Finite element analysis with explicit time integration is widely used in commercial crash solvers to accurately simulate transient structural problems involving large-deformation and nonlinearity. Technological advances in computer software and hardware have expanded the boundaries of computational expense, allowing designers to analyse increasingly complex structures on desktop computers. This dissertation is a review of the use of finite element analysis for crash simulation, the principles of crashworthy design and a practical application of these methods and principles in the development of a concept energy absorber for a sailplane. Explicit nonlinear finite element analysis was used to do crash simulations of the glass, carbon and aramid fibre cockpit during the development of concept absorbers. The SOL700 solution sequence in MSC Nastran, which invokes the LS-Dyna solver for structural solution, was used. Single finite elements with Hughes-Liu shell formulation were loaded to failure in pure tension and compression and validated against material properties. Further, a simple composite crash box in a mass drop experiment was simulated and compared to experimental results. FEA was used for various crash simulations of the JS1 sailplane cockpit to determine its crashworthiness. Then, variants of a concept energy absorber with cellular aluminium sandwich construction were simulated. Two more variants constructed only of fibre-laminate materials were modelled for comparison. Energy absorption and specific energy absorption were analysed over the first 515 mm of crushing. Simulation results indicate that the existing JS1 cockpit is able to absorb energy through progressive crushing of the frontal structure without collapse of the main cockpit volume. Simulated energy absorption over the first 515 mm was improved from 2232 J for the existing structure, to 9 363 J by the addition of an energy absorber. Specific energy absorption during the simulation was increased from 1063 J/kg to 2035 J/kg. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

Master of Science / Department of Mechanical and Nuclear Engineering / Kevin B. Lease / The purpose of this study was to experimentally characterize the compressive and shear behavior of square cell titanium honeycomb cores according to the American Society of Testing and Materials Standards C 365-05 and C 273-06. By varying the honeycomb cell size and height as well as the foil thickness, many configurations of titanium honeycomb were manufactured utilizing a laser welding and expansion method. The test matrix consisted of 1080 compression and 1080 shear specimens. The compression specimens were split evenly into stabilized and unstabilized tests, and the shear specimens were split evenly to test three different shear orientations. At the conclusion of the characterization, a comprehensive statistical analysis was performed on the data. It was determined that both the compressive and shear strengths have a strong dependence on the relative density of the honeycomb. The compressive strength was found to be slightly affected by the presence of a stabilizing face sheet, and largely unaffected by specimen core height. The compressive modulus was affected by both the core height and the presence of a face sheet. Shear strength was found to decrease with increasing core height and was influenced by the shear orientation. Additionally, the rate of increase of shear modulus with respect to relative density was proportional to core height. Although no clear trend was observed, orientation did seem to have an effect on shear modulus. The compression and shear behavior of the honeycomb was compared with experimental results of honeycomb from existing publications and found to be consistent.

<p>In the industry, all passenger vehicles are treated with damping materials to reduce structure-borne sound. Though these damping materials are effective to attenuate structure-borne sound, they have little or no effect on the air-borne sound transmission.The lack of effective predictive methods for assessing the acoustic effects due to added damping on complex industrial structures leads to excessive use of damping materials.Examples are found in the railway industry where sometimes the damping material applied per carriage is more than one ton. The objective of this thesis is to provide a better understanding of the application of these damping materials in particular when applied to lightweight sandwich panels.</p><p>As product development is carried out in a fast pace today, there is a strong need for validated prediction tools to assist in the design process. Sound transmission loss of sandwich plates with isotropic core materials can be accurately predicted by calculating the wave propagation in the structure. A modified wave propagation approach is used to predict the sound transmission loss of sandwich panels with honeycomb cores. The honeycomb panels are treated as being orthotropic and the wave numbers are calculated for the two principle directions. The orthotropic panel theory is used to predict the sound transmission loss of panels. Visco-elastic damping with a constraining layer is applied to these structures and the effect of these damping treatment on the sound transmission loss is studied. Measurements are performed to validate these predictions.</p><p>Sound radiated from vibrating structures is of great practical importance.The radiation loss factor represents damping associated with the radiation of sound as a result of the vibrating structure and can be a significant contribution for structures around the critical frequency and for composite structures that are very lightly damped. The influence of the radiation loss factor on the sound reduction index of such structures is also studied.</p> / QC 20100519 / ECO2-Multifunctional body Panels

Master of Science / Department of Civil Engineering / Hani G. Melhem / Fiber Reinforced Polymer (FRP) is a relatively new material used in the field of civil engineering. FRP is composed of fibers, usually carbon or glass, bonded together using a polymer adhesive and formed into the desired structural shape. Recently, FRP deck panels have been viewed as an attractive alternative to concrete decks when replacing deteriorated bridges. The main advantages of an FRP deck are its weight (roughly 75% lighter than concrete), its high strength-to-weight ratio, and its resistance to deterioration. In bridge design, AASHTO provides load distributions to be used when determining how much load a longitudinal beam supporting a bridge deck should be designed to hold. Depending on the deck material along with other variables, a different design distribution will be used. Since FRP is a relatively new material used for bridge design, there are no provisions in the AASHTO code that provides a load distribution when designing beams supporting an FRP deck. FRP deck panels, measuring 6 ft x 8.5’, were loaded and analyzed at KSU over the past 4 years. The research conducted provides insight towards a conservative load distribution to assist engineers in future bridge designs with FRP decks. Two separate test periods produced data for this thesis. For the first test period, throughout the year of 2007, a continuous FRP panel was set up at the Civil Infrastructure Systems Laboratory at Kansas State University. This continuous panel measured 8.5 ft by 6 ft x 6 in. thick and was supported by 4 Grade A572 HP 10 x 42 steel beams. The beam spacing’s, along the 8.5 ft direction, were 2.5 ft-3.5 ft-2.5 ft. Stain gauges were mounted at mid-span of each beam to monitor the amount of load each beam was taking under a certain load. Linear variable distribution transformers (LVDT) were mounted at mid-span of each beam to measure deflection. Loads were placed at the center of the panel, with reference to the 6 ft direction and at several locations along the 8.5 ft direction. Strain and deflection readings were taken in order to determine the amount of load each beam resisted for each load location. The second period of testing started in the fall of 2010 and extended into January of 2011. This consisted of a simple-span/cantilever test set-up. The test set-up consisted of, in the 8.5 ft direction, a simply supported span of 6 ft with a 2.5 ft cantilever on one side. As done previously both beams had strain gauges along with LVDTs mounted at mid-span. There were also strain gauges were installed spaced at 1.5ft increments along one beam in order to analyze the beam behavior under certain loads. Loads were once again applied in the center of the 6 ft direction and strain and deflection readings were taken at several load locations along the 8.5 ft direction. The data was analyzed after all testing was completed. The readings from the strain gauges mounted in 1.5 ft increments along the steel beam on one side of the simple span test set-up were used to produce moment curves for the steel beam at various load locations. These moment curves were analyzed to determine how much of the panel was effectively acting on the beam when loads were placed at various distances away from the beam. Using these “effective lengths,” along with the strain taken from the mid-span of each beam, the loads each beam was resisting for different load locations were determined for both the continuously supported panel and the simply supported/cantilever panel data. Using these loads, conservative design factors were determined for FRP panels. These factors are S/5.05 for the simply supported panel and S/4.4 for the continuous panel, where “S” is the support beam spacing. Deflections measurements were used to validate the results. Percent errors, based on experimental and theoretical deflections, were found to be in the range of 10 percent to 40 percent depending on the load locations for the results in this thesis.

Electronic platforms that are able to re-shape and assume different geometries are attractive for the advancing biomedical technologies, where the re-shaping feature increases the adaptability and compliance of the electronic platform to the human body. In this thesis, we present a serpentine-honeycomb reconfigurable electronic platform that has the ability to reconfigure into five different geometries: quatrefoil, ellipse, diamond, star and one irregular geometry. We show the fabrication processes of the serpentine-honeycomb reconfigurable platform in a micro-scale, using amorphous silicon, and in a macro-scale using polydimethylsiloxane (PDMS). The chosen materials are biocompatible, where the silicon was selected due to its superior electrical properties while the PDMS was selected due to its unique mechanical properties. We study the tensile strain for both fabricated-versions of the design and we demonstrate their reconfiguring capabilities. The resulting reconfiguring capabilities of the serpentine-honeycomb reconfigurable platform broaden the innovation opportunity for wearable electronics, implantable electronics and soft robotics.

In this thesis we present results from quantum Monte Carlo for the fully-frustrated honeycomb lattice. The XXZ model is of interest in the classical limit, as there is a mapping between the classical fully-frustrated honeycomb Ising model groundstates and the classical hard-core dimer model groundstate. The aim of this work is to explore the effect of quantum fluctuations on the fully-frustrated honeycomb model to see what sort of interesting physics arises. One might expect unusual physics due to the quantum hard-core dimer model, where interesting physics are known to exist. This is because there is a duality mapping between the classical dimer model and the classical fully-frustrated honeycomb Ising model. Indeed, by studying the fully-frustrated honeycomb XXZ model we find that in some cases the system orders into crystal-like structures, a case of order-by-disorder. The most interesting case, when the frustrating bonds are chosen randomly, reveals to us a novel state without any discernible order while at the same time avoiding the freezing one would expect of a glass. This state is a featureless system lacking low temperature magnetic susceptibility---a candidate ``quantum spin liquid''. Future work that might more easily measure quantum spin liquid criteria is suggested.

In the production of iron chromium honeycombs, iron oxide and chromium oxide mixtures are reduced by hydrogen at elevated temperatures to produce a metallic alloy. The complete reduction of the iron oxide occurs prior to the reduction of the chromium oxide. The reduction of the chromium oxide particles within the iron matrix is affected by factors that include the diffusion of the reduced chromium away from the chromium oxide particle into the iron matrix, the diffusion of the gaseous reactants and products to and from the chromium oxide particles, and the porosity of the iron matrix, which changes as a result of sintering. The type of heat-treatment used, (isothermal or non-isothermal, i.e., holding at a specific temperature versus using a steadily increasing temperature) plays a vital role in how these factors will affect chromium oxide reduction. Experimental data were used in conjunction with sintering and dissolution models to obtain an understanding of the environment in which the chromium oxide particles reduce as a function of heat-treatment. This understanding will assist in the development of more effective processing steps for the reduction of metallic honeycombs from oxide mixtures.

In this thesis, design and analyses of honeycomb structures are investigated. Primary goal is to develop an equivalent orthotropic material model that is a good substitute for the actual honeycomb core. By replacing the actual honeycomb structure with the orthotropic model, during the finite element analyses, substantial advantages can be obtained with regard to ease of modeling and model modification, solution time and hardware resources . To figure out the best equivalent model among the approximate analytical models that can be found in the literature, a comparison is made. First sandwich beams with four different honeycomb cores are modeled in detail and these are accepted as reference models. Then a set of equivalent models with the same dimensions is generated. The material properties of the equivalent models are taken from different studies performed in the literature. Both models are analyzed under the same loading and the boundary conditions. In finite element analyses, ANSYS finite element program is used. The results are compared to find out the best performing equivalent model. After three major analyses loops, decision on the equivalent model is made. The differences between the total reaction forces calculated by the equivalent model and the actual honeycomb model are all found to be within 10%. The equivalent model gives stress results at the macro-scale, and the local stresses and the strains can not be determined. Therefore it is deemed that for stress analysis, equivalent model can be used during the preliminary design phase. However, the equivalent model can be used reliably for deflection analysis, modal analysis, stiffness determination and aero-elastic analysis.

In this work, the steady-state performance of zeolite-based (Cu-ZSM-5) and vanadium-based honeycomb monolith catalysts was investigated in the selective catalytic reduction process (SCR) for NO removal using NH3. The aim was to delineate the effect of various parameters including pretreatment of the catalyst sample with H2, NH3-to-NO ratio, inlet oxygen concentration, and space velocity. The concentrations of the species (e.g. NO, NH3, and others) were determined using a Fourier Transform Infrared (FTIR) spectrometer. The temperature was varied from ambient (25 C) to 500 C. The investigation showed that all of the above parameters (except pre-treatment with H2) significantly affected the peak NO reduction, the temperature at which peak NO reduction occurred, and residual ammonia left at higher temperatures (also known as 'NH3 slip'). Depending upon the particular values of the parameters, a peak NO reduction of around 90% was obtained for both the catalysts. However, an accompanied generation of N2O and NO2 species was observed as well, being much higher for the vanadium-based catalyst than for the Cu-ZSM-5 catalyst. For both catalysts, the peak NO reduction decreased with an increase in space velocity, and did not change significantly with an increase in oxygen concentration. The temperatures at which peak NO reduction and complete NH3 removal occurred increased with an increase in space velocity but decreased with an increase in oxygen concentration. The presence of more ammonia at the inlet (i.e. higher NH3-to-NO ratio) improved the peak NO reduction but simultaneously resulted in an increase in residual ammonia. Pretreatment of the catalyst sample with H2 (performed only for the Cu-ZSM-5 catalyst) did not produce any perceivable difference in any of the results for the conditions of these experiments.

In high-pressure centrifugal compressors, honeycomb seals are often used as replacements for labyrinth seals to enhance dynamic stability. A concern exists with the loss of this enhanced stability if the honeycomb cavities become clogged with debris over time. So, as a first objective, static and dynamic tests were conducted on a constant-clearance honeycomb and a constant-clearance smooth-bore seal under three inlet preswirl conditions to determine the effects of inlet preswirl. The resulting leakage flowrate and dynamic parameters, effective stiffness and damping of the seal, were measured for each seal and then compared, with the smooth-bore seal representing the honeycomb seal with completely clogged cells. The second objective was to evaluate a two-control volume theory by Kleynhans and Childs with the measured data under the influence of preswirl. Both seals have a 114.7mm bore with a radial clearance of 0.2mm from the test rotor. The honeycomb seal has a cell width of 0.79mm and cell depth of 3.2mm. The target test matrix for each preswirl setting consisted of three exit-to-inlet pressure ratios of 15%, 35%, and 50%, and three rotor speeds out to 20,200 rpm. The target inlet air pressure was 70 bar-a. Experimental results show that, for a clean honeycomb seal, preswirl has little effect on effective stiffness, Keff*, and decreases effective damping, Ceff*, by about 20% at the high inlet preswirl ratio (~0.6). However, comparing smooth and honeycomb seal results at higher inlet preswirl shows a potential reduction in Keff* by up to 68%, and a large drop and shift in positive Ceff* values, which could cause an instability in the lower frequency range. Measured leakage shows a potential increase of about 80%, regardless of test conditions. A swirl brake at the seal entrance would fix this loss in stability by significantly reducing inlet preswirl. The two-control-volume theory model by Kleynhans and Childs seems to follow the frequency-dependent experimental data well for the honeycomb seal. Theory predicts conservatively (under-predicts) for stability parameters such as k* and Ceff* and for leakage. Predictions for K and Keff may possibly be improved with better measured friction factor coefficients for each seal.