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Applications: Bent Beam

 
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Principle
   - make cut
   - measure surface
   - calculate stress
Validations
Applications
>    - bent beam
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Residual Stress
Conferences
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download preprint M. B. Prime, "Cross-Sectional Mapping of Residual Stresses by Measuring the Surface Contour After a Cut," Journal of Engineering Materials and Technology, 123, pp. 162-168, 2001. (LA-UR-00-205)

For more on this kind of known stress specimen, and x-ray and neutron results: download preprint M. B. Prime, P. Rangaswamy, M. R. Daymond, and T. G. Abeln, "Several Methods Applied to Measuring Residual Stress in a Known Specimen," Proc. SEM Spring Conf. on Experimental & Applied Mechanics, Houston, Texas, June 1-3, 1998, pp. 497-499. (LA-UR-98-0904)

Stress Map Measured Over Beam Cross-Section:
predicted stress map
Bend Test Prediction
measured stress map
Measurement Results
scale
Plot Scale

through-thickness stress plot

Results also plotted as through-thickness curve. Agreement with prediction is very good!
Details of this measurement and specimen:
Steel Beam
  • Austenitic stainless steel
  • 10 mm X 30 mm cross section
Bend to put in known residual stress
  • Bend in 4-point bending fixture.
  • Measure strain on top and bottom of beam during loading and unloading.
  • Calculate residual stress from strains and loads.
beam beding photo

Cut Beam using wire EDM
  • Beam carefully clamped during cutting.
  • Use 100 µm (0.004") diameter wire.
  • Cut using "skim cut settings" so that minimal stresses are put in during cutting.
EDM cutting photo

Measure Surface Contour with CMM
  • Use 4 mm diameter ruby tip
  • Measure 10 x 30 mm surface with a 50 x 300 grid of points.
Photo of CMM tip

Calculate Stress using FEM
  • Make 3-D model of beam after cut.
  • Apply opposite of measured contour as displacement boundary conditions.
  • Extract stresses normal to surface.
FEM mesh

 

 

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Operated by Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA
contact: Mike Prime at prime@lanl.gov | Copyright & Disclaimer
U.S. patent 6,470,756 | Last Modified: June 26, 2009

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