This research aims to study the influence of parameters that affect the mechanical properties of semi-solid-metal 7075 aluminum alloy with friction stir spot welding process. The parameters for this experiment such as rotation welding speed at 380, 760, 1240 and 2500 rpm and welding time at 60, 90 and 120 seconds were employed respectively. The study found that the welded specimens at all the conditions can be welded very well. Moreover, friction stir spot welding process showed that the hardness in weld zone had an average value at 79.83 HV which is lower than the hardness of the base metal. The shear tensile strength of the welded specimens had the average value approximately 194.20 MPa at rotation welding speed of 2500 rpm, welding time of 90 seconds and plunge of depth of 2 millimetres. The microstructure in the weld zone and thermal mechanical affected zone were deformed permanently. Therefore, friction stir spot welding process of this aluminum alloy provided good effects on mechanical properties. Statistical analysis showed that the coefficient of determination R-square was equal to 93.50 percent. This means that the variations of the experiments were controllable, such as equipment or other factors in the experiment. For the remaining, only 6.50 percent was uncontrolled factors.
This research aimed to study the design of the overhead crane of a small fishing boat maintenance factory according to the building and functional requirements of the project based on the ASME B30.2-2005 Standard. The results of the study showed that the design of the runway with steel structure BS: 5950: 2000 grade s460 provided vertical and horizontal deflection values of 4.96 and 16.62 respectively that did not exceed the allowed deflection. It is strong enough for use in construction when the stresses on the beam bridge were analysed by the finite element program compared with the strength of the reinforced steel providing a safety value of 1.83.
Objective of this research was to analyze the stress of a 48 kg LPG cylinder designed under Thai Industrial Standard TIS 27-254. The design was employed by using test pressure of 3.3 MPa and the tank wall thickness of 2.65 mm which provided the maximum tensile strength of 429.3 MPa, yield strength of 286.2 MPa and burst pressure of 5.99 MPa. The material used to produce the gas cylinder was SG295 grade steel with a yield strength of 300 MPa and a maximum tensile strength of 440 MPa, which covered the design requirements. The research results were found that at the 85 percent of cylinder volume, gas density of 0.54 kg / l, liquid height of 0.9367 m and gauge pressure of 0.073 psi gave circumferential and longitudinal stresses of 0.0357 MPa and 0.0178 MPa, respectively. According to analysis results of finite element method revealed that the stress concentration area was the circumference at the center position of the tank with the highest value at the welding joint.
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