Optimal Neural Network Model for Characterization of Process-Induced Damage in Drilling Carbon Fiber Reinforced Epoxy Composites

In this paper, a method for robust design of a neural network (NN) model for prediction of delamination (Da), damage width (Dw), and hole surface roughness (Ra) during drilling in carbon fiber reinforced epoxy (BMS 8-256) is presented. This method is based on a parametric analysis of neural network models using a design of experiments approach. The effects of number of neurons (N), hidden layers (L), activation function (AF), and learning algorithm (LA) on the mean square error (MSE) of model prediction are quantified. Using the aforementioned method, a robust NN model was developed that predicted process-induced damage with high accuracy.     

An integrated system for process planning and cost estimation in hole making

The process planning function plays a critical role not only in computer integrated manufacture, but also in the economics of batch manufacturing. This paper describes the development of a generic knowledge-based system for process planning and cost estimation in the hole making process. The main function of the system, besides estimating the cost of production, is to recommend appropriate processes, their sequence and their respective machining conditions in order to obtain the required product specifications. The system has been implemented in a manufacturing organisation. The results obtained have indicated that in addition to cost savings the system also preserves the consistency in planning and cost estimation.     

提高脉冲激光打孔质量的措施

分析JG-2A型脉冲激光器打孔过程中存在的质量问题及其影响因素。同时提出了改善打孔质量的措施：（1）根据最小二乘法原理建立脉冲激光能量经验公式来选取工艺参数；（2）谐振腔超声调制法；（3）材料的热吸收效应法。在实际应用中，打孔质量明显改善。     

基于SolidWorks的相似零件快速创成

介绍了利用Solidworks软件复杂功能，建立系列零件设计表即Excel表，通过其对配置的驱动，自动生成三维相似零件，从而建立相似零件库。该方法简单实用，有效地缩短了设计时间。     

Laser Ablation and Laser-Hybrid Ablation Processes: A Review

Laser beam machining (LBM) has proven its applications and advantages over almost all the range of engineering materials. It offers its competences from macro-machining to micro- and nano-machining of simple-to-complex shapes. The hybrid approaches in laser ablation have demonstrated much improved results in terms of material removal rate, surface integrity, geometrical tolerances, thermal damage, metallurgical alterations, and many more. The flipside of LBM is the existence of universal problems associated with its thermal ablation mechanism. In order to alleviate or reduce the inherent problems of LBM, a massive research has been done during the past decade in order to build a relatively new route of laser-hybrid processes. This paper reviews the research work carried out so far in the area of LBM and its hybrid processes for different materials and shapes. The article also highlights the research gaps and future research directions in the context of laser and laser-hybrid ablation.     

Iron and niobium based additives in magnesium hydride: Microstructure and hydrogen storage properties

In this study, powder mixtures of MgH₂ + 2 mol.% X, with X = Nb, Nb₂O₅, NbF₅, Fe, Fe₂O₃, FeF₃, were processed by mechanical milling at liquid nitrogen temperature (cryomilling). The effect of additives on crystalline structure, thermal properties and hydrogen storage properties of the mixtures were investigated. Morphological investigations indicated a heterogeneous particle size distribution of the powder mixtures and a fine dispersion of additive particles (FeF₃) in the MgH₂ matrix. High resolution synchrotron radiation X-ray diffraction (SR-XRD) data followed by Rietveld refinements showed a significant reduction on crystallite size for the samples containing fluorides (11 nm) in comparison with the pure MgH₂ sample (29 nm). This was related to the mechanical behavior of fluorides during milling with MgH₂, which act as a lubricant, dispersing and/or cracking agent during milling, and thus helping to further reduce MgH₂ particle size. DSC analysis revealed that fluorides (NbF₅, FeF₃) are much more effective than oxides (Nb₂O₅, Fe₂O₃) and the transition metals (Nb and Fe), respectively, in reduction the desorption temperature. Furthermore, Nb₂O₅ is more efficient than Fe₂O₃. Finally, the best results for desorption kinetics were observed for the fluorides: NbF₅ and FeF₃ (equivalent effect and consistent to the DSC analysis) followed by the oxides: Nb₂O₅, Fe₂O₃ and Nb. The addition of Fe was not efficient in comparison with the pure cryomilled sample.     

Experimental investigation,prediction and optimization of cylindricity and perpendicularity during drilling of WCB material using grey relational analysis

Manufacturing is always the heart of majority of industries. Drilling is an extremely important and an essential machining process which requires a lot of attention as in most of the cases it is required for assembly purposes. Majority of the holes produced during drilling are made with the help of Vertical Machining Centre (VMC) meant for pin- hole assembly. Though the tolerance is within limit, assembly problems arise due to the improper geometry of these holes. Various geometrical tolerances like cylindricity, circularity, perpendicularity and position errors are responsible for such assembly problems. This investigation is focussed on cylindricity and perpendicularity in the drilling of Wrought Cast Steel Grade B (WCB) material using SOMX 050204 DT insert. In this work, effect of machining variables like cutting speed, feed rate and depth of cut (canned cycle) are investigated and optimized using grey relational analysis (GRA). Reliable experiments are conducted based on a 3³ full factorial, replicated twice. Second order regression models are developed for predicting cylindricity and perpendicularity. The models’ adequacy has been checked by calculating correlation coefficient. It shows that the developed models are well fitted for the prediction of responses within the specific range of input variables.     

Tool materials influence on surface roughness and oversize in machining glass fiber reinforced polypropylene (GFR-PP) composites

Glass fiber reinforced Polypropylene (GFR-PP) is used in manufacturing industries like bicycles, auto bodies, aircraft, and civil applications due to superior properties. Machining of fiber-reinforced plastics is problematic especially when drilling due to their inherent in-homogeneity, anisotropy and limited plastic deformation. Drilling is often required to facilitate the assembly of the parts to get the final products. Surface quality in drilled composites is an essential design characteristic in many situations, such as accurate fits, aesthetic requirements, etc. The present work deals with detailed investigation on the influence of tool materials and machining parameters during drilling of GFR-PP composite material. The study mainly focused on machined surface quality such as surface roughness of the drilled hole and dimensional inaccuracies such as oversize of the hole. The better dimensional and surface quality of drilled hole is observed from solid carbide drill with a spindle speed of 2500?rpm and a feed rate of 0.05?mm/rev. Regression model is developed using experimental data for estimating the surface roughness and oversize. The developed model has high R-sq value which shows the strong relationship between the model and the response variables. The effect of drilling process parameters and associated interactions are discussed in detail.     

Evaluating accidents in the offshore drilling of petroleum: Regional picture and reducing impact

This study examined several accidents over the last 56 years in the offshore drilling of petroleum. The aim is to examine the situation in relation to jack-ups, drill ships, semi-submersible and platforms and have a better awareness and understanding which may reduce the number of accidents. The materials examined were available published reports and data on exploration and production activities. From 219 accidents recorded the highest was due to blowouts with 46.1%, followed by storms and hurricanes with 15.1% and structural failures with 11.4%. High fatalities occurred at the Funiwa 5 platform in Nigeria with 230, the Piper Alpha platform in the North Sea with 167 and the Keilland semi-submersible in Norway. Other high fatalities were recorded at the Ocean Ranger fire and sinking, Java Sea sinking, Bohai 2 and Bohai 3 fire and sinking. Worker training and discipline must be maintained at a high level. The facilities must be kept sea-worthy and reliable through regular maintenance.     

保护层一次钻爆技术在三峡工程的研究与应用

从孔间、孔内双微差起爆和孔底设置柔性垫层分析“梯段炮孔加柔性垫层”的作用成因；从水平预裂和梯段孔深的确定分析“梯段炮孔加水平预裂”的作用成因，并通过试验及爆前、爆后检测和检查，说明这两种保护层一次钻爆技术理论上是可行的，在实践上很适合大中型水电工程保护层开挖。