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Sas, Wojciech, Katarzyna Gabryś, Emil Soból i Alojzy Szymański. "Nonlinear dynamic properties of silty clay from Warsaw area". Annals of Warsaw University of Life Sciences – SGGW. Land Reclamation 48, nr 3 (1.09.2016): 201–20. http://dx.doi.org/10.1515/sggw-2016-0016.
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Abstract In this work, the small-strain and nonlinear dynamic properties of silty clay samples were studied by means of the low- and high-amplitude resonant column (RC) tests at various mean effective stresses (p’). The tested specimens were collected from the centre of Warsaw, district Śródmieście. Initially, the low-amplitude tests (below 0.001%) were conducted. Subsequently, the nonlinear testing was performed, at shearing strains greater than 0.001%. These tests were carried out in order to receive the dynamic properties of silty clay specimens in the nonlinear shear strain range. The small-strain material damping ratios (Dmin) of silty clay samples were also measured during the low-amplitude resonant column testing. The results show that increasing shear strain (γ) above the elastic threshold (γte) causes a decrease of the shear modulus (G) and normalized shear modulus (G/Gmax) of analyzed soil samples. Simultaneously, it is observed a increase of its damping ratio (D) and normalized damping (D/Dmin) with increasing shear strain (γ). Predictive equations for estimating normalized shear modulus and material damping of silty clay soils were presented here as well. The equations are based on a modified hyperbolic model and a statistical analysis of the RC tests results. The influence of unloading process on dynamic properties of the tested material was also discussed in the paper.
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Song, Binghui, Angelos Tsinaris, Anastasios Anastasiadis, Kyriazis Pitilakis i Wenwu Chen. "Small to medium strain dynamic properties of Lanzhou loess, China". Soil Dynamics and Earthquake Engineering 163 (grudzień 2022): 107454. http://dx.doi.org/10.1016/j.soildyn.2022.107454.
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Kyei-Manu, William Amoako, Charles R. Herd, Mahatab Chowdhury, James J. C. Busfield i Lewis B. Tunnicliffe. "The Influence of Colloidal Properties of Carbon Black on Static and Dynamic Mechanical Properties of Natural Rubber". Polymers 14, nr 6 (16.03.2022): 1194. http://dx.doi.org/10.3390/polym14061194.
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The influence of carbon black (CB) structure and surface area on key rubber properties such as monotonic stress-strain, cyclic stress–strain, and dynamic mechanical behaviors are investigated in this paper. Natural rubber compounds containing eight different CBs were examined at equivalent particulate volume fractions. The CBs varied in their surface area and structure properties according to a wide experimental design space, allowing robust correlations to the experimental data sets to be extracted. Carbon black structure plays a dominant role in defining the monotonic stress–strain properties (e.g., secant moduli) of the compounds. In line with the previous literature, this is primarily due to strain amplification and occluded rubber mechanisms. For cyclic stress–strain properties, which include the Mullins effect and cyclic softening, the observed mechanical hysteresis is strongly correlated with carbon black structure, which implies that hysteretic energy dissipation at medium to large strain values is isolated in the rubber matrix and arises due to matrix overstrain effects. Under small to medium dynamic strain conditions, classical strain dependence of viscoelastic moduli is observed (the Payne effect), the magnitude of which varies dramatically and systematically depending on the colloidal properties of the CB. At low strain amplitudes, both CB structure and surface area are positively correlated to the complex moduli. Beyond ~2% strain amplitude the effect of surface area vanishes, while structure plays an increasing and eventually dominant role in defining the complex modulus. This transition in colloidal correlations reflects the transition in stiffening mechanisms from flexing of rigid percolated particle networks at low strains to strain amplification at medium to high strains. By rescaling the dynamic mechanical data sets to peak dynamic stress and peak strain energy density, the influence of CB colloidal properties on compound hysteresis under strain, stress, and strain energy density control can be estimated. This has considerable significance for materials selection in rubber product development.
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KREN, Alexander P. "IMPACT INDENTATION OF METALS AT THE SMALL ELASTOPLASTIC STRAIN". Mechanics of Machines, Mechanisms and Materials 1, nr 58 (marzec 2022): 56–63. http://dx.doi.org/10.46864/1995-0470-2022-1-58-56-63.
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The aim of this paper is to study and describe the behavior features of metals under impact loading in the area of elastic-plastic transition, with strains not exceeding 3–4 %, which are typical for measuring the hardness of materials during dynamic indentation. It has been established that until the state of full plasticity is reached, the excess of the dynamic hardness over the static one cannot be explained only by an increase of the strain rate and requires taking into account the elastic properties of the material. It is shown that a grow of the yield stress and the part of elastic deformation leads to a significant increase in the dynamic hardness of the material. This is due to the feature of measurements, which consists in fixing the value of the initial impact energy, which is distributed between elastic and plastic part of strain, depending on the characteristics of the material: yield stress, elastic modulus, strain-hardening coefficient.
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Jafarian, Yaser, i Hamed Javdanian. "Small-strain dynamic properties of siliceous-carbonate sand under stress anisotropy". Soil Dynamics and Earthquake Engineering 131 (kwiecień 2020): 106045. http://dx.doi.org/10.1016/j.soildyn.2020.106045.
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Lei, Xudong, Kailu Xiao, Xianqian Wu i Chenguang Huang. "Dynamic Mechanical Properties of Several High-Performance Single Fibers". Materials 14, nr 13 (25.06.2021): 3574. http://dx.doi.org/10.3390/ma14133574.
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High-performance fiber-reinforced composites (FRCs) are widely used in bulletproof structures, in which the mechanical properties of the single fibers play a crucial role in ballistic resistance. In this paper, the quasi-static and dynamic mechanical properties of three commonly used fibers, single aramid III, polyimide (PI), and poly-p-phenylenebenzobisoxazole (PBO) fibers are measured by a small-scale tensile testing machine and mini-split Hopkinson tension bar (mini-SHTB), respectively. The results show that the PBO fiber is superior to the other two fibers in terms of strength and elongation. Both the PBO and aramid III fibers exhibit an obvious strain-rate strengthening effect, while the tensile strength of the PI fiber increases initially, then decreases with the increase in strain rate. In addition, the PBO and aramid III fibers show ductile-to-brittle transition with increasing strain rate, and the PI fiber possesses plasticity in the employed strain rate range. Under a high strain rate, a noticeable radial splitting and fibrillation is observed for the PBO fiber, which can explain the strain-rate strengthening effect. Moreover, the large dispersion of the strength at the same strain rate is observed for all the single fibers, and it increases with increasing strain rate, which can be ascribed to the defects in the fibers. Considering the effect of strain rate, only the PBO fiber follows the Weibull distribution, suggesting that the hypothesis of Weibull distribution for single fibers needs to be revisited.
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Gao, Shuling, i Guanhua Hu. "Experimental Study on Biaxial Dynamic Compressive Properties of ECC". Materials 14, nr 5 (6.03.2021): 1257. http://dx.doi.org/10.3390/ma14051257.
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An improved hydraulic servo structure testing machine has been used to conduct biaxial dynamic compression tests on eight types of engineered cementitious composites (ECC) with lateral pressure levels of 0, 0.125, 0.25, 0.5, 0.7, 0.8, 0.9, 1.0 (the ratio of the compressive strength applied laterally to the static compressive strength of the specimen), and three strain rates of 10−4, 10−3 and 10−2 s−1. The failure mode, peak stress, peak strain, deformation modulus, stress-strain curve, and compressive toughness index of ECC under biaxial dynamic compressive stress state are obtained. The test results show that the lateral pressure affects the direction of ECC cracking, while the strain rate has little effect on the failure morphology of ECC. The growth of lateral pressure level and strain rate upgrades the limit failure strength and peak strain of ECC, and the small improvement is achieved in elastic modulus. A two-stage ECC biaxial failure strength standard was established, and the influence of the lateral pressure level and peak strain was quantitatively evaluated through the fitting curve of the peak stress, peak strain, and deformation modulus of ECC under various strain rates and lateral pressure levels. ECC’s compressive stress-strain curve can be divided into four stages, and a normalized biaxial dynamic ECC constitutive relationship is established. The toughness index of ECC can be increased with the increase of lateral pressure level, while the increase of strain rate can reduce the toughness index of ECC. Under the effect of biaxial dynamic load, the ultimate strength of ECC is increased higher than that of plain concrete.
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Deng, Ji Wei, Chang Wu Liu i Jian Feng Liu. "Effect of Dynamic Loading on Mechanical Properties of Concrete". Advanced Materials Research 568 (wrzesień 2012): 147–53. http://dx.doi.org/10.4028/www.scientific.net/amr.568.147.
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Concrete structures have to bear dynamic loads in daily work, strength and deformation characteristics of concrete under dynamic loads differ from the characteristics under static loads, and this difference may become a key factor to restrict the structural safety under certain conditions. Using the MTS815 test system, the dynamic uniaxial compression tests of concrete specimens were conducted. The mechanical characteristic parameters of strength, elastic modulus, peak strain and the stress-strain curves at different loading rates of concrete specimens have been studied. The results reveal that concrete is a rate-sensitive material, as a small loading rate may lead to the rapid growth of strength; the variation rule of peak strain is not obvious with the increase of loading rate, thus the peak strain can be regarded as a fixed value in actual projects; the higher the loading rate is, the greater the concrete strength and the elastic modulus are; the elastic modulus increases essentially due to the improvement of structural stiffness; concrete specimens with the same mix proportion have similar stress-strain curves and the loading rate has little effect on the shape of the curve.
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Yang, Jie, Xin Cai, Yangong Shan, Miaomiao Yang, Xingwen Guo i Jinlei Zhao. "Small-Strain Dynamic Properties of Lean Cemented Sand and Gravel Materials under Different Cementing Agent Contents". Advances in Civil Engineering 2020 (24.11.2020): 1–13. http://dx.doi.org/10.1155/2020/8878506.
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Lean cemented sand and gravel (LCSG) materials are increasingly being used in dams, embankments, and other civil engineering applications. Therefore, their mechanical properties and stress-strain behavior should be systematically understood. In this study, the small-strain dynamic properties of LCSG materials were examined. A series of dynamic triaxial tests were performed to investigate the effects of the confining pressure and cementing agent content of the material on its dynamic shear modulus (Gd) and damping ratio (λ). The results show that Gd increased and λ decreased with increasing confining pressure and cementing agent content; however, under the same confining pressure and cementing agent content, Gd decreased gradually in accordance with shear strain. Furthermore, new expressions were derived for Gd and λ, as well as for their maxima. The results of this study could provide a reference for practical engineering applications, including the construction of dams using LCSG materials.
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Kang, Gyeong-o., Woong Choi i Changho Lee. "Prediction of Small-Strain Dynamic Properties on Granulated Spherical Glass Bead-Polyurethane Mixtures". Advances in Civil Engineering 2019 (12.09.2019): 1–12. http://dx.doi.org/10.1155/2019/6348326.
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This paper aims to propose predictive equations for the small-strain shear modulus (Gmax) and small-strain damping ratio (Dmin) of a granulated mixture with plastic and nonplastic materials to reduce the dynamic energy of the ground. Polyurethane bead (PB) and glass bead (GB) were used as the plastic and nonplastic materials, respectively. 180 resonant-column tests were conducted with various conditions affecting the dynamic properties, such as nonplastic particle content (PC), void ratio (e), particle-size ratio (sr), and mean effective confining pressure (σm′). The results showed that Gmax and Dmin, respectively, increased and decreased as e decreased with increasing σm′ of material mixtures. In addition, Gmax decreased with an increase in PC, whereas Dmin increased. It was also found that sr of materials affected the changes in Gmax and Dmin. With an increase in sr, Gmax increased while Dmin decreased because small particles do not hinder the behavior of large particles as the size of larger particles increases. Finally, based on the results, new equations for estimating Gmax and Dmin of a granulated mixture with PB and GB were proposed as functions of PC, e, median grain size (D50), and σm′.
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Lang, Lei, Fudong Li i Bing Chen. "Small-strain dynamic properties of silty clay stabilized by cement and fly ash". Construction and Building Materials 237 (marzec 2020): 117646. http://dx.doi.org/10.1016/j.conbuildmat.2019.117646.
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Kikuchi, Takehito, Yusuke Kobayashi, Mika Kawai i Tetsu Mitsumata. "Elastic Properties of Magnetorheological Elastomers in a Heterogeneous Uniaxial Magnetic Field". International Journal of Molecular Sciences 19, nr 10 (6.10.2018): 3045. http://dx.doi.org/10.3390/ijms19103045.
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Magnetorheological elastomers (MREs) are stimulus-responsive soft materials that consist of polymeric matrices and magnetic particles. In this study, large-strain response of MREs with 5 vol % of carbonyl iron (CI) particles is experimentally characterized for two different conditions: (1) shear deformation in a uniform magnetic field; and (2), compression in a heterogeneous uniaxial magnetic field. For condition (1), dynamic viscoelastic measurements were performed using a rheometer with a rotor disc and an electric magnet that generated a uniform magnetic field on disc-like material samples. For condition (2), on the other hand, three permanent magnets with different surface flux densities were used to generate a heterogeneous uniaxial magnetic field under cylindrical material samples. The experimental results were mathematically modeled, and the relationship between them was investigated. We also used finite-element method (FEM) software to estimate the uniaxial distributions of the magnetic field in the analyzed MREs for condition (2), and developed mathematical models to describe these phenomena. By using these practicable techniques, we established a simple macroscale model of the elastic properties of MREs under simple compression. We estimated the elastic properties of MREs in the small-strain regime (neo–Hookean model) and in the large-strain regime (Mooney–Rivlin model). The small-strain model explains the experimental results for strains under 5%. On the other hand, the large-strain model explains the experimental results for strains above 10%.
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Hao, Shi Ming, Jing Pei Xie, Li Ben Li, Ai Qin Wang, Wen Yan Wang i Ji Wen Li. "Hot Deformation Behaviors and Microstructure Evolution of SiCp/Al Composites". Materials Science Forum 849 (marzec 2016): 430–35. http://dx.doi.org/10.4028/www.scientific.net/msf.849.430.
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In order to explore the compressive properties of aluminium matrix composite reinforced with middle content SiC particles, hot compression behavior of 30%SiCp/2024A1 composite was investigated using Gleeble-1500 system at a temperatures range from 350 to 500°C and strain rates from 0.01 to 10 s−1. The associated structural changes were studied by OM, SEM and TEM observations. The results show that the true stress–true strain curves exhibited a peak stress at a small strain (<0.1), after which the flow stresses decreased monotonically until high strains, showing a dynamic flow softening. The stress level decreased with increasing deformation temperature and decreasing strain rate, indicating that the composite is a positive strain rate sensitive material. And therefore there will be a enough time for dynamic recrystallization to complete nucleation and growth at low strain rate and high deformation temperatures.
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GAMOTA, DANIEL R., i FRANK E. FILISKO. "LINEAR/NONLINEAR MECHANICAL PROPERTIES OF ELECTRORHEOLOGICAL MATERIALS". International Journal of Modern Physics B 06, nr 15n16 (sierpień 1992): 2595–607. http://dx.doi.org/10.1142/s0217979292001316.
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The stress response of an electrorheological (ER) material is modified by the application of an electric field. Various studies have shown that the ER material can behave as a linear viscous, linear viscoelastic, nonlinear viscoelastic, plastic, or viscoelastic-plastic body. Furthermore, several different experimental techniques are conducted to observe the ER material's behavior as a function of strain, strain frequency, field strength, and ER material concentration. Small amplitude dynamic studies are used to observe the ER material's linear viscoelastic properties, while moderate and large amplitude studies are used to observe the material's fundamental nonlinear dynamic properties. Finally, constant shear rate experiments are performed to observe the apparent viscosity of the ER material during flow conditions.
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Karimezadeh, Ali Akbar, Fardin Jafarzadeh, Anthony Kwan Leung i Adel Ahmadinezhad. "Very-small to large strain dynamic behaviour of unsaturated sand in a wide range of suction". E3S Web of Conferences 195 (2020): 03002. http://dx.doi.org/10.1051/e3sconf/202019503002.
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Shear modulus (Gmax at very small strain and G at large strain) and constraint modulus at very small strain (M) are important soil parameters for static and dynamic analysis in geotechnical applications. However, these dynamic properties of unsaturated soil are rarely reported. In this study, a cyclic simple shear apparatus was newly-modified for allowing both the shear and constrained moduli at both very small and large strains to be measured. Benders or ultrasonic sensors were embedded in an unsaturated soil sample for transmitting/receiving shear- and pressure-wave, respectively. Two very-small-strain tests were conducted to determine the Gmax, M and soil damping ratio of a sand for a wide range of suction covering from the boundary-effect, transition and residual zone of the water retention curve of the sand. In addition, six large-strain cyclic simple shear tests were carried out to investigate G. The test results showed that Gmax and M were approximately constant before reaching the air-entry value, but there was a significant increase in Gmax as the sand dried further. Yet, M dropped within the transition zone, and interestingly when the suction was beyond the residual value, M increased. M along the wetting path was higher than that along the drying path. The damping ratio, on the other hand, first reduced before reaching the air-entry value, but it increased at the transition zone and then decreased within the residual zone. At large strain, G/Gmax also increased as suction increased until reaching the residual zone, beyond which the normalised value show substantial decreased.
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Gookin, W. B., M. F. Riemer, R. W. Boulanger i J. D. Bray. "Development of Cyclic Triaxial Apparatus with Broad Frequency and Strain Ranges". Transportation Research Record: Journal of the Transportation Research Board 1548, nr 1 (styczeń 1996): 1–8. http://dx.doi.org/10.1177/0361198196154800101.
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A cyclic triaxial testing system capable of measuring very small to large strain properties on a single specimen has been developed by combining a wide variety of existing instrumentation, including piezoceramic bender elements, internal displacement measurement devices (both contact and noncontact), local displacement measurement devices, a sensitive internal load cell, and an external load cell. The bender elements provide information on soil properties in the nearly linear elastic (very small strain) range. Local and noncontact internal displacement measurements provide information about small strain range properties, whereas more traditional internal displacement measurements provide information in the small to large strain range. In addition, this apparatus can be used over a wide range of loading frequencies to investigate the effect of frequency on dynamic soil properties. By combining this equipment in a single testing system, a number of tests may be run on one specimen, eliminating the effects of variability. The broad variety of displacement measuring instruments also allows direct comparisons of these techniques on a single specimen.
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Wen, Liwei. "Effect of Mean Grain Size on the Small-Strain Dynamic Properties of Calcareous Sand". Advances in Civil Engineering 2022 (18.07.2022): 1–15. http://dx.doi.org/10.1155/2022/9291890.
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Calcareous sand was selected as the prior material for island reclamation in many coastal regions. The mechanical properties of the granular materials are greatly affected by their grain size distribution conditions. The shear modulus and damping ratio are two important parameters for earthquake ground response analysis and liquefaction evaluation. A series of resonant column tests had been performed on calcareous sands with varying median grain diameter and uniform coefficient. The dependence of the shear modulus and damping ratio of the calcareous sand on grain size has been confirmed in this examination. The test results reveal that the shear modulus decreases with a rise in shear strain for calcareous sand samples at a given confining pressure and relative density. The maximum shear modulus tends to increase with confining pressure and relative density. On the maximum shear modulus and void ratio plane, the trend lines of the measured results shift toward up and right position with a rise in grain diameter. The measured results indicate that the influence of uniform coefficient on the maximum shear modulus is neglectable. A revised empirical equation based on the Hardin model had been proposed considering the influence of grain diameter to estimate the maximum shear modulus of calcareous sand. The predicted values show satisfactory agreement with the measured results. The results manifest that the effect of grading condition on small-strain dynamic properties of calcareous sands cannot be neglected for the evaluation of seismic safety for reclamation engineering sites.
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Zekkos, Dimitrios, Jonathan D. Bray i Michael F. Riemer. "Shear modulus and material damping of municipal solid waste based on large-scale cyclic triaxial testing". Canadian Geotechnical Journal 45, nr 1 (styczeń 2008): 45–58. http://dx.doi.org/10.1139/t07-069.
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Representative dynamic properties of municipal solid waste (MSW) are required to perform reliable seismic analyses of MSW landfills. A comprehensive large-scale cyclic triaxial laboratory testing program was performed on MSW retrieved from a landfill in the San Francisco Bay area to evaluate the small-strain shear modulus, and strain-dependent normalized shear modulus reduction and material damping ratio relationships of MSW. The effects of waste composition, confining stress, unit weight, time under confinement, and loading frequency on these dynamic properties were evaluated. The small-strain shear modulus depends primarily on waste composition, confining stress, unit weight, and time under confinement. The normalized shear modulus reduction and material damping curves for MSW depend on waste composition and confining stress. Based on the results of this study and a review of literature, strain-dependent shear modulus reduction and material damping relationships are recommended for use in landfill design.
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Jaumouillé, V., J. J. Sinou i B. Petitjean. "Simulation of Payne Effect of Elastomeric Isolators with a Harmonic Balance Method". Shock and Vibration 19, nr 6 (2012): 1281–95. http://dx.doi.org/10.1155/2012/658960.
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In the presented work, a non linear effect of rubber referred as Fletcher-Gent effect or Payne effect is investigated. It leads to a change in the rubber dynamic modulus with vibration amplitudes and, consequently, modifies resonance frequencies of mechanical systems including non linear elastomers. In this study a new methodology is developed to take into account Payne effect in a linear viscoelastic rubber material. Small vibration amplitudes around a no-preloaded state are predicted by considering frequency and amplitude dependencies of the material. This methodology has the advantage of using tabular experimental data from characterization tests which avoids the development of a complex model. In order to compute frequency responses, the non linear harmonic balance method is used and, for each iteration, new rubber properties are affected at each element according to its strain state. An equivalent strain measure is evaluated from the element strain energy density. This equivalent strain allows to associate dynamic properties of a material element subjected to multiaxial strain state with experimental dynamic properties of a material sample subjected to an uniaxial strain state. Practically, DMAP alter procedures are developed in order to evaluate energies in models defined with MSC.Nastran and the non linear solver is developed with Matlab. The method is applied on a satellite instrument isolator including four non linear rubber mounts. A non homogeneous spatial distribution of element equivalent strains is observed. Moreover, the maximum equivalent strain varies with frequency. These two observations validate the use of a specific methodology to deal with amplitude dependency of rubber.
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Cheng, Xiang, Guangming Zhao, Yingming Li, Xiangrui Meng, Qingyi Tu i Chunliang Dong. "Experimental Study on Mechanical Properties and Energy Dissipation of Gas Coal under Dynamic and Static Loads". Advances in Civil Engineering 2020 (15.12.2020): 1–14. http://dx.doi.org/10.1155/2020/8815730.
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In order to study the mechanical properties and energy dissipation of gas coal under dynamic and static loads, the static loading and impact tests of different strain rates were carried out by the testing systems of SZW-1000 microcomputer servo pressure tester and separated Hopkinson pressure bar (SHPB) for gas coal in the Panxie Coal Field in Huainan City. In the test, the influence laws of various loading patterns on mechanical properties, failure characteristics, and energy dissipation of gas coal sample were analyzed. The results showed that the stress-strain curve of coal gas under dynamic load had no micropore compaction stage compared with that under static load. Dynamic compressive strength, dynamic strength growth factor, mixed dynamic elasticity modulus, and dissipation energy were all highly correlated with strain rate, whereas energy dissipation rate was uncorrelated with strain rate. In addition, the gas coal sample with lower strain had small dissipated energy, and it developed a splitting failure mode. With the increase of strain rate, the dissipation energy increased and the crushing degree of gas coal intensified, finally presenting a compressive failure mode. Based on the comparison of dissipated energy densities of different gas coal samples, given the same dissipated energy density, the failure degree of sample under dynamic load was higher than that under static load.
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Ahmadi, H. R., J. G. R. Kingston i A. H. Muhr. "Dynamic Properties of Filled Rubber — Part I: Simple Model, Experimental Data and Simulated Results". Rubber Chemistry and Technology 81, nr 1 (1.03.2008): 1–18. http://dx.doi.org/10.5254/1.3548196.
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Abstract A simple “viscoplastic” model is used to capture the stress-strain behavior of a filled SBR vulcanizate; a key objective is to predict dynamic properties, in particular the Fletcher-Gent or Payne effect, from non-cyclic stress-strain data. A simple fitting procedure is described to obtain the parameters of the viscoplastic model from the stress relaxation data and stress-strain loading curves at constant rate. Special attention is given to keeping the numbers of parameters and of characterization tests small. Elastic models are incapable of representing several aspects of the material behavior whereas it is confirmed that the proposed “viscoplastic” approach captures the essence of the behavior.
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Ito, Satoru, Arnab Majumdar, Hiroaki Kume, Kaoru Shimokata, Keiji Naruse, Kenneth R. Lutchen, Dimitrije Stamenović i Béla Suki. "Viscoelastic and dynamic nonlinear properties of airway smooth muscle tissue: roles of mechanical force and the cytoskeleton". American Journal of Physiology-Lung Cellular and Molecular Physiology 290, nr 6 (czerwiec 2006): L1227—L1237. http://dx.doi.org/10.1152/ajplung.00299.2005.
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The viscoelastic and dynamic nonlinear properties of guinea pig tracheal smooth muscle tissues were investigated by measuring the storage (G′) and loss (G") moduli using pseudorandom small-amplitude length oscillations between 0.12 and 3.5 Hz superimposed on static strains of either 10 or 20% of initial length. The G" and G′ spectra were interpreted using a linear viscoelastic model incorporating damping (G) and stiffness (H), respectively. Both G and H were elevated following an increase in strain from 10 to 20%. There was no change in harmonic distortion ( Kd), an index of dynamic nonlinearity, between 10 and 20% strains. Application of methacholine at 10% strain significantly increased G and H while it decreased Kd. Cytochalasin D, isoproterenol, and HA-1077, a Rho-kinase inhibitor, significantly decreased both G and H but increased Kd. Following cytochalasin D, G, H, and Kd were all elevated when mean strain increased from 10 to 20%. There were no changes in hysteresivity, G/H, under any condition. We conclude that not all aspects of the viscoelastic properties of tracheal smooth muscle strips are similar to those previously observed in cultured cells. We attribute these differences to the contribution of the extracellular matrix. Additionally, using a network model, we show that the dynamic nonlinear behavior, which has not been observed in cell culture, is associated with the state of the contractile stress and may derive from active polymerization within the cytoskeleton.
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Guo, Y. B., V. P. W. Shim i B. W. F. Tan. "Dynamic Tensile Properties of Magnesium Nanocomposite". Materials Science Forum 706-709 (styczeń 2012): 780–85. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.780.
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In this study, a Mg-6wt%Al alloy and its composite containing 0.22vol% Al2O3 nanoparticles are fabricated using a disintegrated melt deposition technique, and samples are subjected to quasi-static and dynamic tension. Compared to quasi-static loading, both materials exhibit significantly higher yield stresses and tensile strengths, much better ductility, and thus a higher energy absorption capacity under dynamic tension. In terms of nanoparticle addition, its influence on the mechanical properties are not notable; enhancement of the elastic modulus, yield stress and tensile strength are negligible, and there is a small reduction in ductility. The tensile behaviour obtained in this investigation was compared with results of previous compression tests, and significant tension-compression asymmetry in the response is observed. The tensile yield stress is noticeably larger than that in compression, and the profile of the stress-strain curve for tension differs from that for compression – it is convex upwards for tension, but concave upwards for compression. A possible reason for this asymmetry is the occurrence of twinning in compression and its absence in tension.
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Roland, C. M., i G. F. Lee. "Interaggregate Interaction in Filled Rubber". Rubber Chemistry and Technology 63, nr 4 (1.09.1990): 554–66. http://dx.doi.org/10.5254/1.3538273.
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Abstract Measurements of the dynamic properties of carbon-black-filled rubber can be carried out on most instrumentation at strains within the limits of linear behavior; thus, assessments of acoustic performance can readily be made. The equivalence of small-strain dynamic-mechanical testing and acoustic measurements has been demonstrated herein. Blends of NR with a high concentration of 1,2-BR are attractive candidates for damping applications because of the extended frequency range of the glass to rubber transition. One approach to improving the magnitude of the damping is to incorporate high levels of carbon black into the material. Significant interaggregate interaction, promoted for example by a low degree of carbon-black dispersion, will amplify the energy dissipation. The strain dependence of the dynamic properties implicit in such an approach can result in a damping performance sensitive to deformation. The loss tangent rises significantly after such a deformation, while the loss modulus experiences a barely measurable decline. This sensitivity to deformation will thus impact more on constrained layer damping applications than on simple extensional damping. For the materials tested in the present study, complete recovery of the damage to the carbon-black network (which engenders the changes in dynamic mechanical properties) required more than a day at room temperature.
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Jacques, Eric, Alan Lloyd, Abass Braimah, Murat Saatcioglu, Ghasan Doudak i Omar Abdelalim. "Influence of high strain-rates on the dynamic flexural material properties of spruce–pine–fir wood studs". Canadian Journal of Civil Engineering 41, nr 1 (styczeń 2014): 56–64. http://dx.doi.org/10.1139/cjce-2013-0141.
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The influence of high strain-rate loading on the flexural response of typical light-frame wood construction has been investigated. A total of 30 stud grade 38 mm × 140 mm × 2440 mm (2″ × 6″ × 8′) spruce–pine–fir (S–P–F) lumber specimens were tested within a range of low and high strain-rates between 6 × 10−6 s−1 and 0.4 s−1. A single-degree-of-freedom iterative solution procedure was used to compute the high strain-rate modulus of rupture (MOR) and modulus of elasticity (MOE). The MOR was statistically enhanced by high strain-rates, while the MOE and strain at rupture were not. Since equilibrium of the dynamic stress–strain relationship requires that one or both of the MOE and strain at rupture must be sensitive to strain-rate effects, the lack of observed rate enhancement on these material properties was attributed to large scatter within a small sample set. Based on the results, material dynamic increase factors and a stress–strain relationship suitable for blast resistant design of timber structures were also proposed.
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Mouali, Lila, Guillaume Veylon, Daniel Dias, Laurent Peyras, Claudio Carvajal, Jérôme Duriez i Eric Antoinet. "Dynamic Properties of a Compacted Residual Soil from the West Indies". Geotechnics 3, nr 2 (28.04.2023): 254–77. http://dx.doi.org/10.3390/geotechnics3020015.
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This paper presents a laboratory investigation of the strain-dependent cyclic properties of a compacted tropical residual soil as measured in a resonant column and cyclic triaxial testing program. The mechanical properties were evaluated with respect to cyclic shear strain amplitude, initial void ratio, and confining pressure. It was shown that the existing models for the prediction of shear modulus reduction and damping ratio curves were not pertinent in the case of the compacted residual soil studied. Empirical equations were developed for the small-strain shear modulus and the normalized shear modulus, damping ratio, and pore water pressure ratio curves for void ratios between e = 1.00 and e = 1.50 and mean effective pressures of p′ = 50−300 kPa. The comparison of the models to the measured values suggest that the uncertainties associated with each of these models are lower than 20% of the predicted values. The results were established as part of a project for the construction of an embankment dam in the West Indies. However, the methodology as well as the model formulation framework presented in the article can be generalized to other residual soils and applied in all fields of geotechnical engineering.
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Mohammadi, Farough, i Ramin Sedaghati. "Dynamic mechanical properties of an electrorheological fluid under large-amplitude oscillatory shear strain". Journal of Intelligent Material Systems and Structures 23, nr 10 (6.05.2012): 1093–105. http://dx.doi.org/10.1177/1045389x12442013.
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In the present study, the shear stress response and the dynamic mechanical properties of an electrorheological fluid are experimentally investigated for small/large shear strain amplitude at moderate range of frequencies and different field intensities. A new efficient constitutive model has also been proposed, which can accurately predict the measured experimental data. Compared with the Fourier transformation rheology, the proposed model requires less number of parameters in order to predict the stress response and the mechanical properties, including storage and loss moduli for different strain amplitudes, frequencies, and field intensities. This leads to simplify the parameter identification in order to predict the material response using the optimization methods.
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Li, Haiwen, Sathwik S. Kasyap i Kostas Senetakis. "Multi-Scale Study of the Small-Strain Damping Ratio of Fiber-Sand Composites". Polymers 13, nr 15 (27.07.2021): 2476. http://dx.doi.org/10.3390/polym13152476.
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The use of polypropylene fibers as a geosynthetic in infrastructures is a promising ground treatment method with applications in the enhancement of the bearing capacity of foundations, slope rehabilitation, strengthening of backfills, as well as the improvement of the seismic behavior of geo-systems. Despite the large number of studies published in the literature investigating the properties of fiber-reinforced soils, less attention has been given in the evaluation of the dynamic properties of these composites, especially in examining damping characteristics and the influence of fiber inclusion and content. In the present study, the effect of polypropylene fiber inclusion on the small-strain damping ratio of sands with different gradations and various particle shapes was investigated through resonant column (macroscopic) experiments. The macroscopic test results suggested that the damping ratio of the mixtures tended to increase with increasing fiber content. Accordingly, a new expression was proposed which considers the influence of fiber content in the estimation of the small-strain damping of polypropylene fiber-sand mixtures and it can be complementary of damping modeling from small-to-medium strains based on previously developed expressions in the regime of medium strains. Additional insights were attempted to be obtained on the energy dissipation and contribution of fibers of these composite materials by performing grain-scale tests which further supported the macroscopic experimental test results. It was also attempted to interpret, based on the grain-scale tests results, the influence of fiber inclusion in a wide spectrum of properties for fiber-reinforced sands providing some general inferences on the contribution of polypropylene fibers on the constitutive behavior of granular materials.
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Huang, Zeyang, Zhengxiang Huang i Xudong Zu. "Study on dynamic mechanical properties of tungsten copper alloy and application of shaped charge". Journal of Physics: Conference Series 2541, nr 1 (1.07.2023): 012042. http://dx.doi.org/10.1088/1742-6596/2541/1/012042.
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Abstract The tungsten-copper alloy liner has better performance than the copper liner. In order to better study the jet forming and penetration characteristics and dynamic mechanical properties of tungsten-copper alloy-shaped charge liner, this paper uses a multi-functional mechanical experimental machine and a Hopkinson bar device to carry out quasi-static tensile and dynamic impact tests, respectively, and fit the Johnson-Cook constitutive equation. The obtained parameters are used to carry out numerical simulations and compared with the experiment. The results show that the stress of the dynamic impact curve is higher than that of the quasi-static stress, and the strain rate strengthening effect is more obvious. There is an adiabatic temperature rise at the strain rate and an obvious thermal softening effect at different strain rates. At the highest strain rate, it shows an obvious strain rate strengthening effect and obvious plasticizing effect, and the tungsten-copper alloy has a certain sensitivity to strain rate. The precision of the Johnson-Cook constitutive model is higher, and it can better describe the plastic flow stress of tungsten-copper alloy at a high strain rate. When the parameters of the fitted Johnson-Cook model are used in the numerical simulation, the error between the numerical simulation and the actual is small. The obtained Johnson-Cook model and dynamic mechanical properties can help the follow-up study on the influencing factors of tungsten-copper jet forming and fracture, including the effect of material strength on injection instability, the integration of the shear band model with hydrodynamics, and the comparison of injection molding penetration with copper liners provide relevant data.
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Gong, Fengqiang, Hao Ye i Yong Luo. "The Effect of High Loading Rate on the Behaviour and Mechanical Properties of Coal-Rock Combined Body". Shock and Vibration 2018 (25.06.2018): 1–9. http://dx.doi.org/10.1155/2018/4374530.
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In order to investigate the high loading rate effect on the behaviour and mechanical properties of coal-rock combined body, the dynamic compressive tests were conducted by using the Split-Hopkinson Pressure Bar (SHPB) device under the loading rate range from 2.7×105 MPa/s to 4.0×105 MPa/s. The stress-strain curves, dynamic peak stress and strain, elastic modulus, and energy distribution law of coal-rock combined body under different loading rates were analyzed and discussed. The results show that the dynamic stress-strain curves of coal-rock combined body have a double-peak feature under high loading rate range, which can be divided into the initial bearing stage, the bearing decline stage, the bearing enhance stage, and the unstable stage. The first peak stress of the coal-rock combined body is independent of the loading rate, while the dynamic compressive strength (the second peak stress) and dynamic peak strain (the second peak strain) have a strong loading rate effect and will generally increase linearly with the loading rate. The first and second elastic moduli of coal-rock combined body are not sensitive to the loading rate. With the increase of the loading rate, the incident energy and reflective energy of coal-rock combined body increase rapidly, while the change of transmitted energy is very small. The absorption energy ratio of the coal-rock combined body shows a good linear law with the incident energy under different loading rates.
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Wang, Wei, Zhonghao Zhang, Qing Huo, Xiaodong Song, Jianchao Yang, Xiaofeng Wang, Jianhui Wang i Xing Wang. "Dynamic Compressive Mechanical Properties of UR50 Ultra-Early-Strength Cement-Based Concrete Material under High Strain Rate on SHPB Test". Materials 15, nr 17 (5.09.2022): 6154. http://dx.doi.org/10.3390/ma15176154.
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UR50 ultra-early-strength cement-based self-compacting high-strength material is a special cement-based material. Compared with traditional high-strength concrete, its ultra-high strength, ultra-high toughness, ultra-impact resistance, and ultra-high durability have received great attention in the field of protection engineering, but the dynamic mechanical properties of impact compression at high strain rates are not well known, and the dynamic compressive properties of materials are the basis for related numerical simulation studies. In order to study its dynamic compressive mechanical properties, three sets of specimens with a size of Φ100 × 50 mm were designed and produced, and a large-diameter split Hopkinson pressure bar (SHPB) with a diameter of 100 mm was used to carry out impact tests at different speeds. The specimens were mainly brittle failures. With the increase in impact speed, the failure mode of the specimens gradually transits from larger fragments to small fragments and a large amount of powder. The experimental results show that the ultra-early-strength cement-based material has a greater impact compression brittleness, and overall rupture occurs at low strain rates. Its dynamic compressive strength increases with the increase of strain rates and has an obvious strain rate strengthening effect. According to the test results, the relationship curve between the dynamic enhancement factor and the strain rate is fitted. As the impact speed increases, the peak stress rises, the energy absorption density increases, and its growth rate accelerates. Afterward, based on the stress–strain curve, the damage variables under different strain rates were fitted, and the results show that the increase of strain rate has a hindering effect on the increase of damage variables and the increase rate.
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Zhao, Zhong, Mao-Xian Biao, Ming Li i Lian-Ying Zhang. "Effect of strain rate and high temperature on the tensile mechanical properties of coal sandstone". Thermal Science 23, Suppl. 3 (2019): 927–33. http://dx.doi.org/10.2298/tsci180811179z.
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The Split-Hopkinson pressure bar test system with the MTS652.02 high temperature furnace and the 50 mm diameter are used to investigate the dynamic tensile mechanical properties of coal sandstone for the first time. Brazilian tests at high loading rates are conducted at ambient temperature and after heat treatment at 800?C. The effect of the strain rate on the tensile mechanical properties is analyzed using the SEM. The results show that after heat treatment at 800?C, the dynamic indirect tensile strength of sandstone increases with the increase of strain rate. Due to the effect of thermal melting and evaporation, after treatment at 800?C, the edges of the internal cracks in the sandstone become rough and lead to more defects. This makes the dynamic indirect tensile strength of the samples at room temperature greater than that at high temperature under the same strain rate. After heat treatment at 800?C, as the strain rate increases, the damage morphology of sandstone changes from large arc-shaped unilateral tensile faces to small granular detrital fragments; the extent of damage gradually increases at the same time.
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Gabryś, Katarzyna, Raimondas Šadzevičius, Midona Dapkienė, Dainius Ramukevičius i Wojciech Sas. "Effect of a Fine Fraction on Dynamic Properties of Recycled Concrete Aggregate as a Special Anthropogenic Soil". Materials 16, nr 14 (13.07.2023): 4986. http://dx.doi.org/10.3390/ma16144986.
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The literature confirms that fine recycled concrete aggregate (fRCA) can be used as a replacement for natural soil in new concrete, offering many advantages. Despite these advantages, there are also critical barriers to the development of fRCA in new mixes. Among these, the first challenge is the variability of fRCA properties, in both physical, chemical, and mechanical terms. Many individual studies have been carried out on different RCA or fRCA properties, but little investigative work has been performed to analyze their dynamic properties. Therefore, the influence of the non-cohesive fine fraction content of RCA on the dynamic properties of this waste material, when used as a specific anthropogenic soil, has been studied in laboratory conditions, employing a standard resonant column apparatus, as well as piezoelectric elements. In the present research, special emphasis has been placed on the dynamic shear modulus, dynamic damping ratio, small-strain shear modulus, and small-strain damping ratio, as well as shear modulus degradation G(γ)/Gmax, the damping ratio increase D(γ)/Dmin, and the threshold shear strain amplitudes γtl and γtv. Artificially prepared fRCAs with varying fine fraction contents (0% ≤ FF ≤ 30%, within increments of 5%) have been tested at different pressures (p′ = 90, 180, and 270 kPa) and relative densities of Dr > 65%. This study also examined the effect of two tamping-based sample preparation methods, i.e., dry and wet tamping. The results presented herein indicate that the analyzed anthropogenic material, although derived from concrete and produced by human activities, behaves very similarly to natural aggregate when subjected to dynamic loading. The introduction of a fine fraction content to fRCA leads to changes in the dynamic properties of the tested mixture. Concrete material with lower stiffness but, at the same time, with stronger damping properties can be obtained. A fine fraction content of at least 30% is sufficient to cause a significant loss of stiffness and, at the same time, a significant increase in the damping properties of the mixture. This study can serve as a reference for designing fRCA mixtures in engineering applications.
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Morozova, Anna, Yana Olkhovikova, Evgeniy Tkachev, Andrey Belyakov i Rustam Kaibyshev. "Effect of Deformation Temperature on Microstructure and Mechanical Properties of Low-Alloyed Copper Alloy". Materials Science Forum 941 (grudzień 2018): 982–87. http://dx.doi.org/10.4028/www.scientific.net/msf.941.982.
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The microstructure evolution and mechanical properties of a copper alloy subjected to deformation at temperatures of 20 °C and 400 °C to total strains from 1 to 4 were examined. The formation of planar low-angle boundaries with moderate misorientations occurs within initial grains at relatively small strains regardless of deformation temperature. Upon further processing the misorientations of these boundaries progressively increase and the new ultrafine grains develop. Continuous dynamic recrystallization takes place during deformation at ambient and elevated temperatures. The kinetics of dynamic recrystallization is discussed in terms of a modified Johnson-Mehl-Avrami-Kolmogorov relationship. The large plastic straining results in significant strengthening, the ultimate tensile strength increases from 190 MPa in the initial state to 440 MPa and to 400 MPa after total strain of 4 at 20 °C and 400 °C, respectively. A modified Hall-Petch relationship is applied to evaluate the contribution of grain refinement and dislocation density to the overall strengthening.
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Lei, Jingfa, Yan Xuan, Tao Liu, Feiya Duan, Zhan Wei i Chen Lu. "Static and Dynamic Tensile Mechanical Behavior of Polyvinyl Chloride Elastomers with Different Shore Hardness". Shock and Vibration 2021 (8.03.2021): 1–10. http://dx.doi.org/10.1155/2021/8887242.
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An experiment on the static and dynamic tensile mechanical properties of polyvinyl chloride (PVC) elastomers is conducted using an Instron-5943 universal testing machine and an improved Split Hopkinson Tensile Bar to study the dynamic tensile mechanical properties of PVC elastomer materials. The stress-strain curves of PVC materials with three types of Shore hardness (57A, 52A, and 47A) under the strain rates of 0.1 s−1 and 400 ∼ 1800 s−1 are obtained. Results show that the mechanical behavior of PVC elastomer materials with different Shore hardness has remarkable linear elastic characteristics under the action of quasistatic tensile load. It has substantial sensitivity to strain rate and viscoelastic mechanical characteristics under the action of dynamic tensile load. The Zhu–Wang–Tang nonlinear viscoelastic constitutive model is used to characterize the viscoelastic mechanical characteristics with small error. This paper can provide theoretical model and method support for the design, development, production, and reliability analysis of PVC elastomers and other soft polymer materials.
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Morsy, Amr M., Manal A. Salem i Hussein H. Elmamlouk. "Evaluation of dynamic properties of calcareous sands in Egypt at small and medium shear strain ranges". Soil Dynamics and Earthquake Engineering 116 (styczeń 2019): 692–708. http://dx.doi.org/10.1016/j.soildyn.2018.09.030.
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Müller, Manuel, Monika Scheufele, Janine Gückelhorn, Luis Flacke, Mathias Weiler, Hans Huebl, Stephan Gepraegs, Rudolf Gross i Matthias Althammer. "Reduced effective magnetization and damping by slowly relaxing impurities in strained γ-Fe2O3 thin films". Journal of Applied Physics 132, nr 23 (21.12.2022): 233905. http://dx.doi.org/10.1063/5.0128596.
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Magnetically ordered insulators are of key interest for spintronics applications, but most of them have not yet been explored in depth regarding their magnetic properties, in particular with respect to their dynamic response. We study the static and dynamic magnetic properties of epitaxially strained [Formula: see text]-Fe2O3 (maghemite) thin films grown via pulsed-laser deposition on MgO substrates by SQUID magnetometry and cryogenic broadband ferromagnetic resonance experiments. SQUID magnetometry measurements reveal hysteretic magnetization curves for magnetic fields applied both in- and out of the sample plane. From the magnetization dynamics of our thin films, we find a small negative effective magnetization in agreement with a strain induced perpendicular magnetic anisotropy. Moreover, we observe a non-linear evolution of the ferromagnetic resonance-linewidth as a function of the microwave frequency and explain this finding with the so-called slow relaxor model. We investigate the magnetization dynamics and non-linear damping mechanisms present in our samples as a function of frequency and temperature and in particular, observe a sign change in the effective magnetization from the transition of the magnetic anisotropy from a perpendicular easy axis to an easy in-plane anisotropy for reduced temperatures. Its nonlinear damping properties and strain-induced perpendicular anisotropy render [Formula: see text]-Fe2O3 an interesting material platform for spintronics devices.
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Wang, Y. H., i W. K. Siu. "Structure characteristics and mechanical properties of kaolinite soils. II. Effects of structure on mechanical properties". Canadian Geotechnical Journal 43, nr 6 (1.06.2006): 601–17. http://dx.doi.org/10.1139/t06-027.
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This paper reports the effects of structure on the mechanical responses of kaolinite with known and controlled fabric associations. The dynamic properties and strength were assessed by resonant column tests and undrained triaxial compression tests, respectively. The experimental results demonstrate that interparticle forces and associated fabric arrangements influence the volumetric change under isotropic compression. Soils with different structures have individual consolidation lines, and the merging trend is not readily seen under an isotropic confinement up to 250 kPa. The dynamic properties of kaolinite were found to be intimately related to the soil structure. Stronger interparticle forces or higher degrees of flocculated structure lead to a greater small-strain shear modulus, Gmax, and a lower associated damping ratio, Dmin. The soil structure has no apparent influence on the critical-state friction angle (ϕ′c = 27.5°), which suggests that the critical stress ratio does not depend on interparticle forces. The undrained shear strength of kaolinite is controlled by its initial packing density rather than by any interparticle attractive forces, and yet the influence of the structure on the effective stress path is obvious.Key words: interparticle forces, shear modulus, damping ratio, stressstrain behavior, undrained shear strength, critical state.
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Khrustalyov, Anton P., Gennady V. Garkushin, Ilya A. Zhukov, Sergey V. Razorenov i Alexander B. Vorozhtsov. "Quasi-Static and Plate Impact Loading of Cast Magnesium Alloy ML5 Reinforced with Aluminum Nitride Nanoparticles". Metals 9, nr 6 (25.06.2019): 715. http://dx.doi.org/10.3390/met9060715.
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The influence of a small addition of 0.5 wt.% aluminum nitride nanoparticles with an average size of 80 nm on the mechanical properties of a cast magnesium alloy under quasi-static tensile (strain rate 10−4 s−1) and plate impact loading (strain rate 105 s−1) was investigated. The composites were obtained by casting with a special mixing vortex device. After casting, some samples were subjected to heat treatment. The introduction of a small number of particles into the liquid metal led to a decrease in matrix grain size and a change in elasto-plastic and strength properties. Compared to quasi-static loading, the pre-heat treatment of tested alloys does not significantly affect the dynamic properties of a reinforced magnesium alloy under shock compression.
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Zhang, Z. X., Z. Y. Pan, Y. X. Wang, Z. J. Li i Q. Wei. "Simulations of the Nanomechanical Properties of Compressed Small Fullerenes". Modern Physics Letters B 17, nr 16 (10.07.2003): 877–84. http://dx.doi.org/10.1142/s021798490300586x.
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The nanomechanical properties of small fullerenes (C20, C36, C60 and C70) compressed between graphite planes are investigated based on molecular dynamics (MD) simulation using a combination of the many-body Brenner potential with a two-body potential. We find all the fullerenes exhibit similar elastic behavior even if the minimum radii of clusters in the direction of compression are reduced to 1/3 or 1/2 that of the free clusters. Both the potential energy of the system and restoring pressure on the graphite planes as functions of the axial strain are found to be reversible. This is a result of the reversible structure change. The fullerene is deformed severely into a disc-like structure due to compression. The deformation is almost saturated. In the process of decompression the free-fluerene structure is returned, and the cage rotated slightly between graphite sheets. To compare the elasticity of different fullerenes, the second order derivative of strain energy to strain is approximately calculated as a Young's modulus. The modulus becomes larger with increasing fullerene size.
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Wang, Jian, Mi-Jun Zhao, Jun-Zheng Zhang, Yan-Zhou Hao i Rui-Xia He. "Effect of Wetting and Drying Cycles on the Dynamic Properties of Compacted Loess". Advances in Civil Engineering 2022 (14.11.2022): 1–16. http://dx.doi.org/10.1155/2022/8748109.
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This paper investigates the dynamic properties of compacted loess under wetting and drying (W-D) cycles. A series of tests were conducted on compacted loess samples, namely, the soil dynamic triaxial test and the scanning electron microscopy (SEM) test. The test results showed that the dynamic stress-strain relationship of the compacted loess under the action of W-D cycles accords with the Hardin–Drnevich model. The initial dynamic shear modulus (G0) and the maximum dynamic shear stress (τy) of the compacted loess first decreased and then increased with the number of W-D cycles (n) increasing. The damping ratio (λ) increased linearly with the dynamic strain (εd) increasing in the semilogarithmic coordinate. The defined change rate of the damping ratio (η) first increased and then decreased with the n increasing. The macrostructure and microstructure characteristics of samples in the process of W-D cycles indicate that the increasing number of pores in the humidifying process and the cracks on the surface and inside of samples during dehumidification lead to the structural damage and dynamic properties reduction of compacted loess. The main reasons for structure strengthening and dynamic properties increasing are that soil particle structure develops to mosaic structure, pore structure develops to uniform small pore, and matrix suction makes soil sample tend to be dense.
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Rodríguez-Pérez, M. A., J. I. González-Peña, N. Witten i J. A. de Saja. "The Effect of Cell Size on the Physical Properties of Crosslinked Closed Cell Polyethylene Foams Produced by a High Pressure Nitrogen Solution Process". Cellular Polymers 21, nr 3 (maj 2002): 165–94. http://dx.doi.org/10.1177/026248930202100302.
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The thermal conductivity, thermal expansion, mechanical properties at low strain rates and dynamic mechanical properties of a collection of crosslinked closed cell polyethylene foams manufactured by a high pressure nitrogen solution process have been studied as a function of the cell size. The main mechanisms that influence each property and the foam microstructure have been considered to rationalise the results. A theoretical model has been used to examine the thermal conductivity values. The results have shown the extent to which reducing the cell size could improve the insulating capabilities of these materials. The effect of cell size on the mechanical properties at low strain rates is very small, as a consequence the thermal expansion does not depend on cell size. Nevertheless, the structural characteristics are seen to influence dynamic mechanical response at temperatures below 15°C.
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Porcino, Daniela, Vincenzo Marcianò i Raffaella Granata. "Static and dynamic properties of a lightly cemented silicate-grouted sand". Canadian Geotechnical Journal 49, nr 10 (październik 2012): 1117–33. http://dx.doi.org/10.1139/t2012-069.
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This paper describes the results of an experimental investigation on the behaviour of a lightly grouted loose medium sand under both monotonic and cyclic loading. The experimental programme in the present study was carried out on both untreated and treated sand specimens stabilized with a silica-based grout, and comprises isotropic triaxial compression tests equipped with bender elements, drained triaxial monotonic shearing tests, and undrained cyclic tests in a simple shear (SS) apparatus. The results highlight that the weak cementation level induced by chemical treatment was sufficient to moderately increase small-strain stiffness and stress–dilatancy of the grouted sand during drained monotonic shear. A small cohesion intercept was observed in the analyzed failure envelope, while cyclic liquefaction resistance exhibited a much more significant increase, with a different pattern of behaviour between low and high stress levels. Finally, undrained cyclic SS test results evidenced that silicate grout employed in this research improves undrained cyclic shear strength in a manner similar to densification of the same material up to a density index of approximately 75%.
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Jin, Wei, Yingchuan Zhang, Lanxin Jiang, Guangwu Yang, Jingsong Chen i Penghang Li. "A Dynamic Constitutive Model and Simulation of Braided CFRP under High-Speed Tensile Loading". Materials 15, nr 18 (14.09.2022): 6389. http://dx.doi.org/10.3390/ma15186389.
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In this study, a dynamic constitutive model for woven-carbon-fiber-reinforced plastics (CFRP) is formulated by combining dynamic tensile test data and fitting curves and incorporating variation rules established for the modulus of elasticity, strength, and fracture strain with respect to the strain rate. The dynamic constitutive model is then implemented with finite element software. The accuracy and applicability of the dynamic constitutive model are evaluated by comparing the numerically predicted load–displacement curves and strain distributions with the test data. The stress distribution, failure factor, modulus, and strength of the material under dynamic tension are also explored. The results show that the response simulated with the dynamic constitutive model is in good agreement with the experimental results. The strain is uniformly distributed during the elastic phase compared with the DIC strain field. Subsequently, it becomes nonuniform when stress exceeds 600 MPa. Then, the brittle fracture occurs. With the increase in the strain rate, the input modulus decreased, and the tensile strength increased. When the displacement was 0.13 mm, the simulation model was damaged at a low strain rate, and the stress value was 837.8 MPa. When it reached the high strain rate of 800 s−1, no failure occurred, and the maximum stress value was 432.5 MPa. For the same specimen, the strain rate was the smallest on both clamped ends, and the modulus and strength were large at the ends and small in the middle. The fitting curve derived from the test data was completely input into the dynamic constitutive model to better capture the dynamic change in the material properties.
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Wang, Qian, Jun Wang, Xiumei Zhong, Haiping Ma i Xiaowei Xu. "Dynamic Nonlinear and Residual Deformation Behaviors of the Fly Ash-Modified Loess". Shock and Vibration 2021 (6.12.2021): 1–11. http://dx.doi.org/10.1155/2021/1306986.
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Metastable loess soils can deform, inducing geological and engineering disasters. Therefore, the behavior of the loess under dynamic load is gaining massive attention from researchers to improve the strength of the soils. Fly ash mixed with loess can improve strength and reduce construction costs and environmental pollution. Moreover, it has strong economic and social benefits. This paper investigates the influence of fly ash on the dynamic properties of the modified loess through a series of dynamic triaxial tests of the fly ash modified loess with different fly ash contents. The treated soil samples were prepared using a static compaction method in both ends and cured for 28 days. The dynamic shear modulus ratio, the damping ratio, and the dynamic residual strain of the modified loess were analyzed. The variation characteristics of the dynamic shear modulus ratio and damping ratio with the dynamic shear strain of the fly ash modified loess were obtained. The effect of fly ash content on the dynamic nonlinear parameters of the modified loess was also investigated. In addition, the relationship between the dynamic residual strain and the fly ash content was discussed. The results show that the dynamic shear modulus ratio of fly ash modified loess decreases nonlinearly with the increase in the dynamic shear strain. However, the attenuation rate difference of the curves is small. The damping ratio increases gradually with increasing dynamic shear strain. Under a certain dynamic shear strain level, the damping ratio decreases with the increase in the fly ash content. The dynamic residual strain increases with the increase in the dynamic stress. However, it decreases with the increase in the fly ash content. When the fly ash content is between 10% and 20%, the dynamic residual strain of fly ash modified loess is reduced rapidly. However, when the fly ash content exceeds 20%, the dynamic residual strain decreases slowly. The fly ash content of 20% could be suggested as an optimal content for seismic resistance of the loess foundation.
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Zhang, Xinlei, Jun Guo, Yumin Chen, Yi Han, Ruibo Yi, Hongmei Gao, Lu Liu, Hanlong Liu i Zhifu Shen. "Mechanical Properties and Engineering Applications of Special Soils—Dynamic Shear Modulus and Damping of MICP-Treated Calcareous Sand at Low Strains". Applied Sciences 12, nr 23 (28.11.2022): 12175. http://dx.doi.org/10.3390/app122312175.
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Calcareous sand deposits are widespread along the shoreline in tropical and subtropical regions. Microbially induced calcite precipitation (MICP) treatment is a new method for improving the soil’s stiffness and strength. The small-strain shear modulus and damping ratio of MICP-treated calcareous sand, two critical parameters for predicting the dynamic behavior of soil, are little known. This study conducts a series of resonant column tests to investigate the dynamic characteristics of MICP-treated calcareous sand, emphasizing the influence of treatment duration and confining stress on the stiffness and damping characteristics. It analyzes the relationship between the initial dynamic shear modulus and unconfined compressive strength. In addition, empirical relationships between the reference shear strain and treatment duration or confining stress are provided. The results show that the normalized shear modulus G/G0 of MICP-cemented calcareous sand has a higher strain sensitivity than that of untreated sand, and the Hardin–Drnevich model can describe its attenuation pattern. The effective confining stress σc affects the degradation characteristics of the dynamic shear modulus of MICP-treated calcareous sand with a low cementation level; however, its impact decreases as the treatment duration increases. There is a linear relationship between the reference shear strain and confining stress. While the relationship between the reference shear stain and treatment duration is a power law.
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Zhang, Nan, Zhaoyu Wang, Yong Jin, Qi Li i Xiaohui Chen. "Experimental study on dynamic properties of sand-rubber mixtures in a small range of shearing strain amplitudes". Journal of Vibroengineering 19, nr 6 (30.09.2017): 4378–93. http://dx.doi.org/10.21595/jve.2017.18279.
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Hilger, Christopher, Reimund Stadler, L. Liane i de Lucca Freitas. "Multiphase thermoplastic elastomers by combination of covalent and association chain structures: 2. Small-strain dynamic mechanical properties". Polymer 31, nr 5 (maj 1990): 818–23. http://dx.doi.org/10.1016/0032-3861(90)90040-6.
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Camponovo, Christian, i Jürg Schweizer. "Rheological measurements of the viscoelastic properties of snow". Annals of Glaciology 32 (2001): 44–50. http://dx.doi.org/10.3189/172756401781819148.
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AbstractIn order to determine the viscoelastic properties of snow, torsional shear measurements were performed in a cold laboratory with a stress-controlled rheometer. Small samples (60 mm in diameter and about 7 mm thick of natural snow collected from the nearby study plot were loaded in simple shear with monotonically increasing stress (stress ramp) and with sinusoidally varying stress (oscillation). The dynamic measuring method allows the deformation process to be separated into a time-independent part (elastic) and a time-dependent part (viscous). The applied torque is sufficiently small to prevent destructive deformation, generally permitting the true viscoelastic properties of a sample to be obtained over a large range of frequency and temperature. The limit strain for linear viscoelastic deformation was found to be very small (0.5−5 × 10−4). Experiments performed beyond the linear range imply important textural changes (damage, breaking of bonds). The large strain reached during stress-ramp experiments showed that the ongoing damage process must be balanced by a healing (sintering) process. The usefulness of a rheometer was proven. It is a precise method for measuring with high reproducibility the rheological parameters of snow, and data gained with it improve our understanding of the deformation process under shear loading.
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Guzev, Mikhail, Evgenii Kozhevnikov, Mikhail Turbakov, Evgenii Riabokon i Vladimir Poplygin. "Experimental Studies of the Influence of Dynamic Loading on the Elastic Properties of Sandstone". Energies 13, nr 23 (25.11.2020): 6195. http://dx.doi.org/10.3390/en13236195.
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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.