Search results

The purpose of this paper is to optimise the electro‐discharge machining (EDM) parameters and investigate feasibility of using direct metal laser sintering (DMLS) parts as EDM electrodes.

In this paper the effects of discharge current, pulse‐on‐time, flushing pressure are optimized for minimum tool wear rate (TWR), maximum metal removal rate (MRR) and minimum surface roughness (Ra). Taguchi‐based L₉ orthogonal array has been used for performing experiments on EDM machining of EN 24 steel using DMLS electrodes. The grey relational analysis combined with ANOVA techniques have been employed to determine the optimal level as well as their significance.

Experimental results have shown that the performance characteristics of the EDM process (TWR, MRR and surface roughness) using DMLS electrode can be quantified and controlled effectively by grey relational approach presented in the study. Current is found to be the most affective parameter in EDM machining using DMLS electrode. Excessive DMLS tool (electrode) wear was also reported, which limits the use of DMLS tool for EDM machining and it has been found out that porosity (which was about 20 per cent) was one of the primary cause.

This paper was focused on understanding the effects of important EDM parameters on three performance characteristics (TWR, MRR and surface roughness). While this study identifies that DMLS electrode wear rate is high and porosity could be one of the main cause, presently it does not cover the investigations on reducing the porosity level and its implications.

The DMLS material had shown huge potential to be used as EDM electrode. The current investigation established a structured experimental approach to understand the effects of EDM parameters on multi response characteristics. The results derived from this study helps to focus future research on two aspects including enriching the copper content and reducing the porosity level, thereby the benefits of lead time reduction in EDM electrode making could be realized.

The previous research attempts were not focussed on optimising the EDM machining process using rapid tooling electrodes. With the best of author's knowledge none of the researchers have reported these aspects especially for DMLS electrodes. Application of grey relational analysis for performance evaluation of rapid tooling‐based EDM electrodes (DMLS electrodes) appear to be completely new.

The purpose of this study is to examine the influence of ethical ideological orientation (moral idealism and moral relativism), work sector and types of professional membership on the ethical decision-making (EDM) process of professional accountants in Nigeria.

The study obtained primary data from 329 professional accountants with the aid of a structured questionnaire containing four scenarios of ethical dilemmas. The data were analysed using descriptive statistical analysis, independent sample t-test, Pearson correlation analysis and multiple regression techniques.

The results revealed both idealistic and relativistic moral orientation among the accountants surveyed with a higher mean score (>4.0) recorded for moral idealism. Moral idealism was found to have a positive influence, while moral relativism a negative influence on the three stages (ethical recognition, ethical judgement and ethical intention) of EDM examined. Professional accountants with idealistic orientation showed a higher disposition towards making ethical decisions in situations involving ethical dilemmas than those tending towards relativistic orientation. The results also revealed that work sector (private or public) and types of professional membership play significant roles in predicting the EDM process of professional accountants in Nigeria.

The study provides empirical evidence that could be used to support educational and legislative efforts in enhancing the moral ideological orientation of professional accountants, which will, in turn, enhance their EDM processes. The findings could be used to enhance ethics instructions and training of current and prospective professional accountants in educational settings, especially in countries such as Nigeria where there is yet to be a discrete ethics course in the curriculum for accounting undergraduate degree programmes. Professional accounting bodies in Nigeria and other developing countries could use the evidence in this study to strengthen the ethics code for professional accountants.

The study is unique in focussing on professional accountants in developing countries using Nigeria to represent developing countries with high corruption profile and weak institutions and governments and, as such, it contributes to the scarce research output on accounting ethics in developing countries.

Educational data mining (EDM) and learning analytics, which are highly related subjects but have different definitions and focuses, have enabled instructors to obtain a holistic view of student progress and trigger corresponding decision-making. Furthermore, the automation part of EDM is closer to the concept of artificial intelligence. Due to the wide applications of artificial intelligence in assorted fields, the authors are curious about the state-of-art of related applications in Education.

This study focused on systematically reviewing 1,219 EDM studies that were searched from five digital databases based on a strict search procedure. Although 33 reviews were attempted to synthesize research literature, several research gaps were identified. A comprehensive and systematic review report is needed to show us: what research trends can be revealed and what major research topics and open issues are existed in EDM research.

Results show that the EDM research has moved toward the early majority stage; EDM publications are mainly contributed by “actual analysis” category; machine learning or even deep learning algorithms have been widely adopted, but collecting actual larger data sets for EDM research is rare, especially in K-12. Four major research topics, including prediction of performance, decision support for teachers and learners, detection of behaviors and learner modeling and comparison or optimization of algorithms, have been identified. Some open issues and future research directions in EDM field are also put forward.

Limitations for this search method include the likelihood of missing EDM research that was not captured through these portals.

This systematic review has not only reported the research trends of EDM but also discussed open issues to direct future research. Finally, it is concluded that the state-of-art of EDM research is far from the ideal of artificial intelligence and the automatic support part for teaching and learning in EDM may need improvement in the future work.

AA2014 is a copper-based alloy and is typically used for production of complex machined components, given its better machinability. The purpose of this paper was to study the effects of variation in weight percentage of ceramic Al₂O₃ particulates during electrical discharge machining (EDM) of stir cast AA2014 composites. Scanning electron microscopy (SEM) examination was carried out to study characteristics of EDMed surface of Al₂O₃/AA2014 composites.

The effect of machining parameters on performance measures during sinker EDM of stir cast Al₂O₃/AA2014 composites was examined by “one factor at a time” (OFAT) method. The stir cast samples were obtained by using three levels of weight percentage of Al₂O₃ particulates, i.e. 0 Wt.%, 10 Wt.% and 20 Wt.% with density 1.87 g/cc, 2.35 g/cc and 2.98 g/cc respectively. Machining parameters varied were peak current (1-30 amp), discharge voltage (30-100 V), pulse on time (15-300 µs) and pulse off time (15-450 µs) to study their influence on material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR).

MRR and SR decreased with an increase in weight percentage of ceramic Al₂O₃ particulates at the expense of TWR. This was attributed to increased microhardness for reinforced stir cast composites. However, microhardness of EDMed samples at fixed values of machining parameters, i.e. 9 amp current, 60 V voltage, 90 µs pulse off time and 90 µs pulse on time reduced by 58.34, 52.25 and 46.85 per cent for stir cast AA2014, 10 Wt.% Al₂O₃/AA2014 and 20 Wt.% Al₂O₃/AA2014, respectively. SEM and quantitative energy dispersive spectroscopy (EDS) analysis revealed ceramic Al₂O₃ particulate thermal spalling in 20 Wt.% Al₂O₃/AA2014 composite. This was because of increased particulate weight percentage leading to steep temperature gradients in between layers of base material and heat affected zone.

This work was an essential step to assess the machinability for material design of Al₂O₃ reinforced aluminium metal matrix composites (AMMCs). Experimental investigation on sinker EDM of high weight fraction of particulates in AA2014, i.e. 10 Wt.% Al₂O₃ and 20 Wt.% Al₂O₃, has not been reported in archival literature. The AMMCs were EDMed at variable peak currents, voltages, pulse on and pulse off times. The effects of process parameters on MRR, TWR and SR were analysed with comparisons made to show the effect of Al₂O₃ particulate contents.

The purpose of this paper is to investigate prediction and optimization of multiple performance characteristics in the wire electrical discharge machining (wire-EDM) process of SKD 61 (AISI H13) tool steel.

The experimental studies were conducted under varying wire-EDM process parameters, which were arc on time, on time, open voltage, off time and servo voltage. The optimized responses were recast layer thickness (RLT), surface roughness (SR) and surface crack density (SCD). Arc on time was set at two different levels, whereas the other four parameters were set at three different levels. Based on Taguchi method, an L18 mixed-orthogonal array was selected for the experiments. Further, three methods, namely grey relational analysis (GRA), backpropagation neural network (BPNN) and genetic algorithm (GA), were applied separately. GRA was performed to obtain a rough estimation of optimum drilling parameters. The influences of drilling parameters on multiple performance characteristics were determined by using percentage contributions. BPNN architecture was determined to predict the multiple performance characteristics. GA method was then applied to determine the optimum wire-EDM parameters.

The minimum RLT, SR and SCD could be obtained by setting arc on time, on time, open voltage, off time and servo voltage at 2 ms, 3 ms, 90 volt, 10 ms and 38 volt, respectively. The experimental confirmation results showed that BPNN-based GA optimization method could accurately predict and significantly improve all of the responses.

There were no publications regarding multi-response optimization using a combination of GRA and BPNN-based GA methods during wire-EDM process available.

This paper and research behind it aim to explain key elements behind construction project data management by looking at actual operations. The construction project management is heavily built around document control and relating events such as change orders, submittals, transmittals and requests for information. These functionalities are usually forming the core of electronic data/document management systems (EDMS), and more recently solutions based on Building Information Modelling (BIM) technologies. A growing share of buildings construction projects are designed and documented by using BIM applications. BIM applications can form spatially organised access to project data and documents which, if widely applied, can change the world of EDMS solutions.

This paper presents results of a research effort where the use of EDMS was studied in 15 building construction case projects. The research focus was on EDMS structure, usage of EDMS in each case project and EDMS use models.

The gained results explain content and characteristics of current practice. It is considered that useful knowledge can be learned from the present used of EDMS in building construction projects. This understanding can help our sector to move towards more advanced solutions.

The obtained research data are a certain kind of building development projects. These were renovation and change projects of existing buildings.

Although the main stream of research has been technology-driven, the research behind this paper is targeting for new knowledge over the characteristics of EDMS use.

This paper aims to investigate two causality concepts, sphere of control (SOC) and agent–action–results (AAR), and their potential applications to construction business ethics. SOC is used in ethics training, and AAR is applied to ethical decision-making (EDM).

A framework of ethics training and a framework of EDM for construction companies have been developed. Interviews were conducted with experienced construction engineers and PhD ethicians to test the validity of the EDM framework.

Literature review has been conducted in ethical issues, ethics training and EDM, leading to the developments of the frameworks. The framework of ethics training incorporates SOC to reflect the ethicality and personality traits. The framework of EDM is based on AAR, combined with a stakeholder approach and Kohlberg’s cognitive moral development theory, with a review from EDM models in business. Both frameworks include project-level component to reflect the unique feature of the construction industry. The framework of EDM showed a good practicality through the interviews on an ethical dilemma example.

For the ethics training framework, a long-term observation or survey should be accompanied to evaluate the framework in detail, tracing the improvement of ethicalness of course participants.

The customized ethics training will be more efficient and effective, as it considers individual ethicality. The scoring system of the EDM framework is simple and practical. This is particularly relevant for construction ethics management, considering that most of construction practitioners are engineers, not philosophers or psychologists.

Applying causality concepts, SOC and AAR, to construction ethics is a novel approach in construction management. This research has made a good advancement in construction ethics management by providing the right directions to be explored in these new areas.

The purpose of this paper is to examine the influence of personal and moral intensity variables on specific processes, namely, ethical recognition, ethical judgment and ethical intention, involved in the ethical decision making (EDM) of accounting professionals.

A structured questionnaire containing four vignettes of ethical dilemmas is used in the paper to obtain data from 329 accounting professionals. The data are analyzed using Pearson correlation matrix, independent sample t-test, one-way analyses of variance and multiple regression estimation techniques.

The findings of the paper suggest that age, economic status, upbringing, moral idealism and relativism, magnitude of consequence and social consensus are significant determinants of the EDM process of accounting professionals.

The paper provides evidence to guide accounting regulatory bodies on ways to strengthen extant measures that ensure strict compliance with ethics codes among accounting professionals in Nigeria.

The paper provides support for Kohlberg’s cognitive reasoning and moral development theory and Rest’s EDM theoretical model, which will aid the development of a structured curriculum for accounting ethics instruction in Nigeria, as hitherto, there is yet to be a provision for a stand-alone ethics course in the undergraduate accounting programs in Nigeria.

This work is focused on the investigation of direct production of electrical discharge machining (EDM) electrodes through the selective laser sintering (SLS) technique using a new metal-matrix composite material made of molybdenum and a copper-nickel alloy (Mo-CuNi). The influence and optimization of the main SLS parameters on the densification behavior and porosity is experimentally studied. Additionally, EDM experiments are performed to evaluate the electrodes performance under different machining conditions. The paper aims to discuss these issues.

The new EDM electrode material used was a powder system composed of Mo and pre-alloyed CuNi. A systematic experimental methodology was designed to evaluate the effects of layer thickness, laser scan speed and hatch distance. The densification behavior, porosity and surface morphology of the samples were analyzed through microstructural and surface analysis. EDM experiments were conducted under three different regimes in order to observe the electrodes behavior and performance. The results were compared with copper powder electrodes manufactured by SLS and solid copper electrodes EDMachined under the same conditions.

The experimental results showed that the direct SLS manufacturing of composite electrodes is feasible and an adequate combination of parameters can produce parts with good quality. The laser scan speed has a great effect on the densification behavior of the samples, while the effect of hatch distance on the porosity is more visible when the overlapping degree is considered. The overlapping also had a significant effect on the surface morphology. The EDM results showed that the Mo-CuNi electrodes had superior performance to the copper powder electrodes made by SLS for all the EDM regimes applied, but inferior to those achieved with solid copper electrodes.

Significant results on the direct SLS manufacturing of a new material which has a great technological potential to be used as an EDM electrode material are presented. Valuable guidelines are given in regard to the SLS optimization of Mo-CuNi material and its performance as an EDM electrode. This work also provides a systematic methodology designed to be applied to the SLS process to produce EDM electrodes.

This work aims to investigate the direct production of electrical discharge machining (EDM) electrodes by means of the selective laser sintering (SLS) technique using a new non-conventional metal-matrix composite material (TiB₂-CuNi). The influence and optimization of the main SLS parameters on the densification behavior and porosity is experimentally studied. EDM experiments are also performed to evaluate the electrodes performance.

The new EDM electrode material used was a powder system composed of TiB₂ and CuNi. Making use of a designed systematic experimental methodology, the effects of layer thickness, laser scan speed and scan line spacing were optimized, where aspects such as densification behavior, porosity and surface morphology of the samples were analyzed through microstructural and surface analysis. EDM experiments were conducted under three different regimes in order to observe the electrodes behavior and performance. The results were compared with copper powder electrodes manufactured by SLS and EDMachined under the same conditions.

The experimental results showed that the direct SLS manufacturing of composite electrodes is feasible and promising. The laser scan speed has a high effect on the densification behavior of the samples, while the effect of scan line spacing on the porosity is more visible when the overlapping degree is considered. Surface morphology was not affected by the scan line spacing, whereas balling phenomenon was reported, regardless of the scan line spacing. The EDM results showed that the TiB₂-CuNi electrodes had a much superior performance than the copper powder electrodes made by SLS, regardless of the EDM regime applied.

Generally, the machine tool itself promotes some restrictions to the SLS process optimization. It is normally attributed to the characteristics of the laser type and the amount of energy that can be delivered to the powder bed. The present investigation could not cover all the optimization potential involved with the studied material due to limitations of the SLS machine tool used.

Significant results on the direct SLS manufacturing of a new non-conventional composite material, which has a great technological potential to be used as an EDM electrode material, are presented. Valuable guidelines are given in regard to the SLS optimization of TiB₂-CuNi material and its performance as an EDM electrode. This work also provides a systematic methodology designed to be applied to the SLS process to produce EDM electrodes.