As the research on composite materials based on natural resources proliferates further, ramie fiber and polylactic acid (PLA), whch are fully biodegradable composite materials, are expected to be used for mechanical application due to their excellent strength and degradability. Various natural fibers have been applied to a wind turbine blade composite structure, as reinforcement material. However, none of them are fully biodegradable, as the matrix still uses synthetic resins. Hence, this study aims to theoretically optimize the fully biodegradable ramie/PLA laminate design using its lamina orientation on a taper-less blade shell of a wind turbine, as the operating structure experienced multiaxial loading through bending and torsional moment derived by the wind. The selection of taper-less blades was made due to their congruence with the wind speed categorization in southeastern Indonesian territory. The optimization was carried out using the nonlinear Generalized Reduced Gradient (GRG) method on Microsoft Excel. The optimized laminate result is in a stacking sequence of [-4°, 24°, 47°, 65°, 74°, 79°]S that delivers the factor of safety, which is the ratio between the allowable stress and the actual stress, of 7.296 and 18.057 on the longitudinal axis and the laminate shear-plane, respectively, This renders the composite laminate highly safe, both theoretically and numerically.

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The development of computer aided design (CAE) technology, especially casting simulation software (Magmasoft v5), can be utilized maximally as a tool to verify the design of castings that have been made to be able to meet the elements of QCD (quality, cost, delivery) and compete in the market. This study aims to obtain an optimal ESV housing casting design by reviewing and modifying the casting design in terms of both quality and economics. The process of design optimization with casting simulation is an important step in the design and development of casting products to improve casting yield and casting quality. The optimal design of castings is obtained by improving the design through pouring system using bottom pouring and optimizing the riser design. The results of this study obtained Design # 2 as a design choice of pouring system because it can improve the quality of casting products. Design # 2 optimized again into Design # 4 as the optimum design and able to increase the yield casting by 5.11% from the previous design (Design # 2). The result of techno economic analysis shows that by allocating 4% budget for design cost can contribute to decrease of production cost of foundry ESV housing up to 54,95%.

Generally, the crash box on automobile vehicles is a thin-walled structure with a square cross-section. The majority of research was carried out for a long time to find the optimum crashworthiness indicator. In this study, numerical simulations and experimental tests are used to investigate the effect of the corner radius of a square cross-section thin-walled structure on crashworthiness indicators. Quasi-static analysis with mild steel material produces the mean force (Pm) error value is less than 3% while varying the corner radius ranging from zero to 1 mm, 2 mm, and 3 mm shows energy absorption (EA) and peak force (Pmax) decreased. Keyword: Thin-walled square tube, Mild steel, Numerical simulation, Experimental test, Crashworthiness indicators.

AbstrakDalam penelitian ini simulasi dinamis transien diterapkan pada crankshaft dengan silinder ganda empat stroke. Analisis elemen hingga dilakukan dengan menggunakan software bantu ANSYS untuk memperoleh tegangan von-misses di lokasi kritis, sedangkan permodelan 3D menggunakan software 3D modeling CATIA. Beban dan kondisi batas yang diterapkan sesuai dengan kondisi engine mounting di ANSYS. Simulasi transien di mana pembebanan didasarkan pada waktu diharapkan dapat memperoleh kedalaman dari konsentrasi tegangan. Hal ini dapat membantu untuk proses m dari crankshaft, pengerasan permukaan. PENDAHULUANCrankshaft merupakan komponen dalam mesin dengan geometri yang kompleks, di mana bagian utama crankshaft terdiri dari poros yang berputar pada bantalan utama, crankpin dan counterwight. Crankshaft berfungsi mengubah gerak resipro dari piston menjadi gerak rotasi dalam mekanisme pembakaran internal. Gaya piston dan gaya inersia piston yang dihasilkan dari proses pembakaran internal mengakibatkan pembebanan fluktuatif berupa beban torsional dan beban tekuk (1) . Oleh karenanya crankshaft harus cukup kuat untuk menahan gaya-gaya yang bekerja selama mesin beroperasi.Sudah sejak lama metode desain crankshaft dikembangkan melalui perhitungan manual dengan rumus teroritis sampai pada penggunaan software bantu CAD serta CAE (2) . Dari hal tersebut, tantangan enjinir pada saat ini lebih besar untuk dapat mengembangkan desain yang terjamin kelayakannya.Desain geometri merupakan faktor utama dari kemampuan crankshaft, akan tetapi pemilihan dan perlakuan permukaan material baja juga menentukan ketahanan komponen. Perlakuan permukaan pada crankshaft

The application of spot-welding in the automotive industry, especially the electric-based vehicle frame structure, has been optimized to meet passenger and battery compartment safety factors. The present numerical study of the electric-based vehicle frame structure with the top hat cross-sectional model validated the experimental results of reference, which then modified the spot-welding pitch to determine the crashworthiness effect and criteria. The numerical simulation results show that reducing spot-welding pitch in vertical direction can increase energy absorption (EA) by 1.70% - 9.91%, while bringing spot-welding pitch closer to the flange's outer edge can reduce its maximum force (Fmax) by 8.11% - 21.67%. Keywords: Spot-welding; Top Hat Structure; Crashworthiness; Numerical Simulation; Electric Vehicle.

Abstrak Perkembangan mesin-mesin elektrik terutama Bow Thruster bagi sektor kemaritiman sangat signifikan. Dari beberapa komponen penting dalam Bow Thruster, rotor terutama poros dan bantalan bearing mempunyai peran penting sehingga  perlu dilakukan analisa. Analisa dinamik merupakan analisa untuk mengetahui sifat-sifat dinamik rotor akibat pengaruh putaran terhadap frekuensi pribadi. Pada makalah ini analisa dinamik dikembangkan dengan pemodelan rotor menggunakan Euler-Bernoulli Beam (EBB). Hasil dari analisa dinamik rotor ini menunjukan putaran kritis dan modus getar dari rotor Bow Thruster. Kata kunci : Rotordinamik, Euler-Bernoilli Beam, Poros, Putaran Kritis, Modus Getar. AbstractThe development of electric machines, especially Bow Thruster, for the maritime sector is significantly increased. The several important components in Bow Thruster, rotors, especially shaft and bearings, have an important role to analyzed. Dynamic analysis is an analysis to determine the dynamic properties of rotors due to the effect of rotation on natural frequency. In this paper a dynamic analysis, rotor modeling was developed using Euler-Bernoulli Beam (EBB). The results of this rotor dynamic analysis show the critical speed and mode shapes of the Bow Thruster rotor. Key Words : Rotor Dynamic, Euler-Bernoulli Beam, Shaft, Critical Speed, Mode Shape.