Department of Materials and Production, Aalborg University, Aalborg 9220, Denmark.
CMEMS, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal.
J Mech Behav Biomed Mater. 2018 Jan;77:461-469. doi: 10.1016/j.jmbbm.2017.10.005. Epub 2017 Oct 4.
The thermal residual stresses (TRSs) generated owing to the cooling down from the processing temperature in layered ceramic systems can lead to crack formation as well as influence the bending stress distribution and the strength of the structure. The purpose of this study is to minimize the thermal residual and bending stresses in dental ceramics to enhance their strength as well as to prevent the structure failure. Analytical parametric models are developed to evaluate thermal residual stresses in zirconia-porcelain multi-layered and graded discs and to simulate the piston-on-ring test. To identify optimal designs of zirconia-based dental restorations, a particle swarm optimizer is also developed. The thickness of each interlayer and compositional distribution are referred to as design variables. The effect of layers number constituting the interlayer between two based materials on the performance of graded prosthetic systems is also investigated. The developed methodology is validated against results available in literature and a finite element model constructed in the present study. Three different cases are considered to determine the optimal design of graded prosthesis based on minimizing (a) TRSs; (b) bending stresses; and (c) both TRS and bending stresses. It is demonstrated that each layer thickness and composition profile have important contributions into the resulting stress field and magnitude.
由于分层陶瓷系统从加工温度冷却下来而产生的热残余应力（TRS）会导致裂纹的形成，并影响弯曲应力分布和结构强度。本研究的目的是最小化牙科陶瓷中的热残余和弯曲应力，以提高其强度并防止结构失效。开发了分析参数模型来评估氧化锆-瓷多层和分级盘的热残余应力，并模拟活塞-环试验。为了确定基于氧化锆的牙科修复体的最佳设计，还开发了粒子群优化器。各层的厚度和组成分布被称为设计变量。还研究了构成两种基础材料之间的中间层的层数对分级修复系统性能的影响。所开发的方法学通过与文献中可用的结果和本研究中构建的有限元模型进行验证。考虑了三种不同情况，以基于最小化（a）TRS；（b）弯曲应力；和（c）TRS 和弯曲应力来确定分级修复体的最佳设计。结果表明，每层厚度和组成分布对产生的应力场和大小都有重要贡献。
