Showing papers in "International Journal of Materials & Product Technology in 2014"

Application of taguchi method in the optimization of laser micro-engraving of photomasks

Abstract: Photomasks are needed to generate various design patterns in the fabrication of liquid crysral displays (LCDs). This paper discusses the use of the Taguchi method of experimental design in optimising process parameters for micro–engraving of iron oxide coated glass using a Q–switched Nd:YAG laser. The effects of five key process parameters – beam expansion ratio, focal length, average laser power, pulse repetition rate and engraving speed – have been explored. The primary response under study is the engraving linewidth. An L16 orthogonal array was used to accommodate the experiments. The study indicated that a minimum linewidth of 18 pm could be obtained with beam expansion ratio of 5x, focal length of 50 mm, laser average power of 0.4 W, pulse repetition rate of 5 kHz, and engraving speed of 5000 mm/min.

A review of friction processes for aerospace applications

Abstract: Friction welding is now extensively used in industries as divergent as sub–sea and aerospace. This paper will focus on some of the variants of friction welding which already provide or may further provide technical opportunities for the aerospace industry. The following techniques are reviewed: Continuous Drive, Inertia, Linear, Taper Stitch, Friction Stir Welding, Friction Pillar Processing, Friction Transformation Hardening, Third–body Friction Joining, and Friction Surfacing. Friction welding is now an established process for the manufacture of aero engine components, and further development work will include a number of emergent process variants and deal with material combinations which are difficult to weld by other processes.

Advanced engineering materials at high temperatures

Abstract: Materials that are available at the present time for use as engineering components are highly limited in their performance at temperatures above about 1000°C in corrosive environments. There is probably no satisfactory material for service in air above 1400°C and there is only a restricted selection of materials in view including silicon nitride based materials, silicon carbide based materials, and carbon–carbon–silicon carbide composites. This article summarizes the findings of several recent workshops concerned with high–temperature engineering ceramics, and covers nitrogen ceramics, ceramic–ceramic composites, ceramic coatings, Zr02–based ceramics, non–oxide ceramics, ceramic toughening mechanisms, and the microstructure and processing of engineering ceramics. Progress towards improved ceramic properties is not automatic, and many severe problems remain. Developments are needed in: oxidation resistant coatings for carbon–carbon composites, and for super alloys; particulate dispersants of controlled morphology suitable for Si3N4–based and SiC–based materials; high–stability fibres with non–reactive interfaces in refractory matrices; sintering mechanisms of monolithic and of composite ceramics; other high–temperature materials such as borides, silicides, carbides; detection of small flaws in ceramics; data on the mechanical properties of ceramics at temperatures above 1400°C; other methods of preparation of ceramic microstructures; ceramic toughening mechanisms and their interactions.

A review of benchmarking literature: a proposed model for implementation

Abstract: This paper presents a generic conceptual benchmarking model which can be applied in manufacturing and service operational environments. The literature dealing with benchmarking was investigated and integrated in the form of a practical model for the implementation of benchmarking. The proposed model and associated framework have both strategic and operational implications for managers as they attempt to gain a competitive advantage in the marketplace.

Mathematical modelling of laser materials processing

Abstract: Laser materials processing involves a wide range of transport phenomena, power density (up to 1012W/cm²) and interaction time (up to picoseconds) for processing objects with sizes ranging from nanometres to metres The art of modelling this novel process is to develop a proper understanding in selecting the appropriate transport phenomena and boundary conditions for specific applications This paper summarizes modelling efforts to date, on laser heat treatment, non–equilibrium synthesis, alloying, cladding, welding, cutting, drilling, chemical vapour deposition, and ablation processes For each process, the transport phenomena, boundary conditions, governing equations, solution techniques and applicability and limitations are reviewed An extensive bibliography is provided for further reading of the interested scientists and engineers

Shot peening optimisation by means of 'DOE': Numerical simulation and choice of treatment parameters

Abstract: Shot peening is widely used to improve the fatigue properties of cyclically loaded mechanical components. The benefits of the treatment, which are mainly due to the compressive residual stress field induced in the surface layers of material, depend on the correct choice of the peening parameters. However, many times the choice of the treatment parameters is made by following empirical considerations, that do not make it possible, for the particular mechanical application, to set the most important factors at their best levels. So, an appropriate procedure, suitable for the different applications, would be necessary to optimise the treatment parameters and to address the choice of their best levels. 'Design of Experiment' (DOE) was applied to the results obtained from the numerical simulation of shot peening (impact of one or more spheres on an infinite smooth steel target), and permitted a choice to be made of the best levels of the treatment parameters in a cheap and fast way.

Brake vibration and noise: reviews, comments, and proposals

Abstract: Automotive brake noise and vibration control have become increasingly important for the improvement of vehicle quietness and passenger comfort. Studies of the problem can be traced back as early as the mid–1950s, but progress has been mainly confined to the explanation of mechanisms and the identification of the sources of brake noise and vibration. Many aspects of the problem still remain unsolved because of the complexity of the problem itself. This paper presents a comprehensive review of previous research on brake noise and vibration. The previous studies on the sources and contributions of drum and disc brake noise and vibration, on the methods and mechanical models used in experimental, numerical and theoretical investigations, and on the materials for brake friction and damping applications are summarised and discussed. The opinions and suggestions of the authors are presented with emphasise on the computer models with dynamic friction considerations and on the potential application of advanced structural composites.

Preparation of zirconia–ceria powders by coprecipitation of a mixed zirconium carbonate in water with urea

Abstract: Ceria zirconia precursors were obtained by applying the urea hydrolysis method to Zr–oxychloride and Ce–nitrate solutions. Dewatering–dying procedures, such as freeze drying (FD) and acetone–toluene–acetone (ATA), were compared with the usual thermal method to assess their suitability for yielding fine, aggregate–free powders for the preparation of ceria–zirconia sinters. The characteristics of the powders before and after calcinations are discussed. The advantage of the ATA method is based on the fact that the formation of hard agglomerates is avoided, high specific surface is achieved and the tetragonal form was the only phase crystallizing on calcination of the chemical precursor.

The extrusion of hollow profiles with a gas pocket behind the bridge

Abstract: Extrusion welding in porthole die extrusion of aluminium was investigated experimentally, using two different modular porthole extrusion dics. The die design allowed removal of the metal rests from the ports and the welding chamber of the die alter extrusion. The metal residue was then inspected to check whether the die cavities had been completely filled wilh metal during extrusion and to map to what extent these conditions influenced extrusion welding. The experiments aimed at extrusion conditions creating low pressure and partial filling of metal inside the welding chamber in order to investigate how these conditions of extrusion affect the quality of the extrusion seam. Extrusion conditions giving extrusion welds of insufficient strength and ductility were mapped in the experiments. The extrusion welds were tested with regard to mechanical properties in the direction transverse to the seam weld, both using tensile testing and fracture mechanics testing.

An experimental investigation of the material flow inside the bearing channel in aluminium extrusion

Abstract: The metal flow inside various bearing channels in aluminium extrusion has been investigated, using different grid pattern techniques. After extrusion the die channel was partitioned and removed from the metal rest. The contact conditions in the aluminium/die land interface during the press cycle were then evaluated from the visual appearance of the surface of the die channel after removal of the metal rest. Experiments performed in long choked die channels showed that the metal would stick to the die wall in the inlet region. However, in the outlet region the extrusion metal would slide against the die wall. Between these two regions there was a sticking/sliding transition point (line). In the sticking region there was a layer of metal adjacent to the die channel wall, which flowed with a considerably lower velocity than the rest of the cross–section which showed plug flow. Experiments performed in a die with zero die bearing length, showed that an outer surface layer of 0.2 mm thickness, would have a slightly lower axial flow velocity than the rest of the cross–section which showed plug flow. Finally, experiments performed in a laboratory porthole extrusion die working with low pressures in the outlet region and the welding chamber showed that the contact conditions of the aluminium/die interface would change from sticking deep inside the die to sliding along a sticking/sliding transition line located near the die outlet. In all cases a more or less completely covering adhesion layer of extrusion material was observed to form on the die surfaces exposed to sliding metal.

Effect of stress ratio on fatigue crack growth

Abstract: Crack growth data of 6061–T6 aluminium alloys were analysed to study the effect of stress ratio. The life of the specimen decreased as the maximum stress intensity increased. The data covered R values for 0.0, 0.1, 0.2 and 0.3 and a good correlation was obtained for U = ((13.5 + 6.0)/l000)ΔK + 1.4R. A crack growth rate equation was also developed.

Design for recycling: new paradigm or just the latest 'design–for–X' fad?

Abstract: It is clear that designers in most if not all industries will soon be formally challenged with ensuring that their products can be disposed of acceptably. Design for disposal/recycling is introduced as a broader, more accurate term than design for recycling. Some recycling principles are first briefly reviewed. Then we consider why and under what conditions it makes sense to design for recycling. Finally, we consider how designers should go about designing for recycling. A number of heuristics or tentative rules for design for disposal/recycling are discussed. It is concluded that a life–cycle approach to design is required. Thus, researchers must continue to quantify the advantages of source reduction. Manufacturers must continue to develop new reprocessing techniques. Designers must continue to apply design for disposal/recycling heuristics when their tradeoffs with other requirements make sense. Finally, all involved must continue to explore the product life cycle to better understand all the consequences of every design decision.

Safety estimation for construction units with cracks under complex loading

Abstract: To evaluate the safety of components with cracks subject to complex stresses, the author introduces a generalized, practice–oriented fracture criterion (ESIF–criterion), which agrees with the assertions of numerous previously known criteria and can be confirmed by a number of experiments. Apart from the determination of safety factors to prevent fractures, this fracture criterion also makes it possible to answer questions regarding the permissible maximum loads to be applied to construction components, the critical crack lengths and the direction of crack propagation in case of fracture. The usefulness of the fracture criterion for the evaluation of the safety of building components is demonstrated in examples.

The role of rare earth elements in the development of magnesium base alloys

Abstract: This paper examines the importance of rare earth metals in the development of magnesium alloys, and their effect on mechanical properties and corrosion resistance. Examples are given of commercial and some experimental alloys, and their advantages and limitations are briefly discussed. A number of alloy compositions that are suitable for the production of shapes using sand, gravity die and precision (e.g. lost–wax) casting techniques, and offering a range of properties, are in commercial use and new alloys are being introduced. No alloy has yet been developed which is suitable for high–pressure die casting. Although a number of alloy compositions offer attractive properties in the wrought condition, little commercial use has been made of them. Rare earth elements are being studied in connection with rapid solidification techniques and a number of compositions offering high ambient–temperature strength and excellent corrosion resistance have been reported. Finally, opportunities for further research and development work are briefly discussed.

Modern ferrite technologies and products

Abstract: This is a review of the most important aspects of ferrite manufacture, concentrating on several soft ferrites. Some information also relates to hard ferrites. The article describes the state of the art, recent technological developments and ferrite applications, as well as future trends. A collection of publications on the subject is included.

Concurrent Engineering for Composites

Abstract: Faced with increasing global competitiveness, the issues of high costs, product robustness, and long lead times associated with product development are emerging in forefront of the problems facing American industry. It is increasingly clear that a significant (70–80%) percentage of system life cycle costs are committed during the phase of concept development and this is of special significance in composites were design decisions are highly coupled. The continued growth of composites is thus dependant on both development of low–cost fabrication technologies and adoption of the philosophy of concurrent engineering. It is essential that the early decisions are made based on the integration of all phases of product development. In this paper we discuss the need for concurrent engineering methodology for composites, and present framework for such an approach.

Thin thermal barrier coatings for internal combustion engine components

Abstract: Contrary to the thick thermal barrier coating approach used in insulated diesel engines, this paper investigates the merits of thin coatings. Transient heat transfer analysis indicates that the temperature swings experienced at combustion chamber surfaces depend primarily on material thermophysical properties, i.e. conductivity, density, and specific heat. Thus, cyclic temperature swings should be alike whether thick or thin (less than 0.25 min) coatings are applied. Furthermore, thin coatings would lead to lower mean component temperatures and would be easier to apply than thick coatings. The thinly–coated engine concept leads to modest improvements in brake power, lower exhaust emissions, and higher exhaust temperatures for possible exhaust gas utilization. Other gains include improved piston–liner tribological behaviour, improved erosion–corrosion resistance, and thus greater component durability. Above all, thin coatings may find application in the large gasoline engine market.

Development of a ceramic antifriction bearing

Abstract: A high quality rolling bearing of silicon nitride was developed by improving the reliability of materials and through numerous experiments on bearing applications. The high strength silicon nitride ceramics for the bearing were developed by the use of sintering additives of yttria and alumina and newly synthesized high α–phase silicon nitride powder of uniform particle size and shape. The developed silicon nitride bearing was evaluated by rolling fatigue test in comparison with various other ceramics and high–carbon chromium steel. The result showed that silicon nitride had the best quality. Moreover, the applicabilites for high–speed bearings, all–ceramic bearings and dry–lubrication bearings were clearly recognized.

The shape optimisation of a connecting rod with fatigue life constraint

Abstract: This paper presents a deterministic approach, considering the fatigue life requirement, in the optimal design of a connecting rod for a newly developed motor–cycle engine. The main idea is to use the finite element method to calculate the stresses upon the connecting rod, and to use sound fracture mechanics theorems, along with material fatigue properties, to calculate fatigue life during the optimisation process. The life requirement is treated as a side constraint, and the volume of the of the connecting rod as the objective function.

Development of heat-resistant cast steel for exhaust manifolds

Abstract: This paper presents a new heat–resistant cast steel developed for exhaust manifolds. Increased exhaust–gas temperatures accompanying recent trends towards leaner combustion and higher engine output have placed a severe thermal load on the exhaust manifold and turbocharger housing. The new cast steel displays better resistance to thermal fatigue than conventional ductile cast irons (DCI) and better cost performance than Ni–Resist (ASTM A439 austenitic ductile cast irons). In the material–design process, the properties required of the material were determined on the basis of statistical analyses. An experiment was then conducted using a test specimen that partially modelled an actual exhaust manifold and a heating simulation was carried out separately from the engine using an exhaust–system simulator. Finally, an endurance test was conducted on an actual exhaust manifold made of the new cast steel using a production system.

Prediction of fatigue life of packaging EMC material based on RBF-SVM

Abstract: This paper applies a radial basis function support vector machine (RBF-SVM) for predicting fatigue life of packaging elastic memory composites (EMC) material. EMC is one of the three dominating materials in the FOL packing. Using EMC to encapsulate the large-scale integrated circuit has predominated research in the areas all over the world. Till now, more than 95% of microelectronic devices are PEMs. In this study, a RBF-SVM model was constructed to predict life of EMC material and the penalty parameter C and nuclear parameter R was optimised. Meanwhile, a comparison between the predictions of BP neutral network, polynomial kernel, sigmoid kernel, and RBF kernel was made. Experiments show that the SVM (RBF-SVM) has higher complexity and prediction accuracy than polynomial kernel and sigmoid kernel have, and its prediction accuracy is far higher than that of BP neutral network model. According to the predictions, RBF-SVM is very suitable for applying in the prediction of fatigue life of packaging EMC material and receives good prediction complexity and accuracy.

Fracture modelling of DP780 sheets using a hybrid experimental-numerical method and two-dimensional digital image correlation

Abstract: This paper is concerned with the construction of fracture envelopes of DP780 sheets using two methods: a hybrid experimental-numerical method; two-dimensional digital image correlation (2D-DIC). For the hybrid method, four types of ductile fracture tests were carried out covering a wide range of stress states on specimens: with a central hole; two symmetric circular notches; flat grooved; and diagonally double-notched. Based on the fracture strain and loading paths identified with finite element simulation, a fracture envelope was obtained by employing the three-parameter modified Mohr-Coulomb fracture model. In addition, the fracture surface strain was directly measured using 2D-DIC. Loading histories of each test were extracted from a surface element of a three dimensional finite element model. The comparison of fracture envelopes constructed by the two methods reveals that there is little difference. Thus, it can be concluded that 2D-DIC is applicable to fracture modelling of DP780 sheets despite the a...

State–of–the–art on linkage between quality, quality costs and productivity

Abstract: This paper reviews the state–of–the–art on the importance of quality, quality costs, and the linkage between quality and productivity. A summary is given of research developments in the discussion of quality costs, in chronological order, using the 'state– of–the–art matrix' (SAM). The paper also identifies the critical issues for research in relating quality costs to productivity, and is intended to stimulate thinking in quality–productivity linkages. Such an understanding is essential to maintain both quality– and cost– competitiveness among products and services. A synthesis of the review of the literature is a starting point for researchers and practitioners to prevent themselves from 'reinventing the wheel'.

Joining dissimilar material combinations: materials and processes

Abstract: Products made of dissimilar material joints are becoming increasingly important in industrial applications due to their numerous advantages. These include not only technical advantages, such as desired product properties, but also benefits in terms of production economics. Joining of dissimilar material combinations is, however, a difficult task due to the great differences in physical and chemical properties which may be present. In this paper, important issues relating to joining dissimilar materials are addressed, with particular emphasis placed on the materials and joining processes. As the development of industrial applications continues, requirements for new products containing dissimilar materials will continue to increase. Therefore, the joining of dissimilar material combinations is and will be a fascinating and challenging subject for R&D, and can play an important role in the manufacture of many products.

Pitting corrosion in copper water pipes

Abstract: Copper as a material for water supplying installations is used to an increasing degree in Austria as it also is elsewhere. Pipes of copper are used in cold– and warm–water supply because good economy is promised by the easy machinability, handling, very good soldering properties and the good corrosion resistance. In spite of the good corrosion resistance there have been corrosion problems leading to great damage which has had to be covered by technical insurance either of the owner or the manufacturer. Corrosion attack occurs as pitting corrosion; three different types are known. The conditions for pitting corrosion will be shown; in most cases a characteristic analysis of the water may be assigned. This does not mean thought, that certain waters automatically cause corrosion. Further conditions must be fulfilled to make corrosion damage probable. Conditions depending on fabrication, handling and use of copper pipe systems will be discussed.

RMS-based optimisation of surface roughness when turning AISI 420 stainless steel

Abstract: The aim of this investigation is to determine the correlation between the cutting conditions such as cutting speed, feed rate, and depth of cut; and surface roughness parameters (Ra, Rq, Rt, Rp, and R3z). The case of turning operation of martensitic stainless steel AISI 420 using CVD coated carbide tool is studied. Full factorial design (43) was adopted. Statistical analysis ANOVA and response surface methodology (RSM) was used to develop quadratic regression models and to determine optimum cutting conditions. It was found that the feed rate (f) is the highest factor influenced the surface roughness parameters when compared with speed and depth of cut. Moreover, a good agreement was observed between the predicted and the experimental surface roughness criteria. The use of lower cutting speed, lower feed rate, and lower depth of cut ensures minimum surface roughness variations.

Delamination in carbon/epoxy plates drilling: tool and feed rate effect

Abstract: The attractive characteristics of carbon fibre reinforced plastics had their widespread use. In order to join different components, drilling is often necessary. It is known that a drilling process that reduces the drill thrust force can decrease the risk of delamination. In this work, three combinations of the drilling process are compared: tool diameter, tool geometry and feed rate. The parameters studied were: thrust force, delamination extension and mechanical strength of the drilled region-bearing test. This work demonstrates that a proper combination of the drilling variables can contribute to reduce the delamination damage and, consequently, enhance mechanical resistance of the joint.

A validated thermo mechanical FEM model of bead-on-plate welding

Abstract: This paper is presenting accurate FEM model of bead-on-plate welds of 316L stainless steels through thermo-mechanical analysis. The model was composed using ANSYS Parametric Design Language (APDL) program. In thermal analysis, mixed mode of volumetric thermal load was used to represent moving heat source. Growing weld bead was accommodated in both the thermal and mechanical models using birth and death technique. Melting phenomenon was modelled by low stiffness and zero plastic strain of melting elements. Results from thermal analysis and subsequent mechanical analysis have been validated. Good agreements of predicted temperature histories, temperature field and residual stress with experimental results confirmed the accuracy of the proposed FEM model.

New product management and product liability

Abstract: In this paper the focus is on the relationship between the development of new products and product liability. Based on the European Communities Directive, it is argued that product liability is an issue to be taken seriously in each of the stages of developing, manufacturing and marketing a product. On no account should matters of product liability be of interest to a company's legal department only.

The use of decision support systems for the efficient selection and design of composites and their products

Abstract: The tailorability of composites for specific applications has been one of its greatest attractions, and simultaneously one of its most perplexing challenges The wide choice of materials combinations, processing methods and shapes possible, present bewildering problems of selection To achieve fast strategic decision making, the problem of selection must be reduced to its main elements through the deselection (or rejection through comparison) of concepts ill–suited to the specific requirements under consideration The process of deselection (or screening) assists the decision making team (or individual) by reducing the number of viable concepts that would then undergo a detailed analysis for suitability This allows a rapid movement through the list of alternatives reducing the number of final concepts to only a few The ultimate purpose is to focus quickly on the most viable and attractive alternatives In this paper we discuss the stages involved in the composites' product design process whilst emphasizing the development of an electronic environment for a decision support tool to aid the design team towards the successful execution of the product realization process The basic strategy being reinforced through this system is that of limiting conflict without skimping on quality Simple, yet powerful tools such as discrimination charts and tables can be used to accelerate the decision making process, even in areas where decisions are highly interrelated The approach described here favours conflict resultion through deselection, allowing multiple, simultaneous alternatives to be carried forward The use of comparative rankings allows the decision makers to access alternatives even if the superiority of one cannot be readily quantified