Stainless Steel Products Presents

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Stainless Steel Products Presents
FATIGUE LIFE IMPROVEMENTS OF GROUND
SURFACES BY WIRE BRUSHING
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Grinding of Surfaces Causes Microchip Buildup

• Surface Burning
• Material Redeposition
• Surface Subsurface Cracking
• Mechanical Metallurgical Transformation
• Surface Tensile Residual Stresses

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Remedies to Minimize the Effects of Grinding and
Improve Compressive Residual Stresses

• Fine Grinding
• Low Work Speeds
• Small Cut Depths
• CBN or Diamond Grit

• Polishing
• Shot Peening
• Ball Burnishing
• Surface Coating/Nitriding

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Wire Brushing

• Fast and Easy
• A Low Cost Alternative
• Common for On-Line Polishing/Deburring
• Good for Complex Geometries
• Induces Hardening and Compressive Residual
  Stresses

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Purpose of Experiments

• Measure Fatigue Life Enhancements on Stainless
  Steel Ground Surfaces Using Wire Brushing
• o Optimized Brushing Conditions criteria
  related to
• gt Residual Stresses
• gt Work Hardening
• gt Surface Roughness
• gt Burr Formation
• Investigate mechanisms of fatigue crack
  initiation and propagation
• Establish the role of work hardening and residual
  stress on fatigue crack growth

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Experimental Procedures

• Material 304 Stainless Steel
• Ground Surface V shaped notched bar
• Only the Notch was Ground or Brushed
• Test Surfaces characterized by measuring
  roughness
• Hardening characterized by microhardness
  measurements
• Residual Stresses were evaluated using X-Ray
  methods
• High Cycle Fatigue Tests used a 3 point bend
  geometry
• Other effects measured include surface finish,
  and surface temperature

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Optimized Brushing Conditions

• S2 took 14 seconds
• S4 took 12 seconds

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Surface Preparation and Effects on Surface Quality
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Electron Microscopy
Ground Surface 1000x
Brushed Surface 2000x
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Work Hardening Residual Stresses
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Fatigue Behavior
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Summary of Wire Brushing Benefits

• Relatively Inexpensive and Simple Process
• Fatigue Life Improvements resulting from
• o Peak valley reductions on ground surfaces
  resulting in
• fewer potential sites for fatigue crack
  initiation
• Work Hardening Effects resulting from
• o Higher surface hardening and deeper work
  hardened layer
• Eliminates Thermal Micro cracks by
• o Removing the thermally effected layer induced
  by grinding
• Results in Higher Compressive Residual Stresses
  by
• o Generating higher micro geometrical qualities
  and hardness
• Higher Geometrical Qualities vs. Shotpeening with
  Similar Compressive Residual Stresses

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References

• Presented by Ralph Rosenbaum
• Stainless Steel Products
• 561-T Acorn Street, Deer Park, NY 11729
• Phone [phone]
• Fax [phone]
• E-mail Ralph_at_STAINLESSWIRES.COM
• Article By Nabil Ben Fredj, Mohamed Ben Nasr,
  Amir Ben Rhouma, Chedly Braham, and Habib
  Sidhom, Fatigue Life Improvements of the AISI
  304 Stainless Steel Ground Surfaces by Wire
  Brushing, ASM International 1059-9495, December
  21, 2003, p 564-574
• Article Web link http//www.springerlink.com/con
  tent/b824020760543lg0/