Factors affecting prior austenite grain size in low alloy steel

The effect of varying normalising and hardening temperatures on the prior austenite grain size in a low alloy Cr–Mo–Ni–V steel has been examined. An initial relative insensitivity of grain size to increasing austenitising temperature was observed followed by a sudden growth of grains at approximately 1000 °C. A detailed study of the precipitates in the steel showed the presence of a bimodal size distribution of vanadium carbides. The grain size increase is attributed to a decrease in volume fraction and an increase in size of V₄C₃ particles with increasing temperature.     

Experimental comparison of dynamic tracking performance of iGPS and laser tracker

External metrology systems are increasingly being integrated with traditional industrial articulated robots, especially in the aerospace industries, to improve their absolute accuracy for precision operations such as drilling, machining and jigless assembly. While currently most of the metrology assisted robotics control systems are limited in their position update rate, such that the robot has to be stopped in order to receive a metrology coordinate update, some recent efforts are addressed toward controlling robots using real-time metrology data. The indoor GPS is one of the metrology systems that may be used to provide real-time 6DOF data to a robot controller. Even if there is a noteworthy literature dealing with the evaluation of iGPS performance, there is, however, a lack of literature on how well the iGPS performs under dynamic conditions. This paper presents an experimental evaluation of the dynamic measurement performance of the iGPS, tracking the trajectories of an industrial robot. The same experiment is also repeated using a laser tracker. Besides the experiment results presented, this paper also proposes a novel method for dynamic repeatability comparisons of tracking instruments.     

Digital enterprise technology in production networks

Enterprises organised as distributed production networks face challenges related to the planning and synchronisation of their manufacturing operations, and of controlling the quality, cost and production time of products under development. Digital enterprise technology (DET) is a framework for new technologies which can shorten product development and realisation, by estimating and therefore controlling quality, cost and delivery factors for products at an early stage in their lifecycle. DET can also be deployed to facilitate planning and synchronisation of work across an extended enterprise. Particularly for high value and high complexity products, these techniques represent an emergent synthesis of strategies for design, manufacture and product lifecycle management.     

Random uncertainty propagation in estimates of sphere parameters from coordinate measurements

Measurements of reference spheres are widely used in verification and calibration of coordinate measuring systems. In this paper, a model for the propagation of random errors in the estimation of sphere parameters is outlined. The dependence of the error propagation on sampling area and sample density is demonstrated using both simulated and measured data. The model can be used to characterise the random error of a coordinate measurement system. It can also be used to determine the error limits on a single sphere parameter estimate or to determine the required sampling strategy to ensure that the confidence limits on an estimate remain within predetermined bounds.     

Fracture toughness evaluation of a H.S.L.A. steel

The fracture toughness, J_Ic of a 3.5 Ni-Cr-Mo-V steel has been measured using the ASTM method. The results have been used to predict the stress intensity factor, K_Ic from the relationship between linear elastic and elastic-plastic fracture parameters. These predicted values were compared with K_Ic values obtained from empirical equations based on valid K_Ic tests, involving the Charpy upper shelf energy. It was found that the ASTM method for measuring J_Ic led to conservative estimates of K_Ic.     

Design verification and validation in product lifecycle

The verification and validation of engineering designs are of primary importance as they directly influence production performance and ultimately define product functionality and customer perception. Research in aspects of verification and validation is widely spread ranging from tools employed during the digital design phase, to methods deployed for prototype verification and validation. This paper reviews the standard definitions of verification and validation in the context of engineering design and progresses to provide a coherent analysis and classification of these activities from preliminary design, to design in the digital domain and the physical verification and validation of products and processes. The scope of the paper includes aspects of system design and demonstrates how complex products are validated in the context of their lifecycle. Industrial requirements are highlighted and research trends and priorities identified.     

EDM electrode manufacture using rapid tooling: a review

Electrical discharge machining (EDM) is a non-conventional process for the manufacture of complex or hard material parts that are difficult to machine by conventional machining processes. During EDM, the electrode shape is mirrored in the workpiece. As a result, problems are transferred on the electrode manufacturing process. Rapid tooling (RT) is a new technology which uses rapid prototyping (RP) models to reduce the time and cost of tool manufacture. The various methods of manufacturing RT electrodes, with respect to different materials and the incorporated supplementary processes, are classified in the present work. Recent international research work on RT electrodes is reviewed and the results on the performance of RT electrodes are tabulated.     

Early design verification of complex assembly variability using a Hybrid – Model Based and Physical Testing – Methodology

Design verification in the digital domain, using model-based principles, is a key research objective to address the industrial requirement for reduced physical testing and prototyping. For complex assemblies, the verification of design and the associated production methods is currently fragmented, prolonged and sub-optimal, as it uses digital and physical verification stages that are deployed in a sequential manner using multiple systems. This paper describes a novel, hybrid design verification methodology that integrates model-based variability analysis with measurement data of assemblies, in order to reduce simulation uncertainty and allow early design verification from the perspective of satisfying key assembly criteria.     

A dynamic feature information model for integrated manufacturing planning and optimization

This paper presents a new, dynamic feature representation method for high value parts consisting of complex and intersecting features. The method first extracts features from the CAD model of a complex part. Then the dynamic status of each feature is established between various operations to be carried out during the whole manufacturing process. Each manufacturing and verification operation can be planned and optimized using the real conditions of a feature, thus enhancing accuracy, traceability and process control. The dynamic feature representation is complementary to the design models used as underlining basis in current CAD/CAM and decision support systems.