Soda-lime Glass Specimens Research Articles

Modeling brittle crack propagation for varying critical load levels: a dynamic phase-field approach

AbstractBrittle materials are known for their violent and unpredictable cracking behavior. A behavior which is dictated by a combination of microscopical material defects and the competition between the potential energy of the system and the surface energy of the material. In this study, we present the implementation of a dynamic fracture phase-field model with a new crack driving force into a commercial finite element (FE) solver and examine its behavior using three different tension-compression splits. After validating the implementation, we use the model to investigate its predictive capacity on quasi-statically loaded L-shaped soda-lime glass specimens with varying critical load levels. The dynamic fracture phase-field model predicted similar crack propagation to what was found in the literature for quasi-static and dynamic validation cases. By varying the critical load level for the L-shaped soda-lime glass specimens using the new crack driving force, the model predicted a positive correlation between the initial crack propagation speed and the critical load level, similar to what was seen in the experiments. However, the predicted crack propagation speed decreased quicker than the experimental crack propagation speed. The tension-compression splits had an impact on the predicted crack propagation paths. Overall, the proposed crack driving force used in the dynamic fracture phase-field model seems to capture the relation between critical load and initial crack propagation speed and thus enables crack predictions for specimens of varying strength.

Effect of load level on cracking of L-shaped soda-lime glass specimens

Soda-lime glass is a brittle and transparent material that is known for its rapid and sudden fracture behavior. Since the use of soda-lime glass in protective structures is increasing, a more comprehensive understanding of this challenging fracture behavior is needed. The aim of this work is to investigate how the load level affects the crack propagation and to generate an experimental database for L-shaped soda-lime glass specimens with curved crack paths. We designed a repeatable testing procedure which reveals the crack propagation behavior of the specimen and allows for extraction of valuable experimental data. A total of 20 experiments were conducted on L-shaped soda-lime glass specimens subjected to a controlled displacement. High-speed cameras were used to monitor the crack propagation and the high-speed footage was post-processed using an in-house procedure to extract the crack path and speed data. We found a positive correlation between the measured initial crack speed and the load level at fracture. The crack propagation path followed four distinct stages and was also affected by the load level at fracture. With this experimental database, we have provided important insight into how the load level affects the crack propagation in soda-lime glass.

Static and dynamic strength of soda-lime glass under combined compression-shear loading

A modified method was employed to investigate failure of the soda-lime glass under combined compression-shear loading condition based on Split Hopkinson Pressure Bar. With double beveled ends loading blocks, shear component was introduced into the specimen, maximum ratio of which to normal stress was more than 40%. Both quasi-static and dynamic tests were conducted on soda-lime glass specimens in four different loading directions: 0°, 15°, 30° and 45°. With carefully pulse shaping, the dynamic equilibrium of the specimens and constant strain rate loading were satisfied. The progressive failure processes of the specimen illustrated via high-speed photographs manifested that axial splitting failure mode is dominated under both uniaxial compression and combined compression-shear loading. The non-axial cracks observed in combined compression-shear experiment resulted in the strength decline of specimen. Experimental results demonstrated an evident that the strength of soda-lime glass is strain rate and loading path dependent. A power law function was fitted to accurately describe the relationship between equivalent strength and strain rate. Failure surfaces at various strain rates were constructed, which allow us to have a further understanding of dynamic response and failure mechanism of inorganic glass under complex stress states.

Enhancement of the analytical solution for double torsion test using extended finite element techniques

The double torsion (DT) testing technique is not yet standardized for fracture mechanics characterization of brittle materials because previous analytical solutions are insufficient to represent accurate load-displacement (P-h) relationship and stress intensity factor (SIF) in experiments. Therefore, we attempt at enhancing the analytical solutions based on three-dimensional extended finite element (XFE) analysis to obtain reproducible results from DT tests. As a result, the P-h relationship in DT test can be efficiently described by combining the bending deformation of a DT specimen with torsional deformation. Weighting factors are proposed as functions of thickness, moment arm and crack length. DT experiments are conducted with sodalime glass specimens to further validate the proposed weighting factors. Finally, correction terms are provided for SIF and fracturs toughness evaluation in DT specimen with straight and curved crack fronts. Fracturs toughness values of sodalime glass specimens with various thickness are consistent, and in good agreement with literature values.

Spherical indentation for brittle fracture toughness evaluation by considering kinked-cone-crack

This work aims at evaluating the fracture toughness of brittle materials by spherical indentation. The cone-cracking is simulated by the extended finite element method (XFEM) in Abaqus. The formation of a kinked-cone-crack is observed when the indenter comes into (second) contact with the surface part outside the ring-crack. The effects of friction, Poisson’s ratio and cone-crack kinking on the Roesler’s constant κc are analyzed. Based on numerical results, the Roesler’s method for evaluating the fracture toughness is enhanced by considering kinked-cone-crack. By performing systematic XFE analyses, a database for enhanced Roesler’s constant κc | kink is provided for the fracture toughness evaluation of brittle materials. Finally, the proposed method is verified by conducting spherical indentation tests on soda-lime glass specimens.

Wear Behaviour of Nanostructured Polymer-Based Safety Films on Soda-Lime Glass

The wear behaviour of bare and polymer-coated soda-lime glass specimens sliding against 440C stainless steel counterfaces was investigated with the aid of a pin-on-disk apparatus. The selected polymeric coatings were commercially supplied safety films, which are nowadays extensively applied on glass in the automotive and construction industry. One of their main failures is the degradation of their properties due to wear. In this work, the frictional behaviour of these coatings on glass were evaluated and compared to those of bare soda-lime glass. Correlations have been also made between the worn surfaces and weight loss in order to investigate the effect of wear conditions (speed, load) on the wear behaviour of these tribosystems. In addition, during the dry wear of soda-lime glass sliding against stainless steel counterfaces, the dominant wear mechanisms were found to be localized adhesion and abrasion, whereas, in the case of the multilayered polymeric coatings localized adhesion, deformation and tearing were observed.

Dynamic material model of annealed soda-lime glass

Glass is an omnipresent material which is widely used as façade in buildings. Damage of glass windows and the associated glass fragments induced by impact and blast loads impose great threats to people in the vicinity. Much effort has been directed towards understanding glass material properties, and modeling of glass window responses to impact and blast loads. For reliable predictions of glass structure performances under dynamic loadings, an accurate dynamic constitutive model of annealed float glass, which is commonly used for glass windows, is therefore needed. In current practice, the Johnson-Holmquist Ceramic (JH2) model is most commonly used in simulating glass plate responses to impact and blast loads. In this study, the accuracy of the JH2 model in modeling annealed float glass material, especially at high strain rate is examined in detail. Static compressive tests and dynamic compressive tests using Split Hopkinson Pressure Bar (SHPB) are carried out on soda-lime glass specimens sampled from commercially used annealed float glass panes. These testing results are used together with the authors' previous testing data and data reported by other researchers in the literature to determine the constitutive constants for the JH2 model, including Equation of State (EOS), strength criterion and strain-rate effect. The JH2 model with new material constants is then programmed in commercial code LS-DYNA. To verify the model, it is used to simulate a SHPB compressive test on a 15 mm by 15 mm (diameter by length) glass specimen, a field blasting test on a laminated glass window of 1.5 m by 1.2 m in dimension, and a full-scale laboratory windborne debris impact test on a laminated glass window. The simulation results demonstrate that the JH2 model with the new material constants for annealed glass gives good predictions of glass material and glass window responses to impact and blast loads.

Testing rate and cementation seating load effects on resin-strengthening of a dental porcelain analogue

ObjectivesTo determine the resin-strengthening dependence of a soda-lime-glass analogue for dental porcelain as a function of biaxial flexure strength (BFS), test crosshead rate and cementation seating load. MethodsDisc-shaped soda-lime glass specimens were divided into twelve groups (n=24), alumina particle air abraded and hydrofluoric acid-etched. Specimens (Groups A–D) were stored in a desiccator prior to testing at crosshead rates of 0.01, 0.1, 1 and 10mm/min, respectively. The remaining specimens were silane treated, Rely-X Veneer resin-coated with a seating load of 5N (Groups E–H) and 30N (Groups I–L) prior to light irradiation at 480±20mW/cm2, 24h dry storage and BFS testing at 0.01, 0.1, 1 and 10mm/min, respectively. A linear logarithmic regression curve was fit to the raw data to elucidate static fatigue effects of the soda-lime-glass. Analysis of group means was performed utilising a general linear model univariate analysis and post hoc all paired Tukey tests (P<0.05). ResultsThe linear logarithmic regression curve demonstrated the static fatigue effects of the soda-lime-glass analogue. Rely-X Veneer resin-coating (Groups E–L) resulted in significant increases in the mean BFS data for all crosshead rates examined (all P<0.001). However, the pattern of rate dependence effects on resin-cementation deviated from the log relationship observed with the uncoated controls. ConclusionThis study further highlights that when slow crack growth is simulated during testing, valuable insights into the significant modification of a hereto well described phenomenon such as resin-strengthening mediated by the resin–ceramic hybrid layer is provided.

Can a soda-lime glass be used to demonstrate how patterns of strength dependence are influenced by pre-cementation and resin-cementation variables?

ObjectivesTo determine how the variability in biaxial flexure strength of a soda-lime glass analogue for a PLV and DBC material was influenced by precementation operative variables and following resin-cement coating. MethodsThe flexural modulus of a transparent soda-lime glass was determined by longitudinally sectioning into rectangular bar-shaped specimens and the flexural moduli of three resin-based materials (Venus Flow, Rely-X Veneer and Clearfil Majesty Posterior) was also determined. Disc shaped soda-lime glass specimens (n=240) were divided into ten groups and were alumina particle air abraded, hydrofluoric (HF) acid-etched and resin-cement coated prior to biaxial flexure strength testing. Sample sets were profilometrically evaluated to determine the surface texture. One-way analyses of variance (ANOVA) and post hoc all paired Tukey tests were performed at a significance level of P<0.05. The mean biaxial flexure strengths were plotted against resin-coating thickness and a regression analysis enabled estimation of the ‘actual’ magnitude of strengthening. ResultsThe mean three-point flexural modulus of the soda-lime glass was 40.0 (1.0)GPa and the Venus Flow, Rely-X Veneer and Clearfil Majesty Posterior were 3.0 (0.2)GPa, 6.0 (0.2)GPa and 14.8 (1.6)GPa, respectively. At a theoretical ‘zero’ resin-coating thickness an increase in biaxial flexure strength of 20.1% (63.2MPa), 30.8% (68.8MPa) and 36.3% (71.7MPa), respectively was evident compared with the control (52.6 (5.5)MPa). ConclusionsDisc-shaped specimens cut from round stock facilitated rapid fabrication of discs with uniform surface condition and demonstrated strength dependence was influenced by precementation parameters and resin-cementation variables.

Effect of Crack Length on Crack Growth Characteristics in Glass Ceramics and Soda-Lime Glass

New crack length measurement methods using thin metal film were proposed in order to evaluate the crack growth characteristics during static fatigue process of ceramics. Also, the effect of crack length on the crack growth characteristics was investigated using both soda-lime glass and glass ceramics specimens. As the results, it was found that in the soda-lime glass, there is no difference between small- and long-crack growth characteristics. On the other hand, in the glass ceramics, it was found that sub-critical crack growth (SCG) resistance in small-crack propagation test is higher than that in long-crack propagation test. In addition, it is confirmed that the glass ceramics has higher SCG resistance than that in the soda-lime glass. Furthermore, it was confirmed that the proposed crack length measurement method is suitable for crack growth characteristics evaluation on ceramics.

Experimental Research on Failure Waves in Soda-Lime Glass

A series of plate impact experiment with soda-lime glass specimens in different thicknesses are conducted on a 57 mm diameter one-stage gas gun in order to further investigate the so-called failure wave phenomena under dynamic compressive loads. With the aid of the VISAR technique, the failure wave trajectory is explored, which shows that, apart from a constant failure wave velocity, an initial delay time for the failure wave to initiate at the impact surface of the specimen should be taken into consideration. Comparing our experimental results with the available data presented in the previous open literature shows that, with the increasing magnitude of the impact loads, the failure wave velocity increases and the initial delay time decreases. Moreover, the derived initial delay time τ = 0.694 μs for the soda-lime glass specimens under the impact stress of 4.7 GPa is the same order of magnitude as that of the incubation time proposed by Morozov and Petrov (2000), which shows that the incubation time plays a dominant role in the total initial delay time, and it also provides an reasonable explanation to the fundamental question pointed out by Clifton (Appl Mech Rev 46: 540-546, 1993).

More on the behavior of soda lime glass under shock loading

A series of plate impact experiments with soda-lime glass specimens was performed in order to further investigate the complex behavior of this material in the 0–8 GPa range of shock loading. Using commercial manganin gauges we followed the stress histories and their different shapes as the stresses increase from 3.5 to about 8.0 GPa. In particular, we find that there are meaningful differences between the shapes of these signals at pressures below about 4.0 GPa, in between 4.0 and 6.0 GPa and above 6.0 GPa. We also gather more data on the fractured glass behind the fracture wave front, from our measured stress histories, and offer a new way to determine the Hugoniot elastic limit of this material, as well as other brittle solids.

OS5-3-5 Micro-Crack Length Measurement Method in Ceramics by Using Grid Pattern Metal Film

In this study, the new and simple crack length measurement method by using grid pattern of Au film was suggested. Au film coated on the surface of a specimen by the ion sputtering method was cut like a comb by scanning laser beam condensed as a line, and the fine grid pattern film with the grid width, 10μm, and space width, 7μm, was made. Further, to confirm the validity of the method the crack growth test was carried out with four-point bending using soda-lime glass specimens. As a result, it was confirmed that the crack length measurement using the fine grid pattern film could express the relationship between the crack growth rate and stress intensity factor of the material in detail, and the possibility of the application to the other ceramic materials was also showed.

Effect of crosshead speed on the fracture toughness of soda-lime glass, Al2O3 and Si3N4 ceramics determined by the surface crack in flexure (SCF) method

The fracture toughness of soda-lime glass, Al2O3 and Si3N4 specimens was measured by the surface crack in flexure method. For the soda-lime glass specimens, the fracture toughness was calculated from the initial crack size and flexure strength, and the value increased with increasing crosshead speed. This trend seems to be related to the difficulty in determining the critical crack size at fracture, since slow crack growth occurs during bending test. For the Al2O3 specimens, a halo region (stable crack growth region) was formed around the initial precrack during bending test. The halo size increased and the resultant flexure strength decreased with decreasing in the crosshead speed. The halo region, however, could not be observed in the Si3N4 specimens. Despite of the difference in the appearance of halo region, the fracture toughness of the Al2O3 and Si3N4 specimens was constant irrespective of the crosshead speed when the values were calculated with the critical crack sizes at fracture (halo incorporated crack sizes). The constant fracture toughness with the crosshead speed could be explained by the relation between the changes of halo size (thus critical crack size at fracture) and resultant flexure strength.

Fatigue Strength as a Function of Preloading in Dynamic Fatigue Testing of Glass and Ceramics

The solution of fatigue strength as a function of preloading in dynamic fatigue (constant stress-rate) testing was obtained analytically and numerically. The effect of preloading on dynamic fatigue strength decreases with increasing fatigue parameter (n), and for n ≥ 20 the effect is negligible up to a preloading of 90 percent. The solution was verified by dynamic fatigue experiments conducted with soda-lime glass and alumina specimens in room-temperature distilled water. This result showed that one can apply a preloading corresponding up to 90 percent of fatigue strength for most glass and ceramic materials, resulting in a dramatic saving of testing time in dynamic fatigue testing. The key feature that makes this technique feasible is that most of the slow crack growth under dynamic fatigue loading occurs close to failure time where the dynamic fatigue strength is defined.

Effect of a proof test on the fatigue strength and lifetime of soda-lime glass

The effect of a proof test on the fatigue strength and lifetime of soda-lime glass specimens is studied. In practice, subcritical crack growth is difficult to avoid during the proof test so that the initial damage should be considered in the design life prediction process. Statistical treatment assumes that the fatigue lifetime depends on the Weibull modulus m, the material and environment dependent exponent n in the crack growth rate model and the eliminated ratio specimens in the proof test. The effect of the proof test becomes increasingly more important as this ratio is increased. For m/( n − 2) = 1, the statistical distribution of the fatigue strength is unchanged after the proof test. If m/( n − 2) becomes smaller than unity, the proof test raises the fatigue strength of the survived specimens, especially at higher survival probability, and reduces the scatter of the fatigue strength data. Hence, the reliability of the survival components is improved. The opposite occurs when m/( n − 2) becomes greater then unity.

Measurement of Indentation Residual Stresses in Materials Susceptible to Slow Crack Growth

Knowledge of the size and distribution of the indentation residual stress field is important when interpreting slow crack growth data for indented ceramic materials. A technique based on compressively loading indentation cracks has been used to measure the wedging residual stresses at radial indentation cracks. The method also gives information on the fatigue limit and can be applied on any ceramic material susceptible to slow crack growth. Soda–lime glass specimens were indented and the resulting residual stresses, wedging the radial cracks, were measured as a function of indentation load. Calculations of K0, the fatigue limit, were made for both virgin indentation cracks and cracks aged until saturation. The magnitude of closing stress needed to prevent slow crack growth was found to depend linearly on the indentation load. For example, for indentation loads of 20 and 60 N, the corresponding closing stresses were 14 and 26 MPa, respectively.

ＹＡＧレーザによるガラスの曲線割断

Cutting of brittle materials such as glass is usually made with a diamond scriber or a rotary roller chisel. It is said that the mechanical cutting of glass using the scriber or the chisel leads to lower cutting quality. A non-contacting cutting method using a CO2 laser is recently being studied enthusiastically. Precision breaking of glass and other brittle materials, however, has not been made.Curviform breaking of transparent glass plates by YAG laser was studied on the soda-lime glass specimens of which surface was painted marker ink (magic ink) for absorber of YAG laser beam. Influence of a laser tracing curvature on the deviation of broken line was examined. It was found from the experiments that smaller curvatures provide larger deviation of breaking location from the laser tracing locus, which reflects directly to lower quality breaking of glass.

Computer simulation of the quench-induced strength degradation in glass plates

A computer simulation of the strength degradation of quenched soda-lime glass specimens was performed. The evolution of quench-induced crack growth was studied with (1) no subcritical crack growth effect, and (2) subcritical crack growth included. The computer simulation quanlitatively indicates that the means retained strength exhibits a gradual decrease with increasing quench temperature difference. Subcritical crack growth enhances the thermal shock damage.

Contact thermal shock test of ceramics

A novel quantitative thermal shock test of ceramics is described. The technique employs contact between a metal cooling rod and hot disc-shaped specimen. In contrast with traditional techniques, the well-defined thermal boundary condition allows for accurate analyses of heat transfer, stress, and fracture. Uniform equi-biaxial tensile stresses are induced in the centre of the test specimen. Transient specimen temperature and acoustic emission are monitored continuously during the thermal stress cycle. The technique is demonstrated with soda-lime glass specimens. Experimental results are compared with theoretical predictions based on a finite element method thermal stress analysis combined with a statistical model of fracture. Material strength parameters are determined using concentric ring flexure tests. Good agreement is found between experimental results and theoretical predictions of failure probability as a function of time and initial specimen temperature.