- "Mergler, Harry W." (x)
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Show moreThe invention relates to improvements in methods and apparatus for bending beams or like objects to a desired profile. Description of the prior articles: Among the various fields of use, the invention has application in the bending of ship beams or rib frame members from straight mill products to prescribed profiles. Alternatively, the invention may be used to straighten distorted beams or other elongated members. In prior techniques, a beam is usually bent in a three-point loading system where the beam is laterally supported by a pair of spaced elements while an opposed third ram element advances laterally against the beam midway between the spaced support elements until the beam is plastically bent to a desired angle. Inherent in this widely used approach is the introduction of transverse loading or shear throughout the stressed zone of the beam between the spaced support elements. The transverse loading may develop a permanent twist in a beam of nonsymmetrical cross section, which is objectionable for numerous reasons. Twisting of an otherwise plane beam profile makes handling, supporting, and measurement of the beam during bending operations difficult. Further, beams twisted out of plane are not readily stacked for storage or transport and, more critically, are difficult to properly align during their fabrication into a hull assembly. Another result of the stress distribution in a three-point loading system is a nonuniform bending moment in the work area of the beam between the support elements which reaches a maximum at the center ram. Under this condition, the beam yields principally at the ram and develops what is termed a plastic hinge where excessive strains are produced in a limited area. This local type of permanent deformation is generally characterized by unpredictable material behavior in terms of the relationship between load and deformation and in terms of spring-back. The resulting curvature produced in the work area of the beam is nonuniform along its length and may be visualized as a central, sharply curved area of relatively small radius and adjacent, relatively straight areas. This kinked shape is not readily superposed with a smoothly curved profile. Thus, where a beam is successively bent along its length to conform to a given profile, substantial compromise must be made with deviations from the profile, and/or smaller and more frequent bends must be made. A problem commonly occurs with the bending of beams of nonsymmetric cross section where the lack of geometrical balance about the desired bending plane requires, for force equilibrium conditions, a bending moment or component perpendicular to the principal applied moment to maintain the beam in a plane. Typically in commercial practice, either this requirement is ignored or the beam is restrained from bending out of the principal plane by a rigid constraint during bending operations.
http://www.google.com/patents?vid=USPAT3952572
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