Finite element analysis case study

The JKR theory, similar to the Hertz theory, is a continuum theory in which two elastic semi-infinite bodies are in a non-conforming contact. Recently, the contact of layered solids has been addressed within the framework of the JKR theory. In a fundamental study, Sridhar et al. [32] analyzed the adhesion of elastic layers used in the SFA and compared it with the JKR analysis for a homogeneous isotropic half-space. As mentioned previously and depicted in Fig. 5, in SFA thin films of mica or polymeric materials ( i, /ji) are put on an adhesive layer Ej, I12) coated onto quartz cylinders ( 3, /i3). Sridhar et al. followed two separate approaches. In the first approach, based on finite element analysis, it is assumed that the thickness of the layers and their individual elastic constants are known in advance, a case which is rare. The adhesion characteristics, including the pull-off force are shown to depend not only on the adhesion energy, but also on the ratios of elastic moduli and the layers thickness. In the second approach, a procedure is proposed for calibrating the apparatus in situ to find the effective modulus e as a function of contact radius a. In this approach, it is necessary to measure the load, contact area... 

While a full scale experiment to investigate the seismic behavior of a real structure together with SSPW is hard to conduct, an analytical study with a well verified computational RC and soil model (Maekawa et al. 2003) can serve as an alternative to capture the overall efficiency of SSPW. In this study, the authors use a full three dimensional nonlinear finite element analysis of soil-structure-pore water systems. The applicability of the system was verified by shaking table experiments of top-heavy piles embedded in a liquefiable model foundation (Maki et al. 2004, 2005, Mohammed and Maekawa 2012 Mohammed et al. 2012a). Using this analytical platform, the effects of SSPW as a seismic countermeasure for the rafted pile foundation is discussed with regard to the base shear induced in the RC multistorey superstructure and its overall stability. Both cases of drained and undrained soils are considered in the analysis to clarify the potential effect of soil liquefaction. 

Dunmore Bridge case study An introduction to geotechnical engineering via finite element analysis... 

Corrosion-related SECM studies on both zirconium and hyperstoichiometric uranium oxide have been reported by Shoesmith and coworkers [70,71]. In both cases, their interest was in identifying areas of high cathodic activity on the substrate and then determining the electron transfer rate constant (k9) for sites of varying activity. Previously existing models for quantitative kinetic determinations have assumed a substrate of infinite dimensions. In practice, however, the active sites in localized corrosion investigations are often of dimensions similar to the microelectrode probe surface. Therefore, finite element analysis was utilized to generate theoretical PACs that allow for variation in the dimensions of both the active area and the probe, as well as in the level... 

The methods discussed earlier are applied to the seat-occupant-restraint system of an aircraft. A description of a computer-aided analysis environment, including a multibody model of the occupant and a nonlinear finite element model of the seat, is provided, which can be used to re-construct variety of crash scenarios. These detailed models are useful in studies of the potential human injuries in a crash environment, injuries to the head, the upper spinal column, and the lumbar area, and also structural behavior of the seat. The problem of reducing head injuries to an occupant in case of a head contact with the surroundings (bulkhead, interior walls, or instrument panels), is then considered. The head impact scenario is re-constructed using a nonlinear visco-elastic type contact force model. A measure of the optimal values for the bulkhead compliance and displacement requirements is obtained in order to keep the possibility of a head injury as little as possible. This information could in turn be used in the selection of suitable materials for the bulkhead, instrument panels, or interior walls of an aircraft. The developed analysis tool also allows aircraft designers/engineers to simulate a variety of crash events in order to obtain information on mechanisms of crash protection, designs of seats and safety features, and biodynamic responses of the occupants as related to possible injuries. 

Often, there may not be sufficient material test data to calibrate all the material parameters in a finite element model. In such cases, a sensitivity analysis is required to determine the sensitivity of the numerical results to the values of parameters that cannot be determined from material test data. A parametric study by Stavridis and Shing (2010) with finite element models has indicated that the shear strength parameters for mortar joints are most influential on the load-displacement response of an infilled frame. 

---