Fast transient simulation of IEEE recommended surge arrester model on a transmission line using alternative transient program (ATP)

This study presents the outcomes of the performance evaluation simulation residual voltage output resulting from lightning arrestors IEEE Recommended model. This simulation uses software Alternative Transient Program - Electromagnetic transients Programmed (ATP-EMTP). This software is very appropriate in examining the behavior of the system, especially a high voltage system lines. As a result of the comparison can be made in the system of 132kV transmission line between systems that are not supplied with lightning arrestors, system supplied with lightning arrestors with conventional styles and systems supplied with lightning arrestors IEEE Recommended model. The results of the simulation study comparisons can be made by taking into account the peak voltage at sub transient conditions. This situation can determine the 132kV transmission line system can protect the equipment properly. Selection lightning 10kA with the 8μs fast front surge and trailing the current time is 20μs is appropriate in the circumstances lightning eruption in Malaysia. In this research, 132kV transmission line parameter tower need to be enclosed by the actual value of the output to the accurate or almost accurate in determining the ability of a lightning arrester in the system

Modelling Temperature and Strain-Rate Dependence of Recycled Aluminium Alloy AA6061

Recycling aluminium is a topic of high interest for numerous researchers to cope with the high demand for usage of its primary sources, and to overcome the environmental issues at the same time. Many recycling approaches, including the optimization of the recycling processes have been explored. However, the behaviour of such recycled material under various strain rates and the temperatures is yet established. This is important before an appropriate application can be identified in real practice. Therefore, the works in this manuscript are conducted to characterize the deformation behaviour of recycled aluminium alloy under the uniaxial tensile test using experimental and numerical approaches. The deformation behaviour of the recycled aluminium alloy produced using hot press forging recycling technique is tested over a range of strain rate (×10-4 â€“ ×10-3 s-1) and elevated temperature (100°C – 300°C), where a mild ductile and elastoplastic behaviour are observed, and further compared with the primary form of AA6061. In addition, finite element (FE) model capable of predicting the non-linear behaviour of such materials using the flow stress model of MAT_098: Simplified Johnson-Cook model of LS-DYNA FE code is developed. The characterisation of this constitutive model is also discussed thoroughly in this paper. The numerical results are validated against the experimental data. A good agreement between the experimental and numerical results are obtained. The outcome of numerical analysis is important to prove a strength model is still relevant to predict the deformation behaviour of such recycle material. Further, it showed that further manufacturing advancement is required on the experimental part since an anisotropic parameters are still unavailable, yet vital for consideration

Modelling Temperature and Strain-Rate Dependence of Recycled Aluminium Alloy AA6061

Recycling aluminium is a topic of high interest for numerous researchers to cope with the high demand for usage of its primary sources, and to overcome the environmental issues at the same time. Many recycling approaches, including the optimization of the recycling processes have been explored. However, the behaviour of such recycled material under various strain rates and the temperatures is yet established. This is important before an appropriate application can be identified in real practice. Therefore, the works in this manuscript are conducted to characterize the deformation behaviour of recycled aluminium alloy under the uniaxial tensile test using experimental and numerical approaches. The deformation behaviour of the recycled aluminium alloy produced using hot press forging recycling technique is tested over a range of strain rate (×10-4 â€“ ×10-3 s-1) and elevated temperature (100°C – 300°C), where a mild ductile and elastoplastic behaviour are observed, and further compared with the primary form of AA6061. In addition, finite element (FE) model capable of predicting the non-linear behaviour of such materials using the flow stress model of MAT_098: Simplified Johnson-Cook model of LS-DYNA FE code is developed. The characterisation of this constitutive model is also discussed thoroughly in this paper. The numerical results are validated against the experimental data. A good agreement between the experimental and numerical results are obtained. The outcome of numerical analysis is important to prove a strength model is still relevant to predict the deformation behaviour of such recycle material. Further, it showed that further manufacturing advancement is required on the experimental part since an anisotropic parameters are still unavailable, yet vital for consideration

Correlation Between Cutting Force and Residual Stress in Dry End-Milling of Inconel HX

Residual stress in the end-milled subsurface can significantly affect the fatigue performance of end-milled material. In the end-milling process, the generation of residual stress is extremely complex, which is closely related to the spindle speed, feed per tooth and cutting force. Thus, it is crucial to elucidate the influence of spindle speed and feed per tooth on cutting force and residual stress, also the correlation between cutting force and residual stress in terms of spindle speed and feed per tooth. According to this, dry end-milling of Inconel HX was performed by climb-milling using Kennametal KYS40 solid ceramic end-mill. From this experimental test, cutting force and residual stress showed a U-shaped relationship with the increase of spindle speed, while cutting force and residual stress showed a linear relationship with the increase of feed per tooth. Furthermore, for low cutting force and residual stress, the focus should be on choosing the optimum combination of spindle speed (21,400 to 24,100 rpm) and feed per tooth (0.014 to 0.016 mm/tooth)

Correlation Between Cutting Force and Residual Stress in Dry End-Milling of Inconel HX

Residual stress in the end-milled subsurface can significantly affect the fatigue performance of end-milled material. In the end-milling process, the generation of residual stress is extremely complex, which is closely related to the spindle speed, feed per tooth and cutting force. Thus, it is crucial to elucidate the influence of spindle speed and feed per tooth on cutting force and residual stress, also the correlation between cutting force and residual stress in terms of spindle speed and feed per tooth. According to this, dry end-milling of Inconel HX was performed by climb-milling using Kennametal KYS40 solid ceramic end-mill. From this experimental test, cutting force and residual stress showed a U-shaped relationship with the increase of spindle speed, while cutting force and residual stress showed a linear relationship with the increase of feed per tooth. Furthermore, for low cutting force and residual stress, the focus should be on choosing the optimum combination of spindle speed (21,400 to 24,100 rpm) and feed per tooth (0.014 to 0.016 mm/tooth)

Analyzing the effect of nozzle diameter in fused deposition modeling for extruding polylactic acid using open source 3D printing

Fused deposition modeling (FDM) is one of the Rapid Prototyping (RP) technologies. The 3D Printer has been widely used in the fabrication of 3D products. One of the main issues has been to obtain a high quality for the finished parts. The present study focuses on the effect of nozzle diameter in terms of pressure drop, geometrical error as well as extrusion time. While using polylactic acid (PLA) as a material, the research was conducted using Finite Element Analysis (FEA) by manipulating the nozzle diameter, and the pressure drop along the liquefier was observed. The geometrical error and printing time were also calculated by using different nozzle diameters. Analysis shows that the diameter of the nozzle significantly affects the pressure drop along the liquefier which influences the consistency of the road width thus affecting the quality of the product’s finish. The vital aspect is minimizing the pressure drop to be as low as possible, which will lead to a good quality final product. The results from the analysis demonstrate that a 0.2 mm nozzle diameter contributes the highest pressure drop, which is not within the optimum range. In this study, by considering several factors including pressure drop, geometrical error and printing time, a 0.3 mm nozzle diameter has been suggested as being in the optimum range for extruding PLA material using open-source 3D printing. The implication of this result is valuable for a better understanding of the melt flow behavior of the PLA material and for choosing the optimum nozzle diameter for 3D printing

Early resumption of sexual intercourse and its determinants among postpartum Iban mothers

Introduction: Recurrent pregnancy with close child spacing can result from early resumption of sexual intercourse during the postpartum period. This would expose mothers to complications such as unsafe abortion, postpartum depression and premature birth. The aim of this study is to identify the factors associated with early resumption of sexual intercourse among postpartum Iban mothers.Methods: This is a cross sectional study conducted in Sri Aman Division, Sarawak between 1st July and 31st August 2006. A total of 265 Iban mothers agreed to participate in this study. They were interviewed face-to-face using structured questionnaire. Any postpartum sexual intercourse at 6 weeks or less is considered an early resumption of sexual intercourse.Results: Univariable analyses showed significant association between early sexual intercourse and use of contraceptive; mothers’ and husbands’ income; mothers who believed their husbands were sexually abstinent during their confinement period; mothers who stayed with their spouse after delivery; and those with high libido. Multivariable analysis showed only mothers’ and husbands’ income, use of contraceptive and those who believed their husbands practiced sexual abstinence during their confinement period were significantly associated with early resumption of sexual intercourse. Conclusions: Counselling on postpartum resumption of sexual intercourse among Iban mothers should focus on these determinants to ensure a more effective counselling outcome among Iban mothers

Modeling dynamic anisotropic behaviour and spall failure in commercial aluminium alloys AA7010

This paper presents a finite strain constitutive model to predict a complex elastoplastic deformation behaviour involves very high pressures and shockwaves in orthotropic materials of aluminium alloys. The previous published constitutive model is used as a reference to start the development in this work. The proposed formulation that used a new definition Mandel of stress tensor to define Hill’s yield criterion and a new shock equation of state (EOS) of generalised orthotropic pressure is further enhanced with Grady spall failure model to closely predict shockwave propagation and spall failure in chosen commercial materials. This hyperelastic-plastic constitutive model is implemented as 1᨞᨟ᨠᨡ 1 1 1 a new material model in the Lawrence Livermore National Laboratory (LLNL)-DYNA3D code of UTHM’s version, named Material Type 92 (Mat92). The implementation of a new EOS that is modified to match the generalised orthotropic pressure including the spall failure is also discussed in this paper. The capability of the proposed constitutive model to capture the complex behaviour of the selected material is validated against range of Plate Impact Test data at 234, 450 and 895 ms impact velocities

New learning spaces and transformations in teacher pedagogy and student learning behavior in the language learning classroom

Many Malaysian classrooms have been redesigned to include technology and foster the development of twenty first century learning. The availability of this platform and the new learning space created by redesigning the language classroom has opened up new and exciting possibilities for teaching and learning the English language. This paper will investigate if the new learning space has impacted teacher’s pedagogical strategies and student’s learning behavior and engagement for English language teaching and learning. A qualitative approach employing a multiple case study research design was taken and data was collected using classroom observations, teacher interviews and teacher and student focus group discussions from eight English language teachers and 37 students. Findings reveal significant transformations in teachers’ teaching approaches, use of class activities and on students’ learning behavior and outcomes. Technology did feature in the learner centric approach with students functioning as facilitators and allowing more student participation and interaction. The use of multimedia and online materials helped make learning more interesting and improved student attention in class. Students in turn were more focused and engaged in the collaborative tasks and also reported developing better peer relationships and learning from each other