TH74992A - How to slit the fatigue-resistant sheet and the resulting sheet. - Google Patents

Abstract

A DC60 sheet material (111) has a bending aid structure (113) which is designed and positioned to bend along the bending path (115). The bending aid structure (113) has curved vertices (122) that extend from opposite ends (121) back along the bending aid structure (113) to another vertice (122), and each vertice (122) has a length and radius of curvature that minimizes the stress density. Ideally, the length of the curved vertices (122) is more than twice the thickness. The lateral distance LD, from which the bending support structure (113) in the sheet material is placed away from the bending line (115), is minimized by an arc of small radius (125) connecting the vertex (122) to the rest of the bending support structure (113). The method of constructing the structure (131) from the sheet material (111) to resist the loads acting in a circular fashion is also revealed, as is the method of increasing the fatigue strength of the structure (131), which is constructed by bending the sheet material (111) along the bending line (115) where there is more than one bending support structure (113). The sheet material (111) with the bending support structure (113) is laid and positioned. To allow bending along the bending line (115), the bending aid structure (113) has curved vertices (122) extending from the opposite ends (121) back along the bending aid structure (113) to another vertice (122), and each vertice (122) has a length and radius of arc that minimizes the stress density. Ideally, the length of the curved vertices (122) should be more than twice the thickness. Ideally, the lateral distance LD which the bending aid structure (113) in the sheet is provided from the bending line (115) is minimized by a small radius arc (125) connecting the vertices (122) to the rest of the bending aid structure (113). The method of constructing the structure (131) from the sheet (111) to resist the circular load is also revealed. Likewise, a method to increase the fatigue strength of a structure (131) is performed by bending a sheet of material (111) along a bending line (115) which has more than one bending aid structure (113).

Claims (32)

1. A sheet of material fabricated to bend along a given direction, consisting of more than one set of bending structures arranged and positioned to bend along the given direction. At least one of these bending structures has curved folds extending from opposite ends of the bending structure and curving back along the bending structure to another fold. Each of these folds is arranged to greatly reduce the stress density resulting from forces acting perpendicular to the bending direction. 2. A sheet of material as defined in Claim 1, where the bending structure is one or more of the following: slits, grooves, or notches. 3. A sheet of material as defined in Claim 2, where the curved return section bends away from the line of bending near the opposite end and bends back to the line of bending at the far end of the return section. 4. A sheet of material as defined in Claim 3, where the curved bend has a length in the direction of bending of at least twice the thickness of the sheet of material. 5. A sheet of material as defined in Claim 3, where each curved bend section has a length in the bending direction of at least approximately 20 percent of the total length of the bending support structure. 6. A sheet of material as defined in Claim 4, where the curved section has a radius of curvature along the length of most of it which is at least twice the thickness of the sheet of material. 7. A sheet of material as defined in Claim 4, where the curved section has a radius of curvature along the length of most of it which is at least 3 times the thickness of the sheet of material. 8. A sheet of material as defined in Claim 2, where the bending structure is a curve whose convex side faces inward and extends along the bend, and the opposite ends of the curve are re-entry along the curve with a radius of curvature between approximately 0.1 and approximately 1.0 times the thickness of the sheet. 9. Sheet material as defined in Claim 2, where the transverse dimension of the bending support structure from the bending line is less than approximately 20 percent of the total length of such bending support structure. 10. A sheet of material as defined in Reputation 2, whereby the bending support structure is made up of more than one connected curved section which is symmetrical along the transverse centerline of the bending support structure in a manner perpendicular to the bending line and the opposite ends of the bending support structure have a radius of curvature less than the radius of curvature of the bend. 11. A sheet of material as defined in Claim 10, where the radius of curvature of the bend is at least approximately 5 times the radius of curvature of the opposite ends of the bending structure. 12. A sheet of material as defined in Claim 2, where each arc has a length between approximately 2 and approximately 4 times the memory size of the sheet and an arc radius between approximately 2 and approximately 4 times the thickness of the sheet. 13. A sheet of material as defined in Claim 12, where each end has a radius of curvature approximately not exceeding the thickness of the sheet. 14. A sheet of material as defined in Claim 4, where the bending area is structured and positioned so that the edge fits into the surface of the sheet of material on the opposite side of the bending structure during bending. 15. A sheet of material designed to bend along a bending line consists of beveled grooves positioned in an alternating, longitudinal pattern on the alternating sides of the bending line. These grooves are structured to ensure edge-to-surface contact on opposite sides of the grooves during bending. Each groove is curved, with the convex side closest to the bending line. A curved fold extends from the opposite side of the groove to another fold, and this fold has a length and radius that minimizes stress density. 16. A sheet of material as defined in Claim 15, where the curved rebound has chords that are directed parallel to the direction of bending. 17. A sheet of material as defined in Claim 16, where the radius of curvature of the curved return section is at least approximately twice the thickness of the sheet of material. 18. A sheet of material as defined in Claim 17, where the radius of curvature of the return section is between approximately 2 and approximately 4 times the thickness of the sheet of material. 19. A sheet of material as defined in Claim 15, where such sheet of material is bent along the bending direction. 20. A sheet of material as defined in Claim 19, whereby the sheet is bent along the bending direction to form a three-dimensional structure suitable for the application of forces perpendicular to that bending direction. 21. Method for increasing fatigue resistance of structures fabricated by bending: A sheet of material is constructed using more than one bending aid structure, positioned and arranged to facilitate bending. This method involves the following steps: The bending aid structure extends along the bend, with curved folds extending away from opposite ends of the aid structure and looping back along the bend to another fold. The length and radius of these folds are chosen to be large enough to significantly reduce stress density and greatly increase fatigue resistance when subjected to circular loads perpendicular to the bending direction. 22. The method as defined in Claim 21, whereby the procedure for creating a bending structure to achieve a curved bend is accomplished by creating a curved bend with a radius of curvature between approximately 2 and approximately 4 times the thickness of the sheet material. 23. The method as defined in claim 22, whereby during the fabrication process a structure is created that facilitates bending into one of the following incisions, grooves, or notches in the sheet material. 24. The method as defined in claim 23, whereby during the fabrication process a bending structure is formed to create a form that allows the edges to fit onto the opposite side of the bending structure during bending. 25. The method for preparing sheet material for bending into a three-dimensional structure along the bending direction and the subsequent application of forces to the structure in the direction perpendicular to the bending direction consists of the following steps: Preparing more than one set of bending aids along the bending direction. These bending aids are at least one notch, groove, or serration in the sheet material, positioned near the bending direction. During this preparation step, bending aids are constructed with elongated sections extending from opposite ends of the bending aids, away from the bending direction and curving back along the bending aids to another elongated section. Each elongated section has a sufficient length along the bending direction to significantly increase fatigue resistance when the structure is subjected to transverse forces. 26. The method as defined in Claim 25, whereby during the fabrication process, a curved inversion is formed with chords that are primarily parallel to the direction of bending. 27. The method as defined in claim 26, whereby during the fabrication process a curved return section is formed with a radius of curvature of at least approximately twice the thickness of the sheet material. 28. The methods as defined in Article 27 and the procedures for bending the sheet material into a three-dimensional structure after the fabrication process. 29. The method as defined in Reputation 28 and the procedure for applying forces to the three-dimensional structure in a direction perpendicular to the bending direction after the bending procedure. 30. Method of fabricating a structure from sheet material to resist applied weight in a circular manner, consisting of the following steps: Creating a structure in the sheet material with more than one bending point, positioned and defined along the bending line to ensure the sheet material bends along that line. Bending the sheet material along the bending line to create a three-dimensional structure. During the fabrication process, curved incisions are made at each bending point, with opposite ends curving away from the bending line and curved sections extending from the opposite ends. Pressure is applied, and the curve returns along these incisions to another curved section, with the far end of the curve returning to the bending line. 31. The method as defined in Reputation 30 and the procedure for applying forces to the bent structure in a circular motion perpendicular to the bending direction after the bending procedure. 32. The procedure as defined in Reputation 31, whereby the procedure for constructing each bending aid is performed by creating a curved vertex of chord length that extends along the bend with a length of at least approximately 20 percent of the length of the bending aid along that bend.