scholarly journals Nonlinear Young’s Modulus of New Red Sandstone: Experimental Studies

Author(s):  
Evgenii Riabokon ◽  
Vladimir Poplygin ◽  
Mikhail Turbakov ◽  
Evgenii Kozhevnikov ◽  
Dmitrii Kobiakov ◽  
...  

AbstractYoung’s modulus of New Red Sandstone was investigated experimentally to gain insight into its nonlinear nature. A large experimental programme was carried out by applying a controllable quasi-static and dynamic uniaxial loading to 286 dry sandstone samples of four different sizes. The static and dynamic tests, similar to those aiming at determining the uniaxial compressive strength, were conducted using the state-of-the-art experimental facilities at the University of Aberdeen including a custom-built small experimental rig for inducing a dynamic uniaxial compressive load via a piezoelectric transducer. The obtained results have confirmed a complex nature of Young’s modulus of sandstone. Specifically, under a harmonic dynamic loading, it shows strongly nonlinear behaviour, which is hardening and softening with respect to frequency and amplitude of the dynamic loading, respectively.

2015 ◽  
Vol 52 (7) ◽  
pp. 961-970 ◽  
Author(s):  
Christopher T. Senseney ◽  
Jacob Grasmick ◽  
Michael A. Mooney

A dynamic finite element (FE) model of lightweight deflectometer (LWD) loading on a two-layer soil system, validated with an analytical solution and experimental data, is presented. Peak dynamic FE vertical deflections can be substantially different (almost always smaller) than FE static deflections. The numerically simulated measurement depth of the LWD center sensor is found to be 2–2.5 times the plate diameter, deeper than other experimental studies. Using the FE model, we conduct a sensitivity analysis of peak vertical deflections to the top layer Young’s modulus and underlying Young’s modulus of two-layer systems. Peak deflections from the center sensor are found to be more sensitive to the top layer Young’s modulus while peak deflections at radial offsets are found to be more sensitive to the underlying layer Young’s modulus. Sensitivities of layer moduli to FE deflections offer guidance in selecting weighting factors for the inverse solver in an LWD back-calculation procedure.


2020 ◽  
pp. 57-68
Author(s):  
N. Fialko ◽  
◽  
R. Dinzhos ◽  
V. Prokopov ◽  
Ju. Sherenkovsky ◽  
...  

Methods and results of experimental studies of thermophysical, structural and mechanical properties of low-heat-conducting polymer nanocomposites, oriented to use for gas ducts and chimneys of boiler installations, as well as various other gas and water communications are presented. In this work, on the basis of the performed set of methodological studies regarding the analysis of the legitimacy of using different models of heat conductivity for predicting the heat-conducting properties of these composites, the possibility of using for this prediction a number of models of the theory of the effective medium and the theory of percolation is considered. The analysis of thermophysical properties, structural characteristics and Young's modulus of low-heat-conductivity polymer nanocomposites based on polyethylene and polypropylene is carried out. Using these nanocomposites as an example, the achievement of a significant increase in their Young's modulus in comparison with unfilled polymers with a relatively small increase in heat conductivity is demonstrated. To obtain nanocomposites, we used a method based on mixing the components in a polymer melt using an extruder and then shaping the composite into the required shape by hot pressing. The method of differential scanning calorimetry was used to determine Young's modulus. On the basis of the studies carried out, the possibility of obtaining low-heat-conducting polymer nanocomposites with improved mechanical characteristics has been shown. In particular, it was shown that for nanocomposites based on polyethylene or polypropylene filled with CNTs (carbon nanotubes) or nanodispersed aerosil particles, with a mass fraction of the latter up to 2%, the following takes place a relatively insignificant increase in heat conductivity coefficients and a significant increase in the modulus of elasticity in tension. The research data also made it possible to obtain for the developed nanocomposites the temperature dependences of their specific mass heat capacity and, on this basis, to analyze the regularities of changes in the structural characteristics of these materials.


Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 427
Author(s):  
Tongxin Nie ◽  
Baomin Wang ◽  
Bo Liu ◽  
Yali Xie ◽  
Huali Yang ◽  
...  

The wrinkling structures, which can greatly improve the stretchability of the metallic thin films, have been widely used in the preparation of stretchable devices. However, the artificial wrinkling structures are often accompanied by the generation of microcracks, which seriously affect the performance of the devices. In this work, by establishing the corresponding model, the transverse strain of the longitudinally prestrained continuous film and the strip film is mechanically analyzed, which is verified by experimental results; for the strain of blank substrate, the error of the model was about 3.7%. It is difficult to avoid the generation of microcracks with continuous films, but strip films can avoid the generation of microcracks to a certain extent. The experimental results illustrate the various factors affecting the generation of microcracks. The transverse strain of the film is proportional to the substrate’s Young’s modulus, Poisson’s ratio, thickness, and prestrain and is basically inversely proportional to the strip film’s Young’s modulus, thickness, and strip interval. Our results provide deeper knowledge for choosing proper metallic materials to fabricate stretchable wrinkled devices.


2006 ◽  
Vol 21 (11) ◽  
pp. 2948-2954 ◽  
Author(s):  
Yi Zhang ◽  
Ephraim Suhir ◽  
Yuan Xu

We developed a methodology for the evaluation of the effective Young's modulus (EYM) of the vertically aligned carbon nanofibers array (CNFA). The carbon nanofibers array is treated in this study as a continuous structural element, and, for this reason, the determined EYM might be appreciably different (actually, lower) than the Young's modulus (YM) of the material of an individual carbon nanotube or a nanofiber. The developed methodology is based on the application of a compressive load onto the carbon nanofibers array, so that each individual carbon nanofiber experiences axial compression and is expected to buckle under the compressive load. The relationship between the applied compressive stress and the induced displacement of the carbon nanofiber array is measured using a table version of an Instron tester. It has been found that the carbon nanofiber array exhibits nonlinear behavior and the EYM increases with an increase in the compressive load. The largest measured EYM of the carbon nanofiber array turned out to be about 90 GPa. It has been found also that the fragmentary pieces of lateral graphitic layer in the carbon nanofiber array resulted in substantial worsening of the quality of the carbon nanofibers. This might be one of the possible reasons why the measured EYM turned out to be much lower than the theoretical predictions reported in the literature. The measured EYM is also much lower than the reported in the literature atomic force microscopy (AFM)-based data for the EYM for multiwalled carbon nanotubes (MWCNTs) that possess uniform and straight graphitic wall structure. Our transmission electron microscope (TEM) observations have revealed indeed poor structural qualities of the plasma-enhanced chemical vapor deposition (PECVD) grown CNFs.


Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6195
Author(s):  
Mikhail Guzev ◽  
Evgenii Kozhevnikov ◽  
Mikhail Turbakov ◽  
Evgenii Riabokon ◽  
Vladimir Poplygin

Under dynamic loading, the geomechanical properties of porous clastic rocks differ from those in quasistatic loading. A small experimental rig was built to directly assess the influence of vibrations on the uniaxial compressive strength (UCS), Young modulus, and Poisson’s ratio. A piezoelectric actuator powered by a signal from an oscillator was used in the rig as a generator of vibrations. A laser sensor and eddy current probe measured the longitudinal and transverse deformation. Tinius Hounsfield and Instron Series 4483 installations were used to determine the geomechanical properties of new red sandstone in a quasistatic regime. The boundaries of elastic deformations determined in the quasistatic loading were implemented in the dynamic loading. To perform the experiments in the elastic zone (on the graph of stress (σ)–strain (ε)), small samples with diameters ranging between 7.5 and 24.7 mm were manufactured. The investigation demonstrated that the Young’s modulus of the sandstone increased with increasing values of the dynamic load and frequency.


1995 ◽  
Vol 117 (3) ◽  
pp. 266-271 ◽  
Author(s):  
Vijay K. Goel ◽  
Steven A. Ramirez ◽  
Weizeng Kong ◽  
Lars G. Gilbertson

Bone remodeling theory based on strain energy density (SED) as the feedback control variable was used in conjunction with the finite element method to analyze the shape of the vertebral bodies within the ligamentous motion segment. The remodeling theory was once again applied to the altered two motion segments model to predict the Young’s modulus distribution of the cancellous bone within the vertebral bodies. A three-dimensional finite element model of the two motion segments ligamentous lumbar spine (L3-5) was developed. Bone remodeling response (external as well as internal) of the motion segments to a uniaxial compressive load of 424.7 N was studied. The external shape of the converged model matched the normal shape of a vertebral body. The internal remodeling resulted in regional cancellous bone Young’s moduli (or bone density) distributions similar to those reported in the literature; posterocentral regions of the vertebrae were predicted to have greater values of the elastic modulus than that of the outer regions. The results of the present study suggest that vertebral body assumes an adequate/optimum structure in terms of both its shape and its elastic moduli distribution within the cancellous region in response to the applied load. Extensions of the present model and its clinically relevant applications are discussed.


2015 ◽  
Vol 21 (2) ◽  
pp. 185-192 ◽  
Author(s):  
Katalin Szilágyi ◽  
Adorján Borosnyói ◽  
István Zsigovics

Surface hardness testing of materials can be considered as the oldest method to get information about strength related material properties. In recent decades the rebound hammer has been the most popular surface hardness testing device for concrete uniting the advantages of its predecessors. In the technical literature numerous proposals are available for simple, two-parameter regression analyses of rebound surface hardness vs. compressive strength relationship of concrete. The remarkable diversity of the proposed curves implies the need of the more than two-parameter regression techniques to reveal the most pronounced parameters governing hardness behaviour. The objectives of present experimental studies were to carry out dynamic and static hardness tests, Young’s modulus and compressive strength tests on concrete specimens. From the development of the tested properties with time it can be concluded that the rebound hammers provide a hardness value for high strength concretes connected to the Young’s modulus rather than the compressive strength. Present paper includes a parametric simulation and a parameter fitting of the verified phenomenological constitutive model of the authors which recognizes the w/c ratio as the main driver of the interrelated material properties and gives a realistic formulation for the time dependent behaviour of the rebound surface hardness of concrete.


Sign in / Sign up

Export Citation Format

Share Document