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Ramin Hashemi - One of the best experts on this subject based on the ideXlab platform.

  • measurement of directional anisotropy coefficients for aa7020 t6 tubes and prediction of Forming Limit Curve
    The International Journal of Advanced Manufacturing Technology, 2018
    Co-Authors: F Mousavi, Ramin Hashemi, Reza Madoliat
    Abstract:

    The mechanical properties of tubes in hoop directions can be measured with ring hoop tensile test (RHTT). This test involves placing a ring sample of tube over the two D-shaped mandrels which can be parted with a testing machine. In this article, the goal was measuring the directional anisotropy coefficients of hydroformed AA7020-T6 tubes (r0, r45, and r90) to predict Forming Limit diagram (FLD). Due to deriving anisotropy coefficients in different directions, various tensile tests should be performed for the tube. For longitudinal and circumferential samples, a simple tensile test and ring hoop tensile test were applied to obtain r0 and r90, respectively. Additionally, for testing in 45° to the rolling direction, a new testing method which is inspired by RHTT was used to find r45. Afterwards, Forming Limit diagram of this aluminum alloy was predicted theoretically based on the Marciniak-Kuczynski (M-K) model and Voce hardening law. Since, one of the important factors in gaining accurate FLDs is yield function. Two advanced yield functions, BBC2008 and YLd2011, were selected. These advanced yield functions can describe material’s anisotropy behavior better than the classical ones. The importance of the directional anisotropy coefficients and other data obtained by tensile tests was in calibration of yield functions. Good agreement between the FLD derived under the influence of a calibrated yield function and the experimental FLD supports the present calibration.

  • Forming Limit diagram of aluminum-copper two-layer sheets: numerical simulations and experimental verifications
    The International Journal of Advanced Manufacturing Technology, 2017
    Co-Authors: Ehsan Karajibani, Ramin Hashemi, Mohammad Sedighi
    Abstract:

    The aim of this research was to introduce a simulation-based approach for determination of the Forming Limit Curve (FLC) in two-layer metallic sheets. In this study, the FLC of aluminum-1100/copper-C10100 two-layer sheets were obtained through numerical simulations and experimental investigations. In order to construct the FLC, two different criterions including the acceleration (i.e., the second order of derivatives) of equivalent plastic strain and major strain were applied to obtain the onset of necking in the materials. Based on these methods, the localized necking would be started when the acceleration of the equivalent plastic strain or the major strain got its maximum value. To verify the numerical predictions, the experimental works were accomplished on the aluminum-1100/copper-C10100 two-layer sheets and a good agreement between the proposed methods and experimental works was observed.

  • Determination of Forming Limit Curve in two-layer metallic sheets using the finite element simulation:
    Proceedings of the Institution of Mechanical Engineers Part L: Journal of Materials: Design and Applications, 2016
    Co-Authors: Ehsan Karajibani, Ramin Hashemi, Mohammad Sedighi
    Abstract:

    Forming Limit Curve (FLC) is a suitable method for determining the metallic sheets formability. The purpose of the present research is to expose a simulation-based approach to predict the FLC in tw...

  • a methodology for determination of extended strain based Forming Limit Curve considering the effects of strain path and normal stress
    Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2015
    Co-Authors: Ramin Hashemi, Karen Abrinia, G Faraji
    Abstract:

    In this paper, an approach based on the modified Marciniak-Kuczynski (M-K) method for computation of an extended strain-based Forming Limit Curve (FLC) is presented. An extended strain-based FLC is built based on equivalent plastic strains and material flow direction at the end of Forming. This Curve has some advantages in comparison with other necking criteria such as the traditional FLC and also the stress-based FLC. This new criterion is much less strain path dependent than the conventional FLC. Furthermore, the use and interpretation of this new Curve is easier than the stress-based FLC. The effect of strain path on the predicted extended strain-based FLC is reexamined. For this purpose, two types of pre-straining on the sheet metal have been imposed. Moreover, the plane stress state assumption is not adopted in the current study. The verifications of the theoretical FLCs are performed by using some available published experimental data.

  • analysis of the extended stress based Forming Limit Curve considering the effects of strain path and through thickness normal stress
    Materials & Design, 2014
    Co-Authors: Ramin Hashemi, Karen Abrinia
    Abstract:

    Abstract In this study, an approach based on the modified Marciniak–Kuczynski (M–K) method for computation of an extended stress-based Forming Limit Curve (FLC) is presented. The extended stress-based FLC is built based on equivalent plastic stress versus mean stress. This Curve has some advantages in comparison with the conventional FLC. This new criterion is much more strain path independent than the conventional FLC. The effect of strain path on the predicted extended stress-based FLC is reexamined. For this purpose, two types of pre-straining on the sheet metal have been loaded. Moreover, the plane stress state assumption is not adopted in the current study. The influence of a through-thickness compressive normal stress is also investigated theoretically. The verifications of the theoretical FLCs are performed by using some available published experimental data.

Karen Abrinia - One of the best experts on this subject based on the ideXlab platform.

  • a methodology for determination of extended strain based Forming Limit Curve considering the effects of strain path and normal stress
    Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2015
    Co-Authors: Ramin Hashemi, Karen Abrinia, G Faraji
    Abstract:

    In this paper, an approach based on the modified Marciniak-Kuczynski (M-K) method for computation of an extended strain-based Forming Limit Curve (FLC) is presented. An extended strain-based FLC is built based on equivalent plastic strains and material flow direction at the end of Forming. This Curve has some advantages in comparison with other necking criteria such as the traditional FLC and also the stress-based FLC. This new criterion is much less strain path dependent than the conventional FLC. Furthermore, the use and interpretation of this new Curve is easier than the stress-based FLC. The effect of strain path on the predicted extended strain-based FLC is reexamined. For this purpose, two types of pre-straining on the sheet metal have been imposed. Moreover, the plane stress state assumption is not adopted in the current study. The verifications of the theoretical FLCs are performed by using some available published experimental data.

  • analysis of the extended stress based Forming Limit Curve considering the effects of strain path and through thickness normal stress
    Materials & Design, 2014
    Co-Authors: Ramin Hashemi, Karen Abrinia
    Abstract:

    Abstract In this study, an approach based on the modified Marciniak–Kuczynski (M–K) method for computation of an extended stress-based Forming Limit Curve (FLC) is presented. The extended stress-based FLC is built based on equivalent plastic stress versus mean stress. This Curve has some advantages in comparison with the conventional FLC. This new criterion is much more strain path independent than the conventional FLC. The effect of strain path on the predicted extended stress-based FLC is reexamined. For this purpose, two types of pre-straining on the sheet metal have been loaded. Moreover, the plane stress state assumption is not adopted in the current study. The influence of a through-thickness compressive normal stress is also investigated theoretically. The verifications of the theoretical FLCs are performed by using some available published experimental data.

Wolfram Volk - One of the best experts on this subject based on the ideXlab platform.

  • influence of non proportional load paths and change in loading direction on the failure mode of sheet metals
    Cirp Annals-manufacturing Technology, 2020
    Co-Authors: Wolfram Volk, R Norz, M Eder, H Hoffmann
    Abstract:

    Abstract Many studies have shown that failure following non-proportional load paths cannot be predicted by a linear Forming Limit Curve (FLC), as the deformation history and a change in loading direction influence the formability and failure mode. In this paper, the different failure modes due to different load paths are investigated, for the first time, by conducting Nakajima tests with pre-formed specimens. The main objective of the investigation is to better understand the influence of pre-Forming and change in loading direction on the formability. To predict this behaviour, regardless of the failure mode, the Generalized Forming Limit Concept (GFLC) is extended.

  • Numerical determination of the onset of local necking using time dependent evaluation method and dynamic material parameters
    Journal of Physics: Conference Series, 2016
    Co-Authors: D. Jocham, Wolfram Volk
    Abstract:

    The Forming Limit Curve (FLC) is a valid instrument for the evaluation of failure in sheet metal processes. However, its experimental evaluation is challenging, in particular for modern lightweight sheet metals, in which the failure occurs without an evident necking transition. Therefore, the numerical analysis can represent a valid alternative for the investigation of the onset of necking phenomena. Prerequisite for realistic failure prediction are an accurate material characterization for high strain levels and a stable and coherent numerical model. Within this paper, an approach for the determination of Forming Limits by using the time dependent evaluation method is investigated and an analysis of the material sensitivity on the simulation results is performed. The results are discussed for mild steel DX56 and first suggestions for the improvement of the simulation input data are derived.

  • failure prediction for nonlinear strain paths in sheet metal Forming
    Cirp Annals-manufacturing Technology, 2012
    Co-Authors: Wolfram Volk, H Hoffmann
    Abstract:

    The Forming Limit Curve (FLC) is a conventional failure criterion to estimate sheet metal formability for proportional loading conditions in Finite Element Analysis. Previous studies found that a standard FLC is not suitable for predicting the influence of nonlinear strain paths. This paper introduces a new method for the description of failure behavior in two-step Forming operations by using a metamodeling technique. The main objectives of this approach are the cost effectiveness of the required experimental calibration and its practical applicability. The predicted Forming Limits determined with the proposed method are presented and validated by experimental results.

  • failure prediction for nonlinear strain paths in sheet metal Forming
    Cirp Annals-manufacturing Technology, 2012
    Co-Authors: Wolfram Volk, H Hoffmann, Joungsik Suh, Jaekun Kim
    Abstract:

    The Forming Limit Curve (FLC) is a conventional failure criterion to estimate sheet metal formability for proportional loading conditions in Finite Element Analysis. Previous studies found that a standard FLC is not suitable for predicting the influence of nonlinear strain paths. This paper introduces a new method for the description of failure behavior in two-step Forming operations by using a metamodeling technique. The main objectives of this approach are the cost effectiveness of the required experimental calibration and its practical applicability. The predicted Forming Limits determined with the proposed method are presented and validated by experimental results.

Jongjin Park - One of the best experts on this subject based on the ideXlab platform.

  • fundamental studies on the incremental sheet metal Forming technique
    Journal of Materials Processing Technology, 2003
    Co-Authors: Jongjin Park, Yungho Kim
    Abstract:

    Abstract The idea of incremental Forming technique has been investigated for production of sheet metal components. With this technique, the Forming Limit Curve (FLC) appears in a different pattern, revealing an enhanced formability, compared to conventional Forming techniques. In the present study, the formability of an aluminum sheet under various Forming conditions was assessed and difficult-to-form shapes were produced with the technique. By utilizing knowledge and experience obtained during the present study, it became possible to produce some free surfaces.

  • the formability of aluminum sheet in incremental Forming
    Journal of Materials Processing Technology, 2001
    Co-Authors: Myoungsup Shim, Jongjin Park
    Abstract:

    Abstract In incremental Forming, the sheet exhibits a unique pattern of the Forming Limit Curve. In the present investigation, a Forming tool containing a freely rotating ball was developed and used to characterize the formability of fully annealed Al 1050 sheet. Various strain paths were applied to the sheet by imposing different tool paths and the major and minor strains of deformed grids around cracks were measured. It was found that the formability of the sheet shows a distinct dependence on the strain path and appears as a straight line in the Forming Limit diagram. The most suitable Forming Limit Curve for incremental Forming was found to be the one that was obtained from a test in which straight paths, with an incremental increase of tool depth, were imposed using a square specimen with the fixed periphery.

K. S. Diao - One of the best experts on this subject based on the ideXlab platform.

  • Experimental and Numerical Determination of Hot Forming Limit Curve of Advanced High-Strength Steel
    Journal of Materials Engineering and Performance, 2017
    Co-Authors: Min Wan, Zhigang Liu, K. S. Diao
    Abstract:

    This paper studied the hot formability of the advanced high-strength steel B1500HS. The hot Nakazima tests were conducted to obtain the Forming Limit Curve (FLC), and the sheet temperatures were recorded to analyze temperature distributions during deformation. Meanwhile, the numerical simulations of hot Nakazima tests were performed to compare with the experimental ones. By utilizing the commercial software, Abaqus, the punch force–displacement Curve, sheet temperature distribution at the time of the maximum punch load and temperature path of the necked element were investigated from both of experiments and numerical simulations. The FLCs from experiment and numerical simulation showed a good agreement. The temperature path of the necked element on each FLC specimen was different due to the numerical stretching time and stress state. This study demonstrated the predictive capability of finite element simulation on hot stamping.