Fatigue Life of a SG Cast Iron under Real Loading Spectra: Effect of the Correlation Factor Between Bending and Torsion

This paper deals with the effect on life of the desynchronism between two variable amplitude load sequences in combined bending and torsion. Experiments were carried out on smooth specimens made of the EN-GJS800-2 cast iron. The comparison between experimental lives and predicted ones with the following fatigue life calculation methods is presented: Smith-Watson-Topper, Fatemi and Socie (method proposed by Bannantine), Wang and Brown, Socie's proposal for high cycle fatigue, and Morel. If the scatter of experiments is considered, these experiments show a low effect of the correlation factor on life. All the simulated fatigue life calculation methods give good results for proportional loads, but their predictions are not good for non-proportional loads. Morel’s proposal seems to be the best to predict life of the tested material with our non-proportional fatigue test conditions

A volumetric energy based high cycle multiaxial fatigue citerion

A reliable design of industrial parts against high-cycle multiaxial fatigue requires a fatigue criterion capable of predicting both the stress gradient and the load-type effects. These effects are very important in the transfer of fatigue data from specimen to component. By using the concept of volume influencing fatigue crack initiation proposed by Palin-Luc and Lasserre with an energy based approach, a new criterion is presented. Based on the strain-work density given to the material, this proposal is usable whatever the constant amplitude loading is: in and out-of-phase combined loadings, with or without mean stress. Its predictions are compared both with a total of 38 experiments on four materials (a mild steel, two high strength steels and a spheroidal graphite cast iron) and with the predictions of local criteria (Crossland, Dang Van, Papadopoulos and Morel). The comparison shows that the predictions of the volumetric proposal are very good and less scattered than those of the local approaches, especially for loadings with mean stresses or under non-proportional loadings

Fatigue Life of a SG Cast Iron under Real Loading Spectra: Effect of the Correlation Factor Between Bending and Torsion

This paper deals with the effect on life of the desynchronism between two variable amplitude load sequences in combined bending and torsion. Experiments were carried out on smooth specimens made of the EN-GJS800-2 cast iron. The comparison between experimental lives and predicted ones with the following fatigue life calculation methods is presented: Smith-Watson-Topper, Fatemi and Socie (method proposed by Bannantine), Wang and Brown, Socie's proposal for high cycle fatigue, and Morel. If the scatter of experiments is considered, these experiments show a low effect of the correlation factor on life. All the simulated fatigue life calculation methods give good results for proportional loads, but their predictions are not good for non-proportional loads. Morel’s proposal seems to be the best to predict life of the tested material with our non-proportional fatigue test conditions

A volumetric energy based high cycle multiaxial fatigue citerion

A reliable design of industrial parts against high-cycle multiaxial fatigue requires a fatigue criterion capable of predicting both the stress gradient and the load-type effects. These effects are very important in the transfer of fatigue data from specimen to component. By using the concept of volume influencing fatigue crack initiation proposed by Palin-Luc and Lasserre with an energy based approach, a new criterion is presented. Based on the strain-work density given to the material, this proposal is usable whatever the constant amplitude loading is: in and out-of-phase combined loadings, with or without mean stress. Its predictions are compared both with a total of 38 experiments on four materials (a mild steel, two high strength steels and a spheroidal graphite cast iron) and with the predictions of local criteria (Crossland, Dang Van, Papadopoulos and Morel). The comparison shows that the predictions of the volumetric proposal are very good and less scattered than those of the local approaches, especially for loadings with mean stresses or under non-proportional loadings

Fatigue life under non-Gaussian random loading from various models

Fatigue test results on the 10HNAP steel under constant amplitude and random loading with non-Gaussian probability distribution function, zero mean value and wide-band frequency spectrum have been used to compare the life time estimation of the models proposed by Bannantine, Fatemi–Socie, Socie, Wang–Brown, Morel and Łagoda–Macha. Except the Morel proposal which accumulates damage step by step with a proper ethodology, all the other models use a cycle counting method. The rainflow algorithm is used to extract cycles from random histories of damage parameters in time domain. In the last model, where a strain energy density parameter is employed, additionally spectral method is evaluated for fatigue life calculation in the frequency domain. The best and very similar results of fatigue life assessment have been obtained using the models proposed by Socie and by Łagoda–Macha, both in time and frequency domains for the last one.With the support of the Commission of the European Communities under the FP5, GROWTH Programme, contract No. G1MA-CT-2002-04058 (CESTI)

Fatigue life under non-Gaussian random loading from various models

Fatigue test results on the 10HNAP steel under constant amplitude and random loading with non-Gaussian probability distribution function, zero mean value and wide-band frequency spectrum have been used to compare the life time estimation of the models proposed by Bannantine, Fatemi–Socie, Socie, Wang–Brown, Morel and Łagoda–Macha. Except the Morel proposal which accumulates damage step by step with a proper ethodology, all the other models use a cycle counting method. The rainflow algorithm is used to extract cycles from random histories of damage parameters in time domain. In the last model, where a strain energy density parameter is employed, additionally spectral method is evaluated for fatigue life calculation in the frequency domain. The best and very similar results of fatigue life assessment have been obtained using the models proposed by Socie and by Łagoda–Macha, both in time and frequency domains for the last one.With the support of the Commission of the European Communities under the FP5, GROWTH Programme, contract No. G1MA-CT-2002-04058 (CESTI)

Application industrielle de prétraitements pour l'obtention de nanofibrilles de cellulose haute qualité

Le développement de matériaux biosourcés possédant un large éventail de propriétés est devenu une préoccupation majeure dans notre société actuelle, pour tendre vers une bioéconomie durable. Dans ce contexte, les nanofibrilles de cellulose (CNF) sont très prometteuses, de par leurs propriétés mécaniques, optiques, rhéologiques et barrières intéressantes. En revanche, plusieurs verrous technologiques freinent encore la rentabilité de leur production à l’échelle industrielle, tels que les problèmes de procédé ou de toxicité liés aux prétraitements de la cellulose, et la forte consommation énergétique des procédés de fibrillation mécanique. Ce projet vise au développement de prétraitements innovants et à l’optimisation de plusieurs procédés de fibrillation mécanique, avec pour objectif de produire à l’échelle industrielle des CNF de haute qualité. Dans un premier temps, trois prétraitements ont été étudiés, impliquant un traitement alcalin et enzymatique couplé, l’adsorption d’un polyélectrolyte, et l’hydrolyse enzymatique in situ à fort taux de matière sèche pendant la fibrillation par extrusion bi-vis. Ensuite, un procédé de raffinage à disque a été optimisé pour la production de CNF, en vue de l’implémentation de ces prétraitements à l’échelle pilote. Plusieurs essais industriels avec une ligne de raffinage spécifique au papier calque ont souligné la pertinence de ce procédé pour la production de CNF en grande quantité, menant à une réduction significative de la consommation énergétique comparée à des procédés conventionnels. Enfin, le raffinage à disque a été combiné respectivement avec l’extrusion bi-vis, le broyage ultra-fin et l’homogénéisation. Cette stratégie a permis de dépasser la limitation de la qualité de CNF rencontrée avec l’utilisation du raffinage seul. Les résultats de ce projet contribuent à la connaissance des prétraitements et procédés pour la production de CNF, et sont un pas vers leur production efficace à l’échelle industrielle.The development of biobased materials with a wide range of properties has become a key issue in today’s society, to move towards a durable bioeconomy. In this context, cellulose nanofibrils (CNF) are very promising, due to their interesting mechanical, optical, rheological and barrier properties. However, several technological challenges still restrain their cost-efficient production at the industrial scale, such as the process or toxicity issues of the cellulose pretreatments, and the high energy consumption of the mechanical fibrillation processes. This project aims at developing innovative pretreatments and optimize several mechanical fibrillation processes, with an objective of producing high quality CNF at the industrial scale. First, three pretreatments were studied, involving a coupled alkaline and enzymatic treatment, the adsorption of a polyelectrolyte, and in situ enzymatic hydrolysis at high solid content during fibrillation by twin-screw extrusion. Then, a disk refining process was optimized for CNF production, for the implementation of these pretreatments at the pilot scale. Several industrial trials with a specific tracing paper refining line also underlined the relevance of this process for large scale CNF production, leading to a significant decrease of energy consumption compared to conventional processes. Finally, disk refining was combined with twin-screw extrusion, ultra-fine grinding and homogenization, respectively. This strategy enabled to overcome the limitation of CNF quality encountered with the use of refining alone. The results of this project contribute to the knowledge on pretreatments and processes for CNF production, and are a step towards their efficient production at industrial scale

Optimisation des conditions d'epitaxie pour la croissance de puits quantiques InAs/InP par la methode aux hydrures

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 83298 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc