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Ultrafast lasers to be used in Sydney Harbour Bridge renovation

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New large-scale cleaning techniques involving powerful ultrafast lasers are being developed within a collaborative project that seeks to renovate the 90-year-old Harbour Bridge in Sydney, Australia.

The three-year, $858,000 project is being undertaken by the Australian Nuclear Science and Technology Organisation (ANSTO), Australian universities and the Government of New South Wales. It will combine ultrafast lasers with robotics in order to produce a practical robotic system capable of cleaning corroded metal and dirt-encrusted surfaces on the bridge, even in inaccessible areas.

 

In addition to cleaning, the robotic system will also undertake inspections, re-paint cleaned surfaces and remove waste.

Laser cleaning has been used widely to remove contamination from historic architecture when traditional renovation methods are not viable.

The new techniques being developed within the project will replace such traditional methods currently used on the Harbour Bridge, including the sandblasting of dirt, rust and existing lead-based paint from its metal surfaces. Sandblasting not only creates a lot of dust, but is also impractical for use in the 7.2 kilometres of tightly confined tunnels on the bridge, which are inaccessible to humans.

By contrast using ultrafast lasers will not only produce minimal dust and waste, but will also increase the throughput of cleaning while substantially reducing the heat load to the bridge’s structure, reducing energy costs and improving the control of the characteristics of the bridge’s metal surfaces following treatment. This will enable better long-term conservation of the cleaned surfaces by preventing detrimental damage such as residual stresses, micro-cracking or roughening, which can decrease structural performance and surface integrity.

As part of the project, stress assessments to materials using x-rays and nuclear techniques will be undertaken by ANSTO at its facility in Lucas Heights.

‘The team will analyse mechanical properties of laser-treated steel and granite for fatigue resistance, roughness, understanding the microstructure, and distribution of stresses,’ said Dr Anna Paradowska, industrial liaison manager and senior research scientist at ANSTO. ‘We are very excited to utilise nuclear science and expertise to help develop technology that will help maintain Sydney Harbour Bridge – an iconic image of Sydney, and Australia itself!’

Professor Andrei Rode, of the Australian National University, added that this will be the first time a laser cleaning process like this has been used on such a large-scale.

The project partners also say that the new techniques under development will be able to offer improved safety and economic benefits in building maintenance, in addition to reducing the amount of scrap in the marine, automotive and aircraft industries.

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