Yield and shear of rough interlocked faults: analytical solution and experimental observations

2020 ◽  
Author(s):  
Amir Sagy ◽  
Vladimir Lyakhovsky ◽  
Yossef H. Hatzor
Keyword(s):  
Surface Roughness ◽  
Analytical Solution ◽  
Normal Stress ◽  
Laboratory Experiments ◽  
Three Dimensional ◽  
Elastic Half Space ◽  
Interface Roughness ◽  
Displacement Rate ◽  
Initial Surface ◽  
Surface Geometry

<p>Natural fault surfaces are interlocked, partly cohesive, and display multiscale geometric irregularities. Here we examine the nucleation of deformation and the evolution of shear in such interlocked surfaces using a closed-form analytical solution and a series of laboratory experiments.  The analytical model considers an interlocked interface with multiscale roughness between two linear elastic half-space blocks. The interface geometry is based on three-dimensional fault surfaces imaging. It is represented by a Fourier series and the plane strain solution for the elastic stress distribution is represented as a sum of the constant background stress generated by a uniform far-field loading and perturbations associated with the interface roughness. The model predicts the critical stress necessary for failure and the location of failure nucleation sites across the surface, as function of the initial surface geometry.</p><p>A similar configuration is adopted in laboratory experiments as carbonate blocks with rough interlocked surfaces generated by tensional fracturing are sheared in a servo-controlled direct shear apparatus. Resistance to shear and surface roughness evolution are measured under variable normal stresses, slip distances and slip rates.  We find that the evolution of surface morphology with shear is closely related to the loading configuration. Initially rough, interlocked, surfaces become rougher when normal stress and displacement rate are increased. Under a fixed, relatively low normal stress and fixed displacement rate however, the surfaces become smoother with increasing displacement distance.  </p><p>The shear of the interlocked slip surfaces is associated with volumetric deformation, wear and frictional slip, all of which are typically observed across natural fault zones. We suggest that their intensities and partitioning are strongly affected by the initial surface roughness characteristics, the background stress, and the rate and magnitude of shear displacement. </p>

Nanofinishing of Microslots on Surgical Stainless Steel by Abrasive Flow Finishing Process: Experimentation and Modeling

2018 ◽  
Vol 6 (2) ◽  
Author(s):  
Sachin Singh ◽  
Deepu Kumar ◽  
Mamilla Ravi Sankar ◽  
Kamlakar Rajurkar
Keyword(s):  
Surface Roughness ◽  
Stainless Steel ◽  
Critical Role ◽  
Viscoelastic Model ◽  
Three Dimensional ◽  
Drug Eluting Stent ◽  
Initial Surface ◽  
Technological Advancement ◽  
Drug Eluting ◽  
Abrasive Flow Finishing

Miniaturization of components is one of the major demands of the today's technological advancement. Microslots are one of the widely used microfeature found in various industries such as automobile, aerospace, fuel cells and medical. Surface roughness of the microslots plays critical role in high precision applications such as medical field (e.g., drug eluting stent and microfilters). In this paper, abrasive flow finishing (AFF) process is used for finishing of the microslots (width 450 μm) on surgical stainless steel workpiece that are fabricated by electrical discharge micromachining (EDμM). AFF medium is developed in-house and used for performing microslots finishing experiments. Developed medium not only helps in the removal of hard recast layer from the workpiece surfaces but also provides nano surface roughness. Parametric study of microslots finishing by AFF process is carried out with the help of central composite rotatable design (CCRD) method. The initial surface roughness on the microslots wall is in the range of 3.50 ± 0.10 μm. After AFF, the surface roughness is reduced to 192 nm with a 94.56% improvement in the surface roughness. To understand physics of the AFF process, three-dimensional (3D) finite element (FE) viscoelastic model of the AFF process is developed. Later, a surface roughness simulation model is also proposed to predict the final surface roughness after the AFF process. Simulated results are in good agreement with the experimental results.

scholarly journals Tactile perception of the roughness of 3D-printed textures

2018 ◽  
Vol 119 (3) ◽  
pp. 862-876 ◽  
Author(s):  
Chelsea Tymms ◽  
Denis Zorin ◽  
Esther P. Gardner
Keyword(s):  
Surface Roughness ◽  
High Resolution ◽  
3D Printing ◽  
Human Subjects ◽  
Three Dimensional ◽  
Weber Fraction ◽  
Parametric Modeling ◽  
Surface Geometry ◽  
Surface Parameters ◽  
Roughness Perception

Surface roughness is one of the most important qualities in haptic perception. Roughness is a major identifier for judgments of material composition, comfort, and friction and is tied closely to manual dexterity. Some attention has been given to the study of roughness perception in the past, but it has typically focused on noncontrollable natural materials or on a narrow range of artificial materials. The advent of high-resolution three-dimensional (3D) printing technology provides the ability to fabricate arbitrary 3D textures with precise surface geometry to be used in tactile studies. We used parametric modeling and 3D printing to manufacture a set of textured plates with defined element spacing, shape, and arrangement. Using active touch and two-alternative forced-choice protocols, we investigated the contributions of these surface parameters to roughness perception in human subjects. Results indicate that large spatial periods produce higher estimations of roughness (with Weber fraction = 0.19), small texture elements are perceived as rougher than large texture elements of the same wavelength, perceptual differences exist between textures with the same spacing but different arrangements, and roughness equivalencies exist between textures differing along different parameters. We posit that papillary ridges serve as tactile processing units, and neural ensembles encode the spatial profiles of the texture contact area to produce roughness estimates. The stimuli and the manufacturing process may be used in further studies of tactile roughness perception and in related neurophysiological applications. NEW & NOTEWORTHY Surface roughness is an integral quality of texture perception. We manufactured textures using high-resolution 3D printing, which allows precise specification of the surface spatial topography. In human psychophysical experiments we investigated the contributions of specific surface parameters to roughness perception. We found that textures with large spatial periods, small texture elements, and irregular, isotropic arrangements elicit the highest estimations of roughness. We propose that roughness correlates inversely with the total contacted surface area.

scholarly journals Effect of Steel Surface Roughness and Expanded Graphite Condition on Sliding Layer Formation

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2960
Author(s):  
Aleksandra Rewolińska ◽  
Karolina Perz ◽  
Grzegorz Kinal
Keyword(s):  
Surface Roughness ◽  
Steel Surface ◽  
Friction Pair ◽  
Expanded Graphite ◽  
Initial Surface ◽  
Layer Formation ◽  
Material Transfer ◽  
Surface Geometry ◽  
First Case ◽  
Ring Pin

The aim of the research was to evaluate the influence of the initial roughness of a steel pin cooperating with a graphite ring—dry and wet—on the mechanism of sliding layer formation. A ring–pin friction pair was used for the study, where the rings were made of expanded graphite, while the pins were made of acid-resistant steel. In the first case, the steel pin interacted with a dry graphite ring, and in the second case, the graphite rings were moist. To determine the effect of initial surface roughness, the pins were divided into three roughness groups. To determine changes in surface geometry due to material transfer, the Ra and Rz parameters were measured. This project investigated how the initial roughness value of the steel surface pin cooperating with expanded graphite influences the formation of the sliding layer. Increasing the initial roughness of the steel surface interacting with the graphite contributes to faster layer formation and reduced roughness. The state of the expanded graphite—dry and wet—influences the formation of the sliding layer of graphite—a wet graphite component causes a faster smoothing of the steel surface. The running time of the wear apparatus has an effect on the resulting layer. The highest roughness group is the most favorable from the viewpoint of sliding layer formation.

Time-harmonic dislocations in a multilayered transversely isotropic magneto-electro-elastic half-space

2019 ◽  
Vol 30 (13) ◽  
pp. 1932-1950 ◽  
Author(s):  
Ehsan Moshtagh ◽  
Morteza Eskandari-Ghadi ◽  
Ernian Pan
Keyword(s):  
Analytical Solution ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Transversely Isotropic ◽  
Effective Property ◽  
Elastic Half Space ◽  
Smart Devices ◽  
Elastic Fields ◽  
Cylindrical System ◽  
Time Harmonic

Modeling layered systems with dislocations is very challenging; yet, it is important since most smart structures are made of multilayers to make best use of the combined effective property. As such, during the manufactures, defects, such as dislocations, could be introduced in the multilayers. In this article, we analytically find, for the first time, the response of three-dimensional multilayered magneto-electro-elastic systems due to time-harmonic dislocations. The dislocations are the most general, containing the elastic dislocations and discontinuity of the electric potential and/or magnetic potential over a circular region in any layer in the medium. The fully coupled partial differential equations of motion and the Gauss law for the magneto-electro-elastic materials are solved in terms of cylindrical system of vector functions, and the dual variable and position method is further introduced to treat the multilayers. Numerical examples are carried out based on the derived analytical solution to demonstrate the effects of the time-harmonic dislocations on the induced magneto-electro-elastic fields. This analytical solution is important in both electrodynamics and elastodynamics, with possible applications in material sciences and physics. The numerical results are useful in design process of smart devices made of magneto-electro-elastic solids applicable to other engineering fields like renewable energy.

scholarly journals 3D DEM simulations of monotonic interface behaviour between cohesionless sand and rigid wall of different roughness

2020 ◽  
Author(s):  
A. Grabowski ◽  
M. Nitka ◽  
J. Tejchman
Keyword(s):  
Normal Stress ◽  
Three Dimensional ◽  
Rigid Wall ◽  
Interface Roughness ◽  
Wall Friction ◽  
Dem Simulations ◽  
New Perspective ◽  
Interface Behaviour ◽  
Good Agreement ◽  
Three Dimensional Simulations

Abstract The paper deals with three-dimensional simulations of a monotonic quasi-static interface behaviour between cohesionless sand and a rigid wall of different roughness during wall friction tests in a parallelly guided direct shear test under constant normal stress. Numerical modelling was carried out by the discrete element method (DEM) using spheres with contact moments to approximately capture a non-uniform particle shape. The varying wall surface topography was simulated by a regular mesh of triangular grooves (asperities) along the wall with a different height, distance and inclination. The calculations were carried out with different initial void ratios of sand and vertical normal stress. The focus was to quantify the effect of wall roughness on the evolution of mobilized wall friction and shear localization, also to specify the ratios between slip and rotation and between shear stress/force and couple stress/moment in the sand at the wall. DEM simulations were generally in good agreement with reported experimental results for similar interface roughness. The findings presented in this paper offer a new perspective on the understanding of the wall friction phenomenon in granular bodies.

Factors controlling shear rupture roughness: An insight from field and laboratory experiments

2020 ◽  
Author(s):  
Manaska Mukhopadhyay ◽  
Uddalak Biswas ◽  
Nibir Mandal ◽  
Santanu Misra
Keyword(s):  
Surface Roughness ◽  
Laboratory Experiments ◽  
Alternative Mechanism ◽  
Plastic Yielding ◽  
Surface Geometry ◽  
Slip Direction ◽  
Shear Surface ◽  
Fracture Orientation ◽  
Shear Rupture ◽  
Coulomb Failure

<p>Faults and fracture surfaces record the history of slip events through a range of structural features in tectonically active zones. Slickensides, among them, prove to be the most prominent evidences of such slip movements. These linear features give us crucial information about the mechanical processes associated with shear surface roughness formation. We conducted extensive field survey in the Singhbhum Shear Zone, Eastern India, and report shear fractures of varying surface roughness from deformed quartzites. Shear surfaces encountered in the field study varied from very smooth, devoid of any lineation to strongly rough with prominent slickenlines.</p><p>For better understanding of the varied surface roughness, we performed analogue laboratory experiments. The experimental results suggest that the fracture orientation and the mode of shear failure are potential factors that control the fracture roughness. We used cohesive sand-talc models for the analogue experiments with varying sand:talc volume ratio, ranging from pure sand to pure talc variant. Experimental models with pure sand composition underwent Coulomb failure in the brittle regime. With subsequent increase in talc content, the behavior of failure switched to plastic yielding in the ductile regime. This transition from coulomb failure to plastic yielding produced a remarkable variation in the shear surface roughness characteristics. Shear surfaces formed by Coulomb failure are smooth and devoid any slickenlines, whereas, those formed by plastic yielding show prominent presence strongly linear roughness, defined by cylindrical ridge-grooves along the slip direction.</p><p>Shear surface roughness defined by linear irregularities become more prominent with increasing fracture orientation (θ) to the compression direction (θ = 30° to 60°). Increase in θ promotes the formation of smooth slickenlines at the cost of rough zones. For critical analysis and understanding of these features we develop a new computational technique. The technique is based on controlled optical images to map the shear surface geometry from field casts and laboratory samples. Binarization of the irregular surface images (cantor set) provides 1D fractal dimension (D), which is used to quantify the roughness variability, and the degree of their anisotropy in terms of ΔD (difference in D across and along the slip direction). From numerical models, we finally show onset of wave instability in the mechanically distinct rupture zone as an alternative mechanism for slickenlines formation.  </p>

A Parametric Analysis of the Gear Surface Roughness After Hobbing

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Lars Vedmar
Keyword(s):  
Surface Roughness ◽  
Smooth Surface ◽  
Three Dimensional ◽  
Surface Topology ◽  
Roughness Parameters ◽  
Surface Geometry ◽  
Manufacturing Method ◽  
Differentiable Functions ◽  
Involute Gears ◽  
Dimensional Surface

Hobbing is a common manufacturing method when producing helical, involute gears. In order to give the manufactured gear a controlled surface smoothness, a method to, very accurately, determine the achieved surface geometry is needed. In this report, the cutting surfaces of the tool, of which the cutting edges are the boundaries, are assumed to be plane in arbitrary directions. They are mathematically described using parametric and analytically differentiable functions. These functions give the possibility to determine the geometry of the three-dimensional surface of the manufactured gear, without any additional numeric approximations. By comparing this surface with the smooth surface of an ideal gear, the roughness of the surface can be determined. An example is given in which the surface topology and the characteristic surface roughness parameters are determined.

Geophysical inversion for 3D contact surface geometry

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. K27-K45
Author(s):  
Christopher G. Galley ◽  
Peter G. Lelièvre ◽  
Colin G. Farquharson
Keyword(s):  
Three Dimensional ◽  
Massive Sulfide ◽  
Detection Methods ◽  
Sulfide Deposit ◽  
Model Parameters ◽  
Initial Surface ◽  
Model Assessment ◽  
Surface Geometry ◽  
Geophysical Inversion ◽  
The Earth

Geologists’ interpretations about the earth typically involve distinct rock units with contacts between them. Three-dimensional geologic models typically comprise surfaces of tessellated polygons that represent the contacts. In contrast, geophysical inversions typically are performed on voxel meshes comprising space-filling elements. Standard minimum-structure voxel inversions recover smooth models, inconsistent with typical geologic interpretations. Various voxel inversion methods have been developed that attempt to produce models more consistent with such interpretations. However, many of those methods involve increased numerical challenges and ultimately the underlying parameterization of the earth is still inconsistent with geologists’ interpretations. Surface geometry inversion (SGI) is a fundamentally different approach that effectively takes some initial surface-based model and alters the position of the contact surfaces to better fit the geophysical data. Many authors have developed SGI methods. In contrast to those, we are the first to develop a method with the following characteristics: we work directly with 3D explicit surfaces from an input geologic model of arbitrary complexity; we incorporate intersection detection methods to avoid unacceptable topological scenarios; we use global optimization strategies and stochastic sampling to solve the inverse problem and aid model assessment; and we use surface subdivision to reduce the number of model parameters, which also provides regularization without adding the complication of trade-off parameters in the objective function. We test our methods on simpler synthetic examples taken from early influential literature, and we demonstrate their typical use on a more complicated example based on a seafloor massive sulfide deposit. Our work provides a geophysical inversion approach that can work directly with 3D surface-based geologic models. With this approach, geophysical and geologic models can share the same parameterization; there is only a single model, with no need to translate information between two inconsistent parameterizations.

The Effect of Roughness Features on Mos Surface Electric Field and Fowler-Nordheim Tunneling Behavior

1997 ◽  
Vol 473 ◽  
Author(s):  
Heng-Chih Lin ◽  
Edwin C. Kan ◽  
Toshiaki Yamanaka ◽  
Simon J. Fang ◽  
Kwame N. Eason ◽  
...  
Keyword(s):  
Electric Field ◽  
Three Dimensional ◽  
Tunneling Current ◽  
Gate Oxide ◽  
Oxide Thickness ◽  
Interface Roughness ◽  
Normal Electric Field ◽  
Surface Electric Field ◽  
Tunneling Behavior ◽  
Nordheim Tunneling

ABSTRACTFor future CMOS GSI technology, Si/SiO2 interface micro-roughness becomes a non-negligible problem. Interface roughness causes fluctuations of the surface normal electric field, which, in turn, change the gate oxide Fowler-Nordheim tunneling behavior. In this research, we used a simple two-spheres model and a three-dimensional Laplace solver to simulate the electric field and the tunneling current in the oxide region. Our results show that both quantities are strong functions of roughness spatial wavelength, associated amplitude, and oxide thickness. We found that RMS roughness itself cannot fully characterize surface roughness and that roughness has a larger effect for thicker oxide in terms of surface electric field and tunneling behavior.

Experimental investigation and modelling of light scattering in a-Si:H solar cells deposited on glass/ZnO:Al substrates

2002 ◽  
Vol 715 ◽  
Author(s):  
J. Krc ◽  
M. Zeman ◽  
O. Kluth ◽  
F. Smole ◽  
M. Topic
Keyword(s):  
Surface Roughness ◽  
Experimental Investigation ◽  
Solar Cells ◽  
Angular Distribution ◽  
Light Scattering ◽  
Optical Model ◽  
Distribution Functions ◽  
Interface Roughness ◽  
Scattering Parameters ◽  
Good Agreement

AbstractThe descriptive scattering parameters, haze and angular distribution functions of textured ZnO:Al transparent conductive oxides with different surface roughness are measured. An approach to determine the scattering parameters of all internal interfaces in p-i-n a-Si:H solar cells deposited on the glass/ZnO:Al substrates is presented. Using the determined scattering parameters as the input parameters of the optical model, a good agreement between the measured and simulated quantum efficiencies of the p-i-n a-Si:H solar cells with different interface roughness is achieved.

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