Comparative Evaluation of effect of resin protective coatings on the surface hardness and shear punch strength of different GlCs - An InVitro Study

G-Coat Plus is a nano-filled, self-adhesive light cured protective coating that strengthens, protects and enhances glass ionomer restorations. The effect of G- Coat plus on different GICs have not been studied comprehensively. Hence the study was conducted to compare the effect of resin coating on surface hardness and Shear punch strength of newer modified GIC.Materials and methods: 120 samples of three GICs i.e. Fuji IX Extra, Fuji IX Fast, Fuji II LC were prepared using specialized metal moulds. Specimens of Fuji II LC were light cured for 20 seconds. Coated and uncoated samples were tested for surface hardness and 30 samples were tested for shear punch strength. P < 0.05 was considered as significant. Results: Shear Punch Strength after G-Coat plus coating was significantly higher for Fuji IX Extra followed by Fuji II LC. Surface Hardness after G- Coat plus coating was significantly higher for Fuji IX Extra followed by Fuji IX Fast and Fuji II LC.Conclusion: Surface coating by a resin agent significantly increases the surface hardness and shear strength of the GIC. Considering the above stated findings, they can be incorporated into daily clinical practice to enhance the strength and longevity of GIC.

Assessing Microstructure-Local Mechanical Properties in Friction Stir Welded 6082-T6 Aluminum Alloy

The severe deformation and temperature paths in the stir zone, also called weld nugget, of friction stir welded joints result, at very local levels, in significant microstructural variations, such as major differences in grain size or precipitation. One of the most common features of friction stir welds is the presence of successive material layers, known as onion rings; however, little data is available on the mechanical properties of the different regions of the weld nugget, and particularly within the onion ring bands. Such information becomes very important for the integrity of large size friction stir welded structures. In the present study, a comprehensive characterization of onion rings produced during friction stir welding of a 6082-aluminum alloy was carried out. Advanced techniques such as in-situ SEM nanoindentation, EBSD, and high-resolution EDS were used to validate and compare the characteristics of the different bands in the onion rings. The analyses consisted of quantifying variations in grain size, precipitate composition and distribution, crystallographic orientations, and mechanical properties in each band. Furthermore, the tensile strengths of different regions of the weld nugget were evaluated using shear punch testing and correlated with those for the onion ring region in order to determine the impact of the presence of onion rings on weld nugget mechanical properties. The main difference between the alternate bands in the onion ring was found to be due to the difference in their grain size, misorientation, and precipitate content. It was also observed that the bands originate from the base metal and stir zone successively due to the nature of the stirring process, which pulls BM into SZ. Comparison of the shear punch testing results in different regions of the nugget revealed that, in spite of having local differences in the hardness of alternate bands in the onion ring, the presence of onion rings has no significant impact on the deterioration of the mechanical properties of the weld nugget.

Evaluating the Mechanical Behavior of ARB Processed Aluminum Composites Using Shear Punch Testing

Multi-layered metal composites have received considerable attention due to their improved mechanical and physical properties. In this study, Al6061/Al2024 composite was processed by accumulative roll bonding (ARB) as a severe plastic deformation technique. Mechanical properties of processed material were evaluated using the uniaxial tensile test and shear punch test method (SPT). The correlation between the results of the tension experiments and shear strengths was calculated. Experimental results demonstrated that the shear strength enhanced with increased number of ARB passes. However, the elongation under shear manifested a reduction when the number of ARB passes increased. Inspection of the results of tensile tests and SPT revealed that they follow a similar trend for both strength and ductility. Therefore, it can be asserted that the shear punch test represents a useful and complementary tool in the mechanical analysis of the ARB sample.