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Bobcat Company

Using nCode to Perform Vibration Fatigue Analysis of a Cooling Fan Mount

About this user story

Summary:

A cooling fan mount was failing during the field validation process despite high measured fatigue life values. The ultimate root cause was high residual stress from the assembly procedure. This presentation illustrates Bobcat's integration of nCode GlyphWorks and nCode DesignLife.

nCode GlyphWorks was used to process the field data to extract two possible load cases. nCode DesignLife was used to identify the more probably load case and also shows the effects of the mean stress. nCode DesignLife was used to help set up a lab vibration test to validate the new design. Results from nCode DesignLife and nCode GlyphWorks were compared with the fatigue failures produced by the lab test.

Presenter: Patrick Stahl, Bobcat Company

Originally presented on May 15, 2014 at the 2014 HBM-nCode Products User Group Meeting in Livonia, Michigan (USA).


Using GlyphWorks for Data Analysis and Damage Editing

About this user story

Summary:
Bobcat Company uses nCode GlyphWorks to address challenges in order to develop lab tests based on drive motor torque as measured by strain gauged axles.

Abstract:
Time compression of field duty cycles to create laboratory fatigue loads is generally done using data from strain gages. This project involved creation of a time compressed lab fatigue test that used measured axle torque as opposed to measured strain. This involved converting the torque to stress. It was not stress at a specific location; instead torque was multiplied by an arbitrary value to make stress magnitudes of the data traces fit into the classical fatigue region of a modified BS5400 ClassF SN curve.

The front and rear axles of the skid loader are chain driven by the same drive motor, so the data traces had to be analyzed together to ensure that when if one axle was seeing high torque, and the other was not (as is typical), this data was retained and kept in phase. These data traces were then processed with Stress Life and Damage Editing Glyphs to reduce the data trace to only damaging events. This process was iterated to determine effects of Low Pass filter settings, along with the settings of the Damage Editing glyphs' slice selection settings to produce an output data trace that retained 90% of the original damage, while taking into account the effects of filtering the data in order to play the output file in the test rig (test rig only capable of reproducing frequencies up to ~9 Hz). The final settings were then used to process all required field duty cycles, and these traces were concatenated and played out in the test rig using RPC. The final optimized output file retained 90% of damage and had an AF=12.

Presenter: Scott Berndt, Bobcat Company

Originally presented on May 15, 2014 at the 2014 HBM-nCode Products User Group Meeting in Livonia, Michigan (USA).

The Customer

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