دکتر کدخدایان
استاد، گروه مهندسی مکانیک، دانشگاه فردوسی مشهد
[ 1 ] - شکل‌دهی الکترومغناطیس ورق با استفاده از شکل‌دهی به روی پانچ به جای شکل‌دهی به درون قالب
سرعت بالا و عدم کنترل دقیق بر توزیع فشار،شکل‌دهی الکترومغناطیس ورق به درون قالب را محدود به هندسه‌های ساده با عمق کم کرده است. می‌توان با استفاده از پانچ محدب به جای قالب مقعر عمق بیشتری برای ورق بدست آورد. در این مقاله شکل‌دهی الکترومغناطیس ورق به روی پانچ محدب و به درون قالب مقعر بررسی شده است. بخش الکترومغناطیس مسئله بصورت تحلیلی و بخش مکانیکی بصورت عددی با کمک نرم‌افزار آباکوس به روش اجزا م...
[ 2 ] - مطالعه تجربی- عددی خمش‌پذیری درکامپوزیت فلز- الیاف شیشه به منظور کاهش عیوب ناشی از فرآیند
امروزه کامپوزیت‌های لایه‌ای فلز- الیاف به دلیل دارا بودن خواص مکانیکی خوب و وزن کم بسیار مورد توجه طراحان، به ویژه صنایع هوافضا قرار گرفته اند. مواد (Fiber Metal Laminate)FML خواص بهتری نسبت به هر دو آلیاژ آلومینیوم و مواد کامپوزیتی از خود نشان می‌دهند. در این پژوهش، خواص خمشی این کامپوزیتها مورد بررسی عددی- تجربی قرار گرفته است. از آنجایی که این چندلایه‌ها دارای قابلیت فرم‌دهی محدود می‌باشند و...
[ 3 ] - A Closed-form Semi-analytical Elastic-Plastic Solution for Predicting the Onset of Flange Wrinkling in Deep-drawing of a Two-layered Circular Plate
In this paper to predict the critical conditions for onset of elastic-plastic wrinkling of flange of a two-layered circular blank during the deep-drawing process a closed-form semi-analytical elastic-plastic solution using Tresca yield criterion alongwith deformation theory in plasticity with considernig the perfectly plastic behaviour of materials is presented. Simplifying the presented soluti...
[ 4 ] - U-Bending Analysis with an Emphasis on Influence of Hardening Models
In this paper the effect of different hardening models in simulating the U-bending process for AA5754-O and DP-Steel, taking a benchmark of NUMISHEET 93 2-D draw bending, has been discussed. The hardening models considered in simulations are: isotropic hardening, pure (linear) kinematic hardening and combined (nonlinear kinematic) hardening. The influence of hardening models on predicting sprin...
[ 5 ] - Two New Non-AFR Criteria for Depicting Strength Differential Effect (SDE) in Anisotropic Sheet Metals
The issue of pressure sensitivity of anisotropic sheet metals is investigated with introducing two new non-AFR criteria which are called here linear and non-Linear pressure sensitive criteria. The yield and plastic potential functions of these criteria are calibrated with directional tensile/compressive yield stresses and directional tensile Lankford coefficients, respectively. To determine unk...
[ 6 ] - An Experimental and Numerical Study of Forming Limit Diagram of Low Carbon Steel Sheets
The forming limit diagram (FLD) is probably the most common representation of sheet metal formability and can be defined as the locus of the principal planar strains where failure is most likely to occur. Low carbon steel sheets have many applications in industries, especially in automotive parts, therefore it is necessary to study the formability of these steel sheets. In this paper, FLDs, wer...
[ 7 ] - Implementing the New First and Second Differentiation of a General Yield Surface in Explicit and Implicit Rate-Independent Plasticity
In the current research with novel first and second differentiations of a yield function, Euler forward along with Euler backward with its consistent elastic-plastic modulus are newly implemented in finite element program in rate-independent plasticity. An elastic-plastic internally pressurized thick walled cylinder is analyzed with four famous criteria including both pressure dependent and ind...
[ 8 ] - SHEET ELECTROMAGNETIC FORMING USING CONVEX PUNCH INSTEAD OF CONVAVE DIE
High speed and absence of a precise control over pressure distribution confine sheet Electromagnetic Forming into a die to simple shapes having shallow depth. It is possible to reach a higher depth by using a convex punch instead of a concave die. In this study, sheet Electromagnetic Forming on a punch and sheet Electromagnetic Forming into a die are investigated. The electromagnetic part of th...
[ 9 ] - Non-linear Thermo-mechanical Bending Behavior of Thin and Moderately Thick Functionally Graded Sector Plates Using Dynamic Relaxation Method
In this study, nonlinear bending of solid and annular functionally graded (FG) sector plates subjected to transverse mechanical loading and thermal gradient along the thickness direction is investigated. Material properties are varied continuously along the plate thickness according to power-law distribution of the volume fraction of the constituents. According to von-Karman relation for large ...
[ 10 ] - Elastic/plastic Buckling Analysis of Skew Thin Plates based on Incremental and Deformation Theories of Plasticity using Generalized Differential Quadrature Method
Abstract In this study, generalized differential quadrature analysis of elastic/plastic buckling of skew thin plates is presented. The governing equations are derived for the first time based on the incremental and deformation theories of plasticity and classical plate theory (CPT). The elastic/plastic behavior of plates is described by the Ramberg-Osgood model. The ranges of plate geometries...
[ 11 ] - An Investigation into the Deep Drawing of Fiber-Metal Laminates based on Glass Fiber Reinforced Polypropylene
Abstract Fiber-metal laminates (FMLs) are new type of composite materials which could improve defects of traditional composites in ductility, formability, impact and damage tolerance. Drawing behavior of a thermoplastic based FML was investigated consisting of glass-fiber reinforced polypropylene composite laminate and aluminum AA1200-O as the core and skin layers, respectively. The effects o...
[ 12 ] - A Study on Combination of von Mises and Tresca Yield Loci In Non-Associated Viscoplasticity
In this study a non-associated viscoplastic flow rule (NAVFR) with combining von Mises and Tresca loci in place of yield and plastic potential functions and vice verse is presented. With the aid of fully implicit time stepping scheme and discussing the other studies on plastic potential flow rules and also experimental results it is shown that the proposed NAVFR can be adopted to forecast the e...
[ 13 ] - A General Solution for Implicit Time Stepping Scheme in Rate-dependant Plasticity
In this paper the derivation of the second differentiation of a general yield surface implicit time stepping method along with its consistent elastic-plastic modulus is studied. Moreover, the explicit, trapezoidal implicit and fully implicit time stepping schemes are compared in rate-dependant plasticity. It is shown that implementing fully implicit time stepping scheme in rate-dependant plasti...
[ 14 ] - Energy Absorption Analysis and Multi-objective Optimization of Tri-layer Cups Subjected to Quasi-static Axial Compressive Loading
In this paper, the energy absorption features of tri-layer explosive-welded deep-drawn cups subjected to quasi-static axial compressive loading are investigated numerically and experimentally. To produce the cups, tri-layer blanks composed of aluminum and stainless steel alloys were fabricated by an explosive-welding process and formed by a deep drawing setup. The quasi-static tests were carrie...
[ 15 ] - The Effect of Ridges to Improve Ductility and Reduce Deformation Energy in Deep-Drawing Process
In this research, two new methods that improve the drawing depth of deep-drawing processes have been introduced. In the first technique, by creating ridges on the punch surface, the stress concentration is decreased on the blank near the punch edge, in turn increasing the drawing depth. The second method is based on the principle of reducing resistant force in the flange area between the die, t...
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