How to Do Bearing Failure Analysis

Bearing Failure Analysis is the process of collecting and analyzing bearing data to determine the cause of a bearing failure.   

When a Bearing Failure Analysis is needed 

Bearing Failure Analysis is a vital tool used when bearing(s) are submitted by a customer who requests a bearing analysis of a reported bearing failure.   It is also essential in the development of new or improved bearing products and applications. 

Performing the Bearing Failure Analysis  

Collecting failure data: 

• Obtain all the failed components related to the bearing failure (bearing, housing, mating surface) and other related materials such as lubricants or fluids, wear debris, seals and application components.   

• Confirm actual operating conditions data such as load, speed, temperature, torque, lubricant, flow rate; parameters that are found on a Materials Application Data Sheet. 

• Obtain test/failure data such as printouts of measured dimensional and performance parameters, time of test or service, customer’s reason(s) for reporting a failure. 

• Obtain specifications for materials used in the application (shaft and housing material specifications, lubricant and fluid specifications) and even the customer’s design FEMA.  

Analyzing the data:  

1. Visual examination of the failed components with and/or without a microscope.  Photographs should be taken as needed.  Focus should be on, but not limited to, the following failure issues: severe wear; abnormal wear pattern; discoloration; debris; deformation; delamination; damage to bearing other than the intended sliding surface. 

2. Technical review of operational data to confirm suitability of the bearing material and overall design to the actual operating conditions.  This step will include, but not limited to, comparing of actual operating parameters (specific load (p), speed (U), pU, temperature) with bearing material properties capabilities; determination of bearing material’s chemical resistance to fluids or gases that may be present; estimate dry bearing life using actual operating parameters; or, if the application was lubricated, estimate lubrication regime (boundary, mixed-film, full hydrodynamic film).   

This technical review should confirm that the bearing should have met the operational requirements for bearing performance.  If not, this may mean the bearing material selection was the reason for failure pending further examination of the failed bearing and components. 

These two basic steps alone may lead to a satisfactory response to the bearing failure or may indicate a need to develop a strategy for advanced steps of dimensional measurements and/or material analysis using a wide array of non-destructive and destructive methods like: 

• Using a coordinate-measuring-machine (CMM); 

• Measuring surface texture 

• Sonic erosion tests 

• Differential Scanning Calorimetry (DSC)  to observe fusion and crystallization events as well as glass transition temperatures Tg 

• ThermoGravimetric Analysis (TGA) to evaluate the thermal stability of a material 

• Energy-Dispersive X-ray Spectroscopy (EDS, EDX, or XEDS) to determine which chemical elements are present in a sample and to estimate their relative abundance 

• Material hardness tests 

• Tensile/compressive tests 

• Three-shoe wear tests 

• Corrosion resistance tests 

Issuing the report: 

• Whether we use only basic analysis or supplement basic analysis with advanced analysis, the final step in the failure analysis is issuing a report.  Depending upon the scope of the analysis, the report may be very simple or extensive. 

• A basic failure analysis report may be sufficient with only the Background Information (which includes the technical review), Visual Examination (which may include basic dimensional measurements) and Conclusions (which may include recommendations).  This is may be all that is required, particularly if this was a routine failure analysis for a given customer’s application. Technical analysis can be added if more detail is needed to satisfy the customer. 

• If the basic analysis is not sufficient to satisfy the needs for failure analysis, then you will need to prepare a strategy that first will use non-destructive test/measurement techniques and, if needed, destructive testing to complete the failure analysis.  Depending upon the need for advanced analysis the report may include the reports of those additional analyses to further support the report’s conclusions and recommendations.