#	Pagina
attuale pagina	/open-h2020/projects/196956/results.html

Report

Teaser, summary, work performed and final results

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

Teaser

Summary

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

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 SMAâ€™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 expe