Applied Mechanics and Materials Vol. 758

Abstract: In this study, the mechanical properties and corrosion properties of plasma nitrocarburized 304 stainless steel at various processing times was investigated. Plasma nitrocarburizing was carried out at different processing time durations which varied from 60 min to 300 min at fixed temperature of 500 °C in an atmosphere of 78 vol.% N₂, 19 vol.% H₂ and 3 vol.% CH₄. An Optical microscope and SEM coupled with EDS have been used to characterize the microstructural and the elemental depth profiles in which the thickness of the modified layers is derived. Microindentation method is used for the study of mechanical performance of the nitrocarburized material. Corrosion properties were investigated using potentiostat method in a 1 wt% NaCl solution. The result shows that the microhardness increases to a maximum value of more than two times compared to that of the untreated one. The corrosion performance was found being treatment time duration dependent.

Abstract: Bicycle frames on the market are generally made from a pipe connected by welding process. Bicycles are made by big companies, because it requires forming technology of raw materials for the pipe production and complex welding technologies. In order to reduce the dependence on raw materials and pipe welding processes, an alternative technology for bicycle frame manufacturing process is investigated. This study is aimed to examine the use of casting technology in the manufacturing process of bicycle frame. Production of bicycle frames in limited quantities is possible by using the casting process. To achieve these objectives, it is necessary to redesign the bicycle frame suitable for the casting process. Prototypes have been produced and the first bike is in the testing phase. Initilly , the bicycle is relatively heavy (7 kg). The optimization of the design reduces to a light and strong frame. The frame has a weight of 3.74 kg. The prototype of the frame has been succesfully casted by sand casting method.

Abstract: Most of the energy from the vehicle is wasted in the form of heat energy and vibration. On vehicles, the largest vibration occurs in the suspension system. The development of a mechanism which can recover the vibration energy and convert it into electrical energy, named Regenerative Shock Absorber (RSA), will be detailed in this paper. The prototype of RSA which consist of gear transmission and an electromagnetic type electric generator was studied and analyzed. Electrical circuit signal conditioner / stabilizer is added into the RSA system to stabilize the output current of the generator so that the generated electrical energy can be stored in the battery of 6 volts. The characteristics of the RSA are obtained by testing the value of the damping coefficient, the energy absorbtion capacity, and the generated electrical energy before and after going through a series of signal conditioner. Experiment was also performed by measuring the acceleration response time of the sprung and un-sprung suspension system that uses RSA with damping ratio value of 0.6. From this research, it is found that RSA design with stabilizer circuit can produce more stable electric current and voltage. The measurement results show the value of the electrical voltage output through the generator is fluctuating with an average value of 15 volts and a constant 6 volts output is obtained through the signal conditioning circuit. Furthermore, the dynamic response is obtained in the form of acceleration time-value of less than 0.2 m/s² in a corresponding ISO 2631 standard is stated very comfortable.

Abstract: Fire in a typical car park is capable to induce large Heat Release Rate. The heat release rate in car park can be ranged from 500 kW to 20 MW depends on the ventilation condition of the car - park and the car itself. When fire occurs in poor ventilated car, i.e. the window is closed, fire will immediately burn out. Otherwise, fire will rapidly spreads and consume adjacent car. This condition can result in wide spread of fire involving all of the available car in the parking lot considering the availability of ventilation in underground car - park which strongly affect the fire and smoke spread. In this paper, a typical large underground car - park is being considered by varying the aspect ratio of the parking lot shape with constant floor to ceiling height. The effect of horizontal ventilation system and its thrust direction on the spread of smoke, its flow pattern, and overall CO distribution will be covered. In addition, the impact of additional building structure, basement aspect ratio, and ceiling beam will be discussed by considering it effect on smoke flow pattern and extraction effectiveness. Furthermore, based on the simulation which had been carried out the dilution of smoke by the air from the horizontal ventilation system is significantly increasing the CO concentration at 2 m height as it disturbed the smoke concentration stratification.

Abstract: Water current turbine with vertical blade can be used on the river flow, ocean current or tidal current. The three parallel turbines with 40 degree azimuth different, have advantages doubling the power output and diminish the torque fluctuation. When the turbine equipped by the concentrator channeling device, the performance increased and the self-starting capability also augmented. During the experiments is indicated the flow phenomenon behind the turbine, the vortex formation created additional head or formation of low hydraulic level and facilitate the turbine coefficient of power produced greater than BETZ limit. The development of water current turbine at Fluid Machinery Laboratory FTMD ITB is starting with searching numerical simulation model at ANSYS 12.1 using NACA0018 blade profile comparing with experiment and carry out that the Reynolds Stress Model is adequate between simulation and the experiments. Further this model simulate variants of c/R (Chord Radius Ratio), TSR (Tip Speed Ratio), distance of shaft and configuration of the concentrator channeling device at the water flow velocity. Using NACA0018 blade profile as the best chose from the NACA0012, NACA0015, NACA0021 and NACA0024, Water current turbine equipped by the concentrator channeling device with c/R=0,32. The numerical simulation at the flow velocity of 0,4 m/s give C_P =0,39 at TSR=3,2 but at the experiments measurement give C_P =0,35 and TSR= 3,88. Other experimental case at flow velocity 0,6 m/s give C_P =0,38 at TSR=2,18 the experiments and simulation result different is due to the friction loss of the transmission. The NACA0018 optimized by using MATLAB and XFOIL has better stall characteristic with angle of attack extend to 45 degree. Equipped by NACA0018 optimized, the three parallel current water turbine with concentrator channeling device numerical simulation at velocity V=0,4 m/s produce C_P =0,64 at TSR=2,97 and at Velocity V=0,6 m/s produce C_P =0,51 at TSR=3,35. Experiments results shown has C_P= 0.64 greater than BETZ limit at the TSR= 2.97on the low flow velocity 0,4 m/s. In the operational is expected its turbine will operated at the higher flow velocity greater than 1,2 m/s to get better power density and the construction will smaller and lighter for unity of power. Keywords : Water Current Turbine, Channeling Device, Numerical Simulation, Experimental of Parallel Water Current Turbine, Blade Optimized

Abstract: This work presents an experimental work in orbiting EDM which design of the electrode used adopt the non-uniform offset method formulated by the authors. A brief explanation about the design principle is presented in this paper as well as comparison of experimental machining results between uniform tool offset and the said method. The design method is implemented in a commercial CAD software and the system has been proven effective to cut design lead time and reduce error. The experimental part on orbiting EDM adopting the said-method yields improved machining accuracy and machined surface quality.

Abstract: Studies conducted on axial flow hydraulic turbine by comparing the performance of turbines which use a single rotor and two rotors that rotate in opposite (contra-rotating). Both turbines are designed to generate energy utilizing a very low head water flow. Single rotor turbine consists of one row of guide vane and one row of rotor blade. Contra-rotating rotor turbine consists of one row of guide vane and two rows of rotor blade, which is the front rotor blade also serves as a guide vane for the rear rotor. Both of turbines are designed for the same flow and operating conditions. The results of numerical studies show that both of turbines can be applied with a fairly high efficiency, however the single rotor turbine is significantly higher. Especially for contra-rotating turbine, the total power that generated at the same operating conditions will increase because powers are resulted from both of rotors, but the effective head required will be significantly increase compare to the single-rotor turbine. These results may be used as a reference in the development of axial flow hydraulic turbine for very low head sites to expand the applications. Keywords: Single rotor, contra-rotating rotor, axial flow, very low head, hydraulic turbine.

Abstract: Electric mobility seems to be an innovative alternative to future urban transport. In this study, a steady-state cornering model of a three-wheel narrow electric vehicle is derived. The steady-state cornering analysis is conducted by varying the location of the vehicle center of gravity, speed and tilt angle. From this analysis, the center of gravity location and tilt angle that gives better cornering characteristics can be obtained. Therefore, this analysis helps and can be used as starting point to design the chassis and the tilting control system of the three-wheel narrow electric vehicle.