Rotator cuff (RC) muscle insertion was previously thought to consist of singular, individual tendons inserting onto predefined areas on the greater and lesser tuberosities. However, more recent publications describe the RC muscle tendons as forming a singular insertion across the tuberosities, consisting of both tendinous and capsular portions. Orthopaedic surgeons are now considering these two layers in their surgical approach and treatment plans; therefore this study aimed to test and compare the elastic modulus and maximum load to failure for both tendinous and capsular layers taken from supraspinatus (SS), infraspinatus (IS) and subscapularis (SC). Fourteen (n = 14) fresh/frozen arms were used in this study. Each RC muscle was reverse dissected and trimmed to a 2 x 2cm strip, which was separated into its two layers, still attached to the humerus. An Instron 1342 with a 1kN load cell was used to place the samples under tensile testing till failure (Newtons/N). Accompanying Integrated Design Tools (IDT) NX8-S2 cameras captured images for full-field strain measurements with the Image Systems TEMA software package through digital image correlation (DIC). SS, IS, and SC tendinous layers yielded higher average elastic moduli readings (72.34 MPa, 67.04 MPa, and 59.61 MPa respectively) compared to their capsular components (27.38 MPa, 32.45 MPa, and 41.49 MPa respectively). Likewise, the tendinous layers for SS, IS and SC all showed higher average loads to failure (252.74 N, 356.27 N and 385.94 N, respectively) when compared to the capsular layers (211.21 N, 168.54 N and 281.74 N, respectively). These biomechanical differences need to be taken into account during surgical repair owing to the fact that, should these layers be repaired as one singular structure, it may place the weaker less elastic, capsular layer under more strain, possibly leading to either re-tear complications or reduced postoperative healing and functionality. Thus, based on the results, it is recommended that surgeons consider and repair each layer independently for better postoperative biomechanical integrity. / Dissertation (MSc)--University of Pretoria, 2019. / Anatomy / MSc / Unrestricted

This paper presents results on experimental research for concrete produced using recycled coarse aggregates (RCA). Five types of coarse aggregates were used in this study, four of which were RCA. The main purpose of this research was to examine how different types and properties of coarse aggregate affected compressive strength, modulus of elasticity, and shrinkage in concrete when natural coarse aggregates were replaced with RCA. Concrete batches were made with water-cement (w/c) ratios of 0.30, 0.45, and 0.60, and substitution percentages ranged from 0% to 100% of natural aggregate with RCA. Test results clearly show that compressive strength, modulus of elasticity, and shrinkage greatly depend on the quality and type of coarse aggregate used. In addition to testing of hardened concrete, predictive models for elasticity and ultimate shrinkage were developed to formulate and reinforce proposed conclusions about the properties and performance for the different RCA.

Over the last 50 years significant advancements have been made in the southern yellow pine (SYP) forests in the U.S. south. Due to silvicultural changes and large scale reforestation efforts the US south has seen significant increases in standing volume (more than 120% over the period). Landowners that grow SYP plantations largely manage for trees that are harvested to produce dimensional lumber. With the changes in growth patterns it is of interest if there have been any changes in structural properties of the lumber that is produced from timber grown today. Landowners desire confirmation that what they are doing in terms of management is maintaining the quality and strength of lumber that the market demands. This information is critical because timberland owners’ plant and manage trees that will ultimately be brought to market at lumber 25-40 years into the future. In an effort to provide clarity to this topic this dissertation investigates: 1) The extent to which the specific gravity (SG), bending strength (modulus of rupture, MOR), and bending stiffness (modulus of elasticity, MOE) of small clear specimens of SYP have changed, particularly with respect to reduction(s), during the interval from approximately 1965 to 2015. 2) The extent to which the compression parallel to grain and perpendicular to grain strength of small clear specimens of SYP have changed, particularly with respect to reduction(s), during the interval from approximately 1965 to 2015. Use statistical analysis of variance to investigate potential differences among data from a historical 1966 data set, a 2014 in-grade data set, and a 2018 staircase material data set. 3) The nature of the relationship between and among SG, MOE, and MOR of small clear specimens of SYP and how these relationships may have changed, during the interval from approximately 1965 to 2015. Use statistical regression analysis to explore changes to the interrelationships of SG, MOE, and MOR among the three samples, with particular interest toward how these may impact or influence non-destructive evaluation. This work consists of 3 independent chapters using varying appropriate statistical methods and is accompanied by an introduction and conclusion.

This investigation focuses on the production, strength properties, and marketability of a new ultra stiff wood composite. The basis of the examination is to compare strength properties such as, Modulus of Rupture, Modulus of Elasticity, Work to Max Load, and Density with currently available products. The final analysis of the ultra stiff product suggested that this product would compete favorably in today’s market due to the strength properties of the product. Although the current hot-pressing method is not economical for mass production, other ways of pressing can be utilized. It is noted in this research that the wood moisture content can influence MOE, MOR, and density properties. By manipulating and controlling the press cycle and the moisture content, a competitive product was produced.

Currently, NCHRP Report 356 has published an equation to estimate the ultimate strength of the local zone in normal weight concrete. The local zone is the area of concrete directly ahead of the bearing plate. The equation can be broken into two distinct parts: unconfined bearing strength of concrete enhanced by the A/A_b ratio and the enhancement of strength due to the presence of confining. Research has shown that the strength enhancement of the A/Ab ratio and confining reinforcing is less in lightweight concrete than in normal weight concrete. To determine the strength of the local zone in lightweight concrete 30 reinforced prisms, 2 unreinforced prisms, and concrete cylinders were tested. The dimensions of the prisms were 8 in. x 8 in. x 16 in. and the cylinders were 4 in. x 8 in. cylinders. The simulated reinforcing in the prisms extended only through the top 8 in. of the prism and consisted of either ties or spirals with different spacing or pitch, respectively. To determine the effect of the A/A_b ratio for each spacing or pitch arrangement of the reinforcing, one of two different size bearing plates were used. From the testing performed in this research and other research, it is apparent that the NCHRP equation is unconservative when estimating the ultimate strength of the local zone in lightweight concrete. By modifying both parts of the NCHRP equation it is possible to conservatively predict the ultimate strength of the local zone in lightweight concrete. Also investigated in this thesis are equations to predict the splitting cylinder strength and modulus of elasticity of lightweight concrete. For a sand-lightweight concrete, as defined by ACI 318-05 Building code and Commentary, the splitting tensile strength can be accurately predicted by multiplying the square root of the compressive strength by 5.7. / Master of Science

The Ph.D. thesis deals with one of the most important characteristics of hardened concrete; i.e. the modulus of elasticity. The thesis aims to describe and evaluate the important factors that affect the final value of concrete modulus of elasticity, especially those that can be influenced during construction. Another aim is to find ways to determine the static modulus of elasticity of concrete by non-destructive means (primarily ultrasonic pulse method, resonance method and use of electronic rebound hammers), thus to determine the possibility of creating calibration curve for NDT determination of the modulus of elasticity.

The amount and morphology of the graphite phase largely controls the resulting properties of cast iron. For instance, in flake graphite cast irons the mechanical properties are low while the thermal conductivity is high. This is in contrast with spheroidal graphite cast irons where the mechanical properties are high and the thermal conductivity is low. These differences are due to the different graphite morphologies and must be accounted for in the design work and material selection of cast iron components. In this work the influence of the graphite phase on the elastic and plastic deformation behaviour of cast irons has been studied. The material grades studied originate from castings for marine diesel engine piston rings with different chemical analyses. Two groups of pearlitic cast iron materials were studied; one with differences in graphite morphology and one with grey irons that differed in graphite content. For these different material grades the mechanical properties were correlated to microstructural parameters. In addition to standard uniaxial tensile tests, acoustic emission measurements were used for the study of deformation. When studying the modulus of elasticity of the cast iron it was found that the modulus of elasticity of the inherent graphite phase depends on the roundness of the graphite particles and is due to the strong anisotropy of the graphite phase. A linear correlation between nodularity and the modulus of elasticity of the graphite phase was derived. This correlation made it possible to account for the anisotropy of the graphite phase in the model used. By applying the linear function when modelling the effective modulus of elasticity, a high accuracy between experimental and theoretical values was achieved. Another factor affecting the elastic response when subjecting a cast iron component to tensile load was found to be the plastic deformation that actually occurs at very low strains for all of the studied cast iron grades. It was observed that the plastic deformation in the low strain elastic region, quantified by using acoustic emission measurements, increased linearly with decreasing modulus of elasticity. These measurements showed that the amount of plastic deformation in the elastic region was largely controlled by the graphite morphology. It was concluded that as the roundness of the graphite particles increases, the plastic deformation activity in the elastic region decreases. The plastic deformation activity continued linearly into the pronounced plastic region of the tensile tests. A decrease in roundness or increase in graphite fraction resulted in an increase of the amount of plastic deformation and the strain hardening exponent. A dependence between strength coefficient and graphite fraction was observed. Models for the flow curves for pearlitic cast irons were developed and shown to accurately reproduce the observed experimental curves. The surveys performed and conclusions from this thesis will be helpful in the design of new cast iron materials.

When using timber for construction purposes it is important to know its strength. One way to do this is by sorting the boards into strength classes that are defined by European standards.  A commonly used method for strength grading is based on dynamic excitation in the longitudinal direction of the board to obtain an average dynamic longitudinal modulus of elasticity (MOE). This in turn correlates with the bending strength of the board in such a way that it can be used as an indicating property (IP) to bending strength. The use of MOE as an IP has proven to give the highest coefficient of determination (R2) to both bending and tensile strength in boards. Through the research described in this thesis, one might find that both reducing the length of a board to half its initial length and by removing the part containing the lowest local MOE in edgewise bending provided similar results, the axial dynamic MOE remaining within a 1% tolerance whereas the lowest IP based on local MOE in edgewise bending increased by 6–7%.

O objetivo do presente estudo foi avaliar o desenvolvimento das tensões de polimerização de um compósito resinoso restaurador ao longo das primeiras 24 horas após a fotoativação, segundo dois métodos de análise da propagação de trincas. A influência do armazenamento em água sobre a magnitude das tensões também foi avaliada. O grau de conversão (GC) e o módulo de elasticidade (E) do compósito foram determinados nos diferentes tempos de observação. As hipóteses nulas do trabalho foram: 1) tensão de polimerização, GC e E não variam de forma significativa ao longo do período de observação; 2) os dois métodos de análise de propagação de trincas fornecem resultados semelhantes; 3) os valores de tensão não são influenciados pelo meio de armazenamento. Foram confeccionados discos de vidro de soda-cal com 2 mm de espessura, diâmetro externo de 12 mm, com perfuração central de 4 mm de diâmetro. Os discos foram aleatorizados em três grupos. Em um deles, os discos foram restaurados (Charisma Diamond, Heraeus Kulzer) e, após os tempos de 10 min, 1, 2, 4, 8 ou 24 horas (n=10), os espécimes receberam quatro indentações Vickers, (9,8N por 20s) a 500m da margem da cavidade. O segundo grupo passou pelo mesmo processo, porém os discos ficaram armazenados em água antes de serem indentados. Em seguida, o comprimento das trincas e a diagonal da indentação foram mensurados em microscópio óptico. A tensão residual no vidro foi calculada de acordo com a norma 4-01 (The Society of Materials Science, JSMS, Japão). No terceiro grupo, os discos foram indentados e armazenados em dissecador por 24h antes de serem restaurados. As trincas foram medidas antes e após a restauração, nos mesmos tempos descritos acima, e a tensão calculada de acordo com a fórmula descrita por Yamamoto et al. (Dent Mater, 2009). O GC foi determinado por espectroscopia no infra-vermelho próximo (n=3). O E foi obtido através do teste de dobramento em três pontos (n=10). Os dados foram submetidos a ANOVA/Tukey (=0,05) e análise de regressão. A tensão de polimerização, assim como o GC e o E tiveram seus valores aumentados ao longo do tempo. O GC aumentou 28% entre 10 minutos e 24 horas, para o E houve um aumento de 1,7 GPa para 6,3 GPa entre 10 minutos e 24 horas. A tensão de polimerização aumentou 40% entre 10min e 24h para a norma 4-01 e 51% para o método do Yamamoto et al. O meio de armazenamento foi estatisticamente significativo até o tempo de 4 horas. Portanto, a primeira hipótese foi rejeitada. A segunda e a terceira hipótese podem ser apenas parcialmente rejeitadas. / The objective of this study was to evaluate composite resin restoration polymerization stress development over the first 24 hours after polymerization, according to two methods of analysis of crack propagation. The influence of water storage on the magnitude of the stresses was also evaluated. The degree of conversion (DC) and modulus of elasticity (E) of the composite were determined at various time points. The null hypotheses of this study were: 1) The polymerization stress, DC and E do not change significant throughout the observation period, 2) the two methods of analysis of crack propagation provide similar results, 3) the stress values are not influenced by storage medium. Disks were made of soda-lime glass with 2 mm thickness, 12 mm in outside diameter with central bore of 4 mm in diameter. The perforations were treated with hydrofluoric acid and silane. The discs were randomized into three groups. In one of them, the discs were restored (Charisma Diamond, Heraeus Kulzer), and, the times after 10 min, 1, 2, 4, 8 or 24 hours (n = 10), the specimens received four Vickers indentations (9.8 N for 20 s) at 500m cavity margin. The second group went through the same process, but the discs were stored in water prior to being indented. Then, the length diagonal of the indentation and crack was measured in an optical microscope. The residual stress in the glass was calculated according to standard 4-01 (The Society of Materials Science, JSMS, Japan). The third group of discs were treated similarly, indented and stored in a desiccator for 24 hours before being restored. The cracks were measured before and after the restoration following the same time, and the stress calculated according to the formula described by Yamamoto et al. (Dent Mater, 2009). The DC was determined by near-infrared spectroscopy (n = 3). The E was obtained through the bend test conducted at three-points. Data were subjected by ANOVA / Tukey test ( = 0.05) and regression analysis. The polymerization stress, as well as DC and E values were increased over time. GC increased 28% between 10 minutes and 24 hours, and for an increase of 1.7 GPa to 6.3 GPa between 10 minutes and 24 hours. The polymerization stress increased 40% between 10 min and 24 hours to the standard 4.1 and 51% for the method of Yamamoto et al. The storage medium was statistically significant at the time of 4 hours. Thus, the first hypothesis was rejected. The second and third hypothesis may only be partially rejected.

Esta Dissertação de Mestrado tem como Objetivo estudar a influência da tangente delta, envelhecimento termomecânico e força no comportamento de uma borracha de polibutadieno baixo cis perante o desgaste abrasivo através de experimentos em roda de borracha, utilizando planejamento fatorial completo em dois níveis (DOE 2k). A literatura possui muitas informações em relação à força indicando uma relação exponencial com a taxa de desgaste, todavia em relação à tangente delta e ao envelhecimento termomecânico quase não há dados. Ao final do trabalho foi possível verificar que todos os fatores estudados são significativos com relação ao desgaste da borracha, sendo a força a variável com maior influência, seguida pelo envelhecimento. A histerese medida pela tangente delta, apesar de ser um fator importante, só exerce influência no desgaste quando a borracha se encontra no estado envelhecido. Além disto, este trabalho também apresenta informações complementares sobre propriedades que são características da borracha e pouco difundidos, como o smearing, características de ondas de abrasão (abrasion pattern), comprimento de onda (Schallamach wavelength) e ondas de destacamento (waves of detachment). / This goal of this Master thesis is the study the influence of loss factor, thermomechanical aging and applied load to the abrasion behavior of low cis polibutadiene rubber through rubber wheel testing machine experiments using 2k factorial experiment design in two levels (DOE 2k). The literature has many information involving action of force showing exponential relationship between wear rate with applied load, almost no data related to the influence of loss factor and the thermomechanical aging. It was observed that all the studied factors are significant to the wear of rubber, the force being the variable with the greatest influence, followed by aging. The loss factor, despite being an important factor, only influences the wear behavior of aged rubber. In addition, this work presents some information regarding to the typical properties only for rubber and rubber products, such as smearing, abrasion pattern and Schallamach wavelength.