Search

Plasticized poly(vinyl chloride) (PPVC) is widely used in the automotive industry in the design of structural parts for crashworthiness applications. Thus, it is necessary to study and understand the influence of the mechanical response and mechanical properties of PPVC over a wide range of strain rate, from quasi-static to dynamic loadings. The process is also investigated using different sample thicknesses. In this work, the strain rate effect of a new PPVC is investigated over a wide range of strain rates at three temperatures and for three thicknesses. A modelling of the yield stress is also proposed. The numerical prediction is in good agreement with the experimental results.

During the last decades, the part of polymeric materials considerably increased in automotive and packaging applications. However, their mechanical behaviour is difficult to predict due to a strong sensitivity to the strain rate and the temperature. Numerous theories and models were developed in order to understand and model their complex mechanical behaviour. The one proposed by Richeton et al. [Int. J. Solids Struct. 44, 7938 (2007)] seems particularly suitable since several material parameters possess a strain rate and temperature sensitivity. The aim of this study is to implement the proposed constitutive model in a commercial finite element software by writing a user material subroutine. The implementation of the model was verified on a compressive test. Next a normal impact test was simulated in order to validate the predictive capabilities of the model. A good agreement is found between the FE predictions and the experimental results taken from the literature.

L'analyse des comportements mécaniques, biologiques et physiques aux interfaces de biomatériaux médicaux ayant vocation à évoluer dans la sphère orale est particulièrement importante. En effet, des influences cliniques diverses, en termes de vieillissement des matériaux et de protection des éléments dentaires et péri-dentaires peuvent être constatées. Les alliages à mémoire de forme Nickel Titane sont couramment utilisés dans la fabrication d'instruments d'odontologie. Dans cette étude, deux systèmes de limes endodontiques ont été étudiés. Bien qu'ayant des compositions chimiques similaires, leurs structures différentes conduisent empiriquement à des modes de rupture distincts. En effet, certaines limes peuvent être utilisées plusieurs fois, alors que d'autres limes provenant d'un fournisseur différent peuvent casser dès la première utilisation, sans prévention possible. Ce travail cherche à comprendre cette différence à travers une étude couplée mécanique/métallurgique afin de corréler le comportement en traction et en fatigue avec l'état de surface des limes, corrélés à leurs procédés d'élaboration. L'étude métallurgique a d'abord été focalisée sur une comparaison des états de surface, avant et après des traitements de mordançage et/ou de polissage électrolytique (Fig. 1). L'étude mécanique a débuté par l'identification expérimentale des matériaux utilisés pour la fabrication de ces deux types de limes dentaires. Ces matériaux ont été fournis sous forme de fils. La littérature met en évidence la sensibilité du comportement de ces alliages à la vitesse de déformation. Deux vitesses de sollicitations sur trois fils de diamètre 0,6 mm ; 0,8 mm et 1 mm ont été testés. Des essais de traction (Fig. 2) et de fatigue (Fig. 3) ont été réalisés sur ces trois diamètres. Les faciès de rupture avant et après essais ont aussi été analysés.

Hydatid cyst disease is a health problem in some developing countries occurring in groups with permanent contact with dogs. It is a parasitic disease caused by Echinococcus Granulosus. The liver is the most common organ infected. If not treated appropriately; it may lead to developing life-threatening complications. Its rupture into bile ducts is the most frequent one, while hepatopulmonary fistula is a rare complication. We discuss the case of a child presenting those 2 complications as we emphasize the importance of early diagnosis and the role of the radiologist.

Relatively rare, Rasmussen encephalitis is a chronic inflammatory disease conditioning a single cerebral hemisphere. It is a progressive pathology with different stages clinically and on MRI. Therefore, imaging has an important role in evoking the diagnosis and also excluding other possible etiologies. We report a case of Rasmussen encephalitis with 2 different stages on MRI and also provide a review of the role of imaging in diagnostic criteria, differential diagnoses, and stages of this pathology.

Summary Augmented reality could help the identification of nerve structures in brachial plexus surgery. The goal of this study was to determine which law of mechanical behavior was more adapted by comparing the results of Hooke's isotropic linear elastic law to those of Ogden's isotropic hyperelastic law, applied to a biomechanical model of the brachial plexus. A model of finite elements was created using the ABAQUS ® from a 3D model of the brachial plexus acquired by segmentation and meshing of MRI images at 0°, 45° and 135° of shoulder abduction of a healthy subject. The offset between the reconstructed model and the deformed model was evaluated quantitatively by the Hausdorff distance and qualitatively by the identification of 3 anatomical landmarks. In every case the Hausdorff distance was shorter with Ogden's law compared to Hooke's law. On a qualitative aspect, the model deformed by Ogden's law followed the concavity of the reconstructed model whereas the model deformed by Hooke's law remained convex. In conclusion, the results of this study demonstrate that the behavior of Ogden's isotropic hyperelastic mechanical model was more adapted to the modeling of the deformations of the brachial plexus. [ABSTRACT FROM AUTHOR]

Dimer fatty acid-based polyamide (DAPA) was reinforced with cellulose fibers (CF) from 5 to 15 wt%. The mechanical behaviors in terms of dynamic responses were examined by dynamic mechanical analysis and split Hopkinson pressure bars at various temperatures and strain rates. Both DAPA matrix and DAPAC biocomposites showed fiber concentration, temperatures, and strain rates sensibilities. A constitutive elasto-viscoplastic model was developed to predict the finite deformation response for these materials. In this, to account for strain rate, temperature and cellulose concentration effects in elastic behavior, a new formulation of statistical model of Richeton was proposed. A modified cooperative model, based on the recognition of the effective activation energy and volume, was used for the prediction of the composites yield stress. Eight-chain model was also used to capture the large stretch hyperelastic behavior for both DAPA and DAPAC. The constitutive model predictions were found to be in good agreement with the experimental data. POLYM. ENG. SCI., 57:95-104, 2017. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In this paper, the mechanical response of two composites-based polypropylene (PP) is studied. High strain rate tests as well as quasi-static uniaxial tests were performed. Dynamic loadings were carried out using the Split Hopkinson Pressure Bar. Materials used consist of an unfilled high-impact PP (hiPP) and a talc-filled hiPP. For each of these two materials, the recycling effects on the stress-strain response for both quasi-static and dynamic loading were studied. The degradation of the mechanical response due to recycling is then characterised for a wide range of loading rates for both materials. Scanning electron microscopy analyses have been achieved in order to quantify recycling and strain rate effects and also to correlate them with the microstructure evolution for a better understanding of the mechanisms involved in the recycling process and in the dynamic loading. This study has led to a preliminary understanding of the recycling effects, particularly for impact loadings. [ABSTRACT FROM AUTHOR]

The article provides information on the surgical treatment of collateral nerves. Topics include the dissection of the nerves, the tensile strength of the nerve, and the use of a pycnometer. The article also discusses the need for nerve studies, the use of Young's Modulus, and the linear regression of the nerve.

The article presents a study aimed to characterize the mechanical properties of human digital collateral nerves to look for a correlation with density as an intrinsic property of materials. Topics discussed include Injuries to digital collateral nerves after hand trauma; surgical treatment of collateral nerves; and construction of human digital collateral nerve specific modulus.

In order to investigate the dynamic behaviour of polypropylene based organoclay nanocomposite, the polypropylene matrix and a master batch of polypropylene modified anhydrid maleic were mixed by means of melt mixing technique. The experimental characterization was performed by using split Hopkinson pressure bars (SHPB), at different strain rates and temperatures. A significant increase of the yield stress of nanocomposite was shown with the present of organoclay, comparing to neat PP. A three-phase approach based on the micromechanical formulation of the cooperative model is proposed to model the yield behaviour of the polymer nanocomposite. Our proposed approach accounts for strain rate and temperature effects as well as the organoclay exfoliation effect. The predictions of models for the nanocomposite yield behaviour showed a good agreement with experimental data.