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This study analyzed the characteristics of carbon produced from coconut shells and Arabica coffee grounds through a pyrolysis process at a temperature of 1000°C for 1 hour. The SEM test results showed that coconut shells contained 91.87% carbon, while Arabica coffee grounds contained 74.39% carbon, indicating a higher carbon content in coconut shells. Furthermore, this study evaluated the effect of coconut shell carbon and Arabica coffee grounds carbon with temperature variations on the thermal conductivity and corrosion rate of 316L stainless steel plates. The results of the study showed that the highest thermal conductivity values ​​for coconut shell carbon and Arabica coffee grounds were 19.06087 W/m°C and 18.959905 W/m°C, respectively, both achieved at a temperature of 900°C. Increasing the temperature in the pack carburizing process significantly increased the carbon content in 316L stainless steel, which had a positive impact on increasing thermal conductivity. Coconut shell carbon at 900°C showed the lowest corrosion rate of 4.35 mm/year, while Arabica coffee grounds carbon at the same temperature had a corrosion rate of 5.81 mm/year. In conclusion, the effect of adding carbon with temperature variations in the pack carburizing process can increase hardness. The corrosion rate on 316L stainless steel plate will be lower because it contains Cr, Ni, and C which affect strength and high temperature resistance, especially hardness.

One of the promising renewable energy sources is biomass, particularly underutilized candlenut shells, which can be processed into briquettes as a superior alternative to charcoal. This study aimed to utilize candlenut shell waste for briquette production, evaluating hardness and calorific value under varying carbonization temperatures (400°C, 500°C, 600°C) and mesh sizes (30 and 100). Briquettes were produced via carbonization and compression. Hardness was measured using a durometer, yielding the highest value of 76.33 HA at 600°C and 100 mesh, and the lowest of 43.58 HA at 400°C and 30 mesh. Calorific value, determined by bomb calorimetry, peaked at 7834.70 cal/g for 500°C and 30 mesh, while the lowest was 5085.24 cal/g at 500°C and 100 mesh. These results demonstrate that optimized carbonization and particle size enhance briquette quality, promoting sustainable biomass utilization for energy applications.

ASTM A36 steel has relatively low hardness and corrosion resistance, making surface treatment necessary to improve its material properties. This study aims to determine the effect of temperature and holding time variations in the pack carburizing process on the hardness, corrosion rate, and microstructure of ASTM A36 steel. The pack carburizing process was carried out using coconut shell charcoal as the carburizing medium with temperature variations of 850°C, 900°C, and 950°C and holding times of 20, 40, and 60 minutes, followed by quenching in distilled water. Hardness testing was conducted using the Rockwell B scale (HRB) method, corrosion rate testing was performed according to the ASTM G31 method, and microstructural observations were carried out using Scanning Electron Microscopy (SEM). The results showed that increasing the temperature and holding time improved the hardness and corrosion resistance of ASTM A36 steel. The highest hardness value was obtained at a temperature of 950°C with a holding time of 60 minutes, reaching 114.1 HRB. Microstructural analysis revealed the formation of a martensitic phase on the specimen surface after the carburizing process.

The unavailability of intake and exhaust valves for 500 cm³ diesel engines manufactured in the 1980s has created difficulties in maintaining and operating agricultural tractors. This study aimed to manufacture replacement intake and exhaust valves using SUH 35 austenitic steel according to the original engine specifications. The production process included design preparation, material selection, raw material measurement, forging, machining, heat treatment, quality inspection, and packaging. SUH 35 steel rods measuring 12 mm in diameter and 105 mm in length were used as the raw material. Forging was performed to form the valve heads, producing exhaust valves with a diameter of 30 mm and thickness of 2 mm, and intake valves with a diameter of 35 mm and thickness of 2.5 mm. After machining, the final dimensions of the exhaust valve were 29.5 mm head diameter, 2 mm thickness, 105 mm length, and 7 mm stem diameter, while the intake valve measured 33.5 mm head diameter, 2.5 mm thickness, 105 mm length, and 7 mm stem diameter. Hardening treatment produced a hardness value of 40 HRC. The manufactured valves met the required dimensional and mechanical specifications. The production cost was IDR 100,000 per unit, with a processing time of approximately 60 minutes per unit. The results demonstrate that replacement valves for 500 cm³ diesel engines can be successfully reproduced, enabling the continued operation and maintenance of older tractor engines.

The problem in manual tractors lies in the rotor blades that are not wear-resistant and their dimensions are not up to standard. The purpose of fabrication is to obtain medium carbon steel manual tractor rotor blades measuring 220×80×8 mm. Fabrication methods include: standard blade design measuring 220 mm long, 80 mm wide, 8 mm thick, and 9 mm hole diameter, selection of used leaf spring steel type SUP9A measuring 500×90x10 mm, cutting used leaf springs, straightening used leaf springs, forging used leaf springs, drilling used leaf springs with a diameter of 9 mm, hardening at 850°C, tempering at 450°C, sharpening tractor rotary blades, finishing, product quality hardness testing. The fabrication results are in the form of a manual tractor rotary blade with dimensions of 220 × 80 × 8 mm from used SUP9A spring steel which is forged with a hardening hardness value of 55 HRC which is higher than the standard value of 50 HRC or 10% harder and the tempering results reach 45 HRC, the total production cost is IDR 80,000/unit and the processing duration is 130 minutes/unit which implies that the rotor blade is wear-resistant and has met the dimensional standards.

The brake system on a vehicle is an important component for driving safety, brake malfunction can cause danger and driving safety is disturbed to the point of failure which can cause serious accidents. The object of the study was chosen original brake discs and variation discs used for Yamaha Matic Mio motorbikes. in the general public it is better known as brake discs, Hardness testing was carried out using the Rockwell method with 10 pressure points on the braking friction area with an average value of the original disc with a value of 57 HRC, and the value of the variation disc with a value of 53 HRC with a slight difference of 4 HRC, Brinell hardness value and the original disc tensile test averaged 586 HBS and the average variation disc value was 501 HBS. while the conversion tensile test value from the Rockwell hardness test value on the original disc was 1645 N / mm² and the variation disc brake was 1597.2 N / mm² thus the Rockwell test value, Brinell conversion and the original disc tensile test were still greater than the variation disc tensile test value.

The need for metal materials in various industries and construction is increasing. Materials that are widely needed by industry, especially the use of current research for the manufacture of electrodes in the electrolysis process. Some of the mechanical properties that are highlighted in quality include strength and wear resistance of the material. To meet these needs, various engineering techniques such as surface coatings are carried out to improve its mechanical properties. One approach that has been introduced is to change the structure of the material using a mixture of natural carbon-based materials, such as coconut shells and Arabica coffee grounds. Coconut shells and Arabica coffee grounds can be processed into carbon through a pyrolysis process at a temperature of 1000°C. The carbon is used as a material for the pack carburizing process with various heating temperatures (700°C, 800°C, 900°C) and various types of coconut shell carbon and Arabica coffee grounds with a base material of 316L stainless steel and will later undergo a testing process that tests the microstructure and hardness. The results of the structural and hardness tests show changes in the structure of the specimen. The higher the temperature, the higher the carbon mass value and the hardness value. Coconut shell carbon specimens with a temperature of 900°C have an average of the highest hardness value of 318 HV and specimens with the lowest hardness value of 293 HV Arabica coffee grounds carbon specimens with a temperature of 700°C. The content of C, Cr, and Ni affects hardness, strength, and high temperature resistance.

His study aims to investigate the effect of temperature variation in pack carburizing and quenching processes on the microstructure and surface hardness of Stainless Steel 316L. The pack carburizing process was conducted using activated carbon derived from robusta coffee grounds at temperatures of 700°C, 800°C, and 900°C with a holding time of 60 minutes. Subsequently, a quenching process was carried out using oil mixed with activated carbon to lock the diffused carbon. The material was tested for mass change, microstructure (via SEM), and surface hardness (using the Vickers method). The results show that increasing temperature significantly affects carbon diffusion and hardness improvement. The highest hardness value was obtained from the quenching process at 900°C with 330 HV, while pack carburizing at the same temperature resulted in 292 HV. The microstructure revealed more dominant Martensitic formation in the quenching process. Therefore, heat treatment with rapid cooling proves to be more effective in enhancing hardness and modifying the microstructure of Stainless Steel 316L.    

Brake discs are one of the motorcycle spare parts that function to connect and reduce speed when the motorbike is moving, although very simple, this spare part is part of the braking system and has a very important role, without braking it will endanger the driver and other road users. To determine the hardness of the motorcycle brake disc on two original brake discs and variation brake discs on the Yamaha Vision sport motorbike by conducting Rockwell hardness tests on the original and variation brake discs with 10 test variable points. The results obtained for the average value at the level of hardness on the original disc sample are 55.1 HRC and the average value on the variation disc sample is 44.6 HRC, and the conversion hardness value from the Rockwell test. For Brinell testing and tensile testing from the results of Rockwell hardness testing, the average Brinell and tensile test values ​​were converted from the test site with the average Brinell conversion results for the original disc being 575 HBS, while the average variation disc value was 417.1 HBS, the conversion tensile test value with the results on the original disc was 1626 N/mm² and the variation disc was 1427 N/mm² with 10 variable point Rockwell testing and the conversion value of the Brinell hardness test and the original disc tensile test value was still greater than the variation disc tensile test value.

Mochi is a cake made from glutinous rice flour with other ingredients and then steamed. White sweet potato flour is used as a substitute because it contains high levels of fiber, with the addition of elephant ginger extract, which is expected to be able to neutralize the unpleasant taste and scent of white sweet potato flour. The aim of this study was to determine the right formulation in order to obtain white sweet potato flour substitution mochi and a high concentration of elephant ginger extract. This study used a completely randomized design (CRD), which consisted of two factors, namely the concentration of glutinous rice flour and white sweet potato flour (90:10, 80:20, and 70:30) and the percentage of elephant ginger extract (to 100 ml of water) (1.5%, 3%, and 4.5%). The best results of the chemical analysis were white sweet potato flour 30 g and ginger extract 4.5%, with a moisture content of 23.66%, an ash content of 0.25%, a total sugar content of 7.64%, and fiber of 2.60%. Based on the results of the physical analysis, the colour L*47.62 (bright brown), a* -4.68 (slightly green), b* 12.20 (yellowish) and a hardness value of 8.90 N, gumminess of 6.27 N, chewiness of 1.73 N, cohesiveness of 0.71 N, and adhesiveness of 1.17 N. Mochi with white sweet potato flour substitution and concentration of elephant ginger extract can be a nutritions food and a source of fiber.

This study aims to determine the effect of varying hybrid composite volume fractions of luffa (Luffa cylindrica) fiber and fiberglass on the tensile strength of the material. The composite matrix used was polyester resin, while the reinforcements consisted of luffa fibers treated with 5% KOH alkaline solution to improve adhesion with the matrix, and fiberglass as an additional strengthening material. The composition variations applied in this research were 90%:5%:5%, 85%:7.5%:7.5%, and 80%:10%:10% (polyester resin : luffa fiber : fiberglass). The fabrication process was carried out using the hand lay-up method, which is widely used for producing layered composites, followed by tensile testing according to standard mechanical testing procedures to evaluate tensile strength and elongation. The results showed that the addition of luffa fiber and fiberglass fractions had a significant influence on the mechanical properties of the composites. The 80%:10%:10% variation demonstrated the highest tensile strength value of 13.65 MPa and the highest elongation of 0.0105%, indicating better mechanical performance compared to other variations. These findings confirm that the hybridization of natural luffa fiber and synthetic fiberglass can work synergistically to improve the tensile strength of the composite. However, higher fiber fractions should be considered carefully, as they may affect the homogeneity of the mixture and the quality of interfacial bonding. Further research is recommended to optimize volume fractions, enhance fiber surface treatments, and evaluate additional mechanical properties such as impact strength and hardness, in order to explore the potential of hybrid composites as eco-friendly materials with promising mechanical performance.

This study investigates the corrosion inhibition potential of a newly synthesized organic compound, (E)-4-hydroxy-3-(phenylamino)pent-3-en-2-one (LASA3), using computational chemistry approaches. Density Functional Theory (DFT) calculations were performed at the B3LYP/6-31G(d) level of theory with the Gaussian09 software package to evaluate several key quantum chemical parameters. These parameters include total energy, the energies of the highest occupied molecular orbital (EHOMO) and lowest unoccupied molecular orbital (ELUMO), the energy gap (ΔEgap), dipole moment, chemical hardness, softness (σ), and the number of electrons transferred (ΔN). The computational results reveal that LASA3 exhibits a higher EHOMO value and a smaller ΔEgap compared to its precursor molecules, referred to as S.M.1 and S.M.2. A higher EHOMO value suggests that LASA3 has a greater electron-donating ability, which enhances its interaction with the metal surface. Likewise, the reduced ΔEgap indicates greater chemical reactivity and a higher likelihood of forming stable coordination bonds with iron atoms on the carbon steel surface. Electrostatic potential (ESP) map analysis further supports these findings by highlighting the distribution of electron density within the LASA3 molecule. The ESP maps show significant electron-rich regions localized around nitrogen and oxygen atoms, which are potential active sites for adsorption onto the steel surface. This adsorption process plays a crucial role in blocking active corrosion sites and reducing the rate of metal degradation. In conclusion, the theoretical analysis confirms that LASA3 has superior electronic properties for corrosion inhibition compared to its starting materials, S.M.1 and S.M.2. Its ability to donate electrons, favorable dipole characteristics, and strategically located electron-rich sites make it a promising candidate for further experimental evaluation as an efficient corrosion inhibitor for carbon steel applications.  

Along with the times, the availability of fossil energy is decreasing, especially natural gas and coal, before using fossil energy, humans have used biomass as an energy source. Indonesia has many plantation commodities, one of which is coffee which is the fourth largest coffee producer in the world. Coffee grounds are the main waste produced by coffee shops and are usually only thrown away. The main ingredients in this study were arabica coffee grounds and robusta. By using robusta composition 60% arabica 40%, robusta 50% arabica 50% robusta 40% arabica 60%. In addition, briquettes are tested for hardness by making points on the surface of the briquettes using a durometer shore A tool of 30 points, then a calorimeter bomb test is carried out to obtain the calorific value content. The result obtained from the highest hardness value is briquettes with a robusta mixture of 50% arabica 50% with a value of 23.7 HA, while the highest calorific value is found in a robusta mixture of 60% arabica 40% with a value of 4526.85 cal / gram.

The selection of coffee wood in this study is based on the fact that coffee wood is waste and has not been utilized optimally and the availability of coffee wood is large and easy to obtain in the East Java region. Coffee wood is a type of wood that is not in demand by many people because this wood is relatively small and not straight. To reduce waste, researchers made briquettes made from coffee wood using mesh 30 and 250 with variations in drying temperatures (60 °C, 80 ° C and 100 ° C). After that was carried out Calorimeter Bomb Testing, and hardness. The highest calorific value resulting from temperature variations of 60°C, 80°C, and 100°C mesh 30 and 250 drying coffee wood briquettes is mesh 30 temperature 100°C of 6972.23 cal/g, and mesh 250 temperature 100°C of 6763.19 cal/g. The effect of the ratio of temperature variations (60°C, 80°C and 100°C) mesh 30 and 250 Drying coffee wood briquettes is: Grain and adhesive size. The smaller the grain size on the briquettes, namely mesh 250, it produces a high hardness value of 60 °C of 26.6 HA, a temperature of 80 °C of 27.7 HA, and a temperature of 100 ° C of 27.4 HA, the larger the grain size in the briquette, namely mesh 30, the low hardness value of 60 ° C of 25.6 HA, temperature of 80 ° C of 26.4 HA, and a temperature of 100°C of 26.2 HA.  The effect of the adhesive is that when drying the oven for 3 hours with temperature variations (60 ° C, 80 ° C and 100 ° C) makes the adhesive react so that the adhesive evaporates and coagulates which causes the hardness value to rise and fall.

Through this research there are two variables observed, namely the effect of variations in briquette charcoal pressure and specific heat value on the composition of carbonisation of hazelnut shell charcoal with tapioca adhesive on specific heat value. The initial process of research in the form of making charcoal on hazelnut shell briquettes, hazelnut shells are carbonised at 500 °, sieved with mesh 30 and 100 sieves, given a compressive load of 3 kg, 4 kg, 5 kg and 5.5 kg, the adhesive on hazelnut shell briquettes is starch and drying is carried out with a drying oven for 3 hours at a temperature of 80 °. The purpose of this study was to determine the effect of variations in pressure and particle size on the quality of hazelnut shell briquettes when viewed from the combustion rate and calorific value. The methodology used in the research is by using hazelnut shell briquette experiments, hazelnut shell briquette testing includes testing through hardness and briquette calorimeter bomb value. Through the research, it was found that the highest calorific value was in the 4 kg pressure specimen on mesh 30, namely 9221.09 cal/gram while the lowest combustion rate was produced by the hazelnut shell briquette specimen with a pressure of 5 kg and 5.5 kg, which was 4076.17 g/min. Giving different compressive loads and mesh sieves can provide advantages to briquettes including increasing specific calorific value, reducing water content and slowing the combustion rate

Compressive strength is one of the mechanical properties of rock behavior. This study focuses on the Balikpapan and Kampungbaru Formations located in the Kutai Kartanegara area, East Kalimantan. The Schmidt Hammer testing method was applied due to the lack of previous studies utilizing this tool to evaluate rock hardness in correlation with compressive strength. The research site is situated in the Kutai Kartanegara area, specifically in the districts of Muara Badak, Muara Jawa, and Sanga-Sanga. Field observations revealed the presence of claystone slopes at predetermined locations. Based on the test results, the uniaxial compressive strength (UCS) values for the Balikpapan Formation range from 3.453 MPa to 5.454 MPa, while the Kampungbaru Formation ranges from 3.317 MPa to 8.571 MPa. The Schmidt Hammer rebound number (RN) values for the Balikpapan Formation range from 17 to 19.6, and for the Kampungbaru Formation from 15 to 23.7. A negative correlation was found between the rebound number and UCS, where higher RN values tend to correspond with lower UCS values. This is supported by the linear regression analysis showing a negative coefficient (-0.450).  

The manufacturing industry continues to develop quality to improve productivity and business sustainability. One method commonly used in metal surface treatment is the anodizing process. One of these industries is the electroplating industry which uses chemicals as aluminum dyes that damage the environment. The purpose of this study is to determine the effect of using natural dyes turmeric, dragon fruit, and pandan leaves as coloring materials in the anodizing process of bicycle components on their hardness. The specimen used in this study is 1100 aluminum. The results showed that the highest hardness value using dragon fruit natural dye was 204.775 VHN.

Leaf springs are one of the suspension systems that are still widely used in various modes of transport such as cars and trucks. The spring functions to support the load and reduce vibration from operational activities. This study aims to analyse the bending strength and hardness of steel leaf springs of trucks and cars resulting from tempering heat treatment. The three point bending method was used as the flexural strength testing method and the Rockwell C Hardness method testing was used for hardness testing with leaf springs in raw, tempered 460°C, and tempered 510°C conditions. From the results of the study, the highest average bending strength value of 3733,55 MPa was obtained and an average roughness value of 31,8 HR was obtained for the 510°C tempered truck leaf springs. This also applies to the 510°C tempered car leaf springs, where the average bending strength value obtained is 3392,65 MPa and the average hardness value obtained is 29,5 HR. Thus, it is recommended that tempering heat treatment that can be applied to truck and car leaf springs be carried out at 510°C to increase the bending strength and ductility of the leaf springs.

Yangko cake is a semi-wet food made from glutinous rice flour with the addition of a sugar solution. In order to improve the characteristics of the yangko cake, an ingredient is added, namely kidney bean flour and cinnamon extract. Kidney beans are one type of legume that has a high protein source so it can add nutritional value to food products. Kidney bean has an unpleasant taste, therefore it needs to be balanced with the addition of cinnamon extract, which is expected to reduce the unpleasant flavor of the yangko cake which consumers preferred. The experimental design used is a CRD, with the first factor being the ratio of glutinous rice flour and kidney bean flour with a ratio of 90:10, 80:20, and 70:30. The addition of cinnamon extract in various amounts (2 ml, 4 ml, and 6 ml) was the second element. The inclusion of substitute glutinous rice flour and kidney bean flour, coupled with the variation of cinnamon extract produced yangko cake with 3,80% fiber content and 5,76% protein content.  Chemically, physically and organoleptically, the best product from several formulations of the yangko cake was with 70:30 of glutinous rice flour to kidney bean flour and 6 ml of cinnamon extract, with 47.98% water content, 0.66% as content, 31,36% total sugar content and with a hardness of 28.82 N, a gumminess of 4.92 N, a chewiness of 2.28 N then a cohesiveness of 0.64 Ns.  The organoleptic characteristic of the yangko cake was the most preferred by the panelists, with a value of 3,76 (preferred). The yangko cake substitusion of glutinous rice flour and kidney beans with the addition of cinnamon extract is a food ingredient  that has quite high protein and fiber.

A pressure vessel is a closed container that stores pressurized liquids or gases. Low-carbon steel is used as a material for pressure vessels that operate at low to moderate temperatures. One of the important aspects of manufacturing pressure vessels is the welding process. The welded area tends to be the weakest point due to exposure to high heat, which can lead to greater residual stress and potentially cause cracking. This study aims to evaluate the effect of variation in ample angle and current strength on mechanical properties, especially tensile strength, and hardness, to determine the optimal amplitude angle and current strength. The research method applied is an experiment by conducting SMAW welding on SS400 steel using E7016 electrodes, with a single V ample angle variation of 55°, 60°, 65°, and strong welding current of 110 A, 120 A, and 130 A, then a tensile test and hardness test are carried out. The results show that the tensile strength of the raw material is 481.2  with a hardness of 191.95 HVN. For the variation of the amputation angle, the highest tensile strength value was recorded at an angle of 55°, which was 567.471 N/mm2 , while the lowest was at an angle of 65°, which was 559.997 N/mm2 . The highest hardness value at a 65° angle reached 328.422 HVN, while the lowest at a 55° angle was 312.878 HVN. In terms of current strength variation, the highest tensile strength is obtained at 130 A which is 568.421 N/mm2 and the lowest at 110 A is 552.339 N/mm2 . The highest hardness value is found at a current strength of 110 A, which is 343.411 HVN, and the lowest at a current strength of 130 A, which is 295.122 HVN. The optimal parameters were found at a yield angle of 55° with a tensile strength of 567.471 N/mm2 and a hardness of 312.8 HVN and a current strength of 130 A with a tensile strength of 568.421 N/mm2 and a hardness of 295.1 HVN.