{{serverconnectlatestnews.data.showlatestnews.data[0].news_title}}
{{serverconnectlatestnews.data.showlatestnews.data[0].news_date.formatDate("d MMM yyyy")}}
{{serverconnectlatestnews.data.showlatestnews.data[0].news_teaser}}
Metallurgical Investigation - Fractured Bolt
Specialist Equipment
We carry out metallurgical investigations in our Advanced Materials Characterisation Centre using a range of analytical equipment. This includes optical microscopes, providing magnification of up to x1000, and our Scanning Electron Microscopy (SEM), providing high resolution images up to x100000.
Requirement
A dummy bar assembly is a machine used in industrial applications that transfers pulling force to a continuously cast material.
The client requested analysis of a bolt that had failed in the dummy bar assembly. They needed to establish if it was an isolated issue, or whether other bolts would be susceptible to failure.
Continuous bolt failure would be a significant issue for the client as it would impact on their production of cast product.
Project Activities
Following a visual examination the bolt was examined under our SEM which is equipped with Energy Dispersive Spectroscopy, which allows chemical analysis of non-metallic particles.
Findings
Visual Examination
- The bolt exhibited no ductile deformation.
- Part of the fracture face had been damaged on retrieval from the assembly.
- The fracture face was predominantly flat with no evidence of ductile failure. A 45-degree shear area was evident which is characteristic of a final brittle, sudden fracture.
SEM Assessment
- The presence of fine micro-cracking in the thread of the bolt. Oxidation product was observed in association with some of this cracking. This indicates that the cracking was present when the bolt was at temperature.
- Fatigue ‘beach marks’ in the bolt in the area of the micro-cracking in the thread.
- A flat, crystalline fracture in the area of the 45-degree shear.
Conclusion
This assessment indicated that the bolt failed due to fatigue which had caused a crack to propagate through the bolt leading to a sudden, brittle final failure.
Recommendations
It was recommended that the pre-loading and tightening conditions for the bolts were reviewed.
Contact the Materials Processing Institute
Enquire about services, facilities, and expertise.
