Grain Direction Aluminum Sheet

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.

Grain direction aluminum sheet.

The grain direction is in the rolling direction of the sheet as it was being manufactured. Once the crystallites are elongated they appear as the grain that we see in cold rolled steel. You ll now see that your flat pattern is generated based on one edge oriented parallel to the angled edge and the other obviously perpendicular to that in drawing the rectangle. The long tranverse lt the short transverse st and the longitudinal l.

By default in my testing the bounding box aligns itself with the longest straight side. You can define a grain direction to use when calculating the bounding box for sheet metal parts. 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.

The software determines the smallest rectangle bounding box that aligns with the grain direction to fit the flat pattern. A plate s grains run parallel to the rolling direction. The three orientations are. Bending with the grain or parallel to the grain direction can be a contributor to material failure as bending along the grain allows for separation of the grain boundaries.

That has negligible impact on part strength. The grain direction is established during the metal rolling process. Whereas bending parallel to rolling direction can lead to cracks because of destruction in grain structure. As a general rule the grain line must run perpendicular to the bend to avoid the potential for cracking or fracture.

Two rollers compressing the hot metal cause the polycrystalline material to elongate in the direction of rolling. 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. 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. Bending with the grain gives a different result than bending against it.

Bending metal against the grain or perpendicular to the grain is a common way to prevent material failure or cracking.