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The strain‐based flex fatigue of 18 μm thick copper foil is evaluated over a wide range of strain amplitudes. Seven electrodeposited foils, four commercial grades and three experimental foils, and a commercial grade rolled foil are characterized. The fatigue life versus cyclic strain amplitude curve in the high strain amplitude (low cycle) and low strain amplitude (high cycle) regimes is developed for each foil. On the basis of fatigue life (N_f) and fatigue ductility (D_f), the low cycle fatigue performance of eight foils is ranked. Universal correlations of N_f and D_f with the uniaxial tensile strength are established. Two electrodeposited foils, experimental foil DF 8 in the high strain amplitude regime and commercial foil DF 9 in the low strain amplitude regime, have been shown to display fatigue performance comparable to that of the commercial rolled GR 8 foil.

In Part 1, background information on mechanical properties and metallurgy of solder alloys and soldered joints has been presented. In Part 2, mechanisms of damage and degradation of components and soldered joints during soldering, transport and field life have been discussed, the most important mechanism being low cycle fatigue of the solder metal. In this third part, the determination of the fatigue life expectancy of soldered joints is discussed. Accelerated testing of fatigue is needed, as the possibilities of calculations are strongly limited. A temperature cycle test under specified conditions is proposed as a standard. A model is worked out for the determination of the acceleration factor of this test. A compilation of a number of solder fatigue test results, generated in the author's company, is presented.

Aero-engine components endure combined high and low cycle fatigue (CCF) loading during service, which has attracted more research attention in recent years. This study aims to construct a new framework for the prediction of probabilistic fatigue life and reliability evaluation of an aero-engine turbine shaft under CCF loading if considering the material uncertainty.

To study the CCF failure of the aero-engine turbine shaft, a CCF test is carried out. An improved damage accumulation model is first introduced to predict the CCF life and present high prediction accuracy in the CCF loading situation based on the test. Then, the probabilistic fatigue life of the turbine shaft is predicted based on the finite element analysis and Monte Carlo analysis, where the material uncertainty is taken into account. At last, the reliability evaluation of the turbine shaft is conducted by stress-strength interference models based on an improved damage accumulation model.

The results indicate that predictions agree well with the tested data. The improved damage accumulation model can accurately predict the CCF life because of interaction damage between low cycle fatigue loading and high cycle fatigue loading. As a result, a framework is available for accurate probabilistic fatigue life prediction and reliability evaluation.

The proposed framework and the presented testing in this study show high efficiency on probabilistic CCF fatigue life prediction and can provide technical support for fatigue optimization of the turbine shaft.

The novelty of this work is that CCF loading and material uncertainty are considered in probabilistic fatigue life prediction.

The purpose of this study is to investigate the results of reinforcing fibre metal laminates with glass fibres under low-cycle fatigue conditions in a limited number of cycles.

The tests were carried out on open-hole rectangular specimens loaded in tension-tension at high load ranges of 80 and 85 per cent of maximum force determined in static test, correspondingly. The number of cycles for destruction has been determined experimentally.

By means of microscopic observations, it was possible to determine the moment of crack initiation and their growth rate. Furthermore, it was possible to identify the impact of reinforcing fibre orientation in composite layers, material creating the metal layers, on fatigue life and on nature of crack propagation.

This work validates the possibility of increasing the resistance of fibre metal laminates to low-cycle fatigue by modifying the structure of the laminate.

The resistance of fibre metal laminates on low-cycle fatigue is not widely described and the phenomena occurring during degradation are poorly understood.

With the fatigue ductility test the ductility of metallic foils and flexible metal foil/dielectric laminates can be determined. Ductility together with tensile strength allows prediction of the fatigue behaviour of flexible printed wiring (FPW) in both the low‐cycle/high‐strain (ductility dependent) and the high‐cycle/low‐strain (strength dependent) ranges. However, for laminates and FPW with Kapton as the dielectric the standard fatigue ductility test method does not produce the expected results and flex life predictions deviate from experimental results. The results of a study to determine the cause of this anomalous behaviour of Kapton FPW and to find correlative correction procedures are reported. Corrections to account for both the cyclic strain‐hardening of rolled annealed copper foil and the Kapton/adhesive/copper interactions for asymmetric single‐sided FPW are presented. With these corrections the ductility determination for copper foil laminated to a Kapton substrate using the fatigue ductility test produces good results, and the fatigue life of symmetric Kapton FPW can be predicted from the copper foil properties. The underlying mechanisms for the strong deviational flex behaviour of asymmetric single‐sided FPW could not be identified. The recommendation is made that for high‐cycle flex applications the FPW construction be precisely symmetrical. FPW made from copper‐clad Kapton with rolled annealed copper foil is the overwhelming choice and it is important that one has proper acceptance criteria at incoming inspection and that a valid prediction methodology for FPW flexural resistance and fatigue behaviour is available.

Solder joint failure history has generally been assumed to follow a straight line when plotted as a lognormal or 2‐parameter Weibull distribution. Test results presented here show that a deviation from straight‐line behaviour occurs at low percentage failure probabilities. This indicates that solder joint failure history is more correctly characterised as a 3‐parameter Weibull distribution with a failure‐free period of life for true wearout failures. The solder joint failure distribution characteristic is also affected by applied strain. Lower strain, in addition to increasing median life, also improves the distribution such that the number of cycles‐to‐first‐failure is increased compared with the median cycles‐to‐failure. The ratio of cycles‐to‐first‐failure/median cycles‐to‐failure and apparent Weibull slope increases as strain decreases in a predictable manner. The effects of part elevation, part size, solder joint volume and shape, conformal coating, temperature differential, and alternative board materials are also presented with test data showing the effect of variation of these parameters.

Scholars mainly propose and establish theoretical models of cumulative fatigue damage for their research fields. This review aims to select the applicable model from many fatigue damage models according to the actual situation. However, relatively few models can be generally accepted and widely used.

This review introduces the development of cumulative damage theory. Then, several typical models are selected from linear and nonlinear cumulative damage models to perform data analyses and obtain the fatigue life for the metal.

Considering the energy law and strength degradation, the nonlinear fatigue cumulative damage model can better reflect the fatigue damage under constant and multi-stage variable amplitude loading. In the following research, the complex uncertainty of the model in the fatigue damage process can be considered, as well as the combination of advanced machine learning techniques to reduce the prediction error.

This review compares the advantages and disadvantages of various mainstream cumulative damage research methods. It provides a reference for further research into the theories of cumulative fatigue damage.

The investigations provide a basis for the optimization of the alloy 6061-T6 friction stir welding (FSW) process to improve the mechanical properties of welded joints.

The local deformation of the FSW joint in tension and fatigue test were experimentally investigated by digital image correlation (DIC) technique.

The local stress-strain behaviors of the sub-regions show that the plastic strain always concentrated at the heat affected zone (HAZ) on the advancing side both in tension and high cycle fatigue and eventually leads to the final fracture. The evolution of the plastic strain at very low stress is extremely slow and accounts for most of the total fatigue life. However, the local deformation exhibits a sudden increase just before the fatigue failure.

Based on the experimental data, the result indicates that the HAZ is the weakest zone across the weld and the strain localization in high cycle fatigue is very harmful and unpredictable for the FSW joints.

The purpose of this paper is to consider an approximate model of accumulation of microdefects in a material under repeated loading which makes it possible to define theoretical parameters of the fatigue failure (durability, fatigue limit, etc.). The model is involving the relevant law of distribution of ultimate (yield) stresses in the material of these members in combination with the basic characteristics of main mechanical properties of a material (ultimate and yield stresses and associated standard deviations).

The model of fatigue failure of brittle and elastoplastic materials based on the use of the structural-probabilistic approach and up-to-date ideas on the mechanism of material fracture is proposed. The model combines statistical fracture criteria, which are expressed in terms of damage concentrations, with the approximate model of microcrack accumulation under repeating loading of the same level. According to these criteria, the fatigue failure begins with the accumulation of separation- or shear-type microdefects up to the level of critical values of their density.

The failure mechanism is associated with the accumulation of dispersed microdamages under repeated loading. The critical value of the density of the microdamages, which are identified with those formed either by separation or shear under static loading in consequence of simple tension, compression or shear, is accepted as the criterion of the onset of fatigue failure. The fatigue being low-cycle or high-cycle is attributed to accumulation of shear microdamages in the region of plastic deformation in the former case and microdamages produced by separation under elastic deformation in the latter one.

The originality of the paper consists in the following. The authors theoretically define parameters of the fatigue failure (durability, fatigue limit, etc.) using the model in combination with the statistical failure (yield) criteria appearing in the damage measures. The constructed fatigue diagram has discontinuities on the conditional boundary dividing domains with the shear-type and separation-type fractures of structural elements. Such results are supported by the experimental results.

The purpose of this paper is to perform experiments on a full scale turbine blade attached to a part of actual turbine disc at elevated temperature, which can accurately predict the life of a fir‐tree contact under high cycle fatigue (HCF)/low cycle fatigue (LCF) combined loading. Moreover, the effect of shot‐peening on the fatigue lives of the turbine attachments is investigated experimentally by comparing those of unpeened ones.

An experimental system for a full scale turbine blade attached to a part of actual turbine disc at elevated temperature is established in this paper, with a new HCF/LCF combined loading scheme and a design of blade clamp. The new combined fatigue loading method achieves a noninterfering treatment of the high cycle and low cycle loading by placing low cycle loading exerting point to the back of the mortise. Then fatigue tests were performed on six used turbine components to investigate the effect of shot‐peening on fatigue life compared with the unpeened ones.

This test system ingeniously achieves HCF/LCF combined loading of the full scale turbine component, and a special design of the blade clamp successfully simulates the stress field of the turbine blade. Experimental life data show that the shot‐peening process greatly improves the used turbine fir‐tree attachment's life.

The present study provides an experimental method to simulate HCF/LCF combined loading of a full scale fir‐tree turbine attachment at elevated temperature at laboratory.

Compared with the unpeened turbine components, the fatigue lives of the shot‐peened ones are increased greatly. Mean life of the shot‐peened turbine attachment is 5.23 times longer than that of the unpeened.