Simulation of brittle damage for fracture process of endodontically treated tooth

The mechanics of brittle damage in porcelain of an endodontically treated maxilla incisor tooth was simulated using finite element method (FEM). For this purpose a very complex composite structure of endodontically treated tooth is simulated under transverse loading. Three dimensional (3D) model of human maxilla incisor tooth root was developed based on Computed Tomography (CT) scan images. Crown, core cement, resin core, dental post, post cement and dentin were created using SolidWorks software, and then the model was imported into ABAQUS-6.9EF software for nonlinear behavior analysis. This study utilizes finite element method to simulate onset and propagation of crack in ceramic layer (porcelain) by the cause of both tension and compression loading related to complexity of the geometry of tooth implant. The simulation has been done using brittle damaged model available in ABAQUS/Explicit in quasi-static load condition. The load-displacement response of whole structure is measured from the top of porcelain by controlling displacement on a rigid rod. Crack initiated at the top of porcelain bellow the location of the rod caused by tension damage at equivalent load of 590 N. Damage in porcelain accounts for up to 63% reduction of whole structure stiffness from the undamaged state. The failure process in porcelain layer can be described by an exponential rate of fracture energy dissipation. This study demonstrated that the proposed finite element model and analysis procedure can be use to predict the nonlinear behavior of tooth implant

Effects of Probiotic on Turkeys and Laying Hens

Previous studies (A.S. Series 78-7, 77-20 and 76-10) have shown probiotics to have beneficial effects upon growing turkeys under some conditions of stress. There was no response with laying hens in a study reported on last year (A.S. Series 78-7)

The Behavior of Rectangular and Circular Reinforced Concrete Columns under Biaxial Multiple Excitation

The aim of this study is to investigate the dynamic performance of rectangular and circular reinforced concrete (RC) columns considering biaxial multiple excitations. For this purpose, an advanced nonlinear finite element model which can simulate various features of cyclic degradation in material and structural components is used. The implemented nonlinear fiber beam-column model accounts for inelastic buckling and low-cycle fatigue degradation of longitudinal reinforcement and can simulate multiple failure modes of RC columns under dynamic loading. Hypothetical rectangular and circular columns are used to investigate the failure modes of RC columns. A detailed ground motion selection is implemented to generate real mainshock and aftershocks. It was found that multiple excitations due to aftershock has the potential of increasing the damage of the RC columns and longitudinal reinforcements are significantly affected low-cycle fatigue. Also, it was found that rectangular column is more sensitive to accumulative damage due to cyclic fatigue. This study increases the accuracy of structural analysis of RC columns and consequently improves understanding the failure modes of RC columns with different cross-sectional shapes

Grower Diets for Layer Pullets Using Corn or Oats

In previous studies with low-protein (12%) diets for growing pullets, the diets that have supported the best subsequent production and with the least mortality and layer feed have contained some oats. Last year\u27s results showed a 30% oats diet to be just as good in that regard as one containing 80% oats. A 12% protein diet with only corn as the grain component caused the hens to produce at a 2.7% lower rate of production (440 hens per treatment, significant at 0.05)

Effect of Pelleting and Bacitracin Form on Egg Production

Bacitracin-MD and zinc bacitracin at 0, 10, 20 and 40 g per ton levels were individually added to a 13.2% protein low density mash diet (Table 1). In addition, the control and diets containing 40 g of antibiotics per ton were pelleted to investigate the effects of antibiotics and/or pelleting on egg production parameters and feed consumption. Twelve 24-week old pullets were initially used for each treatment replicated eight times using randomized complete block designs. Feed and water were provided ad libitum

Performance Of Layers As Affected By Grower Diets And Pelleting 12 And 16% Protein Diets

Previous studies at this station have shown significant advantages for using grower diets relatively higher in fiber content. This study was conducted in part to evaluate the use of oat hulls for which frequently there is no demand for this purpose. During the layer phase, the effects of pelleting were examined

A Patient-Centered Methodology That Improves the Accuracy of Prognostic Predictions in Cancer

Peer reviewe