Fracture Toughness of Hydrided Zircaloy-4 Sheet Under Through-Thickness Crack Growth Conditions PDF Download
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Author: P. A. Raynaud Publisher: ISBN: Category : Acoustic emission Languages : en Pages : 16
Book Description
The susceptibility of fuel cladding to failure in the case of a postulated reactivity-initiated accident may be determined by crack initiation within a hydride blister or rim and subsequent crack growth through the thickness of the cladding. This study has determined the fracture toughness of hydrided cold-worked stress relieved Zircaloy-4 sheet subject to through-thickness crack growth at both 25 and 300°C. The experimental approach utilizes a novel procedure in which a narrow linear strip of brittle hydride blister across the specimen width creates a well-defined precrack upon initial loading. The subsequent crack growth resistance is then characterized by four-point bending of the specimen and an elastic-plastic fracture mechanics analysis. At room temperature, the through-thickness fracture toughness (Kq) is sensitive to the orientation of the hydride platelets and Kq?25 MPa?m for crack growth through a mixed in-plane/out-of-plane hydride field. In contrast, Kq is much nigher (?75 MPa?m) when the hydride platelets are oriented predominantly in the plane of the sheet and therefore normal to both the crack plane and the crack growth direction. At 300°C, the material exhibits greater ductility as the hydride particles within the matrix resist fracture such that Kq?83 MPa?m, despite the much lower flow stress of the material.
Author: P. A. Raynaud Publisher: ISBN: Category : Acoustic emission Languages : en Pages : 16
Book Description
The susceptibility of fuel cladding to failure in the case of a postulated reactivity-initiated accident may be determined by crack initiation within a hydride blister or rim and subsequent crack growth through the thickness of the cladding. This study has determined the fracture toughness of hydrided cold-worked stress relieved Zircaloy-4 sheet subject to through-thickness crack growth at both 25 and 300°C. The experimental approach utilizes a novel procedure in which a narrow linear strip of brittle hydride blister across the specimen width creates a well-defined precrack upon initial loading. The subsequent crack growth resistance is then characterized by four-point bending of the specimen and an elastic-plastic fracture mechanics analysis. At room temperature, the through-thickness fracture toughness (Kq) is sensitive to the orientation of the hydride platelets and Kq?25 MPa?m for crack growth through a mixed in-plane/out-of-plane hydride field. In contrast, Kq is much nigher (?75 MPa?m) when the hydride platelets are oriented predominantly in the plane of the sheet and therefore normal to both the crack plane and the crack growth direction. At 300°C, the material exhibits greater ductility as the hydride particles within the matrix resist fracture such that Kq?83 MPa?m, despite the much lower flow stress of the material.
Author: A. Glendening Publisher: ISBN: Category : Biaxial deformation Languages : en Pages : 18
Book Description
The fracture behavior of unirradiated Zircaloy-4 containing either solid hydride blisters or hydrided rims has been examined for the contrasting conditions of equal-biaxial and plane-strain tensile deformation at three temperatures (25°, 300°, and 375°C). Cold-worked and stress-relieved Zircaloy-4 sheet containing hydride blisters shows nearly identical failure strains in equal-biaxial and plane-strain tensile deformation for a wide range of blister or rim depths. In all cases, failure strains decrease rapidly with increasing hydride blister or rim thickness, especially in the ?100 ?m range. Test temperature has a significant effect on ductility with failure strains at 300° and 375°C being much greater than at room temperature. The results indicate that the ductility of material containing hydride rims/blisters greater than ? 30-40 ?m deep is limited by crack growth, which occurs in a mode I manner at 25°C but in a mixed mode I/II manner at ?300°C (and at higher failure strain levels).
Author: PH. Davies Publisher: ISBN: Category : Compact tension specimen Languages : en Pages : 22
Book Description
This paper addresses problems involved in measuring fracture toughness of thin pressure tube material which, in the presence of radial-axial hydrides, undergoes a significant brittle to ductile fracture transition. Compact tension specimens (~5 mm thickness) are machined from flattened tensile strips of Zircaloy-2 in which radial hydrides (30 to 100 ppm hydrogen) are produced by precipitation under stress. Axial fracture toughness is determined for the unirradiated material between room temperature and 300°C using the dc potential drop method. At low and intermediate temperatures crack growth is governed predominantly by the presence of the radial hydrides, and the potential drop is shown to underestimate crack extension due to short-circuiting across tight crack faces. In the upper shelf regime where crack extension is governed mainly by the flow properties of the matrix, the potential drop overestimates crack extension due to through-thickness yielding. It is shown that good, reproducible results can be obtained by careful data analysis using individual specimen calibrations.
Author: Anthony W. Thompson Publisher: John Wiley & Sons ISBN: 1118803272 Category : Technology & Engineering Languages : en Pages : 1090
Book Description
Proceedings of the Fifth International Conference on the Effect of Hydrogen on the Behavior of Materials sponsored by the Structural Materials Division (SMD) Mechanical Metallurgy and Corrosion & Environmental Effects Committees of The Minerals, Metals & Materials Society held at Jackson Lake Lodge, Moran, Wyoming, September 11-14, 1994.
Author: Cyril A. Migdal Publisher: ASTM International ISBN: 0803134932 Category : Antioxidants Languages : en Pages : 929
Book Description
This work presents papers from a December 2005 symposium held in Norfolk, Virginia, and sponsored by ASTM Committee D2 on Petroleum Products and Lubricants and its Subcommittees D02.09 on Oxidation and D02.C0 on Turbine Oils. Contributors include equipment manufacturers, end users, lubricant producers, lubricant additive suppliers, test equipment manufacturers, and standard test method developers. They share information on industry trends, evolving technologies, and changing equipment designs and operating conditions, with a focus on how these factors impact oxidation. Some topics covered include turbine oil performance limits, a new form of the rotating pressure vessel oxidation test, and degradation mechanisms leading to sludge and varnish in modern turbine oil formulations. B&w photos are included. There is no subject index. Migdal is affiliated with Chemtura Corporation.
Author: K. Pettersson Publisher: ISBN: Category : Crack growth Languages : en Pages : 16
Book Description
Slow stable crack growth by a mechanism identified as a form of delayed hydride cracking has been studied on irradiated Zircaloy cladding. The background to the investigation was the formation of long axial cracks in defected fuel rods. Post-irradiation examination of such fuel rods has indicated that precipitation and subsequent cracking of hydrides at the tips of the long cracks has played an important role in the crack growth process. The present investigation conducted on irradiated cladding with hydrogen concentrations above about 500 ppm has demonstrated that a hydrogen-induced crack growth process can occur in such material. In the laboratory it was necessary to subject the samples to an overtemperature cycle in order to initiate crack growth after fatigue precracking. It was also observed that an incubation time on the order of 20 h was necessary before crack growth started. The crack growth rates were strongly dependent on the applied stress intensity factor K in a narrow range above a threshold value KIH, which was about 10 MPa?m, Stage I. The growth rate then reached a plateau value when it was independent of K, Stage II. This plateau value was about 10-6 m/s at 300°C and about 2 x 10-7 m/s at 200°C. This temperature dependence is consistent with a mechanism based on stress-induced diffusion of hydrogen at the stress concentration of the crack tip. Metallographic and fractographic observations suggest that the details of the mechanism can be best described as a localized reduction of fracture toughness due to reorientation of hydrides so that they become perpendicular to the applied stress in the region of the crack tip. This is somewhat in contrast to previous DHC mechanisms in which longer-range diffusion of hydrogen to one large hydride at the crack tip is usually modeled. The difference is that in the present case the hydride content is higher and therefore more hydrides are present.
Author: R. H. Ernst Publisher: ISBN: Category : Titanium Languages : en Pages : 12
Book Description
A brief study of delayed fracture in a seam-welded titanium panel is summarized in this memorandum. Examination of the fracture surface with electron microscopy showed that the material cleaved, failing in a brittle manner. Although the nature of the embrittlement was not clearly defined, titanium hydride phase was suspected as a prime contributor to failure. Even though the hydrogen content of the titanium was only 65 ppm, hydride embrittlement was thought to have occurred from precipitation of hydride platelets on crystal planes oriented normal to welding stresses. Other work, briefly discussed in the memorandum, has confirmed that hydride platelets in titanium can be oriented by stress and that tensile ductility of Zircaloy (which behaves similarly with respect to hydrogen, to titanium) depends upon hydride orientation. Stress-relief annealing of welded titanium structures is recommended wherever possible to minimize embrittlement by stress-oriented hydrides. (Author).
Author: P. A. Raynaud
Author: P. A. Raynaud
Author: A. Glendening
Author: PH. Davies
Author: 
Author: 
Author: Anthony W. Thompson
Author: Cyril A. Migdal
Author: K. Pettersson
Author: R. H. Ernst
Author: Peter Kenny