scholarly journals Study on Impact Damage and Energy Dissipation of Coal Rock Exposed to High Temperatures

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Tu-bing Yin ◽  
Kang Peng ◽  
Liang Wang ◽  
Pin Wang ◽  
Xu-yan Yin ◽  
...  
Keyword(s):  
High Temperatures ◽  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Impact Damage ◽  
Time History ◽  
Hopkinson Pressure Bar ◽  
Absorbed Energy ◽  
Failure Patterns ◽  
Temperature Conditions ◽  
Coal Rock

The dynamic failure characteristics of coal rock exposed to high temperatures were studied by using a split Hopkinson pressure bar (SHPB) system. The relationship between energy and time history under different temperature conditions was obtained. The energy evolution and the failure modes of specimens were analyzed. Results are as follows: during the test, more than 60% of the incident energy was not involved in the breaking of the sample, while it was reflected back. With the increase of temperature, the reflected energy increased continuously; transmitted and absorbed energy showed an opposite variation. At the temperature of 25 to 100°C, the absorbed energy was less than that transmitted, while this phenomenon was opposite after 100°C. The values of specific energy absorption (SEA) were distributed at 0.04 to 0.1 J·cm−3, and its evolution with temperature could be divided into four different stages. Under different temperature conditions, the failure modes and the broken blocks of the samples were obviously different, combining with the variation of microstructure characteristics of coal at high temperatures; the physical mechanism of damage and failure patterns of coal rock are explained from the viewpoint of energy.

scholarly journals Experimental and Numerical Studies on the Dynamic Behaviors of Concrete Material Based on the Waveform Features in SHPB Test

2018 ◽  
Vol 183 ◽  
pp. 01001
Author(s):  
Xiao Weintu Chen ◽  
Taihong Lv ◽  
Gang Chen
Keyword(s):  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Failure Process ◽  
Scale Model ◽  
Hopkinson Pressure Bar ◽  
Damage Development ◽  
Concrete Material ◽  
Deformation And Failure ◽  
Failure Patterns ◽  
Shpb Test

The tendency of the waveform curve can directly reflect the deformation and failure process of specimen in the SHPB (Split Hopkinson Pressure Bar) test of concrete. Different loading rates will result in the different ultimate failure modes, waveform curves. Furthermore, these differences are obviously characterized by some feature points of waveform or stress-strain curves. It is to say for concrete-like damage softening materials, the waveform features contains lots of information of material response. In this study, large dimension (Ф120mm) SHPB tests of concrete specimens have been conducted. Four typical failure patterns of concrete specimens are classified, as well as some typical waveform features, e.g. the “double-peak” and“compression wave” phenomena of reflection wave, etc. On the other hand, the numerical simulations corresponding to the experimental tests are performed by means of the 3D meso-scale model of concrete material. In the numerical results, waveform features observed in experiment are reliably reproduced and predicted. Associating with waveform features, the violation indicator of the specimen stress equilibrium in the SHPB test is first identified for concrete-like damage softening materials. The concrete material behaviors forstress non-equilibrium are further analyzed, e.g. DIF and damage development, etc.

High Strain Rate Response of PVC Foams

2001 ◽  
Author(s):  
Tonnia Thomas ◽  
Hassan Mahfuz ◽  
Leif A. Carlsson ◽  
Krishnan Kanny ◽  
Shaik Jeelani
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Failure Modes ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Time History ◽  
Stress And Strain ◽  
Hopkinson Pressure Bar ◽  
Major Mode

Abstract In this study, cross-linked poly-vinylchloride (PVC) closed-cell foams were examined under high strain rate compression loading using a servohydraulic testing machine and a modified Split Hopkinson Pressure Bar (SHPB) apparatus with a steel incident bar and a polycarbonate transmitter bar for strain rates up to 2000 s−1. Three foam densities were examined, viz. 75, 130, and 260 kg/m3. The stress and strain-time history and stress-strain behavior were evaluated. An increase of stress and strain was observed for all categories of foam as strain rate increased. A post impact study was also performed to evaluate the failure modes of the foam cores. A densification band of collapsed cells was the major mode of failure.

scholarly journals Assimilation of Dynamic Combined Finite Discrete Element Methods Using the Ensemble Kalman Filter

2021 ◽  
Vol 11 (7) ◽  
pp. 2898
Author(s):  
Humberto C. Godinez ◽  
Esteban Rougier
Keyword(s):  
Kalman Filter ◽  
Ensemble Kalman Filter ◽  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Peak Stress ◽  
Discrete Element ◽  
Material Behavior ◽  
Model Parameters ◽  
Hopkinson Pressure Bar ◽  
Parameter Values

Simulation of fracture initiation, propagation, and arrest is a problem of interest for many applications in the scientific community. There are a number of numerical methods used for this purpose, and among the most widely accepted is the combined finite-discrete element method (FDEM). To model fracture with FDEM, material behavior is described by specifying a combination of elastic properties, strengths (in the normal and tangential directions), and energy dissipated in failure modes I and II, which are modeled by incorporating a parameterized softening curve defining a post-peak stress-displacement relationship unique to each material. In this work, we implement a data assimilation method to estimate key model parameter values with the objective of improving the calibration processes for FDEM fracture simulations. Specifically, we implement the ensemble Kalman filter assimilation method to the Hybrid Optimization Software Suite (HOSS), a FDEM-based code which was developed for the simulation of fracture and fragmentation behavior. We present a set of assimilation experiments to match the numerical results obtained for a Split Hopkinson Pressure Bar (SHPB) model with experimental observations for granite. We achieved this by calibrating a subset of model parameters. The results show a steady convergence of the assimilated parameter values towards observed time/stress curves from the SHPB observations. In particular, both tensile and shear strengths seem to be converging faster than the other parameters considered.

scholarly journals Effects of Temperature and Water on Mechanical Properties, Energy Dissipation, and Microstructure of Argillaceous Sandstone under Static and Dynamic Loads

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Rongrong Zhang ◽  
Dongdong Ma ◽  
Qingqing Su ◽  
Kun Huang
Keyword(s):  
Mechanical Properties ◽  
Energy Dissipation ◽  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Physical And Mechanical Properties ◽  
P Wave ◽  
Peak Strain ◽  
Hopkinson Pressure Bar ◽  
Stress Strain ◽  
Sandstone Specimen

RMT-150B rock mechanics and split Hopkinson pressure bar (SHPB) devices were adopted to investigate the physical and mechanical properties, energy dissipation, and failure modes of argillaceous sandstone after different high temperatures under air-dried and saturation states. In addition, SEM and EDS tests were conducted to investigate its microstructure characteristics. Results showed that both the P-wave velocity and density of argillaceous sandstone specimen decreased with the increase of high temperature, while its porosity increased. Compared with static stress-strain curves, there was no obvious compaction stage for dynamic stress-strain curves, and the decrease rate of dynamic curves after peak strain was obviously slow compared with static curves. Both the static and dynamic strengths of argillaceous sandstone specimens decreased with increasing temperature, and the critical temperature point for the strength of argillaceous sandstone was 400°C. At the same temperature, the specific energy absorption under air-dried state was generally smaller compared with that under saturated state. Both the strain rate and temperature showed significant effect on the failure mode. After 100∼1000°C heat treatment, the granular crystals of the clastic structure gradually became larger, and both the number and average size of the original pores decreased, resulting in the deterioration of mechanical properties of argillaceous sandstone specimen.

Experimental and Numerical Researches of Dynamic Failure of a High Strength Alumina/Boride Ceramic Composite

2008 ◽  
Vol 368-372 ◽  
pp. 713-716 ◽  
Author(s):  
Jiang Tao Zhang ◽  
Li Sheng Liu ◽  
Peng Cheng Zhai ◽  
Qing Jie Zhang
Keyword(s):  
Ceramic Composite ◽  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Numerical Models ◽  
High Strength ◽  
Tensile Failure ◽  
Hopkinson Pressure Bar ◽  
Loading Direction ◽  
Split Hopkinson ◽  
Pressure Bar

The dynamic compressive behavior of Al2O3 (10% vol.) / TiB2 ceramic composite had been tested by using a split Hopkinson pressure bar in this paper. The results show that the main failure modes of the ceramic composite include crushed failure and split fracture along the loading direction. The former is the typical compressive failure of brittle materials. The later is tensile failure along the flaws produced during the composite manufacturing. The numerical simulation was also used to study the effect of the diameter/length ratio of the samples on the experimental results. The effect of the deformation in the bars’ ends, which contacted with the samples, was also studied in the numerical models.

scholarly journals Analysis of Fractal and Energy Consumption Characteristics of Concrete under Impact Loading

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Yutao Li ◽  
Faning Dang ◽  
Mei Zhou ◽  
Jie Ren
Keyword(s):  
Fractal Dimension ◽  
Surface Energy ◽  
Failure Modes ◽  
Crack Surface ◽  
Split Hopkinson Pressure Bar ◽  
Utilization Rate ◽  
Compression Tests ◽  
Hopkinson Pressure Bar ◽  
Impact Compression ◽  
Aggregate Rate

In order to study the compressive deformation and energy evolution characteristics of concrete under dynamic loading, impact compression tests with impact velocities of 5, 6, and 7 m/s were carried out on concrete samples with aggregate volume ratios of 0, 32%, 37%, and 42%, respectively, using a split Hopkinson pressure bar test apparatus. The broken concrete pieces after destruction were collected and arranged. The fractal characteristics of fragmentation distribution of concrete specimens with different aggregate rates under impact were discussed, and the roughness of the fragment surface was characterized by the fractal dimension of the broken fragment and the crack surface energy was calculated. In addition, the analytical equation of the fractal dimension of the broken fragment and the crack surface energy was established. The relationship between the specimen energy absorption and the crack surface energy was compared and analyzed. The results show that the concrete specimens are mainly tensile split failure modes under different impact speeds. The fractal dimension, absorption energy, and crack surface energy all increase with the increase in impact speed and decrease with the increase in the aggregate rate. When the aggregate rate is different, the effective utilization rate of the absorbed energy is the largest when the aggregate content is 37%. The surface energy of the crack can be used to estimate the concrete dynamic intensity.

scholarly journals Mechanical Characterization of Different Aluminium Foams at High Strain Rates

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1428 ◽  
Author(s):  
Ana M. Amaro ◽  
Maria A. Neto ◽  
José S. Cirne ◽  
Paulo N.B. Reis
Keyword(s):  
Split Hopkinson Pressure Bar ◽  
Cell Structure ◽  
Casting Process ◽  
Nominal Composition ◽  
Hopkinson Pressure Bar ◽  
Absorbed Energy ◽  
The Us ◽  
Split Hopkinson ◽  
Pressure Bar

Samples having nominal compositions of AlSi12 and Al6082-T4 were prepared using a lost wax casting process, with nominal relative densities of 20%, 40%, and 60%, as well as arrangements of a uniform cell structure (US) or a dual-size cell (DS). For comparison, samples of aluminium foam-filled tubes having the same nominal composition were also prepared with the same technique, with nominal relative densities of 20% and similar arrangements (US and DS). Impact tests at different velocities were performed using a split Hopkinson pressure bar (SHPB). It is possible to conclude that Al6082-T4 foams have better performance, in both configurations, than the AlSi12 ones. Considering a uniform cell structure and a density of 20%, the absorbed energy by the Al6082-T4 foams was around 25% higher than the value observed for the AlSi12 ones. In terms of arrangement, the US structure presents absorbed energy around 57% lower than the DS ones, while the AlSi12 foams with a relative density of 20% were compared. Finally, the absorbed energy growths from 2.8 × 105 to 5.2 × 105 J/m3, when the density increased from 20% to 60%. However, when these foams were involved with a tube, the performances increased substantially.

Analysis of Failure Patterns and Damage Mechanisms under Impact Compression of Hybrid Fiber Reinforced Concrete

2012 ◽  
Vol 193-194 ◽  
pp. 609-613
Author(s):  
Meng Chen ◽  
Zhi Li ◽  
Zhe An Lu
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Compression ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced ◽  
Hybrid Fiber ◽  
Impact Compression ◽  
Failure Patterns ◽  
Compression Properties

In order to studying the failure patterns under impact compression of Hybrid Fiber Reinforced Concrete(HFRC), tests focused on static and dynamic compression properties according to steel fiber reinforced concrete(SFRC) and HFRC are adopted. The equipment of dynamic compression properties test is Ф74mm split Hopkinson pressure bar (SHPB). The static and dynamic compressive strength at four different strain rates of the two materials are obtained, while failure mechanism has been analyzed from specimens’ failure modes in static and dynamic compressive tests, which in turn provides theory basis for the application of HFRC.

Numerical Simulation of Polyurethane Strengthened Perforated Masonry Walls under Blast Loading

2013 ◽  
Vol 639-640 ◽  
pp. 727-731
Author(s):  
Yu Rong Guo ◽  
Hong Zheng
Keyword(s):  
Numerical Simulation ◽  
Failure Modes ◽  
Numerical Models ◽  
Time History ◽  
Local Failure ◽  
Masonry Walls ◽  
Layer Number ◽  
Failure Patterns ◽  
Resistance Performance ◽  
Strengthening Method

In order to investigate the explosion resistance performance of perforated masonry walls strengthened with polyurethane, nine numerical models with different layer number and different strip width of polyurethane are established in this paper. Deformation drawings and time history curves of displacement of the numerical models are comparatively analyzed. It is found that there are two failure modes, global failure and local failure, of strengthened masonry walls and the differences of failure patterns are significant between various types of strengthening method.

THE FAILURE BEHAVIOR OF EXTRUDED Mg-12Gd-3Y-0.4Zr ALLOY SUBJECTED TO IMPACT LOADING

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2267-2272
Author(s):  
WEI JI ◽  
YAFU FAN
Keyword(s):  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Shear Bands ◽  
Optical Microscope ◽  
Failure Behavior ◽  
Strain Rates ◽  
Shear Cracks ◽  
Hopkinson Pressure Bar ◽  
Average Width ◽  
Steel Balls

Dynamic failure behaviors of the extruded Mg -12 Gd -3 Y -0.4 Zr alloy were investigated by means of optical microscope and scanning electron microscope (SEM). The dynamic tensile and compressive tests were carried out at 423K~798K and strain rates of 102~103s-1 using a split Hopkinson pressure bar. Additionally, in order to study the failure characteristic of this alloy at higher strain rates, such as 107s-1, a series of ballistic tests were carried out. The results indicate that the failure mechanisms of both tensile and compressive specimens exhibit an obvious dependence on the temperature. As the testing temperatures increased from 423K to 798K, the fractographs of the tensile specimens varied from quasi-cleavage fracture to intergranular rupture, and the failure modes of the compressive specimens changed from shear cracks to dynamic recrystallization zone. Adiabatic shear bands with an average width 10µm were observed in the post-test magnesium targets penetrated by steel balls.

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