Application Note: XRD on Cranks for Grinding Stress

The problem: Metallic components which are machined may be subject to abusive heat and work during the machining process.

During the setup of a new machining process, it is necessary to establish that machining parameters are optimized for surface finish, cycle time, and tool wear while keeping the work piece free of unfavorable stresses. In this application, the grinding of a crankshaft journal was checked for unfavorable stresses due to overheating during grinding, also known as grinding burn.

The testing method: residual stress depth profile with X-ray diffraction

A pin journal was sectioned from the crankshaft and trimmed for physical access at the desired measurement locations to allow for measurement of a residual stress depth profile with X-ray diffraction.

Once the sample was fixtured, measurements were performed in 2 directions (axial and hoop). Material was removed electrochemically and the depth was verified using a dial gauge. The process was repeated for each of the prescribed depths until the full residual stress depth profile was acquired.

Crankshaft journal where residual stresses were determined with X-ray diffraction method — Figure 1 – Photo of measured crankshaft journal

The Results

Figure 2 – Plot showing the residual stress versus depth for Pin 6

Instrument used in this application: Xstress G2R with electropolishing table

Xstress G2R

Stresstech’s Xstress G2R X-ray diffractometer represents advances in design and construction which provide enhanced reliability and function in a truly portable residual stress and retained austenite analyzer. Bi-axial and tri-axial stress state analysis is effortless and automated with rotating diffractometer.

Xstress Table for X-ray

The Xstress Table for X-ray complements the Xstress X-ray diffractometer. The Table for X-ray makes precise positioning of the samples possible for e.g. depth profile measurements. The measuring area is surrounded from all sides by a safety enclosure.