Analysis of warm prestress data

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Loading a cracked structure at elevated temperature, or warm prestressing (WPS), enhances its fracture resistance at a lower temperature. Five data sets, comprising 119 unclad pressure vessel steel specimens, were combined to derive correlations for WPS-enhanced fracture toughness (K{sub Ifrac}) in the absence of ductile tearing. New WPS test results for 27 surface flawed specimens, eight subclad flawed specimens, and five strain-aged specimens are discussed. K{sub Ifrac} exceeded non-WPS fracture toughness, K{sub Ic}, for all experiments. The WPS data showed that no specimens failed while K was decreasing, and that at least an additional seven percent additional reloading from the ... continued below

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26 p.

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Macdonald, B.D.; Embley, G.T.; Irizarry-Quinones, H.; Smith, P.D.; Wuthrich, J.W.; McAfee, W.J. et al. June 1, 1995.

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  • Knolls Atomic Power Laboratory
    Publisher Info: Knolls Atomic Power Lab., Schenectady, NY (United States)
    Place of Publication: Schenectady, New York

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Loading a cracked structure at elevated temperature, or warm prestressing (WPS), enhances its fracture resistance at a lower temperature. Five data sets, comprising 119 unclad pressure vessel steel specimens, were combined to derive correlations for WPS-enhanced fracture toughness (K{sub Ifrac}) in the absence of ductile tearing. New WPS test results for 27 surface flawed specimens, eight subclad flawed specimens, and five strain-aged specimens are discussed. K{sub Ifrac} exceeded non-WPS fracture toughness, K{sub Ic}, for all experiments. The WPS data showed that no specimens failed while K was decreasing, and that at least an additional seven percent additional reloading from the minimum value of applied K{sub I} took place prior to final fracture. The data included complete and partial unloading after WPS prior to final fracture. Crack tip 3-dimensional elastic-plastic finite element (3DEPFE) analysis was performed to support statistical analysis of the data. Regression models were compared with the Chell WPS model. Crack tip 3DEPFE analysis indicated that partially unloaded and completely unloaded data should be treated separately, and that the amount of unloading is unimportant for partially unloaded data. The regression models, which use K{sub I} at WPS (K{sub Iwps}) and K{sub Ic} as independent variables, better represented the WPS benefit than did the more complicated Chell model. An adequate accounting was made for constraint in the WPS experiments. The subclad flaw data support the use of the partial unload regression model, provided that some care is taken to represent the effect of intact cladding if present. The effect of strain aging at or below 260 C (500 F) on WPS benefit was of no consequence for the pressure vessel steels and WPS temperatures used to derive the regression models. The presence of ductile tearing precludes the use of the regression models. The regression model for partial unloading accurately predicted the behavior of full scale pressure vessel WPS experiments. All but one of the 174 experiments considered lie above the lower 2{sigma} estimate of the regressions. The experiments all supported Type I WPS, i.e., there was no fracture during cooling until reloading occurred. However, the regression equations apply to the reload, and are inapplicable to Type I WPS.

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26 p.

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INIS; OSTI as DE99002684

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  • 27. ASTM symposium on fatigue and fracture mechanics, Williamsburg, VA (United States), 26-29 Jun 1995

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  • Other: DE99002684
  • Report No.: KAPL-P--000008
  • Report No.: K--95069;CONF-950618--
  • Grant Number: AC12-76SN00052
  • Office of Scientific & Technical Information Report Number: 350937
  • Archival Resource Key: ark:/67531/metadc689026

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  • June 1, 1995

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  • July 25, 2015, 2:20 a.m.

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  • May 16, 2016, 12:23 p.m.

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Macdonald, B.D.; Embley, G.T.; Irizarry-Quinones, H.; Smith, P.D.; Wuthrich, J.W.; McAfee, W.J. et al. Analysis of warm prestress data, article, June 1, 1995; Schenectady, New York. (digital.library.unt.edu/ark:/67531/metadc689026/: accessed July 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.