فهرس المقالات Strain rate

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  1 - A New Approach for Stress State - Dependent Flow Localization Failure Bounded Through Ductile Damage in Dynamically Loaded Sheets
  F Hosseini Mansoub A Basti A Darvizeh A Zajkani
  10.22034/jsm.2019.1869860.1449
  In this paper, a new approach is proposed for stress state - dependent flow localization in bifurcation failure model bounded through ductile damage in dynamically loaded sheets. Onset of localized necking is considered in phenomenological way for different strain rates أکثر

  In this paper, a new approach is proposed for stress state - dependent flow localization in bifurcation failure model bounded through ductile damage in dynamically loaded sheets. Onset of localized necking is considered in phenomenological way for different strain rates to draw the forming limit diagram (FLD). Using a strain metal hardening exponent in the Vertex theory related to the strain rate helps investigate rate- dependent metal forming limits. Besides, the paper utilizes the model of ductile damage as a function of strain condition, stress states (triaxiality and Lode parameters), and the symbols of stiffness strain to predict the onset of the necking. It is worth noting that updated level of elasticity modulus in the plastic deforming is attributed as an essential index for the ductile damage measuring. According to original formulations, a UMAT subroutine is developed in the finite element simulation by ABAQUS code to analyze and connect the related constitutive models. Results reveal that the FLD levels increase for St 13 material through enhancing the strain rate. تفاصيل المقالة
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  2 - Study of Johnson-Cook Model Comprehensiveness at Moderate Strain Rate and Inverse Analysis to Modify the Constitutive Parameters Using Cold Wire Drawing Process
  Ashkan Mahmoud Aghdami Behnam Davoodi
  Johnson cook constitutive equation was utilized to model the 10100 copper alloy wires at the cold wire drawing process. Johnson cook parameters were determined using several quasi-static tensile tests at different strain rates. The wire drawing experiments carried out a أکثر

  Johnson cook constitutive equation was utilized to model the 10100 copper alloy wires at the cold wire drawing process. Johnson cook parameters were determined using several quasi-static tensile tests at different strain rates. The wire drawing experiments carried out at seven drawing conditions with two areal reductions and four drawing speeds caused the strain rate ranged from 37 to 115 s-1. Wire Drawing forces were measured using a load cell connected to the die. Analytical and finite element with VUHARD subroutine solutions were implemented to calculate the drawing forces using the Johnson cook parameters as well. Results showed that the Johnson cook model with parameters determined from a quasi-static condition was not able to predict the material behavior at the wire drawing process with a moderate strain rate. Inverse analysis using the Newton- Raphson method to minimize the objective function was carried out to modify the Johnson cook parameters. Updated Johnson cook parameters showed much more correlation with experimental results. تفاصيل المقالة
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  3 - Failure Rate of Empty and Fluid-Filled Concrete Pipes under High Strain Rates
  Asadollah Ranjbar Karkanaki Mohsen Parviz Alireza Darvishpour Mahyar Taheri
  10.30495/ijase.2023.1987393.1070
  Considering the importance of the performance of buried concrete pipes under external loads and the role played by concrete specifications and pipe thickness in this regard, the current study analyzed the failure rate and response of concrete pipes buried in three types أکثر

  Considering the importance of the performance of buried concrete pipes under external loads and the role played by concrete specifications and pipe thickness in this regard, the current study analyzed the failure rate and response of concrete pipes buried in three types of soil to a TNT blast load using the Lagrangian-Eulerian method in the nonlinear dynamics software LS-DYNA. The results show that the presence of fluid in the pipe generates an internal pressure, which reduces the deformation of the pipe under the blast load. It was also found that the higher the P-crush of the concrete pipe, the smaller the strain and displacement generated under the blast pressure. In thicker pipes, sometimes the damage is limited to the outer sections of the shell, and the pipe remains usable. However, in thinner pipes, damage often affects both inner and outer surfaces of the shell, rendering the pipe unusable. The plastic strain generated in Specimen 1 in Soil Type 1 is 85% higher than the acceptable plastic strain of the concrete pipe. Moreover, this value is 87% for Soil Type 2 and 85% for Soil Type 3. تفاصيل المقالة
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  4 - Comparison of Compressive Properties Between Va-cuum Infusion and Hand Lay-Up Method Toward Bal-sa Core Sandwich Composites
  م. نجفی ر. اسلامی فارسانی سید محمدرضا خلیلی
  The aim of this work is to evaluate the influence of fabrication methods on the com-pressive properties of sandwich composites using both experimental work and numerical simulations. Two types of sandwich composites with E-glass/Kevlar/polyester resin facings and End-gr أکثر

  The aim of this work is to evaluate the influence of fabrication methods on the com-pressive properties of sandwich composites using both experimental work and numerical simulations. Two types of sandwich composites with E-glass/Kevlar/polyester resin facings and End-grain balsa wood as core have been produced by vacuum infusion processing (VIP) and hand-lay up (HL) method. Compression tests on sandwich composites showed that the mean values of compressive strength of HL and VIP composites are 15.02 MPa and 28.27 MPa, respectively. The performance of sandwich composites manufactured by VIP are presented and compared to the sandwich composites manufactured by HL method. Based on the experimental tests, VIP appears to produce higher results of sandwich composite compressive properties compared to the HL method. Consequently, in this work, the compressive properties of sandwich composites were characterized by finite element analysis (FEA) and a comparison of the compressive prop-erties in various fabrication methods was then presented. The correspondence between the predicted numerical results and the experiments proves the accuracy of this model. تفاصيل المقالة
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  5 - بررسی چقرمگی شکست و حساسیت به نرخ کرنش لایه نازک نیترید تانتالوم تولید شده به روش کندوپاش مغناطیسی واکنشی
  Siavash فیروزآبادی کامران دهقانی مالک نادری فرزاد محبوبی
  نیترید تانتالوم به دلیل سختی بالا و مقاومت به خوردگی خوب توانسته است توجهات زیادی را به عنوان پوششی مناسب جلب نماید. اما چقرمگی شکست لایه‌های نازک نیترید تانتالوم که یکی از عوامل تاثیرگذار بر طول عمر پوشش است، هنوز به خوبی بررسی نشده است. در این پژوهش، برای نخستین بار، أکثر

  نیترید تانتالوم به دلیل سختی بالا و مقاومت به خوردگی خوب توانسته است توجهات زیادی را به عنوان پوششی مناسب جلب نماید. اما چقرمگی شکست لایه‌های نازک نیترید تانتالوم که یکی از عوامل تاثیرگذار بر طول عمر پوشش است، هنوز به خوبی بررسی نشده است. در این پژوهش، برای نخستین بار، چقرمگی شکست، پلاستیسیته و حساسیت به نرخ کرنش لایه های نازک نیترید تانتالوم به کمک روش نانو فرورونده بررسی و ارزیابی شد. در این بررسی نشان داده شده که تغییرات چقرمگی شکست فازهای مختلف نیترید تانتالوم از MPa√m 6/0 تا MPa√m 7/8 بسته به میزان نیتروزن موجود در سیستم لایه نشانی و به تبع آن نیتروژن موجود در شبکه نیترید تانتالوم افزایش می‌یابد. همچنین دو فاز مهم نیترید تانتالوم یعنی γ-Ta2N و δ-TaN دارای حساسیت به نرخ کرنش منفی و مثبت هستند که می‌توان این رفتار را به تغییرات ساختار فازی حین انجام آزمون نسبت داد. تفاصيل المقالة
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  6 - Optimization of Axisymmetric Extrusion Die Profiles
  حسن نحوی مهدی حسن زاده
  In this research, optimization process of axisymmetric extrusion dies is proposed. Plastic zone is analyzed using finite element method in the Eulerian system with flow formulation. The die profiles are defined by Bezier curves with six control points. Two effective fun أکثر

  In this research, optimization process of axisymmetric extrusion dies is proposed. Plastic zone is analyzed using finite element method in the Eulerian system with flow formulation. The die profiles are defined by Bezier curves with six control points. Two effective functions are considered in this research; standard deviation of the strain rate and the rate of energy consumption during extrusion process. A coupled numerical approach of finite element analysis in Eulerian system and the non-gradient Nelder-Mead method is utilized to determine optimum die profiles. Results show that optimized die has higher uniformity in strain rate distribution and less strain values with respect to the non-optimum conical die. In the case of minimizing energy consumption rate, results show that for the die with constant and variable lengths and low friction, the die profile tends to the stream line. In die with variable length and high friction, friction has more effective role in optimization and the die length tends towards lower lengths during optimization. تفاصيل المقالة