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151.
The ferritic steel 16Mo3 is commonly used for heat exchangers and steam generators. The temperature loading conditions for these applications range typically from 200 to 500°C. For a basic characterization of the steel 16Mo3, the properties were determined by means of tensile tests with different strain rates. At 200 and 300°C, a negative strain‐rate sensitivity was observed which is due to dynamic strain ageing (Portevin–LeChâtelier effect). To characterize the low cycle fatigue (LCF) behavior of this steel, isothermal strain‐controlled LCF tests were carried out at 200 and 500°C at different strain amplitudes. The cyclic stress response curves are showing principally different courses at the investigated temperatures. The stress relaxation behavior was obtained by cyclic load enhancement tests at various strain amplitudes with dwell times of 30 and 120 s. 相似文献
152.
The deformation mechanisms of high‐alloyed cast austenitic steels with 16% of chromium, 6% of manganese, and a nickel content of 3–9% were investigated by in situ and ex situ scanning electron microscopy. The austenite stability and the stacking fault energy were influenced by variation of the chemical composition as well as by changing deformation temperature (room temperature; RT and 100°C). The study shows that both an increase in austenite stability and stacking fault energy yield a significant change in the deformation mechanisms. Both increase of nickel content and increase in deformation temperature reduce the intensity of the martensitic phase transformation. Thus, the steel with low nickel content shows at RT pronounced formation of α′‐martensite. The steel with the highest nickel content, however, shows pronounced twinning. 相似文献
153.
Qiuliang Huang Olena Volkova Horst Biermann Javad Mola 《Metallurgical and Materials Transactions A》2017,48(12):5771-5777
The dissolution of Cr-rich carbides formed in the martensitic constituent of a 13 pct Cr stainless steel was studied by dilatometry and correlative electron channeling contrast examinations. The dissolution of carbides subsequent to the martensite reversion to austenite was associated with a net volume expansion which in turn increased the dilatometry-based apparent coefficient of thermal expansion (CTEa) during continuous heating. The effects of carbides fraction and size on the CTEa variations during carbides dissolution are discussed. 相似文献
154.
E. Özkaya E. Bayraktar S. Turek D. Biermann 《Materialwissenschaft und Werkstofftechnik》2013,44(6):577-585
This study concerns the determination of the significant factors for an innovative deburring process: low pressure abrasive water‐jet blasting. The abrasive medium aluminum oxide (Al2O3) is classified according to the individual characteristics of different grain sizes. Then, the particle behavior in the air jet is analyzed with an optical measuring method, Particle Image Velocimetry (PIV); the velocity profile and the particle distribution of the dispersed system are obtained. Computational Fluid Dynamics (CFD) simulations were verified by comparing the experimental and numerical results, and the velocity range for the abrasive particles has been specified. 相似文献
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157.
Alexander Schmiedel Sebastian Henkel Thomas Kirste Roman Morgenstern Anja Weidner Horst Biermann 《Fatigue & Fracture of Engineering Materials & Structures》2020,43(10):2455-2475
The fatigue life of cast steel G42CrMo4 in two different heat treatment conditions was investigated at room temperature (RT), 473 K and 773 K up to the range of very high cycle fatigue (VHCF), that is, 109 cycles. The fatigue life is determined by casting defects, the hardness of the steel matrix and by temperature. Fatigue life data were discussed in correlation with crack‐initiating defects analysed on fracture surfaces. The SN curves obtained at RT and at 473 K show a large scatter. However, the SN curve at 773 K exhibits a larger slope parameter and a significantly reduced scatter. It is shown that the fatigue behaviour of the cast steel G42CrMo4 changes from 473 to 773 K in the range of VHCF. The fatigue lives of the specimens tested at 773 K were described with a crack growth model. 相似文献
158.
Norbert Biermann 《Cryptologia》2018,42(5):381-407
In his book, Noui et singolari modi di cifrare, Giouan Battista Bellaso presented to his readers three challenge ciphertexts. Two of them are based on a polyalphabetic cipher with a mixed primary reciprocal alphabet and a long key, whereas the third one uses four independent homophonic substitution alphabets that change after each word. A successful approach to solving these ciphers, to which Bellaso gave the name “terzo modo” and “quarto modo,” performs a simulated annealing attack directly on the primary alphabet, respectively the four homophonic alphabets at once. This article focuses on the various applied fitness functions. The solutions for the ciphertexts are given and finally discussed, with a view toward the possibility of a hidden message within the plaintexts. 相似文献
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160.
High-performance Ni- and Ti-based materials are generally difficult to machine. Drilling in particular is highly demanding for the applied tools due to challenging thermal stress. This paper describes a novel modification for twist drills which significantly improves the cooling and lubrication of the main and secondary cutting edges and leads to an enhancement in process productivity. Within the scope of this work, the achievable improvements with regard to wear progress, cutting edge temperature and cutting fluid flow when machining Inconel 718 are analysed. The solution developed could also prove its efficiency in the machining of titanium-based alloy Ti6Al4V. 相似文献