Fracture Analysis of High-Strength Screw for Highway Construction
Andrej Dubec1, Petra Kováčiková2, Jan Krmela2
1Department of Material Engineering, Faculty of Industrial Technologies in Púchov, Alexander Dubček University of Trenčín, Ivana Krasku 491/30, 020 01 Púchov, Slovakia.
Materials (Basel, Switzerland)
|April 3, 2021
Summary
Failure analysis of a high-strength screw revealed improper heat treatment. Investigations showed an undesirable intercrystalline fracture mechanism, compromising road safety for traffic sign structures.
Area of Science:
- Materials Science
- Mechanical Engineering
- Failure Analysis
Background:
- High-strength screws are critical fasteners in traffic infrastructure.
- Ensuring the reliability of these components is vital for road safety.
- Production process control alone may not prevent operational failures.
Purpose of the Study:
- Analyze the failure of a grade 10.9 high-strength screw used in highway construction.
- Investigate material properties, microstructure, and fracture surface characteristics.
- Identify the root cause of the screw failure.
Main Methods:
- Optical microscopy
- Scanning electron microscopy (SEM)
- Energy dispersive spectroscopy (EDS)
- Fractographic analysis
- Vickers hardness testing (HV1)
Main Results:
- Micropurity and chemical composition were within acceptable limits (ČSN ISO 4967).
- Microstructure identified as tempered martensite.
- Fracture surface exhibited an undesirable intercrystalline micromechanism.
- Vickers hardness measurements indicated significant heat treatment deficiencies.
Conclusions:
- The screw failure was attributed to improper heat treatment, specifically issues with tempering.
- The intercrystalline fracture mechanism highlights a critical material defect.
- Findings underscore the importance of rigorous heat treatment control for high-strength fasteners in safety-critical applications.
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