scholarly journals The temperature- and density-dependent acoustic emission response of snow in monoaxial compression tests

2004 ◽  
Vol 38 ◽  
pp. 291-298 ◽  
Author(s):  
Carlo Scapozza ◽  
Felix Bucher ◽  
Peter Amann ◽  
Walter J. Ammann ◽  
Perry Bartelt
Keyword(s):  
Acoustic Emission ◽  
Relaxation Times ◽  
Acoustic Emissions ◽  
Wide Band ◽  
Strain Rates ◽  
Compression Tests ◽  
Load History ◽  
Fine Grained ◽  
Rate Controlled ◽  
The Relationship

AbstractResults of acoustic emission tests on cylindrical specimens under compression are reported. Deformation-rate-controlled tests with strain rates ranging from 1.1 × 10-6 s-1 to 2.6 × 10-3 s-1 at temperatures between T = -11.2°Cand T = -1.7°C were performed. The investigated snow was fine-grained, with a density varying between 220 and 380 kgm-3. The acoustic emission was measured with two distinct piezoelectric sensors: a wide-band sensor (frequency 100–1000 kHz) and a resonant sensor (frequency 35–100 kHz). The relationship between the applied strain rate and the measured maximum acoustic-emission rate as a function of temperature and density was found to obey a power law, which is valid for the ductile behaviour range. The quantitative and qualitative effects produced on the acoustic emissions during the transition from ductile to brittle behaviour, occurring at strain rates of approximately 1 × 10-3 s-1, are reported. Finally, the influence of the load history on the acoustic emissions of snow is discussed on the basis of a cyclic test, including deformation-controlled loading steps and relaxation steps, performed at different strain rates and different relaxation times.

Effect of Silver on Superplastic Deformation in YBa2Cu3O7–x/Ag Composites

2002 ◽  
Vol 17 (5) ◽  
pp. 1172-1177
Author(s):  
Jondo Yun ◽  
Ye T. Chou ◽  
Martin P. Harmer
Keyword(s):  
Activation Energy ◽  
Grain Size ◽  
Superplastic Deformation ◽  
Close Agreement ◽  
Silver Content ◽  
Strain Rates ◽  
Compression Tests ◽  
Fine Grained ◽  
Soft Inclusion ◽  
Activation Energy Of Deformation

Superplastic deformation was studied in fine-grained (0.7–1.1 μm) YBa2Cu3O7–x/Ag composites containing 2.5–25 vol% Ag. The compression tests were conducted in the temperature range of 750–875 °C and at strain rates of 10−5 to 10−3/s. For the YBa2Cu3O7−x/25%Ag composites with grain size of 0.7–1.1 μm, deformed at 800–850 °C and 10−5 to 10−3/s, the stress exponent, grain size exponent, and the activation energy of deformation were 2.0 ± 0.1, 2.5 ± 0.7, and 760 ± 100 kJ/mol, respectively. These values were the same as those of the pure YBa2Cu3O7−x, indicating that the deformation of the composite was controlled by that of the rigid YBa2Cu3O7−x phase. However, the strain rate was increased by the addition of silver as explained by the soft inclusion model of Chen. The dependence of the flow stress on the silver content was in close agreement with the prediction of the model.

Mechanical Properties of Bulk Nanocrystalline Silver-Using Compression Tests

2010 ◽  
Vol 152-153 ◽  
pp. 1313-1316
Author(s):  
Guo Jun Hu ◽  
Zhi Quan Hong
Keyword(s):  
Mechanical Properties ◽  
Coarse Grained ◽  
Strain Rates ◽  
Test Results ◽  
Compression Tests ◽  
Static Test ◽  
Rate Dependent ◽  
Average Grain Size ◽  
Bulk Nanocrystalline ◽  
The Relationship

In this paper, the compression test on the bulk nanocrystalline sliver ( n Ag) with average grain size of 50 nm was made. The stress-strain curves under different strain rates were obtained by test. The test results show that the mechanical behavior of n Ag is rate-dependent, and the dynamic compress yield stress are about 1.5 times of that n Ag in static test condition; The effect of strain harding on n Ag is smaller than that of coarse-grained silver (c Ag) in plastic deformation; The relationship between the yield strength and the logarithm of strain rate is approximately linear.

scholarly journals Study of Acoustic Emission and Mechanical Characteristics of Coal Samples under Different Loading Rates

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Huamin Li ◽  
Huigui Li ◽  
Baobin Gao ◽  
Dongjie Jiang ◽  
Junfa Feng
Keyword(s):  
Acoustic Emission ◽  
Elasticity Modulus ◽  
Loading Rate ◽  
Peak Stress ◽  
Test System ◽  
Strong Impact ◽  
Peak Strain ◽  
Compression Tests ◽  
Loading Rates ◽  
The Relationship

To study the effect of loading rate on mechanical properties and acoustic emission characteristics of coal samples, collected from Sanjiaohe Colliery, the uniaxial compression tests are carried out under various levels of loading rates, including 0.001 mm/s, 0.002 mm/s, and 0.005 mm/s, respectively, using AE-win E1.86 acoustic emission instrument and RMT-150C rock mechanics test system. The results indicate that the loading rate has a strong impact on peak stress and peak strain of coal samples, but the effect of loading rate on elasticity modulus of coal samples is relatively small. When the loading rate increases from 0.001 mm/s to 0.002 mm/s, the peak stress increases from 22.67 MPa to 24.99 MPa, the incremental percentage is 10.23%, and under the same condition the peak strain increases from 0.006191 to 0.007411 and the incremental percentage is 19.71%. Similarly, when the loading rate increases from 0.002 mm/s to 0.005 mm/s, the peak stress increases from 24.99 MPa to 28.01 MPa, the incremental percentage is 12.08%, the peak strain increases from 0.007411 to 0.008203, and the incremental percentage is 10.69%. The relationship between acoustic emission and loading rate presents a positive correlation, and the negative correlation relation has been determined between acoustic emission cumulative counts and loading rate during the rupture process of coal samples.

scholarly journals ACOUSTIC EMISSION AND DAMAGE CHARACTERISTICS OF ANTHRACITE UNDER DIFFERENT CONDITIONS

2021 ◽  
Vol 55 (2) ◽  
pp. 213-218
Author(s):  
Jiyu Zheng ◽  
Xiaohua Jin ◽  
Kunyun Tian ◽  
Yinbo Zhou
Keyword(s):  
Acoustic Emission ◽  
Coal Sample ◽  
Characteristic Curve ◽  
Great Influence ◽  
Acoustic Emissions ◽  
Slow Increase ◽  
Loading Rates ◽  
The Relationship ◽  
Damage Characteristic ◽  
Peak Count

Acoustic emission (AE) can be used to observe the process of coal fracture propagation. Based on a press and acoustic-emission platform, the damage and acoustic-emission characteristics of anthracite with different loading rates, water amounts and sizes were studied. The results show that there is less acoustic emission in the initial compression stage of coal; acoustic emission is more active in the transition from elastic deformation to plastic deformation, which is manifested in the following aspects: the faster the loading rate, the higher is the number of acoustic-emission events; the peak count of acoustic emissions of a saturated-coal sample is significantly lower than that of a natural-coal sample. Coal samples and large coal samples emit even more sounds. Based on the normalization of acoustic-emission counts, the relationship between damage variables and stress-strain is studied, and it is characterized by an initial slow increase, followed by a rapid increase; however, different factors have a great influence on the damage-characteristic curve. The research results have a certain guiding significance for the coal and rock disaster prediction.

Research on the AE Characteristic of the Rock with Rockburst Proneness

2014 ◽  
Vol 608-609 ◽  
pp. 689-692
Author(s):  
Mo Xiao Li ◽  
Guang Zhang ◽  
Jing Xi Chen
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Rock Mechanics ◽  
Compression Tests ◽  
Entire Process ◽  
The Relationship ◽  
Ae Signals

In this paper, in order to strengthen the prediction of rockburst and inquire the relationship between the rockburst proneness of rock and its AE characteristic, each kind of typical rock of volcanic, sedimentary and metamorphic were selected to doing indoor rock mechanics experiments. Calculate the rockburst proneness of these rocks by uniaxial compression tests. In uniaxial compression, we collect the entire process of AE signals by using acoustic emission instrument, then we analysis the AE characteristics of different rocks to inquire the relationship between the AE characteristic and its rockburst proneness.

Acoustic emission distress monitoring in sensitive clay

1984 ◽  
Vol 21 (1) ◽  
pp. 176-180 ◽  
Author(s):  
Robert J. Mitchell ◽  
Philip M. Romeril
Keyword(s):  
Acoustic Emission ◽  
Acoustic Emissions ◽  
Coarse Grained ◽  
Monitor System ◽  
Acoustic Response ◽  
Ottawa Sand ◽  
Fine Grained ◽  
Failure State ◽  
Sensitive Clay ◽  
Failure Conditions

A commercial acoustic emission monitoring system (Model MS-1 Geo-monitor) was used to record acoustic emissions in undisturbed block samples of Champlain Sea clays that were deformed to a passive failure state in the laboratory. Laboratory cast samples of Ottawa sand, washed concrete sand, remoulded kaolin clay, and remoulded Champlain Sea clay were also used in order to correlate the acoustic response of various soils. The Geo-monitor system was capable of detecting and quantifying acoustic emissions in all soils tested. Acoustic emissions associated with failure in the coarse-grained soils ranged from 50 to 200 emissions per minute at an amplification of 1000 times. In the fine-grained soils, an amplification of 105 times was required and acoustic emissions of up to 25 emissions per minute were recorded under passive failure conditions. Keywords: acoustic monitoring, slopes, sensitive clay, laboratory study.

The Formation of Fine-Grained Structure in S304H-Type Austenitic Stainless Steel during Hot-To-Warm Working

2012 ◽  
Vol 715-716 ◽  
pp. 380-385 ◽  
Author(s):  
Marina Tikhonova ◽  
Valeriy Dudko ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Compression Tests ◽  
Scale Level ◽  
Single Pass ◽  
Fine Grained ◽  
Loading Direction ◽  
Fine Grained Structure ◽  
Multiple Compression ◽  
The Relationship

The dynamic process of grain evolution in a Super304H austenitic stainless steel was studied in compression tests. The tests were carried out to a strain of 0.7 at temperatures ranging from 700 to 1000°C and strain rate of 10-3s-1. In addition to single pass compression the multiple compressions with changing the loading direction in 90o and decreasing the temperature with step of 100°C from 1000 to 700°C in each pass were utilized to achieve large cumulative strains. Under multiple compression the values of flow stresses were lower than those at single-pass compressions under the same temperatures. The fraction of dynamically recrystallized grains decreased from 1.0 to almost zero with decreasing temperature in single-pass compressions. On the other hand, almost fully recrystallized structure developed under conditions of multiple compressions. The size of dynamically recrystallized grains decreased with decreasing the deformation temperature, approaching a submicrometer scale level at 700°C. The relationship between the deformation conditions and operating mechanisms of dynamic recrystallization is discussed in some details.

scholarly journals Acoustic Emission Waveform Changes for Varying Seeded Defect Sizes

2006 ◽  
Vol 13-14 ◽  
pp. 427-432 ◽  
Author(s):  
S. Al-Dossary ◽  
R.I. Raja Hamzah ◽  
D. Mba
Keyword(s):  
Acoustic Emission ◽  
Acoustic Emissions ◽  
Defect Size ◽  
Geometric Size ◽  
The Relationship ◽  
Geometric Defect

The investigation reported in this paper was centered on the application of the Acoustic Emissions (AE) technology for characterising the defect sizes on a radially loaded bearing. The aim of this investigation was to ascertain the relationship between the duration of AE transient bursts associated with seeded defects to the actual geometric size of the defect. It is concluded that the geometric defect size can be determined from the AE waveform.

Crushing Behavior of SKYDEX® Material

2013 ◽  
Vol 535-536 ◽  
pp. 121-124
Author(s):  
Feng Zhu ◽  
Bin Hui Jiang ◽  
King H. Yang ◽  
Dong Ruan ◽  
Mike S. Boczek ◽  
...  
Keyword(s):  
Numerical Study ◽  
Thermoplastic Polyurethane ◽  
Deformation Mode ◽  
Element Model ◽  
Fe Model ◽  
Strain Rates ◽  
Cellular Solids ◽  
Compression Tests ◽  
Crushing Behavior ◽  
The Relationship

SKYDEX material is an advanced lightweight porous medium consisting of layers of periodic twin-hemispherical microstructures made of thermoplastic polyurethane. This material is used widely in personnel and structural protection. This paper reports a combined experimental and numerical study on crushing behavior of such material. Compression tests were conducted on the SKYDEX panels at the strain rates of 0.01~10 s-1. A 3D finite element model was developed and validated against experimental data. Based on the FE model, the deformation mode of the microstructures, strength, energy absorption, as well as strain rate effect were predicted and analyzed. Additional simulations were conducted to establish the relationship between the peak strength coefficient and relative density. SKYDEX® material has been found to be a competitive energy absorber among cellular solids.

Evaluation of the acoustic emission caused by the chip segmentation frequency during machining of titanium alloy

2020 ◽  
Vol 87 (11) ◽  
pp. 714-720
Author(s):  
Daniel Schwär ◽  
Germán González ◽  
Eric Segebade ◽  
Frederik Zanger ◽  
Michael Heizmann
Keyword(s):  
Acoustic Emission ◽  
Titanium Alloy ◽  
Spectral Analysis ◽  
Chip Formation ◽  
Acoustic Emissions ◽  
Turning Process ◽  
Longitudinal Turning ◽  
The Relationship ◽  
Chip Analysis

AbstractThis work investigates the relationship between acoustic emission and chip segmentation frequency of Ti-6Al-4V at the external longitudinal turning process. Therefore, several sensors like structure borne sensors, microphones and a force dynamometer have been installed in a vertical turning machine. To induce a change of the segmentation frequency, several experiments with different feed rates have been carried out. From each experiment the acoustic emissions have been recorded and the generated chips have been analyzed. Since the chips get stretched or compressed during the chip formation the change in the length is calculated to get an estimation of the segmentation frequency. The comparison of the spectral analysis of the acoustic emission signals and the chip analysis has shown that both methods show the same tendency. The segmentation frequency decreases with increasing feed.

Sign in / Sign up

Export Citation Format

Share Document