A calibration is an activity to determine the conventional validity of the appointment value of measuring instruments and measuring materials by comparing them to standard measurements that are traceable to national and international standards for measurement units and or international and certified reference materials. The calibration is generally a process of adjusting the output or indication of a measurement device to match the magnitude of the standard used in certain accuracy. The purpose of this paper is to find out the vickers hardness test calibration whether the machine running normally or there is a problem with the device. A case study was conducted in PT. Tenaris SPIJ, Cilegon, Indonesia. A vickers hardness testing in the case study has its own reference standard, namely ISO 6507-2: 2018 Metal material - Hardness Test Verification and Calibration of the test machine. The vickers hardness test equipment is a machine to conduct tests using a diamond pyramid with a plane angle of 136°, by means of an emphasis by an indentor that results in a trace or indentation on the surface of the test object. The vickers hardness testing is abbreviated as HV or HVN and also known as Diamond Pyramid Hardness Test (DPH). Result of calibration in the case study was found the repeatability value on vickers hardness testing machine of 32 HV 10 and the error value of ±3%.

This paper presents an experimental study of mass percentage and pretreatment effect of oil palm trunk (OPT), and peat charcoal on energy parameters of biomass pellet. The density, calorific value, moisture and ash content of OPT biomass pellet has been developed and the experimental conditions in obtaining the energy parameters of OPT biomass pellet are discussed. The physical pretreatment was carried out by finely chopping OPT, peat charcoal, and adhesive and mixed in a predetermined composition. The manufacturing process of OPT biomass pellet was performed, the mass percentage of OPT and peat charcoal were varied. Type of test was performed on biomass pellet include density, calorific value, moisture and ash content. The influences of various parameters on the characteristics of biomass pellet were considered. The increase of mass percentage and pretreatment of peat charcoal has an effect on increasing the density, decreasing the calorific value of OPT biomass pellet, increasing the moisture content, and increasing the ash content of OPT biomass pellet. The mixture of coconut shell charcoal decreasing the density, increasing the calorific value, decreasing the moisture content, and decreasing the ash content of OPT biomass pellet. Biomass pellets from a mixture of OPT and coconut shell charcoal has a calorific value of 6649 cal/g, where the density was 1.15 g/cm3, the moisture content of 5.6%, and the ash content of 8.9%.

Impression creep behavior of as-cast Mg-xSi alloys (x = 0.5, 0.8, 1.2 wt.%) was studied under shear modulus-normalized stress values ranging from 0.009 to 0.016 at temperatures between 398 and 491 K. The results show that creep properties of these alloys are improved with increasing Si content under all the applied loads and temperatures, and Mg-1.2Si alloy has minimum creep rate and thus maximum creep resistance. It is attributed to the higher volume fraction of Mg2Si, which can reduce grain boundary sliding during the creep test. Stress exponent of all the alloys is between 4.06 and 7.09 in the temperature range of 398 to 447 K. It is changed from the range of 3.

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