We carried out a comprehensive investigation on the alloy handle to find the cause of the failure. Here are our key findings:
The handle assembly had fractured into two sections on the main handlebar, and another fracture was evident at the section where the handles connect to the main pushchair frame.
We carried out a microscopic examination to analyse the fractures, which were found to have bright, reflective surfaces, and a smooth surface with rounded features. These characteristics are typical of burnishing, caused by relative movement between contacting fracture faces.
We also performed tensile and hardness tests to identify the maximum load that the pushchair handle can withstand before failure, as well as chemical analysis to ensure the alloy material used in production complies with quality standards (EN AW-6463).
Our results indicated that during its service, extreme loads were applied to the pushchair’s handle, causing the handle to flex and initiate fatigue fractures at the machined slot walls that acted as stress raisers. Over time, and with further application of cyclic loads, the fractures propagated through the entire cross-section, separating the material in two.
This means that the pushchair handle was subjected to cyclic loads of sufficient magnitude to cause fatigue fracture through the handle. Likely causes would include misuse of the pushchair handle, for example carrying bags on the handles, creating an uneven load, and intensifying the forces to be controlled by the material.
"We would like to thank Rotech Laboratories for their service. We have been satisfied with our experience and cost-effective service.“
- Colin
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