Strength testing is a large part of friction welding quality control because many OEMs have specifications to meet for the required strength to ensure maximum performance of the component. To validate optimal friction welding parameters and evaluate the durability of the welded materials, you use the bend test. Bend tests are quite straight forward, the most common application of the bend test is to check quality and purpose during friction welding. This process is not very time consuming, and you can test the component nearly anywhere.
After welding the two materials from the friction welding process, remove a strap from the center of the cross sectioned metal from the welded portion. You need to cut the strap flat. Now bend the strap in a L shape. The stretch on the material will be outside; however, the compression of the material will be inside. Even though the bend test method might look simple, there are various complications that even good friction welders sometimes fail to perform the procedure properly.
However, the bend test does not show a quantitative bond from the friction welding, but people associate this method with Tension testing – tensile, yield, and elongation strength test. This method will demonstrate the overall ductility and quality of the weld as it compares to the lessor material. The reason to stretch the test coupon is to stretch the outer surface and challenge the limit of the bond. This stretch also approximates the elongation to the minimum percentage in the tensile test.
In other words, you apply force on the midpoint of a bend test or pull from ends of a tension test of the welded materials. This will create a uniform stretch, and the stress begins at the bending point or at the weakest of the two materials. The intensity of bending and stretching depends on the materials you bind with friction welding. For instance, if you test material with a weak bond, it breaks into two pieces when you try to bend it into a L shape or shears cleanly at the weld union when you stretch it.
Another name for bend testing is transverse beam testing or flexure testing. This method measures how the material reacts after bending and increasing flexibility. It checks the bond between the materials. This method does not require high equipment or space. You can even perform this method in a small store.