Analisis Pengaruh Media Pendingin Terhadap Kekerasan Baja S45C Pada Proses Hardening-Tempering

This study used an experimental method, in the form of the heat treatment hardening 930⁰C with the variations in the cooling media of the coconut water, table salt water, mineral waterwater, coolant radiator, and dromus water and variations in temperatures of tempering 200⁰C, 420⁰C, and 600⁰C, the specimens were cylindrical in diameter 25 mm and 20 mm in length, this study aims to determine the optimum hardness value of S45C steel specimens due to the heat treatment process hardening-tempering. From the results of the study, there is the effect of hardening 930⁰C there is the most optimal hardness value found in coconut water cooling media with the hardness level of 53.5 HRC. Under the influence of tempering 200⁰C there is the optimum hardness value found from the influence of mineral water cooling media with the hardness level of 50.7 HRC, while the influence of tempering 420⁰C there is the most optimal hardness value from the influence of mineral water cooling media with the hardness level of 41.8 HRC, and for tempering effect 600⁰C there is the most optimal hardness value available from the influence of the coconut water cooling media with the hardness level of 35.93 HRC.

PEMANFAATAN SERAT PELEPAH KELAPA SAWIT SEBAGAI BAHAN PEMBUATAN KAMPAS REM SEPEDA MOTOR

Brake pads are generally made of asbestos, which is less environmentally friendly and widely available in nature, therefore motorcycle brake pads are made that utilize palm frond fibers filled with alumina powder and bonded to a polyurethane matrix. This research was conducted at the Laboratory of Material Testing of Industrial Chemical Technology Polytechnic (PTKI) Medan. Research was carried out from February-July 2020, using two test, namely the Rockwell Hardness level test and the Pin On Disk Friction Coefficient test. The result showed that oil palm frond fibers can be made into motorcycle brake pads with the addition of alumina powder according to the predetermined composition. After going through the test, the Rockwell hardness level was obtained in A2 treatment (6% Alumina) with the highest and best hardness level, namely 52.75 Kg. And after testing the friction coefficient of the Pin On Disk type, brake pads from palm frounds with the addition of alumina powder composition which have the lowest coefficient value of the best are obtained in treatment A2 (6% Alumina) with a value of 0.000765 N/mm2. Keywords : biocomposite, brake shoes, palm fround fibers, alumina powder

Aplikasi Pre-Heating dan Edible Coating untuk Peningkatan Kualitas Keripik Kentang

This study aimed to improve the crispness and to reduce oil absorption in potato chips. Potato chips crispness was improved by applying pre-heating, namely boiling and steaming before frying, while oil absorption was reduced by adding acacia gum as an edible coating. Boiling and steaming was conducted at 100°C for 0, 2, 3, 4, 5, and 6 minutes. Acacia gum (0, 3, 4, 5, and 6%) and calcium chloride (0, 0.5, and 1%) were added in the formulation. Boiling for 4 minutes yielded hardness of 384.902±25.10 g, moisture content of 3.02±0.07%, crispness score of 5.04±0.60 (crispy), and overall hedonic score of 5.10±1.43 (somewhat like). Further process by adding acacia gum 5% and calcium chloride 1% yielded potato chips with fat content of 28.01±1.56%, oil absorption ratio of 0.32±0.03, moisture content of 1.07±0.78%, and hardness level of 411.111±25.32 g. The products recuded oil absorption during frying up to 41.81±5.86%.

Equal Channel Angular Pressing and Characterization of a Patented Eutectoid Fe-C Steel

Equal Channel Angular (ECAP) pressing has been showed as an attractive route to produce fine and ultrafine-grained metals and alloys with high strength and fracture toughness. ECAP is a simple process for applying severe plastic deformation (SPD) to metals that can be done with common laboratory equipments (mechanical tests machines) and an adequate die. In the present work, an eutectoid steel was processed by ECAP in a 120° die. Mechanical behavior of samples deformed by ECAP was compared to the same material processed by rolling. The hardness level obtained after a single pass of ECAP was comparable to an 84% reduction by rolling in a single pass. The hardness level obtained after 1 ECAP pass on a patented steel was higher than 4 ECAP passes on the same steel without patenting. The metallographic analysis showed intense alterations on the microstructure by the ECAP processing.

Hardness Analysis of Stone Breaker Chisel Made of Medium Carbon Steel as a Result of Hardening Using Water Cooling Media

Stone chisels produced by blacksmiths which are made using leaf spring steel are often too brittle or fragile so that when they are used, they often occur in the form of cracks and breaks. This study aims to determine the appropriate hardness level for stone chisels. The process is carried out by comparing the hardness level of stone chisels that have been used but still in good condition and those that have been damaged. Broken stone chisels have a high adequate hardness compared to good stone chisels so that damaged stone chisels can be reconditioned to get the right rock chisel hardness. Heat treatment is given to damaged stone chisels to improve the hardness level by normalizing the process to restore the initial mechanical properties of the steel and increasing the hardness of the chisel by heating the steel and then quenching it using water cooling media. Based on the experimental process carried out that the hardness level of a good stone chisel is between 228 HB to 320 HB by heating the duan spring steel to a temperature of 780ºC with a hold time of 10 minutes then cooling it quickly using water and stone chisels can break when it is used because it has a very high hardness.

KADAR AMILOSA, TINGKAT KEKERASAN, DAN SIFAT SENSORI STICK DENGAN SUBSTITUSI TEPUNG GADUNG (Dioscorea hispida Dennst)

Stick is one type of snack that is quite popular. The public's fondness for this stick makes it one of the most widely produced snack foods. The main raw material for stick making is wheat flour, where the import of wheat flour in Indonesia continues to increase. Therefore, the effort to reduce the need of wheat flour needs to be done, among others, by substituting wheat flour with local food products such as gadung flour from gadung tuber (Dioscorea hispida Dennst). Umbi gadung contains a high enough carbohydrate that is equal to 18%, for that gadung tuber potentially as a source of carbohydrates. However, on the other hand the gadung bulb contains HCN levels. To reduce the levels of HCN on the gadung tubers will be modified making of flour gadung using cabbage fermentation extract. The purpose of this research is to know the level of amylose, the hardness level and the sensori character and the best treatment stick with the substitution of gadung flour with variation of the addition of the flour of gadung as much as 0%, 10%, 20%, 30% and 40%. The result showed that there was no significant effect (p <0.05) on the amyloose substitution level and the stick hardness, while the sensory character showed no significant effect (p> 0,05) on the substitution stick of the gadung flour. The best result of this research is stick with substitution of flour of gadung with the formulation of 10% flour of gadung with result of amylose content 58,47%, hardness 0,61N, sensory 3,20 (like) and HCN level 37,45 ppm. Top 10% gadung stick criteria are yellow-brown, fragrant aroma, crispy texture and savory taste.

Modelling Surface Roughness in the Function of Torque When Drilling

Given the application of a multiple regression and artificial neural networks (ANNs), this paper describes development of models for predicting surface roughness, linking an arithmetic mean deviation of a surface roughness to a torque as an input variable, in the process of drilling enhancement steel EN 42CrMo4, thermally treated to the hardness level of 28 HRC, using cruciform blade twist drills made of high speed steel with hardness level of 64–68 HRC. The model was developed using process parameters (nominal diameters of twist drills, speed, feed, and angle of installation of work pieces) as input variables varied at three levels by Taguchi design of experiment and measured experimental data for a torque and arithmetic mean deviation of a surface roughness for different values of flank wear of twist drills. The comparative analysis of the models results and the experimental data, acquired for the inputs at the moment when a wear span reaches a limit value corresponding to a moment of the drills blunting, demonstrates that the neural network model gives better results than the results obtained in the application of multiple linear and nonlinear regression models.

Weed control by 2,4-D dimethylamine depends on mixture water hardness and adjuvant inclusion but not spray solution storage time

Herbicides are an important tool in managing weeds in turf and agricultural production. One of the earliest selective herbicides, 2,4-D, is a weak acid herbicide used to control broadleaf weeds. Water-quality parameters, such as pH and hardness, influence the efficacy of weak acid herbicides. Greenhouse experiments were conducted to evaluate how varying water hardness level, spray solution storage time, and adjuvant inclusion affected broadleaf weed control by 2,4-D dimethylamine. The first experiment evaluated a range of water-hardness levels (from 0 to 600 mg calcium carbonate [CaCO3] L−1) on efficacy of 2,4-D dimethylamine applied at 1.60 kg ae ha−1 for dandelion and horseweed control. A second experiment evaluated dandelion control from spray solutions prepared 0, 1, 4, 24, and 72 h before application. Dandelion and horseweed control by 2,4-D dimethylamine was reduced when the CaCO3 level in water was at least 422 or at least 390 mg L−1, respectively. Hard-water antagonism was overcome by the addition of 20 g L−1 ammonium sulfate (AMS) into the mixture. When AMS was included in spray mixtures, no differences were observed at 600 mg CaCO3 L−1, compared with distilled water. Spray solution storage time did not influence dandelion control, regardless of water-hardness level or adjuvant inclusion. To prevent antagonism, applicators should use a water-conditioning agent such as AMS when applying 2,4-D dimethylamine in hard water.