Abstract The failure of ligament reconstruction has different risk factors, among which we can highlight the period before its incorporation, which is a mechanically vulnerable period. Loss of resistance over time is a characteristic of living tissues. Dissection with bone insertions of the cruciate ligaments of animal models is not described; however, it is essential for monoaxial assays to extract information from tests such as relaxation. The present work describes the dissection used for the generation of a test body for the performance of nondestructive tests to evaluate the mechanical behavior. We performed dissection of four porcino knee ligaments, proposing a dissection technique for the cruciate ligaments with bone inserts for comparison with collateral ligaments. The ligaments were submitted to relaxation tests and had strain gauges placed during the tests. The results showed viscoelastic behavior, validated by strain gauges and with a loss over time; with some ligaments presenting with losses of up to 20%, a factor to be considered in future studies. The present work dissected the four main ligaments of the knee demonstrating the posterior approach that allows maintaining their bone insertions and described the fixation for the monotonic uniaxial trials, besides being able to extract the viscoelastic behavior of the four ligaments of the knee, within the physiological limits of the knee.

Resumo A falha da reconstrução ligamentar tem diferentes fatores de risco, dentre os quais podemos destacar o período antes da sua incorporação, o qual configura um período mecânico vulnerável. A perda de resistência ao longo do tempo é uma característica dos tecidos vivos. A dissecção com as inserções ósseas dos ligamentos cruzados de modelos animais não é descrita; todavia, para os ensaios monoaxiais, é fundamental extrair as informações de ensaios como os de relaxação. O presente trabalho realiza a descrição da dissecção utilizada para a geração de corpo de prova para a realização de ensaios não destrutivos para avaliar o comportamento mecânico. Realizamos dissecção de quatro ligamentos de joelho porcino, propondo uma técnica de dissecção para os ligamentos cruzados com as inserções ósseas para comparação com os colaterais. Os ligamentos foram submetidos a testes de relaxação e foram colocadas strain gauges durante os testes. Os resultados mostraram comportamento viscoelástico, validado pelas strain gauges e com uma perda ao longo do tempo, sendo que, em alguns ligamentos, as perdas chegaram a até 20%, fator este a ser considerado em trabalhos futuros. O presente trabalho dissecou os quatro principais ligamentos do joelho, demonstrando a abordagem posterior que permite manter as suas inserções ósseas e descrevendo a fixação para os ensaios uniaxiais monotônicos, além de ter conseguido extrair o comportamento viscoelástico dos quatro ligamentos do joelho dentro dos limites fisiológicos do joelho.

RESUMO Introdução: O joelho tem demonstrado um aumento significativo de frequência de lesão devido à prática esportiva. Esse aumento e a melhoria das técnicas cirúrgicas de reconstrução ligamentar têm levado a maior indicação desse tratamento com o objetivo de se atingir uma função próxima do normal. Objetivo: Realizar uma análise preliminar do comportamento ligamentar. Métodos: O estudo consistiu na validação de um modelo anatômico do porco, em que cinco modelos foram submetidos a ensaios mecânicos. Foram coletados os dados das cargas do modelo in situ e das deformações do ligamento cruzado posterior. Resultados: Na análise da carga trativa, foi observado que em um primeiro momento existe um aumento não linear das tensões. Em sequência, há uma resposta intermediária relativamente linear do joelho suíno até a falha em torno de 1.200 N. A deformação versus tempo mostrou uma resposta do ligamento cruzado posterior, que também possui uma resposta relativamente linear. Conclusão: Observou-se um comportamento linear na faixa de 1.000 até 5.000 microstrains na deformação do ligamento cruzado posterior. Sugerem-se novos estudos para a compreensão dos ligamentos do joelho quanto ao comportamento deles na sua função. Nível de Evidência IV, Estudo Mecânico.

ABSTRACT Introduction: The knee has shown a significant increase in the frequency of injury due to sports practice. This increase and the improvement of surgical techniques of ligament reconstruction have led to a greater indication of this treatment to achieve a function close to normal. Objective: To conduct a preliminary analysis of the ligament behavior. Methods: The study consisted of the validation of an anatomical model of the pig, in which five models were subjected to mechanical tests. The data on the loads of the in situ model and the strains of the posterior cruciate ligament were collected. Results: The analysis of the tensile load showed, at first, a nonlinear increase in stresses. Subsequently, the pig’s knee showed a relatively linear intermediate response until failure around 1,200 N. Strain × time showed a response of the posterior cruciate ligament, which also has a relatively linear response. Conclusion: We observed a linear behavior in the range of 1,000 to 5,000 microstrains in the strain of the posterior cruciate ligament. We suggest further studies to understand knee ligaments regarding their behavior in their function. Level of Evidence IV, Biomechanical Study.

ABSTRACT The adhesive fracture resistance of structural adhesive joints in mode II, ��IIC, is accessed through the application of two models that prescind of the measurement of the crack length during the subjection of ENF specimens to three-point bending monotonic tests. The load vs transversal displacement results are used in two different approaches: a damage model and a cohesive zone model. The first one was used in test where the crack propagation was unstable and the second one was used for stable crack propagations. These initial results show the viability of the models and show that both: initial crack length and transversal load rate; have great influence in ��IIC evaluation.

Abstract Traditional fatigue limit measurements are expensive and time consuming, requiring a large number of specimens and a long time to be completed. An alternative approach is used in this work to obtain the fatigue limit of a cold drawn steel, in a rotating bending machine, by monitoring temperature variations induced by different load range levels in just a few specimens. Comparisons with Dixon’s traditional up-and-down method confirm that this thermographic approach is indeed a much more efficient, faster, and cheaper method to obtain fatigue limits.

ABSTRACT: Sandwich structures are nowadays widely used due its excellent characteristics of matching light weight with high bend stiffness. However the complex nature of its composition turns the estimation of its mechanical elastic properties challenging. The objective of the present article is to propose an analytical/experimental model to estimate the orthotropic elastic properties of this composite material. To accomplish this objective a theory of anisotropic plates is used together to an extensometric experimental approach. A sandwich laminate specimen, instrumented with strain gages, was submitted through pure bending loading by a mechanical testing machine on a 4-point bending apparatus. The result of this research was the determination of 4 orthotropic elastic properties of the sandwich laminate specimen, namely: the longitudinal and transversal Young moduli, the shear modulus, and the Poisson's ratio.

Abstract High strength wires, which have a poor notch sensitivity performance, are currently been used on many offshore applications where high stresses without yielding are demanded. To assess these wires notch sensitivity, an integrated approach was implemented. An experimental program was conducted, through the realization of fatigue tests to obtain the fatigue limit for notched and notched free specimens to assess the fatigue stress concentration factor. A numerical approach using Finite Element Method, and an analytical model, available in technical literature, were used to assess the stress concentration factor. With both results, the notch sensitivity could be obtained.

Abstract A human femur model, submitted to static loads, is analyzed through the utilization of three material constitutive relationships, namely: isotropic, transversally isotropic and orthotropic. The influence of bone anisotropy with respect to principal stress/strain distribution on human femur external surface was accessed through the use of analytical and finite element approaches. The models results show that the principal angles at a medial path bone surface have a good correlation with human femur bone lamellae angles.