The determination of material strength coefficient and strain hardening constant by inverse method

Lin, Zone‐Ching; Chen, Chang-Cheng; Wang, Hsin-Ho

doi:10.1016/j.jmatprotec.2008.05.039

Cited by 10 publications

(6 citation statements)

References 17 publications

(20 reference statements)

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“…Commonly, in the process of determining material strength coefficient and strain hardening constant, material testing is initially conducted to obtain engineering stress and engineering strain, which are then converted to true stress (σ) and true strain (ϵ). 81 Subsequently, these values are used in the flow stress formula, which can be expressed as σ = Kϵ n , where K represents the material strength coefficient and n represents the strain hardening constant. 82 However, obtaining these parameters involves complex and lengthy calculations.…”

Section: Extensional Rheometrymentioning

confidence: 99%

A pragmatic approach to analyze the ability of ethylene‐octene copolymer in the long chain branching of polypropylene in molten and solid state

Negaresh,

Karbalaei‐Bagher,

Jahani

et al. 2023

SPE Polymers

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The investigation of chain branching in polypropylene (PP) holds significant importance for comprehending the impact of structural modifications on the properties of PP. The utilization of ethylene‐octene copolymer (EOC) presents a valuable opportunity to examine the influence of branching density on the ability of electron beam irradiation or a chemical agent in a PP blend. The introducing long chain branches (LCB) into PP can enhance its mechanical properties, particularly impact strength. This characteristic is of particular significance in applications where the material is subjected to mechanical stress, such as automotive components or packaging materials. Blends of PP/EOC were produced using 20 and 30 wt% of EOC and 0.5 phr trimethylolpropane trimethacrylate (TMPTMA) monomer. To evaluate the efficiency of branching in both solid and molten states, irradiated samples and samples mixed with dicumyl peroxide (DCP) were selected. The rheological properties of the molten blends in shear and extensional modes were assessed, and their morphology was examined using scanning electron microscopy. The existence of LCB in all samples was confirmed through dynamic viscoelastic measurements. It was concluded that although the irradiation promoted chain scission within the backbone, which resulted in long chain branching, DCP created LCB on the backbone chains of PP through chemical reaction in the melt state. Additionally, the strain hardening constant (n) was calculated, and its value for the irradiated sample PP/EOC 80/20 was 0.19, whereas its value for this blend when employing DCP was 0.14. While the complex viscosity of irradiated blend (8764 Pa.s) was greater than that of melt state branched blend (8377 Pa.s) at 0.1 rad/s, in the higher frequencies it became smaller due to the more effective creation of long chain branches through peroxide grafting in the molten state. The results of the study verified the presence of LCB in the materials by observing longer relaxation time and strain hardening behavior.Highlights The chain branching of PP/EOC blends was investigated in both the melt state and solid state through the presence of TMPTMA monomer. The effectiveness of TMPTMA monomer in grafting was mostly notable in the molten state. The steady state viscosity of LCB‐(PP/EOC) was higher in the presence of dicumyl peroxide compared to irradiated PP/EOC. The samples containing 80 wt% of PP exhibited longer side branches compared to the sample with 70 wt% of PP according to shear and extensional rheometry. The induced side chain branches resulting from irradiation and the use of dicumyl peroxide help increase the miscibility of the polymers to a similar extent.

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Section: Extensional Rheometrymentioning

confidence: 99%

A pragmatic approach to analyze the ability of ethylene‐octene copolymer in the long chain branching of polypropylene in molten and solid state

Negaresh,

Karbalaei‐Bagher,

Jahani

et al. 2023

SPE Polymers

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“…As lubrication detoriates due to thinning of the film and extension of the surface, the friction may actually vary during the MLUT. Zone-Ching Lin et al (2009) inversely identified plastic material properties through an upsetting test assuming the change of friction to be known a priori (see also Zone-Ching Lin and Chun-kung Chen, 2006; Zone-Ching Lin and Ven-Huei . However, it is assumed that the frictional shear stress at the surface of the stack is directly and constantly proportional to the normal stress due to the presence of the lubricant.…”

Section: Multi-layered Upsetting Testmentioning

confidence: 99%

“…Cooreman et al, 2008;Lecompte et al, 2009;Endelt and Danckert, 2009;Egan et al, 2007;Zone-Ching Lin et al, 2009). The increasing interest for this new type of test methodology is driven by a number of advantages compared to standard tests.…”

Section: Introductionmentioning

confidence: 99%

Determination of the flow stress and contact friction of sheet metal in a multi-layered upsetting test

Coppieters

Lava

Sol

et al. 2010

Journal of Materials Processing Technology

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“…To investigate the properties of material subjected to the double-compression test, Yanagida and Yanagimoto (2008) used inverse approach for obtaining a flow curve equation. As an inverse approach, estimation using a least-square method is also performed (Lin et al, 2009). The parameter of the work-hardening curve is updated on the basis of changes in the objective function calculated from the analytical value and the experimental value obtained from the compression test.…”

Section: Introductionmentioning

confidence: 99%

Estimation of Work-hardening Curve for Large Strain Using Friction-free Compression Test

Usami

Oya

2014

Procedia Engineering

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Forming simulation has been carried out for prediction of forming limits. Work-hardening curve is deeply involved in the reliability of the forming simulation. Measurement method of large strain region has not been established. In this paper, a new method of determining work-hardening curve of large strain region is proposed. The proposed method consists of compression test and optimization scheme. In the optimization, using the least-square method, the work-hardening curve is determined from the relationship of load and displacement obtained by the compression test and finite element analysis. Jigs are designed to eliminate the effects of friction by constraining the slip between a specimen and jigs. Dumbbell-shaped specimens are designed to prevent re-contact with the jigs. In the experiment, low carbon steel was used as specimens. The proposed method was carried out and the work-hardening curve of large strain region was obtained.

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The determination of material strength coefficient and strain hardening constant by inverse method

Cited by 10 publications

References 17 publications

A pragmatic approach to analyze the ability of ethylene‐octene copolymer in the long chain branching of polypropylene in molten and solid state

A pragmatic approach to analyze the ability of ethylene‐octene copolymer in the long chain branching of polypropylene in molten and solid state

Determination of the flow stress and contact friction of sheet metal in a multi-layered upsetting test

Estimation of Work-hardening Curve for Large Strain Using Friction-free Compression Test

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