Characteristics of strength and plasticity of tungsten and tungsten-base alloys

Bukhanovskii, V. V.; Golovin, S. A.; Kharchenko, V. K.; Kravchenko, V. S.; Nikolskii, V. N.; Ol'shanskii, A. B.

doi:10.1007/bf00791960

Cited by 8 publications

(4 citation statements)

References 3 publications

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“…The results of fractographic examinations, which establish similarity of the PM tungsten fracture modes under conditions of high-temperature creep and static tests, confirm the validity of the hypotheses taken as the basis for our further considerations [10,11]. The similarity of the mechanisms of plastic deformation under active tension and deformation at the stage of steady-state creep for metallic materials was also noted in [4,14], where it was mentioned that under conditions of high-temperature uniform tension, the strain rate is equivalent to the steady-state creep rate.…”

Section: Introductionsupporting

confidence: 65%

“…The amount of accumulated experimental data on the mechanical properties of tungsten produced by PM technique [10][11][12][13] makes it possible to analyze them and establish correlation dependences between the characteristics of its short-term and long-term static strength and creep resistance. The experimental results considered refer to a high-temperature region (above 0 5…”

Section: Introductionmentioning

confidence: 99%

“…presents experimental data[10][11][12][13] on short-term strength of commercially pure PM tungsten (99.97 wt.% W) in the temperature range from 1770 to 2770 Ê, which corresponds to~(0.5-0.8)T melt , in the form of temperature dependences of the ultimate strength R m and the offset yield stress R p0 2 . .…”

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confidence: 99%

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Correlation Dependences between Short-Term/Long-Term Static Strength Characteristics and Creep Resistance of Tungsten at High Temperatures

2005

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Experimental data on high-temperature mechanical properties under uniaxial tension of commercially pure tungsten obtained by powder metallurgy have been analyzed. It has been found that for powder metallurgy tungsten in the high-temperature region~, (0.5 0.8) − T melt there is a close correlation among the characteristics of short-and long-term static strengths and creep resistance, which are described by a single functional relation. Introduction.The progress in a number of branches of modern engineering is related to the use of refractory metals and alloys, which can ensure strength of components and structural elements operating under conditions of extremely high temperatures (up to 2300-3300 K) and mechanical loads. Tungsten and tungsten-based alloys have the most unique range of physico-mechanical characteristics including heat resistance [1][2][3].In addition to short-term strength, the characteristics of long-term static strength and creep are the most important factors characterizing serviceability of metals at high temperatures. Complete experimental evaluation of such characteristics for refractory materials presents great difficulties and is unrealistic in many cases.It is known that temperature dependences of various mechanical characteristics that determine the resistance of metallic materials to deformation are qualitatively similar. Under short-term and long-term static loading, there are correlation dependences between strength characteristics of metals and alloys, which can be described by certain analytical expressions based on both empirical and physically justified approaches. They are undoubtedly of scientific and practical interest, because they make it possible to evaluate heat-resistance characteristics of advanced structural materials at minimum cost [4,5].In the present study, based on the analysis of experimental data obtained earlier, a generalized correlation dependence has been established between the characteristics of high-temperature short-term and long-term static strength and creep resistance of commercially pure tungsten produced by powder metallurgy (PM) technique.Theoretical Background. On the basis of numerous experiments it has been found that temperature dependence of any mechanical characteristics, which determine the resistance of metallic materials to deformation, is described quantitatively by the following equation [4]:

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Section: Introductionsupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

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Correlation Dependences between Short-Term/Long-Term Static Strength Characteristics and Creep Resistance of Tungsten at High Temperatures

2005

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“…The heat transfer capability of the slow wave structure is one of the most important factors that limit the output power capability of helix TWT's. Tube designers must be able to examine thermal behavior of the circuit, especially the dielectric support rods which play a critical role in removing heat from the helix [4]. By employing finite element techniques, tube designers can be able to estimate the feasibility of a projected design by predicting influences of various physical and geometrical parameters of @e interaction circuit on helix temperatures for various power dissipations.…”

Section: O N C L U S I O N Smentioning

confidence: 99%

Thermal-structural reliability assessment of helix TWT interaction circuit using finite element analysis

Rocci¹

Proceedings of the IEEE 1993 National Aerospace and Electronics Conference-Naecon 1993

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Finite element analysis (FEA) techniques were used to assess the mechanical performance due to thermal loading of a high power, wide band, helix traveling wave tube's interaction (slow wave) circuit. This work was sponsored in part by the Air Force Office of Scientific Research. A steady state heat transfer analysis was performed using calculated heat dissipations and boundary temperatures that were obtained through data supplied by the TWT's manufacturer. Although the absolute amount of power dissipated by the interaction circuit is relatively small compared to the total heat dissipation of the TWT, it is locally concentrated over small areas which creates large heat fluxes. The resulting temperatures from this analysis were then used as loading conditions in a linear static analysis of a smaller model which represents a 12 turn section of the circuit. The failure modes investigated in this study were cracking of the helix tape and fracture of the support rods due to excessive thermal stresses. Cracking of the helix tape would cause an opencircuit to occur while fracture of the support rods could cause small mechanical perturbations in the slow wave structure which may reflect the RF signal. Both cases could possibly lead to electrical failure of the TWT. Static stress analysis of the attenuation section indicated that the stress levels in the helix and support rods due to this particular temperature gradient were within acceptable limits and would not fracture if these components were free of initial cracks or flaws. Stresses through the helix were sufficient to nucleate cracks, however the length of these cracks would be minute and would not affect the useful life of the helix.

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