Thermal Shock Effects on Dynamic Deformation Mechanisms in Ti2AlC

2012 ◽  
Author(s):  
R. Bhattacharya ◽  
N. C. Goulbourne
Keyword(s):  
Thermal Shock ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Deformation ◽  
Compressive Loading ◽  
Image Correlation ◽  
Deformation Mechanisms ◽  
Hopkinson Pressure Bar ◽  
High Speed Imaging ◽  
Full Field

The present study is aimed at understanding the effects of thermal shock and associated microstructural features on the dynamic deformation mechanisms in Ti2AlC, a Mn+1AXn phase ternary ceramic. These materials crystallize in a Hexagonal Close Packed (HCP) structure with a c/a ratio greater than 1.67 which results in kink band formations when subjected to loading. In this work, we report the microstructural changes associated with thermal shocking of Mn+1AXn phases and its effects on deformation mechanisms, under dynamic compressive loading. The specimens are heated to temperatures of 220, 550 and 900°C, held at each temperature for 5–10 minutes, and subsequently quenched in water at 20°C to induce thermal shock. The thermal shock resistance and its effect on mechanical properties is investigated by subjecting heat treated specimens to compressive loading at high strain rates (∼1000–4500 s−1) using a Split Hopkinson Pressure Bar (SHPB). The microstructures of thermally shocked specimens are characterized by Scanning Electron Microscopy (SEM) combined with Energy Dispersive Spectroscopy (EDS) analysis to reveal the surface morphologies and characteristics. The displacements during the deformation events are captured using in situ high speed imaging, with full-field 2D Digital Image Correlation (DIC) technique. The key microscale mechanisms of deformation are studied using SEM analysis of deformed/fractured specimens.

scholarly journals Failure behavior of woven fiberglass composites under combined compressive and environmental loading

2019 ◽  
Vol 54 (4) ◽  
pp. 519-533
Author(s):  
Ariana Paradiso ◽  
Isabella Mendoza ◽  
Amanda Bellafato ◽  
Leslie Lamberson
Keyword(s):  
High Speed ◽  
Shear Failure ◽  
Resin Composite ◽  
Compressive Loading ◽  
Image Correlation ◽  
Failure Behavior ◽  
High Speed Photography ◽  
Environmental Loading ◽  
Full Field ◽  
Environmental Conditioning

The purpose of this study is to quantitatively characterize the compressive and damage behavior of a woven fiberglass composite under combined environmental loading. Cuboidal samples of a commercially available woven fiberglass epoxy resin composite, garolite G10, are examined under uniaxial compressive loading perpendicular to the plies at quasi-static (10−3 s−1) and dynamic (103 s−1) strain rates using a standard load frame and Kolsky (split-Hopkinson) bar. In order to simulate environmental conditions, a subset of samples were soaked in either distilled or ASTM standard seawater prior to loading. Two time periods of environmental conditioning were investigated: short term at two weeks and long term at four months. Results demonstrate that, on average, the dynamic compressive strength of the fiberglass increased 35% from the quasi-static. Moreover, environmentally treated samples generally experienced a decrease strain to failure, and composites exposed to water for only short periods exhibited signs of the absorbed water sustaining additional load under quasi-static rates. Ultra-high-speed photography combined with digital image correlation, a full-field surface kinematic measurement technique, is used to map 2D strains on the sample during loading. In all cases, a clear shear failure mechanism from local instabilities appears, and a Mohr–Coulomb failure criterion is used to extract a mesoscale cohesive shear stress and coefficient of internal friction.

Deformation and Failure of Pre-Notched Thin Metal Plates Subjected to Confined Blast Loading

2015 ◽  
Vol 782 ◽  
pp. 49-58
Author(s):  
Han Liu ◽  
Peng Wan Chen ◽  
Bao Qiao Guo ◽  
Shao Long Zhang ◽  
Hai Bo Liu ◽  
...  
Keyword(s):  
High Speed ◽  
Dynamic Deformation ◽  
Blast Loading ◽  
Thin Metal ◽  
Image Correlation ◽  
Deformation And Failure ◽  
Full Field ◽  
3D Digital Image Correlation ◽  
Metal Plates ◽  
Dic Technique

In this paper, the dynamic deformation and rupture of pre-notched thin metal plates subjected to confined blast loading were investigated. The thin copper plates with cross-shape pre-notch were clamped on the end of a confined cylinder vessel by a cover flange. An explosive charge with a mass of 4g was detonated in the vessel center to generate blast load acting on the metal plates. The images of metal plates were recorded by two high-speed cameras. The displacement and strain fields during the deformation and rupture process were measured by using 3D digital image correlation (3D DIC). The effects of pre-notches on the dynamic deformation and rupture of thin metal plates were analyzed. The microstructure of fracture surface was examined The 3D DIC technique is proven to be an effective method to conduct dynamic full-field deformation measurement.

scholarly journals Simultaneous Full-Field Strain and Temperature Measurements in Tensile Hopkinson Bar Experiments at Extreme Temperatures

2021 ◽  
Vol 250 ◽  
pp. 01015
Author(s):  
Guilherme C. Soares ◽  
Mikko Hokka
Keyword(s):  
Elevated Temperatures ◽  
Split Hopkinson Pressure Bar ◽  
Displacement Vector ◽  
Heating System ◽  
Temperature Measurements ◽  
Image Correlation ◽  
Field Strain ◽  
Hopkinson Pressure Bar ◽  
Function Generator ◽  
Full Field

Simultaneous full-field strain and temperature measurements were used to monitor tension Split Hopkinson Pressure Bar (SHPB) tests at elevated temperatures. A direct heating system was used to increase the specimen temperature up to 1350 °C. Digital Image Correlation (DIC) and Infrared Thermography (IRT) were used was used to simultaneously monitor the evolution of the full-field strain and temperature of the specimen. Data acquisition was synchronized using a function generator, a camera pinhole model was used to represent both strain and temperature on the same coordinate system, and the displacement vector field from DIC was used to represent both datasets on the same reference frame. The use of fullfield techniques was essential at elevated temperatures, as necking occurred soon after yielding and the usability of the data obtained from the SHPB after the onset of necking is debatable. The method was able to follow the full-field strain and the temperature evolution under extreme conditions. Some challenges were found in the development of the method and recommendations as well as future applications are also described in this paper. This experimental approach is versatile and can be applied to different materials at similar testing conditions but also different loading modes and testing setups.

Dynamic Deformation Behavior of Rubber under High Strain Rate Compressive Loading

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1415-1420 ◽  
Author(s):  
Ouk Sub Lee ◽  
Myun Soo Kim ◽  
Kyoung Joon Kim ◽  
Si Won Hwang ◽  
Kyu Sang Cho
Keyword(s):  
Strain Rate ◽  
Deformation Behavior ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Deformation ◽  
Compressive Loading ◽  
Hopkinson Pressure Bar ◽  
Split Hopkinson ◽  
Transition Points ◽  
Dynamic Deformation Behavior ◽  
Pressure Bar

A specific experimental method, the split Hopkinson pressure bar (SHPB) technique is used to determine the dynamic material properties under the impact compressive loading condition with strain-rate of the order of 103/s~104/s. The dynamic deformation behavior of rubber materials widely used for the isolation of vibration from varying structures under dynamic loading is determined by using the Split Hopkinson Pressure Bar technique. The relationships between the stresses at transition points of rubber materials and the strain rate are found to be bilinear. However, an interesting relationship between the strains at transition points of rubber materials and the strain rate, which needs further investigation, is noted.

Performances and Limitations of Three Ultra High-Speed Imaging Cameras for Full-Field Deformation Measurements

2011 ◽  
Vol 70 ◽  
pp. 81-86 ◽  
Author(s):  
Fabrice Pierron ◽  
Rachid Cheriguene ◽  
Pascal Forquin ◽  
Raphael Moulart ◽  
Marco Rossi ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Grid Method ◽  
Image Correlation ◽  
High Speed Imaging ◽  
Full Field ◽  
Ultra High Speed ◽  
Ultra High Speed Imaging ◽  
Deformation Measurements

This paper compares the technology and the performances of three ultra high speed cameras for full-field deformation measurements with Digital image correlation or the grid method. The three cameras are based on multiple CCD sensors (Cordin 550-62, with rotating mirror or DRS IMACON 200 with gated intensified CCDs) or dedicated chip (Shimadzu HPV). The advantages and limitations of these cameras are critically reviewed.

scholarly journals In-Situ Damage Evaluation of Pure Ice under High Rate Compressive Loading

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1236 ◽  
Author(s):  
Isakov ◽  
Lange ◽  
Kilchert ◽  
May
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Compressive Loading ◽  
Compressive Load ◽  
Strain Rate Range ◽  
High Rate ◽  
Hopkinson Pressure Bar ◽  
Order Of Magnitude ◽  
Pressure Bar

The initiation and propagation of damage in pure ice specimens under high rate compressive loading at the strain rate range of 100 s−1 to 600 s−1 was studied by means of Split Hopkinson Pressure Bar measurements with incorporated high-speed videography. The results indicate that local cracks in specimens can form and propagate before the macroscopic stress maximum is reached. The estimated crack velocity was in the range of 500 m/s to 1300 m/s, i.e., lower than, but in similar order of magnitude as the elastic wave speed within ice. This gives reason to suspect that already at this strain rate the specimen is not deforming under perfect force equilibrium when the first cracks initiate and propagate. In addition, in contrast to quasi-static experiments, in the high rate experiments the specimens showed notable residual load carrying capacity after the maximum stress. This was related to dynamic effects in fractured ice particles, which allowed the specimen to carry compressive load even in a highly damaged state.

Static and Dynamic Deformation Measurements of Micro Beams by the Technique of Digital Image Correlation

2006 ◽  
Vol 326-328 ◽  
pp. 211-214 ◽  
Author(s):  
Xiao Yuan He ◽  
Wei Sun ◽  
Xiang Zheng ◽  
Meng Nie
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Dynamic Deformation ◽  
Full Range ◽  
Frame Rate ◽  
Image Correlation ◽  
Static Tests ◽  
Full Field ◽  
Fringe Patterns ◽  
Vibration Parameters

It is critical to measure the static and dynamic deformation of the micro beam over their full range of voltage and frequency inputs, which are key parameters for predicting device behavior. In this study, full-field technique by correlation of projected fringe patterns is selected to determine static deformation, while dynamic parameters can be obtained by DIC with high-speed CMOS camera, whose maximal frame rate is 32k f/s. The static tests of micro beams are carried out by applying electric field forces under different dc voltage, while the dynamic tests are excited by harmonic excitations. Using the DIC method, the whole field in-plane or out-of-plane displacements of the micro beams are obtained, and hence the dynamic characteristics by post-processing of vibration analysis. Experimental results including the bending deformation and vibration parameters are reported and compared with finite element method. This study verifies the feasibility of this technique to measure both static and dynamic characteristics of MEMS components.

scholarly journals Experimental Investigation of the Dynamic Tensile Properties of Naturally Saturated Rocks Using the Coupled Static–Dynamic Flattened Brazilian Disc Method

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4784
Author(s):  
Xinying Liu ◽  
Feng Dai ◽  
Yi Liu ◽  
Pengda Pei ◽  
Zelin Yan
Keyword(s):  
Tensile Properties ◽  
High Speed ◽  
Loading Rate ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Strength ◽  
Image Correlation ◽  
Dynamic Loads ◽  
Hopkinson Pressure Bar ◽  
Dynamic Tensile Strength ◽  
Brazilian Disc

In a naturally saturated state, rocks are likely to be in a stress field simultaneously containing static and dynamic loads. Since rocks are more vulnerable to tensile loads, it is significant to characterize the tensile properties of naturally saturated rocks under coupled static–dynamic loads. In this study, dynamic flattened Brazilian disc (FBD) tensile tests were conducted on naturally saturated sandstone under static pre-tension using a modified split-Hopkinson pressure bar (SHPB) device. Combining high-speed photographs with digital image correlation (DIC) technology, we can observe the variation of strain applied to specimens’ surfaces, including the central crack initiation. The experimental results indicate that the dynamic tensile strength of naturally saturated specimens increases with an increase in loading rate, but with the pre-tension increases, the dynamic strength at a certain loading rate decreases accordingly. Moreover, the dynamic strength of naturally saturated sandstone is found to be lower than that of natural sandstone. The fracture behavior of naturally saturated and natural specimens is similar, and both exhibit obvious tensile cracks. The comprehensive micromechanism of water effects concerning the dynamic tensile behavior of rocks with static preload can be explained by the weakening effects of water on mechanical properties, the water wedging effect, and the Stefan effect.

STUDIES ON THE DYNAMIC FRACTURE PROPERTIES AND FAILURE MODES OF A PBX

2014 ◽  
Vol 06 (04) ◽  
pp. 1450039 ◽  
Author(s):  
R. CHEN ◽  
L. CHENG ◽  
Y. LIN ◽  
F. LU
Keyword(s):  
Dynamic Fracture ◽  
High Speed ◽  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Particulate Composite ◽  
Image Correlation ◽  
Initiation Toughness ◽  
Hopkinson Pressure Bar ◽  
Fracture Properties ◽  
Fracture Velocity

Polymer-bonded explosives (PBXs) are particulate composite materials composed of crystalline explosive grains bound in a relatively soft polymeric binder. It is important to optimize the fracture properties, while still maintaining the low sensitiveness and high explosiveness of PBX. This paper describes a study on the fracture properties and failure modes of a PBX by adopting a newly proposed dynamic fracture experimentation method — notched semi-circular bend (NSCB) specimen loaded with split Hopkinson pressure bar (SHPB) which was used in this study. This method offers the advantage of simultaneously determining the fracture initiation toughness, fracture energy, fracture propagation toughness and fracture velocity. The crack propagation is monitored by using a synchronous high-speed camera, which allows the observation of strain field history via digital image correlation process. The experimental results indicate that both the initiation toughness and the propagation toughness linearly increase with loading rate. The propagation fracture toughness is found to increase with fracture velocity, and a limiting fracture velocity is obtained. The failure modes are interpreted by using various theoretical models. Results suggest that the debonding strength of the binder is much smaller than the crystal fracture strength. The tensile strength is similar to the debonding strength, while the compression strength is somewhere intermediate between them.

scholarly journals ‘Seeing’ Strain in Soft Materials

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 542 ◽  
Author(s):  
Zhiyong Xia ◽  
Vanessa D. Alphonse ◽  
Doug B. Trigg ◽  
Tim P. Harrigan ◽  
Jeff M. Paulson ◽  
...  
Keyword(s):  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Color Change ◽  
Soft Materials ◽  
Image Correlation ◽  
High Rate ◽  
Hopkinson Pressure Bar ◽  
Dimethyl Siloxane ◽  
Split Hopkinson ◽  
Pressure Bar

Several technologies can be used for measuring strains of soft materials under high rate impact conditions. These technologies include high speed tensile test, split Hopkinson pressure bar test, digital image correlation and high speed x-ray imaging. However, none of these existing technologies can produce a continuous 3D spatial strain distribution in the test specimen. Here we report a novel passive strain sensor based on poly(dimethyl siloxane) (PDMS) elastomer with covalently incorporated spiropyran (SP) mechanophore to measure impact induced strains. We have shown that the incorporation of SP into PDMS at 0.25 wt% level can adequately measure impact strains via color change under a high strain rate of 1500 s−1 within a fraction of a millisecond. Further, the color change is fully reversible and thus can be used repeatedly. This technology has a high potential to be used for quantifying brain strain for traumatic brain injury applications.

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