Tile Detachment Research Articles

Hygrothermal Simulation Applied to Degradation Modeling of Ceramic Facades

Facades are exposed daily to the incidence of degradation agents such as driving rain and solar radiation. Degradation mechanisms that alter the chemical or physical structure of the material are affected according to the level of incidence of such agents, thus leading to the rise of anomalies such as ceramic tile detachment and cracks. Currently, computer simulations are used to model the action of the climate agents, however, it is not always possible to estimate all agents and factors influencing the degradation process. The combined analysis of the results of the hygrothermal simulation and the degradation indicators of the ceramic facades allows a better understanding of the degradation process and mechanisms. The objective of this research is to simulate the degradation caused by the main climate agents and obtain a statistical model able to describe degradation in ceramic facades. The degradation measurement method (DMM) quantifies the degradation of facades as a function of the affected area. The degradation trend is expressed by indicators that consider the severity of different anomalies according to the affected area. The multiple linear regression model age-weighted indicated the total radiation and thermal stress and humidifying and drying cycles as the most representative variables in degradation modeling. Ceramic facades show slight degradation up to 17 years old, and the end of service life after 25 years. From 45 years of age onwards, facades tend to be in a state of severe degradation, impairing the building performance and safety of users.

GPR and Digital Survey for the Diagnosis and the 3D Representation of the Battle of Issus Mosaic from the House of the Faun, Pompeii (Naples, Italy)

The application of non-invasive geophysical techniques and digital surveys to explore cultural heritage is becoming a very important research field. The capability to detect inner and superficial changes in the inspected surfaces allows for imaging spatial inhomogeneity and material features and planning targeted conservation and restoration interventions. In this work, the results of a research project carried out on the famous Battle of Issus Mosaic, also known as the “Alexander Mosaic”, are presented. It is a masterpiece of ancient art that was found in 1831 in the House of Faun, the most luxurious and spacious house in Pompeii. It is notable for its size (3.41 × 5.82 m), the quality of workmanship and the subject that represents the culminating phase of the battle between Alexander Magno’s army and the Persian one of Darius. In 1916, it was moved inside the National Archaeological Museum of Naples, where the original horizontal location was changed with a vertical arrangement supported by an inner wooden structure, whose exact manufacture is unclear. Today, the mosaic is affected by important instability phenomena highlighted by the appearance of the significant detachment of tiles, superficial lesions and swelling of the surface. Given the important need to preserve it, a high-detail diagnostic study was realized through a digital survey and non-invasive geophysical surveys using ground-penetrating radar (GPR). The investigation was repeated after two years, in 2018 and 2020, with the aim of verifying the evolution of degradation. The work provided a high-resolution estimate of the state of the health of the mosaic and allowed for obtaining a three-dimensional reconstruction of the internal mosaic structure, including the formulation of hypotheses on the engineering supporting works of the twentieth century; this provides an essential tool for the imminent conservation project, which also implies restoring the original horizontal position.

Evolution and stability of tile detachment – Experiments and modeling

Detachment of bonded tiles undermines the aesthetics, functionality, and safety of innumerable buildings world-wide. The plate-type interfacial debonding mechanisms that are the root cause of tile detachments are difficult to observe and monitor because they are hidden by opaque external layers. This invisibility, together with the brittle nature of tile detachments, raises questions regarding the triggering, the two-dimensional evolution, and the stability features of the interfacial failure. The present study adopts a combined experimental–numerical approach to address these questions. Through the use of transparent tiles, the full process of tile detachments under a concentrated pullout load is novelly captured on video. The experimental force displacement curves reveal that the interfacial mechanism becomes unstable at critical points. Numerical modeling based on an inhouse specially tailored finite element formulation is used to further explore and interpret the experimental findings. Comparisons between the experimental and numerical results show the numerical model's ability to closely follow the debonding evolution and capture the variety of experimentally observed phenomena.

Dynamic Simulation of 1D Cellular Automata in the Active aTAM.

The Active aTAM is a tile based model for self-assembly where tiles are able to transfer signals and change identities according to the signals received. We extend Active aTAM to include deactivation signals and thereby allow detachment of tiles. We show that the model allows a dynamic simulation of cellular automata with assemblies that do not record the entire computational history but only the current updates of the states, and thus provide a way for (a) algorithmic dynamical structural changes in the assembly and (b) reusable space in self-assembly. The simulation is such that at a given location the sequence of tiles that attach and detach corresponds precisely to the sequence of states the synchronous cellular automaton generates at that location.

An investigation of pulsed phase thermography for detection of disbonds in HIP-bonded beryllium tiles in ITER normal heat flux first wall (NHF FW) components

Pulsed phase thermography (PPT) is a non destructive examination (NDE) technique, traditionally used in the Aerospace Industry for inspection of composite structures, which combines characteristics and benefits of flash thermography and lock-in thermography into a single, rapid inspection technique. The aim of this work was to evaluate the effectiveness of PPT as a means of inspection for the bond between the beryllium (Be) tiles and the copper alloy (CuCrZr) heatsink of the ITER NHF FW components. This is a critical area dictating the functional integrity of these components, as single tile detachment in service could result in cascade failure. PPT has advantages over existing thermography techniques using heated water which stress the component, and the non-invasive, non-contact nature presents advantages over existing ultrasonic methods. The rapid and non-contact nature of PPT also gives potential for in-service inspections as well as a quality measure for as-manufactured components. The technique has been appraised via experimental trials using ITER first wall mockups with pre-existing disbonds confirmed via ultrasonic tests, partnered with finite element simulations to verify experimental observations. This paper will present the results of the investigation.

Building Thermography: Detection of Delamination of Adhered Ceramic Claddings Using the Passive Approach

Tile detachment is a common durability problem of adhered ceramic claddings causing safety risks. Passive infrared thermography using solar heat gain can be used to detect delamination leading to detachment, and is advantageous especially in the inspection of middle to high-rise buildings envelope although it is qualitative by nature. In this paper, findings of in situ thermographic inspections are comparatively analysed with findings of tapping control and surface moisture measurement, and with findings of thermal simulations to evaluate their efficiency. Comparative analyses showed that passive thermography can be used as a preliminary inspection technique to detect delamination and decide whether further inspection with advanced methods is required to implement maintenance operations.

Cyclic heat load testing of improved CFC/Cu bonding for the W 7-X divertor targets

Extensive high heat flux cycling testing of pre-series targets was performed in the neutral beam facility GLADIS to establish the industrial process for the manufacturing of 890 targets, which will be needed for the installation of the WENDELSTEIN 7-X divertor. The targets are manufactured of flat tiles of CFC NB31 as plasma facing material bonded by an Active Metal Casting copper interlayer onto a water-cooled CuCrZr structure. Based on the results of the 3D thermo-mechanical FEM analysis of the CFC/Cu interface, an additional set of 17 full-scale pre-series elements including three design variations was manufactured by PLANSEE SE. The insertion of an additional plastically compliant copper interlayer between the cooling structure and the Active Metal Casting interlayer showed the best results. No critical tile detachment was observed during >5000 cycles at 10 MW/m 2. These results demonstrated the sufficient life time of the component for the expected heat load in operation.

Examination of C/C flat tile mock-ups with hypervapotron cooling after high heat flux testing

Two C/C flat tile mock-ups with a hypervapotron cooling concept, have been successfully tested beyond ITER specification (3000 cycles at 15 MW/m 2, 300 cycles at 20 MW/m 2 and 800–1000 cycles at 25 MW/m 2) in two electron beam testing facilities [F. Escourbiac, et al., Experimental simulation of cascade failure effect on tungsten and CFC flat tile armoured HHF components, Fusion Eng. Des., submitted for publication; F. Escourbiac, et al., A mature industrial solution for ITER divertor plasma facing components: hypervapotron cooling concept adapted to Tore Supra flat tile technology, Fusion Eng. Des. 75–79 (2005) 387–390]. Both mock-ups provide a SNECMA SEPCARB ® NS31 armour, which has been joined onto the CuCrZr heat sink by active metal casting (AMC) and electron beam welding (EBW). No tile detachment or sudden loss of single tiles has been observed; a cascade-like failure of flat tile armours was impossible to generate. At the maximum cyclic heat flux load of 25 MW/m 2 all tested tiles performed well except one, which revealed already a clear indication in the thermographic examination at the end of the manufacture. Visual examination and analysis of metallographic cuts of the remaining tiles demonstrated that the interface has not been altered. In addition, the shear strength of the C/C to copper joints measured after the high heat flux (HHF) test has been found to be still above the interlamellar shear strength of the used C/C material. The high resistance of the interface is explained by a modification of the C/C to copper joint interface due to silicon originating from the used C/C material.

Thermal Fatigue Testing of Actively Cooled Divertor Mock-Ups after Neutron Irradiation

In order to study degradation effects of neutrons on plasma-facing materials and joints, actively-cooled beryllium and CFC samples were irradiated in the High Flux Reactor in Petten up to 0.35 dpa at 350 and 700°C. Later, these samples were tested by means of an electron beam facility under static and cyclic heating conditions. The heat removal efficiency and the thermal fatigue behavior of these samples were compared to those of corresponding non-irradiated samples. A significant increase of surface temperature was observed for all samples, due to a reduced thermal conductivity of the CFC materials after neutron irradiation. This effect is less distinctive for samples irradiated at the higher temperature. Long term fatigue tests with 1000 heating cycles at 15 MW/m2 did not create any failure of the plasma-facing material or the bond layer of the tested mock-ups. Similar experiments have been performed with brazed beryllium-copper mock-ups. Flat tile mock-ups with an S65 C armor on a CuCrZr heat sink were loaded up to 1000 cycles at a power density of 7 MW/m2 without detachment of tiles.

Evidence of damage in carbon fibre composite tiles joined to a metallic heat sink under high heat flux fatigue

The two years experience with Active Metal Casting (AMC) flat bonds shows that this technology is suitable for the heat fluxes expected in Tore Supra (10 MW/m 2). Tests were pursued up to 3330 cycles, with elements still functional. At higher heat fluxes, fatigue damage is observed, but the bond resists remarkably well with no tile detachment. Examination of such deliberately damaged bonds showed distributed cracking, proving the absence of any weak link. The limitations to those higher heat fluxes are more related to the design and the base materials than to the bond itself.