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Strain Cycles (strain + cycle)

Distribution by Scientific Domains
Polymers and Materials Science60%
Engineering40%

Selected Abstracts

Orientation and strain cycle effects on the impact performance of polyethylene

POLYMER ENGINEERING & SCIENCE, Issue 4 2005
Alexis Paizis
The effects of orientation by plastic strain on the impact fracture resistance of a pipe-grade polyethylene have been investigated. Isotropic samples of bulk polymer were subjected, by plane-strain compression, to uniform Hencky strains of up to ±40%. In some samples this strain was reversed to restore the original dimensions. Impact bend specimens were prepared from samples oriented either normal to or within the fracture plane. Plane-strain fracture resistance and transition temperature were measured at 1 m/s by using the ISO 17281 method, and plane stress fracture resistance was measured by using the Reversed Charpy test. Orientation within the fracture plane by plastic compression across it compromises the relatively high plane-stress toughness of this material and increases the brittle-tough transition temperature, while the opposite is true of plastic extension. Reversion from a state of adverse orientation, by completing a strain cycle, only partially restores the fracture resistance of the isotropic polymer. POLYM. ENG. SCI., 45:596,605, 2005. © 2005 Society of Plastics Engineers [source]

Fatigue crack initiation life estimation in a steel welded joint by the use of a two-scale damage model

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2009
N. LAUTROU
ABSTRACT This work deals with the fatigue behaviour of S355NL steel welded joints classically used in naval structures. The approach suggested here, in order to estimate the fatigue crack initiation life, can be split into two stages. First, stabilized stress,strain cycles are obtained in all points of the welded joint by a finite element analysis, taking constant or variable amplitude loadings into account. This calculation takes account of: base metal elastic,plastic behaviour, variable yield stress based on hardness measurements in various zones of the weld, local geometry at the weld toe and residual stresses if any. Second, if a fast elastic shakedown occurs, a two-scale damage model based on Lemaitre et al.'s work is used as a post-processor in order to estimate the fatigue crack initiation life. Material parameters for this model were identified from two Wöhler curves established for base metal. As a validation, four-point bending fatigue tests were carried out on welded specimens supplied by ,DCNS company'. Two load ratios were considered: 0.1 and 0.3. Residual stress measurements by X-ray diffraction completed this analysis. Comparisons between experimental and calculated fatigue lives are promising for the considered loadings. An exploitation of this method is planned for another welding process. [source]

An investigation into the surface fatigue of materials and thin layers using a sliding diamond spherical segment

LUBRICATION SCIENCE, Issue 2 2000
Ivan Iliuc
Abstract Methods for testing the surface fatigue of materials or thin layers normally involve configurations with two or more rolling balls or discs. Such equipment and test specimens are quite complicated, and for a large number of experiments, costly. Testing could be considerably simplified if the stressing of the material surface were performed with a sliding natural diamond spherical segment. A diamond on steel (or any different material) friction pair has the particular attribute that sliding wear is absent. Under these circumstances, after a certain number of strain cycles, fatigue failure of the investigated surface or layers appears. A particularly relevant application is investigation of the adhesion of a DLC layer. [source]

Fatigue crack initiation in naval welded joints: experimental and numerical approaches

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2008
D. Thevenet
This work deals with the fatigue behavior of welded joints. The proposed strategy can be split into two stages: the structure shakedown study and the fatigue crack initiation study. Firstly, stabilized elastic stress,strain cycles are obtained in any point of the welded joint by a finite element analysis, taking constant or variable amplitude loadings into account. The second part of this work is the calculation of the fatigue crack initiation period. Under the assumption of a fast elastic shakedown, a recent approach, proposed by Lemaitre et al., based on damage mechanics, can be used to predict the fatigue crack initiation life in a structure subjected to variable and complex loadings. This strategy is used as a post,treatment of the shakedown finite element calculation for the studied welded specimen. As a validation, four,point bending fatigue tests under constant amplitude loading were carried out on welded specimens provided by DCNS group. Good correlations between experimental and calculated fatigue crack initiation lives have been established. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

The Role of Filler Networking in Fatigue Crack Propagation of Elastomers under High-Severity Conditions

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2009
Manfred Klüppel
Abstract Structural parameters of the filler network have been evaluated by fitting quasi-static stress/strain cycles to the dynamic flocculation model. It is found that the size of filler clusters as well as the strength of filler,filler bonds increase with filler loading and carbon black activity (specific surface). This correlates with the behavior of the tear resistance obtained for pulsed loading under high-severity conditions, implying that the characteristics of the filler network govern the fracture properties of filled elastomers. The behavior of the power law exponent of fatigue crack propagation versus tearing energy can be explained by flash temperature effects in the crack tip area. [source]