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Effects of welding parameters and welding sequence on residual stress and distortion in Al6061-T6 aluminum alloy for T-shaped welded joint 被引量:16
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作者 Amirreza KHOSHROYAN Armin Rahmati DARVAZI 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2020年第1期76-89,共14页
The distribution of temperature and then the distribution of residual stress and distortion in the stiffened aluminum alloy Al6061-T6 plates under the metal inert gas(MIG)welding process were investigated by three dim... The distribution of temperature and then the distribution of residual stress and distortion in the stiffened aluminum alloy Al6061-T6 plates under the metal inert gas(MIG)welding process were investigated by three dimensional thermo-mechanical coupled finite element model using Ansys software.The properties of materials were considered temperature-dependent and the filler metal was added to the workpiece by the element birth and death technique.In three modes of current,two different speeds and two various sequences,the distribution of residual stress and distortion were calculated and analyzed.The results showed that increase in welding speed decreased the vertical deflection in the plate,transverse shrinkage and angular distortion of plate and the lateral deflection of stiffener,but increased the maximum longitudinal tensile stress in the plate and stiffener.Furthermore,increase in current increased the residual stress and deformation in the plate and stiffener,and the change in the welding sequence changed the distribution of the distortion in the plate and the stiffener without significant change in the distribution of the longitudinal residual stress. 展开更多
关键词 welding parameters welding sequence residual stress DISTORTION
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Numerical Investigation of Transmission of Low Frequency Sound Through a Smooth Air-water Interface 被引量:3
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作者 Parviz Ghadimi Ahreza Bolghasi +1 位作者 Mohammad A. Feizi Chekab Rahim Zamanian 《Journal of Marine Science and Application》 CSCD 2015年第3期334-342,共9页
It is the traditional belief that sound transmission from water to the air is very weak due to a large contrast between air and water impedances. Recently, the enhanced sound transmission and anomalous transparency of... It is the traditional belief that sound transmission from water to the air is very weak due to a large contrast between air and water impedances. Recently, the enhanced sound transmission and anomalous transparency of air-water interface have been introduced. Anomalous transparency of air-water interface states that the sound generated by a submerged shallow depth monopole point source localized at depths less than 1/10 sound wavelength, can be transmitted into the air with omni-directional pattern. The generated sound has 35 times higher power compared to the classical ray theory prediction. In this paper, sound transmission through air-water interface for a localized underwater shallow depth source is examined. To accomplish this, two-phase coupled Helmholtz wave equations in two-phase media of air-water are solved by the commercial finite element based COMSOL Multiphysics software. Ratios of pressure amplitudes of different sound sources in two different underwater and air coordinates are computed and analyzed against non-dimensional ratio of the source depth (D) to the sound wavelength (λ). The obtained results are compared with the experimental data and good agreement is displayed. 展开更多
关键词 enhanced sound transmission anomalous transparency air-water interface shallow depth source sound transmission Helmholtz wave equations
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Numerical Analysis of the High Skew Propeller of an Underwater Vehicle 被引量:3
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作者 Hassan Ghasseni Parviz Ghadimi 《Journal of Marine Science and Application》 2011年第3期289-299,共11页
A numerical analysis based on the boundary element method (BEM) was presented for the hydrodynamic performance of a high skew propeller (HSP) which is employed by an underwater vehicle (UV). Since UVs operate at... A numerical analysis based on the boundary element method (BEM) was presented for the hydrodynamic performance of a high skew propeller (HSP) which is employed by an underwater vehicle (UV). Since UVs operate at two different working conditions (surface and submerged conditions), the design of such a propeller is a cumbersome task. This is primarily due to the fact that the resistance forces as well as the vessel efficiency under these conditions are significantly different. Therefbre, some factors are necessary for the design of the optimum propeller to utilize the power at the mentioned conditions. The design objectives of the optimum propeller are to obtain the highest possible thrust, minimum torque, and efficiency. In the current study, a 5-bladed HSP was chosen for running the UV. This propeller operated at the stern of the UV hull where the inflow velocity to the propeller was non-uniform. Some parameters of the propeller were predicted based on the UV geometrical hull and operating conditions. The computed results include the pressure distribution and the hydrodynamic characteristics of the HSP in open water conditions, and comparison of these results with those of the experimental data indicates good agreement. The propeller efficiency for both submerged and surface conditions was found to be 67% and 64%, respectively, which compared to conventional propellers is a significantly higher efficiency. 展开更多
关键词 boundary element method (BEM) hydrodynamic analysis high skew propeller surface andsubmerged conditions
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Developing a Computer Program for Detailed Study of Planing Hull's Spray Based on Morabito's Approach 被引量:2
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作者 Parviz Ghadimi Sasan Tavakoli +1 位作者 Abbas Dashtimanesh Arya Pirooz 《Journal of Marine Science and Application》 2014年第4期402-415,共14页
Recently, Morabito(2010) has studied the water spray phenomena in planing hulls and presented new analytical equations. However, these equations have not been used for detailed parametric studies of water spray around... Recently, Morabito(2010) has studied the water spray phenomena in planing hulls and presented new analytical equations. However, these equations have not been used for detailed parametric studies of water spray around planing hulls. In this paper, a straight forward analysis is conducted to apply these analytical equations for finding the spray geometry profile by developing a computer program based on presented computational process. The obtained results of the developed computer program are compared against existing data in the literature and favorable accuracy is achieved. Parametric studies have been conducted for different physical parameters. Positions of spray apex are computed and three dimensional profiles of spray are examined. It is concluded that spray height increases by an increase in the speed coefficient or the deadrise angle. Ultimately, a computational process is added to Savitsky's method and variations of spray apex are computed for different velocities. It is shown that vertical, lateral, and longitudinal positions of spray increase as the craft speed increases. On the other hand, two new angles are defined in top view and it is concluded that they have direct relation with the trim angle. However, they show inverse relation with the deadrise angle. 展开更多
关键词 SPRAY prismatic planing hull mathematical modeling water spray parametric study
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Hydrodynamic characteristics of the surface-piercing propellers for the planing craft 被引量:2
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作者 Hassan GHASSEMI 《Journal of Marine Science and Application》 2009年第4期267-274,共8页
Demand for high-speed marine vehicles (HSMVs) is high among both commercial and naval users. It is the duty of the marine vessel's designer to provide a hull and propulsion system that diminishes drag, improves pr... Demand for high-speed marine vehicles (HSMVs) is high among both commercial and naval users. It is the duty of the marine vessel's designer to provide a hull and propulsion system that diminishes drag, improves propulsive efficiency, increases safety and improves maneuverability. From the propulsor side, surface piercing propellers (SPPs) should improve performance. Unlike immersed propellers, behavior of the SPP is affected by depth of immersion, Weber number and shaft inclination angle. This paper uses a practical numerical method to predict the hydrodynamic characteristics of an SPP. The critical advance velocity ratio is derived using the Weber number and pitch ratio in the transition mode, then the potential based boundary element method (BEM) is used on the engaged surfaces. Two models of three and six-bladed SPPs (SPP-1 and SPP-2) were selected and some results are shown. 展开更多
关键词 surface piercing propeller boundary element method hydrodynamic characteristics
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Hydrodynamic Efficiency Improvement of the High Skew Propeller for the Underwater Vehicle Under Surface and Submerged Conditions 被引量:1
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作者 Hassan Ghassemi Parviz Ghadimi 《Journal of Ocean University of China》 SCIE CAS 2011年第4期314-324,共11页
An algorithm based on the Boundary Element Method(BEM)is presented for designing the High Skew Propeller(HSP)used in an Underwater Vehicle(UV).Since UVs operate under two different kinds of working conditions(i.e.surf... An algorithm based on the Boundary Element Method(BEM)is presented for designing the High Skew Propeller(HSP)used in an Underwater Vehicle(UV).Since UVs operate under two different kinds of working conditions(i.e.surface and submerged conditions),the design of such a propeller is an unwieldy task.This is mainly due to the fact that the resistance forces as well as the vessel efficiency under these conditions are significantly different.Therefore,some factors are necessary for the design of the opti-mum propeller to utilize the power under the mentioned conditions.The design objectives of the optimum propeller are to obtain the highest possible thrust and efficiency with the minimum torque.For the current UV,the main dimensions of the propeller are pre-dicted based on the given required thrust and the defined operating conditions.These dimensions(number of blades,pitch,diameter,expanded area ratio,thickness and camber)are determined through iterative procedure.Because the propeller operates at the stern of the UV where the inflow velocity to the propeller is non-uniform,a 5-blade HSP is preferred for running the UV.Finally,the propel-ler is designed based on the numerical calculations to acquire the improved hydrodynamic efficiency. 展开更多
关键词 underwater vehicle propeller design factors high skew propeller surface and submerged conditions hydrodynamic propeller efficiency
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Sound Scattering From Rough Bubbly Ocean Surface Based on Modified Sea Surface Acoustic Simulator and Consideration of Various Incident Angles and Sub-surface Bubbles' Radii 被引量:1
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作者 Alireza Bolghasi Parviz Ghadimi Mohammad A. Feizi Chekab 《Journal of Marine Science and Application》 CSCD 2016年第3期275-287,共13页
The aim of the present study is to improve the capabilities and precision of a recently introduced Sea Surface Acoustic Simulator(SSAS) developed based on optimization of the Helmholtz–Kirchhoff–Fresnel(HKF) method.... The aim of the present study is to improve the capabilities and precision of a recently introduced Sea Surface Acoustic Simulator(SSAS) developed based on optimization of the Helmholtz–Kirchhoff–Fresnel(HKF) method. The improved acoustic simulator, hereby known as the Modified SSAS(MSSAS), is capable of determining sound scattering from the sea surface and includes an extended Hall–Novarini model and optimized HKF method. The extended Hall–Novarini model is used for considering the effects of sub-surface bubbles over a wider range of radii of sub-surface bubbles compared to the previous SSAS version. Furthermore, MSSAS has the capability of making a three-dimensional simulation of scattered sound from the rough bubbly sea surface with less error than that of the Critical Sea Tests(CST) experiments. Also, it presents scattered pressure levels from the rough bubbly sea surface based on various incident angles of sound. Wind speed, frequency, incident angle, and pressure level of the sound source are considered as input data, and scattered pressure levels and scattering coefficients are provided. Finally, different parametric studies were conducted on wind speeds, frequencies, and incident angles to indicate that MSSAS is quite capable of simulating sound scattering from the rough bubbly sea surface, according to the scattering mechanisms determined by Ogden and Erskine. Therefore, it is concluded that MSSAS is valid for both scattering mechanisms and the transition region between them that are defined by Ogden and Erskine. 展开更多
关键词 Modified SSAS method scattering strength rough bubbly sea surface wind speed sub-surface bubble plume surface scattering mechanisms
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A Significant Look at the Effects of Persian Gulf Environmental Conditions on Sound Scattering Based on Small Perturbation Method
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作者 Parviz Ghadimi Alireza Bolghasi +1 位作者 Mohammad A. Feizi Chekab Rahim Zamanian 《Journal of Marine Science and Application》 CSCD 2015年第4期413-424,共12页
The main goal of this paper is to investigate sound scattering from the sea surface, by Kuo's small perturbation method (SPM), in the Persian Gulf's environmental conditions. Accordingly the SPM method is reviewed... The main goal of this paper is to investigate sound scattering from the sea surface, by Kuo's small perturbation method (SPM), in the Persian Gulf's environmental conditions. Accordingly the SPM method is reviewed, then it is demonstrated how it can accurately model sound scattering from the sea surface. Since in Kuo's approach, the effects of surface roughness and sub-surface bubble plumes on incident sounds can be studied separately, it is possible to investigate the importance of each mechanism in various scattering regimes. To conduct this study, wind and wave information reported by Arzanah station as well as some numerical atmospheric models for the Persian Gulf are presented and applied to examine sound scattering from the sea surface in the Persian Gulf region. Plots of scattering strength by Kuo's SPM method versus grazing angle for various frequencies, wave heights, and wind speeds are presented. The calculated scattering strength by the SPM method for various frequencies and wind speeds are compared against the results of critical sea tests 7 (CST-7). The favorable agreement achieved for sound scattering in the Persian Gulf region is indicative of the fact that the SPM method can quite accurately model and predict sound scattering from the sea surface. 展开更多
关键词 sea surface Persian Gulf small perturbation method (SPM) wind rose plots wave rose plots sound scattering surface roughness sub-surface bubble plumes
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Sea Surface Effects on Sound Scattering in the Persian Gulf Region Based on Empirical Relations 被引量:2
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作者 Parviz Ghadimi Alireza Bolghasi Mohammad A. Feizi Chekab 《Journal of Marine Science and Application》 CSCD 2015年第2期113-125,共13页
In this paper, sound scattering from the sea surface in the Persian Gulf region is investigated. Chapman-Harris and Ogden-Erskine empirical relations coupled with perturbation theory are implemented. Based on the Ogde... In this paper, sound scattering from the sea surface in the Persian Gulf region is investigated. Chapman-Harris and Ogden-Erskine empirical relations coupled with perturbation theory are implemented. Based on the Ogden and Erskine's experiments, sound scattering from the sea surface has three different regimes in which two mechanisms of surface roughness and subsurface bubble clouds are involved. Ogden-Erskine's scattering relation which consists of perturbation theory and Chapman-Harris's scattering terms are verified by the experimental data of Critical Sea Tests 7. Subsequently, wind speed in the Persian Gulf is provided based on three data bases of Arzanah station, ERA40, and PERGOS. Accordingly, surface scattering strength in the Persian Gulf region is calculated at different grazing angles, frequencies and provided wind speeds. Based on the resulted values of scattering strength, scattered intensity from the sea surface is also studied. These studies indicate that both scattering strength and scattered intensity generally increase as grazing angle, frequency and wind speed increase. 展开更多
关键词 surface scattering strength scattered intensity seasurface effects Persian Gulf sound scattering empirical relation perturbation theory
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