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A new method is proposed in order to estimate the shear strength of schistosity planes in slate in terms of Mohr-Coulomb cohesion and internal friction angle. The procedure consists in carrying out the Brazilian method under different loading-foliation angles, for which experimental tests were achieved in slates from the northwest of the Iberian Peninsula (Spain). The experimental fracture patterns were analytically studied and justified by simulating the stress field in the discontinuity planes contained in the whole sample, taking into account the first failure registered in the tests. By combining experimental and analytical studies and a procedure based on the representation of the threshold state of stresses-in the elastic regime-in the failure plane, it is possible to estimate the foliation's strength envelope through a lineal adjustment according to the Mohr-Coulomb criterion and, thus, to characterize the layering. Finally, the proposed procedure was validated by the direct shear test. The cohesion and the internal friction angle obtained with this convenctional test were very close to that calculated by the proposed method, verifying the methodology developed by the authors. This procedure may be interesting in various engineering applications, either in the study of the properties of cleavage in slate, which is commonly used as an industrial rock, or in dam foundations, underground excavations and slope engineering, since one of the main failures in civil engineering is due to sliding along weak planes. KeywordsBrazilian test . Slate . Foliation . Internal friction angle . Cohesion . Strength parameters finished thickness. For this reason, slate is commonly used as 39 roofing or flooring, being an important economic sector in 40 Spain, which is the world leader in roofing slate production. 41 Besides its popular use in building, slate is frequently encoun-42 tered in various engineering applications, such as dam foun-43 dations, underground excavations and slope engineering 44 (Chen et al. 2016). Thus, to establish the mechanical proper-45 ties of jointed rocks along weak planes is important for 46 the exploitation, design and construction of civil engineering 47 works. 48 Direct shear testing is the favorable way to characterize the 49 discontinuities. The portable shear box described by Brown 50 and Walton (1975) is one of the most used testing systems in 51 order to calculate the cohesion and the internal friction angle 52 by assuming the Mohr-Coulomb criterion. Once the specimen * C. Gonzalez-Nicieza

The present research analyses the configuration of jaws to avoid the premature failure of the disc in the Brazilian test. The objective is to depict the loading device configuration that most likely produces results comparable to the Hondros' analytical stress solution. To this end, several numerical analyses have been carried out for different contact angles with the Finite Element Method. It was deduced that the final contact angle plays an important part in the success of the Brazilian test and that the Griffith criterion can be fulfilled if the equivalent stress is calculated. Additionally, the orientation of the forces in the contact between the loading device and the disc has been studied for different friction conditions. According to the numerical results, it was found that a loading arc configuration of 20º shows the best agreement with the probable values given by the analytical stress model when the uncertainty of its magnitudes is taken into account. The study also demonstrates that the friction in the contact between the optimal loading configuration and the disc does not seem to significantly affect the theoretical predictions in the centre of the disc.

Bicycle manufacturers are using new materials in order to improve the bicycle performance. In high-level cycling, magnesium, aluminium, titanium and carbon fibre, have replaced steel with the purpose of improving the weight / rigidity ratio.Due to cost factors and ease of machining, aluminium is widely used in bicycle cranks manufacturing. In order to improve the external aspect of the final product and protect the external surface of the component, some surface treatments must be applied.In the case of aluminium, anodizing is the most extended treatment, due to several factors as low cost, visual aspect, variety of colours and finishing. However, this treatment may reduce the fatigue resistance of the component.In this work, the best compromise between anodizing depth and fatigue resistance performance of a bicycle crank has been analysed in order to provide an optimum solution to improve the performance of the component.

In this study, a finite element model of a bicycle crank arm are compared to experimental results. The structural integrity of the crank arm was analyzed in a universal dynamic test bench. The instrumentation used has allowed us to know the fatigue behavior of the component tested. For this, the prototype was instrumented with three rectangular strain gauge rosettes bonded in areas where failure was expected. With the measurements made by strain gauges and the forces registers from the load cell used, it has been possible to determine the state of the stresses for different loads and boundary conditions, which has subsequently been compared with a finite element model. The simulations show a good agreement with the experimental results, when the potential sources of uncertainties are considered in the validation process. This analysis allowed us to improve the original design, reducing its weight by 15%. The study allows us to identify the manufacturing process that requires the best metrological control to avoid premature crank failure. Finally, the numerical fatigue analysis carried out allows us to conclude that the new crank arm can satisfy the structural performance demanded by the international bicycle standard. Additionally, it can be suggested to the standard to include the verification that no permanent deformations have occurred in the crank arm during the fatigue test. It has been observed that, in some cases this bicycle component fulfils the minimum safety requirements, but presents areas with plastic strains, which if not taken into account can increase the risk of injury for the cyclist due to unexpected failure of the component.

This research study presents a new theoretical model to calculate the indirect tensile strength for the Brazilian disk with loading arcs, based on numerical simulations, two-dimensional elasticity theory, and Griffith failure criterion. The new expression incorporates a no uniform contact pressure distribution determined by the results of the simulations with the finite element method. A computational experiment design has been developed to test the accuracy of the predictions made with the proposed model. This study demonstrates that the stresses predicted with the new model are closer to those determined by the finite element models than other theoretical solutions available in the literature. Additionally, a comparative analysis with experimental results obtained by other authors also indicates that the new model provides a more accurate magnitude of the indirect tensile strength.

In this research, the performance and movements of amateur and professional cyclists were analyzed. For this, reflective markers have been used on different parts of the body of the participants in conjunction with sports cameras and a mobile power meter. The trajectories of the markers have been obtained with the software Kinovea and subsequently analyzed using error ellipses. It is demonstrated that the error ellipses help determine movement patterns in the knees, back, and hip. The covariance of the error ellipses can be indicative of the alignment and symmetry of the frontal movement of the knees. In addition, it allows verifying the alignment of the spine and the symmetry of the hip. Finally, it is shown that it is necessary to consider the uncertainty of the power devices since it considerably affects the evaluation of the cyclists’ performance. Devices with high uncertainty will demand a greater effort from the cyclist to meet the power required in the endurance test developed. The statistical magnitudes considered help to analyze power and evaluate the cyclists’ performance.