Summary
The optical method of reflected caustics was applied to beam buckling problems. The reflected rays of a light beam (either parallel, or convergent, or divergent) on the flanks of the strut create caustics which consist of two strongly illuminated straight lines, confining the luminous region of the strut. By measuring the distance between the extremities of the caustics, the perturbation parameters of the buckled beam can be defined. The accurate experimental evaluation ofs allows the solution of the respective Euler expansion equations for the critical buckling load and its higher order terms in the post-buckling state of the strut. The method is a versatile and sensitive technique for experimentally defining the mode of elastic buckling of struts and can be extended to study plastic buckling cases.
Übersicht
Die Methode reflektierender Kaustiken wurde auf Stabknick probleme angewendet. Die von der Oberfläche des Stabes reflektierten Lichtstrahlen (parallel, konvergent oder divergent) erzeugen Kaustiken, die aus zwei stark leuchtenden geraden Linien bestehen, die den leuchtenden Bereich des Stabes begrenzen. Durch Messung des Abstands zwischen den Grenzen der Kaustiken kann der Störparameters des geknickten Stabes bestimmt werden. Eine genaue experimentelle Ermittlung vons ermöglicht die Lösung der nachs entwickelten Eulerschen Gleichungen für die kritische Knicklast und der Terme höherer Ordnung im Nachknickzustand. Die Methode ist eine vielseitige und sensitive Technik, um experimentell die elastische Knickform von Stäben zu bestimmen; sie kann auf das plastische Knicken ausgedehnt werden.
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Theocaris, P.S., Lazopoulos, C. Evaluation of the perturbation parameters in buckled rectangular pin-ended Euler struts by caustics. Arch. Appl. Mech. 62, 83–90 (1992). https://doi.org/10.1007/BF00808731
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DOI: https://doi.org/10.1007/BF00808731