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Conditions around the environment are crucial in the process of welding defects. Temperature, humidity, and air velocity are determinants of hydrogen rise. The formation of hydrogen in the air caused by unfavorable environment can cause defects in the welded joint. The more vapor in the air, the more hydrogen is formed. One welding defect caused by hydrogen content is porosity. Porosity is formed in aluminum welding due to the presence of hydrogen trapped in the Al weld metal. This study discusses welding protection involving experiments with variations in temperature of 20 ° C, 25 ° C, 30 ° C, variations in relative humidity of 65%, 72%, 80%, and air velocity of 1.5m/s; 1.7 m/s; 2.0 m/s so as to minimize porosity defects at the welding joint due to hydrogen. In research shows the lower the temperature, the lower the solubility of hydrogen, this happens because the solubility of hydrogen at low temperatures is very limited. While welding is carried out with a relatively high humidity level, the higher the hydrogen reserves. [ABSTRACT FROM AUTHOR]

Underwater welding is chiepest and easiest methode in the maintenance and repairing offshore engineering equipment construction. It have disadvantage due to the water environment such as the high cooling rate and the hydrostatic pressure. Post weld heat treatment (PWHT) was proposed to improve underwater wet welded joint. Underwater wet welding processes were performed in the water depth (0 m, 2.5 m and 5.0 m ) and water flow ( 0 m/s, 1 m/s and 2 m/s). PWHT were conduct in constant temperature of 5600C and holding time of 75 minutes. The result show that highest hardness was found in underwater wet welding with a depth of 5 m at water flow rate 2m/s with highest value in the weld metal area 180 VN, HAZ 171 VN and base metal 131 VN with tensile strength 199,64 Mpa. Whereas, weld joints which have the lowest hardness is 2.5 m with water flow rate 0m/s produced the weld metal hardness value 145 VN, HAZ 132 VN, BM 127.9 VN and tensile strength 173,1. Distribution hardnes value increased in weld metal due to presence of ferrite second phase (FSP) which has a major contribution increasing hardness. In addition, due to the heat input in PWHT FSP structure that is brittle transforming into the acicular ferrite. [ABSTRACT FROM AUTHOR]

Torsional rigidity of a vehicle is a measure of how much force needed to be applied to twist the frame by one degree. An appropriate torsional rigidity improves the ride quality of a vehicle. This paper delivered the engineering design and experimental works of a test apparatus for chassis testing of a formula student car. The apparatus is a solid jig with an adjustable mount equipped with a rotational loading arm at the front axis point and a fix mount at rear axis point. Firstly, the apparatus was design using 3D engineering drawing software, then the object was analyzed its strength using finite element analysis approach. During simulation, the loading condition was set at a worse condition that was locking the arm bearing. A 1 kN was applied at the loading arm and the critical part was determined from the stress distribution. An iterative design was undertaken to improve the critical part by changing the material until reach the best material, the material for the simulation was aluminum alloy, structural steel, and stainless steel. Finally simulation having achieved a reasonable safety factor that was 1.33, the workshop drawing was finalized for further prototyping process. [ABSTRACT FROM AUTHOR]

Underwater wet welding is widely used to maintenance and repair of offshore engineering equipment construction. Up to now, the research underwater wet welding only is carried out in a laboratory scale with a shallow. So the depth factor is ignored, meanwhile the depth of the water will affect cooling rate and hyrostatic pressure. The cooling rate is usually related with the volume fractions of microstructure and mechanical properties. Therefore, the experiment focused on the microstructures, hardness and tensile strength of low carbon steel welded joints that were welded using welding on air and underwater wet welding under several water depths (2.5 m, 5 m and 10m). The spesimens at underwater wet welding under several water depths 2.5 m, 5 m and 10 m produced the tensile strength 277 MPa, 303 MPa and 313 MPa. The increase depth of water makes the cooling rate increase. With increase the cooling rate, the tensile strength of weld metal increased due to increase volume fraction of acicular ferrite. The fracture surface was investigated by SEM (scanning electron microscope) appear porosity of spesimens weld joint at underwater wet welded due to hydrogen absorbed is very high, so the underwater weld metal are easy fragile. [ABSTRACT FROM AUTHOR]

A great deal of research has been conducted on composite; one of which is related brake pad in automotive area. Nowadays, the use of material should have a high economic value and eco-friendly properties. Such requirements have encouraged researchers to produce eco-friendly composite material by using natural fibers. Natural fiber is an alternative to produce new brake pad composite that has required mechanical properties and economic value and is ecofriendly. The brake pad composite should have heat resistance value, coefficient of friction, and mechanical strength as needed during the process of braking. In this research, Cantala fibers were chosen as strengthening material of brake pad composite. The volume fractions of Cantala fiber evaluated in this study were 0%, 4%, 8%, and 12%. Other materials used in the composition of brake pad composite production were NBR, fly ash, graphite, CaCO3, phenolic resin, and cashew dust. The specimens were manufactured using the following sequential processes: mixing the ingredients, cold pressing, hot pressing, and finally post curing of the specimens. The result showed an increase in flexural strength of composite friction brake along with the increase in Cantala fiber volume fraction. [ABSTRACT FROM AUTHOR]

The purpose of this research is to obtain a mathematical model (Full Vehicle Model) and compare the performance of passive and active suspension systems of a Three-Wheels Reverse Trike vehicle. Vehicle suspension system should able to provide good steering handling and passenger comfort. Vehicle suspension system generally only uses passive suspension components with fix spring and damper coefficients. An active suspension developed from the traditional (passive) suspension design can directly control the actuator force in the suspension system. In this paper, modeling and simulation of passive and active suspension system for a Full Vehicle Model is performed using Simulink-MATLAB software. Ziegler & Nichols tuning method is used to obtain controller parameters of Proportional Integral Derivative (PID) controller. Comparison between passive and active suspension with PID controller is conducted for disturbances input of single bump road surface profile 0.1 meters. The results are the displacement and acceleration of the vehicle body in the vertical direction of active suspension system with PID control is better in providing handling capabilities and comfort for the driver than of passive suspension system. The acceleration of 1,8G with the down time of 2.5 seconds is smaller than the acceleration of 2.5G with down time of 5.5 seconds. [ABSTRACT FROM AUTHOR]

Crucible which is used in melting aluminum process repeatedly examined and had thermal cycles examination. The contact between liquid aluminum and the surface of steel crucible influences on the intermetallic material compound. This research will observe aluminum diffusion process on steel crucible surface during melting process aluminum without degassing. Aluminum diffusion process to the steel is intermetallic material compound a tongue-shaped. The intermetallic material compound can be detected to the steel that examined 10 thermal cycles. The obtaining intermetallic material compound are Fe3Al, Fe2Al3, and Fe2Al5. The domination of Fe2Al3 can be obtained on experiencing 50 thermal cycles and 100 thermal cycles. [ABSTRACT FROM AUTHOR]

Crucible which is used in melting aluminum process repeatedly examined and had thermal cycles examination. The contact between liquid aluminum and the surface of steel crucible influences on the intermetallic material compound. This research will observe aluminum diffusion process on steel crucible surface during melting process aluminum without degassing. Aluminum diffusion process to the steel is intermetallic material compound a tongue-shaped. The intermetallic material compound can be detected to the steel that examined 10 thermal cycles. The obtaining intermetallic material compound are Fe3Al, Fe2Al3, and Fe2Al5. The domination of Fe2Al3 can be obtained on experiencing 50 thermal cycles and 100 thermal cycles. [ABSTRACT FROM AUTHOR]

The most effective chassis control system for improving vehicle safety during severe braking is antilock braking system (ABS). Antilock effect can be gained by vibrate the pad brake at 7 to 20 cycle per second. The aim of this study is to design a new method of antilock braking system with membrane elastic vibrated by solenoid. The influence of the pressure fluctuations of brake fluid is investigated. Vibration data is collected using a small portable accelerometer-slam stick. The experiment results that the vibration of brake pad caused by controlled solenoid excitation at 10 Hz is obtained by our new method. The result of measurements can be altered by varying brake fluid pressure. [ABSTRACT FROM AUTHOR]

Thermal arc spray nickel coating is widely used for decorative and functional applications, by improving corrosion resistance, wear resistance, heat resistence or by modifying other properties of the coated materials. There are several properties have been studied. Layer thickness of nickel thermal sprayed steel may be make harder the substrate surface. In this study, the effect of layer thickness of nickel thermal sprayed steel has been investigated. The rectangular substrate specimens were coated by Ni-5 wt.% Al using wire arc spray method. The thickness of coating layers were in range from 0.4 to 1.0mm. Different thickness of coating layers were conducted to investigate their effect on hardness and morphology. The coating layer was examined by using microvickers and scanning electron microscope with EDX attachment. Generally, the hardness at the interface increased with increasing thickness of coating layers for all specimens due to higher heat input during spraying process. Morphology analysis result that during spraying process aluminum would react with surrounding oxygen and form aluminum oxide at outer surface of splat. Moreover, porosity was formed in coating layers. However, presence porosity is not related to thickness of coating material. The thicker coating layer resulted highesr of hardness and bond strength. [ABSTRACT FROM AUTHOR]