Determination of Perpendicular Anisotropy (r-value) According to DIN EN ISO 10113

The ISO 10113 test is intended for flat metal products such as thin sheets or strips—for example, made of steel or aluminum—for which anisotropic strain properties are critical. Typical fields of application include the automotive and automotive supply industries, mechanical engineering, and other sectors where sheet metal forming plays a role. Thin sheets are used in all branches of industry, which is why extensive material testing is required. The result (r-value) is used to optimize forming processes and for the acceptance testing of new material batches.

Test Method

The test is performed using a uniaxial metal tensile test, for example, in accordance with ISO 6892-1, using sheet metal specimens that are typically taken at various angles to the rolling direction. According to ISO 10113, the r-value is defined as the ratio of the true plastic width elongation to the true plastic change in thickness of the specimen. Since the change in thickness is difficult to measure, a constant volume is assumed up to the point of uniform elongation, and the change in length is determined instead as a substitute for the change in thickness.

The ISO 10113 standard distinguishes between three types of procedures:

• In the manual procedure, changes in width and length are determined using measuring probes or calipers
• In the semi-automatic procedure, only the change in length is determined using an extensometer
• In the automatic procedure, both quantities are recorded simultaneously using extensometers

Test Objectives

The perpendicular anisotropy parameter according to ISO 10113, or alternatively according to ASTM E517 or JIS Z2254, characterizes the anisotropic forming behavior of sheet metal. The r-value is one of the typical parameters in a tensile test, alongside the yield strength, tensile strength, and work hardening exponent. All values are used for material characterization and quality assurance. The r-value indicates the extent to which a specimen deforms in the transverse direction (width) compared to the change in thickness:

• r = 1 indicates isotropic behavior
• r > 1 indicates preferential deformation in the width direction (good deep-drawing properties)
• r < 1 indicates that thickness deformation predominates.

This allows, for example, for planning improvements in the deep-drawing process or identifying quality deviations in coil steel or aluminum sheet.

Testing machine and accessories for tests according to ISO 10113

• Universal testing machine (e.g., inspekt table 20 kN): The machines in the inspekt table series offer test forces up to 250 kN and are designed for tensile, compression, bending, and peel tests. Thanks to backlash-free ball screws and a brushless servo motor, precise and fast measurements are possible even in harsh environments. The machine can be equipped with various strain gauges and, like all our machines, comes standard with LabMaster testing software.
• Grips: Hegewald & Peschke offers a wide range of mechanical, pneumatic, and hydraulic grips for tensile tests. For sheet metal specimens, for example, wedge grips, screw type wedge action grips, or hydraulic grips are suitable. While wedge type grips represent a cost-effective option, hydraulic grips close parallel to the specimen without applying preload to the material and can be supplied in either a synchronous two-sided or a single-sided configuration. The latter allow for the clamping of symmetrical as well as asymmetrical specimens that are bonded, riveted, doweled, or welded. This functionality can also be achieved with screw type wedge action grips. These combine the properties of screw-type and wedge-type clamping devices, enabling them to automatically generate greater gripping forces as the test force increases and still securely clamp the specimen after fracture, which offers advantages for brittle fracture testing.
• Extensometers (strain measurement systems): Optical or mechanical extensometers can be used to simultaneously measure changes in length and width. H&P offers, for example, the MFX long-distance extensometer, which measures the specimen’s longitudinal elongation via contact. Transverse elongation is measured at one or two measurement points using a Clip-On MFQ extensometer or an automatic width-change transducer MFQ-B. This digital wide-range transverse strain gauge measures at two points to determine the r-value (perpendicular anisotropy) on thin sheets and can be used for specimen widths between 6 and 35 mm without any modifications. Low contact forces of the probe pins and a mounting system that sensitively adapts to the specimen allow even the thinnest sheets to be tested. Alternatively, an optical extensometer can be used. Hegewald offers two different devices for this purpose. The DeltaL combines the advantages of the ease of use of contact extensometers with those of optical measurement technology and operates non-contact. This allows even sensitive sheets to be tested at high sample throughput. The ONE video extensometer offers a more scientific approach and allows for the determination of longitudinal and transverse strain distribution across the entire parallel length of the specimen. Likewise, 2-D maps can be generated using a DIC module.
• LabMaster Testing Software: LabMaster supports the automatic acquisition and evaluation of all relevant measurement parameters of a tensile test (force and strain) and uses them to calculate material properties such as the modulus of elasticity, Yield strength, elongation at fracture, and work hardening exponents according to ISO 10275 (n-value), etc. The calculation of the r-value according to ISO 10113 is implemented as standard. The testing software automatically records the perpendicular anisotropy value in the test report, allowing the material property to be directly evaluated and documented.

For further information on determining perpendicular anisotropy (r-value) in accordance with ISO 10113, please feel free to contact us.

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