ISO 7799:1985 PDF

Overview

ISO 7799:1985 specifies the reverse bend test for metallic sheet and strip 3 mm thick or less. The standard defines a repeatable method to determine a material’s ability to undergo plastic deformation by repeatedly bending a rectangular test piece 90° in alternating directions over cylindrical supports of specified radius. It is applicable to metallic sheets and strips; application to aluminium and its alloys is allowed only after prior mutual agreement. ISO 7799 supersedes the earlier ISO/R 88-1959 (first edition 1985).

Key topics and requirements

• Scope: Sheet and strip of thickness ≤ 3 mm; aluminium/alloys only by agreement.
• Specimen: Rectangular test piece; thickness as taken from the product including mill skins; machined width normally 20–25 mm (narrower strips may be tested as supplied).
• Test principle: Repeated bending of the free end of a held specimen through 90° alternately in opposite directions, the bend wrapping over a cylindrical support.
• Supports and jaws:
  • Cylindrical supports and jaws must be sufficiently hard and wear resistant.
  • Axes of cylindrical supports must be perpendicular to the plane of bending and parallel to each other (within 0.1 mm).
  • Support apex position relative to jaws: distance y = 1.5 mm for r ≤ 25 mm; y = 3 mm for r > 25 mm.
  • Distance between top of supports and underside of guide (h) between 25 and 50 mm.
• Machine geometry: Pivot axis distance from support apex = 1.0 mm.
• Test conditions:
  • Temperature: ambient 10–35 °C; controlled tests at 23 ± 5 °C.
  • Bending speed: not to exceed one bend per second; reduce speed if heating affects results.
  • Continuous contact between specimen and supports should be maintained; an optional tensile load up to 2% of nominal tensile strength may be applied if specified.
• End criteria and reporting:
  • Repeat bends until the number specified in product standard or until a visible crack appears (without magnification).
  • The bend that causes rupture is not counted in the reported number of bends.
  • Test report must include reference to ISO 7799, specimen ID and dimensions, test conditions (support radius, h, applied load), end criterion, and results.

Applications

• Assessing ductility and resistance to alternating bending for thin metallic sheets and strips.
• Quality control and acceptance testing in metal producing and processing industries.
• Material selection for forming, stamping, or cyclic bending applications.
• Use by metallurgists, test laboratories, quality engineers, product specifiers, and standards bodies.

Related standards

• Developed by ISO/TC 164 (Mechanical testing of metals).
• ISO 7799 replaces ISO/R 88-1959.