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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Behaviour of Normal and High Strength Concrete Confined with Fibre Reinforced Polymers (FRP)

Cui, Ciyan 23 September 2009 (has links)
An extensive amount of research has been reported in previous literature on the behaviour of FRP-confined concrete subjected to concentric axial compression. However, data on the behaviour of high strength concrete confined with various types and configurations of FRP systems is still lacking and no consensus exists on the complete response of FRP-confined concrete. In addition, no appropriate design guidelines are currently available. This thesis reports results from an experimental program involving 112 cylindrical concrete specimens, 88 of which were FRP-wrapped and the remaining 24 were control specimens. All the specimens were 152 mm in diameter and 305 mm in length. Test variables included: amount of FRP materials used, strength and stiffness of FRP materials, concrete strength, and the health of concrete at the time of strengthening. Experimental results indicated that a pre-repair load of up to 77% of the unconfined concrete strength had no appreciable effect on the stress-strain response of FRP-confined concrete. With an increase of the unconfined concrete strength, the strength enhancement, energy absorption capacity, ductility factor and work (energy) index at rupture of FRP jackets all decreased remarkably. A positive correlation was found between confined concrete ductility and FRP rupture strain. In addition, a gradual post-peak failure of the specimens, observed previously from FRP-confined concrete columns tested at the University of Toronto, was also observed in some of the current tests -- owing to the high speed data acquisition system. That ductile failure can be attributed to the gradual unzipping failure of FRP jacket, which in turn is related to specimen size. A new constitutive model was developed based on material properties, force equilibrium and strain compatibility. The size effect was taken into account in the model, which is able to accommodate concrete with a wide range of strength (25 MPa to 110 MPa) confined with various types and configurations FRP systems. Design equations from CSA S806-02 and CSA S6-06 provide reasonable and conservative estimates for the FRP-confined concrete strength. To calculate the peak strain for FRP-confined concrete, an equation based on the work by Berthet et al. (2006) is proposed.
32

Development and assessment of non-destructive evaluation techniques for the measurment of stress and strain in biological materials

Coulter, Ryan David 07 June 2007 (has links)
The heterogeneous and anisotropic nature of wood material creates additional design challenges not present with the use of other structural materials such as steel and aluminum. The natural variation in the physical properties of wood members requires that the specified strengths and resistances used for design calculations be based on the quantities measured for the fifth percentile of all wood materials tested. The result is that design may be unnecessarily conservative and subsequently inefficient. The same properties that cause uncertainty surrounding the physical properties of biological materials also create difficulty in applying non-destructive evaluation techniques. Strain measurement is one particular technique that is extremely valuable for materials of known and consistent stress-strain relationships, but whose usefulness is diminished when applied to biological materials. To demonstrate the need for more accurate strain measurement in light-framed structures, the predictive calculations and structural modelling of a post-framed building was compared to its demonstrated performance. The analysis did not adequately reflect the actual performance of the building, and it was determined that additional monitoring of light-framed buildings through systems such as strain measurement was required to gain a better understanding of the performance characteristics in order to optimize evaluation techniques. This project aimed to develop a system that accurately measures strain in dimensional lumber of different types, which in turn will enable researchers to enhance monitoring the performance of light-frame structures and optimize design analysis and structural modelling techniques. The development of a methodology that provides a practical means by which to perform in-situ testing of post-frame buildings and decreases the complexity of post-frame building monitoring will contribute to the advancement of design and analysis techniques. In the calibration phase of the project, metal foil resistance strain gages were mounted onto wooden specimens with dimensions of 5 x 13 x 40 mm, 5 x 40 x 100 mm, and 2 x 20 x 50 mm, and acrylic specimens with dimensions of 3 x 25 x 75 mm. These specimens were then subjected to loading in an ATS universal testing machine in the Physical Properties Lab at the University of Manitoba. Stress-strain curves were developed based upon the observed stress and strain levels. These calibrated gages were then mounted on to a 38 x 89 mm specimen of S-P-F dimensional lumber which represented a typical light-framed building material. This assembly was then subjected to a similar loading procedure as the calibrated gage and stress-strain curves were generated once again. The slopes of the stress-strain curves developed from the two phases of the project were compared to determine if a consistent correlation existed. The three sizes of wood specimens did not demonstrate a consistent correlation. However, the acrylic specimen demonstrated consistent correlation amongst two groups of three with correlation coefficients within a forty percent range in one group and within a nine percent range in the other group. This suggests that further experimental refinements could produce the desired results.
33

Impact behavior and modeling of engineering polymers /

Duan, Yiping. January 1900 (has links)
Thesis (Ph.D.)--Tufts University, 2001. / Advisers: Anil Saigal; Robert Greif. Submitted to the Dept. of Mechanical Engineering. Includes bibliographical references (leaves 175-177). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
34

Influence of stress states on soil-water characteristics, conjunctive surface-subsurface flow modelling and stability analysis /

Tse, Man Kit. January 2007 (has links)
Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 145-154). Also available in electronic version.
35

Nonlinear Inelastic Mechanical Behavior Of Epoxy Resin Polymeric Materials

January 2011 (has links)
abstract: Polymer and polymer matrix composites (PMCs) materials are being used extensively in different civil and mechanical engineering applications. The behavior of the epoxy resin polymers under different types of loading conditions has to be understood before the mechanical behavior of Polymer Matrix Composites (PMCs) can be accurately predicted. In many structural applications, PMC structures are subjected to large flexural loadings, examples include repair of structures against earthquake and engine fan cases. Therefore it is important to characterize and model the flexural mechanical behavior of epoxy resin materials. In this thesis, a comprehensive research effort was undertaken combining experiments and theoretical modeling to investigate the mechanical behavior of epoxy resins subject to different loading conditions. Epoxy resin E 863 was tested at different strain rates. Samples with dog-bone geometry were used in the tension tests. Small sized cubic, prismatic, and cylindrical samples were used in compression tests. Flexural tests were conducted on samples with different sizes and loading conditions. Strains were measured using the digital image correlation (DIC) technique, extensometers, strain gauges, and actuators. Effects of triaxiality state of stress were studied. Cubic, prismatic, and cylindrical compression samples undergo stress drop at yield, but it was found that only cubic samples experience strain hardening before failure. Characteristic points of tensile and compressive stress strain relation and load deflection curve in flexure were measured and their variations with strain rate studied. Two different stress strain models were used to investigate the effect of out-of-plane loading on the uniaxial stress strain response of the epoxy resin material. The first model is a strain softening with plastic flow for tension and compression. The influence of softening localization on material behavior was investigated using the DIC system. It was found that compression plastic flow has negligible influence on flexural behavior in epoxy resins, which are stronger in pre-peak and post-peak softening in compression than in tension. The second model was a piecewise-linear stress strain curve simplified in the post-peak response. Beams and plates with different boundary conditions were tested and analytically studied. The flexural over-strength factor for epoxy resin polymeric materials were also evaluated. / Dissertation/Thesis / Ph.D. Mechanical Engineering 2011
36

Ruptura total do tendão de Aquiles : propriedades mecânicas tendíneas em indivíduos submetidos a diferentes protocolos de reabilitação

Geremia, Jeam Marcel January 2011 (has links)
Introdução. Rupturas agudas do tendão de Aquiles afetam as propriedades mecânicas tendíneas. Estudos vêm preconizando o uso de mobilização precoce (tratamento acelerado) para evitar grandes prejuízos tendíneos. Entretanto, estudos que avaliem as propriedades mecânicas do tendão de Aquiles de humanos após ruptura total, submetidos à mobilização precoce, não foram encontrados na literatura específica da área. Objetivo: comparar as propriedades mecânicas e morfológicas do tendão de Aquiles entre pacientes submetidos a tratamento conservador e pacientes submetidos a tratamento acelerado (mobilização precoce) após a sutura do tendão de Aquiles. Materiais e Métodos: A amostra foi dividida intencionalmente em três grupos: controle (CTR; n=9), grupo conservador (CON; n=9; Pós-Cirúrgico: 28,3±3,6 meses) e grupo acelerado (ACE; n=9; Pós-Cirúrgico: 29,8±4,8 meses). Um dinamômetro isocinético foi utilizado para avaliação do torque dos grupos musculares flexores plantares e flexores dorsais do tornozelo. Foram obtidos os valores de área de secção transversa (AST) e comprimento do tendão (CT) de Aquiles. Para a avaliação da relação stress-strain os sujeitos realizaram duas contrações voluntárias máximas em rampa para flexão plantar no ângulo de 0º com duração de 10 segundos cada. Durante as duas contrações voluntárias máximas o deslocamento da JMT do músculo gastrocnêmio medial com o tendão de Aquiles foi verificado por meio de ultrassonografia utilizando uma sonda com arranjo linear. Simultaneamente a este procedimento, foi adquirido o sinal eletromiográfico do músculo tibial anterior, utilizado para a correção da força do tendão de Aquiles. As imagens necessárias para o cálculo do strain, bem como os sinais EMG e de torque foram sincronizados. Os valores máximos de stress, strain, força, deformação, módulo de Young, CT e AST foram comparados. Resultados: Não foram encontradas diferenças significativas nas propriedades mecânicas e morfológicas entre membros do grupo CTR. Não houve diferença significativa entre os membros saudáveis dos grupos CON e ACE e os do grupo CTR. Dessa forma, os membros saudáveis dos grupos CON e ACE foram utilizados como controle do membro lesão em ambos os grupos. Tanto no grupo CON, quanto no grupo ACE, o stress, a força e o módulo de Young apresentaram menores valores no membro lesionado, enquanto que o strain obtido em 10MPa e a AST foram maiores neste membro comparado ao contralateral saudável. Não houve diferença significativa no CT entre os membros, independente do grupo. Não foram encontradas diferenças significativas nas propriedades mecânicas, bem como na morfologia do tendão de Aquiles na comparação entre os membros lesionados dos grupos CON e ACE. Discussão: Esta maior complacência tendínea encontrada nos tendões lesados, independente do grupo, pode estar associada tanto as adaptações decorrentes da lesão que não recuperaram a níveis de normalidade, bem como a mudança nos hábitos de vida após a lesão. Além disso, o protocolo acelerado de reabilitação não foi capaz de reduzir as perdas advindas da ruptura tendínea. Tal resultado pode estar associado à especificidade do protocolo utilizado, que foi desenhado para ganho de flexibilidade no tornozelo e não para força muscular. Conclusão: Em um período mínimo de 21 meses de pós-operatório o tendão de Aquiles ainda apresenta efeitos deletérios da ruptura total nas propriedades estruturais e mecânicas do tendão. O protocolo de reabilitação utilizado não foi eficaz para a redução de tais efeitos. / Introduction. Acute Achilles tendon rupture affects the mechanical properties of the tendon. Despite the tendinous adaptations generated by decreased use, few studies have used early weight bearing (accelerated treatment) to avoid the large losses in the musculoskeletal tissues. In addition, studies that evaluated the mechanical properties of human Achilles tendon after acute rupture, subjected to early weight bearing were not found. Purpose: to compare the mechanical and morphological properties of the Achilles tendon between patients undergoing conservative and accelerated treatment, after Achilles tendon suture. Materials and Methods: subjects were intentionally allocated into three groups: control (CTR; n=9), conservative treatment (CON; n=9; Postsurgical time: 28.3±3.6 months) and accelerated treatment (ACC; n=9; Postsurgical time: 29.8±4.8 months). An isokinetic dynamometer was used to evaluate the torque production of ankle dorsi- and plantar-flexor muscles. The values of Achilles tendon cross sectional area (CSA) and length were obtained. To evaluate the stress-strain relation, patients were asked to produce two isometric maximal voluntary contractions during a ramp protocol (angle: neutral position; duration: 10 seconds) of the plantar flexor muscles. During the maximal contractions the displacement of the myotendinous junction of the gastrocnemius medialis muscle was evaluated by ultrasound with a linear array probe. Simultaneously, the electromyography (EMG) signal of the tibialis anterior was recorded, and used to correct the Achilles tendon force. The ultrasound images, EMG signals and torque were synchronized. The maximal values of stress, strain, force, displacement, Young’s modulus, tendon length and CSA were compared. Results: there were no significant differences in the morphological and mechanical properties between limbs in the CTR group. Moreover, there were no significant differences in the morphological and mechanical properties between healthy limbs amongst groups. Thus, the healthy limbs of the CON and ACC groups were used as control of the injured limb. In CON and ACC groups the stress, force and Young’s modulus had lower values in the injured limb compared to the contralateral healthy limb, while the strain obtained at 10MPa and the CSA were higher in the injured limb. There were no significant differences in the tendon length between groups and limbs. Moreover, there were no significant differences in the morphological and mechanical properties between injured limbs (CON and ACC). Discussion: The highest tendinous compliance found on the injured tendons, independent of the group might be associated to both the adaptations due to injury that did not return to normal healthy levels and to possible changes in the daily life activities after injury. In addition, the accelerated treatment was unable to reduce the losses due to tendon rupture. These results might be associated to the specificity of the rehabilitation protocol used that was designed for the gain of flexibility and not for strength gains. Conclusion: Twenty-one months post-surgery were unable to recover the deleterious effects of acute Achilles tendon rupture on the structural and mechanical tendon properties. The accelerated rehabilitation protocol was ineffective to reduce these deleterious effects.
37

Ruptura total do tendão de Aquiles : propriedades mecânicas tendíneas em indivíduos submetidos a diferentes protocolos de reabilitação

Geremia, Jeam Marcel January 2011 (has links)
Introdução. Rupturas agudas do tendão de Aquiles afetam as propriedades mecânicas tendíneas. Estudos vêm preconizando o uso de mobilização precoce (tratamento acelerado) para evitar grandes prejuízos tendíneos. Entretanto, estudos que avaliem as propriedades mecânicas do tendão de Aquiles de humanos após ruptura total, submetidos à mobilização precoce, não foram encontrados na literatura específica da área. Objetivo: comparar as propriedades mecânicas e morfológicas do tendão de Aquiles entre pacientes submetidos a tratamento conservador e pacientes submetidos a tratamento acelerado (mobilização precoce) após a sutura do tendão de Aquiles. Materiais e Métodos: A amostra foi dividida intencionalmente em três grupos: controle (CTR; n=9), grupo conservador (CON; n=9; Pós-Cirúrgico: 28,3±3,6 meses) e grupo acelerado (ACE; n=9; Pós-Cirúrgico: 29,8±4,8 meses). Um dinamômetro isocinético foi utilizado para avaliação do torque dos grupos musculares flexores plantares e flexores dorsais do tornozelo. Foram obtidos os valores de área de secção transversa (AST) e comprimento do tendão (CT) de Aquiles. Para a avaliação da relação stress-strain os sujeitos realizaram duas contrações voluntárias máximas em rampa para flexão plantar no ângulo de 0º com duração de 10 segundos cada. Durante as duas contrações voluntárias máximas o deslocamento da JMT do músculo gastrocnêmio medial com o tendão de Aquiles foi verificado por meio de ultrassonografia utilizando uma sonda com arranjo linear. Simultaneamente a este procedimento, foi adquirido o sinal eletromiográfico do músculo tibial anterior, utilizado para a correção da força do tendão de Aquiles. As imagens necessárias para o cálculo do strain, bem como os sinais EMG e de torque foram sincronizados. Os valores máximos de stress, strain, força, deformação, módulo de Young, CT e AST foram comparados. Resultados: Não foram encontradas diferenças significativas nas propriedades mecânicas e morfológicas entre membros do grupo CTR. Não houve diferença significativa entre os membros saudáveis dos grupos CON e ACE e os do grupo CTR. Dessa forma, os membros saudáveis dos grupos CON e ACE foram utilizados como controle do membro lesão em ambos os grupos. Tanto no grupo CON, quanto no grupo ACE, o stress, a força e o módulo de Young apresentaram menores valores no membro lesionado, enquanto que o strain obtido em 10MPa e a AST foram maiores neste membro comparado ao contralateral saudável. Não houve diferença significativa no CT entre os membros, independente do grupo. Não foram encontradas diferenças significativas nas propriedades mecânicas, bem como na morfologia do tendão de Aquiles na comparação entre os membros lesionados dos grupos CON e ACE. Discussão: Esta maior complacência tendínea encontrada nos tendões lesados, independente do grupo, pode estar associada tanto as adaptações decorrentes da lesão que não recuperaram a níveis de normalidade, bem como a mudança nos hábitos de vida após a lesão. Além disso, o protocolo acelerado de reabilitação não foi capaz de reduzir as perdas advindas da ruptura tendínea. Tal resultado pode estar associado à especificidade do protocolo utilizado, que foi desenhado para ganho de flexibilidade no tornozelo e não para força muscular. Conclusão: Em um período mínimo de 21 meses de pós-operatório o tendão de Aquiles ainda apresenta efeitos deletérios da ruptura total nas propriedades estruturais e mecânicas do tendão. O protocolo de reabilitação utilizado não foi eficaz para a redução de tais efeitos. / Introduction. Acute Achilles tendon rupture affects the mechanical properties of the tendon. Despite the tendinous adaptations generated by decreased use, few studies have used early weight bearing (accelerated treatment) to avoid the large losses in the musculoskeletal tissues. In addition, studies that evaluated the mechanical properties of human Achilles tendon after acute rupture, subjected to early weight bearing were not found. Purpose: to compare the mechanical and morphological properties of the Achilles tendon between patients undergoing conservative and accelerated treatment, after Achilles tendon suture. Materials and Methods: subjects were intentionally allocated into three groups: control (CTR; n=9), conservative treatment (CON; n=9; Postsurgical time: 28.3±3.6 months) and accelerated treatment (ACC; n=9; Postsurgical time: 29.8±4.8 months). An isokinetic dynamometer was used to evaluate the torque production of ankle dorsi- and plantar-flexor muscles. The values of Achilles tendon cross sectional area (CSA) and length were obtained. To evaluate the stress-strain relation, patients were asked to produce two isometric maximal voluntary contractions during a ramp protocol (angle: neutral position; duration: 10 seconds) of the plantar flexor muscles. During the maximal contractions the displacement of the myotendinous junction of the gastrocnemius medialis muscle was evaluated by ultrasound with a linear array probe. Simultaneously, the electromyography (EMG) signal of the tibialis anterior was recorded, and used to correct the Achilles tendon force. The ultrasound images, EMG signals and torque were synchronized. The maximal values of stress, strain, force, displacement, Young’s modulus, tendon length and CSA were compared. Results: there were no significant differences in the morphological and mechanical properties between limbs in the CTR group. Moreover, there were no significant differences in the morphological and mechanical properties between healthy limbs amongst groups. Thus, the healthy limbs of the CON and ACC groups were used as control of the injured limb. In CON and ACC groups the stress, force and Young’s modulus had lower values in the injured limb compared to the contralateral healthy limb, while the strain obtained at 10MPa and the CSA were higher in the injured limb. There were no significant differences in the tendon length between groups and limbs. Moreover, there were no significant differences in the morphological and mechanical properties between injured limbs (CON and ACC). Discussion: The highest tendinous compliance found on the injured tendons, independent of the group might be associated to both the adaptations due to injury that did not return to normal healthy levels and to possible changes in the daily life activities after injury. In addition, the accelerated treatment was unable to reduce the losses due to tendon rupture. These results might be associated to the specificity of the rehabilitation protocol used that was designed for the gain of flexibility and not for strength gains. Conclusion: Twenty-one months post-surgery were unable to recover the deleterious effects of acute Achilles tendon rupture on the structural and mechanical tendon properties. The accelerated rehabilitation protocol was ineffective to reduce these deleterious effects.
38

Ruptura total do tendão de Aquiles : propriedades mecânicas tendíneas em indivíduos submetidos a diferentes protocolos de reabilitação

Geremia, Jeam Marcel January 2011 (has links)
Introdução. Rupturas agudas do tendão de Aquiles afetam as propriedades mecânicas tendíneas. Estudos vêm preconizando o uso de mobilização precoce (tratamento acelerado) para evitar grandes prejuízos tendíneos. Entretanto, estudos que avaliem as propriedades mecânicas do tendão de Aquiles de humanos após ruptura total, submetidos à mobilização precoce, não foram encontrados na literatura específica da área. Objetivo: comparar as propriedades mecânicas e morfológicas do tendão de Aquiles entre pacientes submetidos a tratamento conservador e pacientes submetidos a tratamento acelerado (mobilização precoce) após a sutura do tendão de Aquiles. Materiais e Métodos: A amostra foi dividida intencionalmente em três grupos: controle (CTR; n=9), grupo conservador (CON; n=9; Pós-Cirúrgico: 28,3±3,6 meses) e grupo acelerado (ACE; n=9; Pós-Cirúrgico: 29,8±4,8 meses). Um dinamômetro isocinético foi utilizado para avaliação do torque dos grupos musculares flexores plantares e flexores dorsais do tornozelo. Foram obtidos os valores de área de secção transversa (AST) e comprimento do tendão (CT) de Aquiles. Para a avaliação da relação stress-strain os sujeitos realizaram duas contrações voluntárias máximas em rampa para flexão plantar no ângulo de 0º com duração de 10 segundos cada. Durante as duas contrações voluntárias máximas o deslocamento da JMT do músculo gastrocnêmio medial com o tendão de Aquiles foi verificado por meio de ultrassonografia utilizando uma sonda com arranjo linear. Simultaneamente a este procedimento, foi adquirido o sinal eletromiográfico do músculo tibial anterior, utilizado para a correção da força do tendão de Aquiles. As imagens necessárias para o cálculo do strain, bem como os sinais EMG e de torque foram sincronizados. Os valores máximos de stress, strain, força, deformação, módulo de Young, CT e AST foram comparados. Resultados: Não foram encontradas diferenças significativas nas propriedades mecânicas e morfológicas entre membros do grupo CTR. Não houve diferença significativa entre os membros saudáveis dos grupos CON e ACE e os do grupo CTR. Dessa forma, os membros saudáveis dos grupos CON e ACE foram utilizados como controle do membro lesão em ambos os grupos. Tanto no grupo CON, quanto no grupo ACE, o stress, a força e o módulo de Young apresentaram menores valores no membro lesionado, enquanto que o strain obtido em 10MPa e a AST foram maiores neste membro comparado ao contralateral saudável. Não houve diferença significativa no CT entre os membros, independente do grupo. Não foram encontradas diferenças significativas nas propriedades mecânicas, bem como na morfologia do tendão de Aquiles na comparação entre os membros lesionados dos grupos CON e ACE. Discussão: Esta maior complacência tendínea encontrada nos tendões lesados, independente do grupo, pode estar associada tanto as adaptações decorrentes da lesão que não recuperaram a níveis de normalidade, bem como a mudança nos hábitos de vida após a lesão. Além disso, o protocolo acelerado de reabilitação não foi capaz de reduzir as perdas advindas da ruptura tendínea. Tal resultado pode estar associado à especificidade do protocolo utilizado, que foi desenhado para ganho de flexibilidade no tornozelo e não para força muscular. Conclusão: Em um período mínimo de 21 meses de pós-operatório o tendão de Aquiles ainda apresenta efeitos deletérios da ruptura total nas propriedades estruturais e mecânicas do tendão. O protocolo de reabilitação utilizado não foi eficaz para a redução de tais efeitos. / Introduction. Acute Achilles tendon rupture affects the mechanical properties of the tendon. Despite the tendinous adaptations generated by decreased use, few studies have used early weight bearing (accelerated treatment) to avoid the large losses in the musculoskeletal tissues. In addition, studies that evaluated the mechanical properties of human Achilles tendon after acute rupture, subjected to early weight bearing were not found. Purpose: to compare the mechanical and morphological properties of the Achilles tendon between patients undergoing conservative and accelerated treatment, after Achilles tendon suture. Materials and Methods: subjects were intentionally allocated into three groups: control (CTR; n=9), conservative treatment (CON; n=9; Postsurgical time: 28.3±3.6 months) and accelerated treatment (ACC; n=9; Postsurgical time: 29.8±4.8 months). An isokinetic dynamometer was used to evaluate the torque production of ankle dorsi- and plantar-flexor muscles. The values of Achilles tendon cross sectional area (CSA) and length were obtained. To evaluate the stress-strain relation, patients were asked to produce two isometric maximal voluntary contractions during a ramp protocol (angle: neutral position; duration: 10 seconds) of the plantar flexor muscles. During the maximal contractions the displacement of the myotendinous junction of the gastrocnemius medialis muscle was evaluated by ultrasound with a linear array probe. Simultaneously, the electromyography (EMG) signal of the tibialis anterior was recorded, and used to correct the Achilles tendon force. The ultrasound images, EMG signals and torque were synchronized. The maximal values of stress, strain, force, displacement, Young’s modulus, tendon length and CSA were compared. Results: there were no significant differences in the morphological and mechanical properties between limbs in the CTR group. Moreover, there were no significant differences in the morphological and mechanical properties between healthy limbs amongst groups. Thus, the healthy limbs of the CON and ACC groups were used as control of the injured limb. In CON and ACC groups the stress, force and Young’s modulus had lower values in the injured limb compared to the contralateral healthy limb, while the strain obtained at 10MPa and the CSA were higher in the injured limb. There were no significant differences in the tendon length between groups and limbs. Moreover, there were no significant differences in the morphological and mechanical properties between injured limbs (CON and ACC). Discussion: The highest tendinous compliance found on the injured tendons, independent of the group might be associated to both the adaptations due to injury that did not return to normal healthy levels and to possible changes in the daily life activities after injury. In addition, the accelerated treatment was unable to reduce the losses due to tendon rupture. These results might be associated to the specificity of the rehabilitation protocol used that was designed for the gain of flexibility and not for strength gains. Conclusion: Twenty-one months post-surgery were unable to recover the deleterious effects of acute Achilles tendon rupture on the structural and mechanical tendon properties. The accelerated rehabilitation protocol was ineffective to reduce these deleterious effects.
39

Výroba kolíkové koncovky objemovým tvářením / Production of terminal pin by cold forming

Šuranský, David January 2017 (has links)
The thesis presents a manufacturing technology proposition for a terminal pin made of copper according to ČSN 42 3001.1 located in combution engine distributor in a series of 320 000 pcs. Based on a literature study, 3 versions of operation sequence were proposed, 2 of them with concern for lowest number of operations possible and the third, chosen one, was designed so the strain and therefore mechanical properties were equal in whole volume of final part. Forming force and work were calculated, utilizing the Johnson-Cook material model. Overall calculated forming force was 64,5 kN and total work for one part 189 J. Subsequently technical drawings of die and punch for the second operation of forward extrusion of shaft were processed along with workspace assembly drawing for the Šmeral TPM 5 machine, which was chosen for the fabrication. Economic evaluation set the costs for one part manufactured 0,09 Eur and equilibrium point, after which the production generates profit, located at 170 000 pcs produced.
40

Deformačně-napěťová analýza aterosklerotické tepny / Stress-strain analysis of artery with atheroma

Maša, Marek January 2008 (has links)
The main goal of this diploma thesis was the stress-strain analysis of iliac artery with atheroma.This problem was solved using finite element method (FEM).For the calculation purposes three two-dimensional models were created. The geometry was gained from transversal sections through the iliac artery with ateroma. This geometry is educed from used literature review. The main calculation process was run by ANSYS 11.0 program system.

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