Optimization of cruciform specimens for biaxial fatigue loading with direct multi search

Baptista, R.; Cláudio, R.A.; Reis, L.; Madeira, J.F.A.; Guelho, I.; Freitas, M.

doi:10.1016/j.tafmec.2015.06.009

Cited by 42 publications

(21 citation statements)

References 13 publications

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“…Both specimens follow a certain geometry with special relations between the dimensions. These relations were obtained from an optimisation of the geometry proposed by Baptista et al The geometry follows the design in Figure with dimensions given by Equations to .

italicRM ((), t) = - 0.0379 t^{4} + 0.8223 t^{3} - 5.5749 t^{2} + 12.555 t + 53.84

italicRm ((), t) = - 0.0236 t^{3} + 0.3501 t^{2} - 0.5036 t + 22.184

italicdd ((), t) = - 0.021 t^{4} + 0.4668 t^{3} - 3.248 t^{2} + 7.9452 t + 46.224

D ((), t) = 0.0342 t^{3} - 0.7936 t^{2} + 6.0398 t + 4.5526.4; 4 \leq t \leq 10 italicmm

θ ((), t) = - 0.7621 t^{3} + 15.484 t^{2} - 92.774 t + 211.78; 4 \leq t \leq 10 italicmm

italictt ((), t) = 0.15 t; t \geq 8 italicmm

…”

Section: Theoretical Background and Methodologymentioning

confidence: 99%

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Cruciform specimens' experimental analysis in ultrasonic fatigue testing

Costa

Montalvão

Freitas

et al. 2019

Fatigue Fract Eng Mat Struct

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In this paper, two special aluminium cruciform specimens are designed and tested in an ultrasonic fatigue machine. They were designed based on Single‐Input‐Multiple‐Output (SIMO) modal analysis to induce in‐plane biaxial stress combinations (in‐phase tension‐tension [T‐T] and out‐of‐phase compression‐tension [C‐T]) when at resonance at 20 kHz. The geometries were subjected to both numerical analysis and experimental testing to understand if they can indeed create the intended biaxial state of stresses. Both numerical and experimental results showed an impact of nearby resonant modes of noninterest on the correct functioning of the specimens, especially regarding the T‐T specimen where a large deviation from the mode of interest was measured. This means that future work includes re‐designing T‐T specimens taking into account these mode shapes. Only out‐of‐phase specimens demonstrated to work properly and tests until failure were conducted. The first failure results showed to be consistent with literature when out‐of‐phase biaxial stress is applied cyclically.

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italicRM ((), t) = - 0.0379 t^{4} + 0.8223 t^{3} - 5.5749 t^{2} + 12.555 t + 53.84

italicRm ((), t) = - 0.0236 t^{3} + 0.3501 t^{2} - 0.5036 t + 22.184

italicdd ((), t) = - 0.021 t^{4} + 0.4668 t^{3} - 3.248 t^{2} + 7.9452 t + 46.224

D ((), t) = 0.0342 t^{3} - 0.7936 t^{2} + 6.0398 t + 4.5526.4; 4 \leq t \leq 10 italicmm

θ ((), t) = - 0.7621 t^{3} + 15.484 t^{2} - 92.774 t + 211.78; 4 \leq t \leq 10 italicmm

italictt ((), t) = 0.15 t; t \geq 8 italicmm

…”

Section: Theoretical Background and Methodologymentioning

confidence: 99%

“…Both specimens follow a certain geometry with special relations between the dimensions. These relations were obtained from an optimisation of the geometry proposed by Baptista et al 22 The geometry follows the design in Figure 1 with dimensions given by Equations (1) to (6).…”

Section: Theoretical Background and Methodologymentioning

confidence: 99%

Cruciform specimens' experimental analysis in ultrasonic fatigue testing

Costa

Montalvão

Freitas

et al. 2019

Fatigue Fract Eng Mat Struct

View full text Add to dashboard Cite

show abstract

“…The final optimal geometry as a function of the base material sheet thickness is proposed, as a guide line for cruciform specimen design, and as a possible contribution for a future standard on in‐plane biaxial tests. The specimen geometry design was optimized using the Direct Multi‐Search methodology for the use with low capacity testing machine . Figure shows the optimal and the notched uniform thickness specimens developed and presented by Baptista et al…”

Section: Planar Specimens For Mixed Mode Evaluationmentioning

confidence: 99%

“…The specimen geometry design was optimized using the Direct Multi-Search methodology for the use with low capacity testing machine. 46 Figure 11 shows the optimal and the notched uniform thickness specimens developed and presented by Baptista et al 49 Both specimens present advantages and disadvantages. The optimal specimen, with reduced thickness in the centre, allows for high stress levels, fast crack initiation, and initial propagation, as a consequence of the higher stress intensity factors produced.…”

Section: Planar Specimens For Mixed Mode Evaluationmentioning

confidence: 99%

Mixed mode fatigue and fracture in planar geometries: Observations on K_eq and crack path modelling

Tavares

Reis

Freitas

et al. 2019

Fatigue Fract Eng Mat Struct

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The mixed mode I‐II fatigue and fracture is briefly reviewed, addressing experimental and numerical modelling aspects, and focusing on planar specimens. One major challenge concerns the determination of equivalent stress intensity factor (Keq) in mixed mode situations. Several approaches were compared through the determination of Keq/KI over a wide range of values of KI/KII or KII/KI. Whereas all different approaches converge to the same value as KI/KII increases, the same does not happen for large KII/KI, where differences between values of Keq persist. In the regions of 0 < KI/KII < 2 and 0 < KII/KI < 2, no stable trend of results can be defined. Experimental fatigue crack growth results are presented for Al alloy AA6082‐T6. Compact tension specimens, modified with holes, and four‐point bending specimens under asymmetrical loading promoting mixed mode situations, were subjected to fatigue crack growth tests, where crack path and crack growth rate were measured. The presentation of the fatigue crack growth data was made using a Paris law based upon Keq. Differences in the Paris law constants were found for the different Keq criteria. Recent developments in numerical techniques, as the implementation of the extended finite element method (XFEM) in finite element software packages allows to determine accurately crack paths in mixed mode fracture. This article highlights concepts for mixed‐mode fatigue and fracture and supporting data, identifying challenges still to be overcome.

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“…This study therefore focuses on reducing the volume of the gauge area to reach the aforementioned two conditions. Baptista et al [31] used cruciform specimen showing round thickness reduction on both sides of the active part. They obtained a maximum stress leading to damage at the center of the gauge area.…”

Section: Specimen Geometry Design For In Situ Loading In Semmentioning

confidence: 99%

Local behavior of an AISI 304 stainless steel submitted to in situ biaxial loading in SEM

Caer

Pesci

2017

Materials Science and Engineering: A

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The microstructural response of a coarse grained AISI 304 stainless steel submitted to biaxial tensile loading was investigated using SEM and X-ray diffraction. The specimen geometry was designed to allow for biaxial stress state and incipient crack in the center of the active part under biaxial tensile loading. This complex loading was performed step by step by a micromachine fitting into a SEM chamber. At each loading step FSD pictures and EBSD measurements were carried out to study the microstructural evolution of the alloy, namely grain rotations and misorientations, stress-induced martensite formation and crack propagation. According to their initial orientation, grains are found to behave differently under loading. Approximately 60% of grains are shown to reorient to the [110] Z orientation under biaxial tensile loading, whereas the 40% left undergo high plastic deformation. EBSD and XRD measurements respectively performed under loading and on the post mortem specimen highlighted the formation of about 4% of martensite.

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Optimization of cruciform specimens for biaxial fatigue loading with direct multi search

Cited by 42 publications

References 13 publications

Cruciform specimens' experimental analysis in ultrasonic fatigue testing

Cruciform specimens' experimental analysis in ultrasonic fatigue testing

Mixed mode fatigue and fracture in planar geometries: Observations on K_eq and crack path modelling

Local behavior of an AISI 304 stainless steel submitted to in situ biaxial loading in SEM

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Optimization of cruciform specimens for biaxial fatigue loading with direct multi search

Cited by 42 publications

References 13 publications

Cruciform specimens' experimental analysis in ultrasonic fatigue testing

Cruciform specimens' experimental analysis in ultrasonic fatigue testing

Mixed mode fatigue and fracture in planar geometries: Observations on Keq and crack path modelling

Local behavior of an AISI 304 stainless steel submitted to in situ biaxial loading in SEM

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Product

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Mixed mode fatigue and fracture in planar geometries: Observations on K_eq and crack path modelling