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Deflection and stress calculated from an experimentally validated, high-fidelity finite element model (FEM) of a photovoltaic module experiencing mechanical load was compared to results from a simplified FEM treating the module laminate as a homogenized composite using a rule of mixtures approach, and further compared to analytical calculations treating the module as a Kirchoff-Love flat plate. The goal of this study was to determine the error incurred by analyzing module mechanics with varying levels of simplification, since resolving the aspect ratios of a module is computationally expensive. Homogenized FEMs were found to underpredict peak deflection under a 1.0 kPa load by between 13 and 19% for lower and upper bound application of the rule of mixtures. However, module shape was captured, implying that a useful replication of a resolved model could be achieved with a reduced, calibrated material stiffness. Homogenized stress results captured glass layer tensile stress components to within 46 to 52% at a sample location of interest, though agreement was poor through the remainder of the laminate due to the lack of material resolution. For plate theory, deflection was overpredicted by 45 to 67% for upper and lower bound homogenizations, and frame-adjacent module shapes were not adequately replicated. Stress results mirrored FEM trends but magnitudes were not well correlated to resolved model values. These results support the use of homogenized laminate models for module shape derivation, though resolved models remain necessary for stress analyses. The accuracy of plate theory was found to be inadequate for most applications. [ABSTRACT FROM AUTHOR]

Indentation hardness tests are widely used in engineering to test the hardness of a material, which can be performed on a macroscopic scale or microscopic scale. In the present work, copper specimens with different thicknesses were indented with a mechanically-instrumented Rockwell tester. The effects of spacing between indents, indent distance to the edge of the sample, and specimen thickness on the hardness measurement were systematically quantified. Non-linear finite-element modeling was performed, assuming elastic-plastic material response with strain hardening. The two-dimensional numerical modeling of stand-alone and multiple indentations helped to shed more light on the deformation field under indentation, especially the size of the plastic zones and any interaction between them. In addition to the geometric effects, the influence of strain hardening of the test material was also investigated using the finite element analysis. The combined experimental and numerical results provided a range of indent spacings and thicknesses, which yield small to no effect on hardness values. The simulations also quantified the size and shape of the plastic zone under an indent. Lastly, the modeling results showed a competition between the effect of intrinsic material hardening and indent spacing on the value of the measured hardness. [ABSTRACT FROM AUTHOR]

Photonic crystals (PCs) are synthetic materials that are used to control light propagation. PCs have a frequency bandgap where light is forbidden to propagate. This bandgap is strongly tied to the microstructure of the photonic crystal. Three-dimensional tungsten photonic crystal in a Lincoln-log microstructure has been suggested as a strong alternative filter in photovoltaic cells with significantly high power efficiency. PCs have also been suggested as sensors for submicron damage. Therefore, mechanical characterization of three-dimensional photonic crystals becomes of interest. Here we report on mechanical characterization of tungsten PC using means of micro-indentation. We also present a three-dimensional finite element simulation of the structural response of a Tungsten photonic crystal under micro-indentation load. Stresses developed in the PC can be used to quantify the level of damage in the crystal. We compare our simulation results with the experimental observations of a Vickers and Knoop micro-indentation experiments of tungsten PC. The FE models were proven able to simulate the mechanical response of the PC with a good accuracy. The calibrated FE models can be further used to realize the mechanical behavior of PC under different thermal and mechanical stresses when used as filters in photovoltaic cells or to simulate the effect of damage in PC sensors. [ABSTRACT FROM AUTHOR]

Finite element (FE) modeling of the human dentate mandible is the method of choice currently used for simulating structural fracture analyses in the mandibular region. A finite element model of a parasymphyseal fracture with an internal rigid fixation plate-screw system has been developed to compare the effects of including frictionless/frictional contact boundary conditions at the fracture site. It is common practice to ignore contact boundary conditions in FE modeling of mandibular fractures due to the non-linearities causing increased computational requirements. The stress distributions and displacements of the mandibular fracture region indicate a significant difference resulting from the introduction of realistic contact boundary conditions. These current findings suggest that even though the modeling of extreme situations, i.e. non-contact modeling of unhealed fractures, may provide insight to non-union problems, future mandibular fracture models should include frictional contact boundary conditions. This is in order to capture more realistic behavior of the system to be analyzed. [ABSTRACT FROM AUTHOR]

Experimental and numerical methods are used to explore the stresses generated around bone screws used in rigid internal fixation of mandibular fractures. These results are intended to aid in decisions concerning both the design and the use of these bone screws. A finite element (FE) model of a human mandible is created with a fixated fracture in the parasymphyseal region. The mandibular model is anatomically loaded, and the forces exerted by the fixation plate onto the simplified screws are obtained and transferred to another finite element submodel of a screw implant embedded in a trilaminate block with material properties of cortical and cancellous bone. The stress in the bone surrounding the screw implant is obtained and compared for different screw configurations. The submodel analyses are further compared to and validated with simple axial experimental and numerical screw pull-out models. Results of the screw FE analysis (FEA) submodel show that a unicortical screw of 2.6mm major diameter and 1.0mm pitch will cause less bone damage than a bicortical screw of 2.3mm major diameter and 1.0mm pitch. The results of this study suggest that bicortical drilling can be avoided by using screws of a larger major diameter. [ABSTRACT FROM AUTHOR]

The article presents information on a finite element model of the human dentate mandible which has been developed for making comparison of fixation systems that are used for fracture reduction. The model presents volume domains for cortical bone, cancellous bone, and teeth which were created and meshed in ANSYS 8.0.