Transverse Mechanical Anisotropy in Hot Consolidated Enclosure Steels
Transverse mechanical anisotropy in consolidated enclosure steels reduces transverse bend angles and impact energy, demanding transverse-orientated batch testing.
R-Value
Meaning
Mechanical property parameters derived from uniaxial tensile testing quantify the resistance of sheet metal to thinning during plastic press deformation. The metric designated as r-value, or plastic strain ratio, measures the ratio of true plastic width strain to true plastic thickness strain in a sheet specimen pulled in tension. High values indicate that sheet metal resists thickness reduction and draws material from the width plane during deep drawing operations.
Stamping suppliers evaluate r-value measurements to predict drawability and avoid localized necking when manufacturing deep-drawn battery cell cans and structural cover panels.
Calculation Method
Specimen preparation and strain measurement follow standardized protocols specified in ASTM E517 or ISO 10113. Tensile tests pull rectangular specimens to specified plastic strain levels below uniform elongation, typically between ten and twenty percent strain. Optical or mechanical extensometers measure concurrent longitudinal and transverse dimensional changes to calculate width and thickness strain values.
The mathematical calculation of r-value divides true width strain by true thickness strain, reflecting crystallographic texture developed during cold rolling and annealing.
Directional Variation
Sheet metals display varying strain ratios depending on specimen orientation relative to the rolling direction. Tensile specimens cut at zero, forty-five, and ninety degrees yield distinct planar values. Averaging these values generates the mean plastic strain ratio, which characterizes overall deep drawability across the entire sheet surface.
Deep Drawing
Manufacturing deep cylindrical battery cans requires high metal flow without wall thinning or tearing. Materials possessing high average r-value maintain wall thickness under heavy draw ratios, preventing cup bottom fracturing during multi-stage press sequences.