Knowing the formability of metals is absolutely critical in the manufacture and development of automobiles, typical performance indicators for the formability properties are the plastic strain ratio (r-value) and strain hardening exponent (n-value). Bend testing is also vital in drawing conclusions about the forming behavior and the susceptibility to failure of metallic materials during the forming processes dominated by bending deformation but also during crash deformation.
There are many factors that can affect the results of a test, it is important that these are minimized where possible to ensure accurate and comparable results. For requirements such as a hemming bend, the bending fixture needs to have high stiffness and be strongly secured to minimize the effect of the side load applied during bending.
Using Instron’s bend fixtures that include specimen stops which will ensure accurate and repeatable placement of specimens before starting testing. During testing, the high stiffness fixture experiences little movement as high side loads increase when the compressive load is distributed to the bending rollers. Importantly, the rollers are designed to minimize the friction experienced between the roller and specimen during bending. Additionally, Instron's Custom Solutions Group can provide fixturing that will meet unique testing needs or standards required by some auto manufacturers.
Meeting Different Specifications
There are many different requirements and specifications for
bend testing from ASTM/ISO as well as individual automotive producers and
automotive groups such as VDA.
There are many different bending fixtures available to meet different requirements. With adjustable span and modular design, it is possible to configure correctly for all requirements. If more accurate displacement measurement is required, LVDT's or extensometers can be easily secured to bending fixtures and automatically integrate with Bluehill® Universal.