Platinum colloid catalyzed etchingless gold electroless plating with strong adhesion to polymers

Echingless electroless plating (ELP) process that can produce gold thin film with strong adhesion to various polymer films has been developed. We have found that platinum (Pt) colloidal nanoparticles have excellent catalytic activity for ELP. The Pt colloidal nanoparticles can be immobilized via electrostatic interactions on a substrate simply by dipping it into a Pt colloid. Owing to the excellent catalytic property of the Pt nanoparticles, continuous gold thin films can be produced at room temperature using a simple cyanide-free gold electroless plating solution composed of chloroauric acid and hydrogen peroxide. The process requires no surface modifications for the immobilization of the catalyst, and by simple post-annealing the adhesion of the plated films to various polymer films can be improved by three orders of magnitude in comparison to that of “as-deposited” film. The process developed in this work is expected to be an environment-friendly thin metal film deposition process without the use of toxic and hazardous substances.     

Recent advances in engineering design optimisation: Challenges and future trends

Traditional engineering design optimisation which is the process of identifying the right combination of product parameters is often done manually, time consuming and involves a step by step approach. This paper identifies recent approaches to automating the manual optimisation process and the challenges that it presents to the engineering community. Engineering design optimisation is classified based on design evaluation effort and degrees of freedom viewpoints. An overview of different approaches for design optimisation is presented. The study identifies scalability as the major challenge for design optimisation techniques. Large-scale optimisation requires significant computing power and efficient algorithms such as swarm intelligence.     

Identification strategy of error parameter in volumetric error compensation of machine tool based on laser tracker measurements

This paper presents a new method for volumetric verification of machine tools. Beyond the consideration of a particular machine, a general verification methodology is presented based on the type of machine to verify the number and movement of axes and different techniques that can be used.A scheme and kinematic model with the inclusion of the measurement system depending on the kinematics of the machine are presented. The model describes the geometry and kinematics of a real milling machine based on a parametric synthetic data generator, which generates a test with known geometric errors and noise to enable a study of different optimisation techniques and models.Similarly, different errors identification techniques and volumetric verification models are presented and analysed.The paper shows the improvement that occurs in verification by considering optimisation phases, the appropriateness of using new techniques of feedback, and the influence of optimisation parameters. Chebyshev polynomials and its characteristics are presented, as well as a regression function for the new verification model. The new developed technique allows the characterisation of the different errors in the whole workspace of the machine and in less time than direct verification methods.     

Some guidelines for thermodynamic optimisation of phase diagrams

Thermodynamic optimisation of phase diagrams is a procedure that requires considerable experience and skill. The purpose of this article is to furnish certain guidelines that might facilitate the work and improve the quality of the thermodynamic optimisation of phase diagrams using the Calphad method. Some particulars regarding experimental data, Gibbs energy models, constraints on model parameters, and performing the optimisation are discussed.     

Methodology for development of welding procedures and empirical weld process models based on principal component analysis techniques

Abstract

With the increased automation of welding processes, there is a necessity for experimental design techniques that will permit rapid and efficient definition of the range of welding process parameters that may be used to produce acceptable welds for each new application. Such techniques are also required during development of empirical weld process models. In the present study, an experimental design technique based on principal component analysis (PCA) has been developed and shown to be more efficient than the traditional fractional factorial approach to experiment design, weld procedure development, and development of weld process models. Gas tungsten arc (GTA) welding of corner joint sheet steel was selected to exemplify the application of the technique. The boundary of a three­dimensional domain of weld process parameters (welding current, speed, and electrode gap) which could be used to produce acceptable welds when using either flush or edge touch corner joint configurations was satisfactorily approximated using only 25 welds. The PCA based technique was able to resolve differences between the procedural domains of these two joint geometries. The procedural field for the edge touch configuration was found to have a larger range of acceptable welding conditions than that for the flush configuration. Empirical weld process models for these joint configurations were developed using standard multivariable regression analysis techniques and only 25 further welds. Finally, an empirical model for weld width prediction in corner joint GTA welding was developed which includes the effect of current, voltage, torch travel speed, and sheet metal fitup. This model had an R ² value of 86%, with all statistical tests yielding acceptable results.     

Porous ceramic scaffolds with complex architectures

This work compares two novel techniques for the fabrication of ceramic scaffolds for bone tissue engineering with complex porosity: robocasting and freeze casting. Both techniques are based on the preparation of concentrated ceramic suspensions with suitable properties for the process. In robocasting, the computer-guided deposition of the suspensions is used to build porous materials with designed three dimensional geometries and microstructures. Freeze casting uses ice crystals as a template to form porous lamellar ceramic materials. Preliminary results on the compressive strengths of the materials are also reported.     

等通道弯角挤压变形机理模拟与工艺参数优化

通过等通道弯角挤压工艺 (EqualChannelAngularPressing ECAP)能够获得块状超细晶粒材料 (包括亚微米和纳米材料 )。模具几何形状、摩擦条件等工艺参数对挤压过程具有重要影响。本文应用作者自主开发的商品化软件 ,通过大量的有限元模拟 ,研究了过程参数对挤压件变形分布、挤压载荷的影响规律 ,给出了不同模具拐角和圆心角对ECAP挤压件变形区产生的累积等效应变、等效应力和载荷 行程曲线的影响 ,为优化模具形状和获得所要求的挤压件变形分布提供了大量有效的结果和规律。     

Process geometry modeling with cutter runout for milling of curved surfaces

Prediction of cutting forces and machined surface error in peripheral milling of curved geometries is non-trivial due to varying workpiece curvature along tool path. The complexity in this case, arises due to continuously changing process geometry as workpiece curvature varies along tool path. In the presence of cutter runout, the situation is further complicated owing to changing radii of cutting points. The present work attempts to model process geometry in machining of curved geometries and in the presence of cutter runout. A mathematical model computing process geometry parameters which include cutter/workpiece engagements and instantaneous uncut chip thickness in the presence of cutter runout is presented. The developed model is more realistic as it accounts for interaction of cutting tooth trajectory with that of preceding teeth trajectories in computing process geometry. Computer simulation studies carried for this purpose has shown that it is essential to account for teeth trajectory interactions for accurate prediction of process geometry parameters. This aspect is further confirmed with machining experiments, which were conducted to validate this aspect. From the outcomes of present work, it is clearly seen that the computation of process geometry during machining of curved geometries and in presence of cutter runout is not straightforward and requires a systematic approach as presented in this paper.     

A review of rolling system design optimisation

Rapid product development and efficient use of existing resources are key competitive drivers in the steel industry and it is imperative that solution strategies are capable of delivering high quality solutions at low cost. However, traditional search techniques for Rolling System Design (RSD) are ad hoc and users of them find it very difficult in satisfying the required commercial imperatives. This paper presents a comprehensive review of approaches for dealing with RSD problems over the years in terms of modelling and optimisation of both quantitative and qualitative aspects of the process. It critically analyses how such strategies contribute to developing timely low cost optimal solutions for the steel industry. The paper also explores the soft computing based technique as an emerging technology for a more structured RSD optimisation. The study has identified challenges posed by RSD for an algorithmic optimisation approach, especially for evolutionary computing based techniques.     

二氧化碳腐蚀环境下套管选材新方法及应用

目的在油田生产过程中,腐蚀的危害性极大,所以套管材质选择至关重要。生产套管材质选择级别低,二氧化碳腐蚀可能导致套管腐蚀穿孔,严重则会影响正常生产,出现安全和环境问题等。如果套管材质选择级别过高,会造成经济上的浪费。为了使材质选择更加合理,所以进行研究。方法以De.Waard预测腐蚀模型计算的不同材质的长期腐蚀速率为基础,提出了一套新的套管选材新方法。通过该方法对渤海油田A井进行了设计,并通过室内实验对设计结果进行了验证。结果根据实验得到的管材选择结果与管材设计新方法设计的结果一致,验证了该方法的准确性。结论提出了一套适合于CO_2腐蚀环境下套管材质优选的方法:计算不同材质的腐蚀速率,进而转化为长期腐蚀速率,根据套管强度要求,计算出套管最大允许磨损量,最终确定套管选择材质。该套管选材新方法能够在保证井筒完整性和井控安全可控的前提下,有效降低套管材质选择的成本,有利于保证油田开发的经济性。     

Advanced lattice support structures for metal additive manufacturing

Metal additive manufacturing (MAM) of complex parts with overhangs typically requires the use of sacrificial support structures to hold the part during the process. This structures which are built simultaneously with the part, anchors the overhang geometry to the base plate and prevent distortion/curling resulting from thermal stresses. They are necessary, but add constraints to the geometries that the processes can make. The design and selection of support structure can influence the manufacturability of complex metal parts, material and energy utilization, manufacturing time and cost. This study takes a new step on the design and manufacturing a more efficient support through the novel application of lattice structures with very low volume fraction. Experiments were conducted in direct metal laser sintering (DMLS) machine using titanium alloy Ti6Al4V powder. Experimental results revealed that the type of structure, volume fraction and cell size are the main factors influencing the manufacturability, amount of support, and built time of lattice support structures. Lattice supports with very low volume fraction up to 8% were built, saving significant amount of materials used in the support while reducing built time of making MAM parts.     

Modeling and simulation of 5-axis milling processes

5-axis milling is widely used in machining of complex surfaces. Part quality and productivity are extremely important due to the high cost of machine tools and parts involved. Process models can be used for the selection of proper process parameters. Although extensive research has been conducted on milling process modeling, very few are on 5-axis milling. This paper presents models for 5-axis milling process geometry, cutting force and stability. The application of the models in selection of important parameters is also demonstrated. A practical method, developed for the extraction of cutting geometry, is used in simulation of a complete 5-axis cycle.     

Laser beam machining—A review

Laser beam machining (LBM) is one of the most widely used thermal energy based non-contact type advance machining process which can be applied for almost whole range of materials. Laser beam is focussed for melting and vaporizing the unwanted material from the parent material. It is suitable for geometrically complex profile cutting and making miniature holes in sheetmetal. Among various type of lasers used for machining in industries, CO₂ and Nd:YAG lasers are most established. In recent years, researchers have explored a number of ways to improve the LBM process performance by analysing the different factors that affect the quality characteristics. The experimental and theoretical studies show that process performance can be improved considerably by proper selection of laser parameters, material parameters and operating parameters. This paper reviews the research work carried out so far in the area of LBM of different materials and shapes. It reports about the experimental and theoretical studies of LBM to improve the process performance. Several modelling and optimization techniques for the determination of optimum laser beam cutting condition have been critically examined. The last part of this paper discusses the LBM developments and outlines the trend for future research.     

A novel procedure for selection of materials in concept design

This work is concerned with the selection of materials for conceptual product design prior to precise definition of part geometries. The proposed selection method is based on normalized scales of 0 to 100 for all fundamental material properties. The proposed scales are independent of the units which are used for the material property values. Three important transformations of the scales are demonstrated. First, the inverse material property is simply represented by 100 minus the original scale value. For example, if a material scores 83 for weight, then its scale value for lightness is 17. Second, a procedure is given for transformation the “100-scales” of individual properties to the “100-scale” of any derived parameter. Finally, a general procedure is established for the selection of multiple parameters with weighting values if desired. A spreadsheet sample database is presented suitable for teaching or demonstration purposes.     

Optical Diagnostics Study of Gas Particle Transport Phenomena in Cold Gas Dynamic Spraying and Comparison with Model Predictions

Cold gas dynamic spraying (CGDS), a relatively new thermal spraying technique has drawn a lot of attention due to its inherent capability to deposit a wide range of materials at relatively low-operating temperatures. A De Laval nozzle, used to accelerate the powder particles, is the key component of the coating equipment. Knowledge concerning the nozzle design and effect of process parameters is essential to understand the coating process and to enable selection of appropriate parameters for enhanced coating properties. The present work employs a one-dimensional isentropic gas flow model in conjunction with a particle acceleration model to calculate particle velocities. A laser illumination-based optical diagnostic system is used for validation studies to determine the particle velocity at the nozzle exit for a wide range of process and feedstock parameters such as stagnation temperature, stagnation pressure, powder feed rate, particle size and density. The relative influence of process and feedstock parameters on particle velocity is presented in this work.     

State of the art in wire electrical discharge machining (WEDM)

Wire electrical discharge machining (WEDM) is a specialised thermal machining process capable of accurately machining parts with varying hardness or complex shapes, which have sharp edges that are very difficult to be machined by the main stream machining processes. This practical technology of the WEDM process is based on the conventional EDM sparking phenomenon utilising the widely accepted non-contact technique of material removal. Since the introduction of the process, WEDM has evolved from a simple means of making tools and dies to the best alternative of producing micro-scale parts with the highest degree of dimensional accuracy and surface finish quality.Over the years, the WEDM process has remained as a competitive and economical machining option fulfilling the demanding machining requirements imposed by the short product development cycles and the growing cost pressures. However, the risk of wire breakage and bending has undermined the full potential of the process drastically reducing the efficiency and accuracy of the WEDM operation. A significant amount of research has explored the different methodologies of achieving the ultimate WEDM goals of optimising the numerous process parameters analytically with the total elimination of the wire breakages thereby also improving the overall machining reliability.This paper reviews the vast array of research work carried out from the spin-off from the EDM process to the development of the WEDM. It reports on the WEDM research involving the optimisation of the process parameters surveying the influence of the various factors affecting the machining performance and productivity. The paper also highlights the adaptive monitoring and control of the process investigating the feasibility of the different control strategies of obtaining the optimal machining conditions. A wide range of WEDM industrial applications are reported together with the development of the hybrid machining processes. The final part of the paper discusses these developments and outlines the possible trends for future WEDM research.     

A new one-phase material model for the numerical prediction of critical material flow conditions in thixoforging processes

Thixoforging allows one-step forming processes of near-net shape components having excellent mechanical properties. However, the high sensitivity of thixoforging regarding process conditions requires precise modelling and determination of process related parameters. At the same time, simple numerical design proves challenging because of the inaccuracy of existing one-phase material models regarding the shear thinning flow behaviour of semi solid metals. Consequently, this paper deals with the development of a new one-phase material model providing a more precise simulation of materials’ shear rate dependency. By using this model, simulations could be performed, which allowed the prediction of solidification and flow-related component defects.     

Mathematical models in new process development

Mathematical modeling is now established as a growing discipline which offers important tools for tackling process development and process optimization problems. The use of mathematical models for the screening of new ideas in new process development and, in particular, for tackling the inverse problem, where appropriate input parameters are defined by working backwards from an optimum result, offers very attractive and potentially rewarding possibilities. The major barriers to widespread implementation of mathematical models are the lack of constitutive relationships and the lack of information on the properties of many materials.     

Development of expert systems for the design of a hot-forging process based on material workability

Most of the time (and cost) involved in planning hot forging process is related to activities strongly dependent on human expertise, intuition, and creativity, and also to iterative procedure involving extensive experimental work. In this paper, the development of an expert system for forging process design, which emphasizes materials’ workability, is discussed. Details of the forging process design expert system, its basic modules, design and implementation details, and deliverables are explained. The system uses the vast database available on the hot workability of more than 200 technologically important materials and the knowledge acquired from a materials’ expert. The C Language Integrated Production System (CLIPS) has been adopted to develop this expert system. The expert system can address three types of functions, namely, forging process design, materials information system, and forging defect analysis. The expert system will aid and prompt a novice engineer in designing a forging process by providing accurate information of the process parameters, lubricants, type of machine, die material, and type of process (isothermal versus non-isothermal) for a given material with a known specification or code and prior history.     

Integrated Virtual Manufacturing Systems for Process Optimisation and Monitoring

The implementation of an Internet-based Virtual Manufacturing facility for the development and optimisation of new manufacturing processes is presented. The facility integrates advanced process simulation software, a remote machine monitoring system and multimedia technologies to realise a virtual environment for manufacturing process optimisation. Utilising physics-based process simulations, process parameters and operational sequences are evaluated and optimised with respect to desired product features. Having optimised the operation, a prototype of the part can be created at the facility. During prototyping, process parameters are monitored in real-time. A Case Study is presented, where a 3-axis milling operation is defined, optimised and executed using the facility.