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Optimal Modeling of Knots in Wood

Description

A model has been developed to modify Euler-Bernoulli beam theory for wooden beams, using visible properties of wood knot-defects. Treating knots in a beam as a system of two ellipses

A model has been developed to modify Euler-Bernoulli beam theory for wooden beams, using visible properties of wood knot-defects. Treating knots in a beam as a system of two ellipses that change the local bending stiffness has been shown to improve the fit of a theoretical beam displacement function to edge-line deflection data extracted from digital imagery of experimentally loaded beams. In addition, an Ellipse Logistic Model (ELM) has been proposed, using L1-regularized logistic regression, to predict the impact of a knot on the displacement of a beam. By classifying a knot as severely positive or negative, vs. mildly positive or negative, ELM can classify knots that lead to large changes to beam deflection, while not over-emphasizing knots that may not be a problem. Using ELM with a regression-fit Young's Modulus on three-point bending of Douglass Fir, it is possible estimate the effects a knot will have on the shape of the resulting displacement curve.

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Date Created
  • 2015-05

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Improving damage detection and localization in complex composites

Description

The goal of this research is to couple a physics-based model with adaptive algorithms to develop a more accurate and robust technique for structural health monitoring (SHM) in composite structures.

The goal of this research is to couple a physics-based model with adaptive algorithms to develop a more accurate and robust technique for structural health monitoring (SHM) in composite structures. The purpose of SHM is to localize and detect damage in structures, which has broad applications to improvements in aerospace technology. This technique employs PZT transducers to actuate and collect guided Lamb wave signals. Matching pursuit decomposition (MPD) is used to decompose the signal into a cross-term free time-frequency relation. This decoupling of time and frequency facilitates the calculation of a signal's time-of-flight along a path between an actuator and sensor. Using the time-of-flights, comparisons can be made between similar composite structures to find damaged regions by examining differences in the time of flight for each path between PZTs, with respect to direction. Relatively large differences in time-of-flight indicate the presence of new or more significant damage, which can be verified using a physics-based approach. Wave propagation modeling is used to implement a physics based approach to this method, which is coupled with adaptive algorithms that take into account currently existing damage to a composite structure. Previous SHM techniques for composite structures rely on the assumption that the composite is initially free of all damage on both a macro and micro-scale, which is never the case due to the inherent introduction of material defects in its fabrication. This method provides a novel technique for investigating the presence and nature of damage in composite structures. Further investigation into the technique can be done by testing structures with different sizes of damage and investigating the effects of different operating temperatures on this SHM system.

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Date Created
  • 2015-05

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Mechanical Design for TolTEC Optics

Description

The following paper discusses the validation of the TolTEC optical design along with a progress report regarding the design of the optical mounting system. Solidworks and Zemax were used in

The following paper discusses the validation of the TolTEC optical design along with a progress report regarding the design of the optical mounting system. Solidworks and Zemax were used in conjunction to model the proposed optics designs. The final optical design was selected through extensive CAD modeling and testing within the Large Millimeter Telescope receiver room. The TolTEC optics can be divided into two arrays, one comprised of the warm mirrors and the second, cryogenically-operated cold mirrors. To ensure structural stability and optical performance, the mechanical design of these systems places a heavy emphasis on rigidity. This is done using a variety of design techniques that restrict motion along the necessary degrees of freedom and maximize moment of inertia while minimizing weight. Work will resume on this project in the Fall 2017 semester.

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Date Created
  • 2017-05

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E-bike Retrofitting Kit

Description

The goal of this honors thesis creative project was to design, manufacture and test a retrofitted E-bike kit that met certain stated design objections. To design a successful E-bike kit,

The goal of this honors thesis creative project was to design, manufacture and test a retrofitted E-bike kit that met certain stated design objections. To design a successful E-bike kit, the needs of the customer were researched and turned into measurable engineering requirements. For the biker, these requirements are speed, range, cost and simplicity. The approach is outlined similarly to the capstone program here at ASU. There is an introduction in sections 1 and 2 which gives the motivation and an overview of the project done. In section 3, the voice of the customer is discussed and converted into requirements. In sections 4, 5,6,7 and 8 the design process is described. Section 4 is the conceptual design where multiple concepts are narrowed down to one design. Section 5 is the preliminary design, where the design parts are specified and optimized to fit requirements. Section 6 is fabrication and assembly which gives details into how the product was manufactured and built. Sections 7 and 8 are the testing and validation sections where tests were carried out to verify that the requirements were met. Sections 9 and 10 were part of the conclusion in which recommendations and the project conclusions are depicted. In general, I produced a successful prototype. Each phase of the design came with its own issues and solutions but in the end a functioning bike was delivered. There were a few design options considered before selecting the final design. The rear-drive friction design was selected based on its price, simplicity and performance. The design was optimized in the preliminary design phase and items were purchased. The purchased items were either placed on the bike directly or had to be manufactured in some way. Once the assembly was completed, testing and validation took place to verify that the design met the requirements. Unfortunately, the prototype did not meet all the requirements. The E-bike had a maximum speed of 14.86 mph and a range of 12.75 miles which were below the performance requirements of 15 mph and 15 miles. The cost was $41.67 over the goal of $300 although the total costs remained under budget. At the end of the project, I delivered a functioning E-bike retrofitting kit on the day of the defense. While it did not meet the requirements fully, there was much room for improvement and optimization within the design.

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Date Created
  • 2017-05

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Study of Exhaust Throttling Effects on SI Engine Performance

Description

To determine the effects of exhaust heat recovery systems on small engines, an experiment was performed to measure the power losses of an engine with restricted exhaust flow. In cooperation

To determine the effects of exhaust heat recovery systems on small engines, an experiment was performed to measure the power losses of an engine with restricted exhaust flow. In cooperation with ASU's SAE Formula race team, a water brake dynamometer was refurbished and connected to the 2017 racecar engine. The engine was mounted with a diffuser disc exhaust to restrict flow, and a pressure sensor was installed in the O2 port to measure pressure under different restrictions. During testing, problems with the equipment prevented suitable from being generated. Using failure root cause analysis, the failure modes were identified and plans were made to resolve those issues. While no useful data was generated, the project successfully rebuilt a dynamometer for students to use for future engine research.

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Date Created
  • 2017-05

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Mechanics of Origami Inspired Structures

Description

This research project will test the structural properties of a 3D printed origami inspired structure and compare them with a standard honeycomb structure. The models have equal face areas, model

This research project will test the structural properties of a 3D printed origami inspired structure and compare them with a standard honeycomb structure. The models have equal face areas, model heights, and overall volume but wall thicknesses will be different. Stress-deformation curves were developed from static loading testing. The area under these curves was used to calculate the toughness of the structures. These curves were analyzed to see which structures take more load and which deform more before fracture. Furthermore, graphs of the Stress-Strain plots were produced. Using 3-D printed parts in tough resin printed with a Stereolithography (SLA) printer, the origami inspired structure withstood a larger load, produced a larger toughness and deformed more before failure than the equivalent honeycomb structure.

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Date Created
  • 2018-05

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Drop Foot Rehabilitation

Description

A significant issue in the medical field is a lack of affordable, rehabilitation practices for patients with drop foot. Drop foot is a condition where a person is unable to

A significant issue in the medical field is a lack of affordable, rehabilitation practices for patients with drop foot. Drop foot is a condition where a person is unable to lift the front part of the foot. People with this condition usually swing their legs in a wide arc to avoid dragging the toes, or lift their leg higher than normal. This can cause an abnormal walking gait and force them to expend more energy than usual for mobility. This condition is usually the result of a nerve injury, brain or spinal injuries, and muscle disorders. One of the most common causes of drop foot is stroke. While there are ways for stroke survivors to live with drop foot, they do not provide free range of motion. Drop foot braces keep the foot in a stationary position with the foot lifted. They do not allow plantarflexion movement of any sort to mimic foot push off. The purpose of this experiment is to allow stroke survivors with drop foot to adjust to a normal walking gait. This experiment is also meant to allow movement while minimizing metabolic cost for the subject.

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Date Created
  • 2020-05

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Quantifying Microstructural Effects on the Strain Localization During Fatigue

Description

The goal of this research is to compare the mechanical properties of CP-Ti and Ti-O and to understand the relationship between a material's microstructure and its response to fatigue. Titanium

The goal of this research is to compare the mechanical properties of CP-Ti and Ti-O and to understand the relationship between a material's microstructure and its response to fatigue. Titanium has been selected due to its desirable properties and applicability in several engineering fields. Both samples are polished and etched in order to visualize and characterize the microstructure and its features. The samples then undergo strain-controlled fatigue tests for several thousand cycles. Throughout testing, images of the samples are taken at zero and maximum load for DIC analysis. The DIC results can be used to study the local strains of the samples. The DIC analysis performed on the CP-Ti sample and presented in this study will be used to understand how the addition of oxygen in the Ti-O impacts fatigue response. The outcome of this research can be used to develop long-lasting, high strength materials.

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Date Created
  • 2016-05

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Evaluation of an Original Design for a Cost-Effective Wheel-Mounted Dynamometer for Road Vehicles

Description

This thesis evaluates the viability of an original design for a cost-effective wheel-mounted dynamometer for road vehicles. The goal is to show whether or not a device that generates torque

This thesis evaluates the viability of an original design for a cost-effective wheel-mounted dynamometer for road vehicles. The goal is to show whether or not a device that generates torque and horsepower curves by processing accelerometer data collected at the edge of a wheel can yield results that are comparable to results obtained using a conventional chassis dynamometer. Torque curves were generated via the experimental method under a variety of circumstances and also obtained professionally by a precision engine testing company. Metrics were created to measure the precision of the experimental device's ability to consistently generate torque curves and also to compare the similarity of these curves to the professionally obtained torque curves. The results revealed that although the test device does not quite provide the same level of precision as the professional chassis dynamometer, it does create torque curves that closely resemble the chassis dynamometer torque curves and exhibit a consistency between trials comparable to the professional results, even on rough road surfaces. The results suggest that the test device provides enough accuracy and precision to satisfy the needs of most consumers interested in measuring their vehicle's engine performance but probably lacks the level of accuracy and precision needed to appeal to professionals.

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Date Created
  • 2018-05

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In situ SEM Testing for Fatigue Crack Growth: Mechanical Investigation of Titanium

Description

Widespread knowledge of fracture mechanics is mostly based on previous models that generalize crack growth in materials over several loading cycles. The objective of this project is to characterize crack

Widespread knowledge of fracture mechanics is mostly based on previous models that generalize crack growth in materials over several loading cycles. The objective of this project is to characterize crack growth that occurs in titanium alloys, specifically Grade 5 Ti-6Al-4V, at the sub-cycle scale, or within a single loading cycle. Using scanning electron microscopy (SEM), imaging analysis is performed to observe crack behavior at ten loading steps throughout the loading and unloading paths. Analysis involves measuring the incremental crack growth and crack tip opening displacement (CTOD) of specimens at loading ratios of 0.1, 0.3, and 0.5. This report defines the relationship between crack growth and the stress intensity factor, K, of the specimens, as well as the relationship between the R-ratio and stress opening level. The crack closure phenomena and effect of microcracks are discussed as they influence the crack growth behavior. This method has previously been used to characterize crack growth in Al 7075-T6. The results for Ti-6Al-4V are compared to these previous findings in order to strengthen conclusions about crack growth behavior.

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Date Created
  • 2018-05