Polycarbonate as a Model Material for Three-Dimensional Photoplasticity

1973 ◽  
Vol 40 (2) ◽  
pp. 600-605 ◽  
Author(s):  
J. W. Dally ◽  
A. Mulc
Keyword(s):  
Yield Point ◽  
Strain Field ◽  
Permanent Deformation ◽  
Three Dimensional ◽  
Model Material ◽  
Yield Behavior ◽  
Molecular Scale

Polycarbonate is a polymer which exhibits extreme toughness, a pronounced yield behavior, and the ability to flow extensively prior to fracture. These characteristics coupled with its birefringent properties indicate its suitability as a model material for photoelastic analyses. This study treats the photoplastic response of polycarbonate which has been deformed well beyond the yield point and unloaded. The strain field associated with this permanent deformation is related to the birefringence by the conventional strain-optic law. The birefringence is permanently locked in the polycarbonate models on a molecular scale. The model can be sliced to isolate planes of interest and the method can be applied to study permanent strains in plastically deformed three-dimensional bodies.

An efficient approach to converting three-dimensional image data into highly accurate computational models

2008 ◽  
Vol 366 (1878) ◽  
pp. 3155-3173 ◽  
Author(s):  
P.G Young ◽  
T.B.H Beresford-West ◽  
S.R.L Coward ◽  
B Notarberardino ◽  
B Walker ◽  
...  
Keyword(s):  
Mesh Generation ◽  
Computational Models ◽  
Three Dimensional ◽  
Image Data ◽  
Model Material ◽  
Imaging Data ◽  
Material Inhomogeneity ◽  
Dimensional Image ◽  
Wide Range ◽  
Impact Modelling

Image-based meshing is opening up exciting new possibilities for the application of computational continuum mechanics methods (finite-element and computational fluid dynamics) to a wide range of biomechanical and biomedical problems that were previously intractable owing to the difficulty in obtaining suitably realistic models. Innovative surface and volume mesh generation techniques have recently been developed, which convert three-dimensional imaging data, as obtained from magnetic resonance imaging, computed tomography, micro-CT and ultrasound, for example, directly into meshes suitable for use in physics-based simulations. These techniques have several key advantages, including the ability to robustly generate meshes for topologies of arbitrary complexity (such as bioscaffolds or composite micro-architectures) and with any number of constituent materials (multi-part modelling), providing meshes in which the geometric accuracy of mesh domains is only dependent on the image accuracy (image-based accuracy) and the ability for certain problems to model material inhomogeneity by assigning the properties based on image signal strength. Commonly used mesh generation techniques will be compared with the proposed enhanced volumetric marching cubes (EVoMaCs) approach and some issues specific to simulations based on three-dimensional image data will be discussed. A number of case studies will be presented to illustrate how these techniques can be used effectively across a wide range of problems from characterization of micro-scaffolds through to head impact modelling.

scholarly journals A new methodology to identify minimum strain anatomical lines based on 3-D digital image correlation

2017 ◽  
Vol 8 (2) ◽  
pp. 337-347 ◽  
Author(s):  
Jorge Barrios-Muriel ◽  
Francisco Javier Alonso Sánchez ◽  
David Rodríguez Salgado ◽  
Francisco Romero-Sánchez
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Strain Field ◽  
Three Dimensional ◽  
Wearable Devices ◽  
Plane Motion ◽  
Human Motion ◽  
The Body ◽  
Image Correlation ◽  
Minimum Deformation

Abstract. Today there is continuous development of wearable devices in various fields such as sportswear, orthotics and personal gadgets, among others. The design of these devices involves the human body as a support environment. Based on this premise, the development of wearable devices requires an improved understanding of the skin strain field of the body segment during human motion. This paper presents a methodology based on a three dimensional digital image correlation (3D-DIC) system to measure the skin strain field and to estimate anatomical lines with minimum deformation as design criteria for the aforementioned wearable devices. The errors of displacement and strain measurement related to 3-D reconstruction and out-of-plane motion are investigated and the results are acceptable in the case of large deformation. This approach can be an effective tool to improve the design of wearable devices in the clinical orthopaedics and ergonomics fields, where comfort plays a key role in supporting the rehabilitation process.

Shakedown analysis for the evaluation of strength and bearing capacity of multilayered railway structures

2018 ◽  
Vol 232 (9) ◽  
pp. 2324-2335 ◽  
Author(s):  
Kangyu Wang ◽  
Yan Zhuang ◽  
Hanlong Liu
Keyword(s):  
Bearing Capacity ◽  
Engineering Design ◽  
Permanent Deformation ◽  
Three Dimensional ◽  
Frictional Coefficient ◽  
Repeated Loading ◽  
Residual Stress Field ◽  
Shakedown Analysis ◽  
Traffic Loads ◽  
Shakedown Limit

Shakedown analysis is a robust approach for solving the strength problem of a structure under cyclic or repeated loading, e.g. railway structures subject to rolling and sliding traffic loads. Owing to the traffic loads, which are higher than the “shakedown limit”, railway structures may fail due to the excessive permanent deformation. This paper develops the analytical shakedown solutions based on Melan’s shakedown theorem, which is then applied for the evaluation of the strength and bearing capacity of multilayered railway structures. The shakedown solutions utilize the elastic stress fields obtained from the fully three-dimensional finite/infinite model, and calculate the shakedown multiplier for each layer of railway structures by means of a self-equilibrated critical residual stress field. The shakedown limits are then determined as the minimum shakedown multiplier among all layers. Parametric studies are also conducted, which indicate how the frictional coefficient, strength and stiffness of the materials, and the thickness ratio of ballast to subballast influence the shakedown limit and the stability condition of railway structures. The critical points of shakedown occur at the rail for low values of rail’s yield stress and large frictional coefficient, while they occur at the ballast layer when the frictional coefficient is relatively small. The shakedown limits are found to decrease with the increase in the strength and thickness of the ballast for a relatively small frictional coefficient. For the engineering design, there is an optimum combination of material properties and layer thickness, which provides the maximum bearing capacity of the railway structure based on this research. The results obtained from this study can provide a useful reference for the engineering design of railway structures.

Three-dimensional instability of Burgers and Lamb–Oseen vortices in a strain field

1999 ◽  
Vol 378 ◽  
pp. 145-166 ◽  
Author(s):  
CHRISTOPHE ELOY ◽  
STÉPHANE LE DIZÈS
Keyword(s):  
Strain Field ◽  
Three Dimensional ◽  
Small Strain ◽  
Kelvin Waves ◽  
Large Reynolds Number ◽  
Axisymmetric Vortex ◽  
Burgers Vortex ◽  
Additional Strain ◽  
Instability Characteristic ◽  
Dimensional Instability

The linear stability of Burgers and Lamb–Oseen vortices is addressed when the vortex of circulation Γ and radius δ is subjected to an additional strain field of rate s perpendicular to the vorticity axis. The resulting non-axisymmetric vortex is analysed in the limit of large Reynolds number RΓ=Γ/v and small strain s[Lt ]Γ/δ2 by considering the approximations obtained by Moffatt et al. (1994) and Jiménez et al. (1996) for each case respectively. For both vortices, the TWMS instability (Tsai & Widnall 1976; Moore & Saffman 1975) is shown to be active, i.e. stationary helical Kelvin waves of azimuthal wavenumbers m=1 and m=−1 resonate and are amplified by the external strain in the neighbourhood of critical axial wavenumbers which are computed. The additional effects of diffusion for the Lamb–Oseen vortex and stretching for the Burgers vortex are proved to limit in time the resonance. The transient growth of the helical waves is analysed in detail for the distinguished scaling s∼Γ/ (δ2R1/2Γ). An amplitude equation describing the resonance is obtained and the maximum gain of the wave amplitudes is calculated. The effect of the vorticity profile on the instability characteristic as well as of a time-varying stretching rate are analysed. In particular the stretching rate maximizing the instability is calculated. The results are also discussed in the light of recent observations in experiments and numerical simulations. It is argued that the Kelvin waves resonance mechanism could explain various dynamical behaviours of vortex filaments in turbulence.

X-ray microbeam three-dimensional topography for dislocation strain-field analysis of 4H-SiC

2013 ◽  
Vol 114 (2) ◽  
pp. 023511 ◽  
Author(s):  
R. Tanuma ◽  
D. Mori ◽  
I. Kamata ◽  
H. Tsuchida
Keyword(s):  
Strain Field ◽  
Three Dimensional ◽  
Field Analysis ◽  
X Ray

scholarly journals A new elastic slot system and V-wire mechanics

2017 ◽  
Vol 87 (5) ◽  
pp. 774-781 ◽  
Author(s):  
Andrea Wichelhaus
Keyword(s):  
Permanent Deformation ◽  
Biomechanical Testing ◽  
Three Dimensional ◽  
Nickel Titanium ◽  
Dental Arch ◽  
Rectangular Slot ◽  
Torque Measurements ◽  
Conventional Brackets ◽  
The Wire ◽  
The Moment

ABSTRACT Objective: To biomechanically test a new elastic slot system and V-wire mechanics. Materials and Methods: Conventional twin and self-ligating brackets and the new elastodynamic bracket were biomechanically tested. The conventional brackets had a rectangular 0.022′′ slot and the new elastodynamic bracket had a V-slot, a new slot geometry. Torque measurements were performed with 0.018′′ × 0.025′′ and 0.019′′ × 0.025′′ stainless steel (ss) archwires. A nickel-titanium V wire was used for the biomechanical measurements on the elastodynamic bracket. The measurements were done with the aid of a six-component measuring sensor. Results: The results of the biomechanical testing revealed play in the brackets with rectangular slot geometry. The V slot in the elastodynamic bracket assured that the wire fit perfectly in the slot. Dynamic moments of 5 to 10 Nmm were transmitted without any play. No permanent deformation of the slot occurred in the new elastodynamic bracket because of the elastic slot. Conclusion: Control of torque for three-dimensional positioning of the teeth in the dental arch with rectangular slot geometry as used in straight-wire therapy is difficult. If torque is bent into the wire, because of the play there is a high risk that either too much, too little, or no moment is transmitted to the teeth. The V-slot archwire/bracket geometry in conjunction with nickel titanium composition has no play and allows a reduction of forces and moments with direct and continuous transmission of torque in the bracket. Because of the elasticity of the bracket, there is an upper limit to the moment possible.

A Study on the Safety Assessment of Car-Body Structure for Urban EMU

2007 ◽  
Vol 345-346 ◽  
pp. 673-676
Author(s):  
Jong Duk Chung ◽  
Jang Sik Pyun
Keyword(s):  
Safety Assessment ◽  
Load Transfer ◽  
Permanent Deformation ◽  
Three Dimensional ◽  
Engineering Analysis ◽  
Analysis Techniques ◽  
Crashworthiness Analysis ◽  
Safety Diagnosis ◽  
Transfer Mechanisms ◽  
Good Agreement

Engineering safety diagnosis of crashed subway electric multiple units (EMUs) was conducted for safety assessment. Several advanced engineering analysis techniques including nondestructive evaluation (NDE) techniques and stress and structural analyses programs, were performed for better understandings and exploration of failure analysis and safety concerns. Moreover, stress and structural analyses using commercial I-DEAS software provided important information on stress distribution and load transfer mechanisms as well as the amount of damages during the crash. One-dimensional crashworthiness was conducted to estimate the speed at the time of the accident by investigating the permanent deformation of the train. The estimated speed was used as the input value of a three-dimensional crashworthiness analysis. A good agreement has been found between structural analysis results and the results of actual damages in EMUs during crash. In this investigation, various advanced engineering analysis techniques for the safety analysis of subway EMUs have been introduced and the analysis results have been used to provide the critical information for the safety assessment of crashed EMUs.

New Model Material for Three-Dimensional Stress Analysis

1975 ◽  
Vol 3 (5) ◽  
pp. 368 ◽  
Author(s):  
SF Etris ◽  
YR Fiorini ◽  
KC Lieb ◽  
IC Moore ◽  
AL Batik ◽  
...  
Keyword(s):  
Stress Analysis ◽  
Three Dimensional ◽  
Model Material ◽  
New Model
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