Application Note: Barkhausen Noise on Camshaft for Cracks

In this application, camshaft lobe was checked for microstructural defects. These invisible non-uniform changes in the microstructure can ultimately lead to cracking at a later time.

The problem: Visible cracks on automotive components

During the production of automotive components, visible cracks can often occur as the result of deficiencies in the heat-treatment or grinding process. The underlying root cause of these cracks, however, are often invisible and not able to be readily detected. These invisible non-uniform changes in the microstructure can ultimately lead to cracking at a later time.  A common method to see these microstructural conditions is to destroy the component using labor-intensive metallography. Magnetic particle inspection, also a labor-intensive process, is commonly used for crack detection.

The testing method: Non-destructive Barkhausen noise analysis

Figure 1. Barkhausen noise analysis on camshaft lobe with automated CamScan 500C system.

Barkhausen noise analysis is an alternative method that can be used to detect the parts with these microstructural defects quickly and non-destructively. Barkhausen noise testing is a non-destructive method that is sensitive to changes in stress and microstructure at or near the surface of a ferro-magnetic material.

To acquire the data, camshafts were placed into a CamScan 500 inspection system, shown in Figure 3.  A camshaft sensor was lowered onto each lobe and the cam was rotated. The response from each lobe was recorded with specific software for an immediate disposition.

The results

The system was able to sort the acceptable and rejectable camshafts with 100% accuracy. In this case, rejectable was defined as parts with cracks or uncracked parts with non-uniform microstructure.

Polar plots of Barkhausen noise response showing (a) acceptable and (b) rejectable cam lobes.
Figure 2. Polar plots of BN response showing (a) acceptable and (b) rejectable cam lobes

Instrument used for this application:

CamScan 500C

The CamScan 500C system provides ease-of-use achieved with full automation but with the size, cost, and simplicity of a manual gauge.

Figure 3. CamScan 500C system is available in two different lengths, with door, or safety light curtain option.

Stresstech Bulletin 5: Grinding Quality Control of Camshafts

Stresstech Bulletin 3: Detection Methods of Grinding Damages

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Article Type: Application note
Part Under Inspection: Camshaft
Product Line: CamScan 500C