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The Florida Technological University four-component strain-gage balance is an internally mounted, half-inch diameter balance capable of measuring four components of load: front and rear normal force, axial force, and rolling moment. Measurement of these components is accomplished by means of sixteen strain gages that are mounted on the balance and wired into four full bridge circuits. When the balance is subjected to a load, the strain gages, through a small resistance change, indicated the strain a balance element is undergoing. This report presents a description of the balance and its support equipment, and outlines specific calibration procedures necessary to their successful implementation. These calibration procedures take two forms: that of calibrating the readout equipment, and that of calibrating the balance itself. Also contained in this report is a method of reducing calibration data into a set of parameters applicable to the balance. To aid in the calibration of the balance, a calibration assembly was designed and built. Two calibration models were designed to facilitate the incremental loading of the balance and the interpretation of the readout data.

<p><strong>In this study, detailed numerical analysis is carried out to investigate the effects of strain hardening on necking improvement by using finite element package ABAQUS. In addition, the response of laminated composite in necking, pure bending and hydroforming is also examined. It is concluded that architectured structure, especially corrugated reinforcement is an efficient method to significantly improve necking strain.</strong></p> <p><strong>The necking strain is proportional to the strain hardening rate and volume fraction of the cladding material for laminated composite. In pure bending process, the residual stress distribution varies according to different material composition. The extent of springback is linearly related to the bending moment.</strong></p> <p><strong>After the unloading in hydroforming process, the volume change of the specimen is linearly related to the fluid pressure while the slope of the linear function is independent to the material composition.</strong></p> <p><strong>Under 2D plane strain tension, corrugated reinforcement is able to provide high strain hardening rate at large strain, and hence significantly improve necking strain of the composite. Small scale corrugation is superior to large scale ones in both necking strain and strength improvement. An optimal scale exists for highest necking strain and strength while further decrease of scale deteriorates the tensile response.</strong></p> <p><strong>The anisotropic improvement of necking strain by 2D corrugation can be extended to other directions by 3D cone reinforcement. Under plane strain condition, the cone reinforcement is superior to the flat reinforcement in necking strain while remaining comparable strength.</strong> <h1></h1></p> / Master of Applied Science (MASc)

<p>Superluminescent diodes have become important for various applications, such as for biomedical imagining, due to their broad spectral width and high power.</p><p>This thesis demonstrates two-section superluminescent diodes fabricated using quantum well intermixing with strained Ga_0.75sln_0.25As quantum wells, grown on a GaAs substrate. A 100 nm capping layer of Ga_0.515In_0.485P grown at low temperature and having an excess of phosphorus, was removed from one section of the device to produce a relative bandgap shift between sections after rapid thermal annealing. The devices emitted at a wavelength of ~1μm with 60 nm of spectral width, and up to 38 mW of power at 20°C, depending on the currents applied to each section.</p><p>The combination of the spectral output from the two quantum well intermixed sections resulted in the broad spectral width. Angled facets at 7 ° were used to prevent the device from lasing. Additional power improvements were seen following the thermal anneal when a SiO2 capping layer was used on both sections. Depending on the applied currents, each section required 1.5 V to 3.0 V; and failed at 5.3 V ± 0.5 V.</p> / Thesis / Master of Applied Science (MASc)

<P> A study of the reliability of semiconductor distributed feedback diode lasers is presented using the degree of polarisation of photoluminescence (DOP). Two figures of merit, v and w, are developed and used to characterise device aging times and performance. v measures the strain gradient between the top and middle of a device by calculating the difference in an area-averaged DOP between the middle and top of a fixed area of the device. w measures the average strain profile across the top of the device by taking the difference in an area-averaged DOP between the region immediately beneath the ridge and the regions to the immediate right and left of it. Further, the influence of aging and the nature of metal contact are explored as they relate to these metrics. </p> <P> Finite element fits to the DOP and rotated degree of polarisation of photoluminescence (ROP) are presented. The models thus generated are used to explain the nature of the strain observed in different devices. </p> / Thesis / Master of Applied Science (MASc)

This thesis describes an investigation into the experimental accuracy of a close-up stereo vision system. Surfaces are measured from any orientation through the synergy of a Coordinate Measurement Machine (CMM) and a custom made stereo vision head. Calibration of the stereo cameras is achieved using bundle adjustment non-linear optimization, commonly used in photogrammetry. Point set registration techniques are used to calibrate the stereo head with respect to the CMM coordinate system. The fully calibrated stereo vision system is used to provide experimental accuracy results under ideal imagining conditions. The system is then applied to the practical problem of sheet metal strain analysis. This problem involves many non-ideal imaging components that affect system accuracy. Experimental results for this non-deal situation are provided in the form of three-dimensional strain distribution plots. / Thesis / Master of Engineering (ME)

In this thesis the nature and strengthening effect of the various precipitates in Al-4% Cu are reviewed, followed by a literature survey on the response of this alloy to fatigue. The first experiments described were carried out to measure the Bauschinger effect and the results of these are presented. The experimental study was further extended by cyclic straining corresponding to fatigue conditions and the results obtained are presented graphically and through electron micrographs. The fatigue behaviour was further investigated at liquid air temperature. Also, the effect of heat treatments carried out during the interruption of fatigue on a specimen containing metastable θ" precipitates is reported. All the experiments were carried out on single crystals and most of them with 112 orientation as indicated later. / Thesis / Master of Science (MS)

Since strain changes the interatomic spacing of matter and alters electron and phonon dispersion, an applied strain ϵ can modify the thermal conductivity κ of a material. This thesis shows how the strain induced by heteroepitaxy is a passive mechanism to change κ in a thin film and how the film thickness is key to the functional form of κ(ϵ). Molecular Dynamics simulations of the physical vapor deposition and epitaxial growth of ZnTe thin films provide insights into the role of interfacial strain on the thermal conductivity of a deposited film. ZnTe films grown on a lattice mismatched CdTe substrate exhibit ~6% in-plane biaxial tension and ~7% out-of-plane uniaxial compression. In the T=700 K to 1100 K temperature range, the conductivities of strained ZnTe layers that are 5 unit cells thick decrease by ~ 35%, a result that is relevant to thermoelectric devices since strain can also enhance charge mobility and increase their overall efficiency. The resulting understanding of dκ/dT shows that strain engineering can also be used to create a thermal rectifier in a material that is partly strained and partly relaxed, like at the junction of an axial nanowire heterostructure. To better isolate the role of strain, the study is extended to free-standing ZnTe films with thicknesses between 116 Å to 1149 Å under the application of both uniform and biaxial strain between -3% to 3% at 300 K. Since the boundaries of the film are diffuse, κ becomes size dependent when the film thickness approaches the order of the mean free path of the phonons. As this thickness is decreased, the magnitude of κ decreases until boundary scattering dominates so that κ(ϵ) depends on v_g (ϵ). This conclusion is important as it can be generalized to other materials and potential functions; it suggests that if a film is thin enough for boundary scattering to dominate, then the behavior of κ(ϵ) can be predicted based on the bulk dispersion curve alone, which should greatly simplify strain-based device design. / Thesis / Doctor of Philosophy (PhD) / Since strain changes the interatomic spacing of matter and alters electron and phonon dispersion, an applied strain ϵ can modify the thermal conductivity κ of a material. This thesis shows how the strain induced by heteroepitaxy is a passive mechanism to change κ in a thin film and how the film thickness is key to the functional form of κ(ϵ). Molecular Dynamics simulations of the physical vapor deposition and epitaxial growth of ZnTe thin films provide insights into the role of interfacial strain on the thermal conductivity of a deposited film. The result is relevant to thermoelectric devices since strain can also enhance charge mobility and increase their overall efficiency. The resulting understanding of dκ/dT shows that strain engineering can also be used to create a thermal rectifier in a material that is partly strained and partly relaxed, like at the junction of an axial nanowire heterostructure.

Rib and costal cartilage fractures are the most common injuries resulting from blunt thoracic loading scenarios, including motor vehicle collisions. The costal cartilage is a cylindrical hyaline cartilage composed of two layers: a core interstitial matrix enveloped by the perichondrium. The perichondrium itself has an inner chondrogenic layer and an outer fibrous layer. The objective of this study was to evaluate the tensile material properties of human costal cartilage perichondrium at two loading rates for a range of subject demographics. Fifty-six (n=56) samples containing the fibrous layer and chondrogenic layer (i.e., two-layered samples) were fabricated from thirty-three (n=33) donors aged from 11 to 69 years of age (19 M, 14 F). Thirteen (n=13) samples without the fibrous layer (i.e., one-layered samples) were fabricated from eight (n=8) donors aged from 11 to 54 years of age (5 M, 3 F). The perichondrium was isolated from the interstitial matrix for all samples and the fibrous layer was removed for one-layered samples to assess the effect of the absence of the fibrous layer. The tissue was then stamped into a dog bone-shaped coupon and sanded down to a uniform thickness of ~1.3 mm for two-layered samples and ~1 mm for one-layered samples. The gage length of the completed coupons was marked with a black ink dot pattern to facilitate strain calculations via video tracking. The coupons were loaded axially in tension to failure at either a slow (0.005 s⁻¹) or fast (0.5 s⁻¹) target loading rate using a material testing system. The elastic modulus, ultimate stress, ultimate strain, failure stress, failure strain, and strain energy density (SED) were then calculated for each test. Material property data were compared by sample type and loading rate. Since there was no significant influence of sex on any material properties, the data were grouped together for the analysis. Modulus, ultimate stress, failure stress, and SED were found to significantly decrease with donor age at both loading rates and ultimate and failure strain also significantly decreased with donor age at the 0.5 s⁻¹ target loading rate. Failure stress in the two-layered samples was found to be greater than that of the one-layered samples at both loading rates. One-layered samples had a greater failure strain than two-layered samples at both loading rates. Perichondrium data were compared to interstitial matrix data from a previous study to further investigate the role of cartilage layer on material properties. The modulus, ultimate stress, and failure stress of costal cartilage decreased moving radially inward (greatest in two-layered perichondrium samples, least in interstitial matrix samples). The opposite was true for ultimate and failure strain, with the greatest failure strain values occurring in the interstitial matrix and the least in the two-layered perichondrium samples. The sample size of one-layered samples was too small to draw any substantial conclusions regarding age trends. This was the first study to analyze the material property trends in costal cartilage perichondrium. The results of this study can be incorporated into virtual human body models to improve the accuracy of thoracic injury prediction in the context of motor vehicle safety. / Master of Science / Motor vehicle collisions are the second leading cause of death due to unintentional injury in the United States, with rib and costal cartilage fractures being the most commonly observed injuries. The cylindrical costal cartilage connects the front of the ribs to the sternum and is composed of two layers: a core interstitial matrix enveloped by the perichondrium. The perichondrium itself has an inner chondrogenic layer and an outer fibrous layer. Virtual human body models incorporate material property data to improve their ability to predict injury risk and are frequently used among vehicle manufacturers to evaluate safety during vehicle development. Currently, models have to make simplifications and assumptions regarding the perichondrium properties, since there are no material property studies on the isolated perichondrium to date. Therefore, the purpose of this study was to quantify the tensile material properties of human costal cartilage perichondrium at two loading rates for a range of subject demographics. Dog-bone shaped coupons with either both perichondrium layers (i.e., two-layered samples) or just the chondrogenic layer (i.e., one-layered samples) were loaded to failure under tension at either a slow (0.005 s⁻¹) or fast (0.5 s⁻¹) target loading rate using a material testing system. Data were obtained for fifty-six (n=56) two-layered samples from thirty-three (n=33) donors aged from 11 to 69 years old. Data were collected for thirteen (n=13) one-layered samples from eight (n=8) donors aged from 11 to 54 years old. The elastic modulus, ultimate stress, ultimate strain, failure stress, failure strain, and strain energy density (SED) were quantified for each test. Material properties of two-layered samples decreased with increasing donor age. No trends were found with regard to donor sex. Only ultimate and failure stress of two-layered samples were significantly affected by loading rate. Perichondrium material property data were compared to interstitial matrix data from a previous study to investigate the effect of cartilage layer on costal cartilage material properties. Elastic modulus, ultimate stress, and failure stress decreased when moving inward in cartilage layers, while ultimate and failure strain increased. Overall, this is the first study to evaluate the material properties of the perichondrium and the change in material properties with cartilage layer. These data can be used to improve the accuracy of human tolerance to thoracic injury in human body models.

Yes / This is a study of the modelling and prediction of strain recovery in a polylactide. Strain recovery near the glass transition temperature is the underlying mechanism for the shape memory in an amorphous polymer. The investigation is aimed at modelling such shape memory behaviour. A PLA-based copolymer is subjected to stress-strain, stress relaxation and strain recovery experiments at large strain at 60 °C just below its glass transition temperature. The material is 13% crystalline. Using published data on the mechanical properties of the crystals, finite element modelling was used to determine the effect of the crystal phase on the overall mechanical behaviour of the material, which was found to be significant. The finite element models were also used to relate the stress-strain results to the yield stress of the amorphous phase. This yield stress was found to possess strain rate dependence consistent with an Eyring process. Stress relaxation experiments were also interpreted in terms of the Eyring process, and a two-process Eyring-based model was defined that was capable of modelling strain recovery behaviour. This was essentially a model of the amorphous phase. It was shown to be capable of useful predictions of strain recovery. / Engineering and Physical Sciences Research Council, grant number EP/L020572/1. / . Not submitted within 3 months from acceptance or publication but is a Gold paper.