Modelling the Effects of Friction on Tool-Chip Interface Temperature During Orthogonal Cutting of Al6061-T6 Aluminium Alloy

© IEOM Society International - IEOM 2019In this work, finite element simulations based on the analytical model derived with the MATLAB software were used to establish the temperature fields within the cutting tool and tool-chip interface. The average tool-chip interface temperature model was simulated and the simulation results were compared with experimental results for validation. At a maximum cutting speed of 90 m/min, the maximum temperature obtained from the experiment was 410 oC, at same rake angle of 0o. However, the developed model predicted 490 oC under the same conditions. The higher value obtained by the model can be attributed to the negligence of heat losses to the surrounding by both convection and radiation modes, as an assumption in the formulated model. A similar trend of these results was also recorded for the case of rake angle and feed rate of 30o and 0.0635 mm/rev, respectively. It was observed that the simulation results and experimental measurements for the average tool-chip interface temperature agreed significantly.Final Published versio

Experimental and numerical prediction of extrusion load at different lubricating conditions of aluminium 6063 alloy in backward cup extrusion

In the present research work using a backward cup extrusion (BCE) die profile, different lubricating conditions on aluminum alloy AA6063 have been experimentally and numerically investigated to predict the extrusion load. It was obvious that due to an increase in applications of the extrusion process, many researchers have worked on the extrusion process using different methods to achieve their aims. This experiment was conducted with three different lubricants namely: Castor oil, Palm Oil and tropical coconut oil; as well as without lubricants. Different lubricating conditions were employed of varying strain rates ranges from 1.5×10-3s-1, 2.0×10-3s-1, 2.5×10-3s-1, and 3.0×10-3s-1; Numerical analysis and simulation for dry and lubricated conditions during extrusion load were also performed using DEFORM 3D software. The results show that prediction extrusion load increases with increasing strain rates. The maximum extrusion load was found to be higher for extrusion without lubricants. In all cases of strain rate, palm oil showed a lower extrusion load compared to the other lubricants. Castor oil indicated the highest extrusion load when the experiment was carried out using lubrication. There was a consistent agreement between the result gotten from the experiment and simulation results of the extrusion load-strike curve.Peer reviewedFinal Published versio

Experimental and numerical investigations of free convection heat transfer in solar oven

The use of solar energy for baking, heating or drying represents a sustainable way of solar energy applications with negligible negative effects. Solar oven is an alternative to conventional oven that rely heavily on coal and wood or Electric oven that uses the power from the National grid of which the end users have little or no control. Since the Solar oven uses no fuel and it cost nothing to run, it use are widely promoted especially in situations where minimum fuel consumption or fire risks are considered highly important. As useful as the Solar Oven proved, it major setback in the area of applications has been its future sustainability. For the use of Solar Oven/Cookers to be sustained in the future, the design and development of solar oven must rely on sound analytical tools. Therefore, this work focused on the design and development of the solar oven. To test the performance of the Small Solar Oven a 5000cm3 beaker of water was put into the Oven and the temperature of the water was found to reach 810C after about 3hrs under an average ambient temperature of 300C. On no load test, the oven reached a maximum temperature of 112oC in 6hrs. In order to carry out the parametric studies and improve the performance of the Solar Oven, Mathematical models were developed and solved by using Characteristics-Based Split (CBS) Finite Element Method. The Model results were compared with the Experimental results and a good agreement ware found between the two results

Effect of frictional boundary conditions and percentage area reduction on the extrusion pressure of Aluminum AA6063 alloy using FE analysis modelling

© 2020 by the authors; licensee Growing Science, Canada. This is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).Finite Element Analysis was carried out to describe the effect of frictional boundary conditions and percentage reduction on deformation modelling (forward extrusion) of Aluminum AA6063 alloy. Curved die profiles of regular polygons (square, hexagonal, heptagonal, and octagonal) were designed using MATLAB R2009b and Autodesk Inventor 2013 to generate the coordinate and thesolid CAD model of the die profile respectively form a circular billet. The numerical analysis was performed using DeformTM-3D commercial package with frictional boundary conditions of 0.38 and 0.75 representing the wet and dry condition and varying the percentage reduction of 50%, 70%, and 90%. The results of the temperature distribution, effective stress, effective strain, andstrain rate were reported. As the percentage area reduction increases, the extrusion pressure also increases with an increasing frictional condition, and die length. Also, extrusion pressure decreases when the side of the polygon increases from square-shaped section follow by hexagonal shaped-section and least in octagonal shaped-section for both friction factors and percentage areareductions. For a given percentage reduction and cross-sectional area, there is no distinct difference between the predictive loads for the shaped-polygons. When the result of this analysis is compared with the experimental results from the literature, it is evident that DeformTM-3D is an effective tool for finite element analysis of non-isothermal deformation processes.Peer reviewedFinal Published versio

Experimental Characterization of Electrical Discharge Machining of Aluminum 6061 T6 Alloy using Different Dielectrics

Electrical discharge machining is a non-traditional machining method broadly employed in industries for machining of parts that have typical profiles and require great accuracy. This paper investigates the effects of electrical parameters: pulse-on-time and current on three performance measures (material removal rate, microstructures and electrode wear rate), using distilled water and kerosene as dielectrics. A comparison between dielectrics for the machining of aluminum 6061 T6 alloy material in terms of performance measures was performed. Aluminum 6061 T6 alloy material was selected, because of its growing use in the automotive and aerospace industrial sectors. The experimental sequence was designed using Taguchi technique of L9 orthogonal array by changing three levels of pulse-on-time and current, and test runs were performed separately for each dielectric. The results obtained show that greater electrode wear rate (EWR) and higher material removal rate (MRR) were achieved with distilled water when compared with kerosene. These greater EWR and MRR responses can be attributed to the early breakage of the weak oxide and carbide layers formed on the tool and alloy material surfaces, respectively. The innovative contributions of this study include, but are not limited to, the possibility of machining of aluminum 6061 T6 alloy with graphite electrode to enhance machinability and fast cutting rate employing two different dielectrics.Peer reviewe

Influence of Seeding Rate on Growth Performance and Yield of Early Maturing Sorghum

Heavy grazing pressure in Tanzanian semi-arid rangelands coupled with climate change and variability has resulted into severe decline in forage production and changes in vegetation composition. To increase forage biomass production in the face of climate change and variability, climate resilient fodder crops such as early maturing sorghum have been recommended in arid and semi-arid regions. However, paucity of information on the best agronomic practices especially the optimal seeding rate and row spacing fostered the need to carry out research on growth performance and yield of early maturing sorghum. The experiment was conducted at Magadu Dairy Farm to assess the Influence of Seeding Rate on Growth Performance and Yield of Early Maturing Sorghum. The experiment adopted the Complete Randomized Design (CRD), where different seeding rate (such as 8kg/ha, 12kg/ha, 16kg/ha, 200kg/ha) were assigned randomly and replicated three times making a total of 12 subplots. The row spaces were also varied in reciprocal order with seeding rate (60cm in 8kg/ha, 50cm in 12kg/ha, 40cm in 16kg/ha and 30cm in 20kg/ha). Parameters collected include, number of plants germinated, circumference of the plant, Dry matter (DM) yield and height of the plants. The data were subjected to One Way Analysis of Variance (ANOVA) using SAS program of 2014 to analyse the effect of seeding rate on growth attributes and yield of early maturing sorghum. The study established the positive correlation of seeding rate and number of plant as well as plant heights. On the contrary, seeding rate was found to be inversely proportion to plant thickness and number of leaves per plant. The above ground biomass was found to increase with increasing seeding rate up to 22.20 tonnes per ha and slightly declined at the highest seeding rate. We recommend further studies on nutritive values and palatability of sorghum to livestock

Analisis Kemampuan Berpikir Kritis Matematika Mahasiswa Jurusan Pendidikan Matematika pada Mata Kuliah Kalkulus I Materi Limit Fungsi

Berpikir kritis merupakan salah satu kemampuan yang sangat penting bagi peserta didik, khususnya mahasiswa agar dapat menghubungkan persoalan atau informasi yang diperolehnya melalui penyelidikan dan pengkajian secara sistematis sehingga menghasilkan ide atau solusi untuk pemecahan masalah dalam pembelajaran matematika. Penelitian ini merupakan penelitian deskriptif eksploratif dengan pendekatan kualitatif yang bertujuan menganalisis atau menggambarkan kemampuan berpikir kritis matematika mahasiswa jurusan pendidikan matematika pada materi limit fungsi aljabar. Indikator yang digunakan untuk menggambarkan kemampuan berpikir kritis matematika mahasiswa antara lain kemampuan identifikasi masalah, analisis, sintesis, inferensi, dan evaluasi. Teknik pengumpulan data terdiri dari observasi, tes tertulis, dan wawancara untuk memperdalam infomasi mengenai kemampuan berpikir kritis matematika mahasiswa. Subjek penelitian adalah mahasiswa semester II Jurusan Pendidikan Matematika Fakultas Matematika dan IPA Universitas Negeri Gorontalo tahun akademik 2014 yang telah selesai memprogramkan mata kuliah Kalkulus I. Sedangkan teknik analisis data sesuai dengan pendekatan kualitatif. Berdasarkan analisis data diperoleh hasil bahwa kemampuan berpikir kritis matematika mahasiswa jurusan pendidikan matematika pada mata kuliah kalkulus I materi limit fungsi aljabar tergolong sedang. Hal ini dipengaruhi oleh beberapa faktor antara lain kecermatan dalam mengabstraksi soal, penguasaan konsep-konsep limit fungsi aljabar dan materi prasyarat (kemampuan awal) serta penerapannya, kecenderungan mahasiswa dalam mengandalkan hafalan

The Friedreich ataxia GAA repeat expansion mutation induces comparable epigenetic changes in human and transgenic mouse brain and heart tissues

Friedreich ataxia (FRDA) is caused by a homozygous GAA repeat expansion mutation within intron 1 of the FXN gene, leading to reduced expression of frataxin protein. Evidence suggests that the mutation may induce epigenetic changes and heterochromatin formation, thereby impeding gene transcription. In particular, studies using FRDA patient blood and lymphoblastoid cell lines have detected increased DNA methylation of specific CpG sites upstream of the GAA repeat and histone modifications in regions flanking the GAA repeat. In this report we show that such epigenetic changes are also present in FRDA patient brain, cerebellum and heart tissues, the primary affected systems of the disorder. Bisulfite sequence analysis of the FXN flanking GAA regions reveals a shift in the FRDA DNA methylation profile, with upstream CpG sites becoming consistently hypermethylated and downstream CpG sites becoming consistently hypomethylated. We also identify differential DNA methylation at three specific CpG sites within the FXN promoter and one CpG site within exon 1. Furthermore, we show by chromatin immunoprecipitation (ChIP) analysis that there is overall decreased histone H3K9 acetylation together with increased H3K9 methylation of FRDA brain tissue. Further studies of brain, cerebellum and heart tissues from our GAA repeat expansion-containing FRDA YAC transgenic mice reveal comparable epigenetic changes to those detected in FRDA patient tissue. We have thus developed a mouse model that will be a valuable resource for future therapeutic studies targeting epigenetic modifications of the FXN gene to increase frataxin expression

Multi-objective optimisation for minimum quantity lubrication assisted milling process based on hybrid response surface methodology and multi-objective genetic algorithm

© 2019 by SAGE Publications Ltd.Parametric modelling and optimisation play an important role in choosing the best or optimal cutting conditions and parameters during machining to achieve the desirable results. However, analysis of optimisation of minimum quantity lubrication–assisted milling process has not been addressed in detail. Minimum quantity lubrication method is very effective for cost reduction and promotes green machining. Hence, this article focuses on minimum quantity lubrication–assisted milling machining parameters on AISI 1045 material surface roughness and power consumption. A novel low-cost power measurement system is developed to measure the power consumption. A predictive mathematical model is developed for surface roughness and power consumption. The effects of minimum quantity lubrication and machining parameters are examined to determine the optimum conditions with minimum surface roughness and minimum power consumption. Empirical models are developed to predict surface roughness and power of machine tool effectively and accurately using response surface methodology and multi-objective optimisation genetic algorithm. Comparison of results obtained from response surface methodology and multi-objective optimisation genetic algorithm depict that both measured and predicted values have a close agreement. This model could be helpful to select the best combination of end-milling machining parameters to save power consumption and time, consequently, increasing both productivity and profitability.Peer reviewedFinal Published versio