scholarly journals Effects of Nanopillar Size and Spacing on Mechanical Perturbation and Bactericidal Killing Efficiency

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2472
Author(s):  
Amar Velic ◽  
Alka Jaggessar ◽  
Tuquabo Tesfamichael ◽  
Zhiyong Li ◽  
Prasad K. D. V. Yarlagadda
Keyword(s):  
Combined Stress ◽  
Mechanical Perturbation ◽  
Simultaneous Reduction ◽  
Biophysical Models ◽  
Out Of Plane ◽  
Contour Plots ◽  
Potential Failure ◽  
Key Dimensions ◽  
Von Mises ◽  
Tip Radius

Nanopatterned surfaces administer antibacterial activity through contact-induced mechanical stresses and strains, which can be modulated by changing the nanopattern’s radius, spacing and height. However, due to conflicting recommendations throughout the theoretical literature with poor agreement to reported experimental trends, it remains unclear whether these key dimensions—particularly radius and spacing—should be increased or decreased to maximize bactericidal efficiency. It is shown here that a potential failure of biophysical models lies in neglecting any out-of-plane effects of nanopattern contact. To highlight this, stresses induced by a nanopattern were studied via an analytical model based on minimization of strain and adhesion energy. The in-plane (areal) and out-of-plane (contact pressure) stresses at equilibrium were derived, as well as a combined stress (von Mises), which comprises both. Contour plots were produced to illustrate which nanopatterns elicited the highest stresses over all combinations of tip radius between 0 and 100 nm and center spacing between 0 and 200 nm. Considering both the in-plane and out-of-plane stresses drastically transformed the contour plots from those when only in-plane stress was evaluated, clearly favoring small tipped, tightly packed nanopatterns. In addition, the effect of changes to radius and spacing in terms of the combined stress showed the best qualitative agreement with previous reported trends in killing efficiency. Together, the results affirm that the killing efficiency of a nanopattern can be maximized by simultaneous reduction in tip radius and increase in nanopattern packing ratio (i.e., radius/spacing). These findings provide a guide for the design of highly bactericidal nanopatterned surfaces.

Rough Contact Between Elastically and Geometrically Identical Curved Bodies

1982 ◽  
Vol 49 (2) ◽  
pp. 345-352 ◽  
Author(s):  
M. D. Bryant ◽  
L. M. Keer
Keyword(s):  
Maximum Principle ◽  
Brittle Fracture ◽  
Contact Area ◽  
Yield Criterion ◽  
Failure Criteria ◽  
Tensile Stresses ◽  
Potential Failure ◽  
Elliptical Contact ◽  
Normal And Tangential Loads ◽  
Von Mises

Surface and subsurface stresses and displacements are obtained when two geometrically and elastically identical rough bodies are pressed together by normal and tangential loads. The theories of Cattaneo and Mindlin, who introduce zones of slip and stick within an elliptical contact area, are used. Von Mises yield criterion and maximum principle tensile stresses are used as failure criteria to assess potential failure due to shear or brittle fracture.

A Three-Dimensional Finite Element Stress Analysis and Strength Prediction of CFRP Adhesive Laminated Plates Subjected to Static and Impact Out-of-Plane Loadings

2009 ◽  
Author(s):  
Yukiya Noshita ◽  
Toshiyuki Sawa ◽  
Yuya Omiya
Keyword(s):  
Equivalent Stress ◽  
Three Dimensional ◽  
Laminated Plates ◽  
Stress Distributions ◽  
Maximum Value ◽  
Out Of Plane ◽  
Dimensional Finite Element ◽  
Von Mises Equivalent Stress ◽  
Von Mises ◽  
Three Dimensional Finite Element

Stress distributions in CFRP adhesive laminated plates subjected to static and impact out-of-plane loadings are analyzed using a three-dimensional finite-element method (FEM). For establishing an optimum design method of the laminated plates, the effects of some factors are examined. As the results, it is found that the maximum value of the von Mises equivalent stress σ eqv occurs at the edge of the CFRP’s interfaces. The maximum value of interface shear stress r i at CFRP interface decreases as the reinforced Young’s modulus and the thickness increases. However, the maximum value of σ eqv at the adhesive layer decreases as the reinforced Young’s modulus and the thickness decreases. In addition, the maximum value of r i at the CFRP’s interface of lower reinforced laminates under impact loadings shows opposite characteristics to those under static loadings. For verification of the FEM calculations, experiments were carried out to measure the strains at the interfaces and the laminates plates strengths. Concerning strain and strength prediction based on von Mises equivalent stress, fairly good agreements were found between the numerical and the experimental results. The FEM results of impacted strain are in fairly good consistent with the measured results. Discussion is made on the effects of some factors on interface stress distributions.

A Multiaxial Fatigue Reliability Analysis Method of Casing Drilling in Casing String

2011 ◽  
Vol 347-353 ◽  
pp. 1749-1753
Author(s):  
Ping Wang ◽  
Zhan Qu ◽  
Jiong Zhang ◽  
Jian Bing Zhang ◽  
Liang Wang
Keyword(s):  
Fatigue Life ◽  
Equivalent Stress ◽  
Multiaxial Fatigue ◽  
Analysis Method ◽  
Fatigue Reliability ◽  
Combined Stress ◽  
Biaxial Fatigue ◽  
Von Mises Equivalent Stress ◽  
Von Mises ◽  
Stress Criteria

The Von Mises equivalent stress criteria is used to equivalent convert and correct the uniaxial and biaxial fatigue reliability experimental study of the casing material. And the probabilistic fatigue P–S–N curve of the casing is gained. The fatigue limit and fatigue life in test is equivalent convert to actual casing by combined stress correction factor. A multiaxial fatigue life calculation formula is proposed by correcting the probabilistic fatigue P–S–N curve.

A Unified, Self-Consistent Theory for the Plastic-Creep Deformation of Metals

1982 ◽  
Vol 49 (4) ◽  
pp. 728-734 ◽  
Author(s):  
G. J. Weng
Keyword(s):  
Plastic Deformation ◽  
304 Stainless Steel ◽  
Plastic Strains ◽  
Combined Stress ◽  
Consistent Theory ◽  
Model Following ◽  
Self Consistent ◽  
Von Mises ◽  
Inelastic Strains ◽  
Plastic Creep

A unified, self-consistent scheme is formulated to determine the plastic-creep behavior of metals under combined stress. It is pointed out that such a deformation involves the transition from the inhomogeneity to transformation problem in the sense of Eshelby. The plastic deformation is studied by the Berveiller and Zaoui modification of Hill’s model. Following plastic deformation the structure of self-consistent relation for subsequent creep is analyzed and found to be independent of prior plastic strains. These self-consistent relations are used in conjunction with one set of unified constitutive equations for slip systems, in which the effect of prior plastic strains on the subsequent creep is considered. This unified, self-consistent scheme is applied to predict the plastic-creep strains of a 304 stainless steel. As compared to the experimental data, the self-consistent scheme is found to consistently provide reasonably accurate estimates for the total inelastic strains, while the predictions by the von Mises theory are seen to be less favorable.

scholarly journals Accurate Numerical Solutions for Elastic-Plastic Models

1979 ◽  
Vol 101 (3) ◽  
pp. 226-234 ◽  
Author(s):  
H. L. Schreyer ◽  
R. F. Kulak ◽  
J. M. Kramer
Keyword(s):  
Numerical Solutions ◽  
Constant Strain Rate ◽  
Single Step ◽  
Isotropic Hardening ◽  
Contour Plots ◽  
Integration Algorithms ◽  
The Common ◽  
The Difference ◽  
Von Mises ◽  
Two Parameters

The accuracy of two integration algorithms is studied for the common engineering condition of a von Mises, isotropic hardening model under plane stress. Errors in stress predictions for given total strain increments are expressed with contour plots of two parameters; an angle in the pi-plane and the difference between the exact and computed yield surface radii. The two methods are the tangent predictor-radial return approach and the elastic predictor-radial corrector algorithm originally developed by Mendelson. The accuracy of a combined tangent predictor-radial corrector algorithm is also investigated. For single-step constant-strain-rate increments the elastic predictor-radial corrector method is generally the most accurate, although errors in angle can be significant. The use of a simple subincrementation formula with any one of the three approaches yields results that would be acceptable for most engineering problems.

scholarly journals Graphynes: an alternative lightweight solution for shock protection

2019 ◽  
Vol 10 ◽  
pp. 1588-1595 ◽  
Author(s):  
Kang Xia ◽  
Haifei Zhan ◽  
Aimin Ji ◽  
Jianli Shao ◽  
Yuantong Gu ◽  
...  
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Plane Deformation ◽  
Von Mises Stress ◽  
In Silico Studies ◽  
Fundamental Understanding ◽  
Out Of Plane ◽  
Impact Protection ◽  
Shock Protection ◽  
Von Mises

The excellent mechanical properties of graphyne (GY) have made it an appealing candidate in the field of impact protection. We assessed the deformation mechanisms of monolayer GY nanosheets of different morphologies, including α-GY, β-GY, γ-GY and 6612-GY, under supersonic-velocity impacts (from 1 to 6 km/s) based on in silico studies. Generally, cracks initiate at the geometry center and the nanosheet experiences significant out-of-plane deformation before the propagation of cracks. Tracking the atomic von Mises stress distribution, it is found that its cumulative density function has a strong correlation with the magnitude of the Young’s modulus of the GYs. For nanosheets with a higher Young’s modulus, it tends to transfer momentum at a faster rate. Thus, a better energy dissipation or delocalization is expected during impact. This study provides a fundamental understanding of the deformation and penetration mechanisms of monolayer GY nanosheets under impact, which is crucial in order to facilitate their emerging applications for impact protection.

scholarly journals DYNAMIC BEHAVIOUR OF SANDWICH PLATE WITH DIFFERENT CORE CONFIGURATION UNDER ACTION OF IMPULSIVE LOADING

2019 ◽  
Vol 18 (4) ◽  
pp. 506-526
Author(s):  
Ammar M Nemah ◽  
Hatem H Obied
Keyword(s):  
Finite Element ◽  
Sandwich Plate ◽  
Dynamic Properties ◽  
Time History ◽  
Impulsive Loading ◽  
Von Mises Stress ◽  
Finite Element Models ◽  
Out Of Plane ◽  
Bending Loads ◽  
Von Mises

Steel sandwich structures with honeycomb and corrugated cellular cores have demonstrated the capability of supporting significant static bending loads while also enabling effective mitigation of impulse loads, the main objectives to use these structures is weight reduction and isolate or reduce the deflection and stress. This research aims to study the effect of dynamic load on the dynamic properties of various types of sandwich cores then find the best model that withstand high stresses and dissipate loads with less mass was possible. The studied model of sandwich is of dimensions (500x500x100) mm with five cells. Four types of steel sandwich plate (SSP) finite element models of various core types have been created: (1) triangle corrugated core, (2) trapezoid corrugated core, (3) square honeycomb and (4) out-of plane hexagonal honeycomb, the mass of various types was constant with value of 13.75 kg. The SSP types were compared by using ANSYS (15.0) APDL software.The finite element models are examined under the effect of transient concentrated stepped load of (350N) during 10ms. The time history response showed that the minimum von-Mises stress and minimum deflection occur at triangle corrugated SSP with values of stress (12.5Mpa) and deflection (3.8 ), but in energy absorption the square honeycomb is the best type with reduction of stress (99.65%) and reduction of deflection of (98.95%).

Component Failure Analysis in MEMS Packaging

2002 ◽  
Author(s):  
J. Zou ◽  
M. Waelti ◽  
A. Bowman ◽  
J. Marchetti ◽  
C. H. Mastrangelo
Keyword(s):  
Failure Modes ◽  
Failure Criteria ◽  
Micro Electro Mechanical System ◽  
Element Analysis ◽  
Identification Methods ◽  
Mems Packaging ◽  
Potential Failure ◽  
Von Mises ◽  
Scale Failure ◽  
Improve Reliability

A finite element analysis (FEA) method used to determine the limits of package failure criteria is described. The failure criteria for the micro-electro-mechanical system (MEMS) packages presented here include von Mises, Mohr’s theory, and micro-crack phenomena. In addition, we explore the limits of micro-scale failure criteria on brittle MEMS assemblies. The paper describes stress source identification methods and failure mechanisms for packaged assemblies that can guide MEMS package designers to reduce potential failure modes and improve reliability.

scholarly journals Magnetic Shielding Study of Bonding and Aromaticity in Corannulene and Coronene

Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 861-872
Author(s):  
Peter B. Karadakov
Keyword(s):  
Ring Current ◽  
Magnetic Shielding ◽  
Ring Strain ◽  
Carbon Ring ◽  
Plane Component ◽  
Out Of Plane ◽  
Contour Plots ◽  
Shielding Tensor ◽  
Planar Geometries

Bonding and aromaticity in the bowl-shaped C5v and planar D5h geometries of corannulene and the planar D6h geometry of coronene are investigated using 3D isosurfaces and 2D contour plots of the isotropic magnetic shielding σiso(r) and, for planar geometries, of the out-of-plane component of the shielding tensor σzz(r). Corannulene and coronene both feature conjoined shielded “doughnuts” around a peripheral six-membered carbon ring, suggesting strong bonding interactions and aromatic stability; a deshielded region inside the hub ring of corannulene indicates that this ring is antiaromatic, more so in planar corannulene. The switch from the planar to the bowl-shaped geometry of corannulene is shown to enhance both bonding and the local aromaticities of the five- and six-membered rings; these factors, in addition to ring strain reduction, favour the bowl-shaped geometry. The most and least shielded bonds in both corannulene and coronene turn out to be the spoke and hub bonds, respectively. The higher π electron activity over spoke bonds in planar corannulene and coronene is supported by σzz(r) contour plots in planes 1 Å above the respective molecular planes; these findings about spoke bonds are somewhat unexpected, given that ring current studies indicate next to no currents over spoke bonds.

Layer-dependent Fracture Strength of Few-layer WS2 Induced by Interlayer Sliding: A Molecular Dynamics Study

2021 ◽  
Author(s):  
Hao Zhan ◽  
Xinfeng Tan ◽  
Xin Zhang ◽  
Guoxin Xie ◽  
Dan Guo
Keyword(s):  
Molecular Dynamics ◽  
Fracture Strength ◽  
Plane Deformation ◽  
Dynamics Simulation ◽  
Interlayer Interaction ◽  
Individual Layer ◽  
Out Of Plane ◽  
Relationship Of ◽  
Tip Radius

Abstract Understanding the relationship of interlayer interaction with mechanical properties and behaviors of two-dimensional layered materials (2DLMs) is critical in favoring the development of related nanodevices, nevertheless, still challenging due to the difficulties in experiments. In this work, nanoindentation simulations on few-layer WS2 were conducted by varying tip radius, suspended membrane radius and membrane size using molecular dynamics simulation. Consistent with our previous experimental results, few-layer WS2 exhibited layer-dependent reduction in fracture strength owing to the uneven stress distribution among individual layer induced by interlayer sliding under out-of-plane deformation. Besides, apparent curve hysteresis was observed due to interlayer sliding in the supported region when large tip radius and membrane radius were employed. However, instead of the supported part, the interlayer sliding within the suspended part resulted in the reduced fracture strength with the increase of layer number. These findings not only provide an in-depth comprehension on the influence of interlayer sliding on the fracture strength of few-layer WS2, but also suggest that the role of interlayer interaction should be seriously considered during nanodevice design.

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