The Influence of Hydrogen on the Multiaxial Fracture Behavior of Titanium Alloy Sheets PDF Download
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Author: B. J. Lograsso Publisher: ISBN: Category : Languages : en Pages : 10
Book Description
The influence of hydrogen on the deformation and fracture of three Ti alloys in the form of sheet has been examined as a function of the state of stress. Unnotched sheet specimens of alpha-phase Ti ( -60, 630, and 980 ppm H), Beta-phase Ti-30V ( -40 and 2000 ppm H), and alpha-Beta Ti-6Al-4V (30, 240, and 500 ppm H) have been investigated over deformation paths ranging from uniaxial to equibiaxial tension. Based on the measurements of the local fracture strains, the alpha-Ti data show a decrease in ductility with increasing hydrogen content as the degree of biaxiality of the tensile strain increases. Thus hydrogen embrittlement of Ti sheet is most severe under equibiaxial straining. In contrast, there is no pronounced effect of stress state on the localized necking and fracture behavior of either the Ti-30V or the Ti-6Al-4V at any of the hydrogen levels/microstructures examined. The results indicate that, even in equibiaxial tension, Ti alloys in the form of sheet are immune to hydrogen embrittlement if hydrides do not form. If hydrides are present, the embrittlement is most pronounced under those state of stress (e.g., plane strain and equibiaxial tension) which are characterized by large normal stresses.
Author: B. J. Lograsso Publisher: ISBN: Category : Languages : en Pages : 10
Book Description
The influence of hydrogen on the deformation and fracture of three Ti alloys in the form of sheet has been examined as a function of the state of stress. Unnotched sheet specimens of alpha-phase Ti ( -60, 630, and 980 ppm H), Beta-phase Ti-30V ( -40 and 2000 ppm H), and alpha-Beta Ti-6Al-4V (30, 240, and 500 ppm H) have been investigated over deformation paths ranging from uniaxial to equibiaxial tension. Based on the measurements of the local fracture strains, the alpha-Ti data show a decrease in ductility with increasing hydrogen content as the degree of biaxiality of the tensile strain increases. Thus hydrogen embrittlement of Ti sheet is most severe under equibiaxial straining. In contrast, there is no pronounced effect of stress state on the localized necking and fracture behavior of either the Ti-30V or the Ti-6Al-4V at any of the hydrogen levels/microstructures examined. The results indicate that, even in equibiaxial tension, Ti alloys in the form of sheet are immune to hydrogen embrittlement if hydrides do not form. If hydrides are present, the embrittlement is most pronounced under those state of stress (e.g., plane strain and equibiaxial tension) which are characterized by large normal stresses.
Author: D. A. Koss Publisher: ISBN: Category : Languages : en Pages : 33
Book Description
Progress is reviewed for a research program whose primary purpose has been to provide a broad-based understanding of the deformation and fracture of high performance alloys in general and titanium alloys in particular. The research has ranged from strengthening mechanisms in titanium alloys to fundamental studies of crack propagation, localized necking, hydrogen embrittlement, and ductile fracture utilizing engineering alloy behavior. Progress for the period 1 July 1975 to 1 October 1984 is reviewed for the following portions of this research program: (1) the influence of silicon on the age hardening of beta-phase Ti alloys, (2) the flow and fracture behavior of multi-phase alloys with lamellar microstructures, (3) fracture along planar slip bands, (4) the multiaxial deformation and fracture of plastically anisotropic alloys in the form of sheet, (5) the influence of stress state on the hydrogen embrittlement of hydride-forming alloys in general and Ti in particular, and (6) the deformation and fracture of alloys containing pores and voids. Keywords: Ductile fracture, Crack growth, Porosity, Deformation, Hydrogen embrittlement, Age hardening, and Sheet metal deformation.
Author: R. J. Bourcier Publisher: ISBN: Category : Languages : en Pages : 32
Book Description
The ductility of commercially pure titanium sheet containing either 60, 630, or 980 wt ppm hydrogen has been investigated over deformation paths ranging from uniaxial to equibiaxial tension. Based on measurements of fracture strains measured locally from grids, the data show a decrease in ductility with increasing hydrogen content as the degree of biaxiality of the tensile strain increases. Thus hydrogen embrittlement of Ti sheet depends on deformation path, being the most severe under equibiaxial straining. The embrittlement occurs even though hydrogen has no significant effect on the room temperature yielding and flow behavior of Ti in either uniaxial or balanced biaxial tension. Quantitative metallography indicates that void nucleation is due to hydride fracture and occurs at comparatively small strains in plane strain and equibiaxial deformation. An analysis shows that the strain-induced fracture of the hydrides appears to obey a critical normal stress criterion, the stresses being caused by: (a) the inhomogeneity of strain between the matrix and the particles and (b) the maximum principal stress within the matrix. Calculations show that only the latter changes significantly with loading path, and this is primarily due to the strong degree of plastic anisotropy in the Ti sheet.
Author: C. W. Lentz Publisher: ISBN: Category : Titanium Languages : en Pages : 27
Book Description
The influence of internal hydrogen on the multiaxial stress-strain behavior of commercially pure titanium has been studied. Thin-walled tubing specimens containing either 20 or 1070 ppm hydrogen have been tested at constant stress ratios in combined tension and internal pressure. The addition of hydrogen lowers the yield strength for all loading paths but has no significant effect on the strain hardening behavior at strains epsilon>or= 0.02. thus, the hydrogen embrittlement of titanium under plain strain or equibiaxial loading is not a consequence of changes of flow behavior. The yielding behavior of this anisotropic material is described well by Hill's quadratic yield criterion. As measured mechanically and by pole figure analysis, the plastic anisotropy changes with deformation in a manner which depends on stress state. Hill's criterion and the associated flow rule do not describe the multiaxial flow behavior well because of their inability to account for changes of texture which depend on multiaxial stress path. Hence, a strain dependent, texture-induced strengthening effect in equibiaxial tension is observed, this effect having the form of an enhanced strain hardening rate.
Author: B. J. Lograsso
Author: B. J. Lograsso
Author: Barbara Kiiskila Lograsso
Author: 
Author: 
Author: D. A. Koss
Author: David F. Teter
Author: 
Author: R. J. Bourcier
Author: Charles William Lentz
Author: C. W. Lentz