scholarly journals Experimental Study on the Temporal and Morphological Characteristics of Dynamic Tensile Fractures in Igneous Rocks

2021 ◽  
Vol 11 (23) ◽  
pp. 11230
Author(s):  
Xuan Xu ◽  
Li-Yuan Chi ◽  
Jun Yang ◽  
Qi Yu
Keyword(s):  
Dynamic Fracture ◽  
Incubation Time ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Gaussian Function ◽  
Morphological Characteristics ◽  
Igneous Rocks ◽  
Frame Rate ◽  
Image Correlation ◽  
Tensile Fractures

In order to investigate the temporal and morphological characteristics of dynamic tensile fractures, experiments on Brazilian specimens machined from igneous rocks (Breccia and Andesite) are carried out with the split Hopkinson pressure bar (SHPB). Detailed observation of the fracture processes of the Brazilian specimens is captured by high-speed camera at a frame rate of 100,000 frames per second. The rate-dependent effect of the dynamic tensile strength of the two igneous rocks is fitted and predicted by the incubation time criterion. Digital image correlation (DIC) is used to calculate the full-field tensile strain distributions on the specimen surface during the loading stage preceding fracture, and this hysteresis of dynamic fracture relative to stress level is interpreted by introducing the concept of incubation time. After the main crack appears, image processing technology is exploited to extract the pixel information of cracks in the high-speed images. Then, FracPaQ quantifies the morphology of the fragmentized process by filling the binarization of cracks with fracture traces. After coordination of the statistical information from these fracture traces, the rose diagram representing their angles and length weights can visually represent the fragmentized characteristics of the Brazilian specimen. Specifically, length-angle distributions of fracture traces at various moments are consistent with the Gaussian function, and the curve fitting parameters reflect differences in the fracture behaviors between the two igneous rocks. In conclusion, the dynamic fracture characteristics of two igneous rocks in dynamic splitting processes are quantified statistically, which can provide references for relevant research.

scholarly journals Testing of Auxetic Materials Using Hopkinson Bar and Digital Image Correlation

2018 ◽  
Vol 183 ◽  
pp. 02045 ◽  
Author(s):  
Tomáš Fíla ◽  
Petr Zlámal ◽  
Jan Falta ◽  
Tomáš Doktor ◽  
Petr Koudelka ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Poisson’S Ratio ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Lattice Structure ◽  
Frame Rate ◽  
Image Correlation ◽  
Poisson's Ratio ◽  
Strain Gauges

In this paper, a split Hopkinson pressure bar (SHPB) was used for impact loading of an auxetic lattice (structure with negative Poisson’s ratio) at a given strain-rate. High strength aluminum and polymethyl methacrylate bars instrumented with foil strain-gauges were used for compression of an additively manufactured missing-rib auxetic lattice. All experiments were observed using a high-speed camera with frame-rate set to approx. 135.000 fps. High-speed images were synchronized with the strain-gauge records. Dynamic equilibrium in the specimen was analyzed and optimized pulse-shaping was introduced in the selected experiments. Longitudinal and lateral in-plane displacements and strains were evaluated using digital image correlation (DIC) technique. DIC results were compared with results obtained from strain-gauges and were found to be in good agreement. Using DIC, it was possible to analyze in-plane strain distribution in the specimens and to evaluate strain dependent Poisson’s ratio of the auxetic structure.

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 TESTING OF HYBRID NICKEL-POLYURETHANE FOAMS AT HIGH STRAIN-RATES USING HOPKINSON BAR AND DIGITAL IMAGE CORRELATION

2018 ◽  
Vol 18 ◽  
pp. 72 ◽  
Author(s):  
Marcel Adorna ◽  
Petr Zlámal ◽  
Tomáš Fíla ◽  
Jan Falta ◽  
Markus Felten ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Equilibrium ◽  
Polyurethane Foams ◽  
Frame Rate ◽  
Image Correlation ◽  
Correlation Technique ◽  
High Speed Camera

In this paper Split Hopkinson pressure bar (SHPB) was used for dynamic testing of nickel coated polyurethane hybrid foams. The foams were manufactured by electrodeposition of a nickel coating on the standard open-cell polyurethane foam. High strength aluminium alloy bars instrumented with foil strain-gauges were used for dynamic loading of the specimens. Experiments were observed using a high-speed camera with frame-rate set to approx. 100-150 kfps. Precise synchronisation of the high-speed camera and the strain-gauge record was achieved using a through-beam photoelectric sensor. Dynamic equilibrium in the specimen was achieved in all measurements. Digital image correlation technique (DIC) was used to evaluate in-plane displacements and deformations of the samples. Specimens of two different dimensions were tested to investigate the collapse of the foam structure under high-speed loading at the specific strain-rate and strain.

STRAIN RATE-DEPENDENT CHARACTERIZATION OF THE IN-PLANE SHEAR RESPONSE OF A UNIDIRECTIONAL NON-CRIMP FABRIC CARBON FIBER/SNAP-CURE EPOXY COMPOSITE

2021 ◽  
Author(s):  
KHIZAR ROUF ◽  
MICHAEL J. WORSWICK ◽  
JOHN MONTESANO
Keyword(s):  
Carbon Fiber ◽  
Strain Rate ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Equilibrium ◽  
Epoxy Composite ◽  
Axial Strain ◽  
Image Correlation ◽  
High Rate ◽  
Plane Shear

The dynamic in-plane shear stress-strain response of a unidirectional non- crimp fabric carbon fiber/snap-cure epoxy composite was studied by subjecting 30° and 45° off-axis specimens to compression loading at high strain rates. Tests were performed using a compression split-Hopkinson pressure bar apparatus where an approximate axial strain rate of 305 s-1 was achieved. Images of the deformed specimen surfaces were captured with high-speed cameras and digital image correlation used to obtain a strain map. Pulse shaping was performed using a copper pulse shaper to achieve dynamic equilibrium during the high-rate tests. The results demonstrated that the in-plane shear yield stress and strength increased by 53% and 68%, respectively, when the strain rate increased from quasi-static to 305 s-1.

Mechanical Behavior of Sn1Ag0.5Cu and Sn3Ag0.5Cu Alloys at High Strain Rates

2012 ◽  
Author(s):  
Pradeep Lall ◽  
Sandeep Shantaram ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Prolonged Exposure ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Image Correlation ◽  
Constitutive Behavior ◽  
Strain Rates ◽  
High Strain Rates ◽  
Test Technique

Electronics may experience high strain rates when subjected to high g-loads of shock and vibration. Material and damage behavior of electronic materials at high strain rates typical of shock and vibration is scarce. Previously studies have shown that second-level interconnects have a high propensity for failure under shock and vibration loads in fine pitch electronics. Exposure to shock and vibration is common in a variety of consumer environments such as automotive and portable electronics. The low strain-rate properties of commonly used SnAgCu solders, including Sn1Ag0.5Cu and Sn3Ag0.5Cu, have been found to evolve with time after prolonged exposure to high temperatures. High strain rate properties of leadfree solder alloys in the strain-rate range of 1–100 sec−1 are scarce. Previous attempts at characterizing the high strain rates properties have focused on the use of the Split Hopkinson Pressure Bar (SHPB), which enables measurements of strain rates in the neighborhood of 1000 per sec. In this paper, a new test-technique developed by the authors has been presented for measurement of material constitutive behavior. The instrument enables attaining strain rates in the neighborhood of 1 to 100 per sec. Tests are conducted at strain rates 10, 35 and 50 per sec. High speed cameras operating at 75,000 fps have been used in conjunction with digital image correlation for the measurement of full-field strain during the test. Constancy of cross-head velocity has been demonstrated during the test from the unloaded state to the specimen failure. Solder alloy constitutive behavior has been measured for SAC105, SAC305 solders. Non-linear Ramberg-Osgood model has been used to fit the material data. The Ramberg-Osgood model available in Abaqus has been used for tensile test simulation and to correlate with DIC based experimental strain data.

scholarly journals The use of charge-coupled device cameras for characterizing the mean deflected shape of an aerospace panel during broadband excitation

2018 ◽  
Vol 54 (1) ◽  
pp. 13-23 ◽  
Author(s):  
Elias Lopez-Alba ◽  
Christopher M Sebastian ◽  
William JR Christian ◽  
Eann A Patterson
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
High Volume ◽  
Random Excitation ◽  
Frame Rate ◽  
Image Correlation ◽  
Charge Coupled Device ◽  
The Mean ◽  
Standard Frame

In vibration experiments demanding long-duration measurements, traditional point-wise techniques are often employed, despite the availability of high-speed digital image correlation. This is due to the high volume of images generated by the latter technique, which limit acquisition times and lengthen post-processing times. In this experimental investigation, it is demonstrated that standard frame rate charge-coupled device cameras yield results for the mean deflected shape of a reinforced aerospace panel subject to a random broadband excitation between 0 and 800 Hz that are not statistically different to those from high-speed cameras. The images from both types of camera were processed using digital image correlation to generate out-of-plane displacement maps, which were then decomposed using Chebyshev descriptors for ease of comparison and to determine the mean deflected shape. The results indicate that, with appropriate sampling rates and durations, standard frame rate charge-coupled device cameras can be used to study broadband random excitation behavior of structures when mean behavior needs to be characterized over long time scales compared to the excitation wavelengths. This is contrary to accepted procedures, but offers comparable accuracy with substantially reduced computational resources compared to using high-speed cameras, as well as effectively unlimited data acquisition periods, which is useful in condition monitoring, for example.

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 Rock Dynamic Fracture Characteristics Based on NSCB Impact Method

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Yanbing Wang
Keyword(s):  
Fracture Toughness ◽  
Dynamic Fracture ◽  
High Speed ◽  
Loading Rate ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Fracture Toughness ◽  
High Speed Photography ◽  
Rate Dependency ◽  
Hopkinson Pressure Bar ◽  
Rock Materials

In 2012, the International Society for Rock Mechanics (ISRM) recommended a new Notched Semicircular Bend (NSCB) method for the determination of dynamic fracture toughness of rock materials, but it did not consider the effect of some uncontrollable factors in the course of the experiment on the test result. This thesis firstly carried out dynamic fracture toughness experiments on several typical rock materials such as sandstone using the modified Split-Hopkinson Pressure Bar (SHPB) experimental system with high-speed photography, directly compared the dynamic fracture failure characteristics of several rock materials, and examined the loading rate dependency of the dynamic fracture toughness of rock materials. Based on the numerical analysis method of Discrete Lattice Spring Model (DLSM), it focused on the effect of bullet impact loading rate, loading area of incident bar, support restraints of clamping specimen, and other uncontrollable factors in the course of SHPB experiment on test results. The findings can be referenced for the improvement of NSCB method.

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.

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