Agus Suprihanto

Comparison of ratio loaded and unloaded foot area of flat foot and healthy foot in younger adults

This study is aimed to investigate loaded and unloaded foot area ratio (RFA, ratio of foot area) as special tests for the basis of clinical examination of flat foot and healthy foot. Type of foot is determined by Cavanagh’s arch indexes (AI) which is the ratio between mid foot area to entire footprint area excluding the toes. Type of foot is called high arch when AI AI≥0.21 and flat foot when AI>0.26. The entire loaded foot and footprint area for evaluating AI derived from a digital footprint is modified from document scanner, while the entire unloaded foot area derived from a 3D scanner. One hundred and two healthy students (87 males and 15 females, average aged 20 years and average BMI 22.51 kg/m 2 ) is asked voluntarily for doing footprint and scan. From 102 subjects found 63 participants identified as flat foot and 31 subjects are healthy feet. This study proves that the higher the value of AI the higher the value of RFA and foot type can be predicted by the value of RFA. For type of foot is high arch RFA RFA≥0.49 and for flat foot RFA>0.55.

Design and Testing of UMM Vertical Ball Mill (UVBM) for producing Aluminium Powder

UMM Vertical Ball Mill (UVBM) was intended to be the apparatus to produce metal powder with superior characteristic in production rate while retaining good quality of metal powder. The concept of design was adopting design theory of Phal and Beitz with emphasis on increasing of probability of success in engineering and economy aspects.Since it was designed as vertical ball mill, a new way to produce powder, then it need to be tested for the performance after manufactured. The test on UVBM was carried out by milling of aluminium chip for 5 (five) different milling time of 0.5 hours, 1 hour, 3 hours, 5 hours and 7 hours, and the powder product then be characterized for it morphology and size using Scanning Electron Microscope (SEM) and Sieve.The results of the study were the longer of the milling time, the finer of the powder. From the test results of SEM, the morphology of the powder with 5 variations of milling time were most of the powder in form of flake (flat), small round and angular (irregular). The distribution of powder size was best obtained on the variation of milling time 3 hours, 5 hours, and 7 hours with percentage of 200 mesh in size of 22.14 %, 64 % and 91.25 % respectively.

DISTRIBUSI TEGANGAN PADA PERCABANGAN PIPA 90O AKIBAT TEKANAN INTERNAL MENGGUNAKAN MEH

Piping system is very important in many industries. Ones of crucial in design of piping system are todetermine the stress distribution around the branch. In this research, the distributed stress over 90o branchpiping system was evaluated with finite element method. Five models piping 90o branch which differentratio of diameter of pipe have been developed. The load applied on the models is internal pressure.The results indicate that around the branch there is stress distribution. The maximum stress is located atcenter of the branch but decrease significantly in the distance 30mm-45mm from it. Beyond the distance75mm from center, for diameter ratio 1, the model gives good agreement with experiment data

The Effect of Cr & Cu on the Fatigue Strength of Grey Cast Irons

The mechanical properties of grey cast irons can be modified with alloying elements. Cr and Cu have been known as elements that can improve tensile strength of grey cast irons. The improvement of tensile strength can be influence of fatigue strength. The goal of this research is to study the effect of alloying Cr and Cu on the fatigue strength. Four materials of grey cast irons have been conducted to high cycle fatigue (HCF) testing on the rotating bending machine. The first material is grey cast irons without added Cr and Cu, and the other have added. The percentages of Cr have been added are 0,23% wt, 0,32%wt and 0,47%wt and Cu 0,6%wt to 0,7%wt. The metallography examinations and tensile test also have been conducted. The results of this research are the material has the same microstructure. The microstructures of its materials are pearlitic grey cast irons with graphite type VII, distribution A and size of graphite 3-5. The tensile, endurance and fatigue strength of materials, which added Cr and Cu significantly increasing, compared with base materials. The tensile strength rose from 191MPa to 232MPa and the endurance strength raised from 94 MPa to 110MPa. However three modified materials, which added Cr and Cu has the same effects.