Construction of plastic contact deformation maps on ceramics: a case study on aluminum nitride

1996 ◽  
Vol 54 ◽  
pp. 636-637
Author(s):  
D. L. Callahan
Keyword(s):  
Plastic Deformation ◽  
Aluminum Nitride ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Bright Field Image ◽  
Perfectly Plastic ◽  
Contrast Analysis ◽  
Deformation Patterns

Modern polishing, precision machining and microindentation techniques allow the processing and mechanical characterization of ceramics at nanometric scales and within entirely plastic deformation regimes. The mechanical response of most ceramics to such highly constrained contact is not predictable from macroscopic properties and the microstructural deformation patterns have proven difficult to characterize by the application of any individual technique. In this study, TEM techniques of contrast analysis and CBED are combined with stereographic analysis to construct a three-dimensional microstructure deformation map of the surface of a perfectly plastic microindentation on macroscopically brittle aluminum nitride.The bright field image in Figure 1 shows a lg Vickers microindentation contained within a single AlN grain far from any boundaries. High densities of dislocations are evident, particularly near facet edges but are not individually resolvable. The prominent bend contours also indicate the severity of plastic deformation. Figure 2 is a selected area diffraction pattern covering the entire indentation area.

scholarly journals 3D Characterization of corneal deformation using ultrasound speckle tracking

2017 ◽  
Vol 10 (06) ◽  
pp. 1742005 ◽  
Author(s):  
Keyton Clayson ◽  
Elias Pavlatos ◽  
Yanhui Ma ◽  
Jun Liu
Keyword(s):  
Speckle Tracking ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Average Volume ◽  
Ocular Tissues ◽  
Corneal Deformation ◽  
Thin Spherical Shell ◽  
Iop Elevation ◽  
Dextran Solution

The three-dimensional (3D) mechanical response of the cornea to intraocular pressure (IOP) elevation has not been previously reported. In this study, we use an ultrasound speckle tracking technique to measure the 3D displacements and strains within the central 5.5[Formula: see text]mm of porcine corneas during the whole globe inflation. Inflation tests were performed on dextran-treated corneas (treated with a 10% dextran solution) and untreated corneas. The dextran-treated corneas showed an inflation response expected of a thin spherical shell, with through-thickness thinning and in-plane stretch, although the strain magnitudes exhibited a heterogeneous spatial distribution from the central to more peripheral cornea. The untreated eyes demonstrated a response consistent with swelling during experimentation, with through-thickness expansion overriding the inflation response. The average volume ratios obtained in both groups was near 1 confirming general incompressibility, but local regions of volume loss or expansion were observed. These results suggest that biomechanical measurements in 3D provide important new insight to understand the mechanical response of ocular tissues such as the cornea.

scholarly journals A Simulation Study for Trimetallic Nanosized Alloy (Ni, Cu, and Ag) in Hydrogenation of Organic Compounds: A Case Study of “Nitrophenols”

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Salem M. Bawaked ◽  
Islam Hamdy Abd El Maksod ◽  
Abdulmohsen Alshehri
Keyword(s):  
Catalytic Activity ◽  
Three Dimensional ◽  
High Accuracy ◽  
Metallic Surface ◽  
Active Centers ◽  
Bimetallic Systems ◽  
Complex Calculation ◽  
Bimetallic System

Trimetallic system (Ni, Cu, and Ag) supported on alumina was utilized for hydrogenation of nitrophenols. The catalytic active centers for hydrogenation were attributed only to the presence of Ni. However, the presence of bi- or trimetallic systems improves the catalytic activity via extra synergism. The catalytic activity was measured as the time for reaching 100% conversion. The function of synergism was fitted for both bimetallic systems (Ni:Ag; Ni:Cu) individually. Subsequently, three-dimensional function was fitted for trimetallic system (Ni:Cu:Ag) based on the linear combination of data for individual bimetallic system. After a complex calculation areal function was evaluated. An Excel program was written to simply evaluate the catalytic activity of trimetallic system with high accuracy. Characterization of catalysts was performed using EPR and pulsed chemisorption by hydrogen. These characterizations of samples enable us to evaluate particle size, metallic surface area, and degree of dispersion. These values were successfully correlated with the synergism function. The program written then could be capable of predicting these values for any trimetallic system.

Computational Characterization of Micro-To Macroscopic Deformation Behavior of Double Network Hydrogel

2012 ◽  
Vol 525-526 ◽  
pp. 193-196 ◽  
Author(s):  
Isamu Riku ◽  
Koji Mimura
Keyword(s):  
Mechanical Response ◽  
Three Dimensional ◽  
Engineering Application ◽  
Spring Element ◽  
Stress Strain Relation ◽  
Proposed Model ◽  
Simple Tension ◽  
Macroscopic Deformation ◽  
Toughness Mechanism

To take advantage of the toughness mechanism of DN gels and explore the possibility for engineering application as the structural member, the information on the mechanical behaviour of DN gels under various loading conditions is indispensable. Therefore, in this paper, we at first constitute a model of DN gel by paralleling a slider element with a nonlinear rubber elasticity spring element based on the nonaffine molecular chain network model, where each element represents the first and the second network of DN gel respectively. The theoretical stress-strain relation of this model shows a strain softening and subsequent strain hardening response, which has been considered as an agent of the propagation of the necking during the simple tension of glassy polymer. Continuously, based on this model, we propose a constitutive equation for DN gel and a three-dimensional simple tension simulation is performed. The computational results show that the propagation of the necking together with the macroscopic mechanical response of DN gel can be reproduced by the proposed model very well.

scholarly journals Determining the elastic-plastic effective width of the free flange of a hull girder with the breaking of a wall

2021 ◽  
Vol 1 (7 (109)) ◽  
pp. 32-40
Author(s):  
Valerii Sokov ◽  
Leontii Korostylov
Keyword(s):  
Plastic Deformation ◽  
Cross Section ◽  
Plastic Material ◽  
Three Dimensional ◽  
Median Plane ◽  
Effective Width ◽  
Hull Girder ◽  
Elastic Plastic ◽  
Perfectly Plastic ◽  
Estimation Scheme

This paper reports the dependences that have been derived to determine the effective width of a free flange in a dangerous cross-section of the wide-flange hull girder with the breaking of the wall/edges/axis at elastic-plastic deformation depending on the applied load for a perfectly plastic material without strengthening. Currently, there are no systematic dependences to determine the effective width of the free flange of girders of this type, except for certain cases. The technique is suitable for use for both purely elastic and elastic-plastic deformation. To calculate the stressed-strained state (SSS), a finite-element method (FEM) was used to solve the three-dimensional problem from the elasticity and plasticity theory. It has been shown that the node is exposed to simple loading. The reported results were derived within the framework of the deformation theory of plasticity. The largest ratio of external load to the boundary of fluidity is 0.9. The estimation scheme takes into consideration the most unfavorable working conditions of the examined node when the safest data are acquired. The dependences were built for the theoretical coefficient of concentration in a dangerous cross-section, which is used in the proposed procedure to determine the moment of transition from the elastic stage of deformation to elastic-plastic. When determining the effective width, the complex work of the flange and its deplanation was taken into consideration by defining the SSS components in the median plane. The feasibility of the idea of designing the SSS components on the inclined plane of a free flange has been proven. In this case, there is practically a (quasi) flat stressed state, suitable for the application of classical methods to determine the effective width. The proposed technique simplifies the calculations of the strength of the examined girder.

scholarly journals THREE-DIMENSIONAL RECONSTRUCTION AND VISUALIZATION OF PLANT CELLS

2020 ◽  
Vol 5 ◽  
pp. 28
Author(s):  
Sharifa Zaman ◽  
B. Fatima
Keyword(s):  
Mechanical Properties ◽  
Image Processing ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Plant Cells ◽  
Quantitative Characterization ◽  
And Topology ◽  
Short Period ◽  
Dimensional Reconstruction

The mechanical properties (like sensory texture etc.) of plants/fruits directly depend on their microstructures. Therefore, it is very important to well understand the geometry and topology of cells in order to control the microstructure for better mechanical response. In this research, techniques of digital image processing and segmentation in conjunction with mathematical morphology models are used to visualize and analyze the 3D cells of potato. ImageJ and MATLAB are used throughout in this study. The labeled image stacks are essential for studying quantitative characterization of 3D cells, MATLAB is used to label each image stacks. By using MATLAB 12420 cells were segmented within a short period of time and labeled each cell uniquely.

Geometrical characterization of canted coil springs

2006 ◽  
Vol 220 (12) ◽  
pp. 1831-1841
Author(s):  
J M Soler ◽  
R H Rangel
Keyword(s):  
Computer Aided Design ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Helical Spring ◽  
Element Analysis ◽  
Geometrical Characterization ◽  
Three Dimensional Models ◽  
Curvature And Torsion ◽  
Aided Design

This article presents a geometrical description of canted coil springs as a particular type of space curve. The influence of the canted angle on the geometrical curvature and torsion is investigated in order to characterize the three-dimensional geometry of the springs. Geometrical descriptions of helical spring rings generated by joining together the two ends of a rectilinear-axis spring as well as several types of spring rings, obtained from rectilinear-axis canted coil springs, are proposed. To create such ring geometries, conservation of length of wire is assumed and approximate relations are derived in order to simplify computations. These geometrical descriptions are then applied to generate appropriate three-dimensional models. Such models can be further imported to computer-aided design and finite-element analysis programmes in order to estimate the mechanical response of such springs.

Grain Size Strengthening in Microcrystalline Copper: A Three-Dimensional Dislocation Dynamics Simulation

2009 ◽  
Vol 423 ◽  
pp. 25-32 ◽  
Author(s):  
Christophe de Sansal ◽  
Benoit Devincre ◽  
Ladislas P. Kubin
Keyword(s):  
Plastic Deformation ◽  
Mechanical Response ◽  
Initial Density ◽  
Three Dimensional ◽  
Dislocation Dynamics ◽  
Dynamics Simulation ◽  
Key Factors ◽  
Slip Mechanism ◽  
Dynamics Simulations ◽  
Dislocation Sources

This article reports on a study of the microstructure and mechanical response of copper polycrystals with grain sizes in the micrometer range. Three-dimensional dislocation dynamics simulations are used for the first time to investigate grain boundary strengthening and the Hall-Petch law. The methodology, which involves constructing a microcrystalline representative volume element with periodic boundary conditions, is briefly presented. Simulation results show that the initial density of dislocation sources and the cross-slip mechanism are two key factors controlling the heterogeneity of plastic deformation within the grains. At yield, the smaller the grains size, the more plastic deformation is heterogeneously distributed between grains and homogeneously distributed inside the grains. A size effect is reproduced and it is shown that the Hall-Petch exponent decreases from the very beginning of plastic flow and may reach a stable value at strains larger than the conventional proof stress.

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