The interference fit surface between planetary gears and corresponding bearings in the planetary gearbox suffers from the most severe variable load during operation and is prone to fatigue failure. It is generally believed that the failure mode of the interference fit surface is only fretting wear. In this study, the fretting and slipping between the planetary gear inner hole and the bearing outer

Non-destructive testing techniques are widely applied in industry for the evaluation of quantities of interest without inflicting additional damage accumulation. Crack detection and monitoring is a prime example of where non-destructive testing is valuable. Among the variety of non-destructive testing techniques, the direct current and alternating current potential difference methods, which are based

The effect of building orientation on the very-high-cycle fatigue (VHCF) response of Ti-6Al-4V specimens produced through selective laser melting (SLM) process with three different building orientations (0°, 45° and 90°) has been experimentally assessed. The fatigue performance decreases with different building orientations from 0° to 90°. The fatigue crack origin has been found to be always an internal

This paper conducts a comparative study on mechanical properties of LMD and forged Ti-6Al-4V, focusing on uniaxial compression, tension and shear response with different strain rates, and vibration fatigue behaviors with 45-50 Hz in frequency. The micro-observation on initial microstructures and fractures explains the mechanism of lower uniaxial strength, shorter fatigue life, and larger dispersion

This study investigated the application of the life-dependent material parameter concept to stress-based fatigue criteria for fatigue life prediction under multiaxial variable-amplitude loading. Different multiaxial fatigue criteria were applied to the fatigue life calculation with fixed and life-dependent material parameters under constant- and variable amplitude loading. Uniaxial variable-amplitude

In this work, for development and sustainability of compressive residual stresses (RS) in bearing steel materials is examined. Of particular interest is the role of retained austenite (RA) transformation in fatigue performance. Cyclic torsional loading was performed for a prescribed number of cycles at specific stress levels. Specimens were then examined using X-ray diffraction techniques to observe

Due to both wave and wind fluctuations, the steel foundations of offshore wind turbines are highly submitted to fatigue. To date, current methods of fatigue design proposed in the regulations are not devoted to structural optimization and to the consideration of time-variant hazards. We propose hence an incremental two-scale model of damage in order to follow the time evolution of the damage. This

Based on the experimental results in [1], [2], a semi-empirical low-cycle fatigue life prediction model is constructed for a polyamide-6 (PA6) polymer, in which the rate dependence of fatigue life and the effect of ratchetting strain on the life are considered. Since the fatigue damage in PA6 is not only loading-cycle-dependent but also time-dependent, a function to describe the complicate effect of

In this paper, a SiMo 4.06 cast iron is subjected to Low-Cycle Fatigue (LCF) loading and Thermo-Mechanical Fatigue (TMF) loading in the temperature range between 20 °C and 650 °C. Strain-controlled experiments were performed for various strain rates, with and without a tensile strain dwell. A modified unified viscoplastic material model is proposed for simulating the temperature- and time-dependent

Small fatigue crack initiation behaviour in a series of specimens containing different sizes of micro-notch has been observed through RepliSet system during interrupted low cycle fatigue tests. From the replicating observations, very initial single crack or multiple cracks near the micro-notch area can be captured. Since then, the crack initiation life for each specimen can be determined. Computationally

Fatigue behaviour in High Cycle Fatigue (HCF) regime has been studied in a 17–4 PH steel produced by an Additive Manufacturing (AM) technique, Selective Laser Melting (SLM). The research was prompted by increasing demands of AM techniques for safety-critical engineering applications. One of the main challenges in as-built AM parts is surface roughness, which gives rise to early crack initiation due

The strength and cracking behaviour under fatigue loading of additively manufactured polylactide (PLA) was investigated experimentally to quantify and model the role of notches. These tests were run under load ratios equal to −1 and to 0. Being supported by the experimental evidence, 3D-printed PLA was treated as a linear-elastic, isotropic, and homogenous material. This allowed the use of the Theory

Crack propagation rates from isothermal and in-phase high temperature thermomechanical fatigue crack propagation tests for Inconel 792 resulted in a rather large scatter band when plotted against the linear-elastic stress intensity function ΔK. Previous observations indicated that the residual strains generated during the first few cycles in the uncracked specimen can explain, to a large extent, the

Microstructural features and defects arising from selective laser melting (SLM) determine the in-service performance of additively manufactured near-net-shape components. Here the grain type, shape, size and distribution were characterized using electron backscattered diffraction (EBSD). High-resolution synchrotron radiation X-ray computed tomography (CT) was used to quantify the population, morphology

Carbon fiber reinforced polymer (CFRP) multidirectional composite laminates are vital for moisture-prone structures where directional fatigue properties can be optimized. In this work, the tension-tension(T-T) and tension-compression(T-C) fatigue properties of hygrothermal aged [±454]S and [+45,−45, 0, 90]2S laminates were compared with virgin properties. The effect of fiber orientation and hygrothermal

The properties of the continuous-time, high-cycle fatigue model of Ottosen et al. (2008) is investigated for challenging stress states. We derive an analytical solution to the damage per cycle for cyclic, proportional stress. Numerical investigations for 7050-T7451 aluminum alloy and AISI 4340 steel alloy show exponential convergence to a constant damage per cycle for cyclic proportional stress, and

Ultrasonic fatigue tests were performed to investigate high and very high cycle fatigue behaviors of a laser additively manufactured Inconel 718 (IN718) alloy in the as-deposited condition. The results indicate that the competition failure behavior between the surface and interior crack initiation results in the separate S-N curve. Both manufacturing defects (e.g., gas pore, lack of fusion) and columnar

This paper investigated static and fatigue bending behavior of sandwich beams using glass fiber reinforced polymer (GFRP) as skins and webs while balsa wood as core The failure modes, S-N curves, load-deflection behavior and stiffness degradation were obtained and compared The results showed that the fatigue failure modes of web reinforced sandwich beams varied with the web setting and load grade The

Inherent defects induced in casting process seriously affect mechanical performance and fatigue properties of the material. Micro-structural investigations reveal that the grain size and dendrite microstructure are sensitive to casting processes and change materials property. The fatigue performance of the material decreases with porosity and is characterized by distributed voids on grain boundaries

Two-sided and simultaneous laser shock peening (TSLSP) was used to strengthen the Ti-6Al-4V titanium alloy. The fatigue crack growth rate of the specimens was investigated by fatigue test. The results show that both direct TSLSP (TSLSP-D) and indirect TSLSP (TSLSP-I) can reduce the fatigue crack growth rate by producing high magnitude compressive residual stress. The maximum fatigue life increases

Axially push-pull fatigue tests of a low-strength Cr-Ni-Mo-V steel welded joint using cross-weld specimens with two types of sampling, i.e., weld metal centered and heat-affected zone centered, were conducted up to 5 × 107 cycles at room temperature and 300 °C. Fatigue strength of heat-affected zone centered specimen was higher due to dynamic strain aging at weld metal at 300 °C and a locally mismatched

Short cracks appearing under fatigue conditions are of major concern for safety-critical components. In this paper, a computational approach based on crystal plasticity and extended finite element method is developed to predict the slip-controlled short crack growth in a single crystal nickel-based superalloy. The onset of fracture is controlled by cumulative shear strain of individual slip system

This study addresses the fatigue crack growth behaviour of a material from an old riveted steel bridge, the Portuguese Fão Bridge, based on an experimental program of constant and variable amplitude loading tests. The material under consideration is a centenary puddle iron, for which information on fatigue crack growth under variable amplitude loads is not available in the literature. Additionally

Ultrasonic fatigue testing is a relative recent fatigue study methodology that applies resonant principles for the induction of stress cycles in a specific designed material specimen. Such experimental method can apply fatigue damage at high frequencies, most commonly at 20 kHz. It was created with the main purpose of studying material fatigue life in the Very High Cycle Fatigue regime between 10E07

Thermoplastics are used in many industries with many applications and can be manufactured using different processing techniques. Multiaxial loading and non-proportionality between different loading sources are inevitable in many design applications with such materials. In this study, multiaxial fatigue behavior of extruded high density polyethylene (HDPE), polypropylene (PP), and neat polyamide66 (PA66)

This study aims at investigating the effect of defect on the high cycle fatigue behavior of polycrystalline aggregates. An explicit virtual microstructure finite element model is created to conduct fatigue simulations. Different stress-based criteria frequently applied in fatigue assessment are tested with a combination of the non-local methods. Two realizations of the non-local method are used and

This study investigates the fatigue behavior of Inconel 718 (IN718) fabricated through laser beam directed energy deposition (LB-DED) process. Fully-reversed (Rε = −1) strain-controlled fatigue tests are conducted on LB-DED IN718 specimens at 650 °C and the results are compared with those of LB-DED IN718 specimens tested at room temperature as well as the ones obtained from wrought counterparts at

The influence of creep damage on high cycle fatigue (HCF) in Alloy 617M at 973 K was investigated in the present study by devising a novel method of incorporating periodic hold at the alternating stress/maximum stress. Under such HCF-creep interaction tests, the endurance limit was found to shift downwards compared to that obtained under HCF cycling. The modified endurance limit was found to be a strong

An understanding of rate dependency over a wide range of time scales is vitally important in approximating the transient response of critical components operating in extreme environments. Many examples of viscoplastic model formulations can be found in the literature, wherein all rate dependency is assumed to occur after yielding. Such models neglect any viscous effects during elastic deformation.

Friction stir welding (FSW) produces heterogeneous microstructure in nugget zone of its joint, which should affect the fatigue responses. This work revealed the unique texture and banded structure of the Mg-FSW joint and their decisive roles on crack initiation behaviors. At higher stress levels, failures occur along the AS NZ/TMAZ boundary (AS: advancing side, NZ: nugget zone, TMAZ: thermo-mechanically

Stress-controlled multiaxial fatigue tests were carried out by using hollow cylindrical specimens of type 430 and type 316 stainless steel at room temperature. A recently developed fatigue testing machine, which can apply push-pull loading and inner pressure to the specimen was used. By combining axial and hoop stresses, a pull, an inner-pressure, a push-pull, an equi-biaxial, a square, an LT, and

This paper investigates the effect of overload and misalignment on crack propagation of laser welded T-joints. The results showed that the crack growth rates of these joints are like those of base material. For single overload, the increase of ΔK from 8.5 to 13 MPam1/2 multiplied the average retarded crack growth rate by 7.5 for R=0.4. The highest crack retardation was caused by multiple overloads

Pipeline fittings containing ferrules are used to connect sections of aircraft hydraulic pipelines. Therefore, their reliability and stability are essential. The purpose of this investigation is to better understand and analyze the sealing failure mechanism of pipeline fittings produced by pipeline vibration. Based on accelerated tests, the sealing failure mechanism and fatigue life of fittings are

In the present paper, a novel procedure for fatigue resistance assessment of fillet-welded joints under complex random loading is proposed. It consists of two consecutive steps: (1) computation of the stress tensor at the verification point; (2) evaluation of damage and, consequently, fatigue life. The procedure exploits the multiaxial critical plane-based criterion by Carpinteri et al. for random

Tests are used to verify the hypothesis “the fatigue crack growth (FCG) driving force is the effective stress intensity factor range ΔKeff”. The tests are performed measuring FCG rates in steel and aluminum C(T) and DC(T) specimens under fixed {ΔK, Kmax} loading conditions and during FCG delays induced by single overloads. Crack-opening loads Pop are redundantly measured along the crack path in all

Fretting fatigue crack propagation in aluminium strands was investigated through experimental tests and FEM simulations. Fretting fatigue tests revealed that crack nucleation predictions are not sufficient to fully predict the total strand failure, and crack arrest conditions may be reached for nucleated cracks. The geometry of arrested cracks was characterized and used to perform simulations using

In the present paper, the mode I and II fatigue fracture performance of a novel Titanium/CFRP adhesive joint is investigated. The adhesive joint under study is composed of two thin adherents, one Titanium sheet and one CFRP laminate, and is reinforced from both sides with two thick aluminum beams to increase its flexural stiffness and ensure the non-yielding of the Titanium. The interfacial fracture

In this study, a temperature dependent elastic-viscoplastic cohesive zone model is developed to predict the thermomechanical fatigue (TMF) behaviour of superalloys. The theory is based on rheological models enhanced with fatigue and creep damage variables which are micro-mechanically motivated. This cohesive law can capture monotonous, cyclic, thermomechanical, and rate dependent loads. The material

Recent works in mechanical fatigue consider that a threshold of entropy exists, the fracture fatigue entropy. In this paper, we observe the existence of a threshold of entropy and exergy in low cycle fatigue for a flat Al-2024 specimen measuring the heat generated during a fatigue test. Results are compared considering various hypotheses (1D heat dissipation with convection and radiation considered

Hot isostatic pressing (HIP) is often needed to obtain powder bed fused (PBF) Ti-6Al-4V parts with good fatigue performance. This manuscript attempts to clarify the mechanisms through which HIP treatment acts to improve high cycle fatigue performance. Several mechanisms are considered and examined against experimental data sets available in the literature. The results suggest that HIP may act most

The fatigue and fracture behavior of hard tissues are topics of considerable interest today. This special group of organic materials comprises the highly mineralized and load-bearing tissues of the human body, and includes bone, cementum, dentin and enamel. An understanding of their fatigue behavior and the influence of loading conditions and physiological factors (e.g. aging and disease) on the mechanisms

The long-term stability of cemented total hip replacements critically depends on the lasting integrity of the bond between the cement and the bone, often referred to as fixation. In vitro assessment of fatigue behaviour of cemented acetabular, as opposed to femoral, replacements is of particular interest due to the more aggressive nature of late "loosening" found in acetabular replacements, reported

Microdamage formation is a critical determinant of bone fracture and the nature and type of damage formed in bone depends on the interaction of its extracellular matrix (ECM) with the applied loading. More importantly, because bone is a hierarchical composite with multiple length scales linked to each other, the nature and type of damage in bone could also be hierarchical. In this review article, based

Although the role of fatigue failure in aseptic loosening of cemented total hip replacements has been extensively studied in femoral components, studies of fatigue failure in cement mantle of acetabular replacements have yet to be reported, despite that the long-term failure rate in the latter is about three times that of femoral components. Part of the reason may be that a complex pelvic bone structure