IADR Abstract Archives
Two Fracture Toughness Methods of a Gradiated Zirconia
Objectives: To examine a gradiated multilayered-multitranslucent zirconia using SEVN and SEPD fracture toughness methods
Methods: Two testing methods were used to examine fracture toughness: Single Edge Precrack Beam(SEPB), and Single Edge V-Notch(SEVN). Three regions of e.max ZirCAD Prime were tested with each method: Groups 1 and 2: Top (5Y), Groups 3 and 4 gradient zone (5Y to 3Y gradient), and Groups 5 and 6 Core (3Y). Eight flexure bars (36mm x 4mm x 3mm after sintering) per zirconia material were milled in each region using a Wieland Zenotex Select. Milled bars were sintered according to the manufacturer's instructions.
For the SEPB tested method, the fully sintered bars were indeted with 3 indents across the bar. The bars were loaded in a precracking fixture (ASTM Standard C1421) using an Instron Universal testing machine (33R4204) (0.25mm/min crosshead speed). The specimen was then backlit to examine for a crack. The precracked specimens were loaded in a 30mm 3-point flexure loading fixture (0.5mm/min crosshead speed).
For the SEVN method, 1mm V-notch was placed using a Diamet diamond saw. The specimens were loaded to failure in a 30mm 3-point testing fixture (0.5mm/min crosshead speed).
Three equa-spaced measurements were taken at 80x using an Olympus SZX12 microscope for both techniques.
The SEPB fracture toughness was calculated using:
KIC=(PfS/bW3/2)f(a/W)
where
f(a/W)=(3/2)(a/W)1/2(1.964-2.837a/W+13.711a2/W2-23.250a3/W3+24.129a4/W4)
The SEVN fracture toughness was calculated using:
KIC = g*[(Pf*Sx10-6)/(b*w3/2)]*[(3(a/w)1/2)/(2(1-a/w)3/2)]
g is {1.99-[(a/w)(1-a/w)]*[2.15-3.93(a/w)+2.7*(a/w)2]}/[1+2(a/w)]
Pf is failure load; s is span; b is thickness; w is width; and a is precrack length/average V-notch depth.
Results: The fracture toughness, KIC(MPa●m0.5), for each group is: Group1: 2.63±0.38; Group2: 3.75±0.68; Group3: 4.35±0.36; Group4: 8.77±0.55; Group5: 5.07±0.17 and Group6: 13.88±1.04. Using ANOVA (p≤0.05), a statistical difference was found for all the zones between the SEPB and SEVN methods.
Conclusions: Within the bounds of this study, SEVN produced higher KIC values which increased with tetragonal phase.
Methods: Two testing methods were used to examine fracture toughness: Single Edge Precrack Beam(SEPB), and Single Edge V-Notch(SEVN). Three regions of e.max ZirCAD Prime were tested with each method: Groups 1 and 2: Top (5Y), Groups 3 and 4 gradient zone (5Y to 3Y gradient), and Groups 5 and 6 Core (3Y). Eight flexure bars (36mm x 4mm x 3mm after sintering) per zirconia material were milled in each region using a Wieland Zenotex Select. Milled bars were sintered according to the manufacturer's instructions.
For the SEPB tested method, the fully sintered bars were indeted with 3 indents across the bar. The bars were loaded in a precracking fixture (ASTM Standard C1421) using an Instron Universal testing machine (33R4204) (0.25mm/min crosshead speed). The specimen was then backlit to examine for a crack. The precracked specimens were loaded in a 30mm 3-point flexure loading fixture (0.5mm/min crosshead speed).
For the SEVN method, 1mm V-notch was placed using a Diamet diamond saw. The specimens were loaded to failure in a 30mm 3-point testing fixture (0.5mm/min crosshead speed).
Three equa-spaced measurements were taken at 80x using an Olympus SZX12 microscope for both techniques.
The SEPB fracture toughness was calculated using:
KIC=(PfS/bW3/2)f(a/W)
where
f(a/W)=(3/2)(a/W)1/2(1.964-2.837a/W+13.711a2/W2-23.250a3/W3+24.129a4/W4)
The SEVN fracture toughness was calculated using:
KIC = g*[(Pf*Sx10-6)/(b*w3/2)]*[(3(a/w)1/2)/(2(1-a/w)3/2)]
g is {1.99-[(a/w)(1-a/w)]*[2.15-3.93(a/w)+2.7*(a/w)2]}/[1+2(a/w)]
Pf is failure load; s is span; b is thickness; w is width; and a is precrack length/average V-notch depth.
Results: The fracture toughness, KIC(MPa●m0.5), for each group is: Group1: 2.63±0.38; Group2: 3.75±0.68; Group3: 4.35±0.36; Group4: 8.77±0.55; Group5: 5.07±0.17 and Group6: 13.88±1.04. Using ANOVA (p≤0.05), a statistical difference was found for all the zones between the SEPB and SEVN methods.
Conclusions: Within the bounds of this study, SEVN produced higher KIC values which increased with tetragonal phase.