Wear of Dry Sliding Al 6061-T6 Alloy Under Different Loading Conditions

In the present work, wear of Al 6061-T6 alloy under different normal loads, sliding speeds and temperatures was investigated. Pin on disk type tribometer was used to conduct dry sliding experiments. Different load combinations comprising of normal loads (1 kg, 1.5 kg and 2 kg), sliding speeds (1.25 m/s, 2 m/s and 3 m/s) and temperatures (room temperature (31 ± 1 °C), 60 °C, 100 °C and 150 °C) were applied during dry sliding experiments. Adhesive and abrasive wear mechanisms were observed in dry sliding of Al 6061-T6 alloy contacts from the microscopic analysis of worn contact surfaces. The wear rate was more influenced by increase in normal load than increase in sliding speed and temperature. Under normal loads of 1 kg and 1.5 kg, Al 6061-T6 alloy showed better wear resistance at higher temperatures when compared to that at room temperature.

ANALISIS MODAL DAN HARMONIK SEBUAH RANCANGAN FIXTURE UJI VIBRASI UNIVERSAL MENGGUNAKAN METODE ELEMEN HINGGA

Fixture uji vibrasi harus dapat memegang device under test (DUT) selama proses pengujian dan sesuai dengan kondisi aslinya. Umumnya fixture uji vibrasi yang dibuat harus sesuai dengan geometri DUT. Oleh karena fixture uji vibrasi dibuat secara khusus untuk DUT tertentu, maka hal ini membuat proses uji vibrasi menjadi panjang alurnya dan lama pelaksanaannya. Selain itu, hal tersebut juga menyebabkan tingginya biaya untuk pembuatan fixture baru. Salah satu solusi dari masalah ini adalah dengan membuat fixture uji vibrasi yang bersifat universal. Fixture uji vibrasi yang bersifat universal dirancang mampu digunakan untuk hampir semua bentuk DUT. Fixture tersebut akan digunakan pada pengujian kategori S standar DO-160G section vibrasi yang memiliki rentang pengujian 5-500 Hz sehingga harus memiliki frekuensi natural di atas 500 Hz. Dalam studi ini dilakukan analisis sebuah rancangan fixture uji vibrasi yang bersifat universal mengunakan metode elemen hingga. Analisis dilakukan untuk fixture uji vibrasi universal berukuran 600 mm x 600 mm menggunakan metode analisis modal dan harmonik pada rentang frekuensi 5 Hz - 2000 Hz, kemudian dilakukan analisis kemampuan aktual sistem uji vibrasi berdasarkan massa fixture. Dua jenis material yaitu paduan aluminium dan paduan magnesium digunakan dalam studi ini. Hasil studi menunjukkan bahwa performa fixture yang menggunakan material Al 6061 tidak jauh berbeda dengan material Mg. Frekuensi natural yang diperoleh untuk fixture bermaterial Al 6061 adalah 975.94 Hz sedangkan untuk material paduan Mg adalah 996.88 Hz dengan selisih sebesar 2.14%, keduanya memenuhi kebutuhan pengujian vibrasi DO-160G kategori S. Analisis harmonik menghasilkan perbedaan amplitudo respon yang tidak signifikan yaitu di bawah 0.6‰. Fixture bermaterial logam paduan Mg lebih ringan daripada material Al 6061 sehingga menghasilkan kemampuan aktual sistem uji vibrasi yang lebih tinggi. Logam paduan Mg dipilih menjadi kandidat utama material fixture uji vibrasi universal yang akan dimanufaktur karena mampu menghasilkan kemampuan aktual sistem uji vibrasi yang lebih tinggi.

Investigation of microstructure and mechanical characteristic of underwater friction stir welding for Aluminum 6061 alloy – Silicon carbide (SiC) metal matrix composite

Demand for metal matrix composites (MMCs) is expected to increase in these applications, such as ‎in the aerospace and automotive sectors. Adequate joining techniques, which are important for ‎structural materials, have not yet been developed for Metal Matrix Composite (MMCs), however. ‎This work aimed to demonstrate the feasibility of ‎friction stir welding (FSW) and ‎underwater friction stir welding (UFSW) for joining Al 6061/5, Al 6061/10, and Al ‎‎6061/18 wt. %SiC composites have been produced by utilizing reinforce stir casting technique. Two ‎rotational ‎speeds,1000and 1800 rpm, and traverse speed 10mm \ min were examined. Specimen ‎composite plates 10 mm thick have been successfully welded by FSW. For FSW and UFSW, a tool ‎made of high-speed steel (HSS) with a conical pin shape was used. The result revealed that the ‎ultimate tensile strength of the welded joint by FSW and UFSW at rotation speed 1800 rpm for (Al ‎‎6061/18 wt. ‎‎% SiC composites) was 195 MPa and 230 MPa respectively. The ultimate ‎tensile ‎strength of the welded joint by FSW and UFSW (Al 6061/18 wt.% SiCe composites) was 165 MPa ‎and 180 MPa at rotation speed ‎‎1000 rpm respectively. The microstructural assessment showed that due ‎to larger grain sizes at FSW and UFSW, most of the fractures are located in the thermal ‎mechanically affected zone (TMAZ) adjacent to the weld nugget zone (WNZ). It is observed that in ‎failure, most of the joints show ductile features. As the volume fraction of SiC (18 wt.%) increases, ‎the friction stir welded and underwater friction stir welded efficiency decreases.

XFEM Simulation of Tensile and Fracture Behavior of Ultrafine-Grained Al 6061 Alloy

In the present work, the tensile and fracture behavior of ultra-fine grained (UFG) Al 6061 alloy was simulated using extended finite element method (XFEM). UFG Al 6061 alloy processed by cryorolling (CR) and accumulative roll bonding (ARB) was investigated in this work. Numerical simulations of two-dimensional and three-dimensional models were performed in “Abaqus 6.14” software using an elastic-plastic approach, and the results obtained were validated with the experimental results. The specimens corresponding to the three-point bend test, compact tension test with center crack, and double edge cracks were analyzed using XFEM (eXtended Finite Element Method) approach. In XFEM, the partition of unity (PU) was used to model a crack in the standard finite element mesh. The tensile and fracture properties obtained from the simulation were in tandem with the experimental data. UFG Al alloy showed higher tensile strength and fracture toughness compared to their bulk solution treated counterparts. Fracture toughness was measured in terms of stress intensity factor and J integral. In CR Al alloys, with increasing thickness reduction, an increase in stress intensity factor and a decrease in the J integral was observed. This behavior is attributed to the increase in strength and decrease in ductility of CR samples with increasing thickness reduction. In ARB Al alloys, the strength and ductility have increased with an increase in number of cycles. It also revealed an increase in both the stress intensity factor and J integral in ARB processed Al alloys with increase in number of cycles, as evident from XFEM simulation results.

Influence of Contact Area on Tribo Response of Al 6061 in Ambient and Vacuum Environment

Aluminium alloys are used in spacecraft and aerospace industries because of their unique properties which are lightweight and high strength. The components of aluminium alloys used in aerospace and space environment are subjected to relative motion which results in the tribo-phenomenon. The designer needs tribo response data for designing components geometrical dimensions. The literature reports inadequate tribo response data, more particularly in a vacuum environment (adverse environment). In the present investigation, experiments were conducted using Al 6061 aluminium alloy pins with different diameters. The cylindrical pin diameters were 2mm, 4mm and 6 mm. The cylindrical pins were slid against a hardened En-8 steel disc. The normal pressure was maintained at 0.625 MPa and the sliding speed was 0.5 ms-1. The estimated friction coefficient from monitored frictional force and normal force and the dependency of estimated friction coefficient on sliding distance for cylindrical pins of different diameters were analysed.

Wear Dry Behavior of the Al-6061-Al2O3 Composite Synthesized by Mechanical Alloying

The present research deals with the comparative wear behavior of a mechanically milled Al-6061 alloy and the same alloy reinforced with 5 wt.% of Al2O3 nanoparticles (Al-6061-Al2O3) under different dry sliding conditions. For this purpose, an aluminum-silicon-based material was synthesized by high-energy mechanical alloying, cold consolidated, and sintered under pressureless and vacuum conditions. The mechanical behavior was evaluated by sliding wear and microhardness tests. The structural characterization was carried out by X-ray diffraction and scanning electron microscopy. Results showed a clear wear resistance improvement in the aluminum matrix composite (Al-6061-Al2O3) in comparison with the Al-6061 alloy since nanoparticles act as a third hard body against wear. This behavior is attributed to the significant increment in hardness on the reinforced material, whose strengthening mechanisms mainly lie in a nanometric size and homogeneous dispersion of particles offering an effective load transfer from the matrix to the reinforcement. Discussion of the wear performance was in terms of a protective thin film oxide formation, where protective behavior decreases as a function of the sliding speed.