Search results for "Strain energy density function"
showing 10 items of 16 documents
Estimation of the fatigue life of high strength steel under variable-amplitude tension with torsion: Use of the energy parameter in the critical plane
2003
Abstract The paper concerns application of the energy parameter, being a sum of the elastic and plastic strain energy density in the critical plane, for describing experimental data obtained in fatigue tests of 35NCD16 steel, subjected to constant amplitude tension-compression, torsion and variable amplitude tension-compression, torsion and combined proportional tension with torsion. It has been shown that the normal strain energy density in the critical plane is a suitable parameter for correlation of fatigue lives of 35NCD16 steel under considered kinds of loading. The critical plane is the plane where the normal strain energy density reaches its maximum value.
Nonsmooth Mechanics. Convex and Nonconvex Problems
1999
Nonlinear, multivalued and possibly nonmonotone relations arise in several areas of mechanics. A multivalued or complete relation is a relation with complete vertical branches. Boundary laws of this kind connect boundary (or interface) quantities. A contact relation or a locking mechanism between boundary displacements and boundary tractions in elasticity is a representative example. Material constitutive relations with complete branches connect stress and strain tensors, or, in simplified theories, equivalent stress and strain quantities. A locking material or a perfectly plastic one is represented by such a relation. The question of nonmonotonicity is more complicated. One aspect concerns…
Fatigue life under non-Gaussian random loading from various models
2004
Fatigue test results on the 10HNAP steel under constant amplitude and random loading with non-Gaussian probability distribution function, zero mean value and wide-band frequency spectrum have been used to compare the life time estimation of the models proposed by Bannantine, Fatemi–Socie, Socie, Wang–Brown, Morel and Łagoda–Macha. Except the Morel proposal which accumulates damage step by step with a proper ethodology, all the other models use a cycle counting method. The rainflow algorithm is used to extract cycles from random histories of damage parameters in time domain. In the last model, where a strain energy density parameter is employed, additionally spectral method is evaluated for …
Energy models for fatigue life estimation under uniaxial random loading. Part II: Verification of the model
2001
Abstract The paper concerns verification of the energy model for the fatigue life determination under the uniaxial random and variable-amplitude stress state. Application of the energy parameter for the fatigue life calculation using the algorithmic method under the random and variable-amplitude uniaxial tension–compression proves that most results of the fatigue life calculation are included in the scatter band with the coefficient determined during the uniaxial cyclic tests. The strain energy density parameter seems to be efficient for the fatigue life determination in the ranges of high and low numbers of cycles. The analysis was based on the author's tests and the data from literature. …
Comparison of the Rain Flow Algorithm and the Spectral Method for Fatigue Life Determination Under Uniaxial and Multiaxial Random Loading
2008
This paper presents the strain energy density parameter used for fatigue life calculation under random loading by two methods. The first method is based on schematization of energy parameter histories with the rain flow algorithm. The other one is based on moments of the power spectral density function of the energy parameter. The experimental data of fatigue tests of 10HNAP steel under constant amplitude and random uniaxial loading with non-gaussion probability distribution, zero mean value, and wide-band frequency spectrum used for comparison of the rain flow algorithm and the spectral method gave satisfactory results. Next, histories of the random stress tensor with normal probability di…
Infrared thermography-based evaluation of the elastic-plastic J-integral to correlate fatigue crack growth data of a stainless steel
2019
Abstract The elastic-plastic J-integral is adopted to correlate fatigue crack growth data of ductile metals. An analytical link is known to exist between the J-integral and the strain energy density averaged in a control volume embracing the crack tip. On the other hand, the strain energy fluctuation is the source of temperature variations close to a fatigue crack tip of a metal material; hence the possibility to measure the J-integral from infrared thermographic scanning at the crack tip is envisaged and it is the focus of this paper. It is proposed that the elastic component of the J-integral is derived from a thermoelastic stress analysis, while the plastic component of the J-integral is…
Energy criteria of multiaxial fatigue failure
1999
This paper contains a review of energy-based criteria of multiaxial fatigue. The criteria have been divided into three groups, depending on the kind of strain energy density per cycle which is assumed as a damage parameter. They are: (i) criteria based on elastic strain energy for high-cycle fatigue; (ii) criteria based on plastic strain energy for low-cycle fatigue; and (iii) criteria based on the sum of plastic and elastic strain energies for both low- and high-cycle fatigue. The criteria which take into account strain energy density in the critical plane seem to be the most promising. In the energy approach to multiaxial fatigue there is an important unsolved problem, i.e. the evaluation…
Calculation of the elastic–plastic strain energy density under cyclic and random loading
2001
Abstract The paper presents a method of identification and calculation of the components of strain energy density under cyclic and random loading causing elastic–plastic strain in the material. The method consists in integration of the history of the strain instantaneous power.
Energy models for fatigue life estimation under uniaxial random loading. Part I: The model elaboration
2001
The paper contains analysis of the energy models for the fatigue life assessment under uniaxial stress state. From the simulation tests it appears that taking into account the stress and strain signs during determination of the energy density allows one to distinguish the strain energy density at the tension and compression path. Under random loading with the zero expected values for Gaussion processes it leads to the centered stochastic process. A new (basic for damage cumulation) material characteristic can be easily determined by rescaling the widely used standard stress and strain characteristics of cyclic fatigue. A new model of the fatigue life determination has been proposed. This mo…
Assessment of multiaxial fatigue behaviour of welded joints under combined bending and torsion by application of a fictitious notch radius
2004
Abstract A major problem in the assessment of the multiaxial fatigue behaviour in welded joints is the determination of local notch stresses, since the real local radii in most cases are not known. This can be circumvented by introducing a fictitious notch radius, according to Neuber and Radaj. The calculations of local equivalent stress amplitudes for welded joints (tube–tube and flange–tube) under pure bending, pure torsion and combined in- and out-of-phase bending with torsion can then be carried out by stress-based and strain energy density-based criteria. Among the investigated methods, the most reliable results are obtained with the effective equivalent stress hypothesis, an integral …