Miner's Damage Rule Research Articles

A coupled wear and crack initiation-propagation methodology for fretting fatigue life assessment in press-fitted axles

A methodology that coupled the fretting wear, crack initiation, and propagation was firstly proposed for the total fatigue life assessment of press-fitted axles. The Smith–Watson–Topper (SWT) fatigue indicator parameter (FIP), the theory of critical distance (TCD), and the Miner damage rule were adopted to estimate the crack initiation. The contour integral method and the Paris’s law were used to predict the crack propagation. Furthermore, fretting wear was simulated using the energy wear approach. The simulation results showed that TCD used in this methodology could mitigate high-stress gradient effects, and define the critical crack length for crack initiation and propagation prediction. The crack initiation prediction provided accurate information about the initial crack angle and site for the propagation estimation. The Maximum Tangential Stress criterion considering the wear effect could reasonably predict the crack propagation path of press-fitted axles. As compared with the total fatigue life predicted by the SWT FIP alone, the proposed methodology provided a better prediction result.

Method for calculating a global dynamic factor KAV in gears subjected to variable velocity and loading conditions

The present paper aims to propose a method, in ISO Standard environment, in order to calculate a single global dynamic factor KAV, replacing both KA and KV, in case of gears subjected to variable velocity and loading conditions.This procedure, based on the Miner damage rule, allows to process a given load spectrum and to calculate a value of the equivalent tangential force that includes all dynamic effects; this force value is useful for bending and pitting calculation of the service life.In this work a practical case for bending strength is presented, based on a recorded flight mission, referring to a gear box for aerospace applications. Obtained results in terms of equivalent forces and global dynamic factor values have been compared to those calculated by means of the classical ISO Standard formulae, based on the corresponding experimental data.

High cycle fatigue micromechanical behavior of dual phase steel: Damage initiation, propagation and final failure

Micromechanical analyses of various materials under high cycle fatigue (HCF) loading have been investigated previously. Experimental findings have shown that failure due to HCF occurred with different pattern comparing to the other loading conditions. The current work tries to carry out both experiments and simulations at micro scale. In this research, scanning electron microscopy (SEM) and metallography images of the specimens are taken to investigate the failure and deformation patterns in dual phase (DP) steel under high cycle fatigue loading. Failure mechanisms of DP steels are also predicted using a real representative volume element (RVE) and microstructural finite element (FE) modeling. The linear damage accumulation rule (Miner's damage rule) is used to determine the material degradation due to fatigue loading. The cyclic loading is implemented in the FE model of the microstructure by developing ANSYS parametric design language (APDL) code to obtain the damage, failure pattern and fatigue life of the RVE. It is also shown that the finite element modeling of the real RVE considering both plasticity and fatigue damage leads to acceptable compatibility between the obtained cracking patterns from SEM images (experiments) and finite element predictions.

Method for Calculating the Application Factor KA in Gears Subjected to Variable Working Conditions

The present paper aims to propose a method, in ISO Standard environment, in order to calculate the KA application factor when the nominal torque is not defined. A procedure is presented, based on the Miner damage rule, in order to process a given load spectrum and to calculate a value of the equivalent tangential force including variable amplitude effects, useful for bending and pitting life calculation. A practical case is presented, based on a recorded vehicle mission, referring to the input gear of a transfer box for industrial truck. A comparison is also given with the ISO Standard results.

On the application of the stochastic approach in predicting fatigue reliability using Miner's damage rule

ABSTRACTThe present paper investigates the application of the stochastic approach when the commonly adopted Miner's linear damage rule is implemented, both in its traditional and modified forms to include the presence of a random stress threshold (random fatigue limit), below which the rate of damage accumulation is reduced.Main steps are provided to obtain the simulated distribution of the accumulated damage under variable amplitude loading. When the stochastic approach is applied in the presence of a random fatigue limit, an additional correlation structure, which takes into account the fatigue limit value, must be introduced in the analysis. If the number of cycles to failure under constant amplitude loading is Weibull (Log‐Normal) distributed, then the corresponding accumulated damage is Fréchet (Log‐Normal) distributed.The effects of the correlation structure on reliability prediction under variable amplitude loading are also investigated. To this aim, several experimental datasets are taken from the literature, covering various metallic materials and variable amplitude block sequences.The results show that the choice of the damage accumulation model is a key factor to value the improvement in the accuracy of reliability predictions introduced by the stochastic approach.Comparison of the predicted number of cycles to failure with experimental data shows that larger errors are non‐conservative, regardless of the adopted correlation structure. When the analysis is limited to reliability levels above 80%, for these large non‐conservative errors, it is the quantile approach to be closer to actual experimental data, thus limiting the overestimation of component's life. For the experimental datasets considered in the paper, adoption of a stochastic approach would improve the accuracy of Miner's predictions in 10% of cases.

A statistical nonlinear cumulative damage rule and fatigue life prediction under random loading

For variable amplitude loading, the fatigue life estimation employing constant amplitude stress-life data and a linear Miner's damage rule is usually nonconservative. Therefore, a plastic work interaction nonlinear damage rule has been proposed to predict a more conservative fatigue life under a countable variable amplitude loading sequence. In the present paper, this nonlinear damage rule is extended to the case of continuous random loading. Order statistics and asymptotic theory of statistical extremes are employed in the analysis. It is concluded that the fatigue life prediction based on this nonlinear damage rule will be reduced by 5 to 20% compared with that based on Miner's rule. The reduction is more obvious under the condition that the plastic work interaction exponent is smaller, the material's fatigue curve slope parameter is smaller, or the number of cycles to failure is larger. These conclusions appear to be reasonable and agree with some available experimental results.

Cumulative Damage in the Low Cycle Fatigue

The authors proposed a hypothesis of cumulative damage due to the low cycle fatigue and gave the following formula for fatigue fracture criterion for the multi-stage loading test; Σ^^p__(i=1)(niΔWci)(σmaxi)α=C(σmaxp)β where ni and ΔWci are number of cycles and plastic strain energy per cycle in the i-th stage, respectively; σmaxi and σmaxp denote maximum tensile stresses in the i-th and final stages, respectively; α, β and C are material constants. Experimental data on stainless steel show that the above formula approximately holds good. The above formula is transformed into Σ^^p__(i=1)ai(ni/Nfi)=1 for multi-stage constant strain cycling test. Deviations in the experimental value of Σ(ni/Nfi) from Miner's damage rule may be explained by this formula.