Innovative Forging and Fabrication Solutions for the Nuclear Industry
Lead Research Organisation:
Sheffield Hallam University
Department Name: Faculty of Arts Computing Eng and Sci
Abstract
The Sheffield Hallam team will conduct novel experiments to characterise mechanical properties of formed and thick
section components from large forgings. Initial work will focus on developing the specimen design and test strategy using
3D Digital Image Correlation (3DDIC) to obtain Crack Tip Opening Angle (CTOA) resistance curves for the material; post
weld heat treated conditions will be of primary concern. Using CTOA measurements and crack extension data is an
established method of determining both KIc and JIc, using data from 3DDIC has been applied to thin section specimens
and will need adapting for thick sections particularly for uneven crack front phenomena.
Once specimen geometries and test techniques have been established the results will be compared to data for the same
material obtained using standard test methods according to BS EN to the UK Civil Nuclear code. This will serve as
validation of the suitability of DIC to determine fracture properties of the material.
Having validated the technique a series of tests comparing different heat treatment procedures and different regions of
interest in the forging (determined by SFIL) will be evaluated. The results of these tests will be compared to the
microstructural properties of the different specimens and optimal treatments identified.
Running concurrently with DIC based fracture toughness measurements will be a benchmarking fatigue program at
elevated temperature (c.700C) using the current treatment parameters for the material. This will provide baseline high
temperature fatigue properties. Once optimal microstructures are determined based on fracture toughness results a
second set of fatigue tests will be conducted using the ideal structure at elevated temperature to confirm any increase in
performance.
Once initial fracture characterisation is complete development work will start on acquiring high temperature values of KIc
and JIc, the equipment to adapt the currently available DIC hardware at SHU has been factored in and the potential results
are deemed to be of high value both to the academic community and the lead partner. A systematic approach drawing on experience within SHU and LaVision (hardware supplier) and a working relationship with Instron UK will enable trials to
take place with relative ease. Development work is likely to focus on the finer points of obtaining robust correlation from
the high temperature surface, namely speckle pattern retention and reducing interference from the emitted photons from
the specimen.
section components from large forgings. Initial work will focus on developing the specimen design and test strategy using
3D Digital Image Correlation (3DDIC) to obtain Crack Tip Opening Angle (CTOA) resistance curves for the material; post
weld heat treated conditions will be of primary concern. Using CTOA measurements and crack extension data is an
established method of determining both KIc and JIc, using data from 3DDIC has been applied to thin section specimens
and will need adapting for thick sections particularly for uneven crack front phenomena.
Once specimen geometries and test techniques have been established the results will be compared to data for the same
material obtained using standard test methods according to BS EN to the UK Civil Nuclear code. This will serve as
validation of the suitability of DIC to determine fracture properties of the material.
Having validated the technique a series of tests comparing different heat treatment procedures and different regions of
interest in the forging (determined by SFIL) will be evaluated. The results of these tests will be compared to the
microstructural properties of the different specimens and optimal treatments identified.
Running concurrently with DIC based fracture toughness measurements will be a benchmarking fatigue program at
elevated temperature (c.700C) using the current treatment parameters for the material. This will provide baseline high
temperature fatigue properties. Once optimal microstructures are determined based on fracture toughness results a
second set of fatigue tests will be conducted using the ideal structure at elevated temperature to confirm any increase in
performance.
Once initial fracture characterisation is complete development work will start on acquiring high temperature values of KIc
and JIc, the equipment to adapt the currently available DIC hardware at SHU has been factored in and the potential results
are deemed to be of high value both to the academic community and the lead partner. A systematic approach drawing on experience within SHU and LaVision (hardware supplier) and a working relationship with Instron UK will enable trials to
take place with relative ease. Development work is likely to focus on the finer points of obtaining robust correlation from
the high temperature surface, namely speckle pattern retention and reducing interference from the emitted photons from
the specimen.
Planned Impact
The Pathways to Impact statement details the strategy to maximise the impact of this work. The key impact will be realised
through the achievement of the principle aim, namely bringing novel experimental mechanical characterisation techniques
into the development of structural civil nuclear components, particularly in the optimisation of mechanical properties. In
addition, further developing advanced techniques for mechanical characterisation will benefit the study of fracture
mechanics and the failure of materials; this in turn will improve our fundamental understanding of mechanical failure.
The approach to maximise the dissemination and therefore impact of the findings will be to use both traditional publication
strategies and also through more diverse communication methods. Committing to public science talks and academic
workshops will help further the impact of this work.
through the achievement of the principle aim, namely bringing novel experimental mechanical characterisation techniques
into the development of structural civil nuclear components, particularly in the optimisation of mechanical properties. In
addition, further developing advanced techniques for mechanical characterisation will benefit the study of fracture
mechanics and the failure of materials; this in turn will improve our fundamental understanding of mechanical failure.
The approach to maximise the dissemination and therefore impact of the findings will be to use both traditional publication
strategies and also through more diverse communication methods. Committing to public science talks and academic
workshops will help further the impact of this work.
People |
ORCID iD |
| David Asquith (Principal Investigator) |
| Description | Corroborated research by Newman et al that DIC can be used to measure a critical CTOA value and that this value can be used to build numeric models of fracture behaviour. These values can be obtained from non-standard specimen geometries. Initial objectives to establish and implement 3DDIC techniques were met and CTOA resistance curves along with calculated KIC values were produced as required. It was noted that for valid tests no correction to the crack tip location was required based on an uneven crack front. Application of the digital optical techniques to recording and evaluating test data have proved very appealing to industry, this has generated a further collaboration as noted elsewhere. Comparison to industry standard approaches (using a clip-gauge in the mouth of the specimen) has shown that DIC (2D or 3D) is capable of producing equivalent data, furthermore it increases the fidelity of the data enabling review and re-evaluation should queries arise; given the cost and rarity of specimens in this field this is an important confirmation. This has been extended in the latter part of the project to evaluate JIC using a compliance technique and the results there are promising. One important complementary technique used here was a standard deflection calibration using a CEN/CWA 16799 beam to confirm performance of the calibrated 3D system. Although DIC users and providers often have confidence in the precision and accuracy, a standardised test such as this confirms that and provides reassurance to 3rd parties. Much of the work on microstructural performance comparing pre to post heat treated material has shown that the HT process has worked as expected, but importantly this contributes to the confidence in DIC to mirror data from standard techniques whilst providing enhanced test records. |
| Exploitation Route | Applications for further funding to develop critical CTOA and valid multiscale testing approaches. Collaborations on implementation of data richness to test evaluation have been established, these will benefit additional organisations (see collaborations) The key findings detailed above will help enable the community to develop and implement 3D-DIC in standard test methods to improve accuracy and confidence in measurement, in turn this will provide industries such as civil nuclear plant manufacturers with greater insight into better quality data. Many of the detailed observations made here will be further investigated by the SHU team and where applicable further funding sought to complete comprehensive studies; these in turn will further enhance industrial uptake of the technique. |
| Sectors | Aerospace Defence and Marine Energy Transport |
| Description | The research associate transferred from Sheffield Hallam to Sheffield Forgemasters to enable SF to establish their own dedicated test facility with digital image correlation to continuously evaluate mechanical properties of nuclear forgings with a throughput not manageable in SHUs labs. Since the project completed Sheffield Forgemasters have continued to develop their business in forging technology for energy generation, their continued excellence at the leading edge of forgings development has contributed to their nationalisation by the government. The project as a whole successfully implemented electron beam welding on larger forgings than previously achieved and demonstrated their superior properties enabling larger vessel fabrication. |
| First Year Of Impact | 2020 |
| Sector | Aerospace, Defence and Marine,Energy |
| Impact Types | Economic |
| Description | Experimental Continuüm Mechanics Facility |
| Amount | £37,480 (GBP) |
| Organisation | Higher Education Funding Council for England |
| Sector | Public |
| Country | United Kingdom |
| Start | 12/2016 |
| End | 04/2018 |
| Description | Crack Compliance and the J-Integral |
| Organisation | Element Materials Technology Ltd |
| Country | United Kingdom |
| Sector | Private |
| PI Contribution | Following on from detailed studies of fracture characterisation RR expressed an interest in collaborating with regards to investigating potential problems with quality testing using the crack compliance approach for the J-Integral. Comparative tests using industry standard methods at Exova and non-contacting optical techniques at SHU are being conducted. One J-Integral evaluation of representative steel has been conducted at SHU within this project with a view to demonstrating viability. Following this my team at SHU and I have provided expertise and advice on setting up DIC test techniques for acquiring surface data to compute a J-Integral value, we will shortly be supervising testing at Exova for a collaborative trial. |
| Collaborator Contribution | RR are contributing financially to enable the partners to travel and test without incurring costs to themselves in return for data and knowledge. In addition RR bring a wealth of historic data on materials performance and testing techniques. Exova are currently one of the main test houses for qualification of high performance materials such as nuclear steels. Their experience in testing to stringent industry standards is invaluable in informing decision making and execution of testing. They recognise that collaboration with SHU on non-contacting techniques is an excellent opportunity to add value to their current methods. Exova have brought expertise and past test data where they can evidence minor discrepancies in the output data from the expectations, the intention is to evaluate in-test events in more detail to increase the level of confidence in the resulting data and rule out further testing where possible. |
| Impact | 1 undergraduate final year project was developed and completed as a result. A further collaboration for SHU applying the technique to a dental material has initiated. |
| Start Year | 2017 |
| Description | Crack Compliance and the J-Integral |
| Organisation | Rolls Royce Group Plc |
| Department | Rolls-Royce Civil Nuclear |
| Country | United Kingdom |
| Sector | Private |
| PI Contribution | Following on from detailed studies of fracture characterisation RR expressed an interest in collaborating with regards to investigating potential problems with quality testing using the crack compliance approach for the J-Integral. Comparative tests using industry standard methods at Exova and non-contacting optical techniques at SHU are being conducted. One J-Integral evaluation of representative steel has been conducted at SHU within this project with a view to demonstrating viability. Following this my team at SHU and I have provided expertise and advice on setting up DIC test techniques for acquiring surface data to compute a J-Integral value, we will shortly be supervising testing at Exova for a collaborative trial. |
| Collaborator Contribution | RR are contributing financially to enable the partners to travel and test without incurring costs to themselves in return for data and knowledge. In addition RR bring a wealth of historic data on materials performance and testing techniques. Exova are currently one of the main test houses for qualification of high performance materials such as nuclear steels. Their experience in testing to stringent industry standards is invaluable in informing decision making and execution of testing. They recognise that collaboration with SHU on non-contacting techniques is an excellent opportunity to add value to their current methods. Exova have brought expertise and past test data where they can evidence minor discrepancies in the output data from the expectations, the intention is to evaluate in-test events in more detail to increase the level of confidence in the resulting data and rule out further testing where possible. |
| Impact | 1 undergraduate final year project was developed and completed as a result. A further collaboration for SHU applying the technique to a dental material has initiated. |
| Start Year | 2017 |
| Description | TWI Multiscale Fracture |
| Organisation | TWI ltd |
| Country | United Kingdom |
| Sector | Private |
| PI Contribution | Beginning to collaborate on the applicability of digital image corellation to characterising fracture parameters over a range of length scales (0.1mm - 1000mm), SHU proposes to develop and evaluate testing methods for standard and subscale fracture toughness measurements in metallic materials. |
| Collaborator Contribution | TWI will perform large scale fracture tests usually aimed at full scale validation of engineering critical structures to obtain comparative data to the SHU measurements. |
| Impact | None. |
| Start Year | 2017 |