Agus Suprihanto

Dissimilar welding between copper (Cu) and stainless steel 316L (SS316L) is essential for heat pipe applications that require high thermal conductivity combined with adequate mechanical integrity. However, the large mismatch in thermal and metallurgical properties between Cu and SS316L...

The effect of the mass fraction of coal fly ash and gravel on the mechanical properties of mineral cast has been investigated. The percentage mass fraction variations of fly ash/gravel were 100/0, 75/25, 50/50, 25/75, and 0/100. This study used epoxy resin as the matrix; the mass fraction of epoxy resin in composite is about 15–25 %. The components of the mineral cast were mixed using conventional concrete mixers and then poured into cast steel molds. The specimens for tensile, bending, impact, and damping ratio tests were made from 160×40×10 mm mineral cast blocks and cut by water jet cutting. The tensile, three-point bending and impact tests were carried out according to ASTM D638, ASTM D790, and ASTM E23, respectively. The compression test specimen o was produced by pouring the compound of mineral cast in the cylinder steel molds with 75 mm diameter and 150 mm height, according to the ASTM C39 standard. The density of mineral cast composites was measured based on Archimedes' law. The results show that the density of the mineral cast composites decreases as the percentage of epoxy resin increases. The lowest density is 1.80 g/cm3 on mineral cast with 100 % gravel and 25 % wt. epoxy resin. The higher percent mass of epoxy resin increases compressive, tensile, and flexural strength. The mineral cast composite with 100 % gravel and 25 % wt. epoxy resin results in the highest compressive strength. The trend indicates that the rise of fly ash composition decreases the compressive strength value of the mineral cast. Increasing % wt. fly ash insignificantly increases the tensile and flexural strength. The minerals cast have a damping ratio of about 0.0241–0.044, which is higher than the damping ratio of cast iron. The research shows that mineral cast composite made from fly ash and gravel reinforced with epoxy resin can be applied as a material for the machine tool bed

This study aims to investigate the mechanical properties of bamboo apus (gigantochloa apus) as a natural reinforced composite material. Bamboo’s laminates of gigantochloa apus were used as reinforcement on the epoxy resin matrix. The parameters examined in this study are the configuration of lamina and compaction pressure. Laminate configuration varies in the number, thickness and direction of the lamina. Compaction pressures of 1.5 MPa, 2 MPa, and 2.5 MPa were used to fabricate the Laminated Bamboo Composites (LBCs). The stem of bamboo with a length of 400 mm was split to obtain bamboo lamina with a size of 400×20 mm. The thickness of bamboo lamina is varied between 1 mm, 1.5 mm, and 2 mm. The bamboo lamina is then preserved by watering it with a preservative solution in the form of 2.5 % sodium tetraborate solution and dried in an oven until the water content reaches 10 %. LBCs were made with a hand lay-up method. After the LBCs were molded, they were pressed with 3 variations of dies compaction 1.5 MPa, 2 MPa and 2.5 MPa. The tensile and bending tests were carried out on the LBCs. Tensile testing is performed in accordance with ASTM standard D3039 and the bending tests were conducted based on ASTM standard D7264. The results show that at each compaction pressure, the highest tensile and bending strength was achieved by LBCs with a thickness of 1 mm of bamboo lamina and 7 layers of bamboo laminates. The LBC with thinner bamboo lamina reinforcement and more layers has the highest tensile strength and bending strength, even it has a lower mass fraction. The LBCs with laminates oriented 0° exhibited greater tensile and bending strengths than the LBCs with laminates structured –45°/+45° and 0°/90°. The LBCs with the 0° laminates direction is matrix fracture followed by lamina fracture. In the 0°/90° direction, matrix fracture is followed by delamination in the 90° and 0° laminates direction. Delamination and lamina clefting were observed in LBCs with laminates oriented +45°/–45°.

Korosi terjadi tanpa mengenal waktu di segala aspek kehidupan manusia dan dapat mengakibatkan banyak kerugian. Di industri minyak dan gas, kerugian yang terjadi akibat korosi berdampak pada penurunan kualitas material yang digunakan. Dua hal ini berarti berhubungan dengan lamanya operasional alat berfungsi atau kemampuan jangka panjang dari suatu alat dan kemungkinan terjadinya kegagalan pada peralatan yang digunakan. Sehingga jika korosi menyerang, maka selain kerugian finansial yang dialami. Sehingga jika korosi menyerang maka selain kerugian finansial yang dialami, kerugain juga berdampak terhadap lingkungan sekitar dan juga safety dari pekerja dan masyarakat sekitar juga bisa terjadi. Oleh karena itu inspeksi terhadap peralatan yang ada penting untuk dilakukan. Indonesia yang masih mengacu pada inspeksi berdasarkan jangka waktu (time based inspection) masih memberikan peluang untuk terjadinya kegagalan pada peralatan yang digunakan. Oleh karena itu penting untuk menggunakan acuan lain seperti inspeksi berdasarkan tingkat risiko (Risk-Based Inspection)/RBI.Hasil penelitian menunjukan bahwa dari pipeline yang dianalisa yakni berdiameter 14” dengan lama penggunaan 8 tahun memiliki nilai 1C yang berarti berstatus risiko low medium dan mendapatkan respon corrective maintenance. Usulan inspeksi yang dapat dilakukan adalah pemeriksaan visual, ultrasonic straight beam, eddy current, flux leakage, radiography, dan pengukuran dimensi. Usulan waktu inspeksi yang dapat dilakukan kembali adalah 3 tahun kemudian. Nilai rendah yang diperoleh melalui penelitian ini dikarenakan pipa memiliki system inspeksi yang baik sehingga nilai TMSF tidak mengalami pertambahan yang signifikan

High temperature gas nitriding (HTGN) is the new methods to enhanced the properties of stainless steel. The HTGN process is able to diffuse the nitrogen atom into stainless steel. Increasing the nitrogen concentration produces higher corrosion resistance. Stainless steel for implant and medical devices such as 316L and 316LVM not only have to high corrosion resistance but also have to magnetic properties stabilities. Evaluation of corrosion and magnetic properties for austenitic stainless steel 316L and 316LVM after HTGN treatments was succesfully done. The corrosion resistance not only significantly increases but the stability of austenite phase is also increases. Therefore HTGN treatments is suitabe for improving the corrosion resistance for 316L and 316LVM which used as implant material.