ISO 10113:2020 𝒓-Value Determination

User Benefits

- Determination of reliable 𝑟-values contributes to improved precision of press forming simulation. - Related standards include ISO 10113, ASTM E517, GB/T 5027, IS 11999, and JIS Z2254. - The 𝑟-Value Measuring Device enables simultaneous determination of other tensile test properties as well as the 𝑟-value.

Introduction

Thin materials like high-tension steel have been gaining attention for aspects of fuel efficiency improvement by reducing body weight, especially in the transportation equipment industry. However, high-tension steel is prone to shape defects after press forming, posing a significant challenge in terms of time and cost required for the production of press molds. Recent advancements in Computer Aided Engineering (CAE) analysis techniques and computational speed of computers have enhanced high-precision simulation of press forming for high-tension steel. This enables prediction of the ideal shape of press-formed products, leading to substantial reduction of development time and cost for pressmolds. The realization of the high-precision press forming simulation requires reliable determination of the Lankford value, in short the 𝑟-value, one of the indicators representing the formability of sheetmetal. The 𝑟-value serves as a quantitative indicator of the ductility of a material in the thickness direction and corresponds to the material’s drawability, which contributes significantly to press formability. In ISO 10113, revised in 2020, three different 𝑟-value determination methods have been standardized (the manual method, the semi-automatic method, and the automatic method). The manual method does not require the use of extensometers for the gauge length and width, and the semi-automatic method employs only an extensometer for the gauge length. Both methods demand test force release after applying a certain plastic strain to the test piece. The automatic method, on the other hand, uses extensometers for the gauge length and width, enabling the 𝑟-value to be determined for any given plastic strain after completion of the standard metal tensile test in accordance with ISO 6892-1. Therefore, this method is very useful for determining other tensile property values (e.g., tensile strength) at the same time (see Appendix). This article introduces a case study of the 𝑟-value determination in accordance with the automatic method in ISO 10113 by using the AGX-V2 and the r ValueMeasuringDevice.

December 19, 2023 GMT