Thermal stresses Stress analysis models

Hart-Smith (references 5.25, 5.26, 5.30 and 5.31) has conducted extensive studies of bonded joints using the elastic—plastic model for the adhesive. He has covered the analysis of lap, strap, scarf and step-lap joints. He has modified the load eccentricity induced peel stress approach by using a modified bending stiffness. He has studied the effects of non-uniform adhesive thickness, adhesive non-uniform moisture absorbtion and defects in the bondline. He has also included thermal stresses in his models. 

Tbe preload in the hold-down bolts is introduced by means of thermal prestrain. This involves imposing artificial temperature in the bolts sufficiently lower than the assembly temperature to achieve the desired preload. By this method the bolt preload can be monitored very effectively. The temperatures in the reactor vessel support system are obtained using a thermal analysis that employs a model identical to Figure 12.8. The ledge temperature of 66° C is used as a boundary condition in the thermal analysis. The bolt temperature distribution is also evaluated in the thermal analysis. The computed bolt temperature is superimposed onto the fictitious bolt preload temperature. The stresses are evaluated in the stress analysis model using the computed temperatures. 

Thermal stress calculations in the five cell stack for the temperature distribution presented above were performed by Vallum (2005) using the solid modeling software ANSYS . The stack is modeled to be consisting of five cells with one air channel and gas channel in each cell. Two dimensional stress modeling was performed at six different cross-sections of the cell. The temperature in each layer obtained from the above model of Burt et al. (2005) is used as the nodal value at a single point in the corresponding layer of the model developed in ANSYS and steady state thermal analysis is done in ANSYS to re-construct a two-dimensional temperature distribution in each of the cross-sections. The reconstructed two dimensional temperature is then used for thermal stress analysis. The boundary conditions applied for calculations presented here are the bottom of the cell is fixed in v-dircction (stack direction), the node on the bottom left is fixed in x-direction (cross flow direction) and y-direction and the top part is left free to... 

In the case of heat transfer analysis, axial temperature distribution, shown in Figure 3 are specified for the surfaces of both He and sulfuric flow cannels, considering heat transfer coefficients. And outer surface of block is modeled as adiabatic condition. Figures 5 and 6 show the temperature and the stress distributions in the block, respectively. The stress shown in Figure 6 is a coupled stress with thermal stress and static stress caused by the operating pressure difference between He and sulfuric acid. Analytical conditions are as follows ... 

ON the basis of the hypothesis analysis model, this paper gives temperature distribution and thermal stress distribution of FGM. By using above formulas to calculate thermal stress in every layer, the optimum combination and distribution profile will be expected to obtain. 

R. L. Williamson, B. H. Rabin and J. T. Drake, "Finite Element Analysis of Thermal Residual Stresses at Graded Ceramic-Metal Interfaces, Part I Model Description and Geometrical Effects," /. Appl. Phys., 74 [2] 1310-1320 (1993). 

A computational design procedure of a thermoelectric power device using Functionally Graded Materials (FGM) is presented. A model of thermoelectric materials is presented for transport properties of heavily doped semiconductors, electron and phonon transport coefficients are calculated using band theory. And, a procedure of an elastic thermal stress analysis is presented on a functionally graded thermoelectric device by two-dimensional finite element technique. First, temperature distributions are calculated by two-dimensional non-linear finite element method based on expressions of thermoelectric phenomenon. Next, using temperature distributions, thermal stress distributions are computed by two-dimensional elastic finite element analysis. 

Thermoelectric analysis and thermal stress analysis are performed on single-stage thermoelectric generator by the finite element method. An analysis model is shown in Figure 5. The device is... 

The finite element (FE) model of the FSSW process was done using ABAQUS/Explicit software. A 3-D dynamic fully coupled thermal-stress analysis was performed to obtain thermomechanical responses of the FSSW process. Two features in the FE package were deployed in order to obtain the results ... 

NETL s CFD research has demonstrated that CFD-based codes can provide detailed temperature and chemical species information needed to develop improved fuel cell designs. The output of the FLUENT-based fuel cell model has been ported to finite element-based stress analysis software to model thermal stresses in the porous and solid regions of the cell. In principle, this approach can be used for other types of fuel cells as well, as demonstrated by Arthur D. Little and NETL (16,18)... 

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