Transient Stress Relaxation Test to Identify Material Constants in Dislocation Density Model

Balaji, Vikram; Kumar, Sunil; Hariharan, K.; Digavalli, Ravi Kumar; Lee, Myong Gyu; Barlat, Frédéric

doi:10.1007/s11661-022-06624-2

Cited by 5 publications

(5 citation statements)

References 88 publications

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“…Higher value of β is observed in as-received sample compared to the CGP-processed sample due to higher activation volume (Figure 4). The mobile dislocation density reduces and forest (immobile) dislocation density increases with increasing relaxation numbers 13,49,50 evidenced by decreasing values of β in the CGP-processed samples. Whereas the variation in β values with relaxation numbers is reversed in an as-received condition which shows the dominant increase in internal stresses due to Table 1.…”

Section: Resultsmentioning

confidence: 94%

“…22,25 Also, these results can be validated with the tendency of higher postuniform elongation in engineering stressstrain behavior of CGP-processed low-carbon steel samples. 4,46 From different literature, 46,49,[55][56][57][58][59] Figure 6(a) shows the variation of grain size and activation volume with the number of passes for different metals and alloys processed through CGP. The coarse-grained initial materials are significantly refined after the first pass and reduced to a submicrometer though the rate of grain refinement is decreased in the later passes.…”

Section: Resultsmentioning

confidence: 99%

“…(a) The variation of grain size and activation volume with pass numbers for different materials 46,49,55–59 and current work. (b) Comparison of crystallite (grain) size 46,62 and activation volume.…”

Section: Resultsmentioning

confidence: 99%

“…From different literature, 46,49,55–59 Figure 6(a) shows the variation of grain size and activation volume with the number of passes for different metals and alloys processed through CGP. The coarse-grained initial materials are significantly refined after the first pass and reduced to a submicrometer though the rate of grain refinement is decreased in the later passes.…”

Section: Resultsmentioning

confidence: 99%

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Re-examination and comparison of activation volume, strain rate sensitivity, and dislocation density for coarse grain and CGP-processed UFG materials

Kumar

2023

Proceedings of the Institution of Mechanical Engineers, Part L:

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The frequently used metallurgical parameters such as activation volume, internal stress, strain rate sensitivity, and dislocation density are identified in ultrafine-grained (UFG) materials through erudite analytical relations. It is difficult to analyze such parameters optically since the material consists of highly distorted and inhomogeneous microstructure due to the large strain imposed during the constrained groove pressing (CGP) process. Hence, transient tests like stress relaxation tests are advantageous over the optical to use. Apart from the identification of parameters in low-carbon steel materials using uniaxial loading and stress relaxation tests, the relationship between the parameters is nobly investigated in as-received and UFG structure samples produced through the CGP process. In the relationship, the exponential-power law constitutive to describe the accurate stress–strain curves, identification of mobile and forest dislocation density during strain hardening, and exponential variation between grain size and activation volume are proposed. The replenishment or exhaustion of mobile and forest dislocation density significantly affects the metallurgical parameters during uniaxial tensile loading followed by stress relaxation testing. In this experimental and analytical work, the CGP process produces a UFG material that has lower activation volume and higher stress drop, mobile dislocation density, forest dislocations density, strain rate sensitivity, and internal stress.

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Re-examination and comparison of activation volume, strain rate sensitivity, and dislocation density for coarse grain and CGP-processed UFG materials

Kumar

2023

Proceedings of the Institution of Mechanical Engineers, Part L:

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“…In a recent work [35], the authors have demonstrated that the dislocation density can be related to formability characterised by local necking. The objective of this study is to look at the possibility of obtaining a unique fracture locus using dislocation density as a variable.…”

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confidence: 99%

A new path-independent variable to model ductile damage

Hariharan

Balaji

Bharti

2023

Materials Science and Technology

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The effective plastic strain is a commonly used damage variable within continuum damage framework. The value of effective plastic strain at fracture, however, depends on strain rate, temperature and strain path. An alternate state variable is proposed in this work that can provide a unique path-independent2 fracture locus. The average dislocation density is a microstructure-based state variable and has been established in the past to describe the constitutive behaviour of plastic deformation. It is demonstrated that when the average dislocation density is used to model fracture initiation, the fracture locus is unique over a range of strain rates, unlike the conventionally used fracture strain.

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Modelling time-dependent relaxation behaviour using physically based constitutive framework

Balaji,

Krishnaswamy,

Natarajan

et al. 2024

International Journal of Mechanical Sciences

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Transient Stress Relaxation Test to Identify Material Constants in Dislocation Density Model

Cited by 5 publications

References 88 publications

Re-examination and comparison of activation volume, strain rate sensitivity, and dislocation density for coarse grain and CGP-processed UFG materials

Re-examination and comparison of activation volume, strain rate sensitivity, and dislocation density for coarse grain and CGP-processed UFG materials

A new path-independent variable to model ductile damage

Modelling time-dependent relaxation behaviour using physically based constitutive framework

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