Some observations on short fatigue cracks under biaxial fatigue

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ABSTRACT.A study on the approximation of the stress field in the vicinity of crack tip in a compact tension specimen made from Al 2024-T351 is presented. Crack tip stress tensor components are expressed using the linear elastic fracture mechanics (LEFM) theory in this work, more precisely via its multi-parameter formulation, i.e. by Williams power series (WPS). Determination of coefficients of terms of this series is performed using a least squares-based regression technique known as over deterministic method (ODM) for which displacements data obtained experimentally via optical measurements are taken as inputs. The stress fields reconstructed based on the displacement data obtained experimentally by means of optical measurements are verified by means of the stress field approximations derived for the normalized CT specimen via hybrid elements.

Section: Materials Al 2024 and Methods Of Measurementmentioning

confidence: 99%

Williams expansion-based approximation of the stress field in an Al 2024 body with a crack from optical measurements

Seitl¹,

Malíková²,

Sobek³

et al. 2017

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“…aterial and test data have been taken from the previous biaxial fatigue test program at the University of Malaga [20]. The material that has been considered for this paper is St52-3N.…”

Section: Methodsmentioning

confidence: 99%

Evaluation of new multiaxial damage parameters on low carbon steel

Cruces¹,

López-Crespo²,

Moreno³

et al. 2017

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Most mechanical components are subjected to the complex fatigue loading conditions, where both amplitude and direction of loading cycles change over the time. The estimation of damage caused by these complex loading scenarios are often done by simplified uniaxial fatigue theories, which ultimately leads to higher factor of safety during the final design considerations. Critical plane-based fatigue theories have been considered more accurate for computing the fatigue damage for multiaxial loading conditions in comparison to energy-based and equivalent stress-based theories. Two recently developed fatigue theories have been evaluated in this work for the available test data. Test data includes significant amount of biaxial load paths.

“…A schematic of the geometry is shown in Fig. 1 A MTS 809 servo-hydraulic loading rig coupled by a biaxial extensometer Epsilon 3550 was used to apply biaxial loads under stress control mode in a similar way to previous works [22,24]. Cyclic sinus signal with axial load ratio of 0.1 (R a = 0.1) and torsional load ratio of -1 (Rt=-1) was applied while the angle between the axial and the torsional stress, φ, was set to 45°.…”

Section: Methodsmentioning

confidence: 99%

Experimental and analytical study of cracks under biaxial fatigue

Mokhtarishirazbad¹,

López-Crespo²,

Moreno³

et al. 2016

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Most mechanical components experience multi-axial cyclic loading conditions during service. Experimental analysis of fatigue cracks under such conditions is not easy and most works tend to focus more on the simpler but less realistic case of uni-axial loading. Consequently, there are many uncertainties related to the load sequence effect that are now well known and are not normally incorporated into the growth models. The current work presents a new methodology for evaluating overload effect in biaxial fatigue cracks. The methodology includes evaluation of mixed-mode (KI and KII) stress intensity factor and the Crack Opening Displacement for samples with and without overload cycle under biaxial loading. The methodology is tested under a range of crack lengths. All crack-tip information is obtained with a hybrid methodology that combines experimental full-field digital image correlation data and Williams' elastic model describing the crack-tip field.