9,365 research outputs found
A New Formulation of the C-S Multiaxial Fatigue Criterion in the Frequency Domain
No full textIn the present paper, a new computationally-efficient frequency domain formulation of the critical plane-based Carpinteri-Spagnoli (C-S) criterion is proposed to evaluate the fatigue lives of smooth metallic structures subjected to multiaxial random loading. The critical plane orientation is here proposed to depend on the Power
Spectral Density (PSD) matrix of the stress tensor. Then, the PSD function of an equivalent normal stress is defined by considering a linear combination of the PSD functions of the normal stress and the projected shear stress along the direction of maximum variance, with such stresses acting on the critical plane. The equivalent PSD function obtained allows us to apply the Tovo-Benasciutti method in order to determine the fatigue life of the structure being examined. The frequency domain formulation of
the C-S criterion is applied to some relevant random fatigue tests related to smooth specimens under non-proportional bending and torsion random loading
An Alternative Definition of the Shear Stress Amplitude for the modified C-S (Carpinteri - Spagnoli) Criterion
No full textAn Alternative Definition of the Shear Stress Amplitude for the modified C-S (Carpinteri - Spagnoli) Criterio
Lifetime Estimation in the Low/Medium-Cycle Regime Using the Carpinteri-Spagnoli Multiaxial Fatigue Criterion
No full textA critical plane-based high-cycle multiaxial fatigue criterion, known as the Carpinteri–Spagnoli (C–S)
criterion, is here extended to evaluate the fatigue lifetime of plain metallic components under constant
amplitude loading in the low/medium-cycle regime. This extended criterion, based on strain components,
resolves the strain tensor into the normal and shear components acting on the critical plane, which is
determined on the basis of the principal strain courses over the loading cycle. An equivalent normal strain
amplitude, computed through a quadratic combinations of strain components in the critical plane, is
taken as the fatigue damage parameter. The required input parameters of the criterion are obtained from
the classical Manson–Coffin–Basquin law for axial loading. A validation by experimental data pertaining
the biaxial fatigue of plain steel specimens under both proportional and non-proportional loadings is
performed
MRH method and modified C-S (Carpinteri-Spagnoli) criterion
No full textIn the present paper, a new formulation of the modified C-S criterion is discussed.
The modified C-S criterion is a critical-plane-based multiaxial high-cycle fatigue criterion, where the multiaxial fatigue limit condition is represented by a quadratic combination of the equivalent normal stress and the shear stress amplitude, acting on the critical plane. The new formulation here proposed consists in the implementation of the Maximum Rectangular Hull (MRH) method (to evaluate the shear stress amplitude), which is very simple and computationally more efficient
than the Minimum Bounding Circle method. Some experimental data available in the literature are analysed, and the fatigue strength estimations determined by applying both the above new formulation of the modified C-S criterion (based on the critical plane approach) and the Araújo et al. criterion (based on the stress invariants approach) are compared
A comparison between time- and frequency-domain Carpinteri criteria for fatigue life estimation under multiaxial random loading
No full textStructures and mechanical components are frequently subjected to time-varying loading
characterised by a random nature. Their fatigue design is complex, especially in the case of a multiaxial local
stress state.
A time-domain criterion is often applied to evaluate the fatigue life. Time-domain criteria are based on cycle
counting methods. Under both uniaxial loading and multiaxial proportional loading, the Rain-Flow Counting
(RFC) procedure is considered as the most accurate method by the scientific community. However, when
loading cannot easily be described by using time signals, a frequency-domain criterion has to be employed.
Frequency-domain criteria are based on the statistical properties of a suitable counting variable.
In the present paper, two critical plane-based criteria proposed by Carpinteri et al. are discussed. Such criteria
are able both to perform the fatigue assessment and to estimate the nucleation crack paths. More precisely, one
is formulated in time-domain whereas the other one in frequency domain. Such criteria are here modified in
order to improve their accuracy in terms of fatigue life estimation, and then applied to experimental fatigue data
related to 18G2A structural steel tests available in the literature, performed on smooth specimens under
random non-proportional bending and torsion loading
An alternative definition of the shear stress amplitude based on the Maximum Rectangular Hull method and application to the C-S (Carpinteri-Spagnoli) criterion
No full textIn the present paper, the fatigue strength estimation capabilities of the modified C-S
(Carpinteri-Spagnoli) criterion are improved by employing the Maximum Rectangular
Hull (MRH) method proposed by the first author. The C–S criterion is a multiaxial
high-cycle fatigue criterion based on the critical plane approach and takes into account both
shear stress (Mode II) and normal stress (Mode I)mechanisms to evaluate the orientation of
the critical plane. The fatigue damage parameter used is given by a nonlinear combination
of the equivalent normal stress amplitude,Na,eq, and the shear stress amplitude, Ca, acting on
the critical plane. In the present paper, the shear stress amplitude is evaluated through the
MRH method. Some experimental data available in the literature are compared with the
theoretical estimations, concluding that the multiaxial fatigue strength evaluations provided
by the C–S criterion are improved when Ca is computed applying theMRHmethod instead
of the Minimum Bounding Circle (MBC) method
A truncated statistical model for analyzing the size-effect on tensile strength of concrete structures
No full textThe statistical model presented in this paper assumes a truncated defect size distribution and predicts a scale effect in complete accordance with that of the Multifractal Scaling Law proposed by Carpinteri (1994a) and Carpinteri et al. (1994a, 1994b, 1995). This truncated distribution model is based on the weakest link concept and aims at evaluating the size effect on the nominal tensile strength of concrete. The expression of the truncated distribution is a Beta-Distribution. The structural failure occurs when the most dangerous defect reaches the propagation critical condition, based on a local LEFM failure criterion. By using this local failure condition, it is possible to obtain the local strength distribution. The global failure probability is obtained by the composition of the n independent local failure conditions. The paper ends with the presentation of the results obtained by this model and with the comparison with some experimental dat
Life estimation by varying the critical plane orientation in the modified Carpinteri-Spagnoli criterion
Get PDFThe modified Carpinteri-Spagnoli (C-S) criterion is a multiaxial high-cycle fatigue criterion based on
the critical plane approach. According to such a criterion, the orientation of the critical plane is linked to both
the averaged directions of the principal stress axes and the fatigue properties of the material. The latter
dependence is taken into account through a rotational angle, . Then, the multiaxial fatigue strength estimation
is performed by computing an equivalent stress amplitude on the critical plane. In the present paper, some
modifications of the original expression are implemented in the modified C-S criterion. More precisely, such
modified expressions of depend on the ratio between the fatigue limit under fully reversed shear stress and
that under fully reversed normal stress (in accordance with the original expression), and can be employed for
metals ranging from mild to very hard fatigue behaviour. Some experimental data available in the literature are
compared with the theoretical results in order to verify if the modified expressions are able to improve the
fatigue strength estimation capability of the modified C-S criterio
Multiaxial fatigue life estimation in welded joints using the critical plane approach.
No full textMany engineering structures experience multiaxial fatigue states of stress–strain in the vicinity of
welded joints. Fatigue assessment of welded joints under proportional (in-phase) cyclic loading can be
performed by using conventional hypotheses (e.g., see the von Mises criterion or the Tresca criterion)
on the basis of local approaches. On the contrary, the fatigue life predictions of welded joints under
non-proportional (out-of-phase) cyclic loading are generally poor if these conventional hypotheses are
used. In the present paper, the critical plane-based multiaxial fatigue criterion proposed by Carpinteri
and Spagnoli for smooth and notched structural components is extended to the fatigue assessment of
welded joints under in- and out-of-phase loadings. The applicability of this criterion, expressed in terms
of nominal stresses, to the fatigue life prediction of welded specimens is investigated by using experimental
data available in the literature
Reformulation in the frequency domain of a critical plane-based multiaxial fatigue criterion
No full textIn the present paper, a new computationally-efficient frequency domain formulation of the critical planebased
Carpinteri–Spagnoli (C–S) criterion is proposed to evaluate the fatigue lives of smooth metallic
structures subjected to multiaxial random loading. The critical plane orientation is here proposed to
depend on the Power Spectral Density (PSD) matrix of the stress tensor. Then, the PSD function of an
equivalent normal stress is defined by considering a linear combination of the PSD functions of the normal
stress and the projected shear stress along the direction of maximum variance, with such stresses
acting on the critical plane. Such an equivalent PSD function allows us to apply the Tovo–Benasciutti
method to estimate the fatigue life of the structural components. The present frequency domain formulation
of the C–S criterion is applied to some relevant fatigue tests related to smooth specimens under
non-proportional bending and torsion random loading
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