Local Yielding Around a Crack Tip in Plexiglas

1970 ◽  
Vol 37 (2) ◽  
pp. 409-415 ◽  
Author(s):  
P. S. Theocaris
Keyword(s):  
Fringe Pattern ◽  
Monochromatic Light ◽  
Crack Tip ◽  
Thickness Variation ◽  
Inert Material ◽  
Monochromatic Light Beam ◽  
Edge Cracks ◽  
Highly Strained ◽  
Local Yielding ◽  
Increasing Load

An optical method was developed to study the highly strained region surrounding small edge cracks in brittle transparent materials loaded in tension. Interference of the partially reflected coherent monochromatic light beam from the front and back surfaces of the specimen prepared from an optically isotropic and inert material, gave a fringe pattern which depicted the thickness variation of the plate in the neighborhood of the crack. The fringe pattern consisted of a dense pattern surrounding the crack tip which was separated from the rest by a distinct bright envelope. It was shown for the material studied that the limiting envelope was a circle which, when projected to a screen, became an epicycloid. The evolution of the geometric characteristics of the highly strained zone with increasing load was studied, up to the critical load for a rapid crack propagation. The data obtained yielded an insight on the mechanism of fracture in brittle materials.

Interaction between collinear asymmetric cracks

1972 ◽  
Vol 7 (3) ◽  
pp. 186-193 ◽  
Author(s):  
P S Theocaris
Keyword(s):  
Light Beam ◽  
Monochromatic Light ◽  
Rear Surface ◽  
Thickness Variation ◽  
Shadow Method ◽  
Gas Laser ◽  
Light Rays ◽  
Monochromatic Light Beam ◽  
Neon Gas ◽  
Helium Neon

Thin strips made of perspex and containing two collinear internal cracks of different length were subjected to tension. The thickness variation of the strips was depicted by the reflected-shadow method, in which a coherent monochromatic light beam, emitted from a helium-neon gas laser, was partly reflected from the rear surface of the specimen. The light rays emerging from the plate, which were twice refracted along the thickness and reflected on the rear surface of the plate, were retarded according to Favre's and Neumann's law. The retarded light rays were focused on a caustic surface which depicted the boundary between the constrained area surrounding the crack tip and the remainder of the plate. In this paper two asymmetric collinear internal cracks of different lengths were studied and the interaction between these cracks was evaluated by measuring the variation of the diameter and the distortion of the shape of the caustics for various ratios of crack lengths.

Rotating Ag-Fe3O4-Au Nanograin by Optical Torque with a Monochromatic Light Beam

Plasmonics ◽  
2019 ◽  
Vol 14 (5) ◽  
pp. 1081-1089
Author(s):  
Xiaoqin Mao ◽  
Yan Li ◽  
Weiyan Jiao ◽  
Xinshun Wang ◽  
Benyang Wang
Keyword(s):  
Light Beam ◽  
Monochromatic Light ◽  
Monochromatic Light Beam ◽  
Optical Torque

Multichannel Fourier Transform Spectroscopy Using Two-Dimensional Detection of the Interferogram and its Application to Raman Spectroscopy

1993 ◽  
Vol 47 (7) ◽  
pp. 863-868 ◽  
Author(s):  
Satoshi Takahashi ◽  
Jeung Sun Ahn ◽  
Shuji Asaka ◽  
Teizo Kitagawa
Keyword(s):  
Fourier Transform ◽  
Fringe Pattern ◽  
Principal Axis ◽  
Monochromatic Light ◽  
Fourier Transform Spectroscopy ◽  
Present System ◽  
The Novel ◽  
Two Dimensional ◽  
One Dimensional ◽  
Ccd Detector

A system for multichannel Fourier transform spectroscopy was constructed by using a CCD detector and an interferometer consisting of Savart plate held between two polarizers, and practical problems associated with its application to Raman experiments were investigated. The novel idea of the present system lies in avoiding the aliasing distortion, seen in the spectrum measured with a one-dimensional multichannel detector, by arranging the principal axis of the sensitized plane of the CCD detector so that it is not coincident with the direction of the fringe pattern of the interferogram. The observed interferogram suffered geometrical distortion due to incompleteness of the Savart plate. In order to circumvent this problem, an algorithm for correcting this distortion by referring to the interferogram of appropriate monochromatic light was successfully developed. The resolution of a Raman spectrum obtained for indene was ∼40 cm−1, in agreement with the theoretical value expected for this system.

Paper 10: Measurement of an Average Size and Number of Droplets during Spontaneous Condensation of Supersaturated Steam

1969 ◽  
Vol 184 (7) ◽  
pp. 22-28 ◽  
Author(s):  
V. Petr
Keyword(s):  
Droplet Size ◽  
Static Pressure ◽  
Monochromatic Light ◽  
Measuring Error ◽  
Photometric Method ◽  
Intensity Attenuation ◽  
Spontaneous Condensation ◽  
Droplet Sizes ◽  
Monochromatic Light Beam ◽  
Average Size

This paper presents the results of measurements to determine the average size and number of droplets which appear during spontaneous condensation of expanding undercooled steam. The measurements were carried out in a non-symmetric convergent–divergent nozzle for three expansion rates, , of 2000, 5000, and 8000 units per second, and pressure in the Wilson region of 0·4–1·5 bar. The method is based on the measurement of monochromatic light beam intensity attenuation when passing through a layer of wet steam of length l (width of the nozzle) and static pressure variation through the nozzle axis. The photometric method was verified by measuring the droplet sizes in sulphur emulsion. The average size and number of droplets during spontaneous condensation were found to be dependent on the expansion rate and pressure in the Wilson region, and the results of the measurement are in qualitative agreement with those obtained by Gyarmathy. The average droplet size measured by the photometric method is about 25–60 per cent greater than the corresponding values of Gyarmathy. The droplet size measuring error, determined by an approximate analysis, was found to be in the range 15–30 per cent.

Experimental Analysis of Deformation Induced Microstructure Near a Crack Tip in a Hardened Copper Crystal

1998 ◽  
Vol 539 ◽  
Author(s):  
A.-F. Bastawros ◽  
K.-S. Kim
Keyword(s):  
Outer Boundary ◽  
Strain Tensor ◽  
Crack Tip ◽  
Characteristic Distance ◽  
Copper Crystal ◽  
Additional Mode ◽  
Point Bend ◽  
Lagrange Strain ◽  
Mode Ii Loading ◽  
Increasing Load

AbstractThe incremental in-plane Green-Lagrange strain tensor was measured near a stationary crack tip in a cyclically work-hardened copper single crystal. Measurements were made on the surface of a four-point bend specimen, using a finite-deformation laser moiré interferometer. The measurement showed the existence of a narrow asymptotic field beyond a distance of 300 μm from the crack tip. The inner boundary of the asymptotic zone was almost fixed at a characteristic distance ahead of the crack tip. This length scale is thought to arise from a microstructural evolution near the crack tip. The inhomogeneous hardening due to glide-band clustering and patchy slip in a small volume near the crack tip triggered such an evolution. The outer boundary of the asymptotic zone radially grew with the increasing load. The deformation field was found to be very sensitive to additional mode II loading.

Viscoelastic Analysis of Adhesively Bonded Double – Lap Joint

2007 ◽  
Vol 345-346 ◽  
pp. 1473-1476
Author(s):  
Sang Soon Lee
Keyword(s):  
Room Temperature ◽  
Viscoelastic Model ◽  
Tensile Load ◽  
Adhesive Layer ◽  
Lap Joint ◽  
Epoxy System ◽  
Adhesively Bonded ◽  
Viscoelastic Analysis ◽  
Edge Cracks ◽  
Local Yielding

In this paper, stress distribution in a double lap joint subjected to a tensile load is investigated using the boundary element method. The adhesive used in this study is a commercial epoxy system which can be cured at room temperature. The adhesive is assumed to be linearly viscoelastic. The order of the singularity is obtained numerically for a given viscoelastic model. The numerical results show that interface stresses are large enough to initiate local yielding or edge cracks. Since the exceedingly large stresses cannot be borne by the adhesive layer, edge cracks can occur at the interface corner.

Physical properties of monochromatic light beam

1968 ◽  
Vol 11 (3) ◽  
pp. 78-79
Author(s):  
A. Yu. Ardashev ◽  
V. A. Kashin ◽  
G. V. Skrotskii
Keyword(s):  
Physical Properties ◽  
Light Beam ◽  
Monochromatic Light ◽  
Monochromatic Light Beam

Determination of ordinary and extraordinary refractive indices of nematic liquid crystals by using wedge cells

2010 ◽  
Vol 18 (2) ◽  
Author(s):  
J. Kędzierski ◽  
Z. Raszewski ◽  
M. Kojdecki ◽  
E. Kruszelnicki-Nowinowski ◽  
P. Perkowski ◽  
...  
Keyword(s):  
Thin Film ◽  
Liquid Crystals ◽  
Nematic Liquid Crystals ◽  
Monochromatic Light ◽  
Refractive Indices ◽  
Multiple Reflections ◽  
Edge Angle ◽  
Interference Fringes ◽  
Monochromatic Light Beam

AbstractA new accurate and fast interference method for determining ordinary and extraordinary refractive indices of nematic liquid crystals is presented and discussed. The method relies on microscopic measurements of distances between interference fringes appearing in polarised parallel coherent monochromatic light beam transmitted normally to the surfaces through a wedge cell filled with a nematic. Both glass plates confining the cell are coated with a partly transparent thin film of metal which is deposited by evaporation in vacuum. Owing to the multiple reflections between the surfaces and a small edge angle, the interference fringes observed near the wedge apex edge are sharp and equidistant. To apply this method one needs only small amount of an investigated liquid crystal. Basic mathematical formulae and results of an experiment are briefly discussed.

THE DURATION OF THE 16 VOLT LEVELS OF NEON

1950 ◽  
Vol 28a (3) ◽  
pp. 339-358 ◽  
Author(s):  
Frank A. Grant
Keyword(s):  
Light Beam ◽  
Discharge Tube ◽  
Half Life ◽  
Electrical Discharge ◽  
Monochromatic Light ◽  
Metastable Level ◽  
Electronic Apparatus ◽  
Rate Of Decay ◽  
Monochromatic Light Beam ◽  
Measured Duration

Electronic apparatus has been developed to determine the rate of decay of the 16 volt levels of neon after the interruption of an electrical discharge, by measurement of the absorption of a monochromatic light beam. The half life of the 3P2 metastable level has been determined as a function of pressure and discharge tube diameter. The 3P0 and 3P1 levels exhibit a pronounced departure from an exponential decay. The hypothesis of the imprisonment of resonance radiation is consistent with the measured duration of the 1P1 and 3P1 levels.

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