Os ensaios não destrutivos visam avaliar um elemento sem gerar danos a ele com a técnica empregada. Um tipo de ensaio não destrutivo é o método da velocidade do pulso de ondas ultrassônicas. Este método é comumente utilizado para determinar propriedades elásticas de um dado material e verificar danos no interior dos elementos estudados. Outra aplicação do ultrassom é a medição do nível de tensão num material por meio da propagação das ondas ultrassônicas, tendo como base a teoria da acustoelasticidade. Entretanto, o uso do ultrassom para esta finalidade ainda é pouco difundido, principalmente na aplicação em estruturas de concreto. Este trabalho teve como objetivo estudar a possibilidade de medir tensões em estruturas de concreto com o uso do ultrassom. Para tanto, foram realizados ensaios de compressão uniaxial em prismas de concreto. Durante os ensaios, foram emitidas ondas ultrassônicas nos elementos para cada nível de tensão aplicada no material. A partir destes ensaios, foi feito um estudo do comportamento acustoelástico do concreto. Verificou-se que as velocidades das ondas ultrassônicas variaram em função da intensidade das tensões normais de compressão existentes nos corpos de prova. Com base na variação das velocidades, os coeficientes acustoelásticos do concreto de cada prisma foram determinados e relacionados com propriedades do concreto. Verificou-se a possibilidade de se estimar o nível mínimo de tensão em determinadas estruturas de concreto a partir do conhecimento de seus coeficientes acustoelásticos. Concluiu-se que é possível estimar tensões em estruturas de concreto utilizando o ultrassom. / Nondestructive tests aim to analyze an element generating no damages. The pulse velocity of ultrasonic waves method is a type of nondestructive test. This method is commonly used to determine elastic properties of materials and to verify damages inside studied elements. Another application for ultrasound is the measurement of stress level in a material by means of propagation of ultrasonic waves. This application is based on the theory of acoustoelasticity. However, the use of ultrasound is still unusual for this purpose, mainly in application in concrete structures. This work intended to study the possibility of measuring stresses in concrete structures with the use of ultrasound. Uniaxial compression tests were performed on concrete prisms. During tests, ultrasonic waves were propagated in elements for each level of applied stress in the material. Then, a study about acoustoelastic behavior of concrete was performed. It was verified that the velocities of ultrasonic waves changed according to the intensity of normal compressive stresses there were in the specimens. Based on the variation of velocities, the acoustoelastic coefficients of concrete were determined for each prism. The coefficients were related with properties of concrete. The possibility of estimating the minimum level of stress in certain structures of concrete from their acoustoelastic coefficients was verified. It was concluded it is possible to estimate stresses in concrete structures using ultrasound.

This research project has investigated the mechanical behaviour of artificial turf surface systems used for sports under a range of real player movements, and the contribution of component layers to the overall system response by developing advanced measurement systems and methods. Artificial turf surface systems are comprised of a number of different materials and commonly with several layers, all of which contribute to their composite behaviour. During sports movements a player loads the surface, resulting in deformation that can change the surface behaviour, which in turn modifies the player biomechanical response. Improving the understanding of surface response to actual player loading is important for developing enhanced products for improving play performance. Likewise, by improving knowledge of surface effects on players, the understanding of injury risk can be improved. However, there is currently no published research to measure and analyse the behaviour of artificial turf system during real player locomotion. This research was undertaken to address this current lack of knowledge within the interaction between player and sports surface regarding the effects of player loading on the mechanical behaviour of artificial turf systems. In addition to support player loading regime, mechanical behaviour of hockey and third generation artificial turf surface systems and their component shockpad layers (a rubber shreds bonded shockpad and a polyurethane foam shockpad) was examined through dynamic cyclic compressive loading using an advanced material testing machine in laboratory environment. Each layer and carpet-shockpad system was subjected to controlled loading designed with previous biomechanical data at various loading frequencies (0.9 Hz, 3.3 Hz and 10 Hz) and under two different contact areas (50 mm and 125 mm diameter) to simulate aspects of player walking, running and sprinting. All layers and surface systems tested showed nonlinear stress-strain behaviour with hysteresis. Increasing the contact area resulted in reduced surface vertical deflection and more linear response. Increasing the loading frequency led to stiffer response in the lower stress range (< 400 kPa) for all surface systems. The third generation artificial turf systems showed also an increase in stiffness at higher stress range ( > 600 kPa) and a decrease in maximum strain as the loading frequency increased. Hysteresis loops obtained at different loading frequencies indicated that the amount of energy lost at the same peak load of 1900 N in each surface system decreased with an increase in loading rate. Player loading regime was performed to quantify the load/stress and the resulting surface deformation/strain under subject loading. Measurement systems including motion capture system, force plate and high speed were developed to characterise the response behaviour in a novel way. The mechanical behaviour of artificial turf surface systems under three player movement patterns (heel-toe walking, forefoot running and forefoot single leg landing) was measured. Boot-surface contact area of each movement varied during the stance. The heel-toe walking results indicated that the maximum applied stress and surface strain occurred in very early stance (first 10%) when the boot-surface contact area was small. For forefoot running and landing, the peak surface strain occurred around mid-stance concurrent with the time of peak applied stress. The maximum strain measured under running was smaller than under landing. A thin-film pressure sensing mat was used in both mechanical and player loading regimes and proved to be a useful tool for evaluating the pressure distributions and contact areas at different interfaces of the surface system. The applied stress on surface was observed to greatly reduce with depth over increasing contact area through the surface systems. Although the average pressure was reduced, pressure distribution contour showed directly under the surface load area the pressure at depth was still relatively large and that outside of this area the pressure was much lower. A comparison of the mechanical behaviour of artificial turf systems in terms of compressive strain, modulus of elasticity, stress distribution and energy loss under mechanical and player loading was evaluated. Key loading parameters in different loading regimes and their influence on surface system response were determined. The structure and material intrinsic properties of shockpad were considered to further explain the observed surface system behaviour. Two mathematical models were used to fit through the experimental data and found to be able to describe the loading behaviour. A breakthrough in understanding of the effects of real player loading on the mechanical behaviour response of artificial turf systems, and the contribution of the components to the whole system response has been achieved through the development of advanced measurement techniques.

Thesis (Ph.D.) -- La Trobe University, 2004. / Research. "A thesis submitted in total fulfill ment of the requirements for the degree of Doctor of Philosophy [to the] School of Human Biosciences, Faculty of Health Sciences, La Trobe University, Victoria". Includes bibliographical references (p. 366-400). Also available via the World Wide Web.

Os ensaios não destrutivos visam avaliar um elemento sem gerar danos a ele com a técnica empregada. Um tipo de ensaio não destrutivo é o método da velocidade do pulso de ondas ultrassônicas. Este método é comumente utilizado para determinar propriedades elásticas de um dado material e verificar danos no interior dos elementos estudados. Outra aplicação do ultrassom é a medição do nível de tensão num material por meio da propagação das ondas ultrassônicas, tendo como base a teoria da acustoelasticidade. Entretanto, o uso do ultrassom para esta finalidade ainda é pouco difundido, principalmente na aplicação em estruturas de concreto. Este trabalho teve como objetivo estudar a possibilidade de medir tensões em estruturas de concreto com o uso do ultrassom. Para tanto, foram realizados ensaios de compressão uniaxial em prismas de concreto. Durante os ensaios, foram emitidas ondas ultrassônicas nos elementos para cada nível de tensão aplicada no material. A partir destes ensaios, foi feito um estudo do comportamento acustoelástico do concreto. Verificou-se que as velocidades das ondas ultrassônicas variaram em função da intensidade das tensões normais de compressão existentes nos corpos de prova. Com base na variação das velocidades, os coeficientes acustoelásticos do concreto de cada prisma foram determinados e relacionados com propriedades do concreto. Verificou-se a possibilidade de se estimar o nível mínimo de tensão em determinadas estruturas de concreto a partir do conhecimento de seus coeficientes acustoelásticos. Concluiu-se que é possível estimar tensões em estruturas de concreto utilizando o ultrassom. / Nondestructive tests aim to analyze an element generating no damages. The pulse velocity of ultrasonic waves method is a type of nondestructive test. This method is commonly used to determine elastic properties of materials and to verify damages inside studied elements. Another application for ultrasound is the measurement of stress level in a material by means of propagation of ultrasonic waves. This application is based on the theory of acoustoelasticity. However, the use of ultrasound is still unusual for this purpose, mainly in application in concrete structures. This work intended to study the possibility of measuring stresses in concrete structures with the use of ultrasound. Uniaxial compression tests were performed on concrete prisms. During tests, ultrasonic waves were propagated in elements for each level of applied stress in the material. Then, a study about acoustoelastic behavior of concrete was performed. It was verified that the velocities of ultrasonic waves changed according to the intensity of normal compressive stresses there were in the specimens. Based on the variation of velocities, the acoustoelastic coefficients of concrete were determined for each prism. The coefficients were related with properties of concrete. The possibility of estimating the minimum level of stress in certain structures of concrete from their acoustoelastic coefficients was verified. It was concluded it is possible to estimate stresses in concrete structures using ultrasound.

Background Demands placed on individuals in occupational and social settings, as well as imbalances in personal traits and resources, can lead to chronic stress. The Trier Inventory for Chronic Stress (TICS) measures chronic stress while incorporating domain-specific aspects, and has been found to be a highly reliable and valid research tool. The aims of the present study were to confirm the German version TICS factorial structure in an English translation of the instrument (TICS-E) and to report its psychometric properties. Methods A random route sample of healthy participants (N = 483) aged 18–30 years completed the TICS-E. The robust maximum likelihood estimation with a mean-adjusted chi-square test statistic was applied due to the sample’s significant deviation from the multivariate normal distribution. Goodness of fit, absolute model fit, and relative model fit were assessed by means of the root mean square error of approximation (RMSEA), the Comparative Fit Index (CFI) and the Tucker Lewis Index (TLI). Results Reliability estimates (Cronbach’s α and adjusted split-half reliability) ranged from .84 to .92. Item-scale correlations ranged from .50 to .85. Measures of fit showed values of .052 for RMSEA (Cl = 0.50–.054) and .067 for SRMR for absolute model fit, and values of .846 (TLI) and .855 (CFI) for relative model-fit. Factor loadings ranged from .55 to .91. Conclusion The psychometric properties and factor structure of the TICS-E are comparable to the German version of the TICS. The instrument therefore meets quality standards for an adequate measurement of chronic stress.