An improved strain gradient approach for determination of deformation localization and forming limit diagrams

Assempour, Ahmad; Safikhani, Azim; Hashemi, Ramin

doi:10.1016/j.jmatprotec.2008.04.030

Cited by 18 publications

(7 citation statements)

References 29 publications

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“…3. Using strain gradient theory: 38,39 in this method, the strain gradient theory of plasticity is incorporated into the M-K method to compute the FLD. It has been shown that variations of the initial in-homogeneity factor have a negligible effect on the FLD.…”

Section: Resultsmentioning

confidence: 99%

Forming limit diagram of tubular hydroformed parts considering the through-thickness compressive normal stress

Hashemi

Abrinia

Assempour

et al. 2014

Proceedings of the Institution of Mechanical Engineers, Part L:

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In this study, the effect of a compressive normal stress has been considered in the determination of forming limit diagrams and forming limit stress diagrams to predict neck initiation failure in tube hydroforming of T-shaped parts. Computation of the forming limit diagrams and FLSDs is based on the generalized Marciniak and Kuczynski method to consider the existence of through-thickness compressive normal stress. The proposed forming limit diagrams and FLSDs were used in conjunction with ABAQUS/EXPLICIT finite element simulations to predict the onset of necking in tube hydroforming of T-shaped part. The amount of calibration pressure and axial feeding required to produce an acceptable part in finite element method was compared to published experimental data, and a satisfactory agreement between the FEM and test results has been achieved. Therefore, the present approach can be used as a reliable criterion to design tube hydroforming processes and reduce the number of costly trials.

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Section: Resultsmentioning

confidence: 99%

Forming limit diagram of tubular hydroformed parts considering the through-thickness compressive normal stress

Hashemi

Abrinia

Assempour

et al. 2014

Proceedings of the Institution of Mechanical Engineers, Part L:

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“…The initial inhomogeneity factor of the groove f 0 is defined as the thickness ratio f 0 = t B0 /t A0 , where t represents the thickness and subscript "0" represents the initial state. This initial inhomogeneity grows continuously with plastic straining to form a localized neck eventually [19]. During the deformation process, the strain ratio ρ(ρ = ε 2 /ε 1 ) outside the groove is constant, but decreases in the groove region.…”

Section: The Forming Limit Curve At An Elevated Temperaturementioning

confidence: 99%

Prediction and Experiment of Fracture Behavior in Hot Press Forming of a TA32 Titanium Alloy Rolled Sheet

Fan

Chen

et al. 2018

Metals

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In aerospace and automotive industries, hot press forming (HPF) technology is widely used for rapid and precise deformation of the complex sheet metal component, where the fracture behavior has always been a focused problem. In this study, the hot tensile test and the Nakazima test were carried out, in order to establish the Misiolek constitutive equation and determine the forming limit strain points at an elevated temperature, respectively. The microstructure evolution during the tensile test was also investigated by optical microscope. In addition, the Marciniak–Kuczynski (M–K) model, considering the Mises, Hill48, and Logan–Hosford yield criteria, was utilized to calculate the theoretical forming limit curve (FLC). Furthermore, the fracture behavior of the TA32 alloy sheet during the HPF process was accurately predicted by inserting the predicted FLC into finite element simulation, and the qualified complex component was obtained by optimizing the shape of the sheet.

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“…The initial imperfection factor of the groove f 0 is defined as the thickness ratio f 0 = t 0b /t 0a , where t denotes the thickness and subscript '0' denotes the initial state. This initial inhomogeneity grows continuously with plastic straining to form eventually a localized neck [21]. The groove region is called 'b' and the safe zone is named 'a'.…”

Section: Fld Predictionmentioning

confidence: 99%

“…In fact, deformation in the groove region gradually approaches the plane strain. In practice, this type of groove can be caused by surface roughness or local thickness variation, which could be formed before the process [21]. Usually sheet metal forming can be assumed as a plane stress, so the strain and stress increments in the groove can directly be obtained with respect to the safe zone strain increments and vice versa.…”

Section: Fld Predictionmentioning

confidence: 99%

A new concept in obtaining a forming limit diagram of tailor welded blanks

Menhaj

Abbasi

Sedighi

et al. 2011

The Journal of Strain Analysis for Engineering Design

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Nowadays, tailor welded blanks (TWBs) have a great role to play in saving of cost, vehicle weight, and fuel consumption in automobile industries. A TWB constitutes blanks with different thicknesses and/or coatings and/or mechanical properties welded together prior to the stamping process. Owing to low formability of TWBs, determining and predicting the forming limit diagram (FLD) of these blanks enables manufacturers to produce non-imperfection parts. In this research, a modified type of Marciniak-Kuczynski (M-K) model was applied to determine the FLD of a TWB consisting of interstitial free (IF) galvanized steel sheet with different thicknesses (0.8 and 1.2 mm). Also, the effect of three yield criteria, namely Hill48, Hosford79, and BBC2002, on the predicted FLDs was investigated. During the analyses, the materials were assumed to follow the Hollomon work hardening rule. The experimental FLDs were determined utilizing the Hecker method. It was observed that the proposed method can properly predict the experimental FLD of a TWB with longitudinal welds and thickness ratios (TRs) greater than one, if proper parameters are being selected. Furthermore, the best prediction took place when the BBC2002 yield criterion was applied.

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An improved strain gradient approach for determination of deformation localization and forming limit diagrams

Cited by 18 publications

References 29 publications

Forming limit diagram of tubular hydroformed parts considering the through-thickness compressive normal stress

Forming limit diagram of tubular hydroformed parts considering the through-thickness compressive normal stress

Prediction and Experiment of Fracture Behavior in Hot Press Forming of a TA32 Titanium Alloy Rolled Sheet

A new concept in obtaining a forming limit diagram of tailor welded blanks

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