The aim of this study was to evaluate the combined effect of MTAD and photon‐induced photoacoustic streaming (PIPS) technique on the smear layer removal and the bond strength of glass fiber post. Fifty‐five human mandibular premolars were chosen. After root canal therapy and post space preparation, the teeth were equally divided to five groups according to the methods of root‐dentin pretreatment: G1: distilled water (control); G2: 2.5% NaOCl+17% EDTA; G3: MTAD; G4: PIPS; G5: MTAD+PIPS. One sample was randomly selected from each group, and scanning electron microscope (SEM) was used to observe the microscopic morphology of the coronal, middle and apical level of the root‐dentin. The remaining ten samples from each group were glued to glass fiber posts, and the bond strength was assessed by push‐out test. SEM evaluation showed that the most complete smear layer removal was found in MTAD + PIPS group, especially in coronal third. Push‐out test results exhibited that there was a statistically significant interaction between the experimental groups and root canal third (p < .0005). Significant differences could be found among five groups (p < .05): G5 > G4 > G3 > G2 > G1. G5 had the highest bond strength. In conclusion, post space pretreatments with MTAD or PIPS technique can significantly remove smear layer and improve the bond strength of glass fiber post, and combination of them works best.

In this paper, the technology of self-piercing riveting (SPR) with half-hollow rivets was investigated using experiments and numerical simulations with 6063 aluminum alloy sheet. The failure mechanism of SPR aluminum alloy sheet was indicated with the shear model and tear model, which could accurately simulate the sheet structure. Based on the simulation results with finite element method (FEA), the effect of die geometry on static mechanical characteristics, including punch load, failure load and failure displacement, was analyzed. It was discovered that the die pip height and sheet thickness should be designed synthetically for optimal tensile behavior.

No abstract

An acquisition of ferrite surface images has been taken with a LY-WN-YH Hyper-depth measurement system, from which the crack condition was analyzed with MATLAB. Based on the contradistinction between experimental data from ferrite work pieces of different quality, a preliminary conclusion has been drawn that the surface quality of ferrite materials has a direct link to the quantity and length of the crack on them. By measuring the quantity and length of the crack, an initial criterion was obtained for judging the surface quality of ferrite.