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Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 75-76). Also available via the Internet.

Thesis (Ph. D.)--University of Wisconsin, 1981. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 119-127).

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objective of this research was to evaluate the effect of private supplementation with concentrated or legume, on the pasture characteristics, performance, carcass traits, body components, physico-chemical and sensory characteristics of the meat from suckling lambs kept on ryegrass pasture. Twenty seven suckling lambs were used with about 17 days of age and weighing 9,91 ± 0,594kg, which are distributed in the treatments that corresponded to feeding systems: suckling lambs kept on ryegrass pasture, suckling lambs kept on ryegrass pasture and supplemented with concentrated in private feeder (creep feeding) and suckling lambs kept on ryegrass pasture and supplemented with legume in the private pasture (creep grazing). The concentrate supplement was composed by corn, soybean meal and limestone, and was supplied ad libitum. The supplementary pasture was composed by legume white clover. It was evaluated the characteristics of ryegrass pasture and performance of lambs, which were slaughtered when reached 32 kg of body weight. Subsequently, evaluated the carcass characteristics, body components and characteristics of meat. The experimental design was completely randomized, where the results were submitted to analysis of variance and means compared by Tukey test at 5% of significance level. Supplementation, through concentrated or legumes, did not increase the performance of suckling lambs grazing ryegrass, despite differences in neutral detergent fiber and acid detergent fiber by consumed pasture from animals that were smaller for the supplemented with legume. Suckling lambs kept in ryegrass produce similar carcasses of animals receiving supplement, despite gastrointestinal tract content with bile and urine and the proportion of the esophagus be higher (P<0,05) in lambs maintained in ryegrass and not supplemented and proportions of liver and intestine are higher (P<0,05) in lambs supplemented with concentrate. The color of the meat of was affected (P<0,05) by feeding system, being less opaque and red but more yellow the meat from not supplemented lambs. The tocopherol and cholesterol levels were higher (P<0,05) in meat of lambs not supplemented as well as lower contents of ash (P<0,05) were found in the meat of these animals. The water hold capacity was lower (P<0,05) in meat from animals supplemented with concentrate. Most intense characteristic flavor (P<0,05) was observed in meat from lambs who consumed concentrated; and more tender (P<0,05) was the meat of suckling lambs supplemented with legume. The use of white clover legume as supplementary private pasture provides rapid finishing of lambs with carcass and meat with quality, which makes this feeding system an option to finishing lambs. / Esta pesquisa foi realizada com o objetivo de avaliar o efeito da suplementação privativa, com concentrado ou leguminosa, sobre as características da pastagem, desempenho, características de carcaça, componentes corporais, características físico-químicas e sensoriais da carne de cordeiros lactentes mantidos em pastejo de azevém. Foram utilizados 27 cordeiros lactentes com aproximadamente 17 dias de idade e pesando 9,91±0,594kg, sendo estes distribuídos nos tratamentos que corresponderam aos sistemas de alimentação: cordeiros lactentes mantidos em pasto de azevém, cordeiros lactentes mantidos em pasto de azevém e suplementados com concentrado em comedouro privativo (creep feeding) e cordeiros lactentes mantidos em pasto de azevém e suplementados com leguminosa no pasto privativo (creep grazing). O suplemento concentrado era composto por milho, farelo de soja e calcário calcítico e foi fornecido ad libitum. O pasto suplementar foi composto pela leguminosa trevo branco. Avaliou-se as características do pasto de azevém e o desempenho dos cordeiros, que foram abatidos ao atingirem o peso corporal de 32 kg. Posteriormente avaliaram-se as características de carcaça, componentes corporais e características da carne dos animais. O delineamento experimental foi o inteiramente casualizado, onde os resultados foram submetidos à análise de variância e as médias comparadas pelo teste Tukey a 5% de significância. A suplementação privativa, concentrada ou através de leguminosa, não elevou o desempenho de cordeiros lactentes mantidos em pastejo de azevém, apesar das diferenças nos teores de fibra detergente neutro e fibra detergente ácido da pastagem consumida pelos animais que foram menores para os suplementados com leguminosa. Cordeiros lactentes mantidos em azevém produzem carcaças similares a dos animais que recebem suplemento, apesar do conteúdo do trato gastrintestinal juntamente com bile e urina e da proporção de esôfago ser maiores (P<0,05) nos cordeiros mantidos em azevém e não suplementados e as proporções de fígado e intestino grosso serem maiores (P<0,05) nos cordeiros suplementados com concentrado. A coloração da carne dos cordeiros foi influenciada (P<0,05) pelo sistema de alimentação, sendo a carne dos cordeiros lactentes que não receberam suplementação considerada a carne menos opaca, menos vermelha e mais amarela. Os teores de colesterol e tocoferol foram maiores (P<0,05) na carne de cordeiros não suplementados, bem como menores teores de cinzas (P<0,05) foram encontrados na carne desses animais. A capacidade de retenção de água foi menor (P<0,05) na carne dos animais suplementados com concentrado. Sabor característico mais intenso (P<0,05) foi observado na carne dos cordeiros que consumiram concentrado e maior maciez (P<0,05) foi encontrada na carne dos cordeiros suplementados com leguminosa. O uso da leguminosa trevo branco como pasto privativo suplementar proporciona rápida terminação de cordeiros com carcaças e carne de qualidade, o que torna este sistema alimentar uma opção para terminação de cordeiros.

Submitted by Marcele Costal de Castro (costalcastro@gmail.com) on 2017-09-06T13:30:34Z No. of bitstreams: 0 / Made available in DSpace on 2017-09-06T13:30:34Z (GMT). No. of bitstreams: 0 Previous issue date: 1984-05 / This work is concerned with the application of the finite element method to the study of creep brittle rupture of structural components. In the formulation material behavior is described by an elastocreep model in which the total strain rates are assumed to be the sum of elastic and creep components. The elastic strain rates are given by Hooke’s law while the creep strain rates and the damage rates are espressed by the multiaxial form of the Kachanov-Rabotnov equations proposed by Leckie and Hayhurst. The incremental equations of motion are derived from the principle of virtual work using an updated Lagrangian formulation which accounts for geometric effects due to large displacements, large rotations and deformation dependent loadings. The finite element incremental equations are developed according to a displacement-based formulation. Isoparametric elements with quadratic shape functions are employed for the domain discretization and simple numerical procedures are developed to deal with the presence of partially and/or fully ruptured elements in the mesh. For integration of the creep strain rate equations a family of implicit time marching schemes is developed which can be regarded as Runge-Kutta methods of second order. The integration of the coupled damage rate equations is performed using a first order predictor-corrector scheme with automatic time step length control. For material nonlinear problems only, a substructuring technique is employed in conjunction with the time integration algorithms. Selected numerical applications are presented and discussed in detail. Comparison with alternative numerical, analytical and/or experimental results is made whenever possible.

The effect of creep-fatigue conditions on structural components is not completely understood, and so the prediction of the behaviour and lifetime of such components is often unreliable and inaccurate. One of the methods proposed to improve the predictions is continuum damage mechanics, which provides a general description of material behaviour under degrading conditions. An estimate of life is usually based on the initial behaviour of a component. However, the work of previous researchers has shown that accurate predictions of the creep life of structures require that the stress redistribution due to the growth of damage is taken into account. In this thesis, this work is extended to fatigue and the effect of fatigue damage on life and deformation is studied for multibar model structures. The non-linear kinematic hardening rule is introduced as a constitutive law for cyclic plasticity that models many aspects of the cyclic behaviour of metals. Its properties are studied and it is extended to include the effects of damage on cyclic deformation. Creep-fatigue is studied by combining the models for fatigue and creep. Using published material data, the creep-fatigue behaviour of a two bar structure is studied and the results are compared with some experimental results. A study is made of finite element methods for solving problems involving plasticity and an example problem is solved. A model for the multiaxial behaviour of damaged material is proposed and examined for simple cases. The studies show that stress redistribution has a significant effect on fatigue life and the qualitative properties of the uniaxial models are very close to experimental observations. However, a lack of suitable and consistent experimental data on material behaviour means that the lifetime predictions and the multiaxial models are of uncertain accuracy.

Rectangular beams of high density single-crystal UO₂ were prepared from large grains of fused UO₂.They were deformed under constant load in four-point bending in hydrogen at temperatures from 1340 to 1420°C. The results appear to fit a creep equation of the form (formula omitted) where e = steady-state creep rate (formula omitted) Q = 118 ± 23 kcal/mole C = constant ; and 3 < n <4 in the regions of stress and temperatures examined. Faint slip lines were observed. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

An investigation of creep deformation in pure zirconia, using a creep-in-bending method with programmed temperature increase, showed the occurrence of superplasticity at temperatures near the monoclinic to tetragonal phase transformation. An interesting phenomenon was observed in a temporary halt to the creep process which occurred with continuing temperature increase beyond the phase transformation. Temperature dependence tests at a maximum fibre stress of 3140 psi gave overall activation energies for the creep process in pure zirconia in the monoclinic and tetragonal phases of 44 and 103 kcal/mole respectively. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

A project report submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 1998 / Aggregate stiffness is known to influence the magnitude of creep of concrete. The purpose of this research project was to quantify the influence of aggregate stiffness on the measured and predicted long-term creep behaviour of plain concrete. Basic and total creep tests were conducted on concrete specimens of two different strength grades for each of three different commonly used South African aggregate types (quartzite, granite and andesite). In addition, elastic modulus tests Were conducted on cores of the aggregate types considered. The test results revealed that no correlation exists between the creep of concrete and the stiffness of the included aggregate. These results appear to be attributable to the stress-strain behaviour of the aggregate/paste interfacial zone, in the case of aggregates with an elastic modulus in excess of 70 GPa. The experimental basic and total creep values from this investigation were compared with those predicted for each mix at the corresponding ages by the BS 8110 (1985), ACI 209 (1992), AS 3600 (1988), CEB-FIP (1970), CEB-FIP (1978), CEB-FIP (1990) and the RILEM Model B3 (1995). This comparison indicated that the results predicted by each model vary widely and that no correlation exists between the magnitude of the aggregate stiffness and the creep strains predicted by each model. / MT2017

Several theories of creep and creep rupture are reviewed. Specific attention is devoted to the brittle damage theory proposed by Kachanov. Creep, damage and life predictions for rectangular or circular cross section beams under bending and tensile loads are presented. Comparison with data for a Ni Superalloy showed life predictions could be 30X in excess of experimental values. This beam model also revealed that it is imperative that no bending moments be inadvertently applied during tensile creep testing. The creep-damage material model is extended to multidimensional situations. A refinement, whereby no damage accumulates in compression, is incorporated. A User-Material subroutine for this constitutive model has been formulated, and incorporated into the ABAQUS FEM package. Several verification examples are presented; one example is the creep-damage behaviour of a notched bar in tension. The value of reference stress techniques is discussed. Reference stress estimates for a centrifugally loaded bar, as well as for a cantilever under distributed loads, are presented. These could be useful in turbine blade design. Bibliography: pages 91-92.