Grain Direction Aluminum Sheet

Two rollers compressing the hot metal cause the polycrystalline material to elongate in the direction of rolling.

Grain direction aluminum sheet.

Once the crystallites are elongated they appear as the grain that we see in cold rolled steel. You must pay careful attention to grain or rolling direction when bending high strength metals especially when trying to achieve a small inside bend radius. From the flat pattern properties we can select a new edge for the grain direction. That has negligible impact on part strength.

Applying this to metal bending be it plate bending press braking or any other type of metal forming consideration must be given to the grain direction before any process is carried out. A plate s grains run parallel to the rolling direction. Aluminum plate thickness gt 250 inch has three grain orientations each with their own strength values. From mil hdbk 5 7075 t62 2 501 3 000 thick stock ultimate tension allowable stress is l 67 ksi lt 70 ksi and st 66 ksi.

When sheetmetal is bend perpendicular to rolling direction grain rearranges. Whereas bending parallel to rolling direction can lead to cracks because of destruction in grain structure. You can define a grain direction to use when calculating the bounding box for sheet metal parts. Bending with the grain gives a different result than bending against it.

During sheet metal processing rolling operation material grains are arranged in the direction of rolling. Bending metal against the grain or perpendicular to the grain is a common way to prevent material failure or cracking. The long tranverse lt the short transverse st and the longitudinal l. The grain direction is established during the metal rolling process.

When working with aluminum plate for example you need to pay close attention to whether you are forming with longitudinal or across transverse the grain direction. The grain direction is in the rolling direction of the sheet as it was being manufactured. As a general rule the grain line must run perpendicular to the bend to avoid the potential for cracking or fracture. By default in my testing the bounding box aligns itself with the longest straight side.

The software determines the smallest rectangle bounding box that aligns with the grain direction to fit the flat pattern.