Determination Of Elastic Modulus Research Articles

Investigations on the Characterization of Various Adhesive Joints by Means of Nanoindentation and Computer Tomography

The mechanical properties of cured wood adhesive films were tested in a dry state by means of nanoindentation. These studies have found that the application of adhesives have an effect on the accuracy of the hardness and elastic modulus determination. The highest values of hardness among the tested adhesives at 20 °C have condensation resins: MF (0.64 GPa) and RPF (0.52 GPa). Then the decreasing EPI (0.43 GPa), PUR (0.23 GPa) and PVAc (0.14 GPa) adhesives. The values of the elastic modulus look a little bit different. The highest values among the tested adhesives at 20 °C have EPI (11.97 GPa), followed by MF (10.54 GPa), RPF (7.98 GPa), PVAc (4.71 GPa) and PUR (3.37 GPa). X-ray micro-computed tomography was used to evaluate the adhesive joint by the determination of the voids. It has been proven that this value depends on the type of adhesive, glue quantity and reactivity. The highest values of the void ratio achieve the PUR (17.26%) adhesives, then PVAc (13.97%), RRF (6.88%), MF (1.78%) and EPI (0.03%). The ratio of the gaps increases with the higher joint thickness. A too high proportion of voids may weaken the adhesive joint.

Determination of Polypropylene Fiber-Reinforced Concrete Compressive Strength and Elasticity Modulus via Ultrasonic Pulse Tests

Compressive strength and elasticity modulus are the main mechanical properties of concrete. The non-destructive ultrasound pulse test can be used to determine these properties without compromising the structure’s integrity. This study seeks to assess whether a correlation exists (1) between the Reinforcement Index (RI) and the mechanical properties, (2) between the RI and the dynamic properties, and (3) among the dynamic properties of polypropylene fiber-reinforced concrete. The RI was modified through fiber volume fraction (0, 0.4, 0.8 and 1.2%) and fiber length (40, 50 and 60 mm). The dynamic properties were assessed through dynamic elasticity modulus and ultrasonic pulse velocity (UPV), which were determined by direct, semi-direct, and indirect prospect methods. Finally, compressive strength, static elasticity modulus, and Poisson’s ratio were assessed through destructive tests. Their relationship with UPV and the dynamic elasticity modulus is also subsequently studied. The results reveal a correlation between RI and compressive strength and UPV; however, the static elasticity modulus only exhibits a correlation with UPV in one of its measurement methods. Finally, empirical models were developed for predicting compressive strength, elasticity modulus as a function of ultrasonic pulse velocity and RI, and dynamic elasticity modulus as a function of compressive strength and RI.

Machine learning framework for determination of elastic modulus without contact model fitting

Many contact models have been proposed for determining the elastic modulus of materials based on AFM force measurement. However, contact model fitting could be a challenging task since the elastic modulus usually varies depending on the tip parameters (i.e., radius and half-opening angle) which are difficult to determine in practice. Therefore, this study proposes a supervised machine learning (SML) regression framework for determining the elastic modulus without the need to either select an appropriate contact model or perform contact model fitting. In the proposed approach, the SML regressor learns the relationship between the force-displacement (FZ) features and the elastic modulus, and then predicts the elastic modulus of unseen samples directly from their FZ features. The predictive power of the proposed framework is demonstrated using both homogeneous materials (polydimethylsiloxane, polymethyl methacrylate, and polyvinyl alcohol), and heterogeneous materials (Staphylococcus aureus bacteria and methylammonium lead iodide). It is shown that the Gaussian process regression (GPR) model achieves a higher prediction accuracy than the multiple linear regression (MLR), random forest (RF), and support vector regression (SVR) models for both groups of materials. Particularly, GPR achieves a testing coefficient of determination value of up to 91.55% for homogeneous materials, and 82.73% for heterogeneous materials. Overall, the results confirm that the proposed SML regression framework is capable of determining the elastic modulus of both homogeneous and heterogeneous materials without the need for both contact model fitting and knowledge of tip shape.

Giant magnetostriction in low-concentration magnetorheological elastomers

Magnetorheological elastomers (MREs) are smart composite materials that can vary their mechanical properties under the influence of an external magnetic field. In the present work, we report the giant magnetostriction of low-concentration isotropic and anisotropic MREs, by combining a soft elastomer matrix with helicoidal-shaped particles. Magnetic characterization has shown high magnetic sensitivity of the anisotropic MREs near H ≅ 0, which can be up to 400% larger comparing to the isotropic counterparts. The determination of tensile elastic modulus (E) of the MREs indicates that the anisotropic samples become softer when the magnetic field is increased from H = 0 to H = 200 Oe. Due to the higher field sensitivity of the anisotropic composites, the magneto-induced elongation contributes to the increase in the overall strain when measuring the elastic modulus at low deformation. This compliance of the MRE explains the decrease in E from H = 0 to H = 200 Oe. Magnetostriction measurements were performed and giant strain values up to 3731 ppm were obtained for isotropic samples with 3.4 vol% of Hiperco particles under a field of H = 3500 Oe. This result stands out from the literature due to the giant induced elongation, with reduced volume fraction of particles. The developments of this work are a step forward on improving smart and efficient composites, that can have many applications, such as switches, controllable valves, and vibration attenuators.

High-throughput characterization of mechanical parameters of thin-film array

The thin-film array is a typical multi-film structure in material genetic engineering. With the requirements for rapid and efficient characterization of new film materials, a high-throughput characterization method based on digital image correlation for mapping the film elastic modulus and Poisson’s ratio of thin-film arrays is developed. First, a high-throughput experimental structure and testing system for the film array are designed, from which we can load 10 × 10 circular film arrays in the range of 0–25 kPa and obtain the full-field bulging displacement. Then, the experimental results are combined with the surface wave velocity equation to decouple the elastic modulus and Poisson’s ratio of the film array. The results are consistent with the material manual parameters, which verifies the feasibility of the high-throughput test method proposed in this article. When the method in this paper is applied to gradient materials, high-throughput testing of the mechanical parameters of a variety of film materials can be achieved. The results show that this method is valuable for quick, reliable and high-throughput determination of the film elastic modulus and Poisson’s ratio in material genetic engineering.

Experimental determination of the dynamic elastic modulus of polymeric soft materials in an extended frequency range: A supported free loading-mass method

In this paper, an experimental test method to accurately measure the complex dynamic elastic modulus of soft materials designed for anti-vibration purposes over a wide frequency range with high resolution at low uncertainty levels is proposed and applied to six polymeric soft materials. The proposed experimental technique, based on standardized test set-up and laser-Doppler velocimetry, is conceived to provide the uniaxial dynamic modulus of these materials on the basis of the exact solution of the Newton’s second law differential equation of a free loading-mass supported by a spring-damper system and subjected to an underlying dynamic stress. After a preliminary characterization with different standard procedures, the dynamic elastic modulus and damping properties of the six materials are investigated over a frequency range of 25–1000 Hz. The overall expanded uncertainty, on average around 3 %, is determined from five repeated measurements including the instrumental uncertainty. Results are compared with the standard ones.

Determination of dynamic elastic modulus of materials under a state of simple stresses by using electrodynamic actuators in beam-type mechanical elements

The dynamic elastic modulus is an important parameter for the study of solid mechanical elements. Even though there exist several well-established standardized methods that allow determining this parameter under a state of simple stresses, some of these may require sophisticated laboratory equipment or involve the use of multiple devices (impulser, sensor transducer…). The main purpose of this work is to propose an alternative approach that uses a single electrodynamic actuator both as an impulse exciter and vibration sensor simultaneously. By generating a random signal excitation and measuring the electrical input impedance of the actuator when coupled to a beam-type cylindrical element, the fundamental flexural mode of vibration of the latter can be identified and the dynamic elastic modulus of its material determined in a simple and straightforward manner. Preliminary experiments were performed over different size beams with rectangular cross-sections made of natural stone, marble, wood, and aluminium. Results were compared to those obtained using the standardized procedure described in the ASTM E1876 for the same specimens, these showing a good agreement in terms of dynamic elastic modulus.

A new design of SiO2–Na2O–Al2O3 glass–ceramic and determination of elastic modulus and density of states via molecular dynamics simulations based on density functional tight-binding calculations

A new design of SiO2–Na2O–Al2O3 glass–ceramic and determination of elastic modulus and density of states via molecular dynamics simulations based on density functional tight-binding calculations

Determination of the Elastic Modulus of Wear Resistant Coatings by Quantitative Acoustic Microscopy

Abstract For the quality assessment of coatings there is an increasing need of test methods which are able to fulfil the requirements to a high reliability of the test results. The exact knowledge of the coating properties and their objective assessment helps the coating industry for an optimum coating development as well as the user which will use the coated parts under a specific purpose. As part of an European project four laboratories deal with the determination of elastic moduli of hard coatings by means of quantitative acoustic microscopy. On titanium nitride coatings and C doped chromium coatings on M2 tool steel basic and continuing research studies were accomplished, guidelines have been developed and proofed in round-robin tests.

Experimental determination of higher order elastic moduli of metallic glasses

We studied the effect of uniaxial compression on longitudinal and transverse ultrasonic resonant vibrations (8–10 MHz) in Zr57Nb5Al10Cu15.4Ni12.6 (VIT106) metallic glass in the initial and relaxed states. On this basis, the 3rd- and 4th-order elastic moduli are determined. We also corrected previous calculations of the parameters of sound propagation vs the applied load and re-examined earlier estimates of higher order elastic moduli in other metallic glasses. To our knowledge, any other estimates of the 4rd-order elastic moduli of metallic glasses based on experimental observations are absent in the literature. The obtained data are discussed in the framework of available theoretical predictions.

Functional mechanical attributes of natural and synthetic gel-based scaffolds in tissue engineering: strain-stiffening effects on apparent elastic modulus and compressive toughness

The accurate identification and determination of elastic modulus and toughness, as well as other functional mechanical attributes of artificial tissues, are of paramount importance in several fields of tissue science, tissue engineering and technology, since biomechanical and biophysical behavior is strongly linked to biological features of the medical implants and tissue-engineering scaffolds. When soft or ultra-soft materials are investigated, a relevant dispersion of elastic modulus values can be achieved, due to the strain-stiffening effects, inducing a typical non-linear behavior of these materials, as a function of strain-range. In this short communication, the Apparent elastic modulus strain-range dependence is estimated from a segmentation of the strain stiffening curve, and the related compressive toughness is investigated and discussed, based on experimental evidence, for 6 different kinds of gels, used for artificial tissue fabrication; experimental results are compared to mechanical properties of native human tissues.

A face-contact connector for modularized floating structures

For a large modularized floating structure, the connection load between adjacent modules could be tremendous under wave excitations. Traditional articulated connection method hardly meets the requirements of structural strength at connection. It has become a major technical obstacle in the connector design. For this reason, a new type of face-contact (FC) connector is proposed here. The core idea is to disperse the huge connection load to the whole end face of modules, so as to significantly reduce the local stress level at connection areas. The face-contact connector is composed of a group of cables and cushions with the mechanism of quick assembly and release. The network modeling method and finite element method (FEM) are used to evaluate the performance of the FC connector. A numerical example of a serially connected pontoon-type floating system is conducted to show the design procedure that includes the layout of the cables and cushions, the selection of wave condition, the determination of cable stiffness and elasticity modulus of cushions based on a proposed evaluation function. The evaluation function is a comprehensive index to assess the balance among the module responses, connection loads and strength redundancy according to designer's preference. The results indicate that the face-contact connector is much easier to meet the strength requirement comparing with the traditional hinged connectors.

Extended characterization of materials based on continuous instrumented indentation diagrams

In addition to the traditional determination of hardness and elastic moduli from continuous diagrams of instrumental indentation, it is proposed to determine the yield stress, the characteristic of plasticity, the characteristic relative size of the elastoplastic zone under the indenter, and the volumetric deformation of the material in the area of contact of the indenter with the sample. The indentation diagram shows the transition point to the unconstrained material flow under the indenter. Keywords: indentation, hardness, elastic moduli, contact stiffness, elastic-plastic strains.

Theoretical determination of elastic and flexural modulus for inter-ply and intra-ply hybrid composite material

In this paper a theoretical analysis for determination of elastic and flexural modulus of natural fibre reinforced hybrid composite is proposed. The proposed analytical model is based on the classical lamination approach to predict the theoretical modulus. Experimental tensile and 3-point bending tests were carried out using standard specimens of inter and intra-ply hybrid composite materials. The elastic and flexural modulus predicted by the new approach showed a better agreement with the experimental results, with a maximum deviation of 11.21% and 11.65 % respectively. From the results it was observed that the theoretical value of elastic and flexural modulus was not accurately predicted by rule of hybrid mixture method. The proposed approach can be adopted as a primary tool to predict the modulus of the composite and it can also be used to optimise the composite parameters such as volume fraction of fibre, ply and fibre orientation, etc. for the maximum performance.

Determination of the intrinsic elastic modulus, hardness and fracture strength of thermally growth oxide by nanoindentation and tensile tests

Thermally growth oxide (TGO) is formed between ceramic coat and bond coat during the service of thermal barrier coatings (TBCs). Characterization of the mechanical properties of the TGO layer is important for simulating the stress or predicting the failure of TBCs. Based on nanoindentation and tensile methods, the elastic modulus, hardness and fracture strength of TGO are obtained. Due to the influence of the indentation size effect (ISE), the measured indentation hardness and elastic modulus of TGO decrease with increasing indentation depth. These values are much smaller than those of bulk alumina. By analyzing the ISE, the intrinsic hardness and elastic modulus of TGO are obtained as 13.58 GPa and 326.46 GPa, respectively. The residual stress in TGO with the value of 133.1 MPa is determined by XRD method. Combining the tensile tests with a digital image correlation (DIC) method, the tensile fracture strain and fracture strength of TGO are determined to be 0.25% and 683 MPa, respectively.

Determination of the high-strain rate elastic modulus of printing resins using two different split Hopkinson pressure bars

The usage of resin-based materials for 3D printing applications has been growing over the past decades. In this study, two types of resins, namely a MMA-based resin and an ABS-based tough resin, are subjected to compression tests on a split Hopkinson pressure bar to deduce their dynamic properties under high strain rate loading.Two Hopkinson bar setups are used, the first one is equipped with aluminum bars and the second one with PMMA bars. From the measured strain waves, elastic moduli at high strain rates are derived. Both setups lead to values of E=3.4–3.8 GPa at a strain rate of about 250 s−1. Numerical simulations support the experiments. Moreover, considering the waves gained from the two different bar setups, PMMA bars appear to be well-suited for testing resin samples and are therefore recommended for such applications.

Using non-destructive testing to assess static elastic modulus of a limestone exposed to high temperatures

The determination of static elastic modulus in the laboratory requires rock core extraction and the subsequent testing of the samples by means of standardised uniaxial compressive strength tests. However, this destructive procedure is not always suitable – as in the case of protected historic buildings. In these cases, the static elastic modulus can be obtained from the dynamic elastic modulus, in turn derived from the velocity of ultrasonic waves (a non-invasive and non-destructive test). The relationship between both the dynamic and static moduli of rocks has been extensively addressed in the scientific literature. Furthermore, several researchers have separately studied the evolution of static or dynamic elastic moduli of rocks exposed to high temperatures – although few studies have compared both values. It is well known that the dynamic modulus is generally higher than the static modulus, and the values diverge especially in rocks with a low modulus of elasticity. These differences can be mainly explained by the effect of porosity and the size of cracks in the determination of both parameters. In this research, the relationship between static and dynamic moduli for ‘Borriol’ limestone is studied for samples previously subjected to 200, 400, 600 and 800 °C and then cooled slowly (in air) or quickly (immersed in water). The results show that the static modulus of samples heated up to 600 °C decreased 80.9 and 79.1 % and dynamic modulus decreased 62.5 and 64.8 % for slow and quick cooling samples, respectively. For samples heated to 600 and 800 °C, the static and dynamic moduli are similar. In general, no significant differences between both cooling methods are observed, even though static modulus shows more loss than dynamic modulus. Finally, linear models were used to correlate static and dynamic moduli, providing coefficients of determination of 0.99 and 0.97, for slow and quick cooling, respectively. It is also remarkable that the Edyn/Est rate was smaller than 1 for elastic moduli over 30 GPa (i.e., 105, 200 and 400 °C) and greater than 1 for lower moduli (i.e., 600 and 800 °C). The results obtained can be used to calculate the static elastic modulus of ‘Borriol’ limestone from dynamic modulus determined by non-destructive techniques.

Determination of elastic modulus of quartz glass using digital speckle pattern interferometry

Determination of elastic modulus of quartz glass using digital speckle pattern interferometry

ВАЛИДИЗАЦИЯ НАИБОЛЕЕ ИНФОРМАТИВНЫХ МЕТОДИК УЛЬТРАЗВУКОВОЙ ДИАГНОСТИКИ ВИСЦЕРАЛЬНОГО ОЖИРЕНИЯ

Objectives. To validate the ultrasound method of diagnosing visceral obesity in patients with cardiovascular diseases and metabolic syndrome. Material and methods. The study involved 115 people aged from 19 to 60 years, who represented a continuous random sample (examination sample). The diagnostic efficacy of shear wave ultrasound elastography of the lower perirenal visceral adipose tissue (VAT) was evaluated in 59 patients. Ultrasound examination was performed on the Logiq E9 ultrasound machine (GE Healthcare, USA); convex 3.5 MHz and linear 10.0 MHz sensors were used. Results. To assess visceral obesity, the following measurements are recommended: the area of the lower perirenal adipose tissue (AT), the distance between the surface of the rectus abdominis muscle and the anterior wall of the aorta, the thickness of the epicardial and pericardial AT, as well as the elastography of the lower part of the perirenal AT. According to the results of the performed validation of ultrasound VAT measuring techniques, the accuracy of visceral obesity diagnosing in patients with arterial hypertension with the use of the boundary values of the lower part perirenal AT area made up 87.8%. The accuracy of visceral obesity diagnosing in patients with coronary heart disease, taking into account the boundary values of the epicardial AT thickness equalled 86.2%, and pericardial AT thickness amounted to 95.4%. Diagnosing of visceral obesity in patients with metabolic syndrome by measuring four ultrasound parameters (area of the lower part of perirenal AT, thickness of intraabdominal AT, epicardial and pericardial VAT) was carried out with an accuracy of 86.1%. Elastic modulus determination during elastography of the lower part of the perirenal AT using the boundary values, established for patients with metabolic syndrome, was performed with an accuracy of 91.5%.

Uncertainty in the determination of elastic modulus by tensile testing

The paper presents the results of theoretical and experimental research related to the uncertainty in the elastic modulus measurement on different types of tensile testing devices and their comparison. Factors that affect the uncertainty in the measurement of the elastic modulus were defined. Analytical limits of the uncertainty in the elastic modulus, i.e. the limits of “acceptable” uncertainties, were determined. The mean values of the uncertainties in the elastic modulus are 1.97% on a conventional tensile testing device with an extensometer and 1.56% on a small laboratory tensile testing device. In the region of lower forces and small elongations, the uncertainty in the elastic modulus measurement has higher values, which is primarily caused by the imperfections of measuring instrumentation.