Author: Kin Yit LeePublisher:
ISBN:
Category : Glass
Languages : en
Pages : 154
Book Description
Photoelasticity of Thermal Stresses and Temperature Measurement of Glass Under Thermal Stress
Author: Kin Yit LeePhotoelasticity of Thermal Stresses and Temperature Measurement of Glass Under Non-uniform Heating
Author: Che Hui PokPhotothermoelasticity Techniques and Application
Author: Warren E. GreenwaldPublisher:
ISBN:
Category : Photoelasticity
Languages : en
Pages : 28
Book Description
Photoelasticity of Glass Under Thermal Stress
Author: Fook Joo TeohPhotoelasticity of Glass
Author: Hillar AbenPublisher: Springer Science & Business Media
ISBN: 3642500714
Category : Technology & Engineering
Languages : en
Pages : 259
Book Description
Glass is the oldest man-made material. Its invention about five thousand years ago should be considered as one of the crucial events in the history of mankind. Glass has given man the possibility to have daylight in his protected living environment and to compensate the defects of his sight. Glass containers and tableware have played and still play an important role in man's everyday life. Glass elements in microscopes and telescopes have given us the possibility to learn the secrets of micro- and macrocosm. Glass participates in the most sophisticated technologies: glass fibers have caused a revolution in telecommunication, glass is used as a material for many modern electronic devices. Although nowadays plastics often make a strong competition to glass, for many applications glass is still the best material due to its specific properties - its hardness, good transparency, resistance to chemicals, the easiness to shape glass articles, feasibility to change the composition of the glass in order to meet new specific demands, etc. Two peculiarities of glass should be pointed out. The first is the fragility of glass - it breaks easily due to tensile stresses. The second is the fact that in every glass item there exist residual stresses due to the complicated technological process during which glass from the state of a viscous liquid at high temperature turns into solid state, while cooled down.
Thermal Stress Fracture of Optical Glasses
Author: Han LiuPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
"Since glass is brittle and thermally insulating, significant thermal stresses, especially in larger components often lead to catastrophic failure. Our work combines experimental measurement of glass thermomechanical failure, as well as computational simulations of transient thermal stresses arising in precision optical component used in fusion research. For the experimental work, we have quenched our samples and correlated the critical temperature difference for thermal shock with surface finish. We have estimated the heat transfer coefficient and the depth of the strength controlling cracks on the edge of disk samples. We have also carried out ring -on-ring biaxial strength tests to measure strength degradation of BK7 disks after thermal shock. For the simulation work, we have calculated thermal stress using both fin approximation and finite element analysis of quenched BK7 disks. The effect of cooling fluid has been examined. To examine the effects of size and glass properties, the radiative cooling processes of BK7 and LHG8 plates are also discussed. We have compared the temperature and thermal stress evolution of BK7 and LHG8 glass plates. Crack size evolution and crack growth rate have been computed. We have used three approaches to describe crack growth: the strength approach, the fracture toughness approach and the slow crack growth approach. The effect of linear variation of surrounding temperature and mitigation strategy are discussed. In this study we also examine in detail the effects of crack geometry near an edge. In addition, we have examined the thermal stresses induced by rinsing. Rinsing is a configuration in-between thermal shock and slow heating/cooling. The effects of rinsing parameters have also been investigated, especially as they affect surface tensile stresses. The main conclusions are the critical temperature drop for catastrophic failure is in the range 124 - 140 °C for surface prepared by lapping with alumina abrasives ranging in size from 5 [micrometers] to 40 [micrometers]. Samples with finer surface finish have better thermal shock resistance. There is no obvious strength degradation for BK7 glass disks and the retained strength depends on surface finish. Thermal shock tests in silicone oil show there is significant difference for retained strength after soaking in silicone oil which is evidence of chemical effect. The simulation results of radiative cooling process of BK7 and LHG8 glass show that BK7 plate is stronger than LHG8 plate and the maximum thermal stress occurs at the center of long edge. In addition, linear variation of ambient temperature with time is more detrimental than exponential decay. The mitigation strategy shows two conductive layers work best to reduce the maximum thermal stresses. Slow crack growth approach is used to calculate the crack size evolution. Stress intensity factor of three dimensional corner cracks is simulated and arbitrary crack shape is included. Our results show that even though initial crack fronts may have different length scales, the stress intensity factor is largest at the shorter length scale. The implication is that an edge crack eventually will grow to a quarter circular crack shape. Piranha rinsing process is simulated and compared with Piranha rinsing. Thermal stress follows temperature profile with delay. According to our simulation results water rinsing is more detrimental than Piranha rinsing."--Leaves iv-v
Photoelasticity of Glass Under Thermal Stress
Author: Kia Kit LowPhotoelasticity of Glass
Author: Hillar AbenPublisher:
ISBN: 9783642500725
Category :
Languages : en
Pages : 272
Book Description
This book presents a sytematic approach to contemporary phototelasticity with particular emphasis on stress analysis in glass. A review of different kinds of residual stresses in glass is presented. Besides traditional photoelastic techniques, differential refractrometry for stress determination on the surface of flat glass and integrated photoelasticity for stress determination in glass articles ofcomplicated shape are considered in detail. Original photoelastic apparatus and corresponding measurement techniques as well as stress calculation algorithms are described. Many practical examples illustrate the possibilities of modern photoelasticity for stress measurement in flat glass, containers, tumblers, tubes, optical fibres and fibre performs etc. The book can be considered as a textbook for a specialist in glass industry who wants to check the quality of products or tries to optimize theproduction process parameters from the point of view of the residual stresses. Furthermore, the book gives a number of new nondestructive methodswhich have not been described in earlier books on photoelasticity.
A Photoelastic Determination of Stress-intensity Factors Under Thermal Stresses
Author: Peizhong ZhangPublisher:
ISBN:
Category : Image analysis
Languages : en
Pages : 46
Book Description
Basic Optical Stress Measurement in Glass
Author: H. W. McKenziePublisher:
ISBN: 9780900682728
Category : Technology & Engineering
Languages : en
Pages : 100
Book Description
There are many texts dealing with photoelastic analysis and its applications, but they are not aimed specifically at the assessment of residual stresses in glasses. This publication offers a practical guide providing information on the various optical arrangements and interpretation of results from typical plant apparatus, it is of general interest to those making stress measurements within the glass industry.