Four-point-bending device for bending moment controlled cyclic reverse loading on plate materials and its application on AZ31B magnesium sheets

Denk, Josef; Dallmeier, Johannes; Huber, Otto

doi:10.1016/j.ijfatigue.2017.12.011

Cited by 7 publications

(2 citation statements)

References 32 publications

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“…Each work uses different approaches to determine the positive elastic strain energy density and achieves a good agreement between the predicted and experimental life for uniaxial unnotched specimens. Only a few investigations were carried out concerning the fatigue modeling of notched specimens [8,30,32], bending specimens [7,15,28] and the fatigue behavior under dominant multiaxial loading [1,24]. The mentioned researches investigate the influence of stress concentrations, stress gradients and different types of loading on fatigue life separately from each other and achieve good results in fatigue modeling for a specific specimen type (uniaxial unnotched specimen, notched specimen, bending specimen, axial and torsional loaded tubular specimen).…”

Section: Introductionmentioning

confidence: 99%

Fatigue modeling for wrought magnesium structures with various fatigue parameters and the concept of highly strained volume

Nischler

Denk

Huber

2020

Continuum Mech. Thermodyn.

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Mechanical fatigue tests of unnotched, notched, and bending twin-roll cast AZ31B magnesium alloy specimens are performed in which strain fields are analyzed with digital image correlation. Clearly, delimited macroscopic bands of twinned grains (BTGs) in which the compressive strain is significantly higher compared to the adjacent regions are observed. Conventional fatigue parameters, e.g., the strain amplitude, exhibited higher values within the BTGs. This findings are confirmed by the fact that for all investigated specimens the initial macroscopic cracks are observed within the BTGs. Consequently, for the presented concept of highly strained volume, fatigue parameters are determined from the highly strained regions with high strain amplitudes. This paper focuses on the application of the effective strain amplitude fatigue parameter decomposed in an elastic and plastic portion, the Smith-Watson-Topper fatigue parameter and energy-based fatigue parameters within the concept of highly strained volume. An extended stress-strain hysteresis model is presented to compute stress-strain hystereses for arbitrary load ratios, required to determine the mentioned fatigue parameters. The application and evaluation of five different fatigue parameters within the concept of highly strained volume demonstrates the accurate description of the fatigue life until failure.

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Section: Introductionmentioning

confidence: 99%

Fatigue modeling for wrought magnesium structures with various fatigue parameters and the concept of highly strained volume

Nischler

Denk

Huber

2020

Continuum Mech. Thermodyn.

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“…The moment-strain relations were validated with those of numerically calculated moment-strain relations for the bending process with pre-determined tensile test data. In [9] Denk et al proposed an in-plane bending setup for cyclic fatigue testing. The strains were measured using digital image correlation (DIC).…”

Section: Introductionmentioning

confidence: 99%

A New in-Plane Bending Test to Determine Flow Curves for Materials with Low Uniform Elongation

et al. 2020

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Background Flow curves can easily be obtained by uniaxial tensile tests, but strains are then limited by diffuse necking. For many applications, the flow stress must be known above this limit. Objective The main objective of this paper is to obtain flow curves for material with low uniform elongation to relatively high strains compared to a uniaxial tensile test. Method A novel in-plane sheet bending experiment and stress evaluation procedure is presented. The developed bending device can be mounted in a tensile test machine and can produce very high bending curvatures compared to previously proposed pure bending setups. The bending angle and curvature are obtained by image processing and the bending moment is calculated directly from the force measured from the tensile test machine and the bending angle. The moment–curvature relation is used to determine the uniaxial stress–strain relation using an analytical approach, without presuming any hardening model. The bending process and the analytical procedure are validated by a numerical simulation as well as by experiments. Results The numerical validation shows good agreement between the stress–strain curve obtained from the bending process and that of the uniaxial input flow curve up to 12% strain. Experimentally the model is validated by comparing the stress–strain curve obtained from the bending test with the results directly obtained from a tensile test for mild steel. Good agreement is observed up to 12% strain. As an application example, bending tests were performed on a martensitic steel (MS) with low uniform strain (less than 3%). For this material, flow curves could be obtained up to relatively high strains (~12%), compared to a tensile test. Conclusion This bending test setup allows to study materials with low uniform elongation up to significantly higher strains than are readily obtained in a tensile test.

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Concept of the highly strained volume for fatigue modeling of wrought magnesium alloys

Denk

Whitmore

Huber

et al. 2018

International Journal of Fatigue

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Four-point-bending device for bending moment controlled cyclic reverse loading on plate materials and its application on AZ31B magnesium sheets

Cited by 7 publications

References 32 publications

Fatigue modeling for wrought magnesium structures with various fatigue parameters and the concept of highly strained volume

Fatigue modeling for wrought magnesium structures with various fatigue parameters and the concept of highly strained volume

A New in-Plane Bending Test to Determine Flow Curves for Materials with Low Uniform Elongation

Concept of the highly strained volume for fatigue modeling of wrought magnesium alloys

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