scholarly journals Characterization of the microstructural components and corrosion-induced changes in the mechanical properties of oolitic limestone

2020 ◽  
Vol 205 ◽  
pp. 03011
Author(s):  
Aránzazu Piñán-Llamas ◽  
Fawad S. Niazi ◽  
Colton Amstutz ◽  
Zachary Brown
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Exposure Time ◽  
Chemical Weathering ◽  
Young's Modulus ◽  
Triaxial Compression ◽  
Effective Porosity ◽  
Peak Strength ◽  
Stress Concentrations ◽  
Oolitic Limestone

The understanding of the variation of mechanical properties and microstructural changes of rocks due to chemical weathering is critical for prospection, extraction and storage of energy resources in the subsurface. Uniaxial and triaxial compression tests were conducted on fresh and chemically weathered oolitic limestone samples submerged in acidic solutions with pH5 and pH3 values for 30 and 50 days each. Results show that both, acid concentration and exposure period have a significant influence not only in changes of effective porosity, Young’s modulus and peak strength, but also in the development of stress-induced microstructures. While the change in effective porosity increased and the Young’s modulus decreased with exposure time, the peak strength decreased with exposure time and decreasing pH. Micro-fracturing, twinning, and rigid body rotation were the main mechanisms of the deformations observed. The highest density of microcracks and twinned grains were observed in samples subjected to longer exposure periods of time, suggesting that the exposure time constitutes an essential factor in rock softening. Microfracturing initiated at grain boundaries, where stress concentrations were higher. In agreement with previous work on limestone inelastic compaction, the mechanical contrast of allochemical components with respect to cement conditioned the spatial distribution of the microfractures.

scholarly journals Effect of Radiation on Topopah Spring Tuff Mechanical Properties

1996 ◽  
Vol 465 ◽  
Author(s):  
P. A. Berge ◽  
S. C. Blair
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Peak Strength ◽  
Test Results ◽  
Welded Tuff ◽  
Discernible Effect ◽  
And Control ◽  
Compressive Tests ◽  
Topopah Spring Tuff

ABSTRACTThe effect of radiation on the mechanical properties of Topopah Spring tuff was investigated by performing uniaxial compressive tests on irradiated and control samples of the tuff from the potential repository horizon at Yucca Mountain. Test results are presented, including stress-strain curves and peak strength and Young's modulus values. The results from this preliminary study show that for uncracked samples of Topopah Spring tuff, exposure to gamma radiation had no discernible effect on the unconfined compressive (peak) strength or the Young's modulus. However, results for samples that contained partially healed subvertical cracks indicate that exposure to radiation may reduce the strength and Young's modulus significantly. This is attributed to weakening of the cementing materials in the cracks and fractures of the samples that were irradiated. These results are preliminary, and additional studies are warranted to evaluate whether radiation weakens cementing materials in welded tuff.

Mechanical properties of a hierarchical honeycomb with sandwich walls

2016 ◽  
Vol 230 (16) ◽  
pp. 2765-2775 ◽  
Author(s):  
Ting Yi
Keyword(s):  
Mechanical Properties ◽  
Finite Element Method ◽  
Fracture Toughness ◽  
Finite Element ◽  
Relative Density ◽  
Young’S Modulus ◽  
Elastic Limit ◽  
Young's Modulus ◽  
Peak Strength ◽  
Element Method

The in-plane compressive collapse and fracture toughness of a hierarchical hexagonal honeycomb with sandwich walls consisting of corrugated cores are studied by using finite element method. Its near-optimal configuration is identified by maximizing its elastic limit, which is determined by three competing failure modes including plastic yielding of the larger struts, or elastic wrinkling of the face sheets of the larger struts, or elastic buckling of the smaller struts. The overall mechanical properties of the optimal hierarchical honeycomb, including the Young’s modulus, elastic limit, peak strength, and fracture toughness are obtained from finite element method simulation and compared with analytical predictions, and the discrepancy between the two is explained. The optimal hierarchical honeycomb is found to be superior to its equivalent mass first-order honeycomb in all the mechanical properties listed above when the relative density is low (about 10%). Moreover, the Young’s modulus, elastic limit and peak strength under plastic failure mode, and the fracture toughness of this optimal hierarchical honeycomb are shown to depend linearly upon its relative density. This paper provides additional insights into hierarchical cellular materials.

Mechanical properties of FeAlSi powders prepared by mechanical alloying from different initial feedstock materials

2019 ◽  
Vol 107 (2) ◽  
pp. 207 ◽  
Author(s):  
Jaroslav Čech ◽  
Petr Haušild ◽  
Miroslav Karlík ◽  
Veronika Kadlecová ◽  
Jiří Čapek ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Alloying ◽  
Young’S Modulus ◽  
Milling Time ◽  
Young's Modulus ◽  
Element Model ◽  
X Ray Diffraction ◽  
X Ray ◽  
Powder Particles ◽  
Complete Homogenization

FeAl20Si20 (wt.%) powders prepared by mechanical alloying from different initial feedstock materials (Fe, Al, Si, FeAl27) were investigated in this study. Scanning electron microscopy, X-ray diffraction and nanoindentation techniques were used to analyze microstructure, phase composition and mechanical properties (hardness and Young’s modulus). Finite element model was developed to account for the decrease in measured values of mechanical properties of powder particles with increasing penetration depth caused by surrounding soft resin used for embedding powder particles. Progressive homogenization of the powders’ microstructure and an increase of hardness and Young’s modulus with milling time were observed and the time for complete homogenization was estimated.

scholarly journals First principles computation of composition dependent elastic constants of omega in titanium alloys: implications on mechanical behavior

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
R. Salloom ◽  
S. A. Mantri ◽  
R. Banerjee ◽  
S. G. Srinivasan
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
First Principles ◽  
Young's Modulus ◽  
Group Vi ◽  
Group V ◽  
Β Phase ◽  
Ti Alloys ◽  
Ω Phase ◽  
Stabilizer Concentration

AbstractFor decades the poor mechanical properties of Ti alloys were attributed to the intrinsic brittleness of the hexagonal ω-phase that has fewer than 5-independent slip systems. We contradict this conventional wisdom by coupling first-principles and cluster expansion calculations with experiments. We show that the elastic properties of the ω-phase can be systematically varied as a function of its composition to enhance both the ductility and strength of the Ti-alloy. Studies with five prototypical β-stabilizer solutes (Nb, Ta, V, Mo, and W) show that increasing β-stabilizer concentration destabilizes the ω-phase, in agreement with experiments. The Young’s modulus of ω-phase also decreased at larger concentration of β-stabilizers. Within the region of ω-phase stability, addition of Nb, Ta, and V (Group-V elements) decreased Young’s modulus more steeply compared to Mo and W (Group-VI elements) additions. The higher values of Young’s modulus of Ti–W and Ti–Mo binaries is related to the stronger stabilization of ω-phase due to the higher number of valence electrons. Density of states (DOS) calculations also revealed a stronger covalent bonding in the ω-phase compared to a metallic bonding in β-phase, and indicate that alloying is a promising route to enhance the ω-phase’s ductility. Overall, the mechanical properties of ω-phase predicted by our calculations agree well with the available experiments. Importantly, our study reveals that ω precipitates are not intrinsically embrittling and detrimental, and that we can create Ti-alloys with both good ductility and strength by tailoring ω precipitates' composition instead of completely eliminating them.

scholarly journals Tailoring a Low Young Modulus for a Beta Titanium Alloy by Combining Severe Plastic Deformation with Solution Treatment

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3467
Author(s):  
Anna Nocivin ◽  
Doina Raducanu ◽  
Bogdan Vasile ◽  
Corneliu Trisca-Rusu ◽  
Elisabeta Mirela Cojocaru ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Solution Treatment ◽  
Young Modulus ◽  
Orthopedic Implants ◽  
Beta Titanium Alloy

The present paper analyzed the microstructural characteristics and the mechanical properties of a Ti–Nb–Zr–Fe–O alloy of β-Ti type obtained by combining severe plastic deformation (SPD), for which the total reduction was of etot = 90%, with two variants of super-transus solution treatment (ST). The objective was to obtain a low Young’s modulus with sufficient high strength in purpose to use the alloy as a biomaterial for orthopedic implants. The microstructure analysis was conducted through X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) investigations. The analyzed mechanical properties reveal promising values for yield strength (YS) and ultimate tensile strength (UTS) of about 770 and 1100 MPa, respectively, with a low value of Young’s modulus of about 48–49 GPa. The conclusion is that satisfactory mechanical properties for this type of alloy can be obtained if considering a proper combination of SPD + ST parameters and a suitable content of β-stabilizing alloying elements, especially the Zr/Nb ratio.

scholarly journals Phase Formation, Microstructure and Mechanical Properties of Mg67Ag33 as Potential Biomaterial

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 461
Author(s):  
Konrad Kosiba ◽  
Konda Gokuldoss Prashanth ◽  
Sergio Scudino
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Equilibrium Phase ◽  
Antibacterial Properties ◽  
Equilibrium Phase Diagram ◽  
Compressive Yield Strength ◽  
X Ray ◽  
Fine Grained ◽  
Equilibrium Phases

The phase and microstructure formation as well as mechanical properties of the rapidly solidified Mg67Ag33 (at. %) alloy were investigated. Owing to kinetic constraints effective during rapid cooling, the formation of equilibrium phases is suppressed. Instead, the microstructure is mainly composed of oversaturated hexagonal closest packed Mg-based dendrites surrounded by a mixture of phases, as probed by X-ray diffraction, electron microscopy and energy dispersive X-ray spectroscopy. A possible non-equilibrium phase diagram is suggested. Mainly because of the fine-grained dendritic and interdendritic microstructure, the material shows appreciable mechanical properties, such as a compressive yield strength and Young’s modulus of 245 ± 5 MPa and 63 ± 2 GPa, respectively. Due to this low Young’s modulus, the Mg67Ag33 alloy has potential for usage as biomaterial and challenges ahead, such as biomechanical compatibility, biodegradability and antibacterial properties are outlined.

scholarly journals Effect of Nanopores on Mechanical Properties of the Shape Memory Alloy

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 529
Author(s):  
Chunzhi Du ◽  
Zhifan Li ◽  
Bingfei Liu
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Shape Memory ◽  
Young’S Modulus ◽  
Residual Strain ◽  
Surface Effect ◽  
Young's Modulus ◽  
Strain Curve ◽  
Stress Strain ◽  
Strength Limit

Nanoporous Shape Memory Alloys (SMA) are widely used in aerospace, military industry, medical and health and other fields. More and more attention has been paid to its mechanical properties. In particular, when the size of the pores is reduced to the nanometer level, the effect of the surface effect of the nanoporous material on the mechanical properties of the SMA will increase sharply, and the residual strain of the SMA material will change with the nanoporosity. In this work, the expression of Young’s modulus of nanopore SMA considering surface effects is first derived, which is a function of nanoporosity and nanopore size. Based on the obtained Young’s modulus, a constitutive model of nanoporous SMA considering residual strain is established. Then, the stress–strain curve of dense SMA based on the new constitutive model is drawn by numerical method. The results are in good agreement with the simulation results in the published literature. Finally, the stress-strain curves of SMA with different nanoporosities are drawn, and it is concluded that the Young’s modulus and strength limit decrease with the increase of nanoporosity.

Effect of Castor Oil Impregnation on the Physical and Mechanical Properties of Bacterial Cellulose

2012 ◽  
Vol 3 (1) ◽  
pp. 13-26
Author(s):  
Myrtha Karina ◽  
Lucia Indrarti ◽  
Rike Yudianti ◽  
Indriyati
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Bacterial Cellulose ◽  
Young’S Modulus ◽  
Castor Oil ◽  
Young's Modulus ◽  
Physical And Mechanical Properties ◽  
Scanning Electron Micrographs ◽  
Elongation At Break ◽  
Acetone Water

The effect of castor oil on the physical and mechanical properties of bacterial cellulose is described. Bacterial cellulose (BC) was impregnated with 0.5–2% (w/v) castor oil (CO) in acetone–water, providing BCCO films. Scanning electron micrographs revealed that the castor oil penetrated the pores of the bacterial cellulose, resulting in a smoother morphology and enhanced hydrophilicity. Castor oil caused a slight change in crystallinity indices and resulted in reduced tensile strength and Young's modulus but increased elongation at break. A significant reduction in tensile strength and Young's modulus was achieved in BCCO films with 2% castor oil, and there was an improvement in elongation at break and hydrophilicity. Impregnation with castor oil, a biodegradable and safe plasticiser, resulted in less rigid and more ductile composites.

Mechanical Properties of Pyrolytic "SiOCN" Thin Coatings

1993 ◽  
Vol 308 ◽  
Author(s):  
Sandrine Bec ◽  
André Tonck ◽  
Jean-Luc Loubet
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Ceramic Coatings ◽  
Optical Observation ◽  
Thin Coatings ◽  
Polymer Precursors ◽  
Polymeric State

ABSTRACTPyrolysis of polymer precursors (polysilazane) is a technologically and economically interesting way to produce thin ceramic coatings. However, many cracks appear and decohesion occurs during pyrolysis when the ceramic coatings (SiOCN) are thicker than 0.5 micrometers. In order to understand these cracking phenomena, the coatings are mechanically characterized by nanoindentation at different stages of the pyrolysis heat treatment.During pyrolysis, the cracking temperature is detected by in-situ optical observation. The thickness of the coatings varies during pyrolysis from 3 micrometers at the polymeric state to 1 micrometer at the ceramic state. The coatings' properties, hardness and Young's modulus are evaluated after heat treatment, taking into account the substrate's influence. A large variation of these properties occurs at the cracking temperature. Both the hardness and the Young's modulus are multiplied by a factor of 10. By analysing these results, we show that cracking is correlated with the evolution of the coatings' mechanical properties during the transformation.

scholarly journals Atomic Simulations of Packing Structures, Local Stress and Mechanical Properties for One Silicon Lattice with Single Vacancy on Heating

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3127
Author(s):  
Feng Dai ◽  
Dandan Zhao ◽  
Lin Zhang
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Silicon Crystal ◽  
Local Stress ◽  
Uniaxial Tensile ◽  
Single Vacancy ◽  
Vacancy Defects ◽  
Silicon Lattice ◽  
Atomic Simulations

The effect of vacancy defects on the structure and mechanical properties of semiconductor silicon materials is of great significance to the development of novel microelectronic materials and the processes of semiconductor sensors. In this paper, molecular dynamics is used to simulate the atomic packing structure, local stress evolution and mechanical properties of a perfect lattice and silicon crystal with a single vacancy defect on heating. In addition, their influences on the change in Young’s modulus are also analyzed. The atomic simulations show that in the lower temperature range, the existence of vacancy defects reduces the Young’s modulus of the silicon lattice. With the increase in temperature, the local stress distribution of the atoms in the lattice changes due to the migration of the vacancy. At high temperatures, the Young’s modulus of the silicon lattice changes in anisotropic patterns. For the lattice with the vacancy, when the temperature is higher than 1500 K, the number and degree of distortion in the lattice increase significantly, the obvious single vacancy and its adjacent atoms contracting inward structure disappears and the defects in the lattice present complex patterns. By applying uniaxial tensile force, it can be found that the temperature has a significant effect on the elasticity–plasticity behaviors of the Si lattice with the vacancy.

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