Assessing the effect of residual stresses on the fatigue behavior of integrally stiffened structures

Labeas, G.; Diamantakos, Ioannis; Kermanidis, Th.

doi:10.1016/j.tafmec.2009.04.003

Cited by 9 publications

(5 citation statements)

References 11 publications

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“…which leads to two different values of the fatigue life (1 £ 10 5 and 1 £ 10 6 cycles) was calculated and the results are presented in Table IV. The efficiency at 1 £ 10 5 cycles with respect to the base material, by taking into account the base material fatigue limit to be Ds ¼ 140 Mpa (Labeas et al, 2009) is also presented in Table IV.…”

Section: Fatigue Test Resultsmentioning

confidence: 99%

“…These FE models do not take into account the hooking defects that are one of the main causes of weakness for FSW overlap joints. Residual stresses caused by the welding process (Labeas et al, 2009) are also not accounted for. However, it should be retained that this joint type creates a stress increase of about six times in the welding area compared to the remote load.…”

Section: Numerical Analysis Of a Fsw Overlap Jointmentioning

confidence: 99%

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Mechanical behaviour of AA 2024 friction stir overlap welds

Papadopoulos

Tavares

Pacchione

et al. 2013

International Journal of Structural Integrity

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Purpose -To investigate the effect of different welding configurations on the mechanical properties of friction stir welding (FSW) overlap joints. The application of FSW in an overlap configuration could be an attractive replacement to the riveting process for assembly of fuselage primary structures due to the similarity in tolerance management. However, the mechanical properties of welded overlap joints are often inferior to the respective riveted lap-joint properties. Design/methodology/approach -In order to quantify the static and fatigue strength of FSW overlap joints, numerical and experimental investigation on overlap welds were performed in the current work. Several single shear overlap joints welding configurations were investigated, including single and multiple pass friction stir welds. The static and fatigue behaviour of these joints was assessed through tensile and fatigue tests. Findings -Static and fatigue behaviour were found to strongly depend on the welding process parameters and configuration. With respect to the static behaviour, it was found that values close to base material can be achieved. However, depending on configuration and process parameters, static properties can be as low as about 30% of the base material properties. As for the fatigue behaviour, the fatigue limit for all configurations tested was found to be unrealistic for structural applications. Originality/value -The distance between the outermost welds in multiple pass welds were found to influence the mechanical properties, although no direct relationship can be derived. Indications have been found but no clear conclusion has been reached with respect to the optimum configuration. In some cases, specimens with superior tensile properties exhibited reduced fatigue properties whereas the exact opposite effect was observed for other configurations.

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Section: Fatigue Test Resultsmentioning

confidence: 99%

Section: Numerical Analysis Of a Fsw Overlap Jointmentioning

confidence: 99%

Mechanical behaviour of AA 2024 friction stir overlap welds

Papadopoulos

Tavares

Pacchione

et al. 2013

International Journal of Structural Integrity

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“…Some researchers have studied the performance of pressure hull materials under cyclic loading [23]. In addition, numerous studies have been made to estimate the welding residual stresses [24,25] of metal structures combined with experimental and numerical techniques under different loading conditions. Fatigue life assessment of pressure hull is studied by a method based on equivalent structural stress [26], and the most common approach to model the entire fatigue life of as-weld joints with some initial residual stress and flaws is by fracture mechanics [27].…”

Section: Introductionmentioning

confidence: 99%

Experimental Observation and Simulation on Crack Growth Behavior of An Equivalent Welding Joint for A Deep-Sea Spherical Hull

Wang

Zhong

Yang

et al. 2022

Metals

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The spherical pressure hull used in the manned cabin of deep-sea submersibles endures low-cycle fatigue problems during the process of cyclic submergence and recovery, but fatigue testing on its full-scale model is difficult to conduct. To approximate the problem, the paper proposed the design of an L-type equivalent welding joint to simulate the status of the strengthened part of the spherical pressure hull under a certain cyclic axial pressure history. The design principle of the equivalent welding joint is to ensure that the stress ratio between inner and outer surface and the distribution of the simulated test piece should be similar to or smaller than the actual stress distribution characteristics in the critical zone of the spherical hull for conservative consideration. The angle of the L-type joint is 175° in the present study, at which the stress on the outside is at the turning point from compressive stress to tensile stress. The fatigue experiment of the equivalent welding joint is conducted with measurements of crack growth and residual stresses. Multiple cracks are observed in the vicinity of the weld, which grows showing a typical low-cycle fracture morphology. The three-dimensional finite element modelling for the equivalent welding joint with prefabricated notch and the same weld zone shape with its tested piece is carried out. An improved crack growth model proposed by the author’s group, considering multiple factors, is adopted for crack growth calculation and compared with experimental results, which shows satisfactory agreement. The finite element modelling based on the pre-designed L-type joint combined with the improved crack growth rate model can be applied as a simplified method to simulate the fatigue life of the spherical pressure hull.

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“…Numerical analysis demonstrated that initial stresses had noticeable influence on a laminate plate’s nonlinear dynamic behavior. Labeas et al (2009) carried out the computation of stress intensity factors at the cracks of welded structures through a proposed numerical approach, which was used to analyze how residual stresses affected the values of stress intensity factors in stiffened plates. Tekgoz et al (2015) dealt with how residual stresses affected the ultimate strength of a single panel and a ribbed panel as well.…”

Section: Introductionmentioning

confidence: 99%

Dynamic stress analysis on nonlinear vibration of a stiffened plate with initial stresses and geometric imperfections considering different resonance conditions

Piao

et al. 2020

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Purpose Stiffened plates have been widely used in civil, marine, aerospace engineering. As a kind of thin-walled structure operating in complex environment, stiffened plates mostly undergo a variety of dynamic loads, which may sometimes result in large-amplitude vibration. Additionally, initial stresses and geometric imperfections are widespread in this type of structure. Furthermore, it is universally known that initial stresses and geometric imperfections may affect mechanical behavior of structures severely, particularly in dynamic analysis. Thus, the purpose of this paper is to study the stress variation rule of a stiffened plate during large-amplitude vibration considering initial stresses and geometric imperfections. Design/methodology/approach The initial stresses are represented in the form of initial bending moments applying to the stiffened plate, while the initial geometric imperfections are considered by means of trigonometric series, and they are assumed existing in the plate along the z-direction exclusively. Then, the dynamic equilibrium equations of the stiffened plate are established using Lagrange’s equation as well as aforementioned conditions. The nonlinear differential equations of motion are simplified as a two-degree-of-freedom system by considering 1:2 and 1:3 internal resonances, respectively, and the multiscale method is applied to solve the equations. Findings The influence of initial stresses on the plate, stresses during internal resonance is remarkable, while that is moderate for initial geometric imperfections. (Upon considering the existence of initial stresses or geometric imperfections, the stresses of motivated modes are less than the primary mode for both and internal resonances). The influence of bidirectional initial stresses on the plate’s stresses during internal resonance is more remarkable than that of unidirectional initial stresses. The coupled vibration in 1%3A2 internal resonance is fiercer than that in internal resonance. Originality/value Stiffened plates are widely used in engineering structures. However, as a type of thin-walled structure, stiffened plates vibrate with large amplitude in most cases owning to their complicated operation circumstance. In addition, stiffened plates usually contain initial stresses and geometric imperfections, which may result in the variation of their mechanical behavior, especially dynamical behavior. Based on the above consideration, this paper studies the nonlinear dynamical behavior of stiffened plates with initial stresses and geometrical imperfections under different internal resonances, which is the originality of this work. Furthermore, the research findings can provide references for engineering design and application.

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Assessing the effect of residual stresses on the fatigue behavior of integrally stiffened structures

Cited by 9 publications

References 11 publications

Mechanical behaviour of AA 2024 friction stir overlap welds

Mechanical behaviour of AA 2024 friction stir overlap welds

Experimental Observation and Simulation on Crack Growth Behavior of An Equivalent Welding Joint for A Deep-Sea Spherical Hull

Dynamic stress analysis on nonlinear vibration of a stiffened plate with initial stresses and geometric imperfections considering different resonance conditions

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