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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 44-46 (June 2008), p. 765-772 
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The glass-to-metal seals are usually used in the solar thermal power (STP) and electronicdevices. However, the requirement of mechanical properties in the STP is much higher than that ofelectronic devices, because the glass-to-metal joints used in the STP need to have anti-fatigueperformance in adition to higher static tensile strength. Under the repeated fluctuating loads, damageand failures of glass-to-metal seals in the STP often lead to serious consequences. Therefore, analysisof damage evolution and fracture behavior of glass-to-metal diffusion welded joints was performed inthis paper. Firstly, the finite element (FE) model of glass-to-metal welded joints was established inaccordance with the STP welded structures. And damage simulation was carried out by the FEsoftware ABAQUS. Also, the work illustrates the modeling of damage in terms of traction versusseparation to simulate crack propagation and introduces the use of traction-separation law as adamage initiation and evolution criteria. The microgram of damage distribution in the glass side nearthe interface could be characterized by Scanning Electron Microscope (SEM), which was comparedwith predictions obtained by finite element method (FEM) analysis. As result, the damage criteria onthe lap joints in conjunction with FM analysis were used to optimize the glass-to-metal diffusionwelding technology. The above results provide the basis of design against damage and reliableestimation of glass-to-metal seals
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 575-578 (Apr. 2008), p. 666-671 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The glass-to-metal seals are widely used in the solar thermal power. When a glass-to-metalseal is cooled in the process of diffusion welding, the residual stresses are generated due to differentthermal contraction between the two materials. The residual stresses built up along the interface nearthe end of the seal can induce welded joints to crack and decrease the fatigue intensity of the weldedjoints and thus are of technical importance. In order to obtain the residual stresses existed in thediffusion welded joints, the glass-to-metal vacuum diffusion sealing process were simulated by usingfinite element software ABAQUS. Furthermore, the influences of temperature, time, vacuum, andseal pressure on the strength of the glass-to-metal diffusion welding were analyzed. The optimizationof the diffusion welding process parameter based on the simulation of the residual stress and analysisof the micro-structure and the macro-mechanical performance of the diffusion welded seals wascarried out. The distribution of residual stress on the surface of the glass-to-metal joint caused bywelding is measured by X-ray diffraction method, and compared with the result of the numericalsimulation to prove the validation of the finite element model
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 575-578 (Apr. 2008), p. 672-677 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: High residual tensile stress is an important factor contributing to stress corrosion cracking(SCC). Shot peening can impose compressive stresses on the surface of welded joints that negatethe tensile stresses to enhance the SCC resistance of welded joints. In the present work, thedistribution of residual stress caused by welding is measured by X-ray diffraction method. Themaximum stress in the weld is close to the yield strength of AISI 304 stainless steel, and the stressesare negative at both ends of the weld and far from the weld. The X-ray method is also used tomeasure stress caused by shot-peening. The results show that the higher the peening coverage, thehigher the residual compressive stresses in the surface of weldments. While under the samecondition, the residual compressive stresses induced by glass beads shot-peening are larger thanthose by cast steel shots. Temperature and stress fields of welding are simulated by using ABAQUScodes. The 3-D solid elements are used in FEM. Temperature depending on material properties aswell as the convection and radiation as boundary conditions are considered. The 3-D linearreduced-integration elements are used to simulate the shot peening process. The results ofsimulation have a good agreement with experimental data. All unpeened and peened weldments areimmersed in boiling 42% magnesium chloride solution during SCC test. Unpeened specimens crackafter immersion for 6 hours. The steel-peened specimens with 50% coverage crack after 310 hours,while the steel-peened specimens with 100% coverage crack for 3500 hours. However, steel-peenedspecimens with 200% coverage and glass-peened specimens with 50%, 100% and 200% coverageare tested for a total of 3500 hours without visible stress corrosion cracks in the peened surfaces.The experiment results indicate that shot peening is an effective method for protecting weldmentsagainst SCC and weldments peened by glass beads resist SCC better than those peened by steelshots
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Chinese Astronomy and Astrophysics 17 (1993), S. 362 
    ISSN: 0275-1062
    Keywords: Pulsar-neutron stars-cyclotron absorption
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Chinese Astronomy and Astrophysics 18 (1994), S. 279-281 
    ISSN: 0275-1062
    Keywords: pulsars-X-ray sources
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Chinese Astronomy and Astrophysics 18 (1994), S. 426-428 
    ISSN: 0275-1062
    Keywords: galactic bulge-X-ray source-oscillation
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 373-374 (Mar. 2008), p. 832-835 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A 3D finite element model is established to simulate the ultrasonic shot peening processby using a finite element software ABAQUS. The residual stress distribution of the AISI 304stainless steel induced by ultrasonic shot peening (USP) is predicted by finite element analysis.Ultrasonic shot peening (USP) process can cause a compressive residual stress layer on the surfaceof the material. During the simulation, many factors, e.g., ultrasonic shot peening duration, initialresidual stress, hourglass, etc., are taken into consideration for the purpose of optimizing the process.The simulation results show that ultrasonic shot peening can produce a compressive residual stresslayer on the surface of the material even if there is initial residual tensile stress (250MPa) and thelonger peening duration. The residual stress of simulation were compared with the experiment datawhich were obtained under the same ultrasonic shot peening parameters and have a good agreementwith the measurement values by X-ray diffraction method. In conclusion, ultrasonic shot peening isan effective method for protecting weldments against stress corrosion cracking by introducing thecompressive residual stress layer into the surface of stainless steel
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 353-358 (Sept. 2007), p. 461-464 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In order to validate a procedure for creep rupture tests using small punch specimens, theinfluences of oxidation on the creep deflection curve, rupture time and ductility of miniaturespecimens were investigated. Using disc test specimens of 10mm in diameter and 0.5mm in thickness,a variety of small punch creep (SPC) tests for Cr5Mo steel at the condition of 550°C-404N and650°C-189N under the protection of different Argon flow and in air atmosphere were firstly carriedout. Metallographic observations, micro-hardness testing and measurement for these specimens ofSPC test were performed. It indicates that the oxidized layer of specimens integrates and the residualthickness of specimens increases, while the hardness of specimens increases with the increment of theArgon flow. Moreover, the different oxidation degrees of specimens with the surface morphologywere compared in this paper. The test results show the rupture time of specimens can be effectivelyprolonged by the protection of different Argon flow
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 353-358 (Sept. 2007), p. 1704-1707 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In order to prevent stress corrosion cracking (SCC) of austenitic stainless steel weldment,a novel technique -laser peening- has been introduced which is able to convert surface tensilestresses in the weldment to surface compressive stresses. In this paper, water-immersed weldedspecimens of type 304 stainless steel are peened by Q-switched Nd: glass laser with a wavelength of1.06μm. A residual compressive layer is produced on the specimen surface by scanning laser pulseto cover the heat affected zone (HAZ) along the weld line. The residual compressive stress valuebased on X-ray measure is significant enough to prevent the initiation of stress corrosion crackingthat is also validated by the finite element analysis. The SCC accelerated tests for comparing thepotential against SCC of the specimens, which are unpeened and peened by laser pulse withdifferent laser spot coverage, are carried on. The results show that stress corrosion cracks on thesurface of unpeened specimen occur after immersion for 25 hours in boiling 42% MgCl2 solutionsat 143℃. In contrast, the specimen with 45% laser spot coverage cracks after immersion for 300hours, while, cracks are observed on the surface of laser-peened specimen with 80% laser spotcoverage after 985 hours of testing. The results show that laser peening is an effective technique forimproving the residual stress distribution and the SCC resistance of 304 stainless steel weldment
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  • 10
    Publication Date: 2018-06-07
    Print ISSN: 0024-9297
    Electronic ISSN: 1520-5835
    Topics: Chemistry and Pharmacology , Physics
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