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The purpose of this paper is to investigate the fatigue crack growth (FCG) under random loading using analytical methods.

For this purpose, two methods of cycle-by-cycle technique and central limit theorem (CLT) were used. The Walker equation was used to consider the stress ratio effect on the FCG rate. In order to validate the results in three random loading group with different loading levels and bandwidths, the results of the analysis, such as the mean lifetime of the specimen and the average crack length were compared with the test results in terms of the number of loading cycles.

The comparison indicated a good agreement between the results of the analysis and the test. Further, the diagrams of reliability and the probability of failure of the specimen were obtained for each loading group and were compared together.

Applying the cycle-by-cycle and CLT methods for the calculation of fatigue reliability of a CT specimen under random loading by the Walker equation and comparing their results with each other is not observed in other researches. Also in this study, the effect of the loading frequency bandwidth on lifetime was studied.

The purpose of this study is to show how gradual strength degradation of metal beams under cyclic bending up to fatigue failure is simulated based on a new elastoplasticity model free of any yield criterion.

A new approach is proposed toward accurately and explicitly prescribing evolution of non-uniform stress distribution on beam cross-section under cyclic bending and, as such, gradual degradation of the bending strength can be directly determined.

Explicit results for the bending response in a whole cyclic process up to fatigue failure are obtained and the fatigue characteristic curve is for the first time simulated directly between the curvature amplitude and the cycle number to failure.

First, explicit and accurate determination of the non-uniform stress distribution on beam cross-section is achieved with asymptotic softening effects. Second, degradation of the bending strength can be directly deduced cycle by cycle. Finally, the relationship between the bending moment and the curvature is calculated using new and efficient numerical algorithms, thus bypassing usual time-consuming calculations with finite element procedures. Numerical results are presented and in good agreement with experimental data.

This study aims to predict the unstable period-1 orbit (UPO-1) of DC–DC converters and find analytical expressions to describe it.

Nonlinear dynamical phenomena of a peak–current–mode controlled direct current–direct current (DC–DC) Boost converter are discussed briefly first. Then fast fourier transform (FFT) analysis of state variables under different dynamic states is provided, and the characteristic of the harmonic content in different states is summarized. Following these, a scientific hypothesis on the harmonic content of the UPO-1 is presented, and the Equivalent Small Parameter method is adopted then, thus analytic-form expressions of the UPO-1 can be derived.

According to results of theoretical analysis, numerical simulations and experiments, this paper illustrates that, like stable period-1 orbit, the UPO-1 is also made up of the DC component and harmonics with integer times of switching frequency.

This work provides an unreported approach for extracting the UPO-1 of DC–DC converters, which is mainly based on predicting the harmonic structure information of the orbit. According to experimental parts of the work, it shows that the stabilizer can be designed easier by using the proposed method. Additionally, from a broader perspective, the results could also have implications in a wide class of forced oscillation systems.

The purpose of this paper is to determine the effects of fatigue on fused deposition modeling rapid prototyped acrylonitrile butadiene styrene (ABS) materials.

FDM dog bones based on UNI EN ISO 527‐1 (1997) were tested at 100, 80, 60, and 40 per cent nominal values of the ultimate stress for nine different print orientations. The samples were cyclically stressed in a tensile tester at 25.4 mm/min (extension) and relaxed at 12.7 mm/min.

Although FDM ABS has a tensile strength that is relatively close to that of the bulk material, up to 80 percent, its ability to absorb energy before fracture has a tremendous amount of room for improvement. FDM ABSplus (P430) material properties are noticeably more isotropic than the predecessor, ABS (P400). The ABSplus fractures in the order of thousands of cycles at 40 percent of ultimate stress load, while the ABS exhibits the similar cycle limits at 60 percent of its ultimate stress load.

FDM ABS parts are limited in fatigue characteristics even though they exhibit similar ultimate stress limits as with bulk materials, warranting further research in improving FDM parts expected to experience cyclical loads.

This paper adds knowledge to the limited fatigue data in literature for FDM ABS. It investigated the load cyclic data of fused deposition modeled ABS through analyzing its cycle‐by‐cycle strain energy, providing another means of identifying the fatigue characteristics of materials.

This paper describes progress on the development of theoretical models required for studying failure mechanism, crack initiation and growth around the boreholes driven by hydrofracturing processes in Hot Dry Rock (HDR) reservoirs of geothermal energy. Due to the importance of the stress intensity factor concept (K) in Fracture Mechanics, some advanced modeling techniques for accurate and fast determination of K for relevant problems are proposed. Alternative tools to deal with stress intensity factor determination are developed and assessed from the points of view of accuracy and computational cost. We concentrate on residual strength, crack initiation and crack growth as a means to model and understand experimentally observed behaviors. Several modeling methods such as compounding and weight function techniques, and boundary and finite element modeling for stress intensity factor calculation are discussed. Further to reviews of those techniques, work performed included (i) developing alternative solutions to deal with boundary‐to‐boundary interaction when using the compounding technique, (ii) relating the precision of K calculations with the level of precision of the crack opening displacement of a reference solution, in order to assess the precision of weight function technique, (iii) modeling relevant geometries using the finite element method (FEM), (iv) working on the implementation of direct stress intensity factor K determination in the Higher Order Displacement Discontinuity Method (HODDM), and (v) developing tools to deal with residual stress fields around the boundary of the hydraulically pressurized boreholes.

In this work, the cohesive zone model (CZM) developed by some of the authors to simulate the propagation of fatigue defects in two dimensions is extended in order to simulate the propagation of defects in 3D. The paper aims to discuss this issue.

The procedure has been implemented in the finite element (FE) solver (Abaqus) by programming the appropriate software-embedded subroutines. Part of the procedure is devoted to the calculation of the rate of energy release per unit, G, necessary to know the growth of the defect.

The model was tested on different joint geometries, with different load conditions (pure mode I, mode II pure, mixed mode I/II) and the results of the analysis were compared with analytical solutions or virtual crack closure technique (VCCT).

The possibility to simulate the growth of a crack without any re-meshing requirements and the relatively easy possibility to manipulate the constitutive law of the cohesive elements makes the CZM attractive also for the fatigue crack growth simulation. However, differently from VCCT, three-dimensional fatigue de-bonding/delamination with CZM is not yet state-of-art in FE softwares.

Describes a computational environment based on cellular automata and genetic algorithm principles. This kind of approach is useful in a large set of applications, particularly in biological models, including those related to theoretical ecology. The program runs on an IBM compatible personal computer with a visual genetic algorithm display. It would be preferable to have at least a 80386‐based machine to take advantage of its speed of processing. It is menu‐based oriented to facilitate its use by non‐experts, and permits the interference by the researcher in many environmental and behavioural parameters, allowing many kind of studies. Illustrates the program′s capabilities by applying it to a set of simulations in order to demonstrate their effect on the evolution of the biological population.

The use of frequency output for measurement transmission remains common in the design of smart transmitters. Conventional methods of frequency generation, based on counting clock cycles, have a precision which is inversely proportional to the frequency to be generated. Consequently, frequency output precision could be much lower than the measurement precision. This paper describes a simple frequency generation technique which, when implemented in low‐cost hardware, provides a precision of 10⁻⁶ per cent for all frequencies. The method represents an intermediate non‐available frequency by dithering between two exact frequencies. Averaging over some reasonably short timescale provides the desired frequency to high precision.