ORCID Profile
0009-0000-3577-7141
Current Organisation
UNSW Sydney
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Publisher: Elsevier BV
Date: 11-2017
Publisher: SAGE Publications
Date: 19-06-2023
DOI: 10.1177/13694332231180372
Abstract: The assessment of the fatigue crack growth rate behavior of welded structural components made of ultra-high strength steels (UHHS) is very important to gain a comprehensive understanding of these materials under high-cycle fatigue loadings and to enhance their applications in the construction industry. The literature on the fatigue crack growth rates of welded ultra-high strength steel plates with nominal yield strengths higher than 690 MPa is very scarce and only very limited research has been done thus far to provide the Paris’ Law fatigue material constants for welded UHSS components in terms of the base metal (BM), the weld metal (WM), and the heat-affected zone (HAZ) regions, which are essential for fatigue life prediction. Hence, the fatigue crack growth rates of butt-welded UHSS plates with three grades (S700, S960, and S1100) are experimentally investigated in this study using Paris’ Law for these three different regions of the welded components. Gas metal arc welding (GMAW) and laser welding (LW) methods are adopted to analyze the influence of welding methods on each steel grade with respect to their static and fatigue strength, microstructural changes, and hardness. In the fatigue crack growth rate test, it was observed that the S700 base material shows the lowest fatigue crack propagation resistance amongst these three grades. In welded components, laser welding outperforms gas welding in terms of the fatigue crack growth resistance. Comparisons of fatigue crack growth behaviors are made among all three tested UHSSs as well as with those from the literature.
Publisher: Elsevier BV
Date: 2022
Publisher: Trans Tech Publications, Ltd.
Date: 09-2016
DOI: 10.4028/WWW.SCIENTIFIC.NET/KEM.713.159
Abstract: Thin compact tension specimens made of direct quenched ultra-high strength steel were tested under constant rate uniaxial tensile load. The length of the crack was monitored using optical microscopes on both sides of the specimens during the fatigue pre-cracking (using a chevron V-notch). Deformations during the crack lengthening were recorded by a full-field measurement technique using a set of digital cameras to check the effect of side grooves on reduction of surface deformation. The Specimen without side grooves showed a high level of plasticity, thickness reduction, and crack growth along a deviating path. In addition, the fracture surface showed excessive failure along the inclined plane. The presence of side grooves, however, led to the decrease of the maximum applied force at final fracture while the force prior to crack tearing was almost the same as the specimen without side grooves. Grooves significantly reduced the inclination of the fracture plane and plastic deformation due to removal of low stress triaxiality on the surface. They led to the fracture along a straight path and approximately even surface which makes them beneficial especially when compliance method is used in plane stress fracture tests.
Publisher: American Society of Mechanical Engineers
Date: 02-07-2012
Abstract: Due to the tendency to increase the velocity of high-speed trains, concerns about their probable events have increased. Since train’s frontal nose is the first part of the train which is damaged at the frontal impact, specific attention should be paid to the design of this part. In this study an effort has been conducted to design a nose with light weight which can absorb maximum amount of energy that is possible when a frontal collision occurs. To this aim and with attention to aerodynamic considerations, application of aluminum honeycomb (HC) sandwich panel as an internal layer of train nose has been studied. This paper includes two main parts. The first part is dedicated to the simulation of aluminum HC sandwich panel with both shell and solid elements under dynamic crush loads. While the frontal collision of nose with different internal layer thicknesses of HC has been simulated in the second part and an optimum thickness has been proposed based on the generated results. It has been demonstrated that for all thicknesses amount of energy absorption has been increased at least 35%. Finite element method using LS-DYNA commercial package has been used for the numerical simulation. The results have been validated with available experimental results and acceptable agreement has been observed.
Publisher: Elsevier BV
Date: 11-2022
Publisher: Elsevier BV
Date: 11-2021
Publisher: ASME International
Date: 25-07-2016
DOI: 10.1115/1.4033930
Abstract: Deformation of a direct quenched type of ultra-high strength steel (UHSS) with low-carbon content is studied in this work. Although this material, as manufactured, combines high strength and good ductility, it is highly sensitive to the workshop fabrication processes used. The presence of stress concentration due to structural discontinuity or notch effects can accentuate the effect of fabrication processes on the deformation capacity of the material. To evaluate the influence of fabrication methods on deformation capacity, a series of tensile tests are done on both pure base material (BM) and after the steel has been subjected to heat input (HI) or cold forming (CF). To study the effect of HI due to welding or other heat-based workshop fabrication processes, the surface of the material was dressed by laser beam at controlled speed and laser intensity. CF effects were studied by bending the specimens to a predetermined angle prior to subjecting the steel to tensile testing. Experimental results were compared with numerical simulation using ls-dyna simulation software. The generated results show acceptable agreement between experimental and numerical simulation outcomes.
Publisher: Elsevier BV
Date: 12-2016
Publisher: Elsevier BV
Date: 11-2019
Publisher: Elsevier BV
Date: 10-2023
Publisher: American Society of Civil Engineers (ASCE)
Date: 04-2023
Publisher: Elsevier BV
Date: 02-2020
Publisher: SAGE Publications
Date: 18-04-2013
Abstract: Since train’s frontal nose is the first part of the train which is damaged at the frontal impact, specific attention should be paid to the design of this part. In this study, an effort has been conducted to the design of a nose with light weight which can absorb maximum amount of energy that is possible during a frontal collision. To this aim and with attention to aerodynamic considerations, application of aluminium honeycomb sandwich panel has been studied. This paper includes two main parts. The first part is dedicated to the simulation of aluminium honeycomb sandwich panel, while the frontal collision of nose with different internal layer thicknesses of honeycomb and various nose lengths have been simulated in the second part. Finite element method using LS-DYNA commercial package has been used for the numerical simulation. The results have been validated with available experimental results and an acceptable agreement has been observed.
Publisher: Elsevier BV
Date: 11-2017
Publisher: Rakenteiden mekaniikka
Date: 31-12-2019
DOI: 10.23998/RM.76267
Abstract: Research on the bond performance of CFRP-strengthened steel have been done for the past years, but it has mainly focused on lower grades of steel. The performance of the bond between ultra-high modulus (UHM) CFRP and high/ultra-high strength steel (HSS/UHSS) is investigated in this paper. A series of experiments have been conducted, with single/double side-strengthened (SSS/DSS) HSS/UHSS with CFRP laminates using Araldite adhesive. It was found that strengthening up to the ultimate strength of the DSS specimens is feasible. However, debonding happens at the ultimate strength of SSS specimens.
Publisher: Elsevier BV
Date: 02-2023
Publisher: Elsevier BV
Date: 04-2022
Publisher: Elsevier BV
Date: 06-2023
Publisher: MDPI AG
Date: 05-10-2022
DOI: 10.3390/MA15196906
Abstract: High-speed electric motors, e.g., axially laminated anisotropic synchronous reluctance motors (ALA-SynRM), use a solid rotor manufactured by joining alternating layers of magnetic and non-magnetic metallic sheets. The strength of the dissimilar metallic joints is critical for the rotor’s ability to withstand the operating conditions of the high-speed electrical machine. In this work, various dissimilar metallic joint configurations that can be used in high-speed ALA-SynRM rotors are studied by analyzing the shear strength, microstructure, hardness, and composition of the joints. Metallic joints of structural steels and Inconel® alloys fabricated by vacuum brazing and hot isostatic pressing (HIP) are studied. Finite element analysis (FEA) was performed to calculate the maximum shear stress of the joints that were subjected to various high speed operating conditions. The shear strength of the test specimens was measured and compared with FEA results. The microstructure and chemical composition of the joints were studied by using optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) on SEM. The results show that the hot isostatic pressed S1100MC-IN718 joint achieved the highest ultimate shear strength (233.3 MPa) followed by vacuum brazed S355MC-IN600 joint (230.1 MPa) and HIP S355-IN718 (203.5 MPa), thereby showing that vacuum brazing and HIP can be viable manufacturing methods to fabricate a high-speed ALA-SynRM rotor.
Publisher: Elsevier BV
Date: 11-2022
No related grants have been discovered for Mohsen Amraei.