ASME Sec VIII Div 3 Fatigue Life Predictions Using Critical Plane Approach

ASME VIII Div 3 fatigue evaluation is based on the theory that cracks tend to nucleate along the slip lines oriented in the maximum shear stress planes. This code provides methods to calculate the fatigue stresses when the principal stress direction does not change (proportional loading) and axes change (nonproportional loading). When principal stress direction does not change within a fatigue cycle, shear stress amplitude is calculated only on the three maximum shear stress planes. But when the principal stress directions do change within a loading cycle, the plane carrying the maximum shear stress amplitude (also known as critical plane) cannot be easily identified and all planes at a point needs to be searched for the maximum shear stress amplitude. This paper describes the development of an ANSYS-APDL macro to predict the critical plane at each surface node of an FE model using the FEA stress results. This macro searches through 325 planes (at 10° increments along two angles) at each surface node and for each load step to identify the maximum shear stress and the corresponding normal stress for each surface node. The fatigue life is calculated for each surface node and is plotted as a color contour on the FEA model. This macro can be extended to calculate the fatigue life using other critical plane approaches such as the Findley and Brown-Miller models.

Deformation and Stress Analysis of the Fullerene by Super Element

Accurate prediction of static and dynamic response of nano structures is one of the important interests of scientists in the last decade. Nano bearing as an important part of nano machines has been extensively implemented in recognizing and disassembling cancerous cells and building molecular support structures for strengthening bones. For this reason, Molecular Dynamic Method and some experimental methods are implemented in this area. As nano ball bearing is one of the most important components of nano machines, a large number of studies are concentrated to analyze it statically and dynamically. In this paper, a Fullerene is simulated by a spherical super element whose stress, deformation and natural frequency are calculated. The Fullerene is considered to be the C60 which is properly similar with a 66 surface-node spherical super element. In this study the mechanical properties of the fullerene and boundary conditions of the nano ball bearing under loading are introduced and stress and natural frequency of a fullerene under concentrated load is presented with two different strategies, super element and conventional elements. Compatible findings of these two methods validate and confirm the results. Findings indicate that applying 1 super element for the simulation of the fullerene leads to same results as implementing 154764 conventional elements.

Deformation, Stress and Natural Frequency Analysis of the Fullerene by Finite Super Element Method

Accurate prediction of static and dynamic response of nano structures is one of the important interests of scientists in the last decade. Nano bearing as an important part of nano machines has been extensively implemented in recognizing and disassembling cancerous cells and building molecular support structures for strengthening bones. For this reason, Molecular Dynamic Method and some experimental methods are implemented in this area. As nano ball bearing is one of the most important components of nano machines, a large number of studies are concentrated to analyze it statically and dynamically. In this paper, a Fullerene is simulated by a spherical super element whose stress, deformation and natural frequency are calculated. The Fullerene is considered to be the C60 which is properly similar with a 66 surface-node spherical super element. In this study the mechanical properties of the fullerene and boundary conditions of the nano ball bearing under loading are introduced and stress and natural frequency of a fullerene under concentrated load is presented with two different strategies, super element and conventional elements. Compatible findings of these two methods validate and confirm the results. Findings indicate that applying 1 super element for the simulation of the fullerene leads to same results as implementing 154764 conventional elements.