Effect of thermal and mechanical aging on fracture toughness of Y-TZP core materials

Yıl 2014, Cilt: 31 Sayı: 1, 1 - 6, 25.02.2014

Merve Bankoğlu Güngör Handan Yılmaz Bilge Turhan Bal Seçil Karakoca Nemli Pırıl Türkan Sindel Cemal Aydın

https://doi.org/10.17214/aot.41767

Öz

OBJECTIVE: The purpose of this study was to evaluate the effect of thermal and mechanical aging on the fracture toughness of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) core materials.

MATERIALS AND METHOD: Disc-shaped specimens for each core material (diameter: 15 mm, thickness: 1.2 mm), Cercon Base and Lava Plus, were randomly divided into three groups (control, thermal aging and mechanical aging). No aging was applied to control specimens. Thermal aging group specimens were subjected to 10⁴ thermal cycles in water between 5-55 °C (dwell time of 30 s). Mechanical aging group specimens were subjected to a 200 N load for 10⁵ times, with a frequency of 2 Hz. The fracture toughness of the control, thermal and the mechanical aging groups were measured by using the indentation fracture technique. Ten indentations were performed for each material. After each indentation, microscopic readings were recorded and the fracture toughness was calculated according to an established formula. Results were statistically analyzed by using a two-way analysis of variance (ANOVA) test.

RESULTS: Indentation fracture toughness values of the control, the thermal and the mechanical aging groups of Cercon Base were 6.28, 6.39 and 6.02 MPa√m, respectively. There was no significant difference between the control group of Cercon Base and the aging groups (p>0.05). However, significant difference was found between the thermal and the mechanical aging groups of Cercon Base (p<0.05). Indentation fracture toughness values of the control, the thermal and the mechanical aging groups of Lava Plus were 4.79, 4.76 and 4.91 MPa√m, respectively. Again, there was no significant difference between the control the aging groups of Lava Plus (p>0.05).

CONCLUSION: Compared to control, thermal and mechanical aging had no significant effect on the fracture toughness of the different Y-TZP core materials.

Anahtar Kelimeler

Aging, Ceramics, Fatigue Fractures, Yttria Stabilized Tetragonal Zirconia, Zirconium Oxide

Isısal ve mekanik yaşlandırma işlemlerinin Y-TZP kor materyallerinin kırılma tokluğuna etkisi

Öz

AMAÇ: Bu çalışmanın amacı, ısısal ve mekanik yaşlandırma işlemlerinin, yttria-stabilize dörtgen zirkon (Y-TZP) kor materyallerinin kırılma tokluğu üzerindeki etkisinin araştırılmasıdır.

GEREÇ VE YÖNTEM: Her iki kor materyalinden disk şeklinde üretilen Cercon Base and Lava Plus örnekler (15 mm çap 1.2 mm kalınlık) rastgele olarak 3 gruba (kontrol, ısısal yaşlandırma ve mekanik yaşlandırma) ayrıldı. Kontrol gruplarına herhangi bir işlem yapılmadı. Isısal yaşlandırma işlemi 5-55 °C sıcaklıklarda su içeren banyolarda, her birinde 30 sn kalacak şekilde 10⁴ kez uygulandı. Mekanik yaşlandırma işlemi ise, 200 N yük ile, 2 Hz frekansta 10⁵ kez uygulandı. Kırılma tokluğu deneyi indentasyon kırılma metodu kullanılarak gerçekleştirildi. Her grup için on ölçüm yapıldı. Her bir indentasyon sonrası mikroskopik okuma kaydedildi ve kırılma tokluğu değeri önceden belirlenmiş bir formüle göre hesaplandı. İstatistiksel analiz iki yönlü varyans analizi (ANOVA) ile yapıldı.

BULGULAR: Cercon Base grubu örneklerin kırılma tokluğu değerleri, kontrol, ısısal ve mekanik yaşlandırma grubu için sırasıyla 6.28, 6.39 ve 6.02 MPa√m olarak belirlendi. Cercon Base grubu örneklerinde, kontrol grubu ve yaşlandırma grupları arasında istatistiksel olarak anlamlı bir fark bulunmadı (p>0.05). Fakat, Cercon Base grubunda, ısısal ve mekanik yaşlandırma grupları arasında istatistiksel olarak anlamlı fark bulundu (p<0.05). Lava Plus grubu örneklerinin kırılma tokluğu değerleri, kontrol, ısısal ve mekanik yaşlandırma grubu için sırasıyla 4.79, 4.76 ve 4.91 MPa√m olarak belirlendi. Lava Plus grubu örneklerinde, kontrol grubu ve yaşlandırma grupları arasında istatistiksel olarak anlamlı bir fark bulunmadı (p>0.05).

SONUÇ: Yaşlandırma işlemlerinin, kontrole kıyasla, Y-TZP kor materyallerine ait kırılma tokluğu değerlerini belirgin olarak etkilemediği tespit edildi.

Anahtar Kelimeler

Seramikler, Yaşlanma, Yorulma Kırıkları, Yttria Stabilize Dörtgen Zirkon, Zirkonyum Oksit

Kaynakça

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