Tile Thickness Research Articles

Manufacturing and Examination for ITER Blanket First Wall Small-Scale Mockups With KoHLT-EB in Korea

The ITER first wall (FW) includes beryllium armor tiles joined to a CuCrZr heat sink. The FWs are one of the critical components in an ITER machine with a surface heat flux of 4.7 MW/m2 or above. The small-scale mockup shall be a part of the qualification tests and used to validate the performance of the dominant manufacturing technologies before the production of larger scale components, and this mockup shall be equipped with a hypervapotron heat sink and manufacturing processes developed for a semiprototype design. The small-scale mockup includes 48 beryllium armor tiles (12 mm × 12 mm) capable of withstanding the specified heat flux values. The tile thickness shall be 6 mm to minimize the beryllium surface temperature and evaporation under high thermal loads. The detailed fabrication process of semiprototype small-scale mockups was developed for a qualification test in Korea. For the CuCrZr and stainless steel, the canned materials are processed into an hot isostatic pressing (HIP) device. In the case of beryllium-to-CuCrZr joining, the HIP was conducted at 580°C and 100 MPa. For nondestructive tests of the fabricated semiprototypes, visual and dimension inspections were performed whenever needed during the fabrication process, and ultrasonic tests were performed using ultrasonic probes. Destructive tests for the qualification semiprototype were performed on a small-scale mockup, which was fabricated together with semiprototypes. The Korea heat load test facility using an electron beam system was constructed with an electron gun (maximum electric power of 800 kW) for a high heat flux application with a 300-kW high-voltage power supply and maximum accelerating voltage of 60 kV. This facility was operated to evaluate the performance test of plasma facing components. A cyclic heat flux test will be performed to evaluate the ITER qualification program.

Microstructure and technological properties of porcelain stoneware tiles moulded at different pressures and thicknesses

Abstract Moulding pressure and thickness are pre-fixed variables in the porcelain stoneware tile industry. This paper examines the effect of both parameters on technological and microstructure properties of unfired and fired porcelain stoneware bodies. The moulding pressure in unfired tiles has a noticeable effect on bending strength and load borne. Common technological properties such as water absorption, porosity, bulk density and bending strength were obtained from the fired tiles. The results indicate that the variation in properties is independent of the thicknesses of the tiles. Moulding pressure affects at lower values, whereas higher moulding pressure produces tiles with similar technological properties. The microstructure exhibits a constant amount of mullite and quartz in all pieces after the firing process. Observations from scanning electron microscopy show that mullite crystals enlarge as moulding pressure increases, but the shape of the crystals are unaffected by the individual thicknesses. Furthermore, the aspect ratio of the mullite needles increases with the moulding pressure, which is invariable to the thicknesses of the tiles. Although the total porosity remains constant, the number of pores is influenced by the thickness. The moulding pressure also influences pore size. The results show a strong relationship between the number of closed pores and the thickness of the ceramic tile.

Phase in non‐reciprocal gyromagnetic waveguides using multiple ferrite tiles

The non-reciprocal phase shifter in the design of the waveguide differential phase-shift circulator consists of two or four suitably magnetised ferrite tiles on the top and bottom walls of the waveguide. It may be adjusted in terms of a reciprocal condition and a non-reciprocal one. The first condition essentially fixes the geometry of a typical phase-shift section except for the thickness of each ferrite tile; the second determines the connection between the split-phase constants and the thickness of the tiles for parametric values of gyrotropy. The purpose here is to satisfy the first requirement of the two-tile geometry using a calculation and to meet the second one by having recourse to measurements. It includes some preliminary experimental data on new four- and eight-stacked ferrite tile structures. It is likely to prove of value in the design of large continuous wave power devices.

Penetration Mechanisms and Ballistic Performance of TiC-TiB2 Composite Armour under the Impact of Long-Rod Kinetic-Energy Projectiles

Based on preparing TiC-40mol%TiB2 composite by combustion synthesis under high gravity, the ballistic targets with different-thickness ceramic tiles were achieved by lateral, cover and back confinements of shrink-fit steel. Ballistic testing showed that as the thickness of ceramic tile was smaller than 12 mm, the penetration of the ceramic tile was mainly controlled by the combination of the initial-shock and steady-state penetration, resulting in poor ballistic performance of the ceramic. As the thickness of ceramic tile was larger than 12 mm, the penetration of the ceramic tile was controlled by the combination of steady-state and third-stage (projectile deceleration and erosion acceleration) penetration, resulting in improved ballistic performance of the ceramic.

Ballistic Performance of TiC-TiB<sub>2</sub> Composite Armour under the Impact of Long-Rod Tungsten Alloy Projectiles of 1.4 Km·s<sup>-1</sup>

Based on preparing TiC-40mol%TiB2 composite by combustion synthesis under high gravity, the ballistic targets with different-thickness ceramic tiles were achieved by lateral, cover and back confinements of shrink-fit steel. Ballistic testing showed that as the thickness of ceramic tile was smaller than 12 mm, the penetration of the ceramic tile was mainly controlled by the combination of the initial-shock and steady-state penetration, resulting in poor ballistic performance of the ceramic. As the thickness of ceramic tile was larger than 12 mm, the penetration of the ceramic tile was controlled by the combination of steady-state and third-stage (projectile deceleration and erosion acceleration) penetration, resulting in improved ballistic performance of the ceramic.

An experimental study on ballistic performance of boron carbide tiles

Boron carbide is an attractive candidate for use as armour material because of its lower density combined with high hardness. The ballistic performance of boron carbide tiles were evaluated using standard Depth of Penetration (DOP) test method against hard steel 7.62 mm armour piercing (AP) projectiles. The effect of variation in thickness of tile and the projectile velocity on the ballistic efficiency of the material was studied. It has been found that the differential efficiency factor (DEF) increases with increase in projectile velocity from 600 to 820 m/s. And an insignificant or marginal increase in efficiency was observed for increase in tile thickness from 5.2 mm up to 7.3 mm. The effect of the type of radial confinement on the residual DOP was also studied. It was found that the steel radial confinement produces lower residual DOP values compared to aluminium alloy and with no radial confinement. Results along with photographs have been presented.

Measuring the strength of brittle materials by depth-of-penetration testing

Based on an energy conservation model, the strength offered by a number of brittle materials has been calculated from depth-of-penetration (DOP) test results. Each material was completely penetrated by a tungsten carbide cored projectile of known kinetic energy and the residual penetration into a ductile aluminium alloy backing material was measured. The energy transferred to the tile by the projectile has been calculated and has been shown to vary linearly with the tile thickness. From the energy transferred to the armour tile, the mean resisting stress that was offered to the penetrator was calculated and for the materials tested, scaled with the material hardness. This work shows that for DOP testing, where the projectile remains intact, the measured DOP is merely a facet of the ceramic’s hardness and not its true ballistic performance. The possibility of using this method to measure the strength of damaged ceramic is also discussed.

Mechanics of discontinuous ceramic tile core sandwich structure: Influence of thermal and interlaminar stresses

The stress states in a discontinuous ceramic tile core sandwich structure due to mechanical and thermal loading are investigated. The influence of coefficient of thermal expansion (CTE) mismatch between the tile and face sheet layer on the in-plane and interlaminar stresses in the sandwich structure is evaluated. The factors affecting the interlaminar stresses in the structure are of particular interest. The influence of an adhesive layer between the face sheet and core on the effective properties of the sandwich is also discussed. A study is performed to evaluate tailoring of the adhesive properties to reduce interlaminar stresses for increased durability. A parametric study is performed to study how various geometric parameters such as tile and adhesive layer thickness affect the effective properties (e.g. axial modulus and CTE). Failure of the discontinuous core sandwich structure under in-plane tension loading is analyzed. It is observed that thermal property mismatch in the structure can significantly reduce the failure loads for the tile layer. Finally, failure of the sandwich corresponding to various failure modes is discussed.

Monitoring defects of ceramic tiles using fuzzy subtractive clustering-based system identification method

In this paper, a subtractive clustering fuzzy identification method and a Sugeno-type fuzzy inference system are used to monitor tile defects in tile manufacturing process. The models for the tile defects are identified by using the firing mechanical resistance, water absorption, shrinkage, tile thickness, dry mechanical resistance and tiles temperature as input data, and using the concavity defect and surface defects as the output data. The process of model building is carried out by using subtractive clustering in both the input and output spaces. A minimum error model is developed through exhaustive search of clustering parameters. The fuzzy model obtained is capable of predicting the tile defects for a given set of inputs as mentioned above. The fuzzy model is verified experimentally using different sets of inputs. This study intends to examine and deal with the experimental results obtained during various stages of ceramic tile production during 90-day period. It is believed, that the results obtained from the present study could be considered in other ceramic tiles industries, which experienced similar forms of defects.

The mineralogical microstructure of shells: PART 2. The iridescence colors of abalone shells

The iridescence colors of abalone shell arise from Bragg diffraction of light from the layers of the nacre. The thickness of the aragonite nacre tiles is locally regular but varies during the growth cycles of the shell and this can give rise to complex color play. In Paua shell (Haliotis iris) and in H. fulgens (particularly the muscle scar shell) the thickness of the nacre tiles varies from 0.25(3) to 0.39(3) μm, but locally the thickness is constant within domains of hundreds of tiles. Other species such as H. laevigata and H. rufescens are similar, but their tile thicknesses range from 0.35(4) to 0.52(4) μm. In all species, the color displayed changes with observation angle and is due to layer diffraction. In H. iris and H. fulgens, the colors displayed encompass the complete visible spectrum; color hues are pure and are well-defined first-order diffraction colors. Shells of the other species display red and green, but not blue colors. The colors are rendered most vividly where dark organic growth layers are formed. These absorb or scatter light and enhance the iridescence colors. The origin and nature of the diffraction colors are compared with those observed in labradorite and opal. The degree of regularity in tile thickness needed to allow diffraction colors to be generated is modeled using pearl (sheet nacre) and abalone shell (columnar nacre) as examples. The wavelength dispersion is proportional to the product of the squares of the refractive indices of the material, the normalized standard deviation of the thickness, and the order of the diffraction color. For this reason, only first-order diffraction color is seen from shells.

An experimental study of penetration resistance of ceramic armour subjected to projectile impact

An experimental study has been carried out on the ballistic performance of 95% and 99.5% alumina ceramic tiles backed by metal plates, when subjected to normal impact of hard steel 12.7 mm armour piercing (AP) projectiles at velocities ranging from 500 to 830 ms −1. Typical damaged targets and broken projectiles are presented. The depth of penetration is measured in all the experiments, and the ballistic efficiency factor of the ceramic plates are determined. Results show that the efficiency factor increases with increase in projectile velocity. With the increase in thickness of the ceramic tile, the ballistic efficiency factor for a given velocity is observed to decrease in the case of 99.5% grade and increase in the case of 95% grade ceramic. The higher purity alumina (99.5%) shows higher ballistic performance when compared with the 95% alumina. The 99.5% alumina exhibited a predominantly transcrystalline fracture while the 95% alumina showed a less defined fracture surface. Experiments on 7.62 mm AP shots were also done keeping the ( d / t ) ratio same as in 12.7 mm AP experiments and results are presented.

Drilling of slate tiles by CO 2 laser

Slate is a natural stone used primarily as a roof building material after it is split into thin flat layers. These thin plates can be used directly as roof tiles just after being cut to the required shape and properly drilled for an adequate clamping. We have undertaken a series of experiments to investigate the feasibility of using a 1.5 kW CO 2 laser to drill slate tiles. The influence of different parameters involved in the process (such as average power, tile thickness and type of assist gas) on the hole geometry has been studied. The results obtained show that the CO 2 laser is a feasible tool for successful drilling of commercial slate tiles.

EXPERIMENTAL EVALUATION OF THE IMPACTABSORPTION PROPERTIES OF RUBBER TILES FOR THE PLAYGROUND

Rubber tiles are popular in playgrounds as protective surfacing to reduce the incidence of head injuries caused by children falling from equipment. However, Taiwan has not yet established a test code for assessment of the shock-absorption properties of such surfacing. For this study, an experimental model was established to evaluate the behavior of various rubber tiles. A hemispherical headform was dropped from a set height to strike the center of the specimen tile. The peak acceleration and Head Injury Criterion (HIC) were measured to assess the impact absorption of and critical height for a given rubber tile. The results show that utilization of the HIC index provides a more conservative assessment of the shock absorption and, ultimately, protection from head injuries than peak acceleration. The maximum critical heights of the rubber tiles used in this study for tile thicknesses of 45, 60 and 80 mm were 1.6, 2.0 and 2.2 m, respectively. Two-part rubber tiles with a base structure consisting of a box-like core offer superior protection from head injuries relative to analogous cylindrical, square pillar and solid structures. The maximum differences in peakacceleration and HIC values comparing the box-like core and solid structures at a thickness of 45 mm were 21% and 44%, respectively. The results of this study suggest a minimum of rubber thickness of 60 mm, based on probable maximum fall heights of more than 1.6 m. Moreover, incorporation of an appropriate cushioning structure in the base of the rubber tile could further improve protection.

Tests and analyses for the mechanical and thermal qualification of the new RFX first wall tiles

The graphite tiles of the RFX first wall were modified to achieve a more uniform power deposition on the plasma facing surface and to give housing to a large number of in-vessel probes. These design requirements led to a substantial reduction of the tile thickness with respect to the original design. For this reason, the new first wall tiles had to be carefully qualified both from the mechanical and thermal point of view, carrying out experimental tests and analyses.

Variable Thermal Emittance Radiator Using Metal-Insulator Phase Transition in La1-xSrxMnO3

A variable-emittance radiator device, made of thin and light ceramic tiles, has been developed for thermal control applications on spacecraft. The ceramic material used is La1-xSrxMnO3 with a perovskite structure, and shows a phase transition from ferromagnetic metal to paramagnetic insulator at around 290 K (Tc). This device automatically controls a spacecraft's temperature without electrical or mechanical instruments. Below the Tc, the device is metallic with a low thermal emittance of 0.3, and above the Tc, it becomes insulative with a high thermal emittance of 0.7. For the ceramic tiles, two different fabrication processes were studied to reduce the cost and weight; one is a conventional ceramic wafer process and the other is a thick film process on zirconia substrates. Total thickness of the ceramic tiles obtained is less than 70 µm and the weight is 450 gr/m2.

On the inelastic shock profile in alumina

The dynamic response of alumina specimens, above their elastic limits, was studied using planar impact experiments with different tile thickness. Stress-time measurements with manganin gauges show a steady spreading of the inelastic portion of the shock profile with increasing tile thickness. Such behavior is typical of elastic waves moving at a constant speed that depends on their amplitude. This finding supports recent interpretations of the failure ramp, by which the elastic response of these materials should be extended to higher stresses than the initial jump. However, further analysis of these profiles raises some questions regarding the exact determination of the Hugoniot elastic limit.

Analysis of ceramic/metal armour systems

A combined numerical and experimental study for the analysis of ceramic/metal composite armour system against 40.7 g steel projectiles has been performed. The ballistic performance of the add-on lightweight armours was examined by varying the thickness of tiles, while maintaining equal areal density of the system. A numerical study using smoothed particle hydrodynamics scheme is promising since the major distinguishing features of composite armour systems such as, projectile erosion, crack propagation, ceramic conoid formation and failure of backing plate, are successfully captured. Simulation results for ballistic limits appear to match fairly well with the test values and reveal an optimum value of the front plate to back plate thickness ratio.

Decay of elastic waves in alumina

The dynamic response of alumina under shock compression was studied using planar impact experiments with different tile thicknesses. Stress-time measurements were made with manganin gauges backed by different backing materials in order to optimize gauge response. The results show an apparent decay in the Hugoniot elastic limit with propagation distance. However, further analysis reveals that this phenomenon is probably a measurement artifact, resulting from the relatively slow response times of manganin gauges.

Quasi-static impact damage in confined ceramic tiles

The effect of confinement on the failure mechanisms in dense alumina tiles during the penetration of a projectile was investigated and the role played by lateral mechanical confinement in inhibiting some failure modes was examined. Alumina tiles were placed in a confinement frame which simply and accurately allows high biaxial compressive pre-stresses. The confinement frame is a modular system which enables the application of various boundary conditions on the impacted tile to be generated. Tile samples were supported by semi-infinite support blocks made of steel or aluminum, and were confined by steel wedges. In the tests carried out under ballistic penetration conditions, the confined tiles were impacted by 0.3 cal. NATO AP (armor piercing) projectiles. These contained a hardened steel cone-shaped core with a sharp tip. In this investigation, the effect of reflected stress waves was small or even negligible, since the tile/support impedance mismatch was low, so that quasi-static failure mechanisms predominated. The effect of tile thickness on the damage mechanisms was also examined. Under the described test conditions, the major failure modes were radial cracks, cone crack, and fragmentation of the cone. Confined tiles exhibited reduced damage; damage in the form of radial cracks was reduced, and cone crack and fragmentation of the cone were inhibited. Based on the theory of a plate on an elastic foundation, the quasi-static loads that initiate the radial cracks were formulated. This model assists in understanding the initial damage mechanism.

The influence of experimental design on depth-of-penetration (DOP) test results and derived ballistic efficiencies

Experimental data for ceramic armor materials from two test methods, small-scale reverse ballistic tests and depth-of-penetration (DOP) tests, are reviewed and compared. Results from reverse ballistic tests can be used to estimate the length of rod erosion in the ceramic tiles of DOP tests. The outcome of a given DOP test can then be predicted by using recently published data bases on RHA penetration to determine the residual penetration into the steel back-up of the DOP test. Results of this methodology, compared to experimental DOP-test results, agree reasonably well for aluminum nitride and silicon carbide, even though scale sizes, impact velocities and experimental procedures varied considerably between investigators. The methodology was then applied to single-valued performance criteria for ceramic armor materials, for example, mass efficiency. This analysis demonstrates that in certain cases, test parameters, like the ratio of penetrator length to ceramic tile thickness, affect test results considerably more than differences between ceramic types. Thus, DOP tests must be properly designed and interpreted in order to assess correctly the ballistic performance of ceramics.