Repairing cracked aluminum plates by aluminum patch using diffusion method

Sobhan Dehghanpour,Alireza Nezamabadi,Mohammad Mahdi Attar,Farzan Barati,Mehdi Tajdari 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.10

The aim of this work is to scrutinize the importance of diffusion bonding temperature, pressure and time on the repair of a cracked aluminum plate while the maximum tensile strength under a quasi-static loading has been investigated. The diffusion method was used to connect aluminum patches to repair the central and mode I cracks in thin aluminum plates. Here, the process of repairing cracked pieces made of aluminum or aluminum alloys involved a chemical and mechanical step to remove aluminum oxide and press the patch and piece under the temperature difference at a certain time. The repaired pieces underwent a quasi-static tensile loading while the maximum tolerable amount of force was obtained in different situations. Having assigned five temperatures, 300, 400, 500, 550 and 600 ° C, as well as four test times 30, 60, 120 and 180 min and five different pressures 10, 20, 50, 80 and 110 bar, we utilized fractional factorial design approach to perform 40 tests while there was seen a 10 mm initial crack in repaired samples . Experimental results showed that the optimum connection was resulted at 550 °C and the pressure of 80 bars within 120 min where the maximum force tolerated by the repaired vs. the unrepaired piece increased by 92 %. Therefore, having weighed the repair method using the diffusion bonding, we suggest that this type of the repair method can be a proper and cheap alternative to composite and adhesive patches.

Microstructural and Mechanical Behavior of Al6061-Graphene Oxide Nanocomposites

Mahdi Hedayatian,Khodadad Vahedi,Alireza Nezamabadi,Amir Momeni 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.6

In this paper, the mechanical properties and microstructure of Al6061-graphene oxide (GO) nanocomposites material, producedby stir casting and hot rolling process have been investigated. In order to make composite samples, GO nanoplateswith various weight percents of 0.2, 0.5 and 0.8% were added to the molten Al6061 through the stir casting process. Thenthe cast composite slabs were hot rolled at 530 °C. Tensile and hardness tests were used to study the mechanical propertiesof nanocomposite specimens. The microstructures of samples were examined by optical and scanning electron microscopes. The scanning electron microscope images and energy dispersive spectroscopy map analyses showed that the GO nanoplateshave been uniformly distributed within the Al matrix. The mechanical test results showed considerable improvements inthe hardness (by 41%), yield strength (by 43%), tensile strength (by 38%), ductility (by 58%) and toughness (by 116%) ofthe composite samples with respect to the base alloy. Studying the fracture surface also showed that ductile fracture is thedominant mechanism of fracture in all the specimens.

A fracture mechanics simulation of the pre-holed concrete Brazilian discs

Vahab Sarfarazi,Hadi Haeri,Alireza Bagher Shemirani,Maryam Firoozi Nezamabadi 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.3

Brazilian disc test is one of the most widely used experiments in the literature of geo-mechanics. In this work, the pre-holed concrete Brazilian disc specimens are numerically modelled by a two-dimensional discrete element approach. The cracks initiations, propagations and coalescences in the numerically simulated Brazilian discs (each containing a single cylindrical hole and or multiple holes) are studied. The pre-holed Brazilian discs are numerically tested under Brazilian test conditions. The single-holed Brazilian discs with different ratios of the diameter of the holes to that of the disc radius are modelled first. The breakage load in the ring type disc specimens containing an internal hole with varying diameters is measured and the crack propagation mechanism around the wall of the ring is investigated. The crack propagation and coalescence mechanisms are also studied for the case of multi-holes' concrete Brazilian discs. The numerical and experimental results show that the breaking mechanism of the pre-holed disc specimens is mainly due to the initiation of the radially induced tensile cracks which are growth from the surface of the central hole. Radially cracks propagated toward the direction of diametrical loading. It has been observed that for the case of disc specimens with multiple holes under diametrical compressive loading, the breaking process of the modelled specimens may occur due to the simultaneous cracks propagation and cracks coalescence phenomena. These results also show that as the hole diameter and the number of the holes increases both the failure stress and the crack initiation stress decreases. The experimental results already exist in the literature are quit agree with the proposed numerical simulation results which validates this simulation procedure.

A fracture mechanics simulation of the pre-holed concrete Brazilian discs

Sarfarazi, Vahab,Haeri, Hadi,Shemirani, Alireza Bagher,Nezamabadi, Maryam Firoozi Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.3

Brazilian disc test is one of the most widely used experiments in the literature of geo-mechanics. In this work, the pre-holed concrete Brazilian disc specimens are numerically modelled by a two-dimensional discrete element approach. The cracks initiations, propagations and coalescences in the numerically simulated Brazilian discs (each containing a single cylindrical hole and or multiple holes) are studied. The pre-holed Brazilian discs are numerically tested under Brazilian test conditions. The single-holed Brazilian discs with different ratios of the diameter of the holes to that of the disc radius are modelled first. The breakage load in the ring type disc specimens containing an internal hole with varying diameters is measured and the crack propagation mechanism around the wall of the ring is investigated. The crack propagation and coalescence mechanisms are also studied for the case of multi-holes' concrete Brazilian discs. The numerical and experimental results show that the breaking mechanism of the pre-holed disc specimens is mainly due to the initiation of the radially induced tensile cracks which are growth from the surface of the central hole. Radially cracks propagated toward the direction of diametrical loading. It has been observed that for the case of disc specimens with multiple holes under diametrical compressive loading, the breaking process of the modelled specimens may occur due to the simultaneous cracks propagation and cracks coalescence phenomena. These results also show that as the hole diameter and the number of the holes increases both the failure stress and the crack initiation stress decreases. The experimental results already exist in the literature are quit agree with the proposed numerical simulation results which validates this simulation procedure.

Experimental investigation of the pullout behavior of fiber concrete with inclination steel fibers

Seyyed Amir Hossein, Madani,S. Mohammad, Mirhosseini,Ehsanolah, Zeighami,Alireza, NezamAbadi Techno-Press 2022 Advances in concrete construction Vol.14 No.5

Cement-based matrixes have low tensile strength and negligible ductility. Adding fibres to these matrixes will improve their mechanical properties and make these composites suitable for structural applications. Post-cracking tensile strength of steel fibers-reinforced cementitious composite materials is directly related to the number of transverse fibers passing through the crack width and the pulling-out behavior of each of the fibers. Therefore, the exact recognition of the pullout behavior of single fibers is necessary to understand the uniaxial tensile and bending behavior of steel fiber-reinforced concrete. In this paper, an experimental study has been carried out on the pullout behavior of 3D (steel fibers with totally two hooks at both ends), 4D (steel fibers with a total of four hooks at both ends), and 5D (steel fibers with totally six hooks at both ends) in which the fibers have been located either perpendicular to the crack width or in an inclined manner. The pullout behavior of the mentioned steel fibers at an inclination angle of 0, 15, 30, 45, and 60 degrees and with embedded lengths of 10, 15, 20, 25, and 30 millimetres is studied in order to explore the simultaneous effect of the inclination angle of the fibers relative to the alongside loading and the embedded length of fibers on the pullout response in each case, including the maximal pullout force, the slip of the maximum point of pullout force, pullout energy, fiber rupture, and concrete matrix spalling. The results showed that the maximum pullout energy in 3D, 4D, and 5D steel fibers with different embedded lengths occurs at 0 to 30° inclination angles. In 5D fibers, maximum pullout energy occurs at a 30° angle with a 25 mm embedded length.