Laser notching ceramics for reliable fracture toughness testing

Abstract

A new method for notching ceramics was developed using a picosecond laser for fracture toughness testing of alumina samples. The test geometry incorporated a singleedge-V-notch that was notched using picosecond laser micromachining. This method has been used in the past for cutting ceramics, and is known to remove material with little to no thermal effect on the surrounding material matrix. This study showed that laser-assisted-machining for fracture toughness testing of ceramics was reliable, quick, and cost effective. In order to assess the laser notched single-edge-V-notch beam method, fracture toughness results were compared to results from other more traditional methods, specifically surface-crack in flexure and the chevron notch bend tests. The results showed that picosecond laser notching produced precise notches in post-failure measurements, and that the measured fracture toughness results showed improved consistency compared to traditional fracture toughness notching methods.

Determination of fracture toughness of zirconia ceramics with different yttria concentrations by SEVNB method

“…Because when the notch root radius is larger than the major microstructural feature size (1.5-to 3-fold values of the average grain size) the fracture toughness results will be adversely affected by the size effect [9,13,19]. One possible method to introduce a submicron sharp V-notch in zirconia is by ultra-short pulsed laser ablation, which has been successfully applied in the cutting process of Al 2 O 3 , Si 3 N 4 and 3Y-TZP ceramics [20][21][22]. This micromachining technique has shown that there was a little or no thermal effect on the surrounding material [22,23].…”

“…One possible method to introduce a submicron sharp V-notch in zirconia is by ultra-short pulsed laser ablation, which has been successfully applied in the cutting process of Al 2 O 3 , Si 3 N 4 and 3Y-TZP ceramics [20][21][22]. This micromachining technique has shown that there was a little or no thermal effect on the surrounding material [22,23]. However, most of the studies in which laser ablation was used in zirconia were concentrated on the surface micro-structuring for dental use [24][25][26][27].…”

Evaluation of damage in front of starting notches induced by ultra-short pulsed laser ablation for the determination of fracture toughness in zirconia

“…One way of machining a very sharp notch on the surface of ceramics is ultrashort pulsed laser ablation (UPLA), which, in principle, is a technique capable of inducing very sharp features with negligible damage [6]- [8]. It is then an appealing technique for inducing a very sharp starting notch for measuring fracture toughness [9]- [12].…”

Relationship between residual stresses and mechanical behavior in ceramic composites

“…The introduction of very sharp notches on specimens is essential for accurate testing. Previous studies [134] confirmed the advantages that laser notching can be more economical than conventional mechanical methods and can also produce notches with minimal unwanted damage to the surrounding material for fracture toughness testing of ceramics. Due to this reliability in the notch size, this method is recommended for notching ceramics or other brittle materials.…”

“…In this work, fracture toughness ( ) of A/Y-TZP materials was evaluated by two different methods: (i) the Single Edge Laser-Notch Beam (SELNB) method [134][135][136] and (ii) the indentation fracture (IF) method [137,138].…”