Full-Field Strain Measurement in Multi-stage Shear Cutting: High-Speed Camera Setup and Variational Motion Estimation

Hartmann, Christoph; Volk, Wolfram

doi:10.1007/978-3-030-75381-8_134

Cited by 3 publications

(4 citation statements)

References 23 publications

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“…The following derivations and explanations were built on the results given in the respective references; see [12,15,25]. The results obtained using the proposed approach have already been published (see [2,26]), which supports its practical relevance. This paper contributes the mathematical derivation, technical background, and careful evaluation of the method.…”

Section: State-of-the-artmentioning

confidence: 74%

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Spatio-Trajectorial Optical Flow for Higher-Order Deformation Analysis in Solid Experimental Mechanics

Bauer

Hartmann

2023

Sensors

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Material models are required to solve continuum mechanical problems. These models contain parameters that are usually determined by application-specific test setups. In general, the theoretically developed models and, thus, the parameters to be determined become increasingly complex, e.g., incorporating higher-order motion derivatives, such as the strain or strain rate. Therefore, the strain rate behaviour needs to be extracted from experimental data. Using image data, the most-common way in solid experimental mechanics to do so is digital image correlation. Alternatively, optical flow methods, which allow an adaption to the underlying motion estimation problem, can be applied. In order to robustly estimate the strain rate fields, an optical flow approach implementing higher-order spatial and trajectorial regularisation is proposed. Compared to using a purely spatial variational approach of higher order, the proposed approach is capable of calculating more accurate displacement and strain rate fields. The procedure is finally demonstrated on experimental data of a shear cutting experiment, which exhibited complex deformation patterns under difficult optical conditions.

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Section: State-of-the-artmentioning

confidence: 74%

“…The results in a practical application already showed the power of the proposed methods; see [2,26]. It was even possible to go beyond robust strain rate computation, evaluating deformation curvatures and their rates, which are variables relevant for advanced modelling approaches in mechanics, such as strain gradient plasticity.…”

Section: Discussionmentioning

confidence: 87%

Spatio-Trajectorial Optical Flow for Higher-Order Deformation Analysis in Solid Experimental Mechanics

Bauer

Hartmann

2023

Sensors

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“…The aim of this work is to investigate the energy-based variational model in the context of in situ measured displacement field data, which are readily available for a wide range of experiments and processes [ 28 , 29 ]. This becomes even more important with the increasing accuracy and precision of full-field optical measurement techniques [ 30 , 31 , 32 , 33 ].…”

Section: Objectivementioning

confidence: 99%

“…Its popularity is due to its stability and improved accuracy compared to the forward or backward Euler methods [63] (pp. [29][30][31]237). Again, in considering the approximate nature of Equation (82), Θ = 0.5 does not exactly yield a Crank-Nicolson approach.…”

Section: Alternative Approachmentioning

confidence: 99%

Plasticity-Induced Heating: Revisiting the Energy-Based Variational Model

Hartmann,

Obermeyer

2024

Materials

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Temperature evolution during plastic deformation is of great importance for the design of manufacturing processes, as well as for the analysis and prediction of tool wear. However, the results from experimental- and numerical-type research are still often contradictory. In this paper, we analyze methods for estimating plasticity-induced heating directly from displacement fields that can be recorded during experiments or extracted from simulation results. In terms of computational methodology, the thermodynamically motivated energy-based variational formulation of the coupled thermo-mechanical boundary-value problem is adapted to the problem at hand. Since an analysis of this variational formulation exhibits challenges and distinct inconsistencies with respect to the problem at hand, an alternative approach is proposed. This alternative approach is essentially a purely thermal finite element simulation, and it is conducted using a heat source term that is empirically based on the fraction of irreversible deformation work converted to heat. Our approach estimates plasticity-induced heating based on the strain and strain rate data derived from displacement fields. We therefore incorporate thermo-visco-plastic constitutive behavior (Johnson–Cook) with a thermodynamically motivated model that specifies the fraction of plastic work converted to heat (the Taylor–Quinney coefficient).

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Application of Fractal Image Analysis by Scale-Space Filtering in Experimental Mechanics

2022

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Increasingly complex numerical analyses require more and more precise, accurate and varied input parameters in order to achieve results that are as realistic and reliable as possible. Therefore, experimental analyses for material parameter identification are of high importance and a driving force for further developments. In this work, opportunities by applying fractal analysis to optical measurement data of a shear cutting process are investigated. The fractal analysis is based on a modification of the concept of scale-space filtering. Scale exponent fields are calculated for the image sequences of the shear cutting process that are taken by a mobile microscope. A least-square approximation is used for the automated evaluation of the local scale exponent values. In order to determine the change of the scale exponent of individual material points, a digital image correlation is applied.

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Full-Field Strain Measurement in Multi-stage Shear Cutting: High-Speed Camera Setup and Variational Motion Estimation

Cited by 3 publications

References 23 publications

Spatio-Trajectorial Optical Flow for Higher-Order Deformation Analysis in Solid Experimental Mechanics

Spatio-Trajectorial Optical Flow for Higher-Order Deformation Analysis in Solid Experimental Mechanics

Plasticity-Induced Heating: Revisiting the Energy-Based Variational Model

Application of Fractal Image Analysis by Scale-Space Filtering in Experimental Mechanics

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