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InnoSMART Report Summary

Project ID: 664892
Funded under: H2020-EU.1.2.1.

Periodic Reporting for period 1 - InnoSMART (An Innovative Method for Improving the Structural Integrity using SMA Revolutionary Technology)

Reporting period: 2015-07-01 to 2016-06-30

Summary of the context and overall objectives of the project

Metallic structures are nowadays used practically everywhere, often withstanding high loads and extreme conditions. Structural Integrity is the ability of a structure to withstand such loads, resisting structural failure due to fracture, deformation, or fatigue. Often the employment of materials in structures that operate in extreme environmental conditions has resulted in structural failures. This phenomenon happens very often in bridges, metallic structures, turbine blades, aircrafts, etc. Unfortunately, human casualties, rendering this problem of major importance for engineers, follow many of these failures.

In order to prevent such failures and improve the integrity of structures during their in service life, the InnoSmart project proposes an innovative attempt that will bring a breakthrough to material sciences and engineering, as well as to structural design. The InnoSMART project proposes to develop a revolutionary technology that will alter and control the mechanical properties of materials by external stimuli. This creation will be a novel coating able to contribute to the stiffness and rigidity of a metallic structure, to withstand safely the expected loads, to enhance the integrity of a damaged structure and at the same time protect it from corrosion.

The ultimate objective of InnoSMART is to improve the structural integrity of metallic structures by developing and delivering an advanced state of the art coating. The coating will be capable of protecting metallic structures from failures, as well as from corrosion extending their in service life. Additionally, quality control of the coating when applied to specific regions of the structure, as well as inspection procedures for damage detection will be developed for ensuring maximum efficiency of the coating. A numerical structural integrity assessment will be performed according to data extracted from the inspection procedure and the theoretical applied loads.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

During the first reporting period, the University of Ioannina (UoI) and SUN have been the main contributors to the WP1 and WP2, while EXIS and Cranfield collaborated on WP4, WP5 and WP7. The work within the first year of the project can be summarised as follows:

- The UoI and SUN performed a comprehensive state of the art of the SMA and related technologies regarding image processing for observation of deformed areas, methods for surface preparation and systems for applying metallic coatings, as well as surface and coating quality inspection techniques, and yielded important results for the selection of the optimal SMA’s. The extensive study of different SMA systems concluded that Nickel-Titanium based alloys are the best candidates for successful implementation as SMA coating systems on metallic substrates due to their strong SME, TWSME, and pseudoelastic behaviour, as well as their excellent deformation behaviour, very good fatigue resistance and resistance to corrosion. In addition, Nitinol, a Nickel Titanium alloy, combines three important mechanical features: biocompatibility, superelasticity and it is considered as a smart material due to its shape-memory. In particular, shape-memory feature depends on the change of a reversible phase of an austenite microstructure into a marten site microstructure. Moreover, this alloy is characterized by an outstanding plastic deformation behaviour and good resistance to fatigue and corrosion.

- The UoI also developed a novel constitutive model for polycrystalline SMAs, implemented in the Abaqus suite via a user subroutine, in order to analyse the SMA coating-elastic structure system both in isothermal and isobaric testing conditions. One main finding was targeted in guiding fabrication of SMA coated metallic structures. Based on the analysis, it is proposed that the SMA coating should be deposited on the compressive side of the elastic structure when under bending at low temperatures. Load removal of the structure will create tensile stresses and detwinning on the SMA-coating resulting in oriented marten site and macroscopic deformation. The innovative model for the SMA coating-elastic structure system, developed by UoI during this period, enables the optimisation of the setup for application of revolutionary technologies to create SMA coatings on metallic substrates.

- The UoI performed a detailed study of the state-of-the-art of shape memory alloy processing and training techniques. The basic forming techniques of SMAs were reviewed, including forging, rolling and cold-drawing and extrusion. Also, conventional and nonconventional machining techniques of shape memory alloys were examined. The state of the art in heat treatment and training of SMAs, including thermomechanical training procedures to obtain the shape memory effect, as well as of application techniques of SMA coatings on metallic substrates were also examined. The extensive studies performed by UoI during this period, including the state-of-the-art of SMA processing and training techniques, determination of the physical nature of the SMA elements, and investigation of SMA properties during processing, enable the successful application of revolutionary technologies to create SMA coatings on metallic substrates.

- The SUN research of the first year was focused on the evaluation of a proper deposition technique of shape memory alloy on metallic substrate. The assessment was carried out by considering the main operative variables, such as system geometry, methodology, process parameters. Two deposition methods were considered: ElectroSpark Deposition and High Velocity Oxygen Fuel (HVOF) spray. The former proved to be ineffective for the application of the coating since coating cohesion failure was found by Optical Microscopy analysis, therefore the High Velocity Oxygen Fuel (HVOF) spray method was proposed as the technique for deposition of shape memory alloy on metallic substrate. Good coating properties are expected by using HVOF process for coating deposition due to the higher particle velocity at impact and relatively lower particle temperature. Indeed coating adhesion strength increases as particle temperature and particle velocity are increased. HVOF process allows keeping these parameters under control choosing the best couple of values in order to obtain the coating properties required.

- The SUN group also performed a literature review concerning SMA coating and Nitinol, a Nickel-Titanium based alloy was found to be a proper SMA coating for its characteristics. In particular, Nitinol combines three important mechanical features: biocompatibility, superelasticity and shape-memory; shape-memory features depend on the change of a reversible phase of an austenite microstructure into a martensite microstructure. It is worth highlighting that the investigations required for Nitinol training, defining phase diagrams and time-temperature-transformation (TTT) diagrams and using HVOF technology, is one of the innovative aspects of the InnoSMART project. Moreover, coating deposition investigation activity will be carried out with and without applying tensile forces to metallic substrates, in order to assess the effect of this parameter on the physical-mechanical characteristics of the system “coating + substrate”.
Several techniques were identified for the characterization of uncoated samples, samples without training and samples with training in order to evaluate material properties.

- EXIS has done an extensive work combining literature review, with testing benchmarks for selecting appropriate FE software, and proposed ANSYS Mechanical as an analysis tool for the respective Tasks; The available software in the market have been initially listed and their capabilities according to the pre-set criteria have been noted. An extensive discussion of the features of the most powerful FE software package was made and it was concluded that the most promising FE software for the current application yield to be ANSYS Mechanical and Simulia ABAQUS. The advantages of those two software packages are among other their efficiency in solving fracture mechanics problems and their powerful FE non-linear solver as well as their scripting language. A benchmark analysis has been conducted between ANSYS Mechanical and Simulia ABAQUS to verify that both software packages calculate a typical fracture mechanics problem.

- EXIS has been working on the conceptual design of the manipulating device. Extensive discussions and collaborations between the project partners have occurred in order to determine the manipulator requirements and technical specification. One of the most critical and innovative points in the design of the manipulating device is to be able to perform all the necessary actions (Clean, Inspect, Spray).

- The main contribution from Cranfield was to design, purchase and further develop the laser profilometer suitable of surface damage inspection. The laser profilometer selection decision was made based on several factors such as number of points per profile scan, laser source type and resolution. From literature, strong evidence was obtained that a blue laser source can achieve ultra-stable and highly accurate measurement with any type of targets that are typically difficult to detect, even high temperature surfaces. The blue laser source also enables to capture data with less noise. The higher the number of points per scan higher will be the level of image quality. A LP capable of capturing 1280 points per profile was chosen. A profile refers to a single scan line which has in this case 1280 discrete points separated by 7.8-micron distance. Each point from laser profilometer represents the surface location with reference to the datum of the LP. Finally Scan Control 2900-10/BL laser profilometer was chosen, which had all the above-mentioned specifications. This laser profilometer was also chosen based on other factors such as weight and integration options. The weight of the laser profilometer without the cable and the mounting bracket is 480 grams. Laser profilometer is integrated with a linear magnetic encoder to capture synchronous data with respect to the movement provided by the traversing mechanism. The laser profilometer is mounted on a programmable traversing mechanism to perform laboratory trails.

- Cranfield has developed two novel image processing techniques to detect the damage as per above listed tasks. The first technique is based on the bicoherence estimation and the other technique is based on Edge detection algorithm. These techniques are developed based on Cranfield IP background and are radically new techniques developed particularly for damage detection using image data. The first technique is based on the bicoherence, a statistic used to search for nonlinear interactions. The intensity slices along horizontal and vertical directions are captured from the image data. Each slice is processed with the bicoherence estimation algorithm. The bicoherence value range from 0 to 1 and 0 represents an image segment without damage and 1 represents an image segment with damage. These bicoherence estimates are further processed to obtain a bicoherence feature called the Integrated Bichorence Feature (Developed based on Cranfield IP background). The other novel technique for damage detection and characterization is based on Edge Detection algorithm. Edges are pixels where image brightness changes abruptly. Edges are mathematically represented as Gradient. The gradient of the image is calculated for each pixel position in the image and the gradient image is further filtered using dilation and erosion operations to obtain a final outline on the image, which represents damage. The software developed using these novel techniques is currently under study. Both the developed image processing algorithms are capable of detecting the damage and are capable of mapping the damage to the original image. The input for both the software is the image of surface obtained using the laser profilometer. Trial tests were performed on composite material specimens, which are cracked and surface strained.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Since this is the first reporting period, the InnoSMART project has not yet progressed beyond the state of the art.

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