ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A two-dimensional hybrid experimental-numerical technique for elastic-plastic stress analysis is presented. This technique results from merging two relatively new technologies in engineering mechanics: boundary-element methods and image processing. A syntactic pattern recognition scheme, termed ‘displacement pattern matching’ (DPM), determines the displacement boundary conditions which are used in an elasticplastic boundary-element method (EPBEM) code. The result is an automated stress-analysis tool. Displacement pattern matching is a process where displacements are measured by tracking an arbitrary array of ‘black’ spots on a ‘white’ specimen. The digitized images of the specimen are compared in a double-exposure format to determine displacements. Displacement pattern matching is a full-field technique, with spatial resolution on the order of. 1 pixels. Displacement pattern matching supplies the actual specimen displacement increments to the EPBEM code which is based on a von Mises, isotropic work-hardening constitutive model. Given these displacements and free surface conditions, EPBEM is able to incrementally calculate the internal state of stress at selected locations. Results obtained for a variety of geometries and loading conditions compared well with ANSYS finite-element solutions and selected published experimental solutions and therefore are encouraging.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper discusses briefly the principles of gaseous and ruby lasers and makes comparisons of pertinent properties of lasers and conventional light sources. Since the output from a laser is a highly collimated beam of monochromatic light that can be made extremely intense and plane polarized, the eminent suitability of lasers as light sources for photoelasticity is suggested. Lasers are shown to be superior to conventional light sources, especially for the scattered-light method and for high-speed dynamic work. Experiments are described and results are given for using lasers for (1) the scattered-light method, (2) a conventional transmission polariscope with static loads and (3) dynamic photoelasticity.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Since experimental techniques using dynamic photoelasticity are, in general, limited by suitably intense monochromatic light sources, it was of primary importance to describe a ruby-laser system which would completely remove this particular aspect of the problem. Modulation of the system, in this case by a Kerr cell, provides the necessary control of the light output such that a complete series of results can be obtained by putting together the results of many individual tests recorded on a conventional still camera. In this case, the dynamic-stress-concentration factor in a strut with a symmetrically located circular discontinuity was determined to establish definitely the potential of the system.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An ultrahigh-speed multiple-frame recording system for two- and three-dimensional dynamic photomechanics has been developed and is described here. The output from a ruby laser is modulated with a Pockels cell to produce a train of short, intense, monochromatic and polarized light pulses. Pulse widths of 50 nsec and repetition rates of up to 170,000 pulses/sec are obtained. These light pulses are synchronized with a “smear camera” and the event to produce a multiple-frame record of the phenomenon. The simplified camera requirements necessary for this purpose are indicated. The system is demonstrated by recording two-dimensional dynamic and scattered-light isochromatic fringe patterns. The capability of multiple recording of scattered-light fringe patterns, achieved here for the first time, has a tremendous potential for three-dimensional dynamic stress analysis. The developed system is also well suited for dynamic moiré, interferometry and holography.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1871-4528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Zusammenfassung Die Stärke der Besiedlung der Kartoffelpflanzungen durch migrienrende Blattläuse hängt in erster Linie vom Gelingen der Frühjahrsmigration der Überwinterungsorten ab. Das weitere Verhalten der Läuse und ihrer Nachkommenschaft auf den Kartoffelpflanzen wird jedoch durch physiologische Einflüsse seitens der Wirtspflanzen bestimmt. Der Schwerpunkt der anfänglichen Besiedlung durch geflügelte Pfirsichblattläuse (Myzus persicae Sulz.) liegt immer auf den untern Blättern des Hauptstengels (Tabelle 1). Von hier aus erfolgt normalerweise die Infektion aufwärts zu den mittleren, alternden Blättern und auswärts zu den achselständigen Sprossen (Abb 2), wo die Blätter die gleiche Entwicklung durchlaufen wie am Hauptstengel. Bedingt durch die Bevorzugung der alternden Blätter durch diese Blattlausart bilden sich auf der FrühsorteArran Pilot im Vergleich zu den andern untersuchten Sorten stärkere Populationen, da bei dieser Sorte alternde Blätter zuerst vorhanden sind. Dies war sehr deutlich im Jahre 1951 (Taylor, 1955); im Jahre 1952, als die meisten Sorten infolge der Trockenheit bald nach der Frühjahrsmigration der Blattläuse vorzeitigabreiften, war der Höchstbefall durchMyzus persicae bei der SorteArran Pilot nur an den Hauptstengeln gesichert schwerer als bei den übrigen Sorten (Abb, 3,Tabelle: 2), Wird der Blattlausbefall pro Pflanze zum Ausdruck gebracht, das heisst sowohl auf den Hauptstengeln wie auf den achselständigen Sprossen zusammen, so ist dieser aufArran Pilot ähnlich, wie auf den meisten anderen Sorten. Die Infektion durchMacrosiphum cuphorbiae Thos. erfolgt auf den jungen, wachsenden Blättern an der Spitze der Triebe. Auf den spät reifenden SortenKing Edward undStormont Dawn, die eine grössere Zahl von Seitensprossen aufweisen, entwickelten sich grössere Populationen als auf den FrühsortenArran Pilot undUlster Chieftain (Abb 3,Tabelle 2). Ungeflügeite Tiere vonAphis nasturtii,Kltb, zeigen keinerlei Bevorzugung eines bestimmten Blattyps und besiedeln Blätter aller Wachstumsphasen. Sofern die Bedingungen für die Entwicklung von grossen Populationen dieser Art günstig sind, wie dies 1952 der Fali war (Abb. 1), ist die vorhandene Blattfläche der begrenzende Faktor. Die spät reifenden SortenKing Edward undStormont Dawn bilden eine grössere Zahl von Blättern als die Frühsorten und bieten demnach mehr Möglichkeit für das Entstehen von grösseren Populationen vonAphis nasturii (Abb. 3,Tabelle 2). Unterschiede in den Blattlauspopulationen verschiedener Kartoffelsorten sind eher durch das Pflanzenwachstum bedingt als durch innere geschmackliche Unterschiede. Sorten mit grossem Blattwerk bieten grösseren Populationen vonAphis nasturtii Platz als solche mit kleinerem Blattwerk.M. euphorbiae besiedelt in der Regel die Spitzen der Triebe und da die spät reifenden Sorten viele achselständige Sprosse bilden, werden sie stärker infiziert als Frühsorten mit wenig Seitensprossen. Die Stärke des Befalls durchMyzus persicae steht im Zusammenhang mit dem Alter der Blätter. Sorten wieArran Pilot, die ihr Wachstum rasch abschliessen, sind deshalb unter normalen Bedingungen immer besser für die Besiedlung durchMyzus persicae und deren Vermehrung geeignet. Bei Bedingungen, unter welchen die Reife der andern Sorten beschleunigt wird, wird auch die Eignung dieser Sorten für Wirtspflanze gefördert.
    Abstract: Résumé Le degré de colonisation des cultures de pommes de terre par les pucerons migrants dépend avant tout du succès du vol de printemps à partir des lieux d'hivernage. Mais ensuite, le comportement des pucerons migrants et de leur descendance est determine par des influences physiologiques de la part de la plante-hôte. Le centre de colonisation initiale par le puceron ailéMyzus persicae Sulz se trouve invariablement sur les feuilles inférieures de la tige principale (Tableau 1) et de là, l'infestation gagne d'ordinaire les feuilles de la partie moyenne de la tige lorsqu'elles commencent à vieillir et, vers la périphérie, les pousses axillaires (Fig. 2). où les feuilles suivent un cycle de croissance analogue à celui des feuilles de la tige principale. par suite de cette préférence marquée qu'elles manifestent pour les feuilles vieillissantes de la plante de pomme de terre, les populations deM. persicae se développent plus nombreuses sur la variété précoceArran Pilot que sur les autres variétés étudiées, parce que les feuilles vieillissantes sont présentées le plus tôt par cette variété. Ce fait se manifesta très nettement en 1951 (Taylor, 1955), mais en 1952. la sécheresse survenue aprés la période de première migration causant un vieillissement prématuré de la plupart des variétés de pommes de terre, seules les trés nombreuses populations deM. persicae sur la tige principale des plantesArran Pilot furent significativement supérieures aux populations trouvées sur les autres variétés (Fig. 3,Tableau 2). Si l'on exprimait la densité de population en nombres de pucerons par plante, e'est-à-dire par tige prineipale avec pousses axillaires, les populations trouvées sur les plantes de la variétéArran Pilot étaient égales à celles de la plupart des autres variétés. L'infestation parMacrosiphum euphorbiae Thos. s'observe sur les jeunes feuilles en développement au bout des tiges. Des populations plus importantes se developpaient sur les variétés tardivesKing Edward etStormont Dawn, dont les pousses axillaires étaient les plus nombreuses, que sur les variétés précocesArran Pilot etUlster Chieftain (Fig. 3,Tabltau 2). Les aptèresAphis nasturtii Kltb. ne manifestent pas de préférence vis-à-vis du type de feuilles et les colonisent à n'importe quel degré de croissance. Lorsque les conditions favorisent le développement d'infestations importantes par cette espèce, comme cela se produisit en 1952 (Fig. 1), le principal facteur limitant le développement de la population est constitué par la superficie du feuillage. Les variétés tardivesKing Edward etStormont Dawn produisaient un plus grand nombre de feuilles que les variétés précoces et, par conséquent, présentèrent des populations plus importantes d'A. nasturtii (Fig. 3,Tableau 2). Les différences de densité de population des pucerons d'une variété de pommes de terre à l'autre sont peut-être dues plutôt à des différences de croissance des plantes qu'à des différences intrinsèques de goût. Les variétés à fanes fort développées hébergent de plus nombreuses populations d'A. nasturtii que les variétés à fanes peu développées.M. euphorbiae colonise généralement les extrémités des pousses axillaires, de sorte que les variétés tardives à pousses nombreuses sont plus gravement infestées que les variétés précoces, qui ont peu de pousses axillaires. L'infestation parM. persicae se rattache au vieillissement des feuilles et si une variété telle qu'Arran Pilot, dont le cycle de croissance s'accomplit rapidement, convient toujours le mieux à la colonisation parM. persicae et à sa multiplication dans des circonstances normales, les conditions exceptionnelles occasionnant un rapide vieillissement d'autre variétés peuvent rendre ces dernières aussi appropriées comme hôtes.
    Notes: Summary The distribution and multiplication of aphids on the potato plant is related to the growth of the plants.Myzus persicae Sulz. prefers senescent leaves and the biggest populations are usually found on the early potato varieties which develop such leaves first. Macrosiphum euphorbiae Thos. infests the tips of the shoots and hence maincrop varieties with many axillary shoots bear bigger populations than early varieties with fewer axillary shoots. Populations ofAphis nasturtii Kltb. are directly related to leaf area and varieties with large haulms are more heavily infested than varieties with smaller haulms.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A shortcoming of the conventional holographic interferometer used in photoelasticity is that, for the double-exposure cases, the resulting fringe patterns are a complex combination of conventional isochromatic and isopachic fringes. This paper describes a holographic interferometer that may be used to obtain separate but simultaneous isochromatic- and isopachic-fringe patterns for photoelastic models in states of plane stress. The method requires a model with a partially reflecting front surface. Isopachics, which are proportional to the thickness change, are recorded using holographic interferometry from the transmitted light. The isochromatics are obtained from the transmitted light by conventional means. General equations relating the surface displacement of the specimen to the observed fringe patterns are developed, and examples of static and dynamic loadings are shown.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experimental mechanics 21 (1981), S. 436-440 
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A common glass plate has been shown to be an adaptable and effective tool for use in speckle-shearing interferometry. Analyses of both the imaging system and the optical-filtering arrangement have been developed. Experiments were performed successfully. The results of these experiments have shown that visible speckle correlation fringes related to the derivatives of surface displacement are obtained when a common glass plate is used as a shearing component.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Experimental mechanics 15 (1975), S. 289-294 
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An ultra-high-speed camera utilizing an acousto-optic device for deflecting light rays is described. The system employs a pulsed-ruby-laser light source used in conjunction with a Cranz-Schardin-type camera thus utilizing the best features of both systems for recording a sequence of photographs. The system has been demonstrated at framing rates of up to 200,000 frames/s and has the potential for considerably faster operation. It features the capability of producing a sequence of dynamic photographs in which the time between succesive exposures can be independently varied. Thus, the frequency at which photographs are obtained can be increased during the times of greatest interest. Experimental results demonstrating these features are given.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Experimental mechanics 28 (1988), S. 170-176 
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An interferometric-fiber-optic sensor and an efficient fringe-detection scheme are described. The fiberoptic interferometer consists of two fibers; they are labeled the reference fiber and the sensing fiber. The reference fiber is arranged in a circular pattern, whereas the sensing fiber is arranged in an ‘S’ pattern. These fibers are exposed to the same strain field and each experiences a strain-induced phase shift. A difference in the phase shift between the two fibers indicates a change in strain. The strain-induced phase difference causes the interferometrically produced fringes to shift spatially. Analysis shows that the number of fringes passing an arbitrary point on a screen (the detection point) is linearly related to the strain in the fiber. In this analysis, the strain sensor is assumed to be perfectly bonded so that the fibers experience the same strain field as the specimen. It is further assumed that the sensor covers a sufficiently small area so that the strain can be considered constant over the entire strain sensor. Also, the phase change produced by transverse strain components (with respect to the fiber) induced by the specimen is assumed negligible compared to the phase changes attributable to the axial strain components. A cantilever beam was used as a specimen. Experimentally determined strains correlated well with the strains predicted by beam theory. The fringe-detection scheme described is a high-speed fringe counter. The speed of this counter is necessary to detect vibrational phase noise which is invisible to the human eye. Two photodiodes detect the fringes, and a logic circuit counts the fringe shifts, both strain and noise induced. Since noise is random in nature, it can be averaged out. This fringe detector exhibits good sensitivity and is the key to moving the sensor from the laboratory to the field.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...