Selecting the right materials for roll forming—Part 1
To manufacture the right product at the right price, roll formers must have the right material. Selecting the best material for a job is an important and difficult task. The designer or material specifier must take a number of factors into consideration.
This article presents some information about general and specific metal characteristics to assist roll formers in choosing the right metal.
 |
| Figure 1: To eliminate the influence of the specimen size, the test load is divided by the area of the original specimen cross section. The load and the corresponding elongations can be measured and plotted in diagrams. |
Mechanical Properties
To safely withstand the expected maximum load without permanent deformation (and/or to stay within the specified deflection) is a basic requirement for any product. The resistance against the load is a function of the cross section and the mechanical properties (or strength) of the material.
The most important mechanical properties are yield strength, tensile strength, and elongation. These properties are established by testing. Tension is applied to materials to test their mechanical properties. The test specimens are cut and machined out from the material to be tested. After their cross sections are measured, the specimens are placed between the jaws of a testing machine. The gradually increasing load and the elongation are then checked.
To eliminate the influence of the specimen size, the test load is divided by the area of the original specimen cross section. The load divided by the area is the stress. For example, a 2,000-pound load on a test specimen with a cross section of 0.1 square inch will create a stress of 20,000 pounds per square inch (2,000 ÷ 0.1 = 20,000). The load and the corresponding elongations can be measured and plotted in diagrams (see Figure 1). In many cases, the yield limit is clearly recognizable on the graphs.
