Intrinsic Errors on Sheet Strain Measurements Based on a Printed Square Grid

1998 ◽  
Vol 122 (4) ◽  
pp. 760-765
Author(s):  
Herman C. J. Bruneel

The paper studies the intrinsic errors on strain measurements induced by the application of an electrochemical etched square grid through serigraphy. Systematic periodic strains are observed when the etched grid is directly measured before any mechanical deformation. These apparent, non-zero strains are the errors induced by the imperfection of the applied grid. They determine the limiting precision of the measuring process. The errors are due to interference between the periodic square grid and an underlying periodic structure, the dot structure of the printer used for the original drawing of the grid or the periodic pitch of the serigraphic tissue and even both. Although they are small, they can suggest an unstable deformation, even at large strains. [S1087-1357(00)02004-9]

1989 ◽  
Vol 62 (2) ◽  
pp. 357-366 ◽  
Author(s):  
N. Nakajima ◽  
R. A. Miller

Abstract Two commercial polyethylacrylate elastomers, having about 50 Mooney Index were selected. They were compounded with 50 parts of N330 carbon black per 100 parts of rubber by weight. One sample having epoxide (EP) crosslinking sites was crosslinked with ammoniumbenzoate. The other having double-bonds by copolymerizing with ethylidene norbornene (ENB) was crosslinked with a sulfur system. The vulcanizates were oven aged at 175°C for 70 h. Tensile stress-strain measurements were performed with the gum rubbers, uncured compounds, unaged vulcanizates, and heat-aged vulcanizates. The data presented as tensile modulus—strain curves revealed the following: at all strain levels, the moduli of ENB gum samples were lower than those of EP gums. After compounding with carbon black, the moduli of two samples became very similar. This indicates that ENB has more affinity with carbon black than EP has. The vulcanizates of two samples has matching moduli at 10% strain but a difference in network structure, since the molecular architecture of the gum rubbers were very different. After heat aging, moduli at small strains increased significantly but not at large strains. The increases were very similar for both samples. The heat-aging characteristics may be very similar for both samples, in spite of the difference in the chemical nature of the crosslinks.


1978 ◽  
Vol 48 ◽  
pp. 389-390 ◽  
Author(s):  
Chr. de Vegt

AbstractReduction techniques as applied to astrometric data material tend to split up traditionally into at least two different classes according to the observational technique used, namely transit circle observations and photographic observations. Although it is not realized fully in practice at present, the application of a blockadjustment technique for all kind of catalogue reductions is suggested. The term blockadjustment shall denote in this context the common adjustment of the principal unknowns which are the positions, proper motions and certain reduction parameters modelling the systematic properties of the observational process. Especially for old epoch catalogue data we frequently meet the situation that no independent detailed information on the telescope properties and other instrumental parameters, describing for example the measuring process, is available from special calibration observations or measurements; therefore the adjustment process should be highly self-calibrating, that means: all necessary information has to be extracted from the catalogue data themselves. Successful applications of this concept have been made already in the field of aerial photogrammetry.


Author(s):  
H.M. Mazzone ◽  
W.F. Engler ◽  
R. Zerillo ◽  
G.F. Bahr

The nucleopolyhedrosis virus (NPV) of the forest tent cater - pillar (Malacosoma disstria Hubner) has been analyzed in our laboratories. As a representative of the Baculovirus class, the NPV has virus particles enclosed with in a proteinaceous structure, the inclusion body.


Author(s):  
W.M. Stobbs

I do not have access to the abstracts of the first meeting of EMSA but at this, the 50th Anniversary meeting of the Electron Microscopy Society of America, I have an excuse to consider the historical origins of the approaches we take to the use of electron microscopy for the characterisation of materials. I have myself been actively involved in the use of TEM for the characterisation of heterogeneities for little more than half of that period. My own view is that it was between the 3rd International Meeting at London, and the 1956 Stockholm meeting, the first of the European series , that the foundations of the approaches we now take to the characterisation of a material using the TEM were laid down. (This was 10 years before I took dynamical theory to be etched in stone.) It was at the 1956 meeting that Menter showed lattice resolution images of sodium faujasite and Hirsch, Home and Whelan showed images of dislocations in the XlVth session on “metallography and other industrial applications”. I have always incidentally been delighted by the way the latter authors misinterpreted astonishingly clear thickness fringes in a beaten (”) foil of Al as being contrast due to “large strains”, an error which they corrected with admirable rapidity as the theory developed. At the London meeting the research described covered a broad range of approaches, including many that are only now being rediscovered as worth further effort: however such is the power of “the image” to persuade that the above two papers set trends which influence, perhaps too strongly, the approaches we take now. Menter was clear that the way the planes in his image tended to be curved was associated with the imaging conditions rather than with lattice strains, and yet it now seems to be common practice to assume that the dots in an “atomic resolution image” can faithfully represent the variations in atomic spacing at a localised defect. Even when the more reasonable approach is taken of matching the image details with a computed simulation for an assumed model, the non-uniqueness of the interpreted fit seems to be rather rarely appreciated. Hirsch et al., on the other hand, made a point of using their images to get numerical data on characteristics of the specimen they examined, such as its dislocation density, which would not be expected to be influenced by uncertainties in the contrast. Nonetheless the trends were set with microscope manufacturers producing higher and higher resolution microscopes, while the blind faith of the users in the image produced as being a near directly interpretable representation of reality seems to have increased rather than been generally questioned. But if we want to test structural models we need numbers and it is the analogue to digital conversion of the information in the image which is required.


Author(s):  
R.W. Carpenter ◽  
Changhai Li ◽  
David J. Smith

Binary Nb-Hf alloys exhibit a wide bcc solid solution phase field at temperatures above the Hfα→ß transition (2023K) and a two phase bcc+hcp field at lower temperatures. The β solvus exhibits a small slope above about 1500K, suggesting the possible existence of a miscibility gap. An earlier investigation showed that two morphological forms of precipitate occur during the bcc→hcp transformation. The equilibrium morphology is rod-type with axes along <113> bcc. The crystallographic habit of the rod precipitate follows the Burgers relations: {110}||{0001}, <112> || <1010>. The earlier metastable form, transition α, occurs as thin discs with {100} habit. The {100} discs induce large strains in the matrix. Selected area diffraction examination of regions ∼2 microns in diameter containing many disc precipitates showed that, a diffuse intensity distribution whose symmetry resembled the distribution of equilibrium α Bragg spots was associated with the disc precipitate.


2010 ◽  
Vol 69 (4) ◽  
pp. 367-378
Author(s):  
V. S. Miroshnichenko ◽  
Victor Konstantinovich Korneyenkov ◽  
Ye. B. Senkevich ◽  
D. V. Yudintsev

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