Finite element comparison of single, bi-layered and three-layered tube hydroforming processes
In this paper, single, bi-layered and three-layered tube hydroforming processes were numerically simulated using the finite element method. It was found that the final bulges heights resulted from the models were in good agreement with the experimental results. Three types of modeling were kept with the same geometry, tube material and process parameters to be compared between the obtained hydroformed products (branch height, thickness reduction and wrinkling) using different loading path types. The results were also discussed.
Experimental Investigation and Optimization of Bi-Layered Tube Hydroforming Process Parameters with Particle Swarm Optimization Algorithm
Determining of exact loading paths for bi-layered hydroforming are very neseccery to produce good products that confirmed design specifications. Unfortunately, theoretical formulas don’t exist to determine the process parameters. The process parameters were determined by trial-and-error and experiences of process planner. Therefore, a hybrid method of finite element and particle swarm optimization (PSO) was proposed for determining of the bi-layered hydroforming parameters. First, this process was simulated and verified by experimental data. Then, finite element and optimization algorithm were linked and used to determine of exact process parameters. Two constrains, thickness variations and maximum stress, were considered in the optimization process. Also, conformation of the geometrical dimension of the product with the design dimension was considered as a goal function. Pressure and feed loading paths were optimized in this research and both loading paths were assumed to be linear. Also, external and internal tubes materials are aluminium and copper, respectively.
Effect of Calcium Glycerophosphate on Demineralization in an in vitro Biofilm Model
The aim was to investigate the anti-caries properties of calcium glycerophosphate (CaGP) using an in vitro bacterial flow cell model. Four flow cells, inoculated from a chemostat containing a seven-organism bacterial consortium, were pulsed with sucrose twice daily, to provide an acidic challenge and pH-cycling conditions. Blocks of enamel and dentine were mounted in each flow cell. In a study on the effect of CaGP concentration, CaGP was pulsed into three of the flow cells, at the same time as the sucrose, to give concentrations of 0.10, 0.25 and 0.50%. Water was pulsed into the fourth flow cell with the sucrose. Microradiography revealed a significant dose response of decreasing demineralization as CaGP concentration increased. Reductions at 0.25 and 0.5% were significant when compared to the control. A second study investigated the effect of timing of CaGP pulsing, relative to sucrose, on enamel and dentine demineralization. CaGP (flow cell concentration 0.2%), was pulsed 1 h before, during or 1 h after the sucrose pulse; a water control was employed. In enamel, pulsing CaGP before the sucrose reduced demineralization significantly compared to concurrent pulsing, which in turn gave a significant reduction compared to pulsing after sucrose, which did not reduce demineralization significantly compared to the water control. In dentine, CaGP reduced demineralization significantly only when pulsed before the sucrose. The findings suggest that in vivo, the anti-caries potential of CaGP may be greater if it is applied before a cariogenic challenge.