The development of a microscale strain measurement system applied to sheet bulge hydroforming

Emblom, William J.; Jones, Richard J.; Aithal, Mitra; Islam, Md. Farhan S. Ibne; Glass, Gary A.; Wagner, Scott W.

doi:10.1016/j.jmapro.2014.02.001

Cited by 9 publications

(11 citation statements)

References 4 publications

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“…Emblom et al 5 developed a microscale lithographic mask that was suitable for electrochemical etching. SU-8 is an epoxy-based negative photoresist manufactured by MicroChem.…”

Section: Microscale Strain Grid Marking Processmentioning

confidence: 99%

“…Additionally, p is the forming pressure, while s f and e f are the stress and strain at the pole of the bulge, respectively. The thickness strain and effective strain can be determined based upon equation 4and are seen in equation (5) e = e f = ln…”

Section: Introductionmentioning

confidence: 99%

“…Siegert and Wagner 7 reported an approach by Gologranc 8 for determining the flow stress while bulge testing and then summarized Panknin's 9 method for determining the thickness stress. Numerous other researchers have used Source: reproduced with permission from Elsevier, 2014, Emblom et al 5 hydroforming and viscous pressure bulge tests to determine the material properties of sheet metal as well. Kim et al 10 investigated annealing and grain-size effects with respect to bulge die diameters.…”

Section: Introductionmentioning

confidence: 99%

“…Finer grids (1-10 mm) have been produced but required using scanning electron microscopes (SEMs) to produce lithographic images with very small pitches and limited fields. 22 This research article evaluates microscale strain measurement during hydrostatic bulge testing using the strain grid marking process described by Emblom et al 5 A brief summary of the grid marking process is presented, followed by a description of the method used for strain measurement. The ''Results'' section presents an error analysis for undeformed grids as well as an error analysis for strains as a function of pressure for hydrostatic bulging dies with diameters of 11, 5, and 1 mm.…”

Section: Introductionmentioning

confidence: 99%

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A microstrain measurement methodology applied to multiscale hydroforming of annealed ASTM 304 stainless steel sheet

Emblom

Aithal

Jones

et al. 2015

The Journal of Strain Analysis for Engineering Design

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Meso-and microscale sheet metal forming represents new and attractive solutions to many manufacturing problems for product miniaturization. Larger organizations are utilizing commercially available microscale digital image correlation systems to measure the strains on these scales. The cost of these systems is preventing smaller research and development organizations from entering this challenging area or they are sacrificing the ability to determine strains and evaluate material behavior at the microscale. However, microscale strain grid measurement has the advantage over digital image correlation when the researchers wish to avoid polishing and etching the surface of the sheet metal to make the grain structure visible for digital image correlation and where tooling interferes with obtaining images of the workpiece in real time. This article evaluates the strain measurement and strains resulting from multiscale sheet metal hydroforming operations for annealed 0.2-mm-thick ASTM 304 stainless steel using a simple method for producing microscale grids that has been previously described. The gridding methodology was shown to be accurate with high repeatability. In addition, a strain grid measurement method using an optical microscope and digital camera is described and an error analysis was performed. Provided reasonable care is taken, the inherent error in undeformed parts is 0.76% of true strain for samples with 127 mm grids using the strain measurement system described. The maximum variation in the mesoscale and microscale strain measurement static bulge testing was 62.4% and more typically 61.3% of true strain. With care, the errors were reduced to less than 1% of strain. Microscale strains from sheet bulge hydroforming experiments for 11, 5, and 1 mm diameter dies are used to show that the strains measured are reasonable and consistent.

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“…Emblom et al 5 developed a microscale lithographic mask that was suitable for electrochemical etching. SU-8 is an epoxy-based negative photoresist manufactured by MicroChem.…”

Section: Microscale Strain Grid Marking Processmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A microstrain measurement methodology applied to multiscale hydroforming of annealed ASTM 304 stainless steel sheet

Emblom

Aithal

Jones

et al. 2015

The Journal of Strain Analysis for Engineering Design

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show abstract

“…Therefore, many researchers have developed automated dimension measurements to calculate strains. [11][12][13][14] Tan et al recorded two or more images with various angles and read the image coordinates automatically, thus calculating the spatial coordinates. 15 An algorithm of pattern recognition system for automatically constructing the FLC of sheet metal was also offered in the literature.…”

Section: Introductionmentioning

confidence: 99%

The verification of strains obtained by grid measurements using digital image processing for sheet metal formability

Yildiz

Yılmaz

2017

The Journal of Strain Analysis for Engineering Design

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Grid marking, which is applied before mechanical tests, is a crucial step in formability tests. In this study, four different grid marking methods, serigraphy, electro-chemical etching, photo-chemical etching, and laser marking techniques, were investigated for the stability of grids and their measurement accuracy. After examining the performance of the grid marking methods, laser marking has been selected to obtain grids on the surface of aluminum alloy parts. To evaluate the efficiency of the strains calculation using grids, tensile tests were conducted that considered different levels of elongation. A forming limit diagram of the 6061-T6 Al alloy was constructed to demonstrate the influence of possible measurement errors. Verification of grid strain evaluation revealed that the error in size measurements is dependent on overall strain values and reduced with increasing overall strain as expected. The maximum error of the implemented method does not exceed 1% when 9% of overall uniform elongation is reached. The approach used in the study provides sufficient accuracy for evaluating strains in principal axis of deformed circular grids with minimalized costs.

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Laser shock hydraulic forming for micro-bowl with miniature concave

Sun

Liu

et al. 2019

Int J Adv Manuf Technol

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The development of a microscale strain measurement system applied to sheet bulge hydroforming

Cited by 9 publications

References 4 publications

A microstrain measurement methodology applied to multiscale hydroforming of annealed ASTM 304 stainless steel sheet

A microstrain measurement methodology applied to multiscale hydroforming of annealed ASTM 304 stainless steel sheet

The verification of strains obtained by grid measurements using digital image processing for sheet metal formability

Laser shock hydraulic forming for micro-bowl with miniature concave

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