Today's KNOWLEDGE Share:Failure Analysis of PC hub

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Today's KNOWLEDGE Share:


Failure Analysis of PC hub

I recently completed a failure analysis on a polycarbonate hub used to secure a steel tube. A number of parts had cracked while undergoing engineering use testing in the laboratory. The fractographic examination, which included scanning electron microscopy (SEM), revealed fracture surface features that indicated that the parts failed though the application of stress at a high strain rate. It was concluded that the engineering testing produced rapid mechanical overload, in which the stresses exceeded the short-term strength of the material. Plastic materials, including polycarbonate, can undergo a ductile-to-brittle transition associated with high strain rate events.




The high strain rate failure mechanism was specifically identified in the SEM images by the presence of features known as river markings. They extended out from and bounded the crack origin. The crack origin area also displayed a relatively smooth texture, which was indicative of a brittle fracture mode. The cracking initiated with a design corner (yellow circle), which likely acted as a point of stress concentration.


Source:The Madison Group

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#failureanalysis #plastics #fractography #SEM #polymerscience #materialsscience #polycarbonate #plasticengineering #crack #stress #fracture

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