Understanding Size Effects and Forming Limits in the Micro-Stamping of Industrial Stainless Steel Foils

This study investigates the effect of grain size and composition on the material properties and forming limits of commercially supplied stainless steel foil for bipolar plate manufacture via tensile, stretch forming and micro-stamping trials. It is shown that in commercially supplied stainless steel the grain size can vary significantly and that ‘size effects’ can be influenced by prior steel processing and composition effects. While the forming limits in micro-stamping appear to be directly linked to the plane strain forming limits of the individual stainless steel alloys, there was a clear effect of the tensile anisotropy. In contrast to previous studies, forming severity and the likelihood of material failure did not increase with a decreasing channel profile radius. This was related to inaccuracies of the forming tool profile shape.

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Modeling of Size Effects on the Flow Stress of Type 304 Stainless Steel and Application in Coining Process

Volume 13: Processing and Engineering Applications of Novel Materials ◽

10.1115/imece2007-41971 ◽

2007 ◽

Author(s):

Gap-Yong Kim ◽

Muammer Koc ◽

Jun Ni

Keyword(s):

Grain Size ◽

Stainless Steel ◽

Flow Stress ◽

Size Effect ◽

Size Effects ◽

Specimen Size ◽

304 Stainless Steel ◽

Length Scales ◽

Type 304 ◽

Type 304 Stainless Steel

Application of microforming in various research areas has received much attention due to the increased demand for miniature metallic parts that require mass production. For the accurate analysis and design of microforming process, proper modeling of material behavior at the micro/meso-scale is necessary by considering the size effects. Two size effects are known to exist in metallic materials. One is the “grain size” effect, and the other is the “feature/specimen size” effect. This study investigated the “feature/specimen size” effect and introduced a scaling model which combined both feature/specimen and grain size effects. Predicted size effects were compared with experiments obtained from previous research and showed a very good agreement. The model was also applied to forming of micro-features by coining. A flow stress model for Type 304 stainless steel taking into consideration the effect of the grain and feature size was developed and implemented into a finite element simulation tool for an accurate numerical analysis. The scaling model offered a simple way to model the size effect down to length scales of a couple of grains and extended the use of continuum plasticity theories to micro/meso-length scales.

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Modified Monkman–Grant relationship for austenitic stainless steel foils

Journal of Nuclear Materials ◽

10.1016/j.jnucmat.2012.08.048 ◽

2013 ◽

Vol 433 (1-3) ◽

pp. 74-79 ◽

Cited By ~ 12

Author(s):

Hassan Osman Ali ◽

Mohd Nasir Tamin

Keyword(s):

Stainless Steel ◽

Austenitic Stainless Steel ◽

Stainless Steel Foils ◽

Steel Foils

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Amorphous Silicon TFTs on Steel-Foil Substrates

MRS Proceedings ◽

10.1557/proc-424-65 ◽

1996 ◽

Vol 424 ◽

Cited By ~ 10

Author(s):

S. D. Theiss ◽

S. Wagner

Keyword(s):

Stainless Steel ◽

Leakage Currents ◽

Action Current ◽

Insulating Layer ◽

Stainless Steel Foil ◽

Current Voltage ◽

Stainless Steel Foils ◽

Steel Foils ◽

Current Behavior

AbstractWe describe the successful fabrication of device-quality a-Si:H thin-film transistors (TFTs) on stainless-steel foil substrates. These TFTs demonstrate that transistor circuits can be made on a flexible, non-breakable substrate. Such circuits could be used in reflective or emissive displays, and in other applications that require rugged macroelectronic circuits.Two inverted TFT structures have been made, using 200 gim thick stainless steel foils with polished surfaces. In the first structure we used the substrate as the gate and utilized a homemade mask set with very large feature sizes: L = 45 μm; W = 2.5 mm. The second, inverted staggered, structure used a 9500 Å a-SiNx:H passivating/insulating layer deposited on the steel to enable the use of isolated gates. For this structure we used a mask set which is composed of TFTs with much smaller feature sizes. Both TFT structures exhibit transistor action. Current-voltage characterization of the TFTs with the inverted staggered structure shows typical on/off current ratios of 107, leakage currents on the order of 10-12 A, good linear and saturation current behavior, and channel mobilities of 0.5 cm2/V·sec. These characteristics clearly identify the TFTs grown on stainless steel foil as being of device quality.

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