The objective of this project is to develop a methodology to measure and predict the strength and the stiffness of red alder (Alnus rubra) nailed pallet connections subjected to repetitive loading. Joint tests were conducted to define the mechanical properties of bottom block pallet connections. The primary tests were conducted to define the strength and stiffness of joint specimens tested in cyclic lateral loading, using three different side member thicknesses and four types of nails. Also, the influence of other specific variables on joint performance was evaluated including friction, pattern, moisture content, number of nails per joint, specific gravity, and rate of loading. In total, 23 sets of nailed joint specimens, with 15 replications each, were constructed and tested. The use of a reversing cyclic lateral loading procedure permits documentation of the effect of dynamic loading on the load-slip response of the connection. Analysis of the data included the creation of two envelope curves, the initial and the final (stabilized) curve. The data obtained from the two curves was used to find the “best” model for predicting the strength and stiffness of the connections. Four models were identified but only one of these was found useful for prediction purposes. Finally, experimental capacity loads were found to be at least three times greater than the national design specification allowable design loads. / Master of Science

Experimental evaluations of impact damage resistance and residual compression strengths after impact are presented for nine laminated fiber reinforced composite material systems. The experiments employ a small scale specimen for assessing the impact damage resistance and impact damage tolerance of these materials. The damage area detected by C-scan is observed to develop linearly with the impact velocity for impact velocities higher than a threshold value. Brittle material systems have lower threshold velocities and higher damage area growth rates than toughened systems. The impact damage resistance of each material system can be characterized with threshold velocity V_c and damage area growth rate C. The residual compressive Strength after impact was observed to decrease linearly with the damage area equivalent diameter. The rate of compressive strength reduction, K_d, has been observed to be independent of the material properties. The impact damage can be simulated from quasi-static indentation test in which the damage due to these two loading conditions are quite similar. The residual compressive strength can also be simulated from specimens with similar damage size resulting from quasi-static indentation load. / Ph. D.

An iterative penalty finite element model is developed for the analysis of three-dimensional coupled incompressible fluid flow and heat transfer problems. The pressure is calculated by solving the momentum equation using known values of velocities, velocity gradients, and flow stresses from previous iteration. An iterative solution algorithm which employs the element-by-element data structure of the finite element equations is used to solve large systems of algebraic equations resulting from finite element models of real world problems. Three different iterative methods (ORTHOMIN, ORTHORES and GMRES) are implemented and tested to determine the efficiency of each algorithm terms of CPU time and storage requirements. Jacobi/Diagonal preconditioning is used to scale the system of equations and improve the convergence of the iterative solvers. The developed iterative penalty finite element model is extended to analyse three-dimensional manufacturing processes such as casting, extrusion and forming of metals. For numerical simulation of extrusion and forming, flow formulation is used since these operations involve large deformations. The viscosity of the metal at elevated temperatures is calculated from the flow stress. The formulation uses the enthalpy method to account for the transfer of latent heat during phase change. The fluid inside the mushy region (between liquid and solid regions) is assumed to obey D’Arcy’s law for flow through porous materials. The permeability of the material is determined as a function of liquid fraction. This forces the velocities in the solid region to zero. In the finite element model, the effects of convection during phase change of the material are included. A method for calculation of the movement of liquid metal-air interface during mold filling process is presented. The developed model predicts the location of the interface (defined by a pseudo-concentration value) by solving for its movement due to forced convection. Also during filling analysis, only the filled and interface elements are used for flow field calculations. / Ph. D.

Optimization of compaction in granular material without the use of traditional ground improvement methods may be possible by optimizing the percentage of finer material and the median grain size ratio in binary soil mixtures. In this study, the median grain size ratio D50/d50 was explored as a fundamental parpmeter affecting the compaction characteristics of binary mixes made from natural sands as opposed to singular measurements such as fines content and mean grain size traditionally used to represent granular soils. A total of 18 binary granular mixes were synthetically generated from natural sands obtained from Longboat Key, Florida and evaluated through grain size analysis, laboratory compaction and determination of relative density. Results indicate that the D50/d50 ratio shows promise as a fundamental parameter for compaction optimization in binary mixes with values exceeding six approaching the densest packing configuations. / by Tara Devine Brenner. / Thesis (M.S.C.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Dynamic tensile characterization of geo-materials is critical to the modeling and design of protective structures that are often made of concrete. One of the most commonly used techniques currently associated with this type of testing is performed with a Kolsky bar and is known as the spall technique. The validity of the data from the spall technique is highly debated because the necessary boundary conditions for the experiment are not satisfied. By using a technique called pulse shaping, a new “controlled” spall technique was developed to satisfy all boundary conditions so that the analyzed data may be useful in modeling and design. The results from this project were promising and show the potential to revolutionize the way Kolsky bar testing is performed.

In this thesis, artificial neural networks (ANNs) are used to model helicopter main rotor dynamic loads as a function of flight variables. The motivation to develop an accurate model of such loads is to reduce maintenance and replacement costs by eliminating excessive conservatism currently associated with structural fatigue estimation. Neural networks are used for the modeling procedure because of their capability to model complex, nonlinear relationships for multiple input-multiple output systems. In support of the dynamic loads modeling discussed above, this thesis also briefly reviews artificial neural network technology, and investigates the modeling of a well-known dynamic system using ANNs. / Master of Science

This thesis aims to develop a new type of highly stretchable strain sensor to measure large deformation of a specimen subjected to dynamic loading. The sensor was based on the piezo-resistive response of carbon nanotube(CNT)/polydimethysiloxane (PDMS) composites thin films, some nickel particles were added into the sensor composite to improve the sensor performance. The piezo-resistive response of CNT composite gives high frequency response in strain measurement, while the ultra-soft PDMS matrix provides high flexibility and ductility for large strain measuring large strain (up to 26%) with an excellent linearity and a fast frequency response under quasi-static test, the delay time for high strain rate test is just 30 μs. This stretchable strain sensor is also able to exhibit much higher sensitivities, with a gauge factor of as high as 80, than conventional foil strain gauges.

Indiana University-Purdue University Indianapolis (IUPUI) / Predictability of tooth displacement in response to specific orthodontic load system directly links to the quality and effectiveness of the treatment. The key questions are how the tooth’s environment changes in response to the orthodontic load and how the biological tissues respond clinically. The objectives of this study are to determine the mechanical environment (ME) changes and to quantify the biological tissues’ response. Eighteen (18) patients who needed maxillary bilateral canine retractions were involved in the study. A method was developed to quantify the 3D load systems on the canine, which allowed the treatment strategies to be customized in terms of orthodontic loading systems to meet either translation (TR) or controlled tipping (CT) requirement. Dental casts were made before and after each treatment interval, and the Cone Beam Computed Tomography (CBCT) scans were taken prior to and following the entire treatment for control of treatment strategy and post treatment evaluations. Finite element method (FEM) was applied to calculate the location of center of resistance (CRes) for tooth movement control. The location and variation of CRes were recorded and compared with previous studies. A quick CRes assessment method that locates CRes by calculating the centroid of the contact surface (CCS) and the centroid of the projection of root surface (CPCS) in certain direction was also tested and compared with the results from FEM. Customized T-loop spring, a kind of orthodontic appliance, was designed, fabricated, and calibrated on a load measuring system to ensure that the load met the clinician’s prescription. The treatment outcomes in terms of tooth displacement and root resorption characterized by the changes of tooth length and volume as well as the bone mineral density (BMD) represented by the Hounsfield units (HU) change were recorded and analyzed. The ME in terms of stress were also calculated by using FEM. Paired t-test and mixed model ANOVA methods were used to analyze the relationships between the mechanical inputs (quantified and customized load, and corresponding stress) and clinical outcomes (root resorption and BMD change). It was found that the overall root resorption is not significant for canine retraction, but apical root resorption does occur, meaning that orthodontic load is not a sufficient factor. Also, it was observed that HU distribution changed significantly in both root and alveolar bone. The maximum reduction was on the coronal level in the direction perpendicular to the direction of movement in root, and in the direction of the tooth movement at the coronal level in bone. In addition, it was determined that the locations of the CRes in the MD and BL directions were significantly different. The locations of the CRes of a human canine in MD and BL directions can be estimated by finding the CPCSs in the two directions. Finally, it was shown that the stress invariants can be used to characterize how the osteocytes feel when ME changes. The stress invariants in the alveolar bone are not significantly affected by different M/F. The higher bone modeling/remodeling activities along the direction of tooth movement may be related to the initial volumetric increase and decrease in the alveolar bone.

In this study the description and development of intensity-based laser interferometric techniques for the detection and measurement of ultrasonic stress waves and their small displacement amplitudes is presented. The dynamic displacement sensitive interferometers described in the following chapters allow the quantitative point-by-point measurement of both in-plane and out-of-plane components of surface displacement motion. These uniquely developed interferometric sensors are: 1) an optical system design for the detection of the surface acoustic wave (Rayleigh wave). The technique is based on the Fourier analysis of coherent light and diffraction imaging properties of an illuminated grating; 2) the design and construction of a two-beam unequal-path laser interferometer for the measurement of out-of-plane surface displacement of ultrasonic waves; 3) extension of a flexible fiber optic probing device which is optically coupled to the test arm of the above two-beam interferometer. This permits scanning of the test surface which may be at some distance from the main optical system components; 4) the design and construction of a laser speckle interferometer for retro-reflective diffusing surfaces in which the in-plane displacements of the ultrasonic wave are interrogated. The inherent advantages of these newly designed optical configurations in terms of their greater simplicity, feasibility, and sensitivity over the conventional counterparts (classical/speckle laser interferometers) are explained. The function-response limitations of these interferometric sensors on lateral displacement resolution, on upper and lower-bound displacement sensitivity (dynamic range), on high-frequency bandwidth probing capability, on low-frequency environmentally associated noise disturbance, and on specularly reflective or diffusively retro-reflective specimen surface preparation are also mentioned. Finally, in a series of experimental observations, the application of a couple of these acoustic sensors in pulsed-excitation ultrasonic Specifically, the optically testing methods is cited. detected ultrasonic signals revealing the true nature of the various surface displacement modes of vibration are presented. / Ph. D.

Indiana University-Purdue University Indianapolis (IUPUI) / Quantification of treatment outcomes (tooth displacement and bony changes) is the key to advance orthodontic research and improve clinical practices. Traditionally, treatment outcome were quantified by using two-dimensional (2D) cephalometric analysis. However, there are problems inherent in 2D analysis, such as tracing errors and inability to detect side-effects. Thus, a reliable three-dimensional (3D) image analysis method for treatment outcome quantification is of high interest. Systematic 3D image analysis methods were developed for digital dental cast models and Cone-Beam Computed Tomography (CBCT) models. A typical analysis procedure includes image reconstruction, landmarks identification, coordinate system setup, superimposition, and displacement or change calculation. The specified procedures for maxillary teeth displacements and anatomical landmarks movements were presented and validated. The validation results showed that these procedures were accurate and reliable enough for clinical applications. The 3D methods were first applied to a human canine retraction clinical study. The purposes of this study were to quantify canines and anchorage tooth movements, and to compare two commonly used canine retraction strategies, controlled tipping and translation. The canine results showed that (1) canine movements were linear with time; (2) the initial load system was not the only factor that controlled the canine movement pattern; and (3) control tipping was significantly faster than translation. The anchorage tooth results showed that (1) anchorage losses occurred even with transpalatal arch (TPA); (2) there was no significant difference in anchorage loss between the two treatment strategies; and (3) compared with removable TPA, fixed TPA appliance can significantly reduce the amount of anchorage loss in the mesial-distal direction. The second clinical application for the 3D methods was a mandibular growth clinical trial. The purposes of this study were to quantify skeletal landmark movements, and compare two widely used appliances, Herbst and MARA. The results showed that (1) the Herbst appliance caused mandibular forward movement with backward rotation; and (2) the treatment effects had no significant differences by using either Herbst or MARA appliances. The two clinical applications validated the methods developed in this study to quantify orthodontic treatment outcomes. They also demonstrated the benefits of using the 3D methods to quantify orthodontic treatment outcomes and to test fundamental hypotheses. These 3D methods can easily be extended to other clinical cases. This study will benefit orthodontic patients, clinicians and researchers.