Neves Aline de A, Coutinho Eduardo, Cardoso Marcio V, Jaecques Siegfried, Lambrechts Paul, Sloten Jos Vander, Van Oosterwyck Hans, Van Meerbeek Bart
Katholieke Universiteit Leuven, Faculty of Medicine, Department of Conservative Dentistry, Leuven BIOMAT Research Cluster, Kapucijnenvoer 7, 3000 Leuven, Belgium.
J Dent. 2008 Oct;36(10):808-15. doi: 10.1016/j.jdent.2008.05.018. Epub 2008 Jul 22.
Describe stress distribution and compare stress concentration factor (K(t)) for homogeneous micro-specimens with different notch geometries and stick-shaped homogeneous and bimaterial specimens by means of finite element (FE) analysis.
Axisymmetric models were created for homogeneous specimens with different notches and for stick-shaped homogeneous and bimaterial specimens. FE mesh was refined at areas of expected stress concentration and boundary conditions included an applied tensile stress in the axial direction. Linear elastic analysis was used.
For hourglass homogeneous specimens, K(t) equaled 1.32 and 1.12 for a notch radius of 0.6mm and 3.3mm, respectively. A non-uniform axial (sigma(zz)) stress distribution was found in the notch cross-section, with values at the outer edge being 78% and 25% larger than at the center. In addition, a triaxial stress state was generated. Stick-shaped and dumbbell homogeneous specimens presented K(t)=1 and a uniform, uniaxial stress distribution along the entire cross-section. Shear stresses were zero for all homogeneous specimens. When an adhesive interface was added to the stick-shaped specimen, an area of localized axial stress concentration (K(t)=1.55) was detected at the bimaterial joint near the outer edge. Normal stresses sigma(rr) and sigma(thetatheta) and shear stress tau(zr) were also non-zero at the free-edge.
Dumbbell or stick-shaped specimens are favored for muTBS testing, as they do not present stress concentrations due to geometry. However, dissimilar mechanical properties of joint components will lead to stress concentrations and non-uniform multi-axial stresses, although to a lesser extent.
通过有限元（FE）分析，描述不同缺口几何形状的均质微试样以及棒状均质和双材料试样的应力分布，并比较应力集中系数（K(t)）。
为具有不同缺口的均质试样以及棒状均质和双材料试样创建轴对称模型。在预期应力集中区域细化有限元网格，边界条件包括在轴向施加拉伸应力。采用线弹性分析。
对于沙漏形均质试样，缺口半径为0.6mm和3.3mm时，K(t)分别等于1.32和1.12。在缺口横截面中发现轴向（σ(zz)）应力分布不均匀，外边缘处的值比中心处大78%和25%。此外，产生了三轴应力状态。棒状和哑铃形均质试样的K(t)=1，且沿整个横截面具有均匀的单轴应力分布。所有均质试样的剪应力均为零。当在棒状试样上添加粘结界面时，在外边缘附近的双材料接头处检测到局部轴向应力集中区域（K(t)=1.55）。自由边缘处的法向应力σ(rr)和σ(θθ)以及剪应力τ(zr)也不为零。
哑铃形或棒状试样有利于进行微拉伸粘结强度（muTBS）测试，因为它们不会因几何形状而出现应力集中。然而，接头部件不同的力学性能会导致应力集中和不均匀的多轴应力，尽管程度较小。
