AbstractThe microstructure transformation of AISI 8655, affecting to hardness and impact properties in various hardening processes, has been investigated in this work. AISI 8655 specimens which had been prepared before hardening processes were heated to austenite temperature and held for 30 minutes and 60 minutes then continued by rapid cooling in various medium (air, oil and water). The hardened steel specimens were tested by optical microscope to observe microstructure, brinell test and impact test respectively to measure hardness and impact strength properties. Martensite and bainite were microstructures that appeared after hardening processes. The holding time for 30 minutes gave higher hardness properties than the holding time for 60 minutes. However, the holding time for 60 minutes performed higher impact strength than that for 30 minutes. The highest of hardness was performed by the specimen cooled in water medium at 552 BHN and the highest of impact strength was performed by the specimen cooled in air medium at 7.2 J/mm2.
Aluminum is a light metal with good electrical conductivity and widely applied for electrical devices. One of its application is the circuit breaker component. The 2xxx series of aluminum alloy has a copper alloying element which increases its mechanical properties and improves quality of electrical conductivity. This research aims to obtain the best gating system design of the circuit breaker mold by ANSYS modeling. This research also is subject to measure the influence of Cu alloying to the rate of electrical conductivity, strength, and hardness in aluminum alloys for circuit breaker application by experimental working. Aluminum is alloyed with variations of 1; 2; 3; 4; and 5% copper addition. Modeling of thermal analysis and structural analysis was calculated by ANSYS Mechanical APDL with a finite element method to find the best design for the sand casting experiments. Chemical composition, metallography, brinnel hardness, tensile, XRD, and electrical conductivity tests were conducted in this study. The highest strength is 59.50 MPa was acquired on Al-3% Cu while the lowest strength is 37.43 MPa was on Al-1% Cu alloy. The peak of hardness 48.70 HBN could be drawn at Al-4% Cu. In the other hand, the dip of it was Al 1% Cu of 25.5 HBN. The last variable, conductivity, has the highest amount as of Al-5C, alloys with a value of 12.88 S / M, which is found on Al-1Cu with a value of 9.30 S/m.
Increased consumption of bottled water has a negative impact on the environment due to plastic waste. This study intends to assess the perceptions of Indonesian students toward tap water. This cross-sectional survey was conducted online using an online questionnaire. From 1,034 undergraduate students, our findings revealed that Indonesian students had a relatively low rate of bottled water consumption. Employing the framework of the theory of planned behavior, all factors were recognized as significant factors driving tap water consumption. Students who reported drinking two or fewer bottles of water per week perceive that tap water is safe and clean for consumption is practical, and has almost the same color, taste, and smell as bottled water. Students concede that consuming tap water is a habit and consider this action necessary to preserve the environment. As observed from demographic characteristics, students’ fields of study affect the choice of drinking water. This study has contributed to uncovering the identified factors that determine the habits of students consuming tap water. Apart from the importance of environmental education, increasing the availability of ready-to-drink tap water facilities and disseminating information regarding the benefits and safety of consuming this water are also important factors in reducing the use of bottled water.
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