scholarly journals Ribs of Pinna nobilis shell induce unexpected microstructural changes that provide unique mechanical properties

2021 ◽  
pp. 142163
Author(s):  
Kinga Nalepka ◽  
Katarzyna Berent ◽  
Antonio G. Checa ◽  
Tomasz Machniewicz ◽  
Adrian J. Harris ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Microstructural Changes ◽  
Pinna Nobilis

The effect of systematic diagenetic changes on the mechanical behavior of a quartz-cemented sandstone

Geophysics ◽  
2015 ◽  
Vol 80 (2) ◽  
pp. D145-D160 ◽  
Author(s):  
Jennie E. Cook ◽  
Laurel B. Goodwin ◽  
David F. Boutt ◽  
Harold J. Tobin
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Fluid Transport ◽  
Field Measurements ◽  
Elastic Stiffness ◽  
Contact Length ◽  
Ultrasonic Velocities ◽  
Microstructural Changes ◽  
Porosity And Permeability ◽  
Common Field

A key goal of petrophysical studies of sandstones is to relate common field measurements, particularly seismic or sonic velocities, to parameters defining the rock’s mechanical and hydrologic characteristics. These include elastic and inelastic mechanical properties, porosity, and permeability. We explored relationships among these properties in variably quartz-cemented, mature arenites of the St. Peter Sandstone with porosities ranging from 9% to 25%. In a previous paper, we described microstructural changes accompanying progressive quartz cementation and related porosity and permeability reduction in this sample suite. Here, we report ultrasonic velocities ultrasonic velocities, dynamic and static elastic properties, confined compressive strength, and tensile strength. Analyses of these data demonstrated that factors controlling permeability also fundamentally determined the elastic and inelastic mechanical properties. We found that the number of grain contacts, or bonds, per number of grains viewed in the thin section (bond-to-grain ratio [BGR]) was a key predictive parameter of the mechanical and hydrologic properties. Although the contact length and number of contacts correlated well with the mechanical behavior, statistical analyses showed that BGR was a better predictor of strength, elastic stiffness, and fluid transport properties than was the contact length. The BGR provided a measure of the pore throat occlusion that reduced permeability and the connectivity of the grain framework that stiffened and strengthened the rock. Because porosity and BGR were typically well correlated, porosity was a more quickly and easily measured proxy for BGR in this case. However, our analysis showed that it was the microstructural changes associated with porosity loss rather than porosity loss per se that largely controlled the properties of interest. Thus, consideration of BGR as well as the relative strengths of grains and bond type (cement, pressure solution) for different compositions of sandstone and cement may constructively form the basis for comparative studies of other more complex sandstones.

Microstructural Evolution of Compacted Graphite Iron under Thermo-Mechanical Fatigue Conditions

2011 ◽  
Vol 409 ◽  
pp. 757-762 ◽  
Author(s):  
S. Ghodrat ◽  
M. Janssen ◽  
Roumen H. Petrov ◽  
Leo Kestens ◽  
Jilt Sietsma
Keyword(s):  
Mechanical Properties ◽  
Cast Iron ◽  
Elevated Temperatures ◽  
Easy Access ◽  
Compacted Graphite Iron ◽  
Microstructural Changes ◽  
Oxide Layers ◽  
Cooling Cycle ◽  
Compacted Graphite ◽  
Mechanical Fatigue

Cast iron components in combustion engines, such as cylinder blocks and heads, are exposed for long periods of time to elevated temperatures and subjected to large numbers of heating and cooling cycles. In complex components, these cycles can lead to localized cracking due to stresses that develop as a result of thermal gradients and thermal mismatch. This phenomenon is known as Thermo-Mechanical Fatigue (TMF). Compacted Graphite Iron (CGI) provides a suitable combination of thermal and mechanical properties to satisfy the performance of engine components. However, TMF conditions cause microstructural changes, accompanied by the formation of oxides at and close to the surface, which together lead to a growth in size of the cast iron. These microstructural changes affect the mechanical properties and accordingly the thermo-mechanical fatigue properties. The aim of this research is to provide insight into the microstructure evolution of CGI, with its complex morphology, under TMF conditions. For this, optical and scanning electron microscopy observations are made after cyclic exposure to air at high temperature, both without and with mechanical loading. It was found that the oxide layers, which develop at elevated temperatures, crack during the cooling cycle of TMF. The cracking results from tensile stresses developing during the cooling cycle. Therefore, paths for easy access of oxygen into the material are formed. Fatigue cracks that develop also show oxidation at their flanks. In order to quantify the oxide layers surrounding the graphite particles, Energy Dispersive X-Ray Analysis (SEM-EDX) and Electron Probe Micro Analysis (EPMA) are used.

Correlation between the mechanical properties and microstructural changes of aged Al-5.8% Mg alloy

1991 ◽  
Vol 26 (23) ◽  
pp. 6331-6340 ◽  
Author(s):  
A. M. Hammad ◽  
M. A. Shaban ◽  
S. M. Sherif
Keyword(s):  
Mechanical Properties ◽  
Mg Alloy ◽  
Microstructural Changes
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