Numerical measures of the degree of non-proportionality of multiaxial fatigue loadings
The influence of the non-proportional loadings on the fatigue life depends on the material ductility. Ductile materials react with a shortening of lifetime compared to proportional loading conditions. For a semiductile material there is almost no difference between proportional and non-proportiona...
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Gruppo Italiano Frattura
2015-07-01
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| Series: | Fracture and Structural Integrity |
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| Online Access: | http://www.gruppofrattura.it/pdf/rivista/numero33/numero_33_art_30.pdf |
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| author | A. Bolchoun H. Kaufmann C. M. Sonsino |
| author_facet | A. Bolchoun H. Kaufmann C. M. Sonsino |
| author_sort | A. Bolchoun |
| collection | DOAJ |
| description | The influence of the non-proportional loadings on the fatigue life depends on the material ductility.
Ductile materials react with a shortening of lifetime compared to proportional loading conditions. For a semiductile
material there is almost no difference between proportional and non-proportional loadings with respect
to the fatigue life. Brittle materials show an increase of the lifetime under non-proportional loadings. If fatigue
life assessment is performed using stress-based hypotheses, it is a rather difficult task to take into account
material ductility correctly, especially the fatigue life reduction as displayed by ductile materials.
Most stress-based hypotheses will compute a longer fatigue life under non-proportional loading conditions.
There are also hypotheses, which already include quantitative evaluation of the non-proportionality (e.g. EESH,
SSCH and MWCM). Anyway in order to improve assessment for ductile materials, some sort of numerical
measure for the degree of non-proportionality of the fatigue loading is required. A number of measures of this
kind (or non-proportionality factors) were proposed in the literature and are discussed here:
- the factor used in EESH is a quotient of stress amplitudes integrals,
- the factor according to Gaier, which works with a discrete stress tensor values in a scaled stress space,
- the factor according to Kanazawa, which makes use of plane-based stress values,
- the factor used in MWCM, which exploits stress values in the plane with the highest shear stress amplitude,
a new non-proportionality factor, which is based on the correlation between individual stress tensor
components, is proposed.
General requirements imposed on the non-proportionality factors are discussed and each of the factors is
evaluated with respect to these requirements. Also application with the stress-based hypotheses is discussed and
illustrated using the experimental data for aluminum and magnesium welded joints under constant and variable
amplitude loadings. |
| format | Article |
| id | doaj-art-fcb1dfe4d24546058c946a17add6915f |
| institution | Kabale University |
| issn | 1971-8993 1971-8993 |
| language | English |
| publishDate | 2015-07-01 |
| publisher | Gruppo Italiano Frattura |
| record_format | Article |
| series | Fracture and Structural Integrity |
| spelling | doaj-art-fcb1dfe4d24546058c946a17add6915f2025-01-03T01:40:53ZengGruppo Italiano FratturaFracture and Structural Integrity1971-89931971-89932015-07-0193323825210.3221/IGF-ESIS.33.30Numerical measures of the degree of non-proportionality of multiaxial fatigue loadingsA. Bolchoun0H. Kaufmann1C. M. Sonsino2Technische Universität Darmstadt,GermanyFraunhofer Institute for Structural Durability and System Reliability,GermanyFraunhofer Institute for Structural Durability and System Reliability,GermanyThe influence of the non-proportional loadings on the fatigue life depends on the material ductility. Ductile materials react with a shortening of lifetime compared to proportional loading conditions. For a semiductile material there is almost no difference between proportional and non-proportional loadings with respect to the fatigue life. Brittle materials show an increase of the lifetime under non-proportional loadings. If fatigue life assessment is performed using stress-based hypotheses, it is a rather difficult task to take into account material ductility correctly, especially the fatigue life reduction as displayed by ductile materials. Most stress-based hypotheses will compute a longer fatigue life under non-proportional loading conditions. There are also hypotheses, which already include quantitative evaluation of the non-proportionality (e.g. EESH, SSCH and MWCM). Anyway in order to improve assessment for ductile materials, some sort of numerical measure for the degree of non-proportionality of the fatigue loading is required. A number of measures of this kind (or non-proportionality factors) were proposed in the literature and are discussed here: - the factor used in EESH is a quotient of stress amplitudes integrals, - the factor according to Gaier, which works with a discrete stress tensor values in a scaled stress space, - the factor according to Kanazawa, which makes use of plane-based stress values, - the factor used in MWCM, which exploits stress values in the plane with the highest shear stress amplitude, a new non-proportionality factor, which is based on the correlation between individual stress tensor components, is proposed. General requirements imposed on the non-proportionality factors are discussed and each of the factors is evaluated with respect to these requirements. Also application with the stress-based hypotheses is discussed and illustrated using the experimental data for aluminum and magnesium welded joints under constant and variable amplitude loadings.http://www.gruppofrattura.it/pdf/rivista/numero33/numero_33_art_30.pdfMultiaxial fatigueNon-proportional loadingsNon-proportionality measuresWelded jointsStress-based criteria. |
| spellingShingle | A. Bolchoun H. Kaufmann C. M. Sonsino Numerical measures of the degree of non-proportionality of multiaxial fatigue loadings Fracture and Structural Integrity Multiaxial fatigue Non-proportional loadings Non-proportionality measures Welded joints Stress-based criteria. |
| title | Numerical measures of the degree of non-proportionality of multiaxial fatigue loadings |
| title_full | Numerical measures of the degree of non-proportionality of multiaxial fatigue loadings |
| title_fullStr | Numerical measures of the degree of non-proportionality of multiaxial fatigue loadings |
| title_full_unstemmed | Numerical measures of the degree of non-proportionality of multiaxial fatigue loadings |
| title_short | Numerical measures of the degree of non-proportionality of multiaxial fatigue loadings |
| title_sort | numerical measures of the degree of non proportionality of multiaxial fatigue loadings |
| topic | Multiaxial fatigue Non-proportional loadings Non-proportionality measures Welded joints Stress-based criteria. |
| url | http://www.gruppofrattura.it/pdf/rivista/numero33/numero_33_art_30.pdf |
| work_keys_str_mv | AT abolchoun numericalmeasuresofthedegreeofnonproportionalityofmultiaxialfatigueloadings AT hkaufmann numericalmeasuresofthedegreeofnonproportionalityofmultiaxialfatigueloadings AT cmsonsino numericalmeasuresofthedegreeofnonproportionalityofmultiaxialfatigueloadings |