Application Note: A Correlation Between Barkhausen Noise and X-Ray Diffraction

In this application residual stresses on ground camshaft lobes were measured with Barkhausen noise and X-ray diffraction methods.

The problem: Near surface residual stresses on ground cam lobes

A manufacturer of camshafts needed to frequently verify the near surface residual stresses on ground cam lobes in a non-destructive manner.  Their only current means of achieving this was in a less frequent and destructive manner using X-Ray Diffraction.

The testing method: A Correlation Between Barkhausen Noise and X-Ray Diffraction

Residual stress measurement on camshaft with X-ray diffraction and Barkhausen noise methods
Residual stress measurement on camshaft with X-ray diffraction and Barkhausen noise methods

Barkhausen Noise (BN) testing was implemented, as it is non-destructive and is able to look beyond the surface of the ground lobes.

In order to correlate the two methods, select spots on the lobe were chosen and the BN results and X-Ray diffraction stress depth profiles were compared.

The results

Barkhausen noise measurements:

The spots shown below are the areas where XRD Depth profiles were performed.  On lobe 1, spots were chosen at the ramps (blue & green), nose (yellow), and the center of the base circle (pink).  On Lobe 2, the nose (orange) was chosen.

Barkhausen noise measurement results on camshaft lobe.
Figure 1: Camshaft lobe 1
Barkhausen noise measurement result on camshaft lobe
Figure 2: Camshaft lobe 2

The residual stresses measured at a subsurface depth approximately 0.020mm below the finished surface were seen to have a linear relationship with the Barkhausen noise values.  This is shown in the following correlation results.

Correlation Results:

The favorable correlation enables the BN testing to be used at a much more frequent interval to supplement the XRD testing, all while not having to destroy any of the camshafts.

A Correlation Between Barkhausen Noise and X-Ray Diffraction
A Correlation Between Barkhausen Noise and X-Ray Diffraction.

Instruments used for this application:

CamScan 100

CamScan 100 is a semi-automated grinding burn and heat treatment defect detection system for low-volume applications. It is designed for quality control needs of small to medium sized circular symmetrical parts like passenger car shafts.

CamScan 100 detecting grinding burn on a camshaft
CamScan 100 detecting grinding burn on a camshaft

Xstress G2R

X-ray diffractometer Xstress G2R 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 G2R x-ray diffractometer
Xstress G2R X-ray diffractometer

Related articles:

Stresstech Bulletin 12: Measurement Methods of Residual Stresses

Stresstech Bulletin 5: Grinding Quality Control of Camshafts

Article Type: Application note
Part Under Inspection: Camshaft