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131.
132.
A review of the development of creep age forming: Experimentation, modelling and applications 总被引:4,自引:0,他引:4
Lihua ZhanJianguo Lin T A Dean 《International Journal of Machine Tools and Manufacture》2011,51(1):1-17
About twenty years ago, the process of Creep Age Forming (CAF) was invented, and since then has been developed for the manufacture of heat treatable aluminium alloy panel components particularly, it has been successfully used for aircraft wing panels. Significant research work has been carried out in recent years and process applications have been expanded. This paper contains a review of recent research and development of this novel forming process. It covers process applications in the aircraft industry and scientific research, including the development of forming tools, experimental studies, materials and process modelling and springback prediction. Some potential future applications and challenges for deeper understanding of this novel process are also discussed. 相似文献
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134.
《Soils and Foundations》2021,61(6):1581-1596
Recent works have shown that delayed events of particle crushing are partially responsible of creep deformation in granular materials, and that Stress Corrosion Cracking promoted by high humidity within particles is the source of this mechanism. A number of experimental studies have focused on creep behaviour of water saturated samples and wetting-deformation after soaking dry material. However, there are few evidences of the effect of varying total suction in time-dependent deformation of partially saturated crushable material, and this mechanism have been rarely considered in constitutive models. The aims of this paper are to present experimental evidence of the effect of total suction on compressibility and creep of sandy sized samples from crushed rock, and to propose a simple one-dimensional elasto-plastic modelling approach based on the enhancement of an existing model. Oedometric compression tests at different total suctions are presented. The results show that compressibility and creep strains increase with both stress and humidity. The model proposed uses a time-dependent hardening law coupling suction with the amount of particle breakage. Based on preliminary calibrations, the model captures the effect of suction and time-dependent behaviour over a large range of total suction. 相似文献
135.
This paper investigates the mechanical deformation and the electrical contact resistance of an electroplated Ni micro-cylinder called micro-insert inserted in an Al thin film. A modified nanoindentation apparatus is used to perform the experiments with 6 μm, 8.5 μm and 12.5 μm diameters micro-inserts having the same 5 μm height. Mechanical deformation of Ni micro-insert and Al film is described at different maximum loads corresponding to an equivalent stress of 0.8 GPa, 1.6 GPa and 3.2 GPa. At equivalent stress less than 1.6 GPa, Ni micro-insert exhibits an elastic deformation while at 3.2 GPa it presents an elastic-plastic deformation with a large amount of compression and penetration into micro-insert foundation. Visco-plastic deformation of Al film is noticed during hold at all maximum loads. Beside, Al creep parameters are extracted using a combined Maxwell/Kelvin-Voigt phenomenological model. Mechanical results are coupled to electrical contact resistance measurement. 相似文献
136.
High‐temperature ferritic alloys are potential candidates as interconnect (IC) materials and spacers due to their low cost and coefficient of thermal expansion (CTE) compatibility with other components for most of the solid oxide fuel cells (SOFCs). However, creep deformation becomes relevant for a material when the operating temperature exceeds or even is less than half of its melting temperature (in degrees of Kelvin). The operating temperatures for most of the SOFCs under development are around 1,073 K. With around 1,800 K of the melting temperature for most stainless steel (SS), possible creep deformation of ferritic IC under the typical cell operating temperature should not be neglected. In this paper, the effects of IC creep behaviour on stack geometry change and the stress redistribution of different cell components are predicted and summarised. The goal of the study is to investigate the performance of the fuel cell stack by obtaining the changes in fuel‐ and air‐channel geometry due to creep of the ferritic SS IC, therefore indicating possible changes in SOFC performance under long‐term operations. The ferritic IC creep model was incorporated into software SOFC‐MP and Mentat‐FC, and finite element analyses (FEAs) were performed to quantify the deformed configuration of the SOFC stack under the long‐term steady‐state operating temperature. It was found that the creep behaviour of the ferritic SS IC contributes to narrowing of both the fuel‐ and the air‐flow channels. In addition, stress re‐distribution of the cell components suggests the need for a compliant sealing material that also relaxes at operating temperature. 相似文献
137.
《International Journal of Hydrogen Energy》2023,48(58):22220-22230
In present paper, effect of holding time at 600 °C during the brazing cooling process on creep life of solid oxide fuel cell (SOFC) with bonded compliant seal (BCS) is investigated by the finite element method. The research indicates that creep crack initiation time in BCS structure increases significantly with the holding time increasing. Compared with that the traditional cooling method during the brazing process, the creep crack initiation time can be prolonged more than twice by the holding time of 150 h with the operating temperature of 600 °C, it increases from 14,949 h to 31,911 h. When the operating temperature is 800 °C, the creep crack initiation time of SOFC can hardly be affected if the holding time exceeds 10 h. Based on the creep damage analysis and considering the cost of the SOFC manufacturing process, it is recommended that the holding time should not be exceeded 300 h if the operating temperature is below 750 °C. And when the operating temperature is 800 °C, the recommended holding time should not be longer than 10 h. The research of the present paper can provide theoretical guidance for the long life manufacturing and reliability operation of SOFC. 相似文献
138.
Recently, there has been considerable interest in studying creep crack growth in creep–brittle materials. For example, the methodologies for assessing creep ductile materials, using fracture mechanics parameters like C* and Ct, have been extended to include creep–brittle materials [1]. This paper begins by examining these recent developments and outlines the difficulties in adopting these developments. An alternative approach is then proposed. This new approach leads from recent work proposed by the authors [2], where a strain based failure assessment diagram (SB-FAD) is used. Experimental results from a series of tests on a simulated heat affected zone of a low alloy steel are explored. The application of the methodology for assessing the initiation and growth of a defect in a creep–brittle material is also demonstrated. 相似文献
139.
The heat corrections (HC) used in two multiple heat stress rupture correlations, one from Manson and Park (MP) and the other from the present authors (RSR), are compared as to their efficacies in correlating multiple-heat stress rupture data for a 0.5Mo–0.15C steel, a 9Cr–1Mo steel, two grades of 2.25Cr–1Mo steels, and two grades of AISI type 316 stainless steels. Two types of fits of isothermal multi-heat data were carried out; in one case the curvatures of the isothermal plots of log(rupture life) against log(stress) were restricted to be non-positive (to be consistent with the behaviour expected from model-based considerations), while in the other case no restrictions were imposed on the possible curvature variations, as is common in the creep literature. Irrespective of whether the curvature restrictions were imposed or not, the HC adopted in RSR proved superior to that in MP for all these materials, though the extent of superiority is apparently dependent on the material. Interestingly, in most cases, the imposition of the curvature restrictions only marginally affected the quality of fit, though this may enhance the regime of the correlation that can be used for extrapolation. 相似文献
140.