Rolling induced size effects in elastic–viscoplastic sheet metals

Nielsen, Kim Lau

doi:10.1016/j.euromechsol.2015.05.006

Cited by 6 publications

(6 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The presented results and observations establish the findings reported in , and Nielsen (2015) as a widespread phenomenon, and show that by exploiting it, results at the rate-independent limit may, in fact, be reached for the present model, which only exists in a rate-dependent framework. It should be made clear, however, that the phenomenon is a purely theoretical concept and, to the best of the authors knowledge, remains to be observed in experiments.…”

Section: Resultssupporting

confidence: 68%

“…The idea of a characteristic rate was first discussed in detail by in relation to conventional rate-dependent steady-state modeling and later exploited in to extract rate-independent results from a scale-dependent steady-state framework. Nielsen (2015) also found similar results for steady-state sheet rolling. Characteristic rates may exist for a wide range of other structural problems, and a broader sense of the phenomenon is demonstrated through the results of the present study.…”

Section: Introductionsupporting

confidence: 73%

See 1 more Smart Citation

Attaining the rate-independent limit of a rate-dependent strain gradient plasticity theory

El-Naaman

Nielsen

Niordson

2016

Extreme Mechanics Letters

Self Cite

View full text Add to dashboard Cite

The existence of characteristic strain rates in rate-dependent material models, corresponding to rate-independent model behavior, is studied within a back stress based rate-dependent higher order strain gradient crystal plasticity model. Such characteristic rates have recently been observed for steady-state processes, and the present study aims to demonstrate that the observations in fact unearth a more widespread phenomenon. In this work, two newly proposed back stress formulations are adopted to account for the strain gradient effects in the single slip simple shear case, and characteristic rates for a selected quantity are identified through numerical analysis. Evidently, the concept of a characteristic rate, within the rate-dependent material models, may help unlock an otherwise inaccessible parameter space.

show abstract

Section: Resultssupporting

confidence: 68%

Section: Introductionsupporting

confidence: 73%

Attaining the rate-independent limit of a rate-dependent strain gradient plasticity theory

El-Naaman

Nielsen

Niordson

2016

Extreme Mechanics Letters

Self Cite

View full text Add to dashboard Cite

show abstract

“…the rolling process is essentially modeled rate-independent (for a rate-dependent study see e.g. [30]).…”

Section: Problem Formulationmentioning

confidence: 99%

Rolling at Small Scales

Nielsen

Niordson

Hutchinson

2015

Journal of Manufacturing Science and Engineering

View full text Add to dashboard Cite

The rolling process is widely used in the metal forming industry, and has been so for many years. However, the process has attracted renewed interest as it recently has been adapted to very small scales where conventional plasticity theory cannot accurately predict the material response. It is well-established that gradient effects play a role at the micron scale, and the objective of this study is to demonstrate how strain gradient hardening affects the rolling process. Specifically, the paper addresses how the applied roll torque, roll forces, and the contact conditions are modified by strain gradient plasticity. Metals are known to be stronger when large strain gradients appear over a few microns; hence the forces involved in the rolling process are expected to increase relatively at these smaller scales. In the present numerical analysis, a steady-state modeling technique that enables convergence without dealing with the transient response period is employed. This allows for a comprehensive parameter study. Coulomb friction, including a stick-slip condition, is used as a first approximation. It is found that length scale effects increase both the forces applied to the roll, the roll torque, and thus the power input to the process. The contact traction is also affected, particularly for sheet thicknesses on the order of 10µm and below. The influences of the length parameter and the friction coefficient are emphasized, and results are presented for multiple sheet reductions and roll sizes.

show abstract

“…In case of friction, an additional traction parallel to the movement should be added to contact interface depending on the direction of sliding relative to the tool. For details relating to the implementation of friction in the context of steady-state solutions please refer to (Nielsen et al, 2016;Nielsen, 2015).…”

Section: Contact Modellingmentioning

confidence: 99%