ABSTRACT The failure initiation of a brazed structure made of Silicon Carbide components is analy... more ABSTRACT The failure initiation of a brazed structure made of Silicon Carbide components is analysed by means of a two-scale analysis and a twofold failure criterion using both a maximum released energy and a maximum tensile stress conditions. In a first step, two asymptotic expansions are settled to describe the perturbation caused by the emergence of the thin solder layer on the free edge surface of the structure, at the macro and micro levels. The resulting far field evidences a logarithmic term. This is mainly due to different elastic properties of the two materials leading to a conflicting necking effect. In a second step, the failure criterion is established; the two conditions lead to two branches depending on the thickness of the solder layer, one is governed by the energy condition and the other by the stress condition. Predictions agree almost well with experiments carried out at room temperature on brazed specimens of SiC with different Silicon based solders.
ABSTRACT Hydrogen storage in metal compounds has been actively studied as a way to store energy b... more ABSTRACT Hydrogen storage in metal compounds has been actively studied as a way to store energy by G. Sandrock (1999) and M. Latroche (2004) [1,2]. But even if the importance of studying the mechanical behaviour of hydride compounds has been shown early in M. Kawamura et al. (1981) [3] there is still a lack of phenomenological or predictive models for handling this difficulty. In this paper, the use of Discrete Element Modelling (DEM) is investigated as a way to improve our understanding of the mechanical behaviour of hydrides absorbing and desorbing hydrogen, which is also called the hydride breathing phenomenon, and to develop better macroscopic models in the future. Starting from elementary mechanical characterisation of the hydride powder, from matrix compaction dedicated to determine the powder compressibility, to rotating drum, dedicated to determine the flowing ability of the powder, the parameters of the Discrete Element Model are adjusted, and the model is then confronted to the results experimentally obtained on a volume of hydride breathing within an instrumented elementary cell. The method is developed on a TiVCr BCC alloy.
ABSTRACT When a hydride material absorbs hydrogen, the phase change occurring is accompanied by a... more ABSTRACT When a hydride material absorbs hydrogen, the phase change occurring is accompanied by a volume change of the material. Very often, the material is of granular nature, and the problem boils down to the study of a powder material swelling and shrinking – which is referred to as the hydride breathing – in a close container.
ABSTRACT In recent years, material development for ITER blanket components has been fervent; yet,... more ABSTRACT In recent years, material development for ITER blanket components has been fervent; yet, a lack of materials data has been identified by the ITER International Organization (IO) and other ITER parties. Therefore, extensive work on assessment of materials data and qualification of the materials with all the relevant interfaces (joints) has been performed to ensure that requirements are fulfilled for the ITER operational conditions with acceptable margins for the foreseen lifetime of the ITER project. This paper will provide an overview of this qualification program with examples of recent results within the scope of the European contribution of blanket components to ITER. Ongoing actions to achieve a comprehensive understanding of the three main materials, beryllium, CuCrZr and stainless steel grade 316L(N)-IG, and their joints included in the blankets are discussed.
Modelling and computer simulation have been developed in order to assist the hot isostatic pressi... more Modelling and computer simulation have been developed in order to assist the hot isostatic pressing (HIP) fabrication of a shield prototype for the ITER blanket. Problems such as global bending of the whole part and deformations of tubes in their powder bed are addressed. It is important that the part does not bend too much. It is important as well
... Most of the studies come from the late Eighties and were realised by Rahaman et al. [23, 24, ... more ... Most of the studies come from the late Eighties and were realised by Rahaman et al. [23, 24, 25, 26, 27 and 28] and Raj et al. [29, 30, 31 and 32]. Rahaman et al. ... The most recent paper reporting viscosity results was published in 1990 [28]. Raj et al. ...
ABSTRACT The failure initiation of a brazed structure made of Silicon Carbide components is analy... more ABSTRACT The failure initiation of a brazed structure made of Silicon Carbide components is analysed by means of a two-scale analysis and a twofold failure criterion using both a maximum released energy and a maximum tensile stress conditions. In a first step, two asymptotic expansions are settled to describe the perturbation caused by the emergence of the thin solder layer on the free edge surface of the structure, at the macro and micro levels. The resulting far field evidences a logarithmic term. This is mainly due to different elastic properties of the two materials leading to a conflicting necking effect. In a second step, the failure criterion is established; the two conditions lead to two branches depending on the thickness of the solder layer, one is governed by the energy condition and the other by the stress condition. Predictions agree almost well with experiments carried out at room temperature on brazed specimens of SiC with different Silicon based solders.
ABSTRACT Hydrogen storage in metal compounds has been actively studied as a way to store energy b... more ABSTRACT Hydrogen storage in metal compounds has been actively studied as a way to store energy by G. Sandrock (1999) and M. Latroche (2004) [1,2]. But even if the importance of studying the mechanical behaviour of hydride compounds has been shown early in M. Kawamura et al. (1981) [3] there is still a lack of phenomenological or predictive models for handling this difficulty. In this paper, the use of Discrete Element Modelling (DEM) is investigated as a way to improve our understanding of the mechanical behaviour of hydrides absorbing and desorbing hydrogen, which is also called the hydride breathing phenomenon, and to develop better macroscopic models in the future. Starting from elementary mechanical characterisation of the hydride powder, from matrix compaction dedicated to determine the powder compressibility, to rotating drum, dedicated to determine the flowing ability of the powder, the parameters of the Discrete Element Model are adjusted, and the model is then confronted to the results experimentally obtained on a volume of hydride breathing within an instrumented elementary cell. The method is developed on a TiVCr BCC alloy.
ABSTRACT When a hydride material absorbs hydrogen, the phase change occurring is accompanied by a... more ABSTRACT When a hydride material absorbs hydrogen, the phase change occurring is accompanied by a volume change of the material. Very often, the material is of granular nature, and the problem boils down to the study of a powder material swelling and shrinking – which is referred to as the hydride breathing – in a close container.
ABSTRACT In recent years, material development for ITER blanket components has been fervent; yet,... more ABSTRACT In recent years, material development for ITER blanket components has been fervent; yet, a lack of materials data has been identified by the ITER International Organization (IO) and other ITER parties. Therefore, extensive work on assessment of materials data and qualification of the materials with all the relevant interfaces (joints) has been performed to ensure that requirements are fulfilled for the ITER operational conditions with acceptable margins for the foreseen lifetime of the ITER project. This paper will provide an overview of this qualification program with examples of recent results within the scope of the European contribution of blanket components to ITER. Ongoing actions to achieve a comprehensive understanding of the three main materials, beryllium, CuCrZr and stainless steel grade 316L(N)-IG, and their joints included in the blankets are discussed.
Modelling and computer simulation have been developed in order to assist the hot isostatic pressi... more Modelling and computer simulation have been developed in order to assist the hot isostatic pressing (HIP) fabrication of a shield prototype for the ITER blanket. Problems such as global bending of the whole part and deformations of tubes in their powder bed are addressed. It is important that the part does not bend too much. It is important as well
... Most of the studies come from the late Eighties and were realised by Rahaman et al. [23, 24, ... more ... Most of the studies come from the late Eighties and were realised by Rahaman et al. [23, 24, 25, 26, 27 and 28] and Raj et al. [29, 30, 31 and 32]. Rahaman et al. ... The most recent paper reporting viscosity results was published in 1990 [28]. Raj et al. ...
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