On the inhomogeneity of residual stresses in tempered glass panels

Anton, Johan; Errapart, Andrei; Paemurru, Mart; Lochegnies, Dominique; Hödemann, Siim; Aben, Hillar

doi:10.3176/eng.2012.1.01

Cited by 18 publications

(16 citation statements)

References 2 publications

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“…SCALP gets these surfaces stress information in a spherical volume with a radius of 0.5 mm from laser’s entrance point, that is, 0.5 mm could be the spatial resolution for surface stress measurement. At the SCALP laser beam’s entering point, the stress profile is calculated through the thickness with the dedicated software [13, 14]. The precision of the measured stress is ±2 MPa if the maximum absolute value is lower than 20 MPa and ±5% of the measure value for the case that the maximum absolute value is >20 MPa.…”

Section: Presentation Of the Industrial Tempering And Stress Measurementmentioning

confidence: 99%

“…To analyse with SCALP the non‐isotropic stress distribution in tempered glass, two measurements in the same location (i.e. in the same laser beam’s entering point) are required, making it necessary that SCALP is directed in two perpendicular orientations [14], which will be accomplished by the CNC machine with a 90° rotation around the z ‐axis.…”

Section: Presentation Of the Industrial Tempering And Stress Measurementmentioning

confidence: 99%

“…More recently, Anton et al. [14] have used SCALP to study the local and global inhomogeneities of the residual stress because of cooling jets in tempered glass panels [9]. They used SCALP manually to make stress measurement in different points or along one line.…”

Section: Introductionmentioning

confidence: 99%

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Measuring the 2D Residual Surface Stress Mapping in Tempered Glass under the Cooling Jets: the Influence of Process Parameters on the Stress Homogeneity and Isotropy

Chen

Lochegnies

Defontaine

et al. 2012

Strain

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In glass products, thermally tempered on industrial lines for automotive and architectural industries, the distribution of residual stress is highly inhomogeneous and, in certain situations, can produce optical defects that are more visible in sunlight because of the impact of the cooling jets on the hot glass during the tempering process. To analyse the influence of the process parameters on stress inhomogeneity, flat square glass samples were tempered with PRELCO tempering production unit without oscillation and with oscillation under cooling jets, thus reproducing the current industrial practice for the latter. To measure the residual stress distributions in the tempered glass samples, we developed a fully automatic system that combines the scattered light polariscope (SCALP) and a four‐axis machine, with three linear axes and one rotational one. Using the SCALP manually with the dedicated software makes it possible to access the glass surface at the laser beam’s entering point. With a four‐axis Computer Numerical Control (CNC) machine, we determined the 2D residual stress distribution under the cooling jets and analysed the influence of the cooling rate and oscillation on the homogeneity and the isotropy of the residual surface stress in the tempered glass samples.

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Section: Presentation Of the Industrial Tempering And Stress Measurementmentioning

confidence: 99%

Section: Presentation Of the Industrial Tempering And Stress Measurementmentioning

confidence: 99%

See 1 more Smart Citation

Measuring the 2D Residual Surface Stress Mapping in Tempered Glass under the Cooling Jets: the Influence of Process Parameters on the Stress Homogeneity and Isotropy

Chen

Lochegnies

Defontaine

et al. 2012

Strain

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“…This procedure, associated with the increase of the cooling rate, can strongly improve the homogeneity and isotropy of the stress distribution after tempering . Hence, if one considers the surface of heat‐treated glass plates produced with oscillations, the residual stress can be assumed to be equibiaxial, at least at a certain distance from the edges that, in general, result to be much more compressed than the core . It is customary to consider that, up to a distance of 15 mm from the edges, the state of stress is equibiaxial and homogenous in practice, thus neglecting, at least as a first‐order approximation, the inevitable point to point variation within a single specimen .…”

Section: The Modelmentioning

confidence: 99%

Statistical interference of material strength and surface prestress in heat‐treated glass

Pisano

Royer-Carfagni

2016

J Am Ceram Soc

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It is customary to assume that the characteristic design value for heat‐treated glass is represented by the sum of the characteristic values of the annealed glass strength and of the heat‐induced surface prestress, even though experiments have provided evidence that the resulting strength may be much higher. Here, we investigate the statistical interference between an assumed two‐parameter Weibull distribution for the annealed glass strength and a Gaussian distribution for the surface prestress. We show how the compound distribution confirms the experimental findings and, in particular, that the type of stress induced by the applied loads, ie, uniaxial vs biaxial, has an important role. This effect, which is more relevant for “weak” than for “strong” glasses, is the mechanical counterpart of the well‐known principle of diversification of investments in economy, and leads to a critical consideration of the design approach commonly suggested by structural standards.

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“…Figure 3 (right) shows the distribution of the thickness stresses near the surface of panel No. 8.Figure 4shows the relationship between the edge stress and the surface stress.Considering the inhomogeneity of the residual stress in tempered glass panels[ 8 ], the surface stress values inFig. 4are the average of 5 measurements.…”

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confidence: 99%