining characteristics.     

A comparison of some methods for measuring the size distribution of two-dimensionally clustered latex particles in TEM images using mathematical morphology

The particle size distribution of polymer latexes of, for example, polybutadiene can be measured on transmission electron micrographs using image analysis methods. By taking suitable measures in preparing the sample it can be ensured that the image only consists of projections of two-dimensional clusters of adhering latex spheres. For the deagglomeration of these clusters a number of methods based on mathematical morphology are discussed. Speed and accuracy of the methods were tested on a personal-computer-based image analysis system and compared to manual measurements. Repeated openings or erosions applied to a binary image are relatively fast global methods with a low accuracy due to the fact that particle diameters are measured in whole numbers of pixels; only the horizontal diameters of rectangular pixels are measured. With an iterative method the individual components of the clusters are found by repeated conditional thickening of the erosion kernels. The method is accurate but very slow due to the large number of processing steps. The watershed method as applied to the original grey-scale transmission electron micrograph makes use of the sharp local maxima which arise at the interface of the projection of two adhering particles. This method is as accurate as the iterative method, but about eight times as fast.     

用双重曲柄滑块机构范成加工高速凸轮的研究

通过对高速凸轮的设计加工问题进行研究,提出了一种新型的由双重曲柄滑块机构组成轮轮廓范成装置。对该范成凸轮的运动动力学进行了分析,并对加工刀具的误差补偿及其它主要的加工工艺进行了简要讨论。     

Integrating Box-Behnken design with genetic algorithm to determine the optimal parametric combination for minimizing burr size in drilling of AISI 316L stainless steel

This paper illustrates the methodology of genetic algorithm (GA) based multi-objective drilling process optimization. The optimal values of cutting speed, feed, point angle and lip clearance angle for a specified drill diameter were determined using GA, which simultaneously minimize burr height and burr thickness at the exit of holes during drilling of AISI 316L stainless steel. The burr size models required for GA optimization were developed using response surface methodology (RSM) with drilling experiments planned as per Box-Behnken design. The GA optimization results reveal that point angle has a significant role in controlling the burr size.     

7055铝合金高速加工表面完整性对疲劳寿命的影响

为优化高强度铝合金高速铣削工艺参数,提高构件的疲劳寿命,通过高速铣削及疲劳试验,研究了7055铝合金高速铣削工艺参数对表面完整性的影响以及表面完整性对疲劳寿命的影响。结果表明:铣削表面残余应力均呈现为压应力;每齿进给量对表面粗糙度的影响大于铣削速度的影响,铣削速度和每齿进给量对表面显微硬度的影响不显著;7055铝合金试样的疲劳寿命随表面粗糙度增大而降低,随表面残余压应力增大而提高;在试验参数范围内最佳的铣削参数为铣削速度1 100 m/min、每齿进给量0.06 mm/z,试件的表面粗糙度为Ra0.327μm,表面显微硬度为187.44 HV0.025,表面残余应力为-177.7 MPa,疲劳寿命为1.275×105次。     

螺旋铣孔工艺参数对CFRP分层的影响研究

选取螺旋铣孔过程中切削速度、轴向进给以及偏心量为对分层产生主要影响的工艺参数。为得到建模所需数据,切削实验采用三因素三水平全因素实验设计,并使用螺旋铣孔工艺专用涂层刀具。基于实验数据,通过多元非线性回归-响应曲面法,建立分层缺陷和螺旋铣孔工艺参数之间的数学模型,并用MATLAB画出响应曲面图,最后通过曲面图直观地分析了三种参数对分层的影响,指出两个导致分层的主要因素。     

遗传算法求解多方案设计问题的研究

本文在智能设计中提出了求解多方案设计问题的遗传算法,讨论了遗传算法中求解多方案问题的关键技术,包括一种改进的遗传算法,避免了标准遗传算法早收敛于局部优解和加快了全局最优的收敛速度,给出了在机床模块综合中多方案求解实例,遗传算法有效地解决模块选择与组合问题中的“组合爆炸”问题。     

Impact of reliability on warranty: A study of application in a large size company of electronics industry

This paper presents product reliability on component basis and investigates the possible effects on warranty which constitutes a non-technical issue. Product reliability is a key factor, which is used in considering the warranty period. It plays a significant role that a mistake in warranty forecasting could cost a lot for companies. The objective is to empirically examine the nature of general reliability of manufactured goods and conduct a case study in an electronics company. In this regard, reliability will be stated from the actual manufacturing point of view. A case study was applied in manufacturing industry. LCD TVs were undertaken to follow. To test reliability, a parametric Weibull model was used and hazard rates of products were estimated with linear regression method. For this research work, the lifetime data obtained by service departments, censored both left and right. Data were used in MINITAB14 to produce the reliability results of the LCDs to reveal the relationship between product reliability and product warranty in the consumer electronics industry. In this manner, this paper would help the company to decide whether it is favorable to extend the warranty period based on the failure findings.     

谐波齿轮传动单级传动比极限的研究

本文针对诸因素对谐波齿轮传动装置强度的影响,进行了理论计算分析为提高柔轮强度,进一步经下限提供了理论依据,得到谐波齿轮传动单级传动比的下限值。     

基于响应曲面法的Aermet100磨削力预测模型研究

为了优化超高强度钢Aermet100磨削参数,采用响应曲面实验法,对Aermet100平面磨削力展开了预测模型研究,建立了磨削力的全系数项回归预测模型;采用显著性检验方法,对磨削力预测模型的显著项和不显著项进行了分析,去除了不显著项,对磨削力预测模型进行了简化;基于所建模型,分析了磨削参数对磨削力的影响规律。结果表明:简化的磨削力预测模型误差小,可对磨削力进行有效预测;磨削深度ap与工件速度vw、砂轮速度vs的交互作用对磨削力影响显著;磨削力随着工件速度vw、磨削深度ap的增加而增加,随着砂轮速度vs的增加而降低。     

单目视觉测量系统中目标位姿对图像点灵敏度影响的研究

通过研究单目视觉测量系统中不同位姿物体姿态测量的灵敏度,找到对图像点灵敏度影响的因素和各自占有比例。给出了灵敏度分析的理论模型,通过设计影响图像点灵敏度相关因素的数值分析实验,得出图像点灵敏度与靶板倾角及物距成反比,最大数值灵敏度最大值对应的处的靶面目标姿态,始终位于相机主方向光轴方向上。     

关于开环机构末杆自由度计算方法的研究

本文运用对偶矢量量论定量地分析开环机构中各运动副所容许的相对运动在末杆上的反映，通过计算末杆独立对偶角速度来确定末杆独立运动的数目，从而得到一种求解末杆自由度的方法。