金-瓷修复体粘弹性残余应力的有限元分析

The Study of Viscoelastic Residual Stresses of Ceramic-metal Bond

目的 分析烤瓷熔附金属修复体冷却过程中形成的残余应力与外载荷对金 -瓷结合力的影响 ,以准确描述金 -瓷结合力的大小 ,为进一步完善金 -瓷结合理论和预防崩瓷和瓷裂的发生提供依据。方法 参考国际标准化组织确定的测定金 -瓷结合力的三点弯曲实验试样建立有限元模型 ,采用粘弹性有限元法按冷却过程中粘弹性和弹性不同阶段进行分析 ,以粘弹性阶段的计算结果作为弹性阶段分析的初始条件将二者进行叠加。结果 修复体完成并施以加载后 ,瓷层材料承受金属施于的压应力 ;沿界面分布的残余应力和加载力形成的剪切力相互抵消 ;而垂直于界面分布的由加载力形成的拉应力远大于残余应力形成的压应力 ,并且趋向于界面边界点应力逐渐增大。结论 残余应力对金 -瓷结合有着极为重要的影响 ,而陶瓷材料的粘弹性对于准确分析残余应力十分重要。只要严格控制金属与瓷材料热膨胀系数的差异 ,残余应力的一些分力有利于金 -瓷结合 ,可以认为构成了金 -瓷结合力的一部分。

Objective To study the residual stresses of ceramic-metal bond at viscoelastic and elastic phases during cooling of porcelain-fused-to-metal in order to precisely calculate the ceramic-metal bond strength and improve the restorations.Methods The finite element model was set up according the crack initiation test (three-point flexure bond test) based on ISO Standard, elements of viscoelastic and thermal-displacement were used to part the model. The result at viscoelastic phases was used as initiation condition of elastic phases to add up.Results The compressive stress was caused by metal during cooling occurred in the ceramic. The shear stress induced by loading was offset by thermal shear stress. Load tensile stress and the thermal compressive stress vertical of interface concentrated at the end of the bond interface, but the tensile was greatly higher.Conclusion The residual stress is very important to metal-ceramic restorations, and the viscoelastic behavior of porcelain greatly influences it. If the metal and ceramic are compatible,the components stresses of the residual stresses may benefit to ceramic-metal bond, and can be taken as a part of bond stresses.