CRACK DETECTION in ZrO2 CERAMICS
Multi-Angle Vibrations (MAV) Technology
- High accuracy: up to 99%
- High throughput: <5seconds/cycle
- Non destructive
- In-line & Off-line configuration
The Multi-Angle Vibrations (MAV) technique was developed for off-line and in-line non-destructive crack and stress detection in ceramic materials such as pre-sintered dental ZrO2. The RUV method relies on a deviation of the resonance frequency response curve measured on a sample with millimeter length crack compared to identical non-cracked samples.
The MAV technology allows to (1) reject mechanically unstable ceramic objects before they are introduced into further processing, (2) identify objects with cracks and high stress in real-time to avoid parts breakage during milling or final sintering, and (3) to save production expenses by eliminating labor cost on cracked ceramic discs. MAV system also serves as a process control tool to increase yield by eliminating production flaws caused by mechanical defects.
Zirconia ceramics is a primary material for the state-of-the-art dental industry. Its primary benefits are superior strength (x5 better than porcelain), durability, biocompatibility, natural color, and translucency to match natural teeth. However, with any other ceramics, ZrO2 discs are prone to invisible cracking which lead to dentures breakage during milling or initial wear. MAV technology is adapted to 100% cracks inspection of ZrO2 dental discs before processing in a dental lab.
Through a resonance frequency curve selected from a broad range (20 - 250 kHz), the MAV method enables screen out materials with hidden invisible cracks. A crack introduced into ceramics alters the MAV peak parameters: amplitude, bandwidth and peak position. The inspection approach is illustrated in Figure 2. Specifically, the crack in the disc measured at different angles in the rotation mode shows the following feature: large individual peak variation between three scans compared to high coincidence for a good sample. Therefore, the MAV approach is based on a fast measurement and analyses (below 5 seconds per scan) of a specific resonance peak and automatic part rejection if peak characteristics deviate from the normal non-cracked samples. An additional MAV feature is stress inspection caused by voids and components delamination.
The sensitivity of the system, which refers to the length of the cracks, is adjustable to the needs of the user. The rejecting method is based on a statistical approach. In production the accuracy of this method to find cracked material approaches 99%. MAV system can be used in the production of ZrO2 dental discs, Zr-based solid oxide fuel cells, and metallized ceramic rings.
IN LINE & OFFLINE CONFIGURATIONS
Fully automatic In-line, Off-line and Quality Control MAV tools are available for ceramic products. For technical information and MAV system availability, please contact Ultrasonic Technologies at support page.