Spring is a component that functions to receive dynamic load and providescomfort in driving. The problem is the leaf spring is sometimes broken due to theoverload or unfavorable road conditions. The solution for that problem is grafting using the SMAW welding.This study aims to determine the effect of variations in the welding currentto the impact strength, hardness and microstructure. Types of weld used is SMAW with a variety of welding current of 100 A, 120 A and 140 A and the type of seam used is the type of seam V.The highest impact strength test was 1.698 j/mm2at 100 A and the highest hardness test was 355.338 HVN at 140 A. In addition, the micro structure at the welding area has bigger grain size and more pearlite structure at 140 A. Keywords: welding current, impact strength, hardness, micro structure AbstrakPegas adalah suatu komponen yang berfungsi untuk menerima beban dinamis dan memberikan kenyamanan dalam berkendara. Permasalahan yang sering dialami oleh pegas daun adalah patah akibat beban lebih atau kondisi jalan yang kurang baik. Penanganan pada hal seperti ini adalah penyambungan menggunakan las SMAW.Penelitian ini bertujuan untuk mengetahui pengaruh variasi arus pengelasan terhadap kekuatan impak, kekerasan dan Struktur mikro. Jenis las yang digunakan adalah las SMAW. Variasi arus pengelasan yang digunakanadalah 100 A, 120 A dan 140 A. Jenis kampuh yang digunakan adalah jenis kampuh V.Hasil uji kekuatan impak tertinggi diperoleh pada variasi arus 100 A yaitu sebesar 1,698 J/mm2. Hasil uji kekerasan tertinggi diperoleh pada variasi arus 140 A yaitu sebesar 355,338 HVN. Struktur mikro pada daerah las memiliki ukuran butiran yang semakin besar dan struktur perlit yang semakin banyak untuk variasi arus 140 A.Kata kunci: arus pengelasan, kekuatan impak, kekerasan, struktur mikro

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Aluminum alloy AA 2024-T3 is widely applied in the aircraft industry because it has good mechanical properties such as; light weight, good conductivity and the corrosion resistance. However Aluminium 2024-T3 susceptible to wearing. One method to improve the wear resistance o f AA 2024-T3 is the anodizing process. The aims of this research to study the effect of current density and anodizing time against the hardness of aluminum alloy AA 2024-T3. The process of anodizing was carried out using 10 percent sulfuric acid solution with the current density of 1.5 Ampere per decimeters square, 3.0 Ampere per decimeters square and 4.5 Ampere per decimeters square with immersion times of 30, 40, 50 and 60 minutes. Furthermore, the surface hardness was measured by using the Vickers hardness test method. As the supporting data the composition of the test conducted, testing the microstructure, and vickers hardness test. This study shows that the surface hardness of aluminum alloy AA 2024-T3 is influenced by the current density and anodizing time with varying values. Its shows that higher current density o f the anodizing caused optimal time tends to be short. The longer anodising time it will produce greater layer of aluminum oxide.

Since a long time ago, Padang City has been recognized as one in most-earthquake and tsunami prone city in the world. The successive significant earthquakes that have struck western coast of Sumatra Island from 2004 to 2010 seems to warn the city about its prone condition. The last major Padang-Pariaman earthquake on September 30, 2009, for instance, has caused hundreds of death and lousy damage to thousands of houses and buildings in city. Recently, several new multistory reinforced concrete (RC) buildings have been established in this area. Its include such buildings as government office, mosques, hotels, school and university. The city government plans to use these buildings as vertical evacuation facilities if an earthquake followed by a tsunami hit the city in the near-future. As a consequence, of course, these infrastructures should be well designed and constructed to resist the future earthquakes motion. This paper discusses an evaluation of the seismic performance of an existing multistory RC building in Padang city. The building was a ten-story of hotel RC building located near the coastline of Padang city. A series Pushover and Time History Analyses were conducted to examine the seismic performance of the target R/C building. It uses STructural Earthquake Response Analysis (STERA-3D), a computer software based on the nonlinear finite element method. The Pushover analysis was conducted for maximum drift ratio 1/200 in X and Y directions, respectively. The input ground motion in a maximum acceleration of about 400 gals and 600 gals for 60 seconds’ excitation were used for the Time History Analysis. These input ground motions were generated from the recorded ground motion of 2009 Padang-Pariaman earthquake. The result of the analyses suggest that the current target multistory RC building has outstanding seismic performance. The result is based on the level of damage of the structural components, base shear, inter-story drift, lateral displacement, dynamic responses and the seismic capacity spectrum of the analytical model.

This study's objective is to review the consequence of the COVID-19 epidemic on physical activities, sedentary lifestyles, screen time, and changes in the nutritional status of school-age children. The outcomes of this study are intended to be applicable to obesity management in children. This study reviewed full-text articles and open-access publications on the sedentary lifestyle of children during the pandemic. and the data were analyzed using cohort, case-control, and cross-sectional designs. The results of reviewing 17 articles show that school-age children's physical activities and nutritional status have decreased, but their sedentary lifestyle and screen time have increased due to social restrictions during the COVID-19 pandemic. Children's decreased physical activities are caused by the absence of a comparable replacement mechanism as that before the pandemic. Meanwhile, the increasingly sedentary lifestyle highly influences children's physical and mental health. Screen time has also increased and is unavoidable during the pandemic because children's activities were limited and their learning systems are switched to online learning; as a result, their supporting sedentary lifestyle increases while physical activities decrease. These factors have changed the nutritional status of children during the pandemic. These results support the idea that the pandemic will impact the health of school-age children, especially their nutritional status. This review concludes that it is important to establish policies that prevent children's further health effects, such as obesity, caused by COVID-19.