CREEPIMAGE

Development of a long term creep monitoring image based technique

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 Obiettivo del progetto (Objective)

'The CreepImage project will develop a digital image technique for long term measurement and monitoring of creep deformation of an engineering structure/component under harsh conditions (high temperature, irradiation etc) where direct sensor attachment and human access are difficult or dangerous. A high definition digital camera equipped with a suitable lens (macro, telescopic or telecentric lens) will be used to capture images of a grid on the component surface at various stages, and digital image correlation (DIC) will be used to calculate the deformation associated with creep behaviour of the component.

The procedure is expected to be as follows: (1) Physically produce a grid on the surface of the structure. It serves as the information carrier from which deformation can be calculated by DIC. (2) Capture digital images of the grid at different stages. A reference plate with a stable known coefficient of thermal expansion (CTE) will be placed adjacent to the grid such that it can be imaged simultaneously. This permits automatic calibration without the need to keep the camera on site all the time. (3) DIC software will be used to calculate the overall deformation. Creep strain is obtained by subtracting the thermal deformation.

The project work will be a laboratory based demonstration to validate the proposed techniques and to investigate the measurement capability (accuracy, repeatability etc). In addition to nuclear plants, other potential application areas include evaporators in a power plant.'

Introduzione (Teaser)

EU-funded scientists developed a novel approach for checking the integrity of components operating under harsh conditions at power stations.

Descrizione progetto (Article)

Extreme temperatures and stresses in engineering components such as steam pipes in a power plant may cause weld cracks that may grow until the pipe breaks. However, existing creep strain measurement techniques are difficult to apply in a power plant due to oxidation at high temperature over a prolonged period of time. The lack of long-term accurate creep measurement leads to poor creep life prognosis, putting European power generation infrastructure at risk.

Scientists initiated the EU-funded project 'Development of a long term creep monitoring image based technique' (CREEPIMAGE) to accurately measure creep deformation and extend component life beyond the original design limits in power stations. The project used digital images for long-term creep measurement and monitoring of pipework where direct sensor attachment and human access are difficult or dangerous.

Scientists integrated a digital camera equipped with a telecentric lens into a compact prototype system that allows quick deployment on a power plant pipe. They also fabricated a protective casing for the inspection coupon and trialled it on an ex-service pipe. To produce a high-density grid pattern on the inspection coupon, scientists formulated a micro laser cladding procedure, developed integrated software that allowed the operator to acquire images and calculate strain based on digital image correlation analysis.

Based on a model and surface creep strain measurements, the project developed a methodology to predict component remaining life and incorporated it in the system.

Comprehensive analysis of the accelerated creep test data obtained from two different pipes showed that the CREEPIMAGE system is capable of providing highly accurate creep strain measurements.