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| 2. |
- Harrysson, Ralph, et al.
(författare)
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Acoustic emission response of soda lime glass after a single Nd-YAG laser pulse
- 1994
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Ingår i: Journal of laser applications. - : Laser Institute of America. - 1042-346X .- 1938-1387. ; 6:3, s. 153-158
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Tidskriftsartikel (refereegranskat)abstract
- When machining brittle solids with a laser, crack formation can occur in the material around the irradiated area causing a strength reduction of the machined material. The purpose of this work was to study a well known brittle material (soda lime glass) by means of acoustic emission (AE) in order to investigate the correlation between visually observed crack formation and detected AE energy released by the crack formation in the material. During and after irradiation of soda lime glass with an Nd-YAG laser pulse, the number of hits and amount of AE energy were measured in the first 300 s using AE. It was found that it is possible to detect AE signals from cracks caused by irradiation with a single Nd-YAG laser pulse. The power of the detected signal is related to the amount of crack formation. Cracks can be minimized or avoided by choosing a suitable combination of pulse time and power density of the single laser pulse. The cracks which occur after a laser shot extend mainly in the radial direction from the irradiated area.
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| 3. |
- Harrysson, Ralph, et al.
(författare)
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Crack formarion during laser machining of ceramics detected by acoustic emission
- 1991
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Ingår i: Euro-Ceramics II. - : DKG. - 3925543112 ; , s. 671-675
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Konferensbidrag (refereegranskat)abstract
- During laser machining of ceramics, cracks can occur in the material around the irradiated area. These cracks reduce the strength of machined parts and may possibly hinder their use as an engineering material. It is therefore very important to establish methods for the detection and avoidance of crack formation. As an aid for detecting crack formation, the acoustic emission method was used for two materials: soda lime glass and sialon. The results have led to the conclusion that it is possible to detect a signal coming from a crack in the investigated material and that the power of the detected signal is due to propagation of the crack. The relationship between laser parameters and crack formation was found with the aid of acoustic emission signal analysis. It was also found that it is possible to minimise or avoid crack formation by choosing suitable laser parameters
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| 4. |
- Harrysson, Ralph, et al.
(författare)
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Glass formation in the system Y2O3-Al2O3-SiO2 under conditions of laser melting
- 1994
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 14:4, s. 377-381
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Tidskriftsartikel (refereegranskat)abstract
- Glass formation in the Y2O3---Al2O3---SiO2 system was investigated by means of laser melting using a CO2 laser source (wavelength 106 μm) with a maximum output power of 1700 W. The glass-forming region was found to be more extensive than that observed by other investigators. No glassy phase formed in compositions with less than 20 wt% SiO2. A non-equilibrium phase diagram corresponding to the conditions of laser-induced rapid melting and self-quenching was also determined. All the phases reported in the relevant binary diagrams with the exception of yttrium silicate 2Y2O3.3SiO2 were observed.
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| 5. |
- Sjögren, Torsten, et al.
(författare)
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High Performance Piston Rings for Two-Stroke Marine Diesel Engines
- 2004
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Ingår i: Proceedings // 24th CIMAC World Congress on Combustion Engine Technology.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The piston ring is a key component in a marine combustion engine. High mechanical loads, relatively high temperatures and corrosive gases and liquids influence its performance in terms of sealing capacity, wear of cylinder liner and the ring itself. Base material of the ring, coating technology and ring geometry design are discussed in the article.When tailoring cast iron materials suitable as piston ring base material two parameters are of importance; the morphology of the graphite and the constituents of the matrix. To optimize the properties of the cast iron a compromise is needed to achieve a satisfactory performance of the piston rings.Daros Piston Rings AB is currently developing a second generation of chromium-ceramic coating the so called Z-chrome. The objective of this project has been to increase the maximum operating temperature of the coating and leave the other characteristics of the coating unaffected. The difference between the commercial Daros coating Tritor® and the Z-chrome is the ceramic component included in the coated layer.Insufficient conformability of piston ring and liner geometry may produce a large local cylinder wall pressure which will destroy the oil film leading to uncontrolled wear and scuffing. Lack of conformability can also produce leakage paths for the combustion gases. Therefore a correct ring shape is of utmost importance. A new design philosophy designated OPCORE® has been developed and is presented here.
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| 6. |
- Vomacka, P., et al.
(författare)
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Crystallization behavior and hardness of ZrO2-free and ZrO2-containing glass-ceramics in the system Y2O3-Al2O3-SiO2
- 1997
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Ingår i: Scandinavian journal of metallurgy. - 0371-0459 .- 1600-0692. ; 26:3, s. 132-138
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Tidskriftsartikel (refereegranskat)abstract
- Background/aims: Y2O3 and Al2O3 are commonly used as sintering aids during sintering of silicon nitride based ceramics such as Si3N4 and sialon materials. These 2 oxides together with SiO2 present on the surface of Si3N4 particles form a liquid at elevated sintering temperatures and subsequently a glassy grain-boundary phase on cooling which causes a deterioration of the high temperature properties of the material. ZrO2 added to yttria-alumina-silica glasses is of interest as a potential nucleating agent which could shorten the incubation period of nucleation and increase the rate of nucleation. The objectives of the present study were to monitor the crystallization process in the Y2O3-Al2O3-SiO2 system by hardness measurements.Methods: A study has been made of the effect of crystallization on the hardness evolution in two glasses in the Y2O3-Al2O3-SiO2 system. The weight ratio of the three oxides in both glasses was 46.9 : 24.3 : 28.8 but one of the glasses was modified by the addition of 6 wt% ZrO2 which has a significant influence on the crystallization morphology. The progress of crystallization was monitored by means of X-ray diffractometry and by metallography.Results and conclusions: The crystalline phases in both materials were harder than the parent glasses but more so in the ZrO2 free material. The hardness increased with volume fraction crystallization but not linearly which suggests the influence of morphological factors such as crystal contiguity on hardness.
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| 7. |
- Vomacka, P., et al.
(författare)
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Crystallization of Y3Al5O12 from an Oxynitride Glass Monitored by High-Temperature X-Ray Diffractometry
- 1996
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 16:11, s. 1263-1269
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Tidskriftsartikel (refereegranskat)abstract
- It is well established that the glassy phase in a β-SiAlON material, with addition of Y2O3, can be crystallized to yttrium aluminium garnet (Y3Al5O12-YAG) by a post-sintering heat treatment. The crystallization of the YAG phase from an oxynitride glass with composition 46·1 wt% Y2O3, 26·3 wt% Al2O3, 21·6 wt% SiO2 and wt% Si3N4 was studied by means of high-temperature X-ray diffractometry. The kinetics of the crystallization were monitored in terms of the (420)) YAG peak area versus isothermal soaking time at 1150 °C during different heat treatments. The crystallization of the YAG phase was found to proceed as a surface crystallization. The results are relevant to developing improved crystallization treatments for glasses with potential for crystallization to YAG-based glass-ceramics and for heat treatments of YAG/β-SiAlON materials
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| 8. |
- Vomacka, P., et al.
(författare)
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Influence of Zirconia Addition on the Crystallization Kinetics of a Y-Si-Al-O-N Glass
- 1996
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 16:11, s. 1253-1262
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Tidskriftsartikel (refereegranskat)abstract
- The crystallization behaviour of YSiAlON glasses with and without ZrO2 additives, prepared by melting at 1700 °C, were studied by means of differential scanning calorimetry, scanning microscopy and X-ray powder diffraction analysis. The optimum nucleation temperatures were determined to be Tg + 65°C and Tg + 50 °C for the ZrO2-free and the ZrO2-containing glass, respectively. The crystallization of the glasses was found to be dominated by the surface mechanism of nucleation and growth. The added zirconia acted as a growth modifier rather than a nucleating agent.
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| 9. |
- Vomacka, P., et al.
(författare)
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Influence of ZrO2 Addition on Melting Kinetics of a YSiAlO Glass-Ceramic
- 1996
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 16:11, s. 1245-1251
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Tidskriftsartikel (refereegranskat)abstract
- A ZrO2-free YSiAlO glass of composition 27Y: 42Si:31Al in equivalent % and one with the addition of wt% ZrO2 were prepared in a nitrogen atmosphere at 1700 °C. These glasses were treated in a nitrogen atmosphere at a controlled rate, during which the glass partially crystallizes to form a glass-ceramic. Under continued heating melting occurs. This behaviour was monitored by differential thermal analysis, scanning electron microscopy and X-ray diffraction. The original dendritic appearance of the crystallized microstructures changed to a blocky one in the early stages of the melting process. The ZrO2 addition was found to increase the kinetics of the phase transformations occurring during the melting.
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| 10. |
- Vomacka, P.
(författare)
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Influence of ZrO2 addition on the crystallization of yttrium oxynitride glasses to Y3Al5O12-based glass-ceramics
- 1997
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Ingår i: Journal of the European Ceramic Society. - 0955-2219 .- 1873-619X. ; 17:4, s. 615-621
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Tidskriftsartikel (refereegranskat)abstract
- The influence of a ZrO2 addition (6 wt%) on the crystallization behaviour of a glass with potential for crystallization to Y3Al5O12-based glass-ceramics has been investigated. Differential thermal analysis, X-ray diffraction and scanning electron microscopy were used to assess the crystallization process. Vickers hardness was used to monitor changes in the crystallized volume fraction at different heat treatment temperatures. The results indicate that the addition of ZrO2 to the investigated glass composition promotes the formation of the y- Y2Si2O7 and inhibits the crystallization of the Y3Al5O12 phase
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