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This paper presents an investigation into 3D viscoelastic behaviour of bituminous mixture. Complex modulus tests were performed at ENTPE laboratory on cylindrical samples, for three different modes of sinusoidal loading: only tension, only compression and tension–compression. Stress-controlled mode was used for cyclic tension tests and cyclic compression tests whereas cyclic tension–compression tests were conducted in strain-controlled mode. For all loading conditions, the strain amplitude of sinusoidal cyclic loadings is less than 60 µm/m. Complex modulus E * and complex Poisson’s ratio ν * were measured at five temperatures ranging from 1 to 30 °C and at six frequencies ranging from 0.03 to 10 Hz. The results indicated that complex moduli are the same for the three modes of loading for average and low temperatures. Rather small differences were obtained between complex modulus values obtained from the three types of loading for higher temperatures. These differences could be explained by nonlinearity (modulus value depending on strain level) and accumulated strain existing for only tension and only compression type tests. No noticeable differences in complex Poisson’s ratio could be obtained from the three modes of loading.

Background To compare the biomechanical in-vitro characteristics of limited-contact dynamic compression plate (LC-DCP) and locking compression plate (LCP) constructs in an osteotomy gap model of femoral fracture in neonatal calves. Pairs of intact femurs from 10 calves that had died for reasons unrelated to the study were tested. A 7-hole LC-DCP with six 4.5 mm cortical screws was used in one femur and a 7-hole LCP with four 5.0 mm locking and two 4.5 mm cortical screws was used in the corresponding femur. The constructs were tested to failure by cyclic compression at a speed of 2 mm/s within six increasing force levels. Results The bone-thread interface was stripped in 21 of 80 cortical screws (26.3%) before a pre-set insertion torque of 3 Nm was achieved. Only 3 corresponding intact pairs of constructs could be statistically compared for relative structural stiffness, actuator excursion and width of the osteotomy gap. Relative structural stiffness was significantly greater, actuator excursion and width of the osteotomy gap were significantly smaller in the LCP constructs. While failure occurred by loosening of the screws in the LC-DCP constructs, locking constructs failed by cutting large holes in the soft distal metaphyseal bone. Conclusions An insertion torque sufficient to provide adequate stability in femurs of newborn calves could not be achieved reliably with 4.5 mm cortical screws. Another limiting factor for both constructs was the weak cancellous bone of the distal fracture fragment. LCP constructs were significantly more resistant to compression than LC-DCP constructs., BMC Veterinary Research, 8, ISSN:1746-6148

Car manufacturers use virtual human models in order to ensure the passengers safety during crash events. To improve the bio-fidelity of these models, we propose to identify the mechanical behaviour of bone tissues, and more particularly of the cancellous bone. After scanning cancellous bone samples with micro computed tomography, compression tests have been performed. The inter and intra-individual variabilities have been studied in order to minimise the results dispersions. Numerical models (taking into account the real architecture of this tissue) have been generated from the data coming from μCT in order to study the effects of architectural parameters on the mechanical behaviour of the cancellous bone. The experimental and numerical results show the need to take into account the inter and intra-individual variabilities in order to identify the mechanical behaviour of the trabecular bone. If the relative density could explain the mechanical dispersions observed, the relationship established could not explain the different behaviour observed between various loading directions.

Although initiation criteria have been the subject of many publications, the phenomena associated with the propagation and arrest of brittle cracks have not. To be able to predict the dynamic behaviour of cleavage cracks, we made a series of experiments and associated numerical studies. Tests of crack propagation and arrest were carried out on specimens of two different geometries (Compact Tension and compression ring) made of the 16MND5 ferritic steel of which French nuclear reactor vessels are constructed. The elastic-viscoplastic behaviour of this material was characterised and its nature was taken into account in the numerical simulations. The eXtended Finite Element Method (X-FEM) was developed in CAST3M finite element analysis software to enable fine, effective modelling of crack propagation. Propagation models based on principal stress were studied and it was found that critical cleavage stress depended on loading rate. The use of criteria calibrated for Compact Tension specimens gave excellent results in predictive calculations for similar specimens, and also for compression rings in both mode I and mixed-mode. The speed and path of crack predicted with the numerical simulations were in close agreement with the experimental results.

The model developed to predict the performance of double-row tapered roller bearings (DRTRB) and described in the first part of the paper is now exemplified. For a given example results on the internal load distribution, bearing fatigue life and hear generation are presented and discussed for various operating conditions including the mounting preload. It is revealed that some sliding occurs at the contact between the rollers and the cone that contributes significantly to the total power dissipated within the bearing. It is also shown that an optimum axial compression (or mounting preload) may be found in terms of fatigue life and heat dissipated. As the main conclusion the initial compression between bearing rows was found to play a major role upon the bearing behavior and therefore should be considered carefully for each application. Presented at the 56th Annual Meeting in Orlando, Florida May 20–24, 2001

In the case of SC cut quartz crystal the effects of compression and flexure stress are studied. Some stress-unsensitive areas are pointed out, and a new holdering structure is proposed Etude des effets de compression et de flexion sur un cristal de quartz. Mise en evidence de l'existence de zones d'insensibilite. Proposition d'une nouvelle structure de maintien d'un resonateur a coupe SC