رامین ابراهیمی
عضو هیات علمی دانشگاه شیراز
[ 1 ] - بررسی رفتار خستگی آلومینیوم خالص تجاری پس از فرآیند اکستروژن برشی ساده
در تحقیق حاضر رفتار خستگی آلومینیوم خالص تجاری تغییر شکل یافته بوسیله فرآیند اکستروژن برشی ساده مورد بررسی قرار گرفته است. بدین منظور، قالب اکستروژن برشی ساده طراحی و ساخته شد. نمونههای آلومینیمی تا چهار مرحله مطابق مسیر بهینه C در این قالب کرنش دیدند. آنالیز پراش اشعه ایکس نشان داد که اندازه دانه پس از چهار مرحله به 120 نانومتر کاهش یافته است. نمونههای آنیل و فرآیند شده با آزمونهای سختی سن...
[ 2 ] - تاثیر پارامترهای فرآیندی بر اکستروژن معکوس داغ آلیاژ Al6061
اکستروژن معکوس، یکی از فرآیندهای شکل‌دهی فلزات می‌باشد که درسال‌های اخیر، کاربرد وسیعی یافته و برای تولید قطعات توخالی استفاده می‌شود. آلیاژهای آلومینیوم با توجه به مزایای مختلف، بهصورت گسترده در صنعت خودرو و هواپیما استفاده میشوند. در این پژوهش تاثیر پارامترهای فرآیندی نظیر میزان کاهش سطح مقطع، دما و شرایط اصطکاکی در فرآیند اکستروژن معکوس داغ آلیاژ آلومینیوم 6061 به صورت تجربی و به روش...
[ 3 ] - Mechanical Behavior of TWIP Steel in High Strain Rate Torsional Test
Advanced high strength steels (AHSS) have recently attracted great attention because of their superior mechanical properties. A modern group of these steels, known as twinning induced plasticity (TWIP) steels, shows a unique combination of strength and ductility even at high rates of strain. In order to examine the functionality of such steels in dynamic loading conditions, their mechanical beh...
[ 4 ] - Characteristic Points of Stress-Strain Curve at High Temperature
Determination of critical points on hot stress-strain curve of metals is crucial in thermo-mechanical processes design. In this investigation a mathematical modeling is given to illustrate the behavior of metal during hot deformation processes such as hot rolling. The critical strain for the onset of dynamic recrystallization has been obtained as a function of strain at the maximum stress. In a...
[ 5 ] - The Effect of Simple Shear Extrusion on the Corrosion Behavior of Copper
In this study, corrosion behavior of copper that was deformed by Simple Shear Extrusion (SSE) method was investigated in 3%wt NaCl solution. Modified Williamson-Hall method, applied on the X-ray diffraction patterns of the samples, showed that increase in the number of SSE passes led to increasing in the dislocation density in the copper samples. Moreover, such deformed samples exh...
[ 6 ] - Ten years of severe plastic deformation (SPD) in Iran, part I: equal channel angular pressing (ECAP)
The superior properties of ultrafine-grained materials fabricated by severe plastic deformation (SPD) have attracted the attention of many researchers around the world. Among the top-ranked countries that are active in this field, Iran is interesting because of the late beginnings of SPD in this country and, subsequently, the highest rate of growth in the number of publications during the last...
[ 7 ] - Prediction of Extrusion Pressure in Vortex Extrusion Using a Streamline Approach
Vortex extrusion (VE) is a severe plastic deformation technique which is based on the synergies between high strain accumulation and high hydrostatic pressure. Such a high amount of pressure, places a mandate to seek the method for investigation of the load under processing conditions. For this, kinematically admissible velocity field and upper bound terms based on Bezier formulation are develo...
[ 8 ] - Stacking Fault Energy and Microstructural Insight into the Dynamic Deformation of High-Manganese TRIP and TWIP Steels
The dynamic behavior of three high manganese steels with very different stacking faultenergy (SFE) values (4-30 mJ/m2) were studied using high strain rate torsional tests. The hotrolledmicrostructure of the steel with the lowest SFE of 4 mJ/m2 consisted of a duplex mixture ofaustenite and ε-martensite, but those of the other two steels were fully austenitic. The deformedmicrostructures were stu...
[ 9 ] - The Relationship between Constant Friction Factor and Coefficient of Friction in Metal Forming using Finite Element Analysis
Frictional shear stress is usually determined by utilizing the coefficient of friction or the constant friction factor models. The present study deals with finite element analysis of double cup extrusion process to determine the relationship between constant friction factor (m) and coefficient of friction (µ), since the metal flow in this process is very sensitive to frictional conditions. Ther...
[ 10 ] - Ten years of severe plastic deformation (SPD) in Iran, part II: accumulative roll bonding (ARB)
The present paper is the second part of a previously published overview entitled “ten years of severe plastic deformation (SPD) in Iran”. Part I concentrates on the equal channel angular pressing (ECAP). In this part, the focus is on the accumulative roll bonding (ARB) because, currently, Iran is ranked the first in the world by the total number of publications in this field. In the present sec...
[ 11 ] - Investigation on the Deformation Behavior and Strain Distribution of Commercially Pure Aluminum after Circular Simple Shear Extrusion
Circular simple shear extrusion process was introduced as a new geometry for simple shear extrusion technique to fabricate ultrafine-grained materials. Similar to the simple shear extrusion method, this process is also based on direct extrusion, and the samples deform in a simple shear manner. In this investigation, the simulations were carried out using the commercial finite element code ABAQU...
[ 12 ] - Simulation of a New Process Design to Fabricate a Rectangular Twist Waveguide Using Extrusion and a Twist Die
The aim of the present study is to determine the feasibility of making a rectangular twist waveguide used to rotate electromagnetic waves. For this purpose, the process of fabricating an aluminum rectangular twist waveguide was simulated by making use of finite element method and Deform software. The optimum length and angle of the twist die for manufacturing a twist waveguide with inner cross ...
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