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Expansion bolts in aviation are more than just connecting elements: they secure vital components such as engine mounts – and must be able to withstand extreme vibrations, thermal loads, and the highest safety requirements. However, even modern titanium alloys often fail to achieve the required 100% fatigue strength. The result: costly rework, increased scrap rates, or even safety risks.

How can this problem be solved without compromising on weight, material, or cost-effectiveness? The answer lies in deep rolling, also called roller burnishing—a mechanical surface treatment process that not only improves surface quality but also introduces targeted compressive residual stresses into the subsurface area. A customer project by ECOROLL shows that with the right tool and process parameters, titanium expansion bolts can be processed in just 28 seconds to reliably achieve the required service life – while reducing costs by 25% and cutting processing time by 30%.

The challenge: titanium alloys and high safety requirements

Titanium is a popular material in aviation because it is lightweight yet highly strong. With a strength of 1,600 MPa and a hardness of 49 HRC, the titanium alloy used here offers the best conditions for highly stressed components. But it is precisely these properties that make machining so challenging, e.g., in cutting.

In aviation, every gram counts. This is why titanium is particularly popular here. However, titanium components must of course also be absolutely fail-safe. This is where many manufacturers reach their limits – and look for alternative solutions that improve both strength and cost-effectiveness.

The solution: Deep rolling with ECOROLL’s HG6-9 tool

ECOROLL relies on deep rolling – a purely forming process that does not require any material removal and specifically strengthens the subsurface area of the component. In this specific application, the HG6-9 tool was used:

• Tool design: A 6 mm ball on a clamping bar positioned perpendicular to the surface (0° angle). This ensures optimum and uniform contact pressure.
• Process parameters:
  • Contact pressure: 300 bar rolling pressure (≙ 750 Newton)
  • Rolling speed: 150 meters per minute
  • Feed: 0.1 mm per revolution
• Processing time: 28 seconds per screw – economical and reproducible.

Why these parameters?

• The rolling force generates optimum surface pressure and applies maximum compressive residual stresses to the subsurface area without damaging the material.
• The selected feed rate ensures sufficient coverage of the surface while maintaining high process efficiency.

The result: A homogeneous compressive residual stress state in the subsurface area, which prevents microcracks and increases fatigue strength by up to 100%.

Application example: Expansion bolt for engine suspension

An aerospace supplier was faced with the following problem: Its titanium expansion bolts met the mechanical requirements, but did not consistently achieve the required fatigue strength. 

Deep rolling with ECOROLL led to a breakthrough:

1. 100% fatigue strength: All tested components passed the service life tests.
2. 25% cost reduction: Less tool wear, less rework.
3. 30% time savings: The processing time was reduced from over 40 seconds to 28 seconds.
4. Lightweight construction compatible: No additional material usage, no weight increase.

Customer’s conclusion:

Deep rolling not only ensured fatigue strength, but also significantly reduced manufacturing costs, making the process an integral part of production today. 

Why deep rolling is the better choice

1. Targeted strengthening: Compressive residual stresses increase fatigue strength, which is particularly important for dynamic loads.
2. Economical: Shorter processing times and longer tool life reduce costs per part.
3. Sustainable: No material removal, no additional chemicals – ideal for climate-friendly production.
4. Flexible: The process can be adapted to different materials and component geometries.

Conclusion: Fatigue strength is not a coincidence, but the result of the right process

Expansion bolts in aviation must be absolutely reliable – with minimum weight and maximum cost-effectiveness. Here, deep rolling with ECOROLL tools offers a proven superior solution:

• 100% fatigue strength for all components.
• 25% lower costs and 30% faster processing.
• Process reliability that meets the stringent requirements of aviation.

Are you facing similar challenges? Whether titanium, steel, or other high-performance materials: ECOROLL develops customized deep rolling solutions for your application. Contact us for individual advice.