Campillo-Funollet Marc, Dargush Gary F, VanSlooten Richard A, Mollendorf Joseph C, Kim Hyeongil, Makowka Steven R
Department of Restorative Dentistry, SUNY at Buffalo, Buffalo, NY, USA.
Department of Mechanical and Aerospace Engineering, SUNY at Buffalo, Buffalo, NY, USA.
Dent Mater. 2014 Aug;30(8):e216-28. doi: 10.1016/j.dental.2014.03.010. Epub 2014 Apr 29.
The aim of this study is to explain the influence of peripheral interface stress singularities on the testing of tensile bond strength. The relationships between these theoretically predicted singularities and the effect of specimen size on the measured bond strength are evaluated.
Finite element method (FEM) and boundary element method (BEM) analyses of microtensile bond strength test specimens were performed and the presence of localized high stress concentrations and singularities was analyzed. The specimen size effect predicted by the models was compared to previously published experimental data.
FEM analysis of single-material trimmed hour-glass versus cast cylindrical specimens showed different theoretical stress distributions, with the dumbbell or cylindrical specimens showing a more homogeneous distribution of the stress on the critical symmetry plane. For multi-material specimens, mathematical singularities at the free edge of the bonded interface posed a computational challenge that resulted in mesh-dependence in the standard FEM analysis. A specialized weighted-traction BEM analysis, designed to eliminate mesh-dependence by capturing the effect of the singularity, predicted a specimen size effect that corresponds to that published previously in the literature.
The results presented here further support the attention to specimen dimensions that has already broadened the empirical use of the microtensile test methods. FEM and BEM analyses that identify stress concentrations and especially marginal stress singularities must be accounted for in reliable bonding strength assessments. Size-dependent strength variations generally attributed to the effects of flaw distributions throughout the interfacial region are not as relevant as the presence of singularities at bonded joint boundaries - as revealed by both FEM and BEM analyses, when interpreted from a generalized fracture mechanics perspective. Furthermore, this size-dependence must be considered when evaluating or designing dental adhesive systems.
本研究旨在解释外周界面应力奇异性对拉伸粘结强度测试的影响。评估这些理论预测的奇异性与试样尺寸对测量粘结强度的影响之间的关系。
对微拉伸粘结强度测试试样进行有限元法（FEM）和边界元法（BEM）分析，并分析局部高应力集中和奇异性的存在。将模型预测的试样尺寸效应与先前发表的实验数据进行比较。
单材料修整沙漏形试样与铸造圆柱形试样的有限元分析显示出不同的理论应力分布，哑铃形或圆柱形试样在临界对称面上的应力分布更均匀。对于多材料试样，粘结界面自由边缘处的数学奇异性带来了计算挑战，导致标准有限元分析中存在网格依赖性。一种专门设计的加权牵引边界元分析，旨在通过捕捉奇异性的影响来消除网格依赖性，预测了与文献中先前发表的结果相符的试样尺寸效应。
此处给出的结果进一步支持了对试样尺寸的关注，这已经扩大了微拉伸测试方法的实际应用。在可靠的粘结强度评估中，必须考虑识别应力集中尤其是边缘应力奇异性的有限元法和边界元法分析。从广义断裂力学角度解释时，有限元法和边界元法分析均表明，通常归因于整个界面区域缺陷分布影响的尺寸依赖性强度变化，不如粘结接头边界处奇异性的存在那么重要。此外，在评估或设计牙科粘结系统时必须考虑这种尺寸依赖性。
