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Journal : Otopro

Pengaruh Penambahan Stophole Pada Bahan Komposit Epoxy Serat Kaca Heryanto B. Soemardi; Kasijanto Kasijanto; Sadar Wahjudi; Nurlia P. Sari
Otopro Vol 13 No 2 Mei 2018
Publisher : Jurusan Teknik Mesin Universitas Negeri Surabaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26740/otopro.v13n2.p54-57

Abstract

Telah banyak diteliti metode stophole untuk menghambat pertumbuhan retak pada bahan logam, namun belum ada penelitian tentang metode stophole ini untuk menghambat retak pada bahan komposit. Penelitian ini mengguankan komposit epoxy dan serat kaca dengan katalis epoxy hardener (polyaminoamide), arah serat yang digunakan adalah serat acak, lapisan komposit terdiri dari 4 lapis,  dengan komposisi 30% serat, 69.7% resin, dan 0,3% katalis digunakan. Spesimen uji menggunakan CTS sesuai standar pengujian ASTM E 647 dengan retak awal sepanjang 20 mm dengan variasi diameter lubang stophole 2mm, 3mm, 4mm, dan 5mm serta jarak lubang dan retak 5mm, 10mm, dan 15mm. Hasilnya didapatkan jarak lubang yang paling optimum yang menyebabkan tegangan tarik tertinggi terletak pada jarak 10mm dari ujung retak, dan diameter optimumnya adalah 5mm dengan kekuatan tarik maksimum 22.74 Mpa, lebih tinggi daripada kekuatan tarik maksimum tanpa stophole (13.3 Mpa). Sehingga dapat disimpulkan adanya variasi stophole mempengaruhi tegangan tarik maksimum komposit epoxi serat gelas, karena pada ujung retak dan sisi lubang terdapat pemusatan tegangan, dan juga perbedaan mode patahan.
DOPING GRAPHENE OKSIDA MENGGUNAKAN BORIC ACID (H2BO3) UNTUK MENINGKATKAN KINERJA COIN CELL SUPERKAPASITOR Nurlia Sari; Andita Ganda
Otopro Vol 16 No 1 Nov 2020
Publisher : Jurusan Teknik Mesin Universitas Negeri Surabaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26740/otopro.v16n1.p7-11

Abstract

Boron doped in graphene oxide is a convincing method for modifying the properties of electrons in supercapacitors. In this study, we compared the performance of graphene electrode supercapacitor coin cells and boron-doped graphene. Graphene oxide was made by the modified Hummers method, followed by the boron-doped process by adding boric acid chemicals then continued with the pyrolysis process in the argon and hydrogen atmosphere at high temperatures. The precursors then used as electrodes (anodes and cathodes) in supercapacitor coin cells. The results show that the addition of boron dopants to graphene results in lower electrolyte absorption at the beginning of the test, causing the specific capacity at the beginning tends to be low but more stable, whereas at the end of the test the specific capacity of boron dopants tends to be higher than graphene without dopants. The addition of Boron Dopants to Graphene is effective in its application in supercapacitor coin cells making it promising in future energy storage needs.
PENGARUH JUMLAH DAN ARAH SAYATAN TERHADAP HASIL MILLING ALUMINIUM Nurlia Sari; Akhmad Faizin; Muhammad Fakhruddin; Agus Dani
Otopro Vol 19 No 1 Nov 2023
Publisher : Jurusan Teknik Mesin Universitas Negeri Surabaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26740/otopro.v19n1.p40-44

Abstract

The quality of production goods, especially milling on aluminum material, is considered good if it is characterized by good surface quality of the components and efficient (short) machining time. There are various factors that affect this. This study investigated the CNC milling machining parameters, namely depth of cut and step over, which were written as the influence of the number and direction of cuts on the surface quality and machining time of aluminum materials. The purpose was to obtain the appropriate parameters so that the machining process is more efficient and with the appropriate quality. The CNC milling used was CNC Dahlih with a 6mm diameter tool, feed rate of 460 mm/min, and rotational speed of 2800 RPM. The variables were vertical cutting direction (depth of cut 5mm) with variations in step over of 0.5 mm, 1 mm, and 2 mm, and horizontal cutting direction (step over 5mm) with variations in depth of cut of 0.5mm, 1mm, and 2mm. So that the number of cuts can be equalized to 4, 6, and 12 in the vertical and horizontal cutting directions. The results showed that the more cuts, the lower the surface roughness, but it increased the machining time.