Evaluate Fatigue Behavior Research Articles

Characterization of compressive fatigue behavior and acoustic emission analysis of Ti6Al4V cellular lattice materials fabricated by laser powder bed fusion

AbstractThis study investigates the mechanical properties and fatigue performance of Ti6Al4V cellular lattice materials (CLMs) featuring five distinct unit cell types (BCC‐Z, BCC, Octet, Truncated cuboctahedron [TCO], and Trabecular) at a relative density of 25%. Compression tests were conducted to assess static properties, including Young's modulus and yield strength. Subsequently, compression–compression fatigue tests (R = 0.1) were performed to evaluate fatigue behavior. Acoustic emission analysis was employed during static and fatigue tests to explore the potential for failure prediction. Results reveal that BCC‐Z and TCO exhibit slightly higher Young's moduli, surpassing 20 GPa, while BCC, Octet, and Trabecular display moduli ranging from 6 to 12 GPa. Regarding normalized fatigue behavior, BCC‐Z demonstrates superior fatigue resistance, followed by TCO. Notably, the acoustic emission parameters significantly correlate with the unit cell type. Lastly, a strong relationship between the initiation of failure and changes in acoustic emission parameters is observed, establishing a meaningful link between the static and fatigue curves and acoustic emission results.

Waste engine oil and polyphosphoric acid enhanced the sustainable self-healing of asphalt binder and its fatigue behavior

Asphalt self-healing capability is critical to the asphalt industry's sustainable development. The paper attempts to explore the feasibility of waste engine oil (WEO) and polyphosphoric acid (PPA) to enhance self-healing of asphalt binder and its fatigue behavior. The different proportion of WEO and PPA were mixed with asphalt to modify asphalt initially. Dynamic shear rheometer (DSR) test and linear amplitude sweep (LAS) test were adopted to establish the modulus master curve and evaluate fatigue behavior. With the aim of estimating the healing degree of asphalt binders, evaluating indicators consist of fatigue life recovery, modulus recovery and dissipated energy recovery were adopted based on fatigue-healing test. The phase state transition of asphalt binders related to temperature was determined by differential scanning calorimetry (DSC) test. Ultimately, to evaluate modification effect of different additives on asphalt binder comprehensively, radar chart method is employed. It can be concluded that the addition of PPA and WEO improves fatigue performance and self-healing of asphalt binder. As for additives with 2% PPA and 2% WEO, 1% PPA and 4% WEO, fatigue life in LAS predicted model presents extreme value, increasing by 1000% and 1150% than original asphalt respectively. The raise of anti-permanent deformation for asphalt modified by WEO/PPA can be attributed to the presence of PPA. Compared with original asphalt, a significant increase of fatigue life recovery, modulus recovery and dissipated energy recovery is observed at asphalt modified with 6% WEO regardless of PPA content. Additionally, the healing indicators increment of the original asphalt is larger than modified asphalt with the extension of the healing time. This is because most of damage of modified asphalt could recover at a relatively short time. Analysis of the DSC indicates that the two peak temperatures of original asphalt are lower than that of modified asphalt. It helps to improve self-healing and fatigue behavior of asphalt binder. Overall, a promising way to promote the sustainable development of asphalt industry is put forward.

Fatigue behavior of uncorroded non-load-carrying bridge weathering steel Q345qDNH fillet welded joints

Bridge weathering steel produced in China is being increasingly employed in bridges worldwide, Q345qNH is among the most commonly used steel grades. Fatigue behavior of uncorroded non-load-carrying fillet welded joints made of bridge weathering steel Q345qNH was explored in this paper. Fatigue tests were conducted on 10 specimens which were under 7 stress ranges, S–N curve and its lower bound of 95% survival probability were established. It was observed that the design S–N curve for non-load-carrying fillet welded joint in Eurocode 3 is suitable to evaluate fatigue behavior of this batch of specimens and offers a considerable safety margin. The influences of initial crack size, initial crack shape, initial crack location and misalignment of attachments on fatigue behavior of non-load-carrying fillet welded joints were explored, the relationship between fatigue life and initial crack size was derived. Furthermore, it is recommended to adopt a semi-elliptical crack with initial crack depth of 0.075 mm for numerical simulation when initial crack size is unknown. The fatigue test results provide reference for fatigue design of steel bridges made of coated weathering steel and serve as control to analyze deterioration of fatigue behavior caused by corrosion for corroded non-load-carrying fillet welded joints made of uncoated weathering steel.

Evaluation of fatigue behavior of asphalt binders containing reclaimed asphalt binder using simplified viscoelastic continuum damage approach

Several fatigue damage analysis approaches have been introduced for asphalt binders and mixtures. In this study, using three modifiers including softer bitumen, a rejuvenator and waste polymer modified bitumen, fatigue behavior of RAB-containing binder mixes was evaluated based on the simplified viscoelastic continuum damage mechanics (S-VECD). In addition, correlations between the S-VECD parameters and the other fatigue failure criteria were investigated. For this purpose, the time sweep test was used to evaluate fatigue behavior of various asphalt binders in controlled-strain mode. Results showed that the rejuvenator and softer bitumen had the greatest effect in terms of prioritization on the improvement of the fatigue resistance of the RAB-containing binder mixes. Moreover, the results showed that good unique relationships between plateau value (PV) and Nf50 and between rate of change of total released pseudo strain energy (GR) and Nf50 were established in the RAB-containing binder mixes. Furthermore, there was a good relationship between the two concepts of the dissipated energy approach used for determination of the PV and the dissipated pseudo strain energy approach which used for calculation of the GR values.

Evaluation of Fatigue Behavior in Dental Implants from In Vitro Clinical Tests: A Systematic Review

In the area of dentistry, there is a wide variety of designs of dental implant and materials, especially titanium, which aims to avoid failures and increase their clinical durability. The purpose of this review was to evaluate fatigue behavior in different connections and implant materials, as well as their loading conditions and response to failure. In vitro tests under normal and dynamic loading conditions evaluating fatigue at implant and abutment connection were included. A search was conducted in PubMed, Scopus, and Science Direct. Data extraction was performed independently by two reviewers. The quality of selected studies was assessed using the Cochrane Handbook proposed by the tool for clinical trials. Nineteen studies were included. Fourteen studies had an unclear risk and five had high risk of bias. Due to the heterogeneity of the data and the evaluation of the quality of the studies, meta-analysis could not be performed. Evidence from this study suggests that both internal and morse taper connections presented a better behavior to failure. However, it is necessary to unify criteria in the methodological design of in vitro studies, following methodological guidelines and establishing conditions that allow the homogenization of designs in ISO (International Organization for Standardization) standards.

Using digital image correlation to evaluate fatigue behavior of strengthened reinforced concrete beams

The fatigue behavior of reinforced concrete beams strengthened with externally bonded carbon fiber reinforced polymer (EBR) plates and near-surface mounted (NSM) bars has been investigated using a digital image correlation (DIC) technique. Displacement fields obtained from digital images recorded during specific load cycles in fatigue tests are analyzed to provide information on crack width, beam deflection and curvature, and major principal strains to enable crack detection. The results obtained in this way were compared to data gathered using conventional sensors, revealing that the DIC technique provided very accurate and detailed information, which is not possible to obtain using conventional techniques. The experimental results for plate-strengthened, bar-strengthened and unstrengthened beams are discussed.

Fatigue Behavior Analysis of Asphalt Mixes Containing Electric Arc Furnace (EAF) Steel Slag

This research was conducted in order to evaluate fatigue behavior of asphalt mixes containing Electric Arc Furnace (EAF) steel slag. After initial evaluation of the properties of EAF steel slag using X-ray Diffraction (XRD) and Scanning Electric Microscope (SEM), six sets of laboratory mixtures were prepared. Each set were treated replacing various portions of limestone aggregates of the mix with EAF steel slag. Four point bending beam fatigue tests were performed in both controlled strain and stress mode of loading at various strain and stress levels to characterize the fatigue behavior of asphalt mixes containing different percentages of EAF slag. Different approaches based on stiffness and dissipated energy were used to analyze the fatigue tests data. The results show that the inclusion of EAF in mixes improved the fatigue life considerably under both stress and strain control mode of loading. In the stress control mode, very good correlations were observed between responses and fatigue life of mixes. However, correlation coefficients in the strain control mode were relatively lower than those in the stress control mode (particularly in the tests that were based on 50% reduction of initial stiffness).

Virtual Qualification of Aeronautical Actuators: Durability Test

The aim of this paper is to highlight some significant aspects related to the dynamic simulation and virtual fatigue behavior evaluation of actuators for aeronautical use (ball screws), subjected to vibration actions, defined by specific instruction and simulating real operating conditions. In particular, it relates to the ability to run (in frequency domain) sine sweep tests simulations by avoiding classical harmonic analyses, in order to reduce the calculation time. This is possible by using a suitable transformation of the input spectra into the corresponding power spectral density (PSD) functions, to perform a faster PSD spectrum analysis and, then, reconverting the output PSD functions into simple frequency spectra, in order to accurately evaluate fatigue behavior.

Fatigue behavior of dental resin composites: Flexural fatigue in vitro versus 6 years in vivo

To evaluate fatigue behavior of direct resin composite restorations (Tetric Ceram vs. Grandio) in vitro and in vivo over an observation period of 6 years. For the in vitro part, Young's moduli (YM) were calculated and both initial (FS: flexural strength) and fatigue flexural strength (FFL: flexural fatigue limit) were evaluated in a four-point bending setup (n = 15) in distilled water at 37°C. For the in vivo part, 30 patients received 68 direct resin composite restorations of the same materials (Grandio bonded with Solobond M; Tetric Ceram bonded with Syntac). Patients revealed a minimum of two different class II restorations in different quadrants. Epoxy replicas of restored teeth were analyzed under a scanning electron microscope (SEM) at 30× magnification for fatigue characteristics, and 11 selected restorations per group were assessed for marginal fatigue characteristics at 200×. In vitro, YM was 15.7 GPa (Grandio) and 8.7 GPa (Tetric Ceram; p < 0.05), FS was 115.0 MPa (Grandio) versus 101.5 MPa (Tetric Ceram; p > 0.05), and FFL was 63.0 MPa (Grandio) versus 44.3 MPa (Tetric Ceram; p < 0.05). In vivo, no significant difference in fatigue behavior (cracks, chippings) was evaluated for the different materials under investigation. However, marginal breakdown was more pronounced under the SEM for Tetric Ceram (7.9% vs. 4.8% for Grandio; p < 0.05), but without being clinically relevant. SEM analysis exhibited distinct wear patterns after 6 years with no significant differences among materials as well. Despite higher in vitro values for YM, FS, and FFL for Grandio, clinical outcome for both resin composite materials over 6 years of clinical service was similar. Higher FFLs in vitro seem to be related to less marginal composite fractures in vivo but without any influence on clinical outcome until the 6 years recall.

Strengthening behavior due to cyclic elastic loading in Pd-based metallic glass

Nanoindentation technique was utilized to unravel the strengthening behavior of Pd-based metallic glass under elastic cyclic loading. This was conducted to ultimately evaluate fatigue behavior which is thought to be a major concern for the structural performance of bulk metallic glasses. The event of shear band formation is considered after subjecting the alloy to loading cycles in the nominal elastic regime, followed by a monotonic deep indent. In all experiments, substantial shift in the load needed to initiate a shear band (indicative of plasticity) was noted. Following prolonged cycling, a fatigue limit was observed evident by the saturation in hardening effect. By varying the amplitude of elastic loading, it appears that a critical loading is needed to initiate strengthening in the bulk metallic glass (BMG); i.e. a specific threshold need to be exceeded for the hardening effect to trigger. This was concluded following successive experiments with increasing number of cycles which proves the effect over multiple cycling. Moreover, the effect of higher loading rates becomes more significant as the successive number of cycles increases. For further assessment, comparative experiments were carried out between holding and cycling in the elastic region. These experiments suggested the necessity of cycling to achieve hardening in the alloy, as no hardening effect was observed following holding experiments. In general, strengthening effect was attributed to the possible development of regions of microplasticity due to the actuating force, without being able to detect these regions in the global load–displacement response. Additional tests were conducted to unravel the irreversibility of these cycling/hardening effects. It was found that slight recovery is possible when no resting time was introduced before the deep indent. This suggests that part of the cycling effects can be reversed which can be linked to the instability of the shear transformation zones (STZs).

Effect of Postweld Aging Treatment on Fatigue Behavior of Pulsed Current Welded AA7075 Aluminum Alloy Joints

This article reports the effect of postweld aging treatment on fatigue behavior of pulsed current welded AA 7075 aluminum alloy joints. AA7075 aluminum alloy (Al-Zn-Mg-Cu alloy) has gathered wide acceptance in the fabrication of light weight structures requiring high strength-to weight ratio, such as transportable bridge girders, military vehicles, road tankers, and railway transport systems. The preferred welding processes of AA7075 aluminum alloy are frequently gas tungsten arc welding (GTAW) process and gas metal arc welding (GMAW) process due to their comparatively easier applicability and better economy. Weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often results inferior weld mechanical properties and poor resistance to hot cracking. In this investigation, an attempt has been made to refine the fusion zone grains by applying pulsed current welding technique. Rolled plates of 10 mm thickness have been used as the base material for preparing multipass welded joints. Single V butt joint configuration has been prepared for joining the plates. The filler metal used for joining the plates is AA 5356 (Al-5Mg (wt.%)) grade aluminum alloy. Four different welding techniques have been used to fabricate the joints and they are: (i) continuous current GTAW (CCGTAW), (ii) pulsed current GTAW (PCGTAW), (iii) continuous current GMAW (CCGMAW), and (iv) pulsed current GMAW (PCGMAW) processes. Argon (99.99% pure) has been used as the shielding gas. Rotary bending fatigue testing machine has been used to evaluate fatigue behavior of the welded joints. Current pulsing leads to relatively finer and more equi-axed grain structure in GTA and GMA welds. Grain refinement is accompanied by an increase in fatigue life and endurance limit. Simple postweld aging treatment applied to the joints is found to be beneficial to enhance the fatigue performance of the welded joints.

1340 ステンレス鋼の疲労特性に及ぼす平均応力の影響(S21-6 ステンレス鋼とチタン合金の疲労,S21 金属材料の疲労特性と破壊機構)

In this study, pulsating fatigue test had been performed in order to evaluate fatigue behavior of notched structural stainless steel under applied mean stress. All specimens were made to final shape and dimensions only by machining. The main results obtained in this research are as follow; (1) Fatigue limit of applied mean stress specimens increases with an increase in compressive mean stress. (2) Applied compressive mean stresses on martensitic stainless steel are more effectively increase the fatigue limit than that on ferritic stainless steel. (3) Compressive mean stress delays crack initiation and suppresses crack propagation.

Fatigue behavior of rolled structural stainless steels

In this experiment, rotating bending fatigue test and compressive-tensile fatigue test had been performed in order to evaluate fatigue behavior of notched structural stainless steels. Two types of specimens were used in this fatigue test, i.e., a non-rolled specimen and a rolled one. The non-rolled specimens were made to final finishing shape and dimensions only by machining. The surface layer of rolled specimens was plastically 1mm deformed by roller-working. The.main results obtained in this research are as follow; (1) Fatigue limits of non-rolled specimens FSSA, FSSB, ASS and MSS are 210, 246, 260 and 485 MPa, respectively. (2) Fatigue limit of both 1 mm rolled specimens, ASS-RI and FSSB-R1, are 500 MPa. (3) The fatigue limits of rolled specimens are higher than those of non-rolled specimens due to work-hardening and residual stress effect.

Fatigue crack growth behavior of laser-processed 304 stainless steel in air and gaseous hydrogen

Fatigue crack growth test was performed to evaluate fatigue behavior of 304 stainless steel specimens with or without laser processing (welding and surface treatment) in air and gaseous hydrogen. As the crack propagation normal to the laser welding or scan direction, the laser-processed specimens exhibited a higher resistance to crack growth in the low stress intensity factor range (Δ K) than the as-received steel plates regardless of testing environments. However, the marked retardation of crack growth behavior vanished for welded specimens subjected to a 850 °C/h stress relief treatment or with a shorter distance from notch tip to the weld centerline in the test. Fatigue-fractured appearance of the steel plate tested in air was composed of mainly transgranular fatigue fracture and some flat facets, along with a small amount of intergranular fracture. While quasi-cleavage fracture and few twin boundary separations were observed for the same specimen in hydrogen. On the other hand, the lower crack growth rate of laser-processed specimens in both air and hydrogen was accompanied with rubbed areas on the fracture surfaces. It was found that the extent of quasi-cleavage fracture was related to the formation of strain-induced martensite, which would contribute to an increased fatigue crack growth rate of all specimens in gaseous hydrogen.