Friction measurement in precision glass molding: An experimental study

Mosaddegh, Peiman; Ziegert, John C.

doi:10.1016/j.jnoncrysol.2011.05.012

Cited by 18 publications

(19 citation statements)

References 16 publications

(19 reference statements)

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“…Internally at SCHOTT, it is used as a reference material. It was already used in several studies, but the rheological properties were never quantified experimentally in situ at pressures above 1‐atm. To quantify the viscosity of SCHOTT N‐BK7 ® glass, compared to (28) we use a totally different experiment set up by performing in situ deformation experiments in a gas‐medium pressure vessel.…”

Section: Introductionmentioning

confidence: 99%

Effect of pressure and temperature on viscosity of a borosilicate glass

et al. 2018

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During industrial glass production processes, the actual distribution of stress components in the glass during scribing remains, to date, poorly quantified, and thus continues to be challenging to model numerically. In this work, we experimentally quantified the effect of pressure and temperature on the viscosity of SCHOTT N‐BK7® glass, by performing in situ deformation experiments at temperatures between 550 and 595°C and confining pressures between 100 and 300 MPa. Experiments were performed at constant displacement rates to produce almost constant strain rates between 9.70 × 10−6 and 4.98 × 10−5 s−1. The resulting net axial stresses range from 81 to 802 MPa, and the finite strains range from 1.4% to 8.9%. The mechanical results show that the SCHOTT N‐BK7® glass is viscoelastic near the glass transition temperature at 300 MPa of confining pressure. To elucidate the data, we incorporated both 1‐element and 2‐element generalized Maxwell viscoelastic models in an inversion approach, for which we provide MATLAB scrips. Results show that the 2‐element Maxwell model fits the experimental data well. The stress decreases with increasing temperature at 300 MPa and the temperature dependence yields a similar activation energy (601 ± 10 kJ mol−1 or ∆H/R = 7.2 × 104 K) to a previously reported value at 1‐atm (615 kJ mol−1 or ∆H/R = 7.4 × 104 K). The SCHOTT N‐BK7® glass shows a limited linear increase in viscosity with increasing pressure of ~0.1 log10 (Pa·s)/100 MPa, which is in agreement with the most recent 2‐internal‐parameter relaxation model (based on experiments).

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Section: Introductionmentioning

confidence: 99%

Effect of pressure and temperature on viscosity of a borosilicate glass

et al. 2018

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“…27 This is the initial motivation to the development of several experimental and computational methods concerning friction evaluation. 27 This is the initial motivation to the development of several experimental and computational methods concerning friction evaluation.…”

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confidence: 99%

“…A good knowledge of glass-mold interface friction is invariably needed in accurate modeling of glass forming processes such as precision molding. 27 This is the initial motivation to the development of several experimental and computational methods concerning friction evaluation. Mossaddegh and Ziegert conducted double-sided shear tests at elevated temperatures, whereby the friction coefficient between the coated tungsten carbide (WC) mold and glass N-BK7 was directly measured as 0.6-0.7.…”

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confidence: 99%

“…Mossaddegh and Ziegert conducted double-sided shear tests at elevated temperatures, whereby the friction coefficient between the coated tungsten carbide (WC) mold and glass N-BK7 was directly measured as 0.6-0.7. 27 Ananthasayanam et al investigated the glass-mold frictional behavior via ring compression tests, where a universal set of friction calibration curves were obtained by numerical iterations, which allowed for a reliable friction evaluation without the need for knowing the material properties. 12,13,28 Considering the temperature dependence, Sarhadi et al evaluated the glass-mold interface friction through ring compression tests at several temperatures.…”

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confidence: 99%

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A comprehensive study on frictional dependence and predictive accuracy of viscoelastic model for optical glass using compression creep test

Luo

Zhang

et al. 2019

J Am Ceram Soc

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Compression creep tests (CCTs) have been widely used in phenomenological characterization of viscoelastic materials such as glasses. However, disturbed by specimen‐tool interface friction, the real stress‐strain data regarding the pure viscoelastic deformation are frequently misestimated in conventional CCTs, causing decreased accuracies of the derived viscoelastic parameters. This study proposes a comprehensive CCT‐based approach to develop a viscoelastic model with weakened frictional disturbance and enhanced predictive accuracy. An integrated calculation procedure is first built to mathematically characterize the frictional and viscoelastic behaviors of glass during compression. Uniaxial CCTs of a typical borosilicate glass (L‐BAL42) are then performed at varied frictional conditions. The quantified coefficients of interface friction indicate that a minor frictional disturbance is achieved when Nickel foils are used as interfacial layers, whereby a more realistic viscoelastic constitutive relation of the glass is derived. The obtained frictional and viscoelastic constants are further incorporated into computational modeling of the CCT and precision molding processes. The demonstrated consistencies between the simulated and measured results (creep displacement and molding force) suggest that, by technically slashing the interface friction and theoretically correcting the friction‐involved stress in CCTs, the frictional disturbance to experimental stress‐strain data can be effectively weakened, and a viscoelastic model of enhanced predictive accuracy can be thus developed.

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“…A sleeve around the lower mold and mold tooling is utilized to align the upper and lower molds which are made of tungsten carbide (WC). The WC is used because of its robust mechanical and thermal properties at higher temperatures [8]. Alternative mold/insert materials can be employed as needed for the desired glass type/heating method/temperature range; however, the present work only describes finding for WC with L-BAL35 glass.…”

Section: Mechanical Systemsmentioning

confidence: 99%

Performance Evaluation of a Bench-Top Precision Glass Molding Machine

Wachtel

Mosaddegh

Gleason

et al. 2013

Advances in Mechanical Engineering

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A Dyna Technologies Inc. GP-5000HT precision glass molding machine has been found to be a capable tool for bridging the gap between research-level instruments and the higher volume production machines typically used in industry, providing a means to apply the results of rigorous instrumentation analysis performed in the lab to industrial PGM applications. The GP-5000HT's thermal and mechanical functionality is explained and characterized through the measurement baseline functionality and the associated error. These baseline measurements were used to determine the center thickness repeatability of pressed glass parts, which is the main metric used in industrial pressing settings. The baselines and the repeatability tests both confirmed the need for three warm-up pressing cycles before the press reaches a thermal steady state. The baselines used for pressing a 2 mm glass piece to a 1 mm target center thickness yielded an average center thickness of 1.001 mm and a standard deviation of thickness of 0.0055 mm for glass samples pressed over 3 consecutive days. The baseline tests were then used to deconvolve the sources of error of final pressed piece center thickness.

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Friction measurement in precision glass molding: An experimental study

Cited by 18 publications

References 16 publications

Effect of pressure and temperature on viscosity of a borosilicate glass

Effect of pressure and temperature on viscosity of a borosilicate glass

A comprehensive study on frictional dependence and predictive accuracy of viscoelastic model for optical glass using compression creep test

Performance Evaluation of a Bench-Top Precision Glass Molding Machine

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