ANALISIS KOEFISIEN PENGURANGAN TATAL (CHIP REDUCTION COEFFICIENT) PADA PEMESINAN BUBUT MAGNESIUM AZ31 MENGGUNAKAN PAHAT PUTAR

Coefficient reduction chip atau pengurangan tatap dianalisa menggunakan Metode Anova untuk menentukan pengaruh dari parameter input untuk setiap variasi eksperimen pada proses permesinan, sekaligus juga menentukan persentase pengaruh parameter individual. Metode Taguchi dipilih untuk mengurangi jumlah total dari percobaan yang dilakukan dan menghilangkan aspek yang tidak perlu dipertahankan, mengurangi biaya percobaan, sederhana dan mendapatkan hasil yang presisi. Penelitian ini bertujuan untuk menganalisa koefisien pengurangan tatal yang terjadi pada saat pemesinan menggunakan material paduan magnesium AZ3. Pada penelitian ini, proses pemesinan dilakukan menggunakan mesin bubut dengan jenis pahat berputar, yang mana pahat yang digunakan adalah pahat karbida jenis round insert. Sementara itu metode pengujian yang diterapkan adalah menggunakan Metode Taguchi dan ANOVA. Sementara itu, diameter benda kerja digunakan sebesar 35 mm dan Panjang 100 mm, kedalaman potong 1 mm dan kecepatan potong 80, 120, 160 mm/min, kadar pemakanan 0,10 0,15 0,20 mm/rev, kecepatan putaran pahat 50, 80, 120 rpm. Hasil dari penelitian ini menunjukan bahwan nilai koefisian pengurangan tatal terendah sebesar adalah 1,44, yang mana diperoleh pada parameter kecepatan potong 80 mm/min, kedalaman potong 1 mm, kadar pemakanan 0,10 mm/rev dan kecepatan putaran pahat 50 rpm. Dari semua faktor yang dianalisa, didapati bahwa faktor yang berpengaruh signifikan yaitu kecepatan potong da kadar pemakanan.

Modelling of Drag Force Reduction for a Waterjet Propulsion System

The paper provides simulation results for SUP (Stand Up Paddle) board appendage resistance. Additional propulsion is added to the SUP board. It is equipped with a waterjet. The waterjet is attached to the board rudder. This increases the drag coefficient for rudder five times. To reduce the drag variable, design options for the waterjet duct were proposed. The simulation tests were performed using SolidWorks Flow software using two types of simulations, namely, the pressure on the body and the flow around the body. The objective was to streamline the bluff duct of the waterjet and thus to create the appendage design with minimum drag force from fluid flow and possibly greater Inlet Velocity Ratio. Calculations showed that rounding-off the edges of waterjet duct resulted in 35 % of drag coefficient reduction, while further streamlining reduced it by additional 10 %.

Aerodynamics Analysis and Range Enhancement Study of 81mm Mortar Shell (French Design)

The aim of this research is performing the Computational Fluid Dynamics (CFD) analysis of 81mm Mortar Shell (French Design). The analysis is performed using ANSYS Fluent Software on three different Mach numbers (0.72, 0.76, and 0.84) and results are compared with existing design of 81mm HE M57D A2 Mortar. The drag coefficient of new modified design is found to be less than the existing model. The range of mortar shell is increased by 271 meters because of low drag coefficient with 5.96% percent increase in range and 15.73% decrease in drag coefficient value. Parabolic type; light weighted material fuze casing applied over the existing fuze will result in increase in aerodynamics, range enhancement and drag coefficient reduction. Weight optimization by using lighter material for mortar components and increasing the muzzle velocity can also increase flight duration of the projectile and increase its range. The analysis on 81mm Mortar Shell is a part of range enhancement study to overcome the short fall in required range of mortar shells.

Experimental Investigation of the Effect of Superhydrophobic Coating and Microbubbles Lubrication on the Resistance of a Scaled Ship

Skin friction in marine vessels constitutes one of the major issues that have negative environmental and financial impact due to the increased energy consumption. In this paper, the combination of two skin friction reduction techniques of superhydrophobic coating and microbubble lubrication are investigated experimentally. Microbubbles of up to 20 [μm] are introduced in the boundary layer through microbubble generators attached on the stem of a 2.52 [m] long ship treated with a superhydrophobic nano-ceramic coating. Resistance measurements are conducted at various towing speeds and trim angles and a skin friction coefficient reduction of up to 2.15% is noted.

Analysis for Resistance Reduction of an Amazon School Boat Through Hull Shape Modification Utilizing a CFD Tool

The waterway system of the Brazilian Amazonian region is one of the most complex in the world, being of vital importance for the daily circulation of passengers and cargo, and in this scenario, the FNDE (National Fund for Development of Education) provided the implementation of school boats for the transportation of riverine students to their classrooms. However, one of the school boat models presented operational inefficiency, as well as increased fuel consumption and travel duration. This work investigates the hydrodynamic causes of this inefficiency by analyzing dynamic pressure distributions on the hull, streamlines, and wave train generation and identifying hull shape regions that would hinder the flow. Through Computational Fluid Dynamics (CFD) simulations and analysis, a hull shape modification is proposed in order to reduce the resistance to forward motion and a comparison is made with the results of another research report, using the same hull geometry and speed range in simulations performed in other CFD software. Due to the hydrodynamic analysis, it can be inferred that the prototype hull form is inappropriate for the proposed operation regime in this project, and an agreement on the resistance coefficient reduction rates can be observed between use of both software, where a maximum total resistance coefficient reduction of 25.06% is achieved.