scholarly journals Post-flambage unilatéral des films minces sur substrat

2007 ◽  
pp. 941-955
Author(s):  
Guillaume Parry ◽  
Jérôme Colin ◽  
Christophe Coupeau ◽  
Alain Cimetière
Keyword(s):  
Biaxial Stress ◽  
Element Analysis ◽  
Compression Device ◽  
Critical Transitions ◽  
Atomic Force ◽  
Biaxial Stress State ◽  
The Finite Element Analysis ◽  
Rectangular Strip ◽  
Post Buckling

Various buckling equilibria can be observed on the delaminated areas of thin films. These equilibria are usually under advanced post-buckling. Results of the finite element analysis for the post-buckling equilibria of a thin film delaminated along a rectangular strip are discussed in this paper. Those results are compared with experimental observations performed with the help of an in-situ atomic force microscope coupled to a compression device which allows to vary the biaxial stress state in the film. The transitions from straightsided blisters to bubbles or telephone cord blisters are characterized. Both sub-critical and super-critical transitions are highlighted. A mapping of the various stable post-critical equilibria is given.

scholarly journals In situbending of an Au nanowire monitored by micro Laue diffraction

2015 ◽  
Vol 48 (1) ◽  
pp. 291-296 ◽  
Author(s):  
Cédric Leclere ◽  
Thomas W. Cornelius ◽  
Zhe Ren ◽  
Anton Davydok ◽  
Jean-Sébastien Micha ◽  
...  
Keyword(s):  
Atomic Force Microscope ◽  
Gold Nanowires ◽  
Element Analysis ◽  
Bending Angle ◽  
Three Point Bending ◽  
Atomic Force ◽  
Au Nanowire ◽  
Bending Process ◽  
Diffraction Patterns

This article reports on the first successful combination of micro Laue (µLaue) diffraction with an atomic force microscope forin situnanomechanical tests of individual nanostructures.In situthree-point bending on self-suspended gold nanowires was performed on the BM32 beamline at the ESRF using a specially designed atomic force microscope. During the bending process of the self-suspended wire, the evolution of µLaue diffraction patterns was monitored, allowing for extraction of the bending angle of the nanowire. This bending compares well with finite element analysis taking into account elastic constant bulk values and geometric nonlinearities. This novel experimental setup opens promising perspectives for studying mechanical properties at the nanoscale.

scholarly journals Foundations for low cost buildings

2016 ◽  
Vol 4 (2) ◽  
pp. 143-149 ◽  
Author(s):  
Sayed Abdel Salam ◽  
Mahmoud Samir El-kady
Keyword(s):  
Soil Type ◽  
Reinforcement Ratio ◽  
Strip Footing ◽  
Analysis Software ◽  
Element Analysis ◽  
Modeling And Analysis ◽  
Total Cost ◽  
The Finite Element Analysis ◽  
Rectangular Strip ◽  
Strip Footings

Abstract Attaining an economical and safe design of structures is regarded as a prerequisite for the structural engineer. The market prices of reinforcing steels have dramatically soared in recent years internationally. Therefore, the purpose of the current paper is not just reducing the ratio of reinforcing steel in the foundations for skeleton structures, but rather minimizing this ratio through choosing the most effective footing shape (folded strip footings). Folded footings have been used as an alternative to the conventional rectangular strip footings. The height of the studied model is ten floors. Two different foundation systems are used in the analysis namely; rectangular strip footings, and folded strip footings respectively. Both footing shapes will be designed as continuous footings with grid shape under the building. Comparison between the two systems is also presented regarding the concrete sections and reinforcement ratio under the same applied loads. The finite element analysis software ADINA is used in modeling and analysis of the structural and geotechnical behavior of both types of footings, with emphasis on the effect of changing the footing shape on the stresses in the footing concrete body and the underlying soils. Research results presents the internal stresses within the footing and soil domains, as well as the contact pressure distribution for a reinforced folded strip footing resting on different soil types. The influence of folding inclination angle, and soil type on the results are also studied. Results showed that folded strip footings are efficient in reducing the amount of needed reinforcements, and such efficiency in reducing the required steel reinforcement in the footings is depending on the applied footing loads, and to some degree on the soil type and properties. Reduction in the reinforcement ratio between the rectangular and folded footing types is about 26% in favor of the folded strip footings. A comparative economical study shows that the total cost of the reinforced concrete section for the folded strip footings is less than the traditional one by about 18%. This difference in cost of both types of footings is mainly due to the relatively smaller in steel reinforcement ratio needed for the folded type as compared with the rectangular ones. So, the folded strip footing is more economical than the rectangular strip footing. Highlights Two different foundation systems are used in the analysis namely; rectangular strip footings, and folded strip footings respectively. The finite element analysis software ADINA is used in modeling and analysis of structural and geotechnical behavior of both types of footings with emphasis on the effect of changing the footing shape and soil type (Ks) on the stresses and soil settlement. Results showed that the maximum value of contact pressure decreased by about 38% for folded strip footing when compared with the traditional strip footing in stiff clay soil, and by about 25% in dense sand soil when increasing vertical static load to its peak value. The reduction in the reinforcement ratio between the two types of footings is about 26% in favor of the folded strip footings. While the total cost of the concrete for the folded strip footings is less than the rectangular one by about 18%. So, the folded shape is more economical than the ordinary rectangular strip footing.

A Novel Plate-Like Sensor Utilizing Curvature-Based Stiffening for Nanometrology Applications

2020 ◽  
Author(s):  
Rafiul Shihab ◽  
Tasmirul Jalil ◽  
Burak Gulsacan ◽  
Matteo Aureli ◽  
Ryan C. Tung
Keyword(s):  
Finite Element Analysis ◽  
Atomic Force Microscopy ◽  
Natural Frequencies ◽  
Piezoelectric Actuators ◽  
Static Stiffness ◽  
Element Analysis ◽  
Force Microscopy ◽  
Transverse Curvature ◽  
Atomic Force

Abstract In this study, we propose a novel plate-like sensor which utilizes curvature-based stiffening effects for enhanced nanometrology. In the proposed concept, the stiffness and natural frequencies of the sensor can be arbitrarily adjusted by applying a transverse curvature via piezoelectric actuators, thereby enabling resonance amplification over a broad range of frequencies. The concept is validated using a macroscale experiment. Then, a microscale finite element analysis is used to study the effect of applied curvature on the microplate static stiffness and natural frequencies. We show that imposed transverse curvature is an effective way to tune the in-situ static stiffness and natural frequencies of the plate sensor system. These findings will form the basis of future curvature-based stiffening microscale studies for novel scenarios in atomic force microscopy.

Wrinkling of Thin Membrane Under Thermal Loading

2006 ◽  
Author(s):  
Jia Gao ◽  
Seungbae Park ◽  
James Pitarresi ◽  
Dorel Homentcovschi
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Compressive Stress ◽  
Critical Value ◽  
Thin Membrane ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Post Buckling ◽  
Formation And Evolution ◽  
Wrinkle Generation

There has been an increasing interest in the applications of thin membrane in space application, flexible electronic display, manufacturing of glass displays and growth of film on materials at elevated temperatures. Because of the negligible bending stiffness of thin membranes, membranes are lack of resistance to compressive stress. For the applications at high temperatures, the thermal expansion coefficient mismatch between membrane and substrate materials may generate compressive stress that causes the membrane buckling. The study of thermal buckling of isotropic elastic plate in the context of the large - deflection theory was the subject of a series of papers[1-5]. However, it has been noted that none of these papers has considered the second buckling of the membrane resulting in membrane wrinkling. The presence of wrinkles may significantly change deflection and stress profile of membranes. So, it is important to develop an effective analysis method to investigate the wrinkle formation and evolution in membrane subjected the elevated temperature. This paper presents the experiment work to investigate wrinkle formation and evolution in membranes heated from room temperature up to 170 °C. The specimens consist of polymer and metal membranes with steel and silicon substrate respectively. A wide range of membrane shapes and aspect ratios are considered in this work. An experiment set up is developed to study the deflection profiles of membranes at discrete temperatures. The information gained from this experiment work is used to validate numerical modeling results. The Finite Element Analysis results using nonlinear post-buckling analysis are also included in this paper. The nonlinear post-buckling analysis provides a good understanding of the mechanism of wrinkle generation and evolution as temperature increased. It is shown that the first buckling of membrane significantly reduces bending stiffness thus to create localized buckling modes accounting for the wrinkle generation. The wrinkle pattern is stable until the temperature reaches the next critical value. After this critical temperature, the wrinkle pattern is changed until temperature reaches the next critical value. The new wrinkle pattern is keeping evolved until the final temperature is reached. The finite element analysis results are in good agreement with experimental observations.

Modeling and Simulation of Hydraulic Fracturing Propagation in Permeable Reservoirs

2006 ◽  
Vol 324-325 ◽  
pp. 383-386 ◽  
Author(s):  
Zhi Long Lian ◽  
Xiu Xi Wang ◽  
Heng An Wu ◽  
Bing Xue ◽  
J. Zhang ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Fracture Propagation ◽  
In Situ Stress ◽  
Analysis Software ◽  
Element Analysis ◽  
Fracture Geometry ◽  
Stress Equilibrium ◽  
Continuity Equations ◽  
The Finite Element Analysis

Numerical simulation of hydraulic fracturing propagations in the permeable reservoirs was carried out with the finite element analysis software (ABAQUS). A model of coupling the stress equilibrium and fluid continuity equations was proposed and implemented. The nonuniform of sink pore pressure on the fracture surfaces which changes associated with the propagation of fracture was described by a self-developed subroutine through the FLOW in ABAQUS. Samples under different conditions were conducted for studying the rules of the propagation of hydraulic fracturing. The results show that the permeability at the fracture tip is more serious than any other places of the fracture face. The model also illustrates that the fracture geometry is mainly determined by the minimal in-situ stress. The model can be used to simulate the effects of hydraulic fracturing pressures and injection rates on fracture propagation. The results are of much significance for the design of hydraulic fracturing treatments.

Comparative Study of Post-Buckling Load Redistribution in Stiffened Aircraft Panel With and Without Material Nonlinearity

2018 ◽  
Author(s):  
Enes Aydin ◽  
Altan Kayran
Keyword(s):  
Finite Element ◽  
Material Nonlinearity ◽  
Stiffened Panel ◽  
Effective Width ◽  
Element Analysis ◽  
Buckling Behavior ◽  
The Finite Element Analysis ◽  
Post Buckling ◽  
Buckling Coefficient ◽  
Clamped Edge

In this article, a comparative study is presented on the post-buckling load redistribution in stiffened aircraft panels modeled with and without material nonlinearity. In the first part of the study, a baseline stiffened panel is generated for further investigation of the material nonlinearity on the post-buckling behavior and on the effective width of the stiffened panel. In this respect, a stiffener section which provides classical clamped edge condition is designed by matching the compression buckling coefficient determined by the finite element analysis closely with the analytically determined buckling coefficient of the clamped edge panel. Post-buckling analysis of the stiffened panel is then performed utilizing linear and nonlinear material models in the finite element analysis and the effect of material plasticity on the post-buckling behavior of the panel is ascertained. The load distribution in the stiffened panel is investigated just before the buckling of the panel and before the collapse of the panel in the post-buckled stage. The effective widths of the panel are calculated before the collapse of the panel using the load distributions determined by the finite element analyses of the panel models with and without material nonlinearity and comparisons are made with the effective width calculated by the classical effective width formulation. It is shown that material nonlinearity accounts for higher effective width and in general the classical empirical approach gives the smallest effective width.

scholarly journals Influence of Strengthening Material Behavior and Geometry Parameters on Mechanical Behavior of Biaxial Cruciform Specimen for Envelope Material

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2680
Author(s):  
Zhipeng Qu ◽  
Houdi Xiao ◽  
Mingyun Lv ◽  
Xihe Wang ◽  
Pengfei Wang ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Mechanical Behavior ◽  
Central Region ◽  
Limit State ◽  
Material Behavior ◽  
Biaxial Stress ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Envelope Material ◽  
Stress Ratios

The stratospheric airship envelope material is operated in biaxial stress, so it is necessary to study the in-plane biaxial tensile strength. In this paper, a theoretical model is developed to evaluate the mechanical properties of in-plane biaxial specimens. Being applied to the finite element analysis, the theoretical model is employed to evaluate the influence of strengthening material behavior (E*) and geometry parameters on the mechanical behavior in the central. The follows results are drawn: (i) smaller the length of the central region (Lcen), E* and larger the central region corner radius (r) contribute to smaller coefficient of variation (CV); (ii) smaller Lcen and larger E* contribute to smaller stress concentration factor (k), k in the limit state of r is larger than that in other conditions. (iii) The CV and k under stress ratio of 1:1 are smaller than those under other stress ratios. The study can provide a useful reference for the design of biaxial specimens.

Evaluation of Pipeline Stresses During Line Lowering

2008 ◽  
Author(s):  
Millan Sen ◽  
Joe Zhou
Keyword(s):  
Finite Element Analysis ◽  
Loading Condition ◽  
Analysis Program ◽  
Element Analysis ◽  
Environmental Loads ◽  
Right Of Way ◽  
The Finite Element Analysis ◽  
The Right ◽  
Maximum Stresses

The stresses induced to a pipe during line lowering are the maximum stresses that the pipeline will experience during its lifetime, in regions where there are no excessive environmental loads. During the installation of the TransCanada pipeline at Stittsville, Ontario, it was critical to limit the pipeline stresses that occurred during line lowering. This was required in order to fulfill the requirements of ECA-based flaw acceptance criteria applicable to mainline welding. However, the construction of the pipeline involved numerous challenges with regards to moving equipment during the pipeline installation, regions of deep cover requirements, and spatial restrictions on the right of way. These conditions introduced complicated loading scenarios, which made it difficult to ascertain the resulting stresses that the line lowering would apply to the pipeline. These stresses were evaluated herein using the finite element analysis program PIPLIN, with consideration of the actual in-situ installation conditions. Each loading condition was modeled individually, and the forces in the sidebooms were considered in addition to the pipeline stresses. It was determined that all the stresses in the pipeline during the line lowering were acceptable, so long as the specified boom locations remained within limits.

scholarly journals 4D Printing Pre-Strained Structures for Fast Thermal Actuation

2021 ◽  
Vol 8 ◽  
Author(s):  
Yu Zou ◽  
Zhongyi Huang ◽  
Xiying Li ◽  
Pengyu Lv
Keyword(s):  
Bilayer Structure ◽  
4D Printing ◽  
Element Analysis ◽  
Strained Layer ◽  
Thermal Actuation ◽  
The Finite Element Analysis ◽  
3D Printed ◽  
Shape Property ◽  
External Stimuli

Four-dimensional (4D) printing is an emerging technology by adding the dimension of time-dependent reconfiguration into 3D printing. It enables the 3D printed structure to change the shape, property, or functionality under external stimuli such as temperature, magnetic field, and light, etc. Among the existing 4D printed structures, thermal responsive structures are widely used for their easy operation. However, the slow actuation of the thermal responsive structures impedes the applications like soft robotics. In the current work, a pre-strained strategy is proposed to accelerate the actuation of thermal responsive structures. A 4D printing platform that can apply strain during the printing process is constructed to fabricate the pre-strained structures under the aid of in-situ tensile of the printing base. A bilayer structure with one pre-strained layer and the other non-pre-strained layer is integrally printed. Through experiments and the finite element analysis, it is demonstrated that the aspect ratio has little effect on the deformation of the bilayer structure, whereas the pre-strain plays a key role in the deformation and also greatly accelerates the actuation of the bilayer structure. Based on the 4D printed pre-strained bilayer structure, an energy-free gripper is fabricated and a fully soft crawler is printed to achieve a high running speed.

scholarly journals Modified design and use of a high-pressure environmental stage for laboratory X-ray powder diffractometers

2008 ◽  
Vol 41 (2) ◽  
pp. 350-355 ◽  
Author(s):  
Pamela S. Whitfield ◽  
A. Victoria Nawaby ◽  
Brian Blak ◽  
James Ross
Keyword(s):  
Variable Temperature ◽  
Materials Processing ◽  
Design Code ◽  
Element Analysis ◽  
Data Set ◽  
Time Resolved ◽  
X Ray ◽  
The Finite Element Analysis ◽  
American Society

The popularity of supercritical CO2for materials processing makes thein situstudy of pressures up to 10 MPa in the laboratory particularly interesting. This paper describes a modified design for a 12.4 MPa (1800 psi) variable-temperature pressure vessel based on an existing cell reported by Koster van Groos, Guggenheim & Cornell [Rev. Sci. Instrum.(2003),74, 273–275]. The modifications satisfied the demands of the American Society of Mechanical Engineers design code 31.3, leading to legal design registration, construction and subsequent hydrostatic test. The thinner windows that the finite element analysis indicated as sufficient allow for rapid data collection, even using a laboratory-based Mo source. This type of application is demonstrated with a time-resolved data set showing the crystallization of a polylactic acid–clay nanocomposite under 6.8 MPa CO2.

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