bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress intensity factors for semi-elliptical internal surface cracks in autofrettaged thick-walled cylinders
Authors: Lin X B , Smith R A
Published: October 2002

Stress intensity factors for internal semi-elliptical surface cracks in autofrettaged cylinders with and without internal pressures applied are presented. The three-dimensional finite element based displacement method with the crack tip square-root singularity of stresses and strains simulated is used to evaluate the stress intensity factors along the crack front. Both allowing and disallowing the overlapping of crack faces are considered in this investigation, the latter being simulated by considering crack surface contact through a kind of interface element introduced into the cracked area. The residual stress distribution assumed to act on the crack face is obtained according to Tresca's yield criterion with the material assumed to be elastic-perfectly plastic. Three different overstrains of autofrettage are chosen. The results show that the stress intensity factor is generally underestimated if the crack contact that has actually occurred is ignored, which may lead to a danger in the assessment of either fracture strength or fatigue life. Implications of the stress intensity factor results are also briefly discussed, particularly for the prediction of fatigue lives, and it is shown that the full autofrettage treatment might be the most beneficial for increasing the fatigue life of cracks initiated from the inner core.
Variation of the residual stress state in a welded joint during plastic deformation in a 5.0%Cr and 0.5%Mo steel
Authors: Gurova T , Teodòsio J R , Rebello J M A , Monin V
Published: October 2002

The aim of the present work is to verify the variation of the initial residual compressive stress induced by shot-peening, during plastic deformation under uniaxial tension, in a steel with 5.0%Mo and 0.5%Cr, employing test pieces taken from a welded joint where, due to the welding process, there are regions with different mechanical properties (yield strength and tensile strength). The regions of the joint, the base metal, the heat-affected zone and the weld bead exhibited different behaviour. In the heat-affected zone the residual compressive stresses in the longitudinal direction changed to tensile stresses with 0.5-1 per cent plastic deformation. At 3 per cent the stresses attain a maximum tensile value, decreasing in an oscillating manner up to 6 per cent plastic deformation. Beyond this point the test pieces reached a constant tensile value until the fracture. The transverse residual stress values were also modified during the tensile test but no full stress relaxation was observed. Indeed, the initial compressive stress values changed under small applied plastic deformation and after 4 per cent plastic deformation they changed weakly until the test piece fracture. The weld bead was weakly deformed and no effective stress relaxation was observed. In both the longitudinal and the transverse directions, the residual compressive stresses are brought sharply from an initial value of — 470MPa to a minimum of — 250MPa for only 0.5 per cent plastic deformation. No further changes were observed until the fracture of the test piece.
Designing against fretting fatigue: Crack self-arrest
Authors: Moobola R , Hills D A , Nowell D
Published: October 2002

Issues concerned with self-arrest of fretting fatigue cracks at small initial lengths are discussed for a range of well-defined contact geometries. The conditions under which self-arrest will occur are given, together with the maximum tolerable initial flaw size, beyond which self-arrest may not be anticipated.
Recent developments and applications in electronic speckle pattern interferometry
Authors: Petzing J N , Tyrer J R
Published: October 2002

Electronic speckle pattern interferometry (ESPI) is a wholefield non-contact optical metrology technique for displacement measurement, based on the optical physics of surface-generated laser speckle. Since its inception during the early 1970s ESPI has gradually evolved into different optical designs and has been applied to a range of engineering and non-engineering applications. Development of ESPI has continued during the 1990s with the introduction of new laser and optical technology into the interferometers, allowing further optimization and extending the potential applicability of the technique. This review considers the most notable developments of interferometer design and application that have occurred and been widely published during the 1990s, and examines the current and near-future direction of research into the technique.
On the relaxation of interface stresses during creep of ferritic steel weldments
Authors: Kimmins S T , Smith D J
Published: October 2002

This paper examines the interaction between materials joined together that individually have high and low degrees of creep resistance. A specific example considered is an overtempered layer of the heat-affected zone of a ferritic steel weldment which lies between stronger materials. Experimental evidence is reviewed which shows that adjacent strong and weak layers of material creep relatively independently of each other when a tensile stress is applied perpendicular to the plane of the layer.

Finite element analyses are presented of a simplified model of a narrow and weak layer of material sandwiched within much stronger material. A constant load is applied perpendicular to the plane of the weak layer and the stress and strain distributions are considered after the accumulation of a significant degree of creep deformation. If the finite element mesh is constructed in a conventional manner it is shown that significant constraint of the narrow, weak layer is to be expected. However, if the mesh is modified so as to allow sliding of adjacent elements then the constraint of the weak zone can be virtually eliminated. It is proposed that finite element models of creeping weld interfaces need to be modified to allow a greater relaxation of the interface stress if they are to agree with experimental studies.
A method for reducing the influence of quarter-wave plate errors in phase stepping photoelasticity
Authors: Ajovalasit A , Barone S , Petrucci G
Published: October 2002

The phase stepping technique has recently been applied to the automated analysis of photoelastic fringes to determine the isoclinic parameter and the relative retardation. Generally, in these methods the error of quarter-wave plates, due to common manufacturing tolerances, influences the determination of the isoclinic parameter and the fringe order. In this paper a new phase stepping method in which the influence of quarter-wave plate error is null on the isoclinic parameter and negligible on the fringe order is proposed. The theoretical results have been confirmed by experimental tests.
Characterization of residual stresses generated during inhomogeneous plastic deformation
Authors: Lorentzen T , Faurholdt T , Clausen B , Danckert J
Published: October 2002

Residual stresses generated by macroscopic inhomogeneous plastic deformation are predicted by an explicit finite element (FE) technique. The numerical predictions are evaluated by characterizing the residual elastic strains by neutron diffraction using two different ( hkl) reflections. Intergranular residual elastic strains between subsets of grains are predicted numerically and verified by neutron diffraction. Subsequently, the measured residual strain profiles in the test samples are modified by the intergranular strains and compared to the engineering predictions of the FE technique. Results compare well and verify the capability of the numerical technique as well as the possibilities of experimental validation using neutron diffraction. The presented experimental and numerical approach will subsequently be utilized for the evaluation of more complicated plastic deformation processes resembling forming operations.
Postbuckling of composite laminated plates under biaxial compression combined with lateral pressure and resting on elastic foundations
Authors: Shen H-S
Published: October 2002

A postbuckling analysis is presented for a simply supported, composite laminated rectangular plate subjected to biaxial compression combined with lateral pressure and resting on a two-parameter (Pasternak-type) elastic foundation. The initial geometrical imperfection of the plate is taken into account. The formulations are based on the classical laminated plate theory, including plate-foundation interaction. The analysis uses a perturbation technique to determine the buckling loads and postbuckling equilibrium paths. Numerical examples are presented that relate to the performances of antisymmetric angle-ply and symmetric cross-ply laminated plates subjected to combined loading and resting on Pasternak-type elastic foundations from which results for Winkler elastic foundations are obtained as a limiting case. The influence played by a number of effects, among them foundation stiffness, the plate aspect ratio, the total number of plies, fibre orientation and initial lateral pressure, is studied. Typical results are presented in dimensionless graphical form.
A theoretical and experimental study of alternating current stress measurement under different loading modes
Authors: Chen K , Brennan F P
Published: October 2002

This paper presents some experimental studies on the inverse magnetostriction effect that were recently conducted at University College London (UCL) by the authors. A form of alternating current field measurement (ACFM) instrumentation, which was developed to detect and size surface defects in ferromagnetic components, was used in the present study to induce a low alternating magnetic field near the surface of a mild steel specimen and to pick up the influences of applied stresses on that field. The mild steel specimen was tested both in four-point bending and uniaxial tension to investigate the response under different stress modes within the elastic region. Consistent and repeatable results have been obtained under both bending and tension loading modes when different probe types with different inducing frequencies are used. In the present paper, the mathematical model of half-space electromagnetic induction which was recently developed at UCL has been combined by the authors with the previously published fundamental relationships between stress and magnetization. The combination gives a new model, which has been introduced here to demonstrate that stress will alter the magnetic field. This suggests that ACFM technology can be further developed into that of alternating current stress measurement (ACSM) for industrial applications.
Study of through-thickness residual stress by numerical and experimental techniques
Authors: Rasouli Yazdi S , Retraint D , Lu J
Published: October 2002

The quenching process of aluminium alloys is modelled using the finite element method. The study of residual stress field induced by quenching is divided into two: the thermal and mechanical aspects. In the thermal problem, the general heat conduction equation is solved and the temperature field during quenching is calculated. In the mechanical problem, the calculated temperature field and mechanical properties are used to predict the residual stress field.

In this paper, the two different boundary conditions used in the thermal problem are examined. The first is surface convection using the appropriate heat transfer coefficient. The second is the temperature variation measured at the surface of the part. These boundary conditions are compared, and the advantages and the drawbacks of each are shown.

The influence of different quenching parameters on the level of residual stress is studied. To validate the quenching modelling, the incremental hole drilling and neutron diffraction methods are used to measure the residual stress field in the studied parts. The hole drilling technique has been adapted to measure the residual stress through a larger thickness of the part. The aim of this paper is the combination of numerical and experimental techniques for the investigation of the through-thickness residual stress field.
Towards the standardization of in vitro load transfer investigations of hip prostheses
Authors: Ke X , Sutton M A , Lessner S M , Yost M
Published: October 2002

The effect of optical refraction at an interface between optically dissimilar media is modelled in order to apply the principles of three-dimensional digital image correlation (DIC) to measure deformations on submerged objects accurately. Using an analytical formulation for refraction at an interface, a non-linear solution approach is developed to perform stereo calibration. The proposed method incorporates a simplified parametric representation for the orientation and position of an interface(s), accounting explicitly for the effects of refraction at all such interfaces in the path of each stereo camera. Separating the calibration process into two parts, a modified bundle adjustment process with an updated Levenburg–Marquardt (LM) non-linear optimization algorithm is employed to determine (a) intrinsic and extrinsic stereo camera parameters without interface refraction and (b) orientation and position of each planar interface. Detailed simulations demonstrate the efficiency, accuracy, and stability of the methodology when using multiple images of a grid pattern undergoing general rigid body motion, even in the presence of Gaussian noise in the sensor plane measurements, providing a robust framework for practical implementation of the methodology for submerged object measurements.
Equivalent stress and total strain range predictions for multiaxial states of stress and strain
Authors: Hardy S J , Gowhari-Anaraki A R , Pipelzadeh M K
Published: October 2002

The paper describes a procedure for modifying finite element predictions of equivalent stress and equivalent total strain in order to obtain equivalent stress and equivalent total strain ranges for lowcycle fatigue life estimates.
Creep and relaxation of heritable orthotropic continua under the plane stress state
Authors: Dumansky A M , Strekalov V B
Published: October 2002

A phenomenological approach for describing the viscoelastic behaviour of orthotropic materials under the plane stress state is suggested. Using the algebra of resolvent operators the analytical expression for a matrix inverse to the matrix of constitutive equations connecting strains and stresses by means of heritable relationships has been obtained. With the help of the inverse matrix including hereditary operators (resolvent of the matrix) the relationships describing the stress state in thin-walled polymeric structures through the history of deformations in the plane stress state have been derived.
Evaluation of the stress intensity factors for a three-dimensional interfacial crack by the boundary element method
Authors: Wen P H , Aliabadi M H
Published: October 2002

In this paper, three-dimensional interface crack problems are analysed by the boundary element method. A special crack tip element is used to improve the accuracy and the complex stress intensity factors are determined by several techniques, namely the one-point stress formula, the one-point discontinuity displacement formula and an energy technique. Stress intensity factors are presented for single-edge, double-edge and centre cracks in bi-materials.
Accelerated life testing and thermomechanical simulation in power electronic device development
Authors: Nicoletto G , Pirondi A , Cova P
Published: October 2002

Product development in the power electronic industry is characterized by the short time-to-market and high-reliability requirements. Improved design methods and advanced modelling techniques are therefore required to support package design selection and to arrive at lifetime prediction algorithms for failure prevention. In this work, experimental and computational activities aimed at supporting the development of a press-pack insulated gate bipolar transistor (IGBT) is reported. A testing rig for accelerated testing of single IGBT chips under controlled contact pressure conditions is presented. Then, thermomechanical simulations of accelerated tests by the finite element method provided stress-strain evolution in the device and insight into the sources of local degradation.
Identification and measurement of ductile damage parameters
Authors: Bonora N
Published: October 2002

The possibility of extending fracture mechanics concepts and design criteria to ductile failure is an issue that has attracted the attention of many researchers. Many models that address this are available nowadays. For these, two kinds of approach are widely used: the porosity-based model proposed by Gurson and the continuum damage mechanics (CDM) approach. Any new user that has to deal with these models for the first time is often hindered by the difficulty of finding in the literature, or measuring, the material parameters necessary. In addition, the use of these models, which are often available already built into commercial finite element codes, requires great experience and attention in order to avoid the danger of ‘numerical traps and tricks’. Here, constitutive models based on the plasticity criterion for porous media given by Gurson, and the CDM framework proposed by Lemaitre are reviewed, giving attention to identification procedures for the damage parameters.
The RapidTool process: Technical capabilities and applications
Authors: Pham D T , Dimov S S , Lacan F
Published: October 2002

RapidTool is a proprietary process based on selective laser sintering technology and designed for producing tooling more quickly than conventional means. Proper implementation of the process for manufacturing tooling inserts requires a thorough understanding of its capabilities. This paper focuses on factors influencing the accuracy of inserts and proposes an approach for fine tuning of process parameters (scaling coefficients and offsets). The paper discusses the finishing of inserts to achieve optimum utilization of the process capabilities. Two industrial case studies are presented to illustrate the application of RapidTool in injection moulding and gravity die casting.
Flexible forming of sheet metal using a plasma arc
Authors: Li P J , Chen Y W , Male A T , Zhang Y M
Published: October 2002

Conventional precision forming of sheet metal requires the use of mechanical tools. During product development, different tools may be required to form various shapes. If the required shapes can be formed without tools, the potential reduction in product development cost and lead time could be quite significant. To explore the potentials of flexible forming without tools, various researchers have used lasers as a heat source to form sheet metals. Promising results have been obtained. To investigate more economical and potentially safer heat sources, the authors recently established an experimental system to investigate the feasibility of forming sheet metals using a plasma arc as the energy beam and CO2 as the cooling jet. Several samples have been formed using the developed experimental system. Experiments have shown that the forming direction, either towards or away from the plasma arc beam, can be completely controlled to allow the formation of complex shapes.
Overcut in pulsed electrochemical grinding
Authors: Tehrani A Fadaie , Atkinson J
Published: October 2002

The electrochemical grinding (ECG) process offers a number of advantages over conventional grinding, such as low induced stresses, large depths of cut, increased wheel life and the ability to machine delicate workpieces. However, one disadvantage is the difficulty of controlling the dimensional accuracy of the workpiece. In the present work the use of pulsed voltage in ECG is investigated for two workpiece materials, AISI 01 tool and die steel and stainless steel 304. The effect on resulting workpiece dimensional accuracy is assessed in terms of repeatability of overcut.

Under conditions where an overcut of 0.03 mm is expected in conventional ECG, a reduction to zero overcut has been obtained by appropriately pulsing the applied voltage. The ranges of such operating conditions have been quantified for the two materials. Further, it is seen that, under finishing conditions appropriate to obtaining mechanical abrasive contribution at the final workpiece surface, a repeatability within 0.010 mm is possible. Repeatability deteriorates to 0.018 mm when electrochemical dissolution is the dominant contributor to metal removal. Pulsed ECG is found to be a convenient means of adjusting operating conditions to control overcut and its repeatability.
Real-time image processing of keyhole puddle in variable polarity plasma arc welding
Authors: Wang H , Kovacevic R , Zheng B , Wang Q
Published: October 2002

In a previous study, a simple and practical image-sensing system comprising a narrow band filter and neutral filters was developed to acquire front-side keyhole puddle images in variable polarity plasma arc welding (VPPAW) of aluminium alloys. However, during actual welding, oxides existing on the puddle surface and variations in image quality with respect to keyhole puddle size complicate the processing of images. In this paper, an image-processing method based on an α-cutting-average-median filter, minimum filter, direction enhancement operators and local statistical characteristics enhancement is developed to tackle the various shapes and appearances of the keyhole puddle. Also, an effective edge-tracing method is developed to detect the edge of the visible keyhole. The geometric sizes of the visible keyhole, such as area, width and height, are acquired with sufficient accuracy, which can be used to calculate the keyhole diameter during the welding process. Experiments show that satisfying results can always be obtained with the developed image-processing method regardless of the original image quality. Processing one image frame takes less than 220ms.
Automatic recognition of machining features from computer aided design part models
Authors: Wong T N , Lam S M
Published: October 2002

This paper presents an innovative method for recognizing manufacturing features from computer aided design (CAD) part models. The proposed method is to integrate the graph-based approach and the volume approach, in order to combine the positive aspects of both strategies. Feature edge sequence, a new graph-based feature recognition approach, is used to recognize and extract surface features from the part design data. The extracted features are then clustered into the machining volumes by the volume-based approach. The main drawback of conventional feature recognition systems is their limitations in handling feature interactions and arbitrary shape features. In the proposed system, the graph-based method is able to recognize interacting features, the volume-based approach can generate alternative interpretations of machining volumes and an artificial intelligence (AI)-based algorithm, established with a neural network, is used to handle the arbitrary features.
In-process automatic dressing system for grinding wheels
Authors: Maksoud T M A , Wong L M J
Published: October 2002

The condition of a grinding wheel surface has a major effect on the surface quality and integrity of the finished component. The condition of the grinding wheel is constantly changing during the process of grinding. Self-dressing is one feature of this process, and blunting and wearing of the cutting grits are other undesirable outcomes. The wear of grits and falling out of sharp cutting edges have serious effects on the ground component integrity and surface finish. This can happen to all types of grinding wheels. This paper presents a novel automated system for dressing of all types of grinding wheels. This system can detect in process the condition of the wheel surface, order a dresser to move to the grinding wheel and dress it to the desired condition under the control of the system and then retract to its original position. This is done without any operator interference. Hence, the system can be readily used with CNC grinders. The system was designed to provide a highly accurate and controllable dressing condition.
The mechanism of material removal in ultrasonic drilling of engineering ceramics
Authors: Zhang Q H , Wu C L , Sun J L , Jia Z X
Published: October 2002

A new method for drilling holes in engineering ceramics by using a rotary ultrasonic tool has been developed. In this method, a drilling tool impregnated with abrasive particles is simultaneously rotated and vibrated. The mechanism of ultrasonic drilling is analysed using the concept of fracture mechanics and a new theoretical model of material removal rate (MRR) is proposed. According to this model, the material removal rate increases with increases of applied static load, amplitude of vibration and rotation speed of the drilling tool. Test results show that ultrasonic drilling is an effective method for machining engineering ceramics.
A discrete model method for three-dimensional parting line search
Authors: Li Z Z , Nee A Y C , Li X P
Published: October 2002

This paper presents a new approach for three-dimensional parting line search of injection moulded parts. In previous work, automatic parting line search is usually based on surface edge-loops. However, it is possible that edge-loops may not be present in a particular parting location. In the present research, all the surfaces in an initial solid model are divided into union parting surfaces and multiple parting surfaces. The multiple parting surfaces are decomposed into several union parting surfaces using the discrete model method before parting line search, creating the new edges as potential parting lines. Parting line search is completed based on the pure union parting surface model. Case studies show that the present research has solved some of the common problems faced in the previous work.
Using stereolithography tools for injection moulding: Research into tensile tool failure and unexpected benefits of the process
Authors: Hopkinson N , Dickens P M
Published: October 2002

The use of stereolithography (SL) parts as injection moulding tools offers many advantages over traditional tool making approaches. In particular, the time required to convert a computer aided design (CAD) file to the final tool is dramatically reduced as may be the costs in creating the tool. However, the process has been perceived to have a number of drawbacks which are, in the main, associated with the poor thermal and mechanical properties of the SL resins.

Research was performed which involved the production and use of an SL tool to injection mould a series of parts in polypropylene. Measurements were made of the forces required to eject parts from the tool in order to assess the possibility of tensile tool failure during part ejection. The measured forces were compared with predicted values which had been calculated using previously devised equations. In addition, temperatures were recorded throughout the injection moulding cycle to assess the tool's strength at different times. Surface roughness measurements were also taken to characterize the ejection process more closely and observe any changes to surface roughness caused by moulding parts. A finite element analysis was made of the heat transfer in the tool to help with prediction of ejection forces.

Measurements of ejection forces and heat transfer indicated that, contrary to existing recommendations, part ejection should be performed shortly after injection. Accurate predictions of ejection force were shown to be unattainable given the difficulty in finding accurate values for the variables used in the force prediction equations. Measurements of heat transfer coupled with surface roughness suggested that the low thermal properties of SL tools actually work in favour of the process rather than against it. This conceptual about-turn regarding the role of thermal properties in SL injection moulding tools indicates that further benefits may be derived from the new technology.
Optimal stock removal in LOM-RP
Authors: Karunakaran K P , Dibbi S , Shanmuganathan Vivekananda P , Raju D S , Kakaraparti Srinivasarao
Published: October 2002

At the completion of building an object in laminated object manufacturing rapid prototyping (LOM-RP), a block with the required object inside is obtained. The remaining stock inside and surrounding the object is in the form of tiny tiles. The operator ‘decubes’ these tiles using sharp tools and extracts the object. After cutting the object contours in each laminate during the building process, the remaining sheet is cut into square grids that grow into these tiles. This grid cutting method, though very simple and innovative, is very inefficient due to poor cutting efficiency and a long decubing time. In this paper, a novel method is presented for extracting the object that is analogous with the extraction of a casting from its permanent mould. This method has a very high cutting efficiency and simplifies and speeds up decubing. The concepts of convex hull and visibility are utilized in the algorithm.
Intelligent control for holonic manufacturing systems
Authors: Balasubramanian S , Zhang X , Norrie D H
Published: October 2002

To enable holonic manufacturing systems (HMS) to have their desired characteristics of adaptability and reconfigurability, their control systems need to be dynamically reconfigurable. An holonic control system implementing metamorphic mechanisms which facilitate such reconfiguration has therefore been developed conceptually and is presented in this paper. An integrated and generic event-driven control architecture is described for the various functional levels of this distributed holonic control system. The architecture utilizes the emerging IEC 1499 function block standard to specify the requisite behaviour of the distributed-control software components. The core low-level control mechanisms have been implemented within an agent-based distributed real-time operating system and a prototype holonic control system using the new architecture has been developed and tested.
The implementation of a control system for a product introduction process
Authors: Backhouse C J , Burns N D , Brookes N J
Published: October 2002

This paper describes the approach taken in implementing a system to control the new product introduction process in an ‘engineering to order’ scenario. The primary objective was to ensure that the new system was immediately viable and able to control all aspects of new product introduction, including long-term learning. The approach taken consisted of integrating a series of techniques established by the authors with concepts previously developed in the literature. The consequence of the implementation was a significant improvement in new product introduction performance as measured against company strategic targets in terms of both short- and longer-term priorities.
A direct analytical solution to the tool design problem in electrochemical machining under steady state conditions
Authors: Alder G M , Clifton D , Mill F
Published: October 2002

A method for the direct computation of two-dimensional electrochemical machining tool designs is described. The required workpiece geometry is represented by a Fourier series. Conformal transformation is then used to express the tool shape in series form, each term being a direct analytical function of the corresponding workpiece harmonic. Tool designs are thus achieved without numerical iteration. The model has been experimentally validated for a required workpiece geometry consisting of two harmonics, for which a tool was designed and manufactured. An In 718–15 per cent NaC1 workpiece-electrolyte system was used to produce a machined surface, whose Fourier transform was obtained. The measured and predicted harmonic amplitudes agree closely. This harmonic design method is also shown to give insight into the relationship and limitations between tool design and achievable workpiece detail.
A three-dimensional algorithm using two-dimensional slice data for building multiple parts in layered manufacturing
Authors: Hur J , Lee K , Ahn J , Lee H C
Published: October 2002

In a rapid prototyping process, the time required to build multiple prototype parts can be reduced by building several parts simultaneously in a work volume. Interactive arrangement of the multiple parts, called three-dimensional nesting, is a tedious process and does not guarantee the optimal placement of all the parts. The three-dimensional nesting is well known as a problem requiring intense computation. Thus, an efficient algorithm to solve this problem is still under investigation. This paper presumes that the three-dimensional packing problem can be simplified into a set of two-dimensional irregular polygon nesting problems for each layer to take advantage of the characteristic of a rapid prototyping process, i. e. the process eventually uses two-dimensional slicing data of the STL file. The proposed algorithm uses a no-fit polygon (NFP) to calculate the allowable locations of each slice of a part such that it does not overlap other existing slices in the same z level. Then the allowable position of the part with respect to other parts already located in a work volume can be determined by obtaining the union of all NFPs that are obtained from each slice of the part. Additionally, a genetic algorithm is used to try and determine the various orders of the placement of the part and the various orientations of each part for efficient packing. Various orientations of a part are examined by rotating it about the normal vector of the slice in finite angles and by inversion. The proposed algorithm can be applied to a rapid prototyping process that does not use support structures.
An analysis of self-assessment practices using the business excellence model
Authors: Ritchie L , Dale B G
Published: October 2002

The paper reports the findings of an examination of self-assessment practices against the criteria of the business excellence model in ten different organizations. Among the main findings are that organizations attempt a number of approaches while gaining experience of self-assessment and therefore the movement from one approach to another needs to be planned and improved guidance provided, that management give insufficient consideration to the resources required for each method of self-assessment and that there was a lack of consistency in the coordination of the self-assessment process. It is also pointed out that, among the organizations studied, there has been a lack of emphasis on the total quality management (TQM) philosophy and its principles in the self-assessment process. It appears that the concept has been rebadged as business excellence to move away from existing pre-concepts of TQM.
Advances in probabilistic design: Manufacturing knowledge and applications
Authors: Swift K G , Raines M , Booker J D
Published: October 2002

Product lifetime prediction, cost and weight optimization have enormous implications for the business of engineering manufacture. Deterministic design fails to provide the necessary understanding of the nature of manufacture, material properties, in-service loading and their variation. Probabilistic approaches offer much potential in this connection, but have yet to be taken up widely by manufacturing industry. This paper reports on advances in probabilistic design made possible through new progress in manufacturing engineering. Methods for predicting process capability indices for given design geometry, material and processing route, and for estimating material property and loading stress variation, are developed to augment probabilistic design formulations. The techniques are used in conjunction with failure mode and effects analysis (FMEA) to facilitate the setting of reliability targets for design schemes. A case study is included to illustrate the application of the methods and the benefits that can accrue from their usage.
Reframing standards using fuzzy sets for improved quality control
Authors: Harris J , Raines M , Booker J D
Published: October 2002

British Standard BS 6208:1990 treats the ultrasonic inspection of steel castings and the consequent assignment of quality levels. This standard is considered as a case study for reframing such specifications in terms of fuzzy sets. The advantage of using fuzzy sets is the elimination of sharp boundaries between quality levels and between cross-section zones with their attendant borderline cases, thus producing smooth natural changes with improved quality control. The standard does not specify a method for estimating a consolidated quality level rating from the individual quality levels obtained from the several criteria in the standard. Such a method, a consequence of the fuzzy sets treatment, is proposed here.
Design and analysis of hollow section extrusion of the underframe part of a railroad vehicle using mismatching refinement with domain decomposition
Authors: Park K , Lee Y K , Yang D Y , Lee D H
Published: October 2002

In order to reduce the weight of a high-speed railroad vehicle, the main body has been manufactured by hollow section extrusion using aluminium alloys. A porthole die has been utilized for the hollow section extrusion process, which involves complicated die geometry and flow characteristics. The design of the porthole die is very difficult because of this complexity. Three-dimensional finite element analysis for a complicated hollow section is also an arduous task from the viewpoint of appropriate mesh construction and computational time. In the present work, mismatching refinement, an efficient domain decomposition method with a different mesh density for each subdomain, is implemented for the analysis of the hollow section extrusion process. In addition, a modified grid-based approach with the surface element layer is utilized for three-dimensional mesh generation of a complicated shape with hexahedral elements. The effects of porthole design are discussed through simulation of the extrusion of an underframe part of a railroad vehicle. An experiment has also been carried out for comparison. Comparing the velocity distribution at the outlet with the thickness variation of the extruded part, it is concluded that the analysed results can provide reliable measures for deciding on whether the die design is acceptable to obtain uniform wall thickness. The analysis results are then successfully extended to industrial porthole die design.
Extraction of roughness properties from captured images of surfaces
Authors: Gadelmawla E S , Koura M M , Maksoud T M A , Elewa I M , Soliman H H
Published: October 2002

Surfaces of industrial parts need to be specified on the basis of their use and application environment. Hence, surface characterization is vital for design, manufacturing and inspection. Furthermore, the development of new industries has led to a requirement for super-smooth surfaces and for the ability to measure such surfaces accurately; therefore, the measurement of engineering surface roughness is becoming increasingly important. Many methods of measuring surface finish have been developed ranging from the simple touch comparator to sophisticated optical techniques (light scattering). The latest technology for measuring surface roughness is the computer vision systems. Unlike the stylus instruments, the optical techniques and computer vision systems have the advantages of being non-contact and are capable of measuring an area from the surface rather than a single line. This paper introduces a new technique to capture an image for a surface and then to extract the roughness heights from the captured image. A set-up consists of a charge-coupled device (CCD) video colour camera, a frame grabber, IBM-compatible PC and a microscope used to capture the images. The images were stored using the bitmap image file format (BMP). A program was written in Visual C++ to convert the captured colour images into grey scale images and then to extract the grey level for each pixel and to store it into a two-dimensional array sized to the image width and the image length. The program is capable of reading six different image file formats: these are BMP, TIFF, GIF, PCX, JPG and WMF. The grey levels range between 0 and 255. The grey level 0 represents the black colour, which represents the minimum height in the image, and the grey level 255 represents the white colour, which represents the maximum height in the image. The grey levels between 0 and 255 represent different heights according to their grey level values. After extraction of the grey levels from the image, a three-dimensional view is displayed to view the topography of the surface. The three-dimensional view can be displayed, virtually, from any point of view using the same basics as those of three-dimensional computer aided design (CAD) systems. From the three-dimensional surface topography it is easy to assess any scratches or cracks in the surface. The developed software works independently and does not need any other software. The package includes the unique feature of calculating a multitude of surface roughness parameters (59 in all) that have not been included in any other package hitherto.
A protocol for communication in a component-based modelling infrastructure
Authors: Hicks B J , Culley S J
Published: October 2002

The concept-to-embodiment phase of the design process is one of the most important aspects of any machine system design activity. In this phase the designer must populate/embody a design concept with actual components and other machine elements. Populating a design concept entails the sizing, specification and matching of engineering components in order to fulfil the performance requirements of the design specification. This is a time-consuming and complex task when undertaken manually. New technologies for component specification, such as electronic catalogues and computational models, enable the designer to consider many more individual components in combination within a shorter space of time. However, to enable more effective and optimal design with these tools, it is desirable for the assembly of components and their associated representations to be considered as a whole during this process, rather than as separate software entities, as is the current practice. This paper describes the communication protocol for a modelling infrastructure that enables systems of components to be considered in an integrated and flexible manner during the embodiment phase of the design process. This is achieved by the generation of a convention for the exchange of component data within a system model. This convention enables the propagation of sufficient component interaction data to allow the concurrent execution of component selection procedures. For a mechanical systems model these procedures may incorporate a range of component representations from a variety of sources, such as electronic catalogues, parametric models or computational design algorithms. This approach enables individual components to be fully specified and the performance capabilities of the system to be assessed as well as ensuring that embodied solutions are achievable configurations.
The characteristics of a high-power diode laser fired enamel coating on a carbon steel
Authors: Lawrence J , Li L
Published: October 2002

Significant changes to the wettability characteristics of a common engineering carbon steel (EN8) were effected after high power diode laser (HPDL) surface treatment. These modifications have been investigated in terms of the changes in the surface roughness of the steel, the presence of any surface melting, the polar component of the steel surface energy and the relative surface O2 content of the steel. The morphological and wetting characteristics of the mild steel and the enamel were determined using optical microscopy, scanning electron microscopy, X-ray photoemission spectroscopy, energy-dispersive X-ray analysis and wetting experiments by the sessile drop technique. This work has shown that HPDL radiation can be used to alter the wetting characteristics of carbon steel so as to facilitate improved enamelling. Furthermore, standard mechanical, physical and chemical testing of the HPDL-fired enamel glaze revealed the glaze to possess similar properties to those of a conventionally fired enamel glaze in terms of bond strength, rupture/impact strength, wear and corrosion resistance. Such similar performance can be attributed to the two glazes possessing the same mechanical properties and similar amorphous structure, despite their very different firing techniques.
Life cycle management and assessment: Approaches and visions towards sustainable manufacturing
Authors: Westkämper E , Alting L , Arndt G
Published: October 2002

Thinking in terms of product life cycles is one of the challenges facing manufacturers today: Efforts to increase efficiency throughout the life cycle do not only mean extended responsibility of the parties concerned. Economically successful business areas can also be explored. Whether new service concepts are required, new regulations have been passed or consumer values are changing, the differences between business areas are disappearing. Life cycle management (LCM) considers the product life cycle as a whole and optimizes the interaction of product design, manufacturing and life cycle activities. The goal of this approach is to protect resources and maximize effectiveness by means of life cycle assessment, product data management, technical support and, last but not least, life cycle costing. This paper shows the existing approaches of LCM and discusses their prospects and further development.
Computer-based product structure analysis for technical goods regarding optimal end-of-life strategies
Authors: Feldmann K , Trautner S , Lohrmann H , Melzer K
Published: October 2002

The environmental consciousness of customers as well as legislative regulations force producers to consider the product end of life within the product design. Consequently, additional design aspects are leading to the need for specific support tools, which enable design for disassembly and recycling. The approach presented shows a computer-based methodology for a product structure analysis regarding the determination of economically optimal end-of-life strategies for technical goods. Based on a product model, a model of end-of-life processes and a simulation of disassembly, the economically optimal end-of-life strategy of a complex product is calculated. Owing to the huge number of disassembly options of complex products, some methodical approaches for the reduction of computation efforts have been developed. Further approaches for the detection of improvement potentials regarding the product end-of-life behaviour consider the product structure, the joining technique and the material compatibility. The different aspects are analysed and compared with the modelled end-of-life processes using special characteristic values. The methodologies developed have been implemented in a software tool that contains the respective input interface, performs the computations and displays models and results mainly in a graphical manner.
Disassembly planning and scheduling: Review and further research
Authors: Lee D-H , Kang J-G , Xirouchakis P
Published: October 2002

This paper focuses on the planning and scheduling problems in disassembly systems, in which used or end-of-life products are disassembled into basic parts and subassemblies for both economic and environmental reasons. The disassembly planning includes product representation, disassembly sequencing with disassembly level and end-of-life options, and related product design/redesign issues, while the disassembly scheduling is the problem of determining the order quantity of the used product to fulfil the demand of disassembled parts and subassemblies. This paper presents a review of the state-of-the-art articles and suggests the corresponding further research directions. The research directions suggested in this paper can be summarized as