Tempered Glass Research Articles

Assessment of Stresses in Float and Tempered Glass Using Eigenstrains

Residual stress data determined using the contour method has been used to determine the misfit-strains (i.e., eigenstrains) existent in float glass. Although the uncertainty associated with the results of the contour method analysis may be high the results agree with the residual stress profiles measured using scattered-light-polariscope experiments. The relationship between the eigenstrains and the thickness of glass has been investigated and the results have been validated using scattered-light-polariscopic experiments. The paper shows that the eigenstrain distribution depends on the differential cooling takes place during the manufacturing process. Once the underlying eigenstrain distribution in a given float glass product has been determined this can be used to devise the eigenstrain distribution in tempered glass. It is also shown that eigenstrain analysis can be implemented in finite element models to predict structural response of glass structures thereby to ensure efficient, safe and reliable designs.

Study of Aluminum Oxide Abrasive on Tempered Glass in Abrasive Jet Machining Using Taguchi Method

The abrasive jet machining (AJM) is a non-conventional machining process in which a abrasive particles are made to impinge on the work material at a high velocity. The jet of abrasive particles is carried by carrier gas or air. The high velocity stream of abrasive is generated by converting the pressure energy of the carrier gas or air to its kinetic energy . The high velocity abrasive particles remove the material by micro-cutting action as well as brittle fracture of the work material . Abrasive jet machining is generally good for cutting hard or brittle materials and is usually performed to furnish machining or finishing operation such as cutting, deburring, etching, etc. This project deals with the fabrication of the Abrasive Jet Machine and machining on tempered glass, calculating the material removal varying various performance parameters like pressure, angle abrasive grit size so on. Before performing the experiment ,fabrication done on AJM which are also discussed.. The different problem faced while machining on tempered glass are also discussed.Taguchi method and ANOVA is used for analysis of material removal rate .

The Entrepreneur's Dilemma: Case of TMT Toughened Glass Pvt. Ltd.

TMT Toughened Glass Company is in the glass processing industry. This industry requires a high level of innovation and expertise to process glass which is a very fragile and unworkable material. Customers typically want complete and technically sound solutions to their security, structural, design and architectural needs where glass is a material of choice. Shiv Prasad, the Managing Director of TMT Toughened Glass Company Pvt. Ltd., likes to call himself a “Glass Fabricator” and has been the pioneer in finding innovative solutions to glass processing needs in India. Tempering is the core process in this. Manufacturers of float glass are the suppliers and real estate developers and builders, automobile manufacturers and industrial appliance manufacturers are its buyers. Growth in this industry has been fuelled by the economic boom in India. The industry is largely unregulated. The number of players in the industry has increased to 40 in the same period from a mere 10. While the demand in the glass processing industry is growing at a steady rate of 30%, the capacity is growing at a compound annual growth rate of almost 80%. Prasad's competence is in engineering and design innovation. The dilemma he faces is whether to carry on with his time-tested strategy of innovation led growth or follow what other industry players are doing. Prasad has the option of concentrating his resources on doing what he does best — finding innovative solutions to the glass processing needs of his customers. The central question for Prasad is how to ensure that TMT Toughened Glass outperforms others on a sustained basis. Out of several options, this case explores the option of expanding the product line to include processed glass for the passenger car segment.

Difference of cracking behavior due to Vickers indentation between physically and chemically tempered glasses

Crack formation phenomena for the thermally and chemically tempered commercial soda-lime float glasses were investigated by using an indentation method. Since crack formation generally can be related with stress around an indent, the crack initiation load and the residual stress generated around the indent were measured using Vickers indentation method and a birefringence imaging system, respectively. In the case of thermally tempered glass, the crack initiation load became higher than on the original glass, whereas in the case of chemically tempered glass, the load became higher than on the original glass only when the surface stress was higher than a critical stress. The size of the residual stress field normalized by the indent size was smaller in the thermally tempered glass and larger in the chemically tempered glass than that in the original glass. The cracking resistance of both tempered glasses can be related to the residual stresses generated in the glass.

Laser sheet scattered light method for industrial measurement of thickness residual stress distribution in flat tempered glass

The paper presents the laser sheet scattered light technique, a fast optical non contact method for measuring internal stress distribution over a cross section of flat glass specimens, designed for closed loop control of glass tempering furnaces. The technique is an evolution of the scattered light method for flat glass residual stress analysis and allows a full thickness stress profile to be measured with a single shot acquisition across a glass plate without any contact. A linearly polarized laser sheet, shaped into a thin plane of parallel light beams, enters orthogonally to the side of the flat glass illuminating its full thickness. Light sheet is orthogonal to the glass surface and travels parallel to it. Stress induced birefringence through the glass affects light polarization, thus scattered light intensity detected at 90° with respect to the polarization of the incident light appears spatially modulated in intensity. A camera aligned orthogonal to the laser light polarization collects an image of fringes whose shape is digitally analyzed to measure the thickness stress state. The paper describes the development of this technique by recalling the scattered light method, then describing its automation by scanning a collimated beam across the glass thickness and finally by showing that the scan method can be substituted by the light sheet method. Light sheet method provides a full field non contact stress measurement across the glass thickness, thus allowing for a fast inspection method, suitable for industrial use. Flat glass items for industrial use have bevelled edges; this does not allow measurements close to glass surface. To solve this limit, experimental data are extrapolated by a symmetrical polynomial fitting and imposing a zero integral to the stress profile. Results on surface stress measured by the laser sheet scattered method are in agreement with those of the automated light scattered method and show a fair agreement with measurement by an epibiascope, thus proving the applicability of the method for fast and contact-less detection of residual thickness stress; the industrial application of the method is outlined, so that a tempering furnace could be controlled using feed-back data from thickness stress measurements on flat glass.

USING TEMPERED GLASS AS A REPLACEMENT OF ASPHALT CONCRETE WEARING COURSE

USING TEMPERED GLASS AS A REPLACEMENT OF ASPHALT CONCRETE WEARING COURSE

New processing possibilities for highly toughened metallic glass matrix composites with tensile ductility

New processing possibilities are explored for a semi-solidly-processed bulk metallic glass matrix composite based on the ZrTiNbCuBe system. Thermoplastic processing in the supercooled liquid region, extensive room temperature cold-rolling, and tensile ductility with work-hardening are all achieved. This research demonstrates that bulk metallic glass matrix composites have potential that far exceeds high tensile ductility and ultra-high toughness.

Evaluation of Crack Growth Characteristics in Float Glass and Thermally Tempered Glass Based on the Crack Length Measurement Using Au Ion Sputtered Film

Thermal tempered glass is made by rapidly cooling after heating float glass to near the softening point. Compressive residual stresses at the surface layer of thermally tempered glass strengthen the material, and tensile residual stresses are also generated at the same time in the interior of the material to balance with the surface compressive residual stresses. It is considered that the fatigue crack growth characteristics of thermally tempered glass are remarkably different from that of float glass, due to the existence of those residual stresses. In this study, Au film made by ion sputtering method and an optical microscope are used to measure the crack length of the thermally tempered glass and float glass, and these fatigue crack growth characteristics are investigated. As a result, it is confirmed that the crack length measurement with an Au film has high accuracy of measurement. Furthermore, it is found that the higher stress intensity factor is needed to cause the crack growth in thermally tempered glas than in flat glass.

An electron microscopic study of nickel sulfide inclusions in toughened glass

It has been known since the early sixties that nickel sulfide inclusions cause spontaneous fracture of toughened (thermally tempered) glass, but despite the considerable amount of work done on this problem in the last four decades, failures still occur in the field with regularity. In this study we have classified (by viewing through a 60× optical microscope) inclusions into two groups, which are “classic” and “atypical” nickel sulfides. The “classics” look like the nickel sulfide inclusions found at the initiation-of-fracture of windows that have broken spontaneously. We have compared the structure and composition of the “atypical” inclusions with the structure and composition of the “classics”. All of the “classic” and “atypical” nickel sulfide inclusions studied in this work were found to have a composition in the range of Ni52S48to Ni48S52. Inclusions on the nickel rich side of stoichiometric NiS were found to be two-phase assemblies, and inclusions on the sulphur rich side of NiS were single phase. It had been proposed that the “atypicals” were passive, and of a different composition to the “classics”. However, we found that the difference between passive and dangerous nickel sulfide inclusions was not a difference in composition but rather a difference in the type of material in the internal pore space. The passive's had carbon char in their internal pore space, whereas the pore space of dangerous inclusions contained Na2O. The presence of Na2O and carbon char with the inclusions indicates that the formation of the inclusions results from a reaction of a nickel-rich phase with sodium sulphate and carbon.

717 熱強化ガラスの静疲労及び動疲労特性(G.S. 材料力学 : 衝撃応答その他)

717 熱強化ガラスの静疲労及び動疲労特性(G.S. 材料力学 : 衝撃応答その他)

TRE LETTERE DI GEMINIANO MONTANARI A GIAN DOMENICO CASSINI *

Abstracttitle SUMMARY /title Here are been transcribed three letters sended by Geminiano Montanari to Gian Domenico Cassini. The first two, written in 1669, deal with his experiments with different types of tempered glass and with the tears or gocciole e vermicelli di vetro che rotti in qualunque parte si stritolano d'un subito in minuta polvere. The third, dated 1673, regards mainly the inspections made by Montanari on the S. Petronio sundial in Bologna.

Quasi-static indentation cracking of thermally tempered soda-lime glass with spherical and Vickers indenters

Abstract An experimental study of the indentation cracking behaviour of thermally tempered soda-lime glass flats is described. The indenters were steel and tungsten carbide spheres of radii in the range 0·5 to 2·5 mm and a Vickers diamond pyramid. They were loaded normally on to the flats and particular attention was paid to the evolution (i.e. initiation and growth) of the Hertzian cone cracks formed under the spherical indenters and to the median cracks which were generated under the Vickers indenter. With the spherical indenters, the Hertzian ring‐cone cracks have been shown to initiate most frequently at the circle of contact between the indenter and the specimen surface. Moreover, with increasing indenter load, the skirt of the cone crack has been found to extend almost parallel to the indented surface; this is shown to be consistent with the principal stress trajectories within the tempered glass. The implication of such cone cracks for the strength degradation of the tempered glass is discussed. Within the range of spherical indenter sizes studied, it has been found that in the tempered glass the critical load required to cause a ring-cone fracture is proportional to the indenter radius. A comparison of these observations with those from the same glass specimens, but this time in an annealed state, has also been made. By employing a simple analysis, the surface compressive stress in the tempered glass has been determined to be 280 ± 180 MPa. Under the Vickers indenter, a full penny-shaped median crack has been found to form in the tempered glass at a sufficiently high load. During loading, the shape of this crack remains approximately unaltered with increasing indenter load. During unloading, the penny-shaped median crack becomes like a half-penny. On the other hand, in the annealed glass, the penny-shaped median crack clearly changes into the half-penny shape with increasing indenter load during the loading cycle. Also, in both types of glass shallow radial cracks have been observed to initiate during loading as well as during unloading. From measurements of the surface extent of the median-radial cracks in the thermally tempered glass and in the annealed glass, a second method of analysis has also been employed to estimate the magnitude of the surface compressive stress in the former. This method has given a value of 60 ± 5 MPa for the compressive stress, which is considerably smaller than that determined using the spherical indenters. A brief discussion of the possible reasons for the discrepancy is given.

The production of toughened glass

The production of toughened glass

熱強化ガラス板の残留応力

熱強化ガラス板の残留応力

Instability of toughened glass: Anon., New Scientist, 16 (311), 1 Nov. 1962, 266.

Instability of toughened glass: Anon., New Scientist, 16 (311), 1 Nov. 1962, 266.

Rectifier Plant in Time of War

IT has been doubted by some engineers whether the glass bulb devices used in some electric stations for converting alternating into direct current are able to withstand the blast and other effects of aerial bombing. It has to be remembered that the bulbs, being spherical, present a minimum surface to blast contact. They are flexibly mounted and are made of a special toughened high-grade glass. They are always operating under an external atmospheric pressure of approximately 15 lb. per sq. in. (as the bulbs are various). This is equivalent to a total pressure of about 20 tons in the case of a large rectifier bulb and so its inherent strength is very considerable. It has been computed that one ton of high explosive will cause a blast pressure of about 2½ lb. per sq. in. at 100 yd. distance. Such a pressure might be sufficient to knock down a 9-in. brick wall (because of the large resistance surface it presents), for 2½ lb. per sq. in. is the equivalent of 1½ tons per sq. yd. A rectifier bulb is always working at 15 lb. per sq. in. and can withstand many times this amount.

Condensers of tempered glass

Condensers of tempered glass