A Look Ahead at Bar Fatigue in 2018

The SMDI Bar Steel Fatigue subcommittee is celebrating 20 years of working together to provide the industry with much needed fatigue data for critical applications. Past work includes the completion of over 200 iterations; 164 released to the public. This work continues in 2018 by working on four studies for key ground vehicle OEMs and suppliers that comprise the subcommittee. The subcommittee concentrates test efforts on those steel grades and process combinations used in safety critical components. Test plans for 2018 include:

  1. Completion of Phase XIII; rotating bending fatigue tests on both SAE 8620 and SAE 9310 steel. The tests results will be compared to previous axial fatigue results for the same steels.
  2. Completion of Phase XIV; SAE 9310 gas carburized to both shallow (5% of bar diameter) and deep (10% of bar diameter) case depths.
  3. Initiation of Phase XVI by testing a SAE 4120 steel modified to be vacuum carburized at high temperatures up to 1900 °F. The test results will be compared to previous iterations of the same grade (not modified) to determine if the high vacuum carburizing temperature and accelerated cycle time is an acceptable process alternative.
  4. Initiation of Phase XVII by testing SAE 8620 steel at elevated temperatures to determine long term durability within harsh environments such as engines and transmissions. The material will be tested at room temperature, 350 °F and 675 °F. The test results will be used to validate formulas currently used in the industry to estimate elevated temperature performance.

Further blog discussions on all of these test phases will be provided when the data becomes available to the public. If you are interested in these results earlier, committee membership is available (contact danderson@steel.org).

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