Numerical and experimental studies have been conducted to try to quantify the influence of Automated Fiber Placement (AFP) induced manufacturing defects on the quasi-static behavior of composite parts ranging, on the building block approach, from coupons to sub-structural parts. In more recent studies, researchers started to conduct the same investigations for fatigue load cases with the purpose of

Hydrogen-assisted, fatigue crack-growth in pure iron within a low stress-intensity range was ascribed to the emergence of intergranular fracture, the significance of which was emphasized by increased hydrogen-gas pressure, while conversely mitigated by an elevation of test temperature. Based on conventional thermodynamic theory, a single parameter, GB hydrogen-coverage (θx), was used to derive a systematic

The investigation of the carbon fibre reinforced plastic components under vibration fatigue testing is known to be challenging; as it involves the analyses of both the mechanical response and the inherent self- heating behaviour which emerges due to the high-frequency testing. The paper will firstly address an open question about the so-called critical event, which is a sudden change in one of the

The influence of graphite morphology on the corrosion-fatigue mechanism in the cast compacted graphite iron SiMo1000 is investigated. Two batches of SiMo1000 with the same chemical composition but different nodularity are tested using low-cycle-fatigue tests in argon and a synthetic exhaust atmosphere at 800 °C. Decreased graphite nodularity is found to significantly reduce the corrosion resistance

Fretting fatigue is a combination of fatigue and micro-sliding due to fretting. The aim of the present work is to estimate crack initiation direction, endurance strength and lifetime of aluminium 7050-T7451 alloy specimens. The experimental campaign examined is devoted to investigate the role of the mean bulk stress on fretting fatigue behaviour. The above estimations are performed by using the Carpinteri

Fatigue crack growth (FCG) behaviour of austenitic stainless steel SS316L(N) has been evaluated at different temperatures in the threshold and Paris regimes. Comparison of crack closure corrected data from ASTM tests and the data from constant Kmax test at 300 K brings out the inherent inadequacies of crack closure correction in describing the FCG behaviour. An attempt to describe the temperature effects

This study focuses on the influence of defect density on the sizes of the critical defects responsible for fatigue failure in AlSi7Mg0.6 alloy produced by Selective Laser Melting. Samples having similar microstructures and different defect densities were obtained combining Hot Isostatic Pressing and T6 treatments. Defect populations were analyzed using X-ray tomography, and fatigue tests were performed

In the present study, the finite element method was applied to model the fatigue behavior of glassphalt and conventional mixtures. In order to assess the efficiency level of the presented model, all mixtures were tested using 4-point bending test. Accordingly, it can be seen that there is high consistency between the laboratory results and outputs of 3D finite element model presented in this study

Redistribution of residual stress during crack growth in butt welded joint of Al5083-H111 was studied. Furthermore, the effect of post weld heat treatment and removing the weld reinforcements on fatigue crack growth rate was investigated. Three dimensional simulations of welding process and fatigue crack growth were conducted. It was shown that removing the weld reinforcements causes an increase in

A model to predict fatigue crack growth (FCG) for small-scale yielding (SSY) and non-SSY conditions where J-integral applies is established. The ΔJ-characterized elastic-plastic fracture mechanics (EPFM) analysis is performed based on a rearranged FCG process to achieve the crack-tip geometry and stress state. The root stress of blunted crack and the FCG rate are calculated from the cycle-wise local

Considering the unconvincing results produced by probability theory when dealing with small sample data, this paper introduces uncertainty theory (a branch of axiomatic mathematics parallel to probability theory) to model and estimate the uncertainty of fatigue life with the small sample of fatigue test data. A new method called α-S-N curves is firstly proposed to describe the relationship between

The fatigue crack propagation (FCP) behavior of Inconel 718 alloy manufactured by laser powder bed fusion (L-PBF) was studied at 25 and 650°C, and compared to those of conventionally processed counterpart. The FCP rates of L-PBF Inconel 718 alloy were found to be significantly higher than those of conventionally processed counterpart at 25°C in low and intermediate ΔK regimes. The FCP rates decreased

Cornering fatigue test of an automotive wheel is one of the essential tests to ensure the structural integrity of a wheel disc. Forming operation of wheel disc introduces forming history such as thickness reduction, pre-strain, and mean residual stresses. In this work, a methodology is proposed to consider the factors affecting the cornering fatigue performance of DP600 automotive wheel disc. The cyclic

Low-cycle fatigue tests were performed on metastable austenitic steel at two initial material states, the as-received, with a high crystal defect density, and the solution treated one, with fewer crystal defects. Cyclic curves have shown different hardening behavior depending on the initial material states. To understand these differences, the back and friction stresses were studied from the hysteresis

The influence of variable load spectra in the fatigue crack growth (FCG) was analyzed. A 4.1% interference was pre-set to some specimens by an expansion operation. As-drilled hole and hole expanded specimens were subjected to FCG tests under a combination of baseline cyclic loading and periodic overloads or underloads applied. Fatigue life was of approximately 1 million of cycles for the as-drilled

The application of fracture mechanics to the determination of the fatigue behavior of weldments is discussed with the focus on classic fatigue, i.e., the overall fatigue life and the fatigue strength in terms of an S-N curve and the endurance limit. The following issues are addressed: specific features of short fatigue crack propagation, an adequate initial crack size, multiple crack propagation and

We have studied here the high cycle fatigue properties and sub-surface fatigue crack initiation mechanism in advanced bainitic steel subjected to conventional bainitic austempering (BAT) and novel “disturbed” bainitic austempering (DBAT) processes. The retained austenite in DBAT steel mainly exhibited ultrafine film-like morphology, whereas a considerable amount of coarse blocky retained austenite

Four different types of dissimilar laser beam welded joints made of additively manufactured AlSi10Mg and conventionally manufactured EN AW-6082 T6 in 2 mm thickness have been assessed by the nominal and notch stress approach. Fatigue results for butt joints and lap joints with fillet welds fulfil the lowest fatigue class for conventional aluminium welds of FAT 12. Conventionally welded lap joints,

Tensile and fatigue behaviors of selective laser melted titanium alloy were investigated in the as-built condition. The alloy has a high defect density, and its tensile properties are comparable to those of wrought alloys, but the fatigue strength is significantly reduced. The FGA plastic zone is similar to the martensite laths width. The critical size of fatigue failure is analyzed by the K-T diagram

Rolling contact fatigue cracks shorten rail service life, and increase costs of rail maintenance and replacement significantly. The aim of the present study is to investigate the effect of residual stresses induced by manufacturing and repeated wheel-rail contact on fatigue crack initiation in rails. To this end, three-dimensional finite element models of rail on-line heat treatment, rail straightening

Fully-reversed strain-controlled tests have been performed on AZ31B magnesium alloy extrusion at room temperature, 100 °C, and 200 °C. Different fatigue life prediction models including Coffin-Manson-Basquin, Smith-Watson-Topper, and Jahed-Varvani were applied to predict the fatigue life. According to the shape of the hysteresis loops at half-life, by increasing the test temperature to 200 °C, the

Micro scratch with depth and width of micron expresses a significant influence on fatigue life. However, little literature is available on modelling the effect of micro scratch on the fatigue life of TC17 titanium alloy. In this paper, the geometric characteristics of micro scratch, especially depth and width, were obsevered and measured. Then, fatigue experiment was conducted to obtain the corresponding

In this paper, the stress concentration factors (SCFs) in tubular T/Y-joints reinforced with fiber reinforced polymer (FRP) are investigated. A total of 134 3-D FE models was generated and analyzed under compressive load. The effect of FRP layers and joint geometry on the SCFs and the SCF ratio of the reinforced to the unreinforced joints were investigated through a parametric study. Results showed

The cyclic behaviour and fatigue crack initiation in low cycle regime of dual phase (DP) steel grade 590 were characterized. Experimental strain-controlled tension–compression tests and corresponding simulations using representative volume elements were carried out. The Chaboche kinematic hardening parameters were determined for each individual phases. The damage model based on accumulated inelastic

This study presents an experimental and theoretical investigation into the bond-slip relation of a CFRP-to-steel bonded interface under cyclic loading. It was observed that the peak interfacial shear stress during cyclic loading was lower than that during monotonic loading. A damaged-plasticity-type bond-slip relation was developed to model the constitutive behavior of the bonded interface under quasi-static

A new fatigue crack growth rate model is proposed considering overload effect, which could quantitatively describe the crack growth rate considering overload from variable-amplitude load. Residual stress intensity factor Kq caused by overload was put forward by defining stress ratio Rc and obtained by XFEM. Three typical overload situations are studied and reappearance of the threshold stage was elaborated

Effects of surface mechanical attrition treatment (SMAT) on fatigue performance of a 7075-T6 aluminium alloy were studied in high cycle fatigue (HCF) and very high cycle fatigue (VHCF) regimes. Fatigue test results showed that SMAT can improve fatigue strength in HCF regime, but decrease it in VHCF regime. Fracture surface observations indicated that the low SMAT intensity is quite optimal, which can

Based on the metallographic observation, the microstructure evolution of nickel-based single crystal superalloy under thermomechanical fatigue (TMF) loading is investigated, and respective phenomenological models of damage and rafting are developed. Considering that the deformation behaviour of material is closely related to their microstructures, new variables involving rafting evolution are incorporated

This study experimentally analyzed the influence of squeeze force and initial fit tolerance on the fatigue property of a riveted aircraft lap joint. All specimens were prepared under load control and tested under six levels of fatigue loads. The results showed that an initially oversized rivet might be detrimental to fatigue-life improvement. Increasing the squeeze force within an allowable range could

To increase the prediction accuracy of small-number sample life data, improved backward statistical inference approach (ISIA) was formulated using the modified distribution coefficients while fitting the fatigue probabilistic S-N (P-S-N) curve. Based on the search path searching for fatigue parameters, the novel scheme captures the optimal coefficients that can efficiently correlate the life distribution

The fatigue properties of the original, 1%, 2%, and 3% plastic pre-strained welded joints of X80 pipeline steels were tested to find the effect of plastic deformation on the service of pipelines. Results showed that the fatigue cracks growth period remarkably decreased with the increasing plastic pre-straining extent, reducing the safety of pipeline transportation. The decrease was caused by the cleavage

Post-weld treatments can enhance the fatigue strength of weldments by means of improving their geometry or residual stresses, or both. In this study, the fatigue strength of TIG-dressed non-load-carrying cruciform joints made of ultra-high-strength steel were analyzed using stress-based approaches, i.e. nominal, structural, and effective notch stress (ENS) methods, and a multi-parametric approach,

The in-service safety of railway axles is a very important engineering challenge, as it has a large impact not only from the economic point of view of the railway operator, but it has cascading effects on supply chains, loss of work productivity, and, in the most serious cases, loss of life. It is, therefore, vital that the structural integrity of such components is known, during their lifecycle, with

A new in-situ biaxial creep-fatigue testing system was built to study the creep-fatigue interaction of Alloy 617, a nickel base alloy with potential structural applications in the Very High Temperature Reactor, up to 70 MPa at 950 °C. The results show that creep-fatigue life of Alloy 617 is reduced with increasing hold time and the cracking mode seems to be intergranular in all creep-fatigue samples

The effects of pore size and position on the local stress are characterized by a parameter PdH. This parameter is then introduced into the elastic fatigue damage model to equivalently reflect the influence of pore. The proposed fatigue damage model is numerically implemented to predict fatigue lives of the joints with different pores, and the results agree well with the experimental data. The sensitivity

The International Institute of Welding published IIW-recommendations for the HFMI-treatment, which covers fatigue assessment procedures and quality assurances guidelines. This paper contributes to the validation of the detrimental effect of high R-ratios on HFMI-treated cover plate specimens made of high-strength steel S700. Applying the nominal stress approach, the recommended S/N-curves agree well

Characterization of microstructurally small fatigue crack growth behavior for two aluminum alloys, AA7065 and AA2099 were quantified using a surface replication process for the first time. In addition, scanning electron microscopy analysis revealed that for AA7065, crack initiation was caused by either voids or intermetallic particles. Whereas, for the AA2099, crack initiation was caused by persistent

According to the existing experimental investigation on the ratchetting-fatigue interaction of SUS301L stainless steel butt-welded joint, a new life-prediction model addressing the important role of ratchetting is developed based on the ductility exhaustion theory (DET) and continuum damage mechanics (CDM). The total ductility damage is assumed to consist of fatigue ductility and ratchetting ductility

The correlation between microstructural evolution and low cycle fatigue behavior of SA508-IV steel were investigated. The fatigue tests of specimens with different tempering times were performed under the strain amplitudes of ±0.45% and ±0.6% at 300 °C, respectively. The experimental results showed that the more and more islands which were martensite/austenite islands (M/A islands) in granular bainite

Rolling contact fatigue is the main cause of failure in bearings. Among other factors, damage phenomena are related to material properties and manufacturing processes. The damage evolution might be affected by microinclusions present in the material. This influence is related to composition, dimension, shape and location of microinclusions. The relation between microinclusions and fatigue life is investigated

Elevated fatigue behaviors of resin matrix composites are considerable key to the application of aeroengine that requires fatigue resistance at elevated temperature. However, undeniably, very few studies are focused on this issue, thereby resulting in limitation applications of resin matrix composites in aeroengine components, i.e. blades and case. In this work, the fatigue responses of layer-to-layer

The combined effects of low-temperature nitriding (LTN) and cold rolling on the microstructure of commercially pure titanium (CP titanium) were investigated. The grain size of the LTN-treated CP titanium decreased with increasing thickness reduction due to the cold rolling pre-treatment and with decreasing the nitriding temperature. The fatigue limit for the nitrided CP titanium depended on the grain

Buttering layer (BL) was used to weld two ultra-supercritical turbine rotor steels. Low-cycle fatigue behavior of different regions in the dissimilar metal welded joint (DMWJ) was compared and evaluated at 280 °C. Microstructure, fracture and weak link were observed by OM, SEM, EDS and TEM. BL had lower fatigue life than weld metal (WM) and base metals (BMs). Weld zone showed cyclic softening characteristic

The impact of a controlled surface imperfection on the low-cycle fatigue life in two different steels is investigated. After introduction of a single imperfection with a depth varying from 50 to 350 µm in cylindrical samples, fatigue tests were conducted under fully-reversed total axial strain control in air at ambient temperature. It is shown that the fatigue life is significantly reduced, even in

This paper presents both experimental and analytical investigations into weld root cracking behaviors in load-carrying high-strength aluminum alloy cruciform joints. In test specimen preparations, electric spark machining was used to ensure weld penetration consistency. An analytical weld throat stress model is proposed for determining the maximum opening stress state and its weld throat angle. Its

Severe wheel rolling contact fatigue (RCF) has been observed on two types of high-power AC locomotives with CO-CO axle arrangement and running in complicated environments in China. This RCF occurs as continuous lateral surface cracks in the zone approximately centered at the nominal rolling circle of wheels and can propagate downward up to 14.5 mm deep. To figure out the causes, field observations

Impact damage are critical for damage tolerance assessment of high-speed train axles. Flying ballast impact damage on railway axles produce geometry discontinuities, which become preferential sites for fatigue crack initiation and usually lead to premature failure. According to this, the formation of surface impact damage and its influence on structural integrity of induction hardened S38C axles are

This paper investigates the effects of degassing, curing and post-curing conditions on the tensile quasi-static and fatigue behavior of a cold-curing structural epoxy adhesive. Quasi-static experiments performed at standardized and high displacement rates similar to those imposed to the material under fatigue loading, in order to derive comparable results from both loadings, and tensile-tensile fatigue

Non-conventional machining processes, such as the Electrical Discharging Machining (EDM) offers the possibility to machine very hard materials with great potential to generate complex geometries. However, the EDM process involves significant microstructural changes in the as machined surfaces, which are known to have a significant impact on fatigue behaviour of mechanical parts. This study aims at

This paper presents the results of fatigue tests combined with conformal contact, non-conformal contact and simple fatigue carried out on Ti-6Al-4V sheet specimens under externally remote bending load. A special fretting fatigue test rig was proposed to focus on two different fretting modes fatigue test simultaneously between non-conformal contact and conformal contact. The test results showed that

The sensitivity of the fatigue limit of an additively manufactured, Ni-based superalloy 718 sample to surface finishing conditions and solute hydrogen was investigated via a series of tension–compression fatigue tests. The results revealed that neither defects nor hydrogen diminished the fatigue limit of the sample. The high defect tolerance of this material is attributed to a large unit of crack initiation