ISO 7438

The standard covers a method to determine the ability of metallic materials to undergo plastic deformation in bending, by using different bending devices. One of the more common bending device uses two supports and a former in a 3-point setup.

 

The bend test is performed by placing a test piece with either a rectangular, square, round, or polygonal cross-section symmetrically on the support fixture that is mounted to the testing machine. The load is applied to the specimen at mid-span until the predefined angle of bend is achieved. The angle of bend is determined from the measurement of the displacement of the former. The interpretation of the test results should be in accordance to the requirements of the product standards or if not specified, it should be confirmed that no visible macro-cracks are present.

 

Please refer to the standard for more detailed information about the other test setups; bending device with a V-block and a former, and bending device with a clamp.

 

Solutions for ISO 7438 with a 3-point bend setup typically include these types of components:

 

MTS offers electromechanical Criterion® and Exceed® universal test systems and dynamic servohydraulic Landmark® test systems that are ideal for performing accurate and repeatable monotonic bend testing of metallic materials per ISO 7438.

MTS Criterion universal testing systems are engineered to support the needs of advanced Research & Development. MTS Exceed universal testing systems are best suited for Quality Control testing by delivering the reliable performance needed to meet the uptime demands of high-volume production environments. Due to the large variety of metals and specimen dimensions that can be tested per ISO 7438, the required force capacities can differ significantly. MTS offers frame models that address the smaller force requirements for testing thin-sheet specimens up to high-force requirements for testing solid cylindric specimens with a large diameter.

The MTS Criterion and the MTS Exceed universal testing machines range from tabletop to floor-standing electromechanical models with force ratings of up to 600 kN / 135 kip. Many of the models have dual-zone test spaces to reduce set-up times if you frequently change test requirements.

The MTS Landmark dynamic servohydraulic test system with its superior stiffness and alignment capabilities, is an ideal choice if additional fatigue and fracture testing capabilities are required. Systems are available in highly configurable floor-standing and tabletop models with force ratings from 5 kN / 1 kip to 500 kN / 110 kip.

As an alternative to a new load frame, you can replace outdated controls / hydraulics of existing MTS or another manufacturer’s electromechanical, servohydraulic or custom test systems, including: **Instron®, **Zwick®, **Tinius Olsen™, **SATEC®, **Baldwin® and more with an MTS ReNew™ Upgrade.

**Trademark owned by their respective owners, not affiliated with MTS Systems Corporation.

 

 

The lower support span and the radius of the supports and loading nose are generally selected based on the material and specimen type to be tested. Applicable product specifications define the distance between the supports and radius requirements as related to the specimen thickness to be tested. For example, a hot rolled mild steel sheet or soft aluminum might require only a radius of 1.5 to 3 times the thickness, but high strength steel or hard aluminum alloys with low ductility can require a radius as large as 5 to 8 times the thickness.