scholarly journals The influence of microstructure geometry on the scale effect in mechanical behaviour of heterogeneous materials

2017 ◽  
Vol 24 (4) ◽  
pp. 557-571 ◽  
Author(s):  
Adrian Różański ◽  
Magdalena Rajczakowska ◽  
Andrzej Serwicki
Keyword(s):  
Uniaxial Compression ◽  
Scale Effect ◽  
Mechanical Behaviour ◽  
Young Modulus ◽  
Uniaxial Compression Test ◽  
Compression Tests ◽  
Number Of Factors ◽  
Pore Size Distributions ◽  
Attenuation Profiles ◽  
The Relationship

AbstractThere are a significant number of factors which have impact on the scale effect in the mechanical behaviour of composite materials. In this paper, the influence of the microstructure on this phenomenon is examined. In particular, how the results of the uniaxial compression test are affected by the microstructure geometry is verified. For the purposes of this study, two different materials are chosen, i.e. pure gypsum and mortar. Firstly, the microstructures of the two considered materials are compared with the use of different microstructure measures, i.e. attenuation profiles, porosity and pore size distributions, calculated based on the images obtained from the X-ray microCT. Then, a series of uniaxial compression tests is performed for a large number of cylindrical specimens made of the two materials under study. Four different sample diameters are assumed in order to investigate the size effect in the considered composites. For both materials, the results of uniaxial compressive strength and the Young modulus are presented. The relationship between the microstructure of the material and the scale effect in mechanical properties is proved. The scale effect is more demonstrable in the case of the material which exhibits a more heterogeneous microstructure.

Texture Changes during Uniaxial Compression of Mg-3Al-1Zn

2004 ◽  
Vol 467-470 ◽  
pp. 429-434 ◽  
Author(s):  
Petra Backx ◽  
Matthew R. Barnett ◽  
Leo Kestens
Keyword(s):  
Uniaxial Compression ◽  
Annealing Treatment ◽  
Processing Parameters ◽  
Mechanical Anisotropy ◽  
Uniaxial Compression Test ◽  
Compression Tests ◽  
Texture Change ◽  
Different Temperatures ◽  
Axis Compression ◽  
Different Strains

The mechanical anisotropy of wrought Mg alloys is very high. For example the yield stress of extruded Mg-3Al-1Zn tested in tension can be as high as twice that obtained in compression [1]. To solve the problems this creates for product design it is necessary to understand the sensitivity of texture to processing parameters. Uniaxial compression tests at different temperatures were performed on cylindrical samples of an extruded Mg-3Al-1Zn bar. The texture during this deformation changes from a situation where all crystal c-axes are nearly perpendicular to the sample axis to one where the c-axes are all nearly parallel to this axis. Compression was stopped at different strains to examine the rate of this texture change. Textures were examined using EBSD measurements. It was found that different mechanisms operate depending on the temperature of deformation and that a variety of textures can be created. Also it was seen that an annealing treatment performed after compression has an influence on the texture. Afterwards the samples were subjected to another uniaxial compression test to examine the influence of texture on room temperature properties.

scholarly journals Application of supervised machine learning as a method for identifying DEM contact law parameters

2021 ◽  
Vol 18 (6) ◽  
pp. 7490-7505
Author(s):  
Piotr Klejment ◽  
Keyword(s):  
Machine Learning ◽  
Uniaxial Compression ◽  
Calibration Procedure ◽  
Supervised Machine Learning ◽  
Critical Threshold ◽  
Uniaxial Compression Test ◽  
Universal Relation ◽  
Compression Tests ◽  
Input Parameters ◽  
Pertinent Question

<abstract> <p>Calibration of Discrete Element Method (DEM) models is an iterative process of adjusting input parameters such that the macroscopic results of simulations and experiments are similar. Therefore, selecting appropriate input parameters of a model effectively is crucial for the efficient use of the method. Despite the growing popularity of DEM, there is still an ongoing need for an efficient method for identifying contact law parameters. Commonly used trial and error procedures are very time-consuming and unpractical, especially in the case of models with many parameters to calibrate. It seems that machine learning may offer a new approach to that problem. This research aims to apply supervised machine learning to figure out the dependencies between specific microscopic and macroscopic parameters. More than 6000 DEM simulations of uniaxial compression tests gathered the data for two algorithms - Multiple Linear Regression and Random Forest. Promising results with an accuracy of over 99% give good hope for finding a universal relation between input and output parameters (for a specific DEM implementation) and reducing the number of simulations required for the calibration procedure. Another pertinent question concerns the size of the DEM models used during calibration based on the uniaxial compression test. It has been proven that calibration of certain parameters can be done on smaller samples, where the critical threshold is around 30% of the radius of the original model.</p> </abstract>

scholarly journals Research on the Surface Fractal Characteristic of the Rock with Rockburst Proneness

2016 ◽  
Vol 12 (12) ◽  
pp. 71
Author(s):  
Moxiao Li ◽  
Ying-hua Song ◽  
Guang Zhang ◽  
Jing-xi Chen
Keyword(s):  
Fractal Dimension ◽  
Uniaxial Compression ◽  
Compression Test ◽  
Uniaxial Compression Test ◽  
Fractal Method ◽  
Fractal Characteristic ◽  
Surface Fractal ◽  
Crack Morphology ◽  
Different Types ◽  
The Relationship

In order to strengthen the prediction of rockburst and inquire the relationship between the rockburst proneness of rock and its surface fractal characteristic, the surface fractal of the rock was studied by fractal method and uniaxial compression test. The change rules of surface fractal of different types of rock were compared by calculating its fractal dimension of rock before experiment and after experiment. Based on the prediction results, we found that the dimension after test is bigger than before test for four kinds of rocks. The rock with stronger rockburst proneness has more intense failure in the loading process and its crack morphology is more complex.

scholarly journals The Determination of a Damage Model for Mudstone under Uniaxial Loading in Acidic Conditions

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
K. Cao ◽  
L. Ma ◽  
Y. Wu ◽  
A. J. S. (Sam) Spearing ◽  
Naseer Muhammad Khan ◽  
...  
Keyword(s):  
Uniaxial Compression ◽  
Mechanical Test ◽  
Damage Parameter ◽  
Coal Bed ◽  
Relative Mass ◽  
Uniaxial Compression Test ◽  
Peak Strain ◽  
Compression Tests ◽  
Analysis And Design ◽  
Chemical Damage

The influence of acid solutions was investigated on the mechanical properties of mudstone. Uniaxial compression tests on mudstone samples were conducted to determine the variations of relative mass, porosity, deformation, and strength characteristics of mudstone subjected to acidic solutions with different pH values. The change of pH, relative mass, and porosity of mudstone in the process of acid solution immersion was monitored during soaking. The mechanism of hydrochemical corrosion of mudstone samples was preliminarily discussed. The damage parameter was introduced based on the porosity rate. The results show that with increased solution acidity, the peak stress and elastic modulus decreased to different levels, while the peak strain increases in the rock samples. The increased chemical damage parameters reduce the mechanical parameters and increased the deformation parameters. On the basis of the mechanical test, considering the stress-strain relationship of rock in the compaction stage, a segmented damage constitutive model of rock based on chemical damage parameters is established, and the test results are verified. The results show that the correlation coefficient between the theoretical curve and the experimental data is as high as 0.98, and the model is suitable for the analysis of chemically corroded rock under the uniaxial compression test. The results provide a reference for the analysis and design of coal-bed methane wells where the rocks frequently become acidic during the production of methane.

Research on the Surface Fractal Characteristic of the Rock with Rockburst Proneness

2016 ◽  
Vol 1 (2) ◽  
pp. 349
Author(s):  
Li Mo-xiao ◽  
Zhang Guang ◽  
Chen Jing-xi
Keyword(s):  
Fractal Dimension ◽  
Uniaxial Compression ◽  
Compression Test ◽  
Uniaxial Compression Test ◽  
Fractal Method ◽  
Fractal Characteristic ◽  
Surface Fractal ◽  
Crack Morphology ◽  
Different Types ◽  
The Relationship

<p>In order to strengthen the prediction of rockburst and inquire the relationship between the rockburst proneness of rock and its surface fractal characteristic, the surface fractal of the rock was studied by fractal method and uniaxial compression test. The change rules of surface fractal of different types of rock were compared by calculating its fractal dimension of rock before experiment and after experiment. Based on this, we found that the dimension after test is bigger than before test for four kinds of rocks. The rock with stronger rockburst proneness has more intense failure in the loading process and its crack morphology is more complex.</p>

Plastic Behaviour of Green Powder Metallurgical Compacts

2007 ◽  
Vol 534-536 ◽  
pp. 305-308
Author(s):  
Jose Manuel Prado
Keyword(s):  
Plastic Deformation ◽  
Internal Friction ◽  
Uniaxial Compression ◽  
Mechanical Behaviour ◽  
Experimental Results ◽  
Compression Tests ◽  
Contact Areas ◽  
Plastic Behaviour ◽  
Different Levels ◽  
Cam Clay

The results of monotonic and cyclic uniaxial compression tests, in which the deviatoric component of the stress is predominant, carried out on green and recrystallized iron compacts with different levels of density are presented and discussed in order to analyse the macro and micromechanisms governing the mechanical behaviour of non-sintered PM materials. The plastic deformation of the particles, especially at the contact areas between neighbouring particles, produces an internal friction responsible for the main features observed in the behaviour of green metallic compacts. These experimental results show important discrepancies with the plasticity models, Cam-Clay and Drucker-Prager Cap, used to simulate the powder compaction stage. Possible causes for these discrepancies are pointed out.

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.

scholarly journals Application of single-board computers in experimental research on unsaturated soils

2020 ◽  
Vol 195 ◽  
pp. 02022
Author(s):  
Marius Milatz
Keyword(s):  
Uniaxial Compression ◽  
Mechanical Behaviour ◽  
Unsaturated Soils ◽  
Water Retention ◽  
University Teaching ◽  
Water Retention Curve ◽  
Raspberry Pi ◽  
Granular Soils ◽  
Compression Tests ◽  
Unsaturated Granular Soils

In this contribution, the application of single-board computers for the investigation of the hydro-mechanical behaviour of unsaturated granular soils is presented. Single-board computers, such as the Raspberry Pi or Arduino, have recently experienced a hype of applications in school and university teaching, in the maker scene, amongst hobbyists, but also in research. In combination with easy to learn and open programming languages, such as Python, individual experimental set-ups for research in unsaturated soil mechanics, using actuators and sensors can be easily developed with the help of different programmable hardware, such as stepper motors, analog-to-digital converters and other controller boards. For the experimental application in imaging of unsaturated granular soils by computed tomography (CT), we present a miniaturized uniaxial compression device for the measurement of unsaturated shear strength and capillary cohesion in CT-experiments. The device has already been applied for CT-imaging of the development of water distribution and capillary bridges in between different shear steps. Furthermore, a new fully programmable hydraulic experimental set-up for the automated investigation of transient hydraulic paths of the water retention curve of granular media is presented. Both devices have been developed in the framework of the Raspberry Pi single-board computer and Python programming language with simple and relatively inexpensive hardware components. In addition to the technical development of the testing devices, experimental results of the hydro-mechanical behaviour of unsaturated sand and glass beads, derived from uniaxial compression tests and water retention tests, will be presented.

scholarly journals Energy Analysis Method for Uniaxial Compression Test of Sandstone under Static and Quasi-Dynamic Loading Rates

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Zhixi Liu ◽  
Guangming Zhao ◽  
Xiangrui Meng ◽  
Ruofei Zhang ◽  
Dong Chunliang ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Uniaxial Compression ◽  
Compression Test ◽  
Elastic Energy ◽  
Loading Rate ◽  
Uniaxial Compression Test ◽  
Input Energy ◽  
Analysis Method ◽  
Compression Tests ◽  
Loading Rates

To investigate the energy evolution characteristics of sandstone under static-quasi-dynamic loading rates (1.0 × 10−3, 5.0 × 10−3, 1.0 × 10−2, 5.0 × 10−2, and 1.0 × 10−1 mm/s), the uniaxial compression tests, the uniaxial cyclic loading-unloading tests, and the uniaxial incrementally cyclic loading-unloading tests were conducted under five different loading rates. Through analysis of the elastic energy of the uniaxial cyclic loading-unloading test and the uniaxial incremental cyclic loading-unloading test, show that the impact of the loading rate and the cycle numbers on the elastic energy is less. Hence, we can deem that when the loads of the uniaxial incremental cyclic loading-unloading test and the uniaxial compression test are equal, the elastic energy of the two also equals. The energy in the uniaxial compression tests analyzed by the uniaxial incrementally cyclic loading-unloading test show that elastic energy increased linearly when the input energy increased under different loading rates. Through the linear energy storage law and the uniaxial incremental cyclic loading and unloading test, it is possible to analyze the energy in the uniaxial compression test at any loading rates. The results show that the greater the loading rate, the greater the peak elastic energy and peak input energy. But when the load is equal, the greater the loading rate, the smaller the input energy and elastic energy. Compared with traditional methods, the new energy analysis method is accurate and simple. Meanwhile, based on energy dissipation, the damage of rock during uniaxial compression tests was studied.

scholarly journals Comparison of Proctor and Uniaxial Compression Tests for Selected Soils

2018 ◽  
Vol 22 (1) ◽  
pp. 5-13
Author(s):  
Dariusz Błażejczak ◽  
Kinga Śnieg ◽  
Małgorzata Słowik
Keyword(s):  
Uniaxial Compression ◽  
Compression Test ◽  
Humus Content ◽  
Solid Particles ◽  
Dry Density ◽  
Uniaxial Compression Test ◽  
Compression Tests ◽  
Lateral Expansion ◽  
Soil Material ◽  
Uniaxial Test

AbstractThe objective of this paper was to compare the results of soil material compaction carried out with the use of the Proctor and uniaxial compression tests in order to find relations between these methods. Soil material in the form of loose mass was collected from the layer deposited at the depth from 35 to 60 cm in order to determine its typical properties (textural group, density of solid particles, humus content, reaction, plastic and liquid limits) and in order to compact it in the Proctor apparatus and in the uniaxial compression test. Results of both tests were used for construction of regression models reflecting the course of the unit stress (Pρdp), necessary to generate compaction equal to the dry density of solid particles obtained in the Proctor apparatus (ρdp) in relation to the sample moisture (ws). It was stated that the stress value Pρdp on the soil sample in the uniaxial compression test depends significantly on ws. It was proved that for the purpose of comparing the results of both tests, the uniaxial stress of samples must be performed in conditions of their lateral expansion. It was also proved that the use of the uniaxial test with possible lateral expansion of soil with a model sample, a diameter of which is 100 and the height is 30 mm, one may determine the obtained compaction with the use of the plate movement value.

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