scholarly journals Strain rate dependent plasticity and fracture of DP1000 steel under proportional and non-proportional loading

2021 ◽  
Author(s):  
Sarath Chandran ◽  
Wenqi Liu ◽  
Junhe Lian ◽  
Sebastian Münstermann ◽  
Patricia Verleysen
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Stress State ◽  
Strain Rate ◽  
Dynamic Strain ◽  
Loading Path ◽  
Strain Rates ◽  
Fracture Surfaces ◽  
Stress States ◽  
Scanning Electron

To assess the effect of stress state and strain rate on damage and fracture of a commercial DP1000 steel with a very fine microstructure, an extensive series of tests were performed. Using finite element simulations, eight different sample geometries, including a dogbone, a central hole, a shear and several notched samples, were designed to achieve both proportional and non-proportional stress states using conventional test benches. Tested at quasi-static, intermediate and, dynamic deformation rates, in total 175 tests were performed. Local strain fields were obtained by digital image correlation. A correction procedure was worked out to eliminate the influence of thermal softening. After testing, scanning electron microscopy was employed to analyse the fracture surfaces. Tests and fractography allowed to draw systematic conclusions on the response of the DP1000 steel. A two-stage strain rate sensitivity of strength is found with a gradually increasing slope at low strain rates and a much steeper rise at high strain rates, which is further amplified at higher triaxiality stress states. The experimentally derived fracture loci revealed a dominant, detrimental impact of the stress triaxiality that is most pronounced at intermediate strain rates. A remarkable, non-monotonic evolution of the fracture strain with strain rate is observed: the highest values were obtained at intermediate rates. Scanning electron microscopy images of the fracture surfaces indicate a void-assisted ductile fracture, though with the occurrence of brittle features triggered at dynamic strain rates. Fracture morphology and dimple features are heavily dependent on stress state, strain rate and loading path.

Uniaxial and biaxial compressive response of a bulk metallic glass composite over a range of strain rates and temperatures

2009 ◽  
Vol 24 (1) ◽  
pp. 66-78 ◽  
Author(s):  
M. Martin ◽  
L. Meyer ◽  
L. Kecskes ◽  
N.N. Thadhani
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Metallic Glass ◽  
Strain Rate ◽  
Bulk Metallic Glass ◽  
Inductive Heating ◽  
Strain Rates ◽  
Drop Weight ◽  
Split Hopkinson ◽  
Scanning Electron

The uniaxial and biaxial compressive responses of Zr57Nb5Al10Cu15.4Ni12.6–W composite were investigated over a range of strain rates (∼10−3 to 103 s−1) using an Instron universal testing machine (∼10−3 to 10° s−1), drop-weight tower (∼200 s−1), and split Hopkinson pressure bar (103 s−1). The temperature dependence of the mechanical behavior was investigated at temperatures ranging from room temperature to 600 °C using the instrumented drop-weight testing apparatus, mounted with an inductive heating device. The deformed and fractured specimens were examined using optical and scanning electron microscopy. Stopped experiments were used to investigate deformation and failure mechanisms at specified strain intervals in both the drop weight and split Hopkinson bar tests. These stopped specimens were also subsequently examined using optical and scanning electron microscopy to observe shear band and crack formation and development after increasingly more strain. The overall results showed an increase in yield strength with strain rate and a decrease in failure strength, plasticity, and hardening with strain rate. Comparison of uniaxial and biaxial loading showed strong susceptibility to shear failure since the additional 10% shear stress caused failure at much lower strains in all cases. Results also showed a decrease in flow stress and plasticity with increased temperature. Also notable was the anomalous behavior at 450 °C, which lies between the Tg and Tx and is in a temperature regime where homogeneous flow, as opposed to heterogeneous deformation by shear banding, is the dominant mechanism in the bulk metallic glass.

Effect of Nanocellulose Loading on Tensile Properties of Nitrile Rubber

2017 ◽  
Vol 264 ◽  
pp. 112-115
Author(s):  
Erfan Suryani Abdul Rashid ◽  
Wageeh Abdulhadi Yehye ◽  
Nurhidayatullaili Muhd Julkapli ◽  
Sharifah Bee O.A. Abdul Hamid
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Scanning Electron Microscopy ◽  
Tensile Strength ◽  
Tensile Test ◽  
Tensile Properties ◽  
Mechanical Performance ◽  
Butadiene Rubber ◽  
Fracture Surfaces ◽  
Scanning Electron

Nanocellulose (NCC) is incorporated into nitrile butadiene rubber (NBR) latex with the composition 0 to 5 phr using dipping method. Mechanical properties of NBR/NCC composites using tensile test was used to characterize their mechanical performance and the fracture surfaces post tensile test were studied. The tensile strength of NBR/NCC composites increase significantly with the addition of nanocellulose. This could be anticipated due to the presence of Van der Waals interaction between hydrophilic natures of nanocellulose with hydrophobic of NBR consequently limits the tearing propagation. The result was supported with the fracture surfaces morphology viewed under Fourier Emission Scanning Electron Microscopy (FESEM).

scholarly journals Influence of Indentation on the Fatigue Strength of Carbonitrided Plain Steel

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Jiewei Gao ◽  
Guangze Dai ◽  
Junwen Zhao ◽  
Hengkui Li ◽  
Lei Xu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Fatigue Strength ◽  
Fatigue Limit ◽  
Compound Layer ◽  
Indentation Size ◽  
Fracture Surfaces ◽  
Significant Difference ◽  
Scanning Electron

To study the influence of indentation on the fatigue strength of untreated and carbonitrided specimens of S38C steel, the fatigue limit of specimens with and without indentations was tested. Fracture surfaces were observed using scanning electron microscopy (SEM). The results show that the fatigue strength of the untreated specimen decreases with increasing dimension of indentation, without significant difference compared to the predicted results. Compared to the fatigue limit of the untreated specimen, those of the carbonitrided specimen and the carbonitrided specimen whose compound layer was polished were improved by 12% and 40%, respectively. The fatigue strength of the carbonitrided specimen decreased sharply with increasing indentation size because of the presence of microcracks in the compound layer. When the compound layer was removed, the fatigue limit was observed to be less sensitive to indentation than that of the carbonitrided specimen.

Investigations of strain rate, size, and crack length effects on the mechanical response of polycaprolactone electrospun membranes

2021 ◽  
pp. 095440892110240
Author(s):  
Ferdi C Bayram ◽  
Mehmet F Kapçı ◽  
Adile Yuruk ◽  
Ismail A Isoglu ◽  
Burak Bal
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Strain Rate ◽  
Crack Length ◽  
Crack Growth ◽  
Mechanical Response ◽  
Electrospinning Technique ◽  
Strain Rate Effects ◽  
Electrospun Membranes ◽  
Scanning Electron

The effects of strain rate, size (height × width), and pre-existing crack length on the mechanical response of polycaprolactone electrospun membranes were investigated by tension tests conducted at room temperature. In particular, tensile tests were performed with three different strain rates for strain rate effect tests, seven different geometries for elucidating the size effect, and three different initial notch lengths for crack growth experiments. The electrospun membranes were produced by the electrospinning technique using a polycaprolactone solution prepared in 1, 1, 1, 3, 3, 3-hexafluoro-2-propanol as the solvent. Scanning electron microscopy was utilized to show the continuous fiber structure without bead formation. The average fiber diameter was calculated as 1.113 ± 0.270 μm by using scanning electron microscopy images of the membranes. The chemical structure of polycaprolactone was analyzed by Fourier transform infrared spectroscopy, and the toxicity and cell viability of the electrospun membranes were shown by CellTiter 96® Aqueous One Solution Cell Proliferation Assay (MTS test). It was observed that the ultimate tensile strength and Young’s modulus decreased, and the elongation at failure value increased as the strain rate decreased from 10−1 to 10−3 s−1. Besides, positive strain rate sensitivity was observed on the mechanical response of electrospun polycaprolactone membranes. Moreover, the dependency of mechanical response on the size geometry has been well studied, and the optimum height and width combinations were specified. Also, crack growth was studied in terms of both macroscopic and microstructural deformation mechanisms and it is observed that individual fiber deformations and interactions are highly effective on the mechanical behavior and also propagation of the crack. Consequently, in this study, the size and strain rate effects and crack growth on the mechanical response of electrospun polycaprolactone membranes have been investigated extensively, and the results presented herein constitute an essential guideline for the usage of polycaprolactone electrospun membranes at different loading scenarios.

Correlative Fractography: Combining Scanning Electron Microscopy and Light Microscopes for Qualitative and Quantitative Analysis of Fracture Surfaces

2013 ◽  
Vol 19 (2) ◽  
pp. 496-500 ◽  
Author(s):  
Luis Rogerio de Oliveira Hein ◽  
José Alberto de Oliveira ◽  
Kamila Amato de Campos
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Quantitative Analysis ◽  
New Method ◽  
Fracture Mechanisms ◽  
Stereo Pair ◽  
Qualitative And Quantitative Analysis ◽  
Qualitative And Quantitative ◽  
Fracture Surfaces ◽  
Scanning Electron

AbstractCorrelative fractography is a new expression proposed here to describe a new method for the association between scanning electron microscopy (SEM) and light microscopy (LM) for the qualitative and quantitative analysis of fracture surfaces. This article presents a new method involving the fusion of one elevation map obtained by extended depth from focus reconstruction from LM with exactly the same area by SEM and associated techniques, as X-ray mapping. The true topographic information is perfectly associated to local fracture mechanisms with this new technique, presented here as an alternative to stereo-pair reconstruction for the investigation of fractured components. The great advantage of this technique resides in the possibility of combining any imaging methods associated with LM and SEM for the same observed field from fracture surface.

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