Digital image correlation shows localized deformation bands in inelastic loading of fibrolamellar bone

2009 ◽  
Vol 24 (2) ◽  
pp. 421-429 ◽  
Author(s):  
Gunthard Benecke ◽  
Michael Kerschnitzki ◽  
Peter Fratzl ◽  
Himadri S. Gupta
Keyword(s):  
Plastic Strain ◽  
Tensile Deformation ◽  
Image Correlation ◽  
Correlation Technique ◽  
Length Scale ◽  
Strain Rates ◽  
Deformation Bands ◽  
Localized Deformation ◽  
High Deformation ◽  
Multiple Regions

Irreversible or plastic deformation in bone is associated with both permanent plastic strain as well as localized microdamage. Whereas mechanisms at the molecular and mesoscopic level have been proposed to explain aspects of irreversible deformation, a quantitative correlation of mechanical yielding, microstructural deformation, and macroscopic plastic strain does not exist. To address this issue, we developed and applied a two-dimensional image correlation technique to the tensile deformation of bovine fibrolamellar bone, to determine the spatial distribution of strain fields at the length scale of 10 μm to 1 mm in bone during irreversible tensile deformation. We find that tensile deformation is relatively homogeneous in the elastic regime and starts at the yield point, showing regions of locally higher strain. Multiple regions of high deformation can exist at the same time over a length scale of 1 to 10 mm. Macroscopic fracture always occurs at one of the locally highly deformed regions, but the selection of which region cannot be predicted. Locally, strain rates can be enhanced by a factor of 3 to 10 over global strain rates in the highly deformed zones and are lower but always positive in all other regions. Light microscopic imaging shows the onset of structural “banding” in the regions of high deformation, which is most likely correlated to microstructural damage at the inter- and intrafibrillar level.

Development of a Time-Resolved Catadioptric Stereo Digital Image Correlation Technique for the Study of Blast Loading of Composite Material Structures

2011 ◽  
Author(s):  
Douglas Jahnke ◽  
Yiannis Andreopoulos
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Strain ◽  
Blast Loading ◽  
Image Correlation ◽  
Time Dependent ◽  
Correlation Technique ◽  
Strain Rates ◽  
Flat Plates ◽  
High Strain Rates

Impingement of blast or shock waves on structures is characterized by a substantial transient aerodynamic load that develops over the short time associated with the shock reflection time scale. This mutual interaction between the shock wave and the structure can cause significant deformation of the structure and high strain rates within the material resulting in damage. While accelerometers, strain gages and other single point measurement probes and their corresponding techniques can provide valuable information of the local displacement and strain during blast loading, better understanding of the complex phenomena involved in these interactions require time dependent information acquired simultaneously from multi points on the structure. Digital Image Correlation is a full-field noncontact optical technique which can provide time dependent information of the displacement of the structure and the resultant high strain rates generated during the loading. The present setup consists of a single high-frame-rate camera which can accommodate two simultaneous stereo images of the deforming structure on its CMOS chip. Four different planar mirrors, appropriately positioned, provide the stereo views of the specimen captured on the chip. The present layout offers several advantages over traditional systems with two different cameras. First, it provides identical system parameters for the two views which minimizes their differences and thus facilitating robust stereo matching. Second, it reduces calibration time since only one camera is used and third its cost is substantially lower than the cost of a system with two cameras. The technique is being developed and tested in a large scale shock tube facility during loading by shock/blast wave of various impulses. The specimens used are flat plates made of high-alloy steel, aluminum or composite materials. In the present paper the development of the technique will be described and preliminary results of qualification tests will be presented and discussed.

scholarly journals Effect of Discontinuous Yielding on the Strain Hardening Behavior of Fine-Grained Twinning-Induced Plasticity Steel

2021 ◽  
Vol 8 ◽  
Author(s):  
Singon Kang ◽  
Sujin Jeong ◽  
Yeon-Sang Ahn
Keyword(s):  
Strain Hardening ◽  
Tensile Deformation ◽  
Early Stage ◽  
Image Correlation ◽  
Localized Deformation ◽  
Fine Grained ◽  
Cooling Conditions ◽  
Strain Hardening Behavior ◽  
Strain Hardening Rate

The yielding of a high Mn twinning-induced plasticity steel was examined in three fine-grained specimens recrystallized at 700°C for 5 min with different cooling conditions. While the stress-strain curves of furnace-cooled and air-cooled specimens exhibit a stress drop at yielding, the drop was not observed in the water-quenched specimen. A simple analysis of the displacement data indicates the occurrence of localized deformation at the beginning of the plastic deformation in the three tensile specimens with different cooling conditions. The localized deformation of all three specimens was confirmed as Lüders strain by digital image correlation (DIC) analysis. Based on this observation, the role of yielding behavior on the strain hardening rate evolution at an early stage of the tensile deformation was discussed.

scholarly journals Thermomechanical response of Mg AZ31 at different levels of temperatures and strain rates

2019 ◽  
Vol 304 ◽  
pp. 01025
Author(s):  
Farid Abed ◽  
Wael Abuzaid ◽  
Yomna Morad
Keyword(s):  
True Strain ◽  
Weight Ratio ◽  
High Strength ◽  
Tensile Tests ◽  
Industrial Applications ◽  
Gauge Length ◽  
Image Correlation ◽  
Strain Rates ◽  
Localized Deformation ◽  
The Difference

Magnesium alloys’ mechanical behavior has received increasing attention because of its high strength to weight ratio making them ideal for various industrial applications, such as vehicle components, transportation and aerospace. The objective of this work is to closely investigate the thermo-mechanical properties of magnesium alloy AZ31 at different strain rates and temperatures. Tensile tests are conducted on a 30 mm gauge length MgAZ31 specimens at two quasi-static strain rates (1.11x10−3 s−1 and 0.28 s−1) at a range of temperatures between 25 ºC and 250 ºC. Digital Image Correlation (DIC) system was used to calculate the true strain and provide quantitative assessment of the localized deformation response at high levels of deformation. The stress-strain responses of MgAZ31 show that the yield stress as well as the ultimate stress decreases as temperature increases and strain rate decreases. Moreover, the difference between the yield and ultimate stresses at both strain rates increases rapidly as temperature increases. The material shows a significant increase in ductility as temperature increases while the modulus of elasticity remains independent of change in strain rates.

scholarly journals Mechanical characterization and numerical modeling of TPMS lattice structures subjected to impact loading

2021 ◽  
Vol 250 ◽  
pp. 02005
Author(s):  
Rafael Santiago ◽  
Sarah Almahri ◽  
Dong-Wook Lee ◽  
Haleimah Alabdouli ◽  
Omar Banabila ◽  
...  
Keyword(s):  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
High Energy ◽  
Image Correlation ◽  
Dynamic Strain ◽  
Correlation Technique ◽  
Fe Model ◽  
Strain Rates ◽  
The Impact ◽  
Constitutive Parameters

The advent of Powder Bed Fusion (PBF) techniques allows the additive manufacturing of complex structures, as Triply Periodic Minimal Surfaces (TPMS) lattices, which exhibit promising characteristics for impact applications, such as lightweight and high-energy absorption. Thus, this work aims to develop a numerical model of TPMS structures to investigate the mechanical response of such structures when subjected to impact loadings. To fulfill this task, stainless steel samples made by PBF technique were mechanically characterized at different strain rates using a universal testing machine and Split Hopkinson Pressure Bar. The testing campaign also explored the compressive and tensile material response, with the strain field being monitored by Digital Image Correlation technique. It was noted that the material exhibits a similar elasto-plastic response on both tension and compression and an evident strain rate hardening when the material is loaded from static (0.001 s-1) to dynamic strain rates (4000 s-1). Constitutive parameters were then obtained and implemented in an explicit finite element model developed through Abaqus CAE. Samples of TMPS lattices were manufactured and tested at different loading velocities, which showed that the FE model developed can be used to predict the impact response of TMPS lattices.

scholarly journals Investigations on Strain Hardening During Cutting of Heat-Resistant Austenitic Stainless Steel

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Rabiae Arif ◽  
Guillaume Fromentin ◽  
Frédéric Rossi ◽  
Bertrand Marcon
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Plastic Strain ◽  
Strain Hardening ◽  
Subsurface Layer ◽  
Hardened Layer ◽  
Cutting Edge ◽  
Cutting Process ◽  
Image Correlation ◽  
Correlation Technique

Abstract This study presents a novel analysis of the machined subsurface layer formation dealing with strain hardening phenomenon which results from complex mechanisms due to cutting edge multiple passes in drilling. On the one hand, the hardened layer during drilling is characterized in relation with the local cutting geometry and thanks to a quick-stop device (QSD) to suddenly interrupt the operation. Micro hardness is used to determine the hardened thickness of the machined subsurface layers along the local cutting edge geometry. On the other hand, orthogonal cutting performed with a complex self-designed planing experiment is used to investigate in details the hardening accumulation aspects. Then, dedicated methodologies are proposed to quantify the strain hardening as well as the incremental plastic strain generated by consecutive tool passes. In addition to the subsurface hardness evolution, the work material strain is observed during the steady-state cutting process thanks to the high-speed camera. The digital image correlation technique is exploited to analyze not only the plastic strain remaining on the workpiece after the cut but also the effect of the incremental plastic strain generated by the consecutive planing passes as the cutting edges in drilling do. One of the outcomes is that the hardened layer thickness can reach from two to three times the cut thickness in drilling or in planing. As a consequence, this work demonstrates that the cutting process affects itself by hardening. Thus, the studied austenitic stainless steel in such a way that this last is never cut in its initial state.

Large Deformation Strain Measurement Using Digital Image Correlation Technique During Axial Crushing of an Extruded AA-6063 Tube

2016 ◽  
Author(s):  
Arun Kumar Sudalaiyandi ◽  
Ramesh Krishnamurthi ◽  
Raghu V. Prakash
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Tensile Deformation ◽  
Compressive Load ◽  
Image Correlation ◽  
Correlation Technique ◽  
Thin Wall ◽  
Full Field ◽  
Static Test ◽  
Thin Walled

Thin-walled metal tubes are extensively used in aircraft and automobile industries as energy absorbers during collision. When a thin wall tube is subjected to an axial compressive load, lobes are formed sequentially and each lobe undergoes a large plastic deformation without any cracking; this is referred to as progressive buckling. The focus of this paper is to study the displacement and strain fields near the buckled zone of a thin-walled square tube both experimentally and numerically. Quasi-static test was conducted on thin-walled square tubes made of aluminum alloy AA-6063 and the displacement and full-field strain was measured using Digital Image Correlation (DIC) technique. It is noted that while one face of the tube undergoes tensile deformation, the adjacent faces undergo compressive deformation. The strain levels exceed the fracture strain obtained during a tensile test. Strain estimated from DIC was found to be in good agreement with the strain gauge measurements at far field. Further, strain estimations obtained through numerical simulations showed a reasonable agreement with DIC measurements.

Local Plastic Strain Measurement by EBSD

2007 ◽  
Vol 7-8 ◽  
pp. 173-179 ◽  
Author(s):  
Masayuki Kamaya ◽  
Joao Quinta da Fonseca ◽  
L.M. Li ◽  
Michael Preuss
Keyword(s):  
Plastic Strain ◽  
Electron Backscatter Diffraction ◽  
Pure Copper ◽  
Local Strain ◽  
Image Correlation ◽  
Correlation Technique ◽  
Microscopy Imaging ◽  
Local Plastic Strain ◽  
Individual Grains ◽  
Backscatter Diffraction

Work has been carried out recently, which demonstrates misorientation measurements recorded by using electron backscatter diffraction (EBSD) enables one to undertake local post mortem plastic strain quantification once the degree of misorientation is calibrated against plastic strain. The present paper builds on this work and investigates the possibility of determining strain in individual grains. Due to the anisotropy of crystalline grains, polycrystalline material deform inhomogeneously on a microstructural level. In this study, the local strain induced in a pure copper specimen during tensile loading measured using EBSD was compared to in-situ strain measurements using optical microscopy imaging in conjunction with image correlation technique. By applying an averaging procedure for improving the accuracy of the measured EBSD data, the distribution of the misorientation within grains was quantified, and, as one would expect, it tended to be highest near the grain boundaries.

Deformation Behavior and Plastic Strain Localization of Nanostructured Materials Produced by Severe Plastic Deformation

2009 ◽  
Vol 633-634 ◽  
pp. 107-119 ◽  
Author(s):  
Evgeny V. Naydenkin ◽  
Galina P. Grabovetskaya
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Severe Plastic Deformation ◽  
Strain Localization ◽  
Deformation Behavior ◽  
Grain Boundary Sliding ◽  
Deformation Bands ◽  
Localized Deformation ◽  
Plastic Strain Localization ◽  
Structure Heterogeneity

The literature on the deformation behavior and plastic strain localization inherent to nanostructured metallic polycrystals produced by severe plastic deformation techniques is reviewed. The effects of the texture, structure heterogeneity and state of grain boundaries on the special features and evolution of mesoscopic and macroscopic localized deformation bands are investigated. The role of grain-boundary sliding in the development of mesoscopic plastic deformation bands is discussed.

scholarly journals Effect of strain rate on strength and deformation behavior of an Fe-Mn-Al-Ni shape memory alloy

2021 ◽  
Vol 250 ◽  
pp. 05012
Author(s):  
Sebastian Henschel ◽  
Lutz Krüger
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Strain Rate ◽  
Shape Memory ◽  
Deformation Behavior ◽  
Image Correlation ◽  
Coarse Grained ◽  
Strain Rates ◽  
Localized Deformation ◽  
Strength And Deformation

The strength and deformation behavior of an Fe-Mn-Al-Ni shape memory alloy at different strain rates was studied. Furthermore, the effect of grain size was investigated. To this end, a batch with bamboo-like grain arrangement and a batch with smaller, nevertheless coarse, grains were analyzed. Tensile tests at quasi-static, intermediate, and dynamic loading rates were performed. Digital image correlation and microstructural analysis revealed the localized deformation and phase transformation in favorable oriented grains. At higher strain rates, a increased number of orientations was activated for the phase transformation. A higher strain rate resulted in an increased strength for the coarse-grained material while the bamboo-like material did not show this effect. The analysis of fracture surfaces revealed ductile fracture and cleavage fracture for all strain rates.

scholarly journals Autowave Criteria of Fracture and Plastic Strain Localization of Zirconium Alloys

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 95
Author(s):  
Lev B. Zuev ◽  
Svetlana A. Barannikova ◽  
Dina V. Orlova
Keyword(s):  
Plastic Strain ◽  
Cold Rolling ◽  
Strain Distribution ◽  
Ultrasound Velocity ◽  
Zirconium Alloys ◽  
Joint Analysis ◽  
Deformation Bands ◽  
Localized Deformation ◽  
Stress Strain ◽  
Zone Length

Plastic deformation and fracture of Zr–1% Nb alloys exposed to quasi-static tensile testing have been studied via a joint analysis of stress-strain curves, ultrasound velocity and double-exposure speckle photographs. The possibilities of ductility evaluation through the εxx strain distribution in thin-walled parts of zirconium alloys are shown in this paper. The stress-strain state of zirconium alloys in a cold rolling site is investigated considering the development of localized deformation bands and changes in ultrasound velocity. It is established that the transition from the upsetting to the reduction region is accompanied by the significant exhaustion of the plasticity margin of the material; therefore, the latter is more prone to fracture in this zone exactly. It is shown that traditional methods estimating the plasticity margin from the mechanical properties cannot reveal this region, requiring a comprehensive study of macroscopically localized plastic strain in combination with acoustic measurements. In particular, the multi-pass cold rolling of Zr alloys includes various localized deformation processes that can result in the formation of localized plasticity autowaves. Recommendations for strain distribution division over the deformation zone length in the alloy in the pilger roll grooves are provided as well.

Sign in / Sign up

Export Citation Format

Share Document