Ceramic Backing Research Articles

Influence of backing materials towards the fatigue strength of butt-welded joints

The purpose of this study is to investigate the fatigue strength of butt-welded joints with special attention paid to employing different kinds of backing plates. The effect of the under-matched weld was also considered. Four different cases of backing scenarios for butt-welded specimens such as steel backing, ceramic backing, CMT (no backing by cold metal transfer) and UM (under-matched welded specimen) were investigated. A series of fatigue tests was performed to compare the fatigue strength of butt-welded joints with respect to different backing scenarios. Effective notch stress was used for the interpretation of fatigue strength of butt-welded specimens with backing plates based on finite element analyses for calculating fatigue notch factors. When results were presented from the effective notch stress, all backing scenarios considered in this study exhibited the fatigue strengths corresponding to the FAT 225 curve. From the experimental results of this study, it was determined that the fatigue strengths of butt-welded joints were found to be in the order of CMT, ceramic backing, UM, and steel backing. No significant decrease in fatigue strength, however, was observed when backing plates were steel backing and ceramic backing types.

Optimization of the procedure to burn textile fabrics by cone calorimeter: Part I. Combustion behavior of polyester

AbstractThe aim of this study was the optimization of cone calorimeter to determine the burning behavior of textile fabrics. In particular, the combustion behavior of commercial polyester textile fabrics with varying densities was studied in terms of time to ignition (TTI), heat release rate (HRR), and relative peak (pkHRR) were monitored. Reproducibility and repeatability of the data have been verified by the influence of instrument variable including incident heat flux, the temperature of ceramic backing pads and retaining grid used during sample mounting as well as sample weight (as the number of fabric layers), the density of textiles, and the relative humidity. A low reproducibility has been obtained when a wire grid was not used to stabilize samples during the tests. The effects of these variables on TTI and pkHRR were observed. Copyright © 2010 John Wiley & Sons, Ltd.

Back Bead Characteristics during Butt Welding of a Thick Plate for Various Backing Conditions

In a welded structure, thick plates are joined by multi-pass welding in the butt joint. During the first pass of multi-pass welding, burn-through, lack of fusion, and incomplete penetration were readily found as weld defects. Accordingly, the backing condition should be carefully selected in welding of a thick plate, because improper backing conditions lead to weld defects. In the job site, a steel backing strip is usually adopted, although it reduces the fatigue strength. No backing conditions or removable backing is recommended to increase the fatigue strength, but selection of the proper backing and welding conditions is complicated. In this study, several backing methods, such as ceramic backing, water-cooled copper backing, and even the use of no backing, were investigated during GMA (Gas Metal Arc) welding of a thick steel plate. The gas metal arc welding conditions were established for each backing method, and the bead shape and mechanical properties were examined after welding.

Soldagem unilateral com suporte cerâmico de cordierita

Este trabalho apresenta a avaliação de juntas soldadas com suporte cerâmico de cordierita produzido em laboratorio. Foi utilizada a técnica de soldagem unilateral em chapas de aço A-36 com espessuras de 6,4 e 15,8 mm pelo processo MIG-MAG. Com a chapa de 6,4 mm foi avalliado apenas o passe de raiz sobre o suporte cerâmico. Com a chapa de 15,8 mm foi produzida uma junta soldada em passes múltiplos. Após soldagem as juntas soldadas foram submetidas a ensaios de inspeção visual, liquido penetrante, macrografia, microdureza Vickers, microscopia ótica, ensaios de dobramento e de tração e análise química por EDS. Os resultados mostram que o passe de raiz, realizado sobre o suporte cerâmico, apresentou bom acabamento, isento de descontinuidades, com penetração adequada nas laterais do chanfro e reforço de solda apropriado. Em relação à junta soldada, a microestrutura da zona fundida (ZF) obteve predominância de ferrita primária, em suas formas de ferrita de contorno de grão e poligonal, e ferrita com segunda fase alinhada. A microdureza Vickers obteve valores médios abaixo de 180 HV tanto na zona termicamente afetada (ZTA) como na ZF. Os ensaios de dobramento não apresentaram descontinuidades maiores que 3 mm e nos ensaios de tração a ruptura ocorreu no metal base, indicando que o procedimento de soldagem foi adequado. A composição das inclusões tanto do passe de raiz como do ultimo passe de solda possuem os mesmos constituintes, apesar de proporções diferentes, indicando que não houve contaminação do material do suporte cerâmico no cordão de solda.

Soldagem unilateral com suporte cerâmico de cordierita

Este trabalho apresenta a avaliação de juntas soldadas com suporte cerâmico de cordierita produzido em laboratorio. Foi utilizada a técnica de soldagem unilateral em chapas de aço A-36 com espessuras de 6,4 e 15,8 mm pelo processo MIG-MAG. Com a chapa de 6,4 mm foi avalliado apenas o passe de raiz sobre o suporte cerâmico. Com a chapa de 15,8 mm foi produzida uma junta soldada em passes múltiplos. Após soldagem as juntas soldadas foram submetidas a ensaios de inspeção visual, liquido penetrante, macrografia, microdureza Vickers, microscopia ótica, ensaios de dobramento e de tração e análise química por EDS. Os resultados mostram que o passe de raiz, realizado sobre o suporte cerâmico, apresentou bom acabamento, isento de descontinuidades, com penetração adequada nas laterais do chanfro e reforço de solda apropriado. Em relação à junta soldada, a microestrutura da zona fundida (ZF) obteve predominância de ferrita primária, em suas formas de ferrita de contorno de grão e poligonal, e ferrita com segunda fase alinhada. A microdureza Vickers obteve valores médios abaixo de 180 HV tanto na zona termicamente afetada (ZTA) como na ZF. Os ensaios de dobramento não apresentaram descontinuidades maiores que 3 mm e nos ensaios de tração a ruptura ocorreu no metal base, indicando que o procedimento de soldagem foi adequado. A composição das inclusões tanto do passe de raiz como do ultimo passe de solda possuem os mesmos constituintes, apesar de proporções diferentes, indicando que não houve contaminação do material do suporte cerâmico no cordão de solda.

Image processing and control of weld pool in switch-back welding without backing plate

To achieve high quality in multilayer welding, it is important to obtain stable weld results for the first layer.1–5 For this reason, welding is usually conducted by using a backing of the same kind as the base material or a ceramic backing plate. In using a backing metal, the weight of the base material increases. Also it sometimes induces notches to occur at the weld joint between the base material and the backing. This can cause cracking. On the other hand, in using the backing plate, its removal is required after welding, and this makes the method unsuitable for automating the process. Therefore, in the authors' previous report, a proposal was made of the switch-back welding method in which welding is executed without using a backing plate, and also an investigation was made of the welding conditions for the root gap.6 In this welding method, it is necessary to adjust the wire feeding rate, the torch motion and the power property in accordance with the gap so that the back bead and the deposit can be controlled. Even if the gap is measured before welding, it may change owing to welding distortion. Hence, when welding is conducted by fixing the welding conditions, the change in the gap causes the back bead to become unstable. For this reason, in this study, a method is discussed to detect the gap on-line by processing images of the molten pool observed by a CCD camera. Then, using the results, the back bead was feed-forward-controlled in real time. Moreover, to examine the controlling performance, welding was conducted by varying the gap between 4.6 mm and 2.5 mm without tack welding. Very good weld results were obtained.

Ceramic Backing Materials Used in One-Side Welding Methods

Ceramic Backing Materials Used in One-Side Welding Methods

Ultrasonic transducers with functionally graded piezoelectric ceramics

Ultrasonic transducers used for measurement systems are required having a capability of generating a short time waveform ultrasonic pulse, i.e., a broadband frequency spectrum. In order to obtain the broadband transducer, functionally graded piezoelectric ceramics with a ceramic backing are fabricated and their ultrasonic performances are examined. Gradient of the piezoelectric parameter is realized by sintering a layer-structured ceramic green body composed of piezoelectric ceramic calcined powder layers with various compositions or composed of green sheets containing calcined powder mixed with some organic materials. It has been found that the above transducer generates an ultrasonic wave with a broader frequency spectrum compared with that of the conventional one.

Functionally Gradient Piezoelectric Ceramics for Ultrasonic Transducers

Ultrasonic transducers used for measurement systems are required to have the capability of generating a short-time waveform ultrasonic pulse, i.e., a broadband frequency spectrum. In order to obtain the broadband transducer, functionally gradient piezoelectric ceramics with a ceramic backing are fabricated and their ultrasonic performances are examined. The gradient of the piezoelectric parameter is realized by sintering a layer-structured ceramic green body composed of piezoelectric ceramic calcined powder layers with various compositions or composed of green sheets containing calcined powder mixed with some organic materials. It has been found that the above transducer generates an ultrasonic wave with a broader frequency spectrum than that of the conventional one.

Ultrasonic transducer with a ceramic backing

Ultrasonic transducer with a ceramic backing

RoSiB – a 4π silicon ball for charged-particle detection in EUROBALL

A 4π silicon ball for detection and identification of light charged particles in large multidetector γ-arrays as EUROBALL is presented. The design is based on a N=42 ball with 12 pentagons and 30 hexagons as used in the GASP array. The absorptive material for γ-rays is minimized to the detector thickness of 300 or 500 μm and a 0.63 mm ceramic backing. The geometrical coverage is designed for about 90% of 4π. A pulse shape discrimination method with totally depleted detectors working in the reverse mount allows identifying protons and α-particles above an energy threshold of about 2 MeV. The performances of the ball were tested at the tandem – booster accelerator combination of the MPI Heidelberg in two experiments using the high-recoil reaction of 228 MeV 58 Ni+ 46Ti and the low-recoil reaction of 95 MeV 16 O+ 58Ni . The two-dimensional spectra of zero-crossing (ZC) versus energy confirmed an excellent discrimination of protons and α-particles in all the detectors at different angles. The energy spectra of protons and α-particles measured in the experiments are presented, too. The γ-spectra measured in coincidence with various combinations of emitted particles showed a high selectivity of the ball. The reduced total efficiency for protons of 59% and 55% and α-particles of 44% and 32% measured in a nuclear spectroscopy application is analyzed in a Monte-Carlo simulation (GEANT). It is due to a combined influence of a thick target needed to stop the recoiling residual nuclei and thick absorbers needed to protect the Si-detectors from scattered beam. The results along with the GEANT extrapolation to optimum experimental conditions confirm that RoSiB is a highly efficient and selective device for identification of rare reaction channels with heavy ions.

Feasibility study of a portable PIXE system using a 210Po alpha source

An alpha source which consists of 1 mCi of 210Po electro-deposited on 1 μm thin Ag foil attached to a ceramic backing has been prepared. The overall geometry exhibits a truncated-conical shape. The source has been coupled to a standard 10 mm diameter Si(Li) X-rays detector connected to a portable electronic system (ORTEC-NOMAD). The analysed area of the exposed samples is 16 mm in diameter. Preliminary results state that medium-light elements, like Ca, Ti, Fe, Co, Cr, Ni and Cu can be easily analysed at concentrations of some per cent. Lighter elements determination is affected by the enhancing presence of X-rays generated in the Ag foil and by some chlorine impurities. PIXE measurements of attic greek pottery sherds are discussed.

An investigation into the effects of gravity level on rate of heat release and time to ignition

AbstractTwo experiments were performed on board an aircraft flying repeated parabolic trajectories to generate free‐fal conditions. The first experiment investigates the way in which rate of heat release (RHR) varies with gravity for a candle flame under an imposed low‐speed flow. In line with previous studies of flame spread rate it has been shown that rate of heat release drops significantly in imcrogravity. The heat loss due to radiation decreases by a larger proportion than that due to non‐radiative processes indicating a lower flame temperature. The RHR from a microgravity flame is flow rate dependent, increasing for increased flow rate at air speeds under 0.03 ms−1. For the geometry used in this experiment hypergravity caused only a small increase in RHR. The second experiment studied the ignitability of thermoplastics under an imposed radiant heat flux. The ignition test apparatus consists of a conical spiral heating element positioned horizontally above the sample, a continuous spark ignition source and a removable heat shield. Experiments were conducted in a sealed pressure chamber on samples of either PMMA or POM, 1.5 mm thick, with a ceramic backing. There is some indication that gravity influences the time to ignition for some materials.

In vivo imaging using a copolymer phased array

Phased-array images have been obtained in vivo with a steered copolymer array operating at 2.5 MHz. The array was fabricated using 28 μm copolymer film, λ/4 resonant at 21 MHz, which was bonded to a glass ceramic backing with a thin film bond. The 32 array elements were created by laser ablation of the continuous gold electrode on one side of the film. The transducer was driven by 200 V shock excitation, and the received signal was processed by 32 custom IC preamplifiers that were mounted to the array connector. The amplifiers had a high input impedance compared to that of the array elements and their output impedance matched that of the coaxial cable that connected to the scanner. Because the copolymer transducer had a broad bandwidth, the spectrum of the pulse echo image was modified by the frequency dependent attenuation of tissue and the bandpass of the ultrasound scanner, resulting in a center frequency of 2.5 MHz. The performance of the copolymer array was compared to that of a 3 MHz, PZT array with similar dimensions. On the Duke phased-array scanner, the copolymer sensitivity was 28 dB less than that of PZT. The copolymer elements had a 6 dB pulse-echo angular response of 30°, and the interelement cross-coupling was -35 dB. Phased-array images were made of the heart of a 25 year-old normal male.

In vivo imaging using a copolymer phased array.

Phased-array images have been obtained in vivo with a steered copolymer array operating at 2.5 MHz. The array was fabricated using 28 microns copolymer film, lambda/4 resonant at 21 MHz, which was bonded to a glass ceramic backing with a thin film bond. The 32 array elements were created by laser ablation of the continuous gold electrode on one side of the film. The transducer was driven by 200 V shock excitation, and the received signal was processed by 32 custom IC preamplifiers that were mounted to the array connector. The amplifiers had a high input impedance compared to that of the array elements and their output impedance matched that of the coaxial cable that connected to the scanner. Because the copolymer transducer had a broad bandwidth, the spectrum of the pulse echo image was modified by the frequency dependent attenuation of tissue and the bandpass of the ultrasound scanner, resulting in a center frequency of 2.5 MHz. The performance of the copolymer array was compared to that of a 3 MHz, PZT array with similar dimensions. On the Duke phased-array scanner, the copolymer sensitivity was 28 dB less than that of PZT. The copolymer elements had a 6 dB pulse-echo angular response of 30 degrees, and the interelement cross-coupling was -35 dB. Phased-array images were made of the heart of a 25 year-old normal male.

The effect of thermal-radiation heating on the hardening of epoxy enamels

A presentation is offered with respect to the considerations governing the mechanisms of thermal-radiation activity on a film of an epoxy enamel applied to a compound ceramic backing.