Fracture Resistance of Primary Zirconia Crowns: An In Vitro Study

In this study, we evaluated the fracture resistance of three commercially available prefabricated primary zirconia crowns and their correlation with dimensional variance. Methods: a total of 42 zirconia crowns were selected from three companies, (1) NuSmile primary zirconia crowns, (2) Cheng Crowns zirconia, and (3) Sprig EZ crowns. The crowns were divided into two groups based on their location in the oral cavity and further divided into subgroups based on the brand. All of the samples were subjected to fracture tests using a universal testing machine. Results: the mean load observed was highest with Cheng Crowns zirconia anterior crowns (1355 ± 484) and the least load was seen with Sprig EZ anterior crowns with a mean load of 339 ± 94. The mean load observed was highest with Cheng Crowns zirconia posterior crowns (1990 ± 485) followed by NuSmile posterior crowns and the least load was seen with Sprig EZ posterior crowns with a mean load of 661 ± 184. Conclusion: the Cheng crowns showed the highest fracture resistance amongst all three groups. Overall, the zirconia crowns (anterior and posterior) tested showed optimum mechanical properties to withstand the masticatory forces.

Effects of Size, Section Pattern, and Material on the Tensile Performance of Filled Thin-Walled Tubes

The tensile performance of ductile tubes can be enhanced by the application of fillers. Research studies on the mechanical performance of filled tensile tubes have mainly focused on experiments and numerical simulations on concrete-filled steel tube (CFST) components, while the effects of factors such as size, section pattern, and material of filled tensile tubes on their performance have rarely been studied. In this research, the effects of size, section pattern, and material on the tensile performance of filled tubes have been evaluated through theoretical studies, simulations, and experiments. The tensile strength reinforcement and deformation weakening coefficients of filled circular thin-walled tubes corresponding to hollow tubes were theoretically deduced, and the influencing factors of the two were parametrically evaluated. Tensile performances of filled tubes with circular and square sections were compared with each other through numerical methods. In the current research, the circular section was optimized and prestressed circular hollow support section was proposed. Tensile fracture tests were performed on circular thin-walled tubes made of six different materials to determine material effects on the tensile performance of these structures. It was also found that metallic materials with good ductility significantly enhanced the tensile performance, fracture toughness, and energy consumption of test components containing prestressed filler.

Acoustic emission as a valuable technique used for monitoring polymer failures

In the paper, acoustic emission (AE) system was presented as a method that can be used to monitor polymer material failures. Samples fabricated of two aluminum profiles bonded together with a thick layer of cured epoxy resin were subjected to fracture tests. Epidian 53 epoxy resin cured with Z1 curing agent as well as Epidian 5 epoxy resin cured with PAC curing agent were selected as adhesives. Acoustic emission parameters were acquired during Double Cantilever Beam (DCB) tests. The frequencies of elastic waves released during failure were then analyzed using both Fast Fourier Transformation (FFT) and Wavelet Transformation (WT) for the two materials.

Advanced Evaluation of the Freeze–Thaw Damage of Concrete Based on the Fracture Tests

This paper presents the results of an experimental program aimed at the assessment of the freeze–thaw (F–T) resistance of concrete based on the evaluation of fracture tests accompanied by acoustic emission measurements. Two concretes of similar mechanical characteristics were manufactured for the experiment. The main difference between the C1 and C2 concrete was in the total number of air voids and in the A300 parameter, where both parameters were higher for C1 by about 35% and 52%, respectively. The evaluation of the fracture characteristics was performed on the basis of experimentally recorded load–deflection and load–crack mouth opening displacement diagrams using two different approaches: linear fracture mechanics completed with the effective crack model and the double-K model. The results show that both approaches gave similar results, especially if the nonlinear behavior before the peak load was considered. According to the results, it can be stated that continuous AE measurement is beneficial for the assessment of the extent of concrete deterioration, and it suitably supplements the fracture test evaluation. A comparison of the results of fracture tests with the resonance method and splitting tensile strength test shows that all testing methods led to the same conclusion, i.e., the C1 concrete was more F–T-resistant than C2. However, the fracture test evaluation provided more detailed information about the internal structure deterioration due to the F–T exposure.

Effect of Loading Angles and Implant Lengths on the Static and Fatigue Fractures of Dental Implants

Mechanical properties play a key role in the failure of dental implants. Dental implants require fatigue life testing before clinical application, but this process takes a lot of time. This study investigated the effect of various loading angles and implant lengths on the static fracture and fatigue life of dental implants. Implants with lengths of 9 mm and 11 mm were prepared. Static fracture tests and dynamic fatigue life tests were performed under three loading angles (30°, 40°, and 50°), and the level arm and bending moment were measured. After that, the fracture morphology and fracture mode of the implant were observed. The results showed that 9 mm length implants have a higher static failure load and can withstand greater bending moments, while 11 mm length implants have a longer fatigue life. In addition, as the loading angle increases, the static strength and bending moment decrease linearly, and the fatigue life shows an exponential decrease at a rate of three times. Increasing the loading angle reduces the time of the implant fatigue test, which may be an effective method to improve the efficiency of the experiment.

Effects of hybridization and ply thickness on the strength and toughness of composite laminates

This work presents the results of an experimental study performed in carbon/epoxy composite materials manufactured using a ply-level hybridization technique. The aim of the study is to investigate the potential of such hybridization technique to promote pseudo-ductile failure, and to enhance fracture toughness. Two thin-ply carbon-epoxy systems and three different carbon-carbon hybrid lay-ups are considered. Both strength and fracture tests are performed on the manufactured laminates and the properties of the hybrid materials are compared to those of the baseline non-hybrid composites. Digital Image Correlation and post-mortem X-ray imaging are used to analyze the fracture process of the different materials. The comparison of the mechanical response of the different materials demonstrates that, by means of thin ply hybridization, a pseudo-ductile failure in tension can be obtained, associated with fibre fragmentation. However, the hybridization seems not to be responsible for the increased fracture toughness that is ascribable to the ply-thickness effect.

Numerical Analysis of Edge Cracking in High-Silicon Steel during Cold Rolling with 3D Fracture Locus

In this study, a 3D fracture locus of high-silicon steel strip was constructed through a series of fracture tests with specimens of various shapes and corresponding finite element (FE) simulations of the fracture tests. A series of FE analyses coupled with the developed fracture locus was conducted, and the effect of the secondary roll-bending ratio (defined as L2/R2, where L2 and R2, respectively, denote the secondary work roll barrel length and the radius of the convex curvature of the work roll surface profile emulating positive roll bending) and the initial notch length on edge cracking in the strip during cold rolling was investigated. The results reveal that the 2D fracture locus that does not include the Lode angle parameter (varying between −0.81 and 0.72 during cold rolling) overestimates the edge cracking in the range of 13.1–22.2%. The effect of the initial notch length on the length of crack grown in the transverse direction of the strip during cold rolling is greatest when the ratio L2/R2 is 0.12.