Papers by Keyword: Crown

Abstract: Objective: To study the fracture resistance and failure modes of different type of ceramic crowns. Methods: Four groups of crown including zirconia-veneering porcelain crown (Group 1), whole zirconia crown (CAD/CAM, Group 2), cast ceramic crown (Group 3) and glass ceramic crown (CAD/CAM, chairside, Group 4) with the same thickness were manufactured, each group own 12 crowns. The fracture resistance test and failure modes analysis of the specimens were conducted, SPSS22.0 was used to analyze the difference among the groups. Results: The fracture strength of Group 2 is significantly higher than other three group (P<0.05), Statistical significance was found between group 3 and group 1, group 4. No Statistical significance was found between group 1 and group 4. The failure modes of the whole zirconia crown, the cast ceramic crown and the glass ceramic crown are complete crown fracture; 33% of the zirconia-veneering porcelain crown showed veneering layer fracture, the other 67% showed complete crown fracture. Conclusion: The fracture resistance of the whole zirconia crown are higher than the cast ceramic crown, the zirconia-veneering crown and the glass ceramic crown and the glass ceramic crown (CAD/CAM) is a very convenient prostheses. The failure modes are significantly influenced by the type of the crown.

Abstract: Complex geometric model can be reconstructed rapidly and accurately with reverse engineering technology which is an important engineering technology .This paper focuses on the CAD/CAE/CAM integrated technology of crown restorations based on RE technology .To construct satisfied 3D model , the digital model from RE technology is combined with and finite element analysis of CAE. Advanced manufacturing technology is used for manufacturing of resin materials crown. That is laser rapid manufactory technology.

Abstract: The quality demands of shape characteristics of strips have especially been increased recently by the modern industrial branches processing strips. The final shape of sheet is influenced by the construction and stiffness of mill stand and the shaping parameters through the deformation patterns of roll gap. The purpose of our research work was the modelling of shape-defects (crown) developing during cold rolling in order to increase the technological precision of production of sheets.

Abstract: The software CFDesign was used for the analysis of flow field simulation of two different kinds of drilling bit. The results showed that, if the waterway design of drilling bit was unreasonable, it could result in the following phenomenon: the local position of drilling bit could get severe erode of drilling fluid; the return of flow and eddy currents could be observed in the bottom of drilling well; negative pressure could be detected and might result in cavitation corrosion; the direction vector of flow field were diffused and resulted in cross flow. The waterway structure of arc-bottom bit was more reasonable comparing that of flat-bottom bit.

Abstract: A complete cast crown allows the operator to modify axial tooth contour. The margin should be smooth and distinct and its width has to allow adequate bulk of metal at the margin. The objective of this study was to evaluate, by finite element analysis, the influence of different degree of taper and marginal designs for cast crown preparations, on the stress distribution in teeth and crowns. As experimental model an upper first molar was used. The geometry of the intact tooth were obtained by 3D scanning. The tooth preparations and the complete cast crowns were designed. Models were exported in a finite element analysis software for structural simulations. Von Mises equivalent stresses were calculated and their distribution was plotted graphically. Numerical simulations provide a biomechanical explanation for stress distribution in prepared teeth and overlying crowns.

Abstract: 2638 branch samples are gained from the 14 sample spots and the data of 50 parse trees in the spots investigated by Muling Forestry Bureau in 2008. The type of the curve are determined by the observation of the radius(r) of various kinds of trees and the scatter diagram graph of crown depth (lx) . This paper is to use power function, single formula, parabola and hyperbolic function models to fit. Through the comparison of the results of fitting, it is found that the fitting effect of the average crow of Korean pine is the best whose correlation coefficient achieves 0.58, and for parabola, spruce and fir are the best respectively with correlation coefficient 0.69 and 0.72; The same model is applied to fit the outside shape of the three species and the result is similar with that of average crown: hyperbolic function of Korean pine is the best and parabola of spruce and fir are the best. After test, it is found that forecast accuracy of model is higher. Average crown of Korean pine is 95.7% and outside crown is 92.1%; Average crown of fir is 94.9% and outside crown is ：95.9%; Average crown of Spruce is 96.0% and outside crown is 95.4%. From the point of comprehensive results, the fitting of crown shape model is better and the model chosen can better describe the crown shape of the main conifer species in Muling area, achieving the desired objectives.

Abstract: In the manufacturing of slider, the final step is a dicing process of the rowbars into individual slider. However, in all slider separation processes seem to affect the curvature of the slider air bearing surface (ABS). As a result, the change in ABS crown and camber which can significantly affect the fly height of the slider. This paper investigates the influence of three types of dicing process, with the same feed rate and cutting speed, on the ABS curvature.

Abstract: SmartCrown work roll contour has been brought in China for several years, but the research of crown control characteristics of SmartCrown work roll is lacking, especially the relationship and difference between SmartCrown and CVC work rolls. The paper researched the principle and design method of SmartCrown work roll contour first, and then the relation and difference between the SmartCrown and CVC work roll contours were pointed out, the crown control ability of different strip width was discussed too. From the analysis and research, it can be concluded that the contour angle of SmartCrown work roll contour is the most key factor for its crown control characteristics.

Abstract: Asymmetrical rolling is usually used on some special rolling produce. It offers lower rolling pressure, more reduction and better crystallographic textures. In recent years asymmetrical rolling has become more important due to realization of improved properties of the strip. In this paper, a elasto-plastic finite element method code has been developed to simulate the asymmetrical rolling of strip, considering unequal roll radii, unequal speed ratio between the upper roll and lower roll, different exit thickness and different reduction. Meanwhile, The profile, crown and edge drop of strip, as well distribution of front tensile stress were discussed in different rolling process. It makes better preset values for the online control system and good results was obtained.

Abstract: This paper researches on the theory of the crown modification of cylinder-roller bearing raceway using electrochemical abrasive belt grinding (ECABG) technology, and establishes relevant experimental device. The range of processing parameters with a better surface roughness can be obtained through experiments. On this basis, a mathematics model of distribution of material removal of electrochemical machining bearing is set up. Considering the controllability of processing parameters and demand of the surface quality, the processing parameters such as interelectrode voltage, electrolyte, interelectrode gap and cathode geometry are invariable in the experiment, and processing time is changed to control the crown value. The experimental results show that ECABG can enhance the surface quality of raceway to a great degree, and obtain the ideal forming crown at the same time under the optimum technological parameters. This paper developed a new method for the crown processing and finishing of bearing raceway.