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STATEMENT OF PROBLEM. Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic material has been reported to possess remarkably high flexural strength; however, after sintering zirconium dioxide (ZrO2) frameworks and fixed partial dentures, some may not fit properly when trying them on their master cast. PURPOSE. The objective of this study was to investigate joining fully sintered YTZ-P by various methods including adhesive cements or fusion with intervening materials. MATERIALS AND METHODS. 216 specimens were used in this study; bars were fabricated from Vita In-Ceram YZ blocks and three bars were joined using dental cements; RelyX Unicem 2 Clicker and Multilink Automix, or fusing them with VM9, Infusion Glass, Boron Oxide, Aluminum Oxide, LUDOX, Colloidal Zirconia and Mullite Zirconia. The load to failure in Newtons was determined using a 3-point bending test. RESULTS. Sandblasted bars for RelyX (64.38N, RelyX-A-Sb) and Multilink (48.58N, M-Sb) wasn’t significantly higher compared to as-sintered groups (45.87N, RelyX-A) and (34.69N, M-A). Coating the bars with Monobond-Plus had a significantly higher load to failure 123.22N, RelyX-A-MP and 136.06N, M-MP compared to as-sintered and sandblasted groups. VM9 at an end firing temperature (EFT) of 1200 °C was significantly higher (228.97N, V-5) compared to lower fusing temperatures. Glass at an end firing temperature of 1200 °C was significantly higher (460.32N, G-6) compared to lower fusing temperatures. Frit at an end firing temperature of 1200 °C was significantly higher (214.52N, F-6) compared to lower fusing temperatures. Optical microscopy showed that Glass group G-6 (1200°C, EFT) had a thickness range from .09 to 0.03 mm while for Glass-A (1050°C, EFT) it was 0.5 mm. CONCLUSIONS. Within the limitations of this study, we concluded that sandblasted bars didn’t significantly increase the means load to failure values compared to as-sintered groups. Coating the bars with Monobond-Plus had a significantly higher load to failure compared to as-sintered and sandblasted groups. VM9, Glass and Frit at an end firing temperature of 1200 °C showed significantly higher means load to failure compared to lower fusing temperature groups. / 2018-09-28T00:00:00Z

This comprehensive study is the first to quantify the fatigue performance, failure loads, and microstructure of resistance spot welding (RSW) in 6061-T6 aluminum (Al) alloy according to welding parameters and process sensitivity. The extensive experimental, theoretical and simulated analyses will provide a framework to optimize the welding of lightweight structures for more fuel-efficient automotive and military applications. The research was executed in four primary components. The first section involved using electron back scatter diffraction (EBSD) scanning, tensile testing, laser beam profilometry (LBP) measurements, and optical microscopy(OM) images to experimentally investigate failure loads and deformation of the Al-alloy resistance spot welded joints. Three welding conditions, as well as nugget and microstructure characteristics, were quantified according to predefined process parameters. Quasi-static tensile tests were used to characterize the failure loads in specimens based upon these same process parameters. Profilometer results showed that increasing the applied welding current deepened the weld imprints. The EBSD scans revealed the strong dependency between the grain sizes and orientation function on the process parameters. For the second section, the fatigue behavior of the RSW’ed joints was experimentally investigated. The process optimization included consideration of the forces, currents, and times for both the main weld and post-heating. Load control cyclic tests were conducted on single weld lap-shear joint coupons to characterize the fatigue behavior in spot welded specimens. Results demonstrate that welding parameters do indeed significantly affect the microstructure and fatigue performance for these welds. The third section comprised residual strains of resistance spot welded joints measured in three different directions, denoted as in-plane longitudinal, in-plane transversal, and normal, and captured on the fusion zone, heat affected zone and base metal of the joints. Neutron diffraction results showed residual stresses in the weld are approximately 40% lower than the yield strength of the parent material, with maximum variation occurring in the vertical position of the specimen because of the orientation of electrode clamping forces that produce a non-uniform solidification pattern. In the final section a theoretical continuum modeling framework for 6061-T6 aluminum resistance spot welded joints is presented.

This paper summarises the data from 1819 tests on concrete-filled steel tube columns and compares their failure load with the prediction of Eurocode 4. The full data is given on the website http://web.ukonline.co.uk/asccs2 . The comparison with Eurocode 4 is discussed and shows that Eurocode 4 can be used with confidence and generally gives good agreement with test results, the average Test/EC4 ratio for all tests being 1.11. The Eurocode 4 limitations on concrete strength could be safely extended to concrete with a cylinder strength of 75 N/mm2 for circular sections and 60 N/mm2 for rectangular sections.

yes / The results of testing two simply and three continuously supported concrete beams reinforced with glass fiber-reinforced polymer (GFRP) bars are presented. The amount of GFRP reinforcement was the main parameter investigated. Over and under GFRP reinforcements were applied for the simply supported concrete beams. Three different GFRP reinforcement combinations of over and under reinforcement ratios were used for the top and bottom layers of the continuous concrete beams tested. A concrete continuous beam reinforced with steel bars was also tested for comparison purposes. The experimental results revealed that over-reinforcing the bottom layer of either the simply or continuously supported GFRP beams is a key factor in controlling the width and propagation of cracks, enhancing the load capacity, and reducing the deflection of such beams. Comparisons between experimental results and those obtained from simplified methods proposed by the ACI 440 Committee show that ACI 440.1R-06 equations can reasonably predict the load capacity and deflection of the simply and continuously supported GFRP reinforced concrete beams tested.