Numerical Study of Deformation and Fracture of Ceramics Nanocomposite with Different Structural Parameters under Mechanical Loading

2016 ◽  
Vol 683 ◽  
pp. 601-608
Author(s):  
Igor S. Konovalenko ◽  
Egor M. Vodopjyanov ◽  
Evgenii V. Shilko
Keyword(s):  
Mechanical Properties ◽  
Mechanical Response ◽  
Numerical Study ◽  
Structural Parameters ◽  
Phenomenological Approach ◽  
Sample Volume ◽  
Model Composite ◽  
Deformation And Fracture ◽  
Kinetics Of ◽  
Geometrical Dimensions

Deformation, fracture and effective mechanical properties of sintered ceramics composite under uniaxial compression were studied. To perform this investigation the plain numerical model of ceramics composites based on oxides of zirconium and aluminum with different structural parameters was developed. The model construction was carried out within the frame of particle based method, namely the movable cellular automaton method (MCA). The implementation of the phase transition in the MCA-model composite was carried out on the basis of the phenomenological approach, the main point of which was the formulation of the principle of irreversible mechanical behavior of the material. Increase the fracture toughness of ceramics after (T-M) transition in its structure was realized in the model by introducing transition kinetics of the automata pair from "bound" to an "unbound" state. The structure of model composite was generated on the basis of scanning electron microscope images of micro-sections of real composite. The influence of such structural parameters as geometrical dimensions of layers, inclusions, and their spatial distribution in the sample, volume content of the composite components and their mechanical properties, as well as the amount of zirconium dioxide undergone the phase transformation on the mechanical response were investigated

scholarly journals Evolution of Meniscal Biomechanical Properties with Growth: An Experimental and Numerical Study

2021 ◽  
Vol 8 (5) ◽  
pp. 70
Author(s):  
Marco Ferroni ◽  
Beatrice Belgio ◽  
Giuseppe M. Peretti ◽  
Alessia Di Giancamillo ◽  
Federica Boschetti
Keyword(s):  
Mechanical Properties ◽  
Stress Relaxation ◽  
Developmental Stage ◽  
Mechanical Response ◽  
Numerical Study ◽  
Numerical Models ◽  
Mechanical Stimulus ◽  
Specific Response ◽  
Mechanical Parameters ◽  
Biochemical Analyses

The menisci of the knee are complex fibro-cartilaginous tissues that play important roles in load bearing, shock absorption, joint lubrication, and stabilization. The objective of this study was to evaluate the interaction between the different meniscal tissue components (i.e., the solid matrix constituents and the fluid phase) and the mechanical response according to the developmental stage of the tissue. Menisci derived from partially and fully developed pigs were analyzed. We carried out biochemical analyses to quantify glycosaminoglycan (GAG) and DNA content according to the developmental stage. These values were related to tissue mechanical properties that were measured in vitro by performing compression and tension tests on meniscal specimens. Both compression and tension protocols consisted of multi-ramp stress–relaxation tests comprised of increasing strains followed by stress–relaxation to equilibrium. To better understand the mechanical response to different directions of mechanical stimulus and to relate it to the tissue structural composition and development, we performed numerical simulations that implemented different constitutive models (poro-elasticity, viscoelasticity, transversal isotropy, or combinations of the above) using the commercial software COMSOL Multiphysics. The numerical models also allowed us to determine several mechanical parameters that cannot be directly measured by experimental tests. The results of our investigation showed that the meniscus is a non-linear, anisotropic, non-homogeneous material: mechanical parameters increase with strain, depend on the direction of load, and vary among regions (anterior, central, and posterior). Preliminary numerical results showed the predominant role of the different tissue components depending on the mechanical stimulus. The outcomes of biochemical analyses related to mechanical properties confirmed the findings of the numerical models, suggesting a specific response of meniscal cells to the regional mechanical stimuli in the knee joint. During maturation, the increase in compressive moduli could be explained by cell differentiation from fibroblasts to metabolically active chondrocytes, as indicated by the found increase in GAG/DNA ratio. The changes of tensile mechanical response during development could be related to collagen II accumulation during growth. This study provides new information on the changes of tissue structural components during maturation and the relationship between tissue composition and mechanical response.

Geometrical nonlinear thermal response of sandwich panels with temperature dependent mechanical properties—Extended high-order approach

2019 ◽  
Vol 21 (5) ◽  
pp. 1700-1725 ◽  
Author(s):  
Yeoshua Frostig ◽  
George Kardomateas
Keyword(s):  
Mechanical Properties ◽  
Sandwich Panel ◽  
Mechanical Response ◽  
Numerical Study ◽  
Thermal Response ◽  
High Order ◽  
Theory Approach ◽  
Temperature Dependent ◽  
The Core ◽  
Compressive Loads

The thermal and the thermo-mechanical responses of a sandwich panel with a compliant core are investigated within the framework of the extended high-order approach where the core properties are temperature dependent or independent. Loads schemes include thermal field within temperature working range simultaneous with in-plane compressive loads applied to the core only and to the face sheets and core in the form of the uniform end—shortening of edge of panel. The mathematical formulations use the extended high-order sandwich panel theory approach that takes into account the in-plane rigidity of the core and uses the deformation patterns of the high-order sandwich panel theory. The linear and nonlinear field equations along with the appropriate boundary conditions are presented. A numerical study is conducted, and it investigates the thermal response with temperature independent and temperature dependent mechanical properties of the core as well as the thermo-mechanical response due to in-plane compressive loads. The results include displacements, stress resultants, and stress at critical locations along the panel as well as equilibria curves. They reveal that, in general, the panel with temperature independent properties response remains almost linear while with temperature dependent ones it takes a general nonlinear response. The addition of an external mechanical load changes the response from a linear/nonlinear one that may be allowable stress controlled to a case where loss of stability occurs.

scholarly journals Experimental and Numerical Study on Mechanical Properties and Deformation Behavior of Beishan Granite considering Heterogeneity

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Z. H. Wang ◽  
Y. L. Tan ◽  
S. M. Li ◽  
T. Z. Wang ◽  
X. C. Wu
Keyword(s):  
Numerical Simulation ◽  
Mechanical Response ◽  
Numerical Study ◽  
Failure Process ◽  
Confining Pressure ◽  
Sample Volume ◽  
Mechanical Tests ◽  
Peak Strength ◽  
Research Subjects ◽  
Beishan Granite

Disposal of high-level radioactive waste (HLW) deep underground is one of the most challenging research subjects in rock engineering. In China, Beishan granite is usually chosen as host rock for the construction of the HLW repository. In this study, mechanical tests are conducted on Beishan granite and the stress-strain state during the complete failure process is analyzed by numerical simulation. The results show that the tensile strength and uniaxial compressive strength of Beishan granite are 8.66 and 162.9 MPa, respectively. Dilatancy appears when the stress reaches about 81% of the peak strength. Heterogeneity is introduced by Weibull distribution in numerical simulation. With the increase of homogenization degree, the degraded elements are more easily to concentrate locally. Based on experimental and numerical simulation results, it is noticeable that the sample volume is basically in the state of compaction before reaching the peak strength. The elements are more likely to show expansion, and the splitting failure dominates the destroy mode when the confining pressure is relatively low. With increasing confining pressure, more and more degraded elements are concentrated in the shear band, which develops from the surface to the interior of the sample during loading. Therefore, the granite shows ductile mechanical response characteristics when the confining pressure is relatively high. The results are instructive for the construction of the repository.

scholarly journals Effect of Poling on the Mechanical Properties of β-Poly(Vinylidene Fluoride)

2006 ◽  
Vol 514-516 ◽  
pp. 951-955 ◽  
Author(s):  
Carlos M. Costa ◽  
Vitor Sencadas ◽  
João F. Mano ◽  
Senentxu Lanceros-Méndez
Keyword(s):  
Mechanical Properties ◽  
Mechanical Response ◽  
Vinylidene Fluoride ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
Direction Parallel ◽  
Poly Vinylidene Fluoride ◽  
The Stability ◽  
Kinetics Of ◽  
The Degree Of Crystallinity

In this work, mechanical and thermal experimental techniques have been applied in order to relate the mechanical response with the microscopic variations of the material. Stress-strain results along the main directions of β-poly(vinylidene fluoride), β-PVDF, in poled and non-poled samples enables to investigate the influence of the poling process on the mechanical response of the material. Further, differential scanning calorimetry experiments allow the investigation of the effect of poling in the degree of crystallinity of the material as well as on the stability of the crystalline phase. Thermogravimetric analysis was used to investigate the kinetics of the thermal degradation of poled and non-poled β-PVDF samples. The differences observed between the two materials suggest that the poling affects the mechanical properties of the material especially in the direction parallel to the polymeric chains and originates changes at a molecular level that remain beyond the melting of the material.

scholarly journals Deformation micromechanisms of collagen fibrils under uniaxial tension

2009 ◽  
Vol 7 (46) ◽  
pp. 839-850 ◽  
Author(s):  
Yuye Tang ◽  
Roberto Ballarini ◽  
Markus J. Buehler ◽  
Steven J. Eppell
Keyword(s):  
Mechanical Properties ◽  
Uniaxial Tension ◽  
Structural Engineering ◽  
Mechanical Response ◽  
Structural Parameters ◽  
Finite Size ◽  
Collagen Fibrils ◽  
Deformation Mechanisms ◽  
Collagen Molecule ◽  
Intermediate Structure

Collagen, an essential building block of connective tissues, possesses useful mechanical properties due to its hierarchical structure. However, little is known about the mechanical properties of collagen fibril, an intermediate structure between the collagen molecule and connective tissue. Here, we report the results of systematic molecular dynamics simulations to probe the mechanical response of initially unflawed finite size collagen fibrils subjected to uniaxial tension. The observed deformation mechanisms, associated with rupture and sliding of tropocollagen molecules, are strongly influenced by fibril length, width and cross-linking density. Fibrils containing more than approximately 10 molecules along their length and across their width behave as representative volume elements and exhibit brittle fracture. Shorter fibrils experience a more graceful ductile-like failure. An analytical model is constructed and the results of the molecular modelling are used to find curve-fitted expressions for yield stress, yield strain and fracture strain as functions of fibril structural parameters. Our results for the first time elucidate the size dependence of mechanical failure properties of collagen fibrils. The associated molecular deformation mechanisms allow the full power of traditional material and structural engineering theory to be applied to our understanding of the normal and pathological mechanical behaviours of collagenous tissues under load.

Elaboration and Characterization of the Properties of Refractory Cr Base Alloys

2010 ◽  
Vol 72 ◽  
pp. 46-52 ◽  
Author(s):  
Laurent Royer ◽  
Stéphane Mathieu ◽  
Christophe Liebaut ◽  
Pierre Steinmetz
Keyword(s):  
Mechanical Properties ◽  
Melting Point ◽  
Molten Glass ◽  
Energy Production ◽  
Creep Properties ◽  
Refractory Alloys ◽  
Industrial Use ◽  
Kinetics Of ◽  
Selection Of

For energy production and also for the glass industry, finding new refractory alloys which could permit to increase the process temperatures to 1200°C or more is a permanent challenge. Chromium base alloys can be good candidates, considering the melting point of Cr itself, and also its low corrosion rate in molten glass. Two families of alloys have been studied for this purpose, Cr-Mo-W and Cr-Ta-X alloys (X= Mo, Si..). A finer selection of compositions has been done, to optimize their chemical and mechanical properties. Kinetics of HT oxidation by air, of corrosion by molten glass and also creep properties of several alloys have been measured up to 1250°C. The results obtained with the best alloys (Cr-Ta base) give positive indications as regards the possibility of their industrial use.

Changes of Selected Structural and Mechanical Properties of the Strzelin Granites As Induced By Thermal Loads / Wpływ Obciążeń Termicznych Na Zmiany Niektórych Strukturalnych I Mechanicznych Właściwości Granitów Strzelińskich

2012 ◽  
Vol 57 (4) ◽  
pp. 951-974 ◽  
Author(s):  
Andrzej Nowakowski ◽  
Mariusz Młynarczuk
Keyword(s):  
Mechanical Properties ◽  
Nuclear Waste ◽  
Structural Changes ◽  
Structural Parameters ◽  
Total Porosity ◽  
Fracture Network ◽  
Qualitative Description ◽  
Temperature Changes ◽  
Heating And Cooling ◽  
Waste Repositories

Abstract Temperature is one of the basic factors influencing physical and structural properties of rocks. A quantitative and qualitative description of this influence becomes essential in underground construction and, in particular, in the construction of various underground storage facilities, including nuclear waste repositories. The present paper discusses the effects of temperature changes on selected mechanical and structural parameters of the Strzelin granites. Its authors focused on analyzing the changes of granite properties that accompany rapid temperature changes, for temperatures lower than 573ºC, which is the value at which the β - α phase transition in quartz occurs. Some of the criteria for selecting the temperature range were the results of measurements carried out at nuclear waste repositories. It was demonstrated that, as a result of the adopted procedure of heating and cooling of samples, the examined rock starts to reveal measurable structural changes, which, in turn, induces vital changes of its selected mechanical properties. In particular, it was shown that one of the quantities describing the structure of the rock - namely, the fracture network - grew significantly. As a consequence, vital changes could be observed in the following physical quantities characterizing the rock: primary wave velocity (vp), permeability coefficient (k), total porosity (n) and fracture porosity (η), limit of compressive strength (Rσ1) and the accompanying deformation (Rε1), Young’s modulus (E), and Poisson’s ratio (ν).

On the use of Ozawa/Flynn/Wall method to determine aging activation energy for elastomers

2021 ◽  
pp. 009524432110203
Author(s):  
Sudhir Bafna
Keyword(s):  
Mechanical Properties ◽  
Activation Energy ◽  
Weight Loss ◽  
Oxygen Consumption ◽  
Dwell Time ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Degradation Mechanism ◽  
Kinetics Of ◽  
Wall Method

It is often necessary to assess the effect of aging at room temperature over years/decades for hardware containing elastomeric components such as oring seals or shock isolators. In order to determine this effect, accelerated oven aging at elevated temperatures is pursued. When doing so, it is vital that the degradation mechanism still be representative of that prevalent at room temperature. This places an upper limit on the elevated oven temperature, which in turn, increases the dwell time in the oven. As a result, the oven dwell time can run into months, if not years, something that is not realistically feasible due to resource/schedule constraints in industry. Measuring activation energy (Ea) of elastomer aging by test methods such as tensile strength or elongation, compression set, modulus, oxygen consumption, etc. is expensive and time consuming. Use of kinetics of weight loss by ThermoGravimetric Analysis (TGA) using the Ozawa/Flynn/Wall method per ASTM E1641 is an attractive option (especially due to the availability of commercial instrumentation with software to make the required measurements and calculations) and is widely used. There is no fundamental scientific reason why the kinetics of weight loss at elevated temperatures should correlate to the kinetics of loss of mechanical properties over years/decades at room temperature. Ea obtained by high temperature weight loss is almost always significantly higher than that obtained by measurements of mechanical properties or oxygen consumption over extended periods at much lower temperatures. In this paper, data on five different elastomer types (butyl, nitrile, EPDM, polychloroprene and fluorocarbon) are presented to prove that point. Thus, use of Ea determined by weight loss by TGA tends to give unrealistically high values, which in turn, will lead to incorrectly high predictions of storage life at room temperature.

scholarly journals The Effect of Different Annealing Strategies on the Microstructure Development and Mechanical Response of Austempered Steels

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1041
Author(s):  
Eliseo Hernandez-Duran ◽  
Luca Corallo ◽  
Tanya Ros-Yanez ◽  
Felipe Castro-Cerda ◽  
Roumen H. Petrov
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Mechanical Response ◽  
Steel Grade ◽  
The Other ◽  
Microstructure Development ◽  
Microstructural Refinement ◽  
Heterogeneous Distribution ◽  
Parent Austenite ◽  
Conventional Annealing

This study focuses on the effect of non-conventional annealing strategies on the microstructure and related mechanical properties of austempered steels. Multistep thermo-cycling (TC) and ultrafast heating (UFH) annealing were carried out and compared with the outcome obtained from a conventionally annealed (CA) 0.3C-2Mn-1.5Si steel. After the annealing path, steel samples were fast cooled and isothermally treated at 400 °C employing the same parameters. It was found that TC and UFH strategies produce an equivalent level of microstructural refinement. Nevertheless, the obtained microstructure via TC has not led to an improvement in the mechanical properties in comparison with the CA steel. On the other hand, the steel grade produced via a combination of ultrafast heating annealing and austempering exhibits enhanced ductility without decreasing the strength level with respect to TC and CA, giving the best strength–ductility balance among the studied steels. The outstanding mechanical response exhibited by the UFH steel is related to the formation of heterogeneous distribution of ferrite, bainite and retained austenite in proportions 0.09–0.78–0.14. The microstructural formation after UFH is discussed in terms of chemical heterogeneities in the parent austenite.

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