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| Abstract No.: |
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Scheduled at:
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Thursday, June 23, 2022, Saal Brüssel 11:20 AM
Modeling and simulation
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| Title: |
Extrapolation of short-time creep tests to long-time creep values:
Selection of a model for brazed joints
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| Authors: |
Alexander E. Shapiro* / Titanium Brazing, Inc., United States of America
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| Abstract: |
Evaluation of the reliability of brazed or soldered joints at high temperatures during their entire service life is necessary for many applications: from jet engines to fuel cells and hydrogen storage systems. The service life of these products varies greatly: from 6000 hours for some jet engines to 300 years for power station aggregates. Therefore, full-size creep tests are not possible in laboratory conditions - extrapolation of short-term tests for the expected service life is always used. However, the practice of hot testing of brazed or soldered joints has shown the presence of two problems with these tests: (1) large scatter in measured values of rupture stress over time and (2) excessive duration of the hot tests (even testing one sample for 200 hours takes more than a week).
During the twentieth century, the industry has accumulated a very large experience of accelerated tests of high-temperature creep of homogeneous samples, but very little experience of such tests for brazed and soldered joints. Our industry does not even have standards for testing creep resistance of brazed structures.
This paper considers the applicability of existing extrapolation models of short-time creep tests (Larson-Miller or Manson-Haferd parameters, Garofalo creep law, and others) to assess the long-time creep of brazed and soldered joints. As a result, two different accelerated testing methods and extrapolation models are recommended for brazed and soldered joints: the Larson-Miller parameter - for creep testing of brazed joints, - and the Garofalo hyperbolic sine equation - for creep testing of soldered joints.
Application of selected extrapolation models is illustrated by creep test diagrams of titanium brazed joints manufactured using Ti-Zr-Cu-Ni braze alloys and their derivatives.
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