No description available.

Osteoporosis is a disease prevalent in older adults, characterized by increased bone porosity resulting in significant fracture risk. Orthopaedic implants are designed and validated against cadavers from the general ‘healthy’ population, but little is known about their response in osteoporotic bone. Orthopaedic implants can also be developed using synthetic bones, if they have been demonstrated to be representative of healthy bone, and offer a number of advantages. To date, no synthetic femur has been validated for the osteoporotic population. The purpose of this study was to assess novel synthetic femurs for representing this population. Custom jigs were manufactured to test two sets of ten synthetic femurs and five isolated cadaveric femurs in four-point bending, torsion, axial compression, axial failure, and screw pullout, using an Instron mechanical testing machine to record load-displacement data. Statistical significance was found in bending, torsion, and screw pullout between both synthetic sets and cadavers using one-way ANOVA with post-hoc Tukey analysis. In all instances, the synthetic femurs had lower coefficients of variation than natural specimens. Both synthetic and cadaveric femurs were CT scanned prior to testing. The data were used to measure key anatomical details and to develop a series of numerical models of the synthetic bones, using Materialize Mimics® and ABAQUS® software, evaluated using axial and bending data. The model was modified by reducing cortical thickness and modulus in an attempt to make the synthetic model better represent osteoporotic bone. Establishing synthetic femurs as suitable replacements for osteoporotic bone allows for improved orthopaedic implant development. The digital model constructed allows the synthetic to be further analyzed, improving expected response of the synthetic bones. These synthetic bones could provide a foundation for development of effective orthopaedics for this population. / Thesis / Master of Applied Science (MASc) / The considerations and parameters in the design of orthopaedic implants for osteoporotic bone are relatively unknown. Orthopaedic implants can be evaluated with synthetic bones, which offer a number of advantages to natural specimens, assuming they are sufficiently representative of natural bone. No physical synthetic model yet exists that represents an osteoporotic femur. In the present work, synthetic femurs were subjected to bending, torsion, axial compression, and screw pullout and compared to natural osteoporotic specimens. The synthetics were significantly different to natural specimens in bending, torsion, and screw pullout. A numerical model was created, evaluated, and tested in finite element software alongside modified models with reduced modulus and cortical thickness to assess stiffness. Recommendations were made to improve the accuracy of a future synthetic model. The synthetic femurs tested were not representative of osteoporotic femurs, but may be feasible alternatives with minor modifications and could be useful in future orthopaedics design.

Indiana University-Purdue University Indianapolis (IUPUI) / Lithium-Ion Batteries (Li-ion batteries or LIBs) have been extensively used in a wide variety of industrial applications and consumer electronics. Additive Manufacturing (AM) or 3D printing (3DP) techniques have evolved to allow the fabrication of complex structures of various compositions in a wide range of applications. The objective of the thesis is to investigate the application of 3DP to fabricate a LIB, using a modified process from the literature [1]. The ultimate goal is to improve the electrochemical performances of LIBs while maintaining design flexibility with a 3D printed 3D architecture. In this research, both the cathode and anode in the form of specifically formulated slurry were extruded into filaments using a high-temperature pellet-based extruder. Specifically, filament composites made of graphite and Polylactic Acid (PLA) were fabricated and tested to produce anodes. Investigations on two other types of PLA-based filament composites respectively made of Lithium Manganese Oxide (LMO) and Lithium Nickel Manganese Cobalt Oxide (NMC) were also conducted to produce cathodes. Several filaments with various materials ratios were formulated in order to optimize printability and battery capacities. Finally, flat battery electrode disks similar to conventional electrodes were fabricated using the fused deposition modeling (FDM) process and assembled in half-cells and full cells. Finally, the electrochemical properties of half cells and full cells were characterized. Additionally, in parallel to the experiment, a 1-D finite element (FE) model was developed to understand the electrochemical performance of the anode half-cells made of graphite. Moreover, a simplified machine learning (ML) model through the Gaussian Process Regression was used to predict the voltage of a certain half-cell based on input parameters such as charge and discharge capacity. The results of this research showed that 3D printing technology is capable to fabricate LIBs. For the 3D printed LIB, cells have improved electrochemical properties by increasing the material content of active materials (i.e., graphite, LMO, and NMC) within the PLA matrix, along with incorporating a plasticizer material. The FE model of graphite anode showed a similar trend of discharge curve as the experiment. Finally, the ML model demonstrated a reasonably good prediction of charge and discharge voltages.

To address the challenges associated with urban expansion and environmental changes, innovative interlocking concrete block pavement (ICBP) is being researched for usage in urban areas. The ICBP is designed to have higher durability and better long-term performance compared to traditional asphalt pavement. Using recycled concrete aggregates (RCA) and supplementary cementing materials (SCMs) can provide many environmental benefits. The objective of this research is to investigate the mechanical properties of concrete with recycled materials. This also involves the assessment of deflection and stresses associated with ICBP using the finite element method. Four concrete mixtures with different RCA and SCMs contents were designed and cast. The RCA replacement levels were 20% and 40%, while slag and glass pozzolan were added to improve mechanical properties. The results showed that the use of RCA had adverse impacts on workability. The 28 days compressive strength of the Control Mix was 40 MPa. The compressive strength of Mix 3 was 40.5 MPa which was the highest strength among all mixtures. It demonstrated that a 40% RCA replacement level could have a non-negative effect on mechanical properties when the SCMs are added. A three-dimensional pavement model was established using ABAQUS software. The orthogonal experimental design was used to evaluate the effects of the length/width ratio of blocks, the block thickness, the elastic modulus, and the laying pattern of blocks on the deflection and von Mises stress of all ICBP models under the vertical load. Considering the deflection of the loading area, the length/width ratio had the greatest effect, then comes with thickness, elastic modulus, and laying pattern according to the Range Analysis. The bigger block size and higher elastic modulus of blocks could provide even better performance. Overall, the herringbone laying pattern is recommended as the optimum laying pattern with minimum deflection. It also contributes to better load spreading. / Thesis / Master of Applied Science (MASc)

This research contributes to the development of a structural optimization software system designed to support design optimization. The focus of this thesis work is on formulating strategies to obtain accurate solutions and enhance the efficiency of the optimization process, particularly when dealing with large and complex finite element (FE) models, utilizing statistical concepts. A potential avenue explored in this study is the adaptive response surface optimization process. The adaptive response surface optimization method involves the adaptive control of samples selected through the design of experiments and empirical models constructed via the response surface methodology, with the sampling of the design space and empirical model terms dynamically adjusted throughout the optimization progression. The empirical models are constructed with statistically significant terms to maximize the utilization of information from each sample generated using the design of experiments. If the available information is fully utilized by the empirical model and the adaptive response surface optimization process needs to progress further until an optimal solution is identified, additional samples are generated. The methodology is applied to a benchmark bell crank problem, optimizing the bell crank for maximum operational value by simultaneously increasing fatigue life and reducing the overall component cost. This demonstration showcases the structural optimization software's capability to handle both design and manufacturing aspects seamlessly. The approach to solving the structural optimization problem involves constructing a constrained parametric bell crank part in Abaqus/CAE as it facilitates easy manipulation of the geometry. The entire process of geometry generation, meshing, simulation, and output extraction was supported by developing Python scripts. Response surface model building and other statistical analyses are conducted using the JMP statistical software. Nonlinear constrained optimization is executed through the sequential quadratic programming (SLSQP solver) from the SciPy library, allowing optimization on the response surfaces representing the objective function and constraints to identify the optimal solution. The optimal solution is obtained utilizing a small composite design with individual response surface models for the objective function and each constraint, is compared with results from the Abaqus finite element model, and the percentage difference was 0.9% at the optimal design variable values. / Master of Science / Optimization processes, in general, require multiple iterations to converge to the optimal solution. Structural optimization, dealing with large and complex computationally intensive models are typically very time-consuming. To address this challenge, approximations of the actual design space, called response surfaces, are created using the statistical concept known as response surface methodology. Response surfaces are developed by selecting specific regions within the design space and studying them using complex computational models. The results obtained from these computational models are combined with statistical tools to build a response surface that approximately represents the actual design objective function and the associated constraints of the design within the specified design space. In this research, an adaptive approach called adaptive response surface optimization is implemented. In this approach, the regions studied and the response surfaces are dynamically adjusted based on the progression of the optimization process. Such adaptability significantly accelerates the structural optimization process and yields successful results. To illustrate this method, a benchmark problem was solved using the finite element solver Abaqus, the statistical software JMP, and the optimization toolbox from the Scipy library.

The success of any racing car hinges on three key factors: its speed, handling, and reliability. In a highly competitive environment where lap times are extremely tight, even slight variations in components can significantly affect performance and, consequently, lap times. At the heart of a race car's performance lies the upright—a critical component of its suspension system. The upright serves to link the suspension arms to the wheels, effectively transmitting steering and braking forces to the suspension setup. Achieving optimal performance requires finding the right balance between lightweight design and ample stiffness, crucial for maintaining precise steering geometry and overall vehicle dynamics, especially under intense loads. Furthermore, there is a need to explore the system of structural optimization and seamlessly integrate Finite Element (FE) Models into the mathematical optimization process. This thesis explores a technique for parametric structural optimization utilizing finite element analysis and response surfaces to minimize the weight of the upright. Various constraints such as frequency, stress, displacement, and fatigue are taken into consideration during this optimization process. A parametric finite element model of the upright was designed, along with the mathematical formulation of the optimization problem as a nonlinear programming problem, based on the design objectives and suspension geometry. By conducting parameter sensitivity analysis, three design variables were chosen from a pool of five, and response surfaces were constructed to represent the constraints and objective function to be used to solve the optimization problem using Sequential Quadratic Programming (SQP). To streamline the process of parameter sensitivity analysis and response surface development, a Python scripting procedure was employed to automate the finite element job analysis and results extraction. The optimized upright design resulted in overall weight reduction of 25.3% from the maximum weight design of the parameterized upright. / Master of Science / The success of any racing car depends on three key factors: its speed, handling and reliability. In a highly competitive environment where lap times are extremely tight, even slight variations in components can significantly affect performance and consequently, lap times. At the heart of a race car's performance lies the upright—a critical component of its suspension system. The upright serves to link the suspension arms to the wheels, effectively transmitting steering and braking forces to the suspension setup. To achieve the best performance, upright must be as light as possible but it needs to be strong enough to ensure that the car is predictable when turning in a corner or while braking. Additionally, there is a need to explore methods of structural optimization and integrate finite element analysis seamlessly into the optimization process. Finite element analysis (FEA) is the use of part models, simulations, and calculations to predict and understand how an object might behave under certain physical conditions. This thesis examines a technique for optimizing the upright by designing it with numerous adjustable features for testing and then utilizing response surfaces to minimize its weight. Throughout this process, factors such as vibration, stress, deformation, and fatigue are carefully considered. A detailed parametric finite element model of the upright was developed, alongside the formulation of the optimization problem as a nonlinear programming problem, based on the objectives of the design and the geometry of the suspension. Through rigorous testing of parameters for optimization potential, design variables are selected for optimization. Response surfaces were then constructed to represent the constraints and objective function necessary to solve the optimization problem using Sequential Quadratic Programming (SQP). To enhance the efficiency of this process, a Python script was created to handle specific tasks within the finite element solver. This automation streamlined the analysis of the finite element model and the extraction of results. Ultimately, the optimized design of the upright yielded a 25.3% reduction in weight compared to its maximum weight configuration.

A numerical analysis of the loop tack test is presented to study the behavior of the strip and the influence of several factors, and the results are compared with experimental ones. The numerical results can be applied to model the performance of a pressure sensitive adhesive (PSA). Since the simulation of the loop tack test includes geometrical and material nonlinearities, it is solved numerically by the finite element method. The finite element program ABAQUS is used throughout the research. As the teardrop shaped loop is pushed down onto the adhesive and then pulled up, the variation of the loop behavior is investigated using two-dimensional (2D) and three-dimensional (3D) models. A bilinear elastic-plastic constitutive law is used for the strip. The deformation of the pressure sensitive adhesive is approximated as uniaxial extension of independent adhesive strands. A Winkler-type nonlinear elastic foundation and a viscoelastic foundation are used to model the PSA. A nonlinear elastic spring function is used, which is composed of a compression region for the bonding phase and a tension region for the debonding phase. A debonding failure criterion is assumed, in which an adhesive strand will debond when it reaches a certain length. During the bonding phase, it is assumed that the loop is perfectly bonded, and the contact time is not included. Curves of the pulling force versus the top displacement (i.e., tack curves) are obtained throughout the simulation. A parametric study is made with respect to the nonlinear spring function parameters, experimental uncertainties, and strip thickness. Anticlastic bending behavior is shown in the 3D analysis, and the contact patterns are presented. The effects of the elasticity modulus of the PSA for the elastic foundation and the displacement rate for the viscoelastic model are investigated. / Ph. D.

Linear and nonlinear finite element analyses are used for the investigation of rectangular anchorage zones with the presence of a support reaction. The investigation is conducted based on four load configurations consisting of concentric, inclined concentric, eccentric, and inclined eccentric loads. The method of model construction is illustrated thoroughly. The influence of several parameters, including anchorage ratio, inclination of prestressing load, eccentricity, magnitude of the reaction force, bearing plate ratio, and the location of the reaction force, is studied. Both graphical and numerical presentations of the results from each load configuration are given. Improved equations, which are modified from the equations presented in the AASHTO Standard Specifications (2002), are proposed. The results from the equations are compared to those from the finite element method. Nonlinear finite element analysis is used to verify the applicability of the equations and to study a new bursting steel arrangement. Linear and nonlinear finite element analyses are also used for the study of non-rectangular anchorage zones. Four basic load configurations, including concentric, eccentric, inclined concentric, and inclined eccentric loads, are investigated. The shell element is selected for the construction of the finite element models. Several parameters, consisting of anchorage ratio, inclination of prestressing load, eccentricity, web thickness, ratio of web thickness to flange thickness, and flange width, are chosen for parametric studies. The results from the studies are presented graphically and numerically. Equations to calculate the bursting force and location of the force are developed from the Strut-and-Tie Model approach. The verification of the formulations and the investigation of bursting steel arrangement are conducted using nonlinear finite element analysis. / Ph. D.

Abstract Biomechanics are especially important when it comes to the lower third of the face which is composed of a single load-bearing structure, the mandible. Implementation of recent developments in image processing, material sciences and computational technology allows the verification of these principles defining the appropriate practice. The studies listed in the thesis, benchmark from the simple to the more complicated mandibular surgical procedures. The aims were to build patient specific, custom made, composite reconstructions using newly learned techniques. Cross-sectional imaging with Cone Beam Computer Tomography was used to build bone models. The mandible at various ages, undergoing minor oral surgery, partial cross-section reduction with or without reinforcements and complete transection were simulated under biting conditions. Industry standard free form modelling, reverse engineering techniques and Finite Element Analysis were used. Internal and external validations of certain modelling elements were introduced. The mandible became stiffer with increasing age. Minimization of the reduction of the main load-bearing structures was noted to be crucial. The External Oblique Ridge was one such a structure. Partial thickness defects were best spanned by Dynamic Compression Plates. If the remaining amount of bone was insufficient or the bone quality was poor then Locking Compression Plates were preferred. Rounding or the use of a stop-hole was recommended to reduce the risk of fracture development especially without additional Prophylactic Internal Fixation. Fixation using a single reconstruction plate with three screws on either side in the four most common segmental defects was sufficient. Locking monocortical screw fixation was superior over non-locking systems. The suitability of CBCT in bone scanning was demonstrated, highlighting the positional dependent differences within the scanned volume. It should be noted that the relevance and validity of such simulations depends on the quality and the setup. In the future, biomechanically customized fixation can complement tissue engineering procedures and regenerative techniques by providing the precise physical dimensions and biomechanical requirements of the planned reconstructions. / Abstrakti Biomekaniikan ymmärtäminen on tärkeää kovakudoskirurgiassa. Periaatteet ovat erityisen tärkeitä, kun kyseessä on kasvojen alin kolmannes, joka muodostuu yhdestä kantavasta rakenteesta eli alaleuasta. Viime aikojen kehitys kuvankäsittelyssä, materiaalitieteessä ja tietokoneteknologiassa ovat mahdollistaneet näiden periaatteiden tarkistamisen käytännössä. Tämän opinnäytetyön osatöissä tutkittiin biomekaniikkaa erityyppisissä leikkauksissa. Tavoitteena on rakentaa tulevaisuudessa potilaille mittatilaustyönä erilaisista materiaaleista korjausosia käyttäen hyväksi uusinta tietoa ja tekniikkaa. Leikekuvantamista kuten Multi Detectoria ja viime aikoina kartiokeilatietokonetomografiaa (KKTT) käytettiin luumallien valmistamisessa. Eri-ikäisten alaleukoja, joihin tehtiin pieniä suukirurgisia toimenpiteitä, osaosteomioita vahvistuksen kanssa tai ilman vahvistusta ja täydellisiä alaleuan katkaisuja, simuloitiin kuormitusolosuhteissa. Teollisuudessa standardoitua vapaamuotoista mallinnusta ja käänteistä tekniikkaa sekä Finite Element Analysis-menetemää käytettiin. Mallinnuksessa käytettiin lisäksi sisäistä ja ulkoista validointia. Alaleuka koveni iän myötä. Leuan kestävyyden kannalta oli ratkaisevaa että tärkeisiin kantaviin rakenteisiin puututtiin mahdollisimman vähän. Oblique Ridge oli yksi tällainen rakenne. Osaosteotomioissa paras ratkaisu oli dynaaminen kompressiolevy. Jos jäljelle jäävän luun määrä tai laatu oli heikko niin sitten lukittuvat puristuskompressiolevyt toimivat parhaiten. Luun pyöristäminen tai pysäytysreiän käyttö oli suositeltavaa vähentämään murtumariskiä varsinkin ilman profylaktista kiskotusta. Neljän yleisimmän segmentaalisen defektin kiinnitys yhdellä levyllä ja kolmella ruuvilla levyn molemmin puolin oli riittävä. Lukittuva monokortikaalinen ruuvikiinnitys oli ylivoimainen verrattuna ei-lukittuvaan systeemiin. KKTT osoittautui parhaaksi menetelmäksi alaleuan kuvantamisessa. Kaikki havainnot voivat toimia yleisohjeena kun harjoitellaan edellä mainittuja toimenpiteitä. On huomattava, että tällaisen simulaation merkitys ja todenmukaisuus riippuu sen laadusta ja asennuksesta. Tulevaisuudessa biomekaanisesti tarkkojen mittausten perusteella suunniteltu luun kiinnitys voi palvella kudosteknologian avulla tehtäviä rekonstruktioita antamalla toimenpiteessä tarvittavat tarkat fysikaaliset mitat ja kuormitusarvot.

No description available.