Compressive Fatigue Research Articles

Contribution of the Self‐Heating Method in the Characterization of the Fatigue Damage of Materials With Defects Resulting From Additive Manufacturing

ABSTRACTThis paper investigates the ability of the self‐heating method to characterize the fatigue behavior of 316L stainless steel produced by Laser Powder Bed Fusion. Nearly dense cylinders are built vertically using various process parameters corresponding to various volumetric energy densities. Fatigue specimens are then machined from these cylinders and polished. Fully reversed tension–compression fatigue tests (R = −1) are conducted. The self‐heating method is used for the estimation of the fatigue limits. These fatigue limits are compared to results obtained from S‐N curves in the high cycle regime. Whatever the set of process parameters, the self‐heating curves show three distinct domains of heat dissipation. Thanks to microstructure analysis, fractographic observations, and correlations with S–N curves, these domains can be closely linked to damage mechanisms associated or not with defects.

Effect of initial temperature damage on the static and fatigue performance of all-lightweight shale ceramsite concrete

The effects of initial temperature damage on the static and compressive fatigue properties of LC30 all-lightweight shale ceramsite concrete (ALWSCC) were studied. The curing conditions ranged from -5 °C to -30 °C without antifreeze, with an elevated temperature range of 100 °C to 400 °C applied after 28 days of standard curing. We tested the static strength, elastic modulus, and stressstrain curves of ALWSCC, as well as its uniaxial compression fatigue life and ƐN curves under different stress levels. The credibility of data from only three test samples per condition was statistically analyzed, and we explored how temperature, aggregate properties, and concrete pore structure affect performance. The results indicate that the impact of temperature on the static and fatigue performance of ALWSCC can be described by a unified damage model. The Hillerborg characteristic length effectively captures the brittleness induced by temperature changes. Using the two-parameter Weibull equation and various fatigue equations that account for failure probability and temperature, the fatigue life predictions were accurate. Although low and high temperatures affect ALWSCC differently, temperature effects combined with static and fatigue loads further accelerate its deterioration.

An Integrated Approach for Prognosis of Remaining Useful Life for Composite Structures under In-Plane Compressive Fatigue Loading

An Integrated Approach for Prognosis of Remaining Useful Life for Composite Structures under In-Plane Compressive Fatigue Loading

Flocculation potential regulation to achieve the improved thermal‐mechanical performance for CB/GO reinforced NR nanocomposites

AbstractWith the rapid development of modern transportation systems, optimizing the relationship between structure and performance to obtain natural rubber‐based nanocomposites with excellent comprehensive performance is still worth to investigation. Herein, the regulation of flocculation potential through different flocculants selection on the thermomechanical properties for carbon black/graphene oxide reinforced natural rubber (CB/GO/NR) nanocomposites were investigated based on the compression electric double layer theory. The results showed that formic acid owned the highest zeta potential with comparison of sodium chloride (NaCl), calcium chloride (CaCl2), and aluminum chloride (AlCl3). Meanwhile, as the content was 8 wt%, tensile strength, tearing strength and thermal conductivity could achieve to 27.64 MPa, 56.89 N/mm, and 1.05 W m−1 K−1, respectively. While the heat generation after compression fatigue dropped to 10.1°C. These findings reveal that the highest zeta potential of formic acid could promote the improvement of flocculation degree between GO and NR latex and significantly enhanced the thermomechanical properties of CB/GO/NR nanocomposites due to the larger flocculation potential difference. Therefore, this study not only provides important theoretical insights for preparing high‐performance NR‐based nanocomposites, but also highlights the crucial role of high zeta potential flocculants in optimizing the composite performance. More importantly, the findings offer the creative insights for preparation of the excellent comprehensive NR nanocomposites for the practical industry application.Highlights The effect of flocculation degree on the properties of CB/GO/NR composites was studied. Formic acid was benefit to the flocculation and could promote the surface interaction. CB/GO/NR composites possessed the improved thermal and mechanical properties.

An Adaptable Method for Rapid Fatigue Limit Prediction of Composite Materials Based on Acoustic Emission Technology

ABSTRACTEncouraged by the emerging infrared thermography (IT)–based technique for determining fatigue limit of composite materials, this study introduces a novel approach for the quick fatigue limit determination based on acoustic emission (AE) technology. The AE‐based method expands fatigue testing capabilities beyond the IT‐based methods. Fatigue experiments were conducted for the composite laminates and composite sandwich panels subjected to stepwise increasing cyclic loads. For composite laminate specimens subjected to tension–tension and tension–compression fatigue loads, the fatigue limits obtained by the AE‐based method are in good correlation with those acquired from the IT‐based method as well as the conventional up‐and‐down test procedure. In the tests for out‐of‐plane shearing fatigue limits of composite sandwich panel specimens, where the IT‐based method did not work properly, the AE‐based method performed well and obtained the fatigue limit estimation, which is in line with that derived from the S–N curve data, thereby demonstrating its high adaptability.

Effect of granulated blast furnace slag on uniaxial compression fatigue properties of engineered geopolymer composites

Engineered geopolymer composites (EGCs), emerging as a novel eco-friendly cementitious material, exhibit considerable potential in diverse applications. Granulated blast furnace slag (GBFS) is a by-product of the blast furnace ironmaking process. Owing to its exceptional cementing properties, GBFS is frequently incorporated into geopolymer materials to enhance strength and stability, while also achieving slurry solidification at ambient temperature. The study examined the effect of different rates of GBFS replacement on the fatigue behavior of EGCs using uniaxial compression fatigue testing, with a particular focus on the changes in fatigue life and fatigue deformation. The results indicate that the fatigue life of EGC conforms to a Weibull distribution. While a higher GBFS replacement rate can improve the compressive strength of EGC, it has a detrimental effect on the fatigue life. Furthermore, when subjected to fatigue loading, the total strain accumulation, residual strain, and fatigue stiffness of EGC exhibited a three-stage evolutionary pattern, and remained constant during the secondary creep stage. Therefore, the comprehensive effect of adding GBFS to EGC on material strength and fatigue properties should be taken into account. This study uncovers the potential negative impacts of GBFS on the fatigue properties of EGC, contradicting the previous belief that GBFS could enhance the mechanical properties of geopolymers. Therefore, a comprehensive and meticulous assessment is necessary when contemplating the use of GBFS as a reinforcement material for EGC.

Fabrication of highly carboxylated nanofibrous aerogels under mild conditions and their protein adsorption performance

The development of high-performance media for protein adsorption in bio-purification is highly desired, particularly in biological pharmaceuticals. In this study, we demonstrate a simple, versatile and mild strategy to construct a nanofibrous aerogel (NFA)-based adsorption media for protein purification. Pyromellitic dianhydride (PMDA) was selected to in-situ graft onto poly(ethylene-co-vinyl alcohol) (PE-co-PVA) nanofibers in aerogels through liquid phase grafting. The obtained PE-co-PVA/PMDA NFAs (PPNAs) possessed superb underwater elasticity, compression fatigue resistance and shape-memory performance. With an open porous network, abundant adsorption ligands, and surface hydrophilicity, the PPNAs exhibited a significant adsorption capacity of 1019.71 mg/g and a short equilibrium time of 3.0 h, surpassing that of commercial and reported nanofiber-based adsorbents. Additionally, the PPNAs demonstrated good dynamic adsorption performance for protein driven solely by gravity. Furthermore, the PPNAs showed reusability, selectivity, acid and alkaline resistance, and practical potential of extracting lysozyme form egg white solution. The successful scale-up of such aerogel-based adsorbents can open up new way for the development and design of next-generation protein adsorption media for bio-purification applications.

Fatigue life prediction method for bolted joints based on equivalent structural stress under tensile–compressive loading

In this study, load amplitude–life (Fa–N) curves were obtained through tensile–compressive fatigue tests of bolted joints. It was observed that the correlation coefficient squared (R2) value of the Fa–N curve with the same geometric and pre-tightening parameters was high, but the R2 value of the Fa–N curve with all the parameters was low, indicating poor correlation and inability to meet the engineering requirements. Therefore, an equivalent structural stress model for the bolted joint was first developed based on a mechanical model with a strict mathematical definition to normalize these Fa–N curves, which considered the bolted joint loads as the input conditions and integrated the geometric and pre-tightening parameters. Subsequently, a classical beam–shell equivalent finite element model of the bolted joint was constructed. The nodal loads in the bolted connection zone were coupled with the forces and moments of the beam element nodes through finite element simulation, and the equivalent structural stress (σs) of the bolted joint was then obtained based on the equivalent structural stress model. Consequently, the equivalent structural stress–life (Ss–N) curve and probabilistic stress–life (P–Ss–N) curve normalized for different Fa–N curves were obtained by fitting the data of σs and N. Lastly, the accuracy of the fatigue life prediction method based on equivalent structural stress was verified by conducting the vibration fatigue test on the bolted joint structure of the subway antenna bracket.

Dielectric behavior and breakdown strength of glass fiber reinforced epoxy composites under dynamic mechanical fatigue

Glass fiber reinforced polymer (GFRP), used in insulating components like insulation rods, needs to withstand both high voltage and large dynamic mechanical fatigue during operation. In this paper, the effects of tension–compression fatigue loads on the dielectric properties of GFRP under various fatigue cycles and stress levels are investigated. The results show that DC conductivity has a strong negative correlation with stiffness, while breakdown strength is showing a positive correlation. Fatigue-induced internal damage could cause continuous charge accumulation and enhanced interfacial polarization, leading to the increase of dielectric constant by 46.89% and the reduction of breakdown strength by 15.05%, when the fatigue span ratio reaches 80% under 40% stress level. Understanding the evolution of dielectric properties of GFRP under dynamic mechanical fatigue conditions is helpful for ensuring the safe and stable operation of electrical power equipment subjected to both high voltage and fatigue loads.

Experimental study on the compressive fatigue performance of nano-silica modified recycled aggregate concrete

This study focused on the compressive fatigue performance of nano-silica (NS) modified recycled aggregate concrete (RAC). 108 prism specimens with varying replacement ratios (i.e., 0 %, 50 %, and 100 %), NS soaking concentrations (i.e., 0 %, 1 %, 2 %, and 3 %), and stress levels Smax (i.e., 0.75, 0.8, 0.85, and 0.90) were designed for compressive fatigue test. The failure process and failure modes for the specimens were observed, the fatigue life curves of NS modified RAC under different design parameters were measured. Moreover, the relationships between different design parameters and fatigue life, fatigue strength were analyzed. The results revealed that the failure modes for specimens with different design parameters were mainly shear failure, conical failure and mixed failure. Fatigue life exhibited significant changes under different stress levels, decreasing notably with increasing stress levels. As the recycled coarse aggregate (RCA) replacement ratio increased, fatigue life demonstrated a decreasing trend. Based on the two-parameter Weibull distribution function, the fatigue life equation considering the influence of variable parameters under different failure probabilities was proposed. When the failure probability was 0.5, the specimen with a NS soaking concentration of 2 % exhibited the highest fatigue strength at the same replacement ratio.

The Evolution of Surfaces on Medium-Carbon Steel for Fatigue Life Estimations

Early in fatigue life, fatigue cracks are often initiated at persistent slip bands (PSBs), which play the main role in surface evolution when the components are subjected to cyclic loading. Therefore, this paper aims to study the behavior of the surface development of medium-carbon steel, specifically 42CrMo4 (SAE 4140). Tests were conducted using tension–compression fatigue testing with stress amplitudes set at 30%, 40%, and 50% of the ultimate tensile strength (UTS); a load ratio of R = −1; and a frequency of f = 10 Hz. The ultimate number of test cycles was 2 × 105. The fatigue test specimens with as-machined surface quality (Ra < 100 nm) were tested on a servo-hydraulic push–pull testing machine, and the tests were interrupted a few times to bring the specimens out for surface measuring with a confocal microscope. The linear roughness values of the arithmetic mean deviation (Ra), maximum height (Rz), maximum profile peak height (Rp), and maximum profile valley depth (Rv) were investigated and further used to determine the roughness evolution during cyclic loading (REC) by analyzing the inclinations of the fitting curves of roughness and number-of-cycles diagrams. REC could then be used to estimate and classify the fatigue lifetime.

Comparative fatigue performance of as-built vs etched Ti64 in TPMS-gyroid and stochastic structures fabricated via PBF-LB for biomedical applications

PurposeThis study compares the fatigue performance and biocompatibility of as-built and chemically etched Ti-6Al-4V alloys in TPMS-gyroid and stochastic structures fabricated via Powder Bed Fusion Laser Beam (PBF-LB). This study aims to understand how complex lattice structures and post-manufacturing treatment, particularly chemical etching, affect the mechanical properties, surface morphology, fatigue resistance and biocompatibility of these metamaterials for biomedical applications.Design/methodology/approachSelective Laser Melting (SLM) technology was used to fabricate TPMS-gyroid and Voronoi stochastic designs with three different relative densities (0.2, 0.3 and 0.4) in Ti-6Al-4V ELI alloy. The as-built samples underwent a chemical etching process to enhance surface quality. Mechanical characterization included static compression and dynamic fatigue testing, complemented by scanning electron microscopy (SEM) for surface and failure analysis. The biocompatibility of the samples was assessed through in-vitro cell viability assays using the Alamar Blue assay and cell proliferation studies.FindingsChemical etching significantly improves the surface morphology, mechanical properties and fatigue resistance of both TPMS-gyroid and stochastic structures. Gyroid structures demonstrated superior mechanical performance and fatigue resistance compared to stochastic structures, with etching providing more pronounced benefits in these aspects. In-vitro biocompatibility tests showed high cytocompatibility for both as-built and etched samples, with etched samples exhibiting notably improved cell viability. The study also highlights the importance of design and post-processing in optimizing the performance of Ti64 components for biomedical applications.Originality/valueThe comparative analysis between as-built and etched conditions, alongside considering different lattice designs, provides valuable information for developing advanced biomedical implants. The demonstration of enhanced fatigue resistance and biocompatibility through etching adds significant value to the field of additive manufacturing, suggesting new avenues for designing and post-processing implantable devices.

Evaluation of finite element modeling methods for predicting compression screw failure in a custom pelvic implant.

Introduction: Three-dimensional (3D)-printed custom pelvic implants have become a clinically viable option for patients undergoing pelvic cancer surgery with resection of the hip joint. However, increased clinical utilization has also necessitated improved implant durability, especially with regard to the compression screws used to secure the implant to remaining pelvic bone. This study evaluated six different finite element (FE) screw modeling methods for predicting compression screw pullout and fatigue failure in a custom pelvic implant secured to bone using nine compression screws. Methods: Three modeling methods (tied constraints (TIE), bolt load with constant force (BL-CF), and bolt load with constant length (BL-CL)) generated screw axial forces using functionality built into Abaqus FE software; while the remaining three modeling methods (isotropic pseudo-thermal field (ISO), orthotropic pseudo-thermal field (ORT), and equal-and-opposite force field (FOR)) generated screw axial forces using iterative physics-based relationships that can be implemented in any FE software. The ability of all six modeling methods to match specified screw pretension forces and predict screw pullout and fatigue failure was evaluated using an FE model of a custom pelvic implant with total hip replacement. The applied hip contact forces in the FE model were estimated at two locations in a gait cycle. For each of the nine screws in the custom implant FE model, likelihood of screw pullout failure was predicted using maximum screw axial force, while likelihood of screw fatigue failure was predicted using maximum von Mises stress. Results: The three iterative physics-based modeling methods and the non-iterative Abaqus BL-CL method produced nearly identical predictions for likelihood of screw pullout and fatigue failure, while the other two built-in Abaqus modeling methods yielded vastly different predictions. However, the Abaqus BL-CL method required the least computation time, largely because an iterative process was not needed to induce specified screw pretension forces. Of the three iterative methods, FOR required the fewest iterations and thus the least computation time. Discussion: These findings suggest that the BL-CL screw modeling method is the best option when Abaqus is used for predicting screw pullout and fatigue failure in custom pelvis prostheses, while the iterative physics-based FOR method is the best option if FE software other than Abaqus is used.

Microstructure and fatigue properties of laser-MIG hybrid welding of medium-thickness 6005A aluminum alloy

Light alloys represented by aluminum alloys have a wide range of applications in railway transportation, the key load-bearing parts of high-speed train bodies are welded with a large number of medium-thickness plates, so the study of the welding performance of medium-thickness aluminum alloy plates is significant. In this study, laser-MIG hybrid welding technology is used to realize the single-layer, single-pass welding of 6005A aluminum alloy plate with a thickness of 10 mm. The grains in the weld zone (WZ) are coarsened by welding heat, and the average diameter is about 1.6 times that of the base metal (BM), while the average grain diameter in the heat-affected zone (HAZ) is similar to that of the BM. A softening phenomenon is observed in the welded joint, with a minimum hardness of 72.6 HV in the HAZ. TEM analysis shows that the softening phenomenon is caused by the coarsening of precipitate phases in the HAZ. In terms of tensile properties, the ultimate tensile strength (UTS) of the welded joint is approximately 237 MPa, which is 70.1 % of the BM. The fatigue strength (Nf = 2 × 106 cycles) of the welded joints is predicted to be 83 MPa, which is 64 % of the yield strength (YS), from the S-N curve obtained by fitting the tension–compression fatigue test data. Different morphologies of secondary phase particles are observed in the fatigue crack propagation zone, and their formation and effects on secondary crack are described. The fracture location indicates that softening behavior in the HAZ is the main factor influencing tensile performance, while defects in the WZ are the primary factors affecting fatigue fracture. The experimental results can enrich the tensile and compressive fatigue data of 6005A aluminum alloy.

Design and molecular dynamics of biocompatible WPU/PVA composite hydrogels with enhanced fatigue resistance: Energy dissipation of intermolecular clusters for elastomers

To engineer a hydrogel elastomer for use as an in vivo tissue replacement, it is imperative to ensure superior fatigue resistance, guaranteeing a prolonged service life. Investigating the molecular mechanisms of strain energy accumulation and transmission, which occur during the compression of elastomeric materials, is instrumental in elucidating the causes of hydrogel material fatigue. Such insights are of immense value for the development of durable artificial tissue replacements, ensuring their longevity and sustained functionality within the human body. We synthesized hydrogel elastomers through polyvinyl alcohol (PVA) and waterborne polyurethane (WPU) with good biocompatibility, and studied their fatigue behavior through molecular dynamics (MD). The results of this analysis demonstrate that the introduction of energy dissipation structures between mechanically supported molecular frameworks can enhance the relaxation efficiency of polymers. This improvement leads to enhanced resistance of hydrogels to compression fatigue. A total of 1,000,000 cycles of compression tests were conducted to verify that WPU/PVA did not exhibit any significant compression fatigue under high stress of 50 % strain. In contrast, PVA hydrogel exhibited obvious fatigue due to the absence of an energy dissipation structure. These results revealed the source of compression fatigue resistance of hydrogel elasticity and provided powerful guidance for the design and synthesis of artificial tissues.

Compression–compression fatigue damage of wrinkled carbon/glass hybrid composite laminates

Compression–compression fatigue tests were carried out to study the compressive fatigue damage mechanisms of a carbon/glass hybrid composite laminate with a manufacturing-induced wrinkle defect. As reported in literature, thin wrinkled composite laminates could show sensibly different fatigue behaviours and damage mechanisms in the presence of tension and compression cyclic loadings. The sensitivities of composites to tension and compression cyclic loadings were not the same. In this study, the damage modes and cracking sequence of a thick wrinkled laminate were identified by the strain fields from digital image correlation (DIC). Acoustic emission (AE) and infrared (IR) thermography were used to detect the damages and explore the potential capabilities of non-destructive evaluation methods when applied to detection of fatigue induced damages in composite structures under operational cyclic loadings. Two primary damage modes were identified and detected before the final failure of the laminate i.e. debonding between the resin-rich layer and the laminate and interlaminar cracks. Debonding occurred earlier than interlaminar cracking. Out-of-plane stresses due to fibre waviness drove the initiation of these damages. Under the settings of AE in this work, AE captured early debonding activities but did not detect the micro damage accumulating before the formation of interlaminar crack. Interlaminar crack initiation was tracked by IR thermography at cross-section of the specimen based on the distinct temperature localisations that occur with this micro damage. No distinct temperature localisations occurred during the formation of debonding as it is mode-I driving under compression–compression cyclic loading, so IR thermography did not detect the debonding crack. The results of this study show the potential of using complementary non-destructive damage evaluation methods to inspect early damages in composite structures. The early detection of damages would give early warning signs before the damages become critical. It is found that AE and IR thermography should be used as complementary tools to detect different damage modes.

Tension–Compression Fatigue of a Hybrid Polymer-Matrix/Ceramic-Matrix Composite at Elevated Temperature

Tension–Compression Fatigue of a Hybrid Polymer-Matrix/Ceramic-Matrix Composite at Elevated Temperature

Dislocation structures in micron-sized Ni single crystals produced via tension–compression cyclic loading

The strength and deformation characteristics of micron-sized metals under monotonic loading have long been investigated. In contrast, despite its practical significance, their fatigue behavior remains unexplored. To this end, tension–compression fatigue tests were conducted herein on micron-sized Ni single crystals to elucidate their fatigue behavior and internal dislocation structures. Specimens with square cross sections of 5 and 2 μm on a side were prepared and subjected to cyclic loading at low stress amplitudes, which did not induce fatigue cracking in bulk metals. Remarkably, fatigue cracks were not present in 5-μm-wide specimens, whereas intrusions/extrusions were observed in 2-μm-wide specimens, leading to crack initiation. Vein-like structures comprising edge dislocations were observed in 5-μm-wide specimens, which are commonly observed in bulk metals. Conversely, the dislocation structure in 2-μm-wide specimens resembled that associated with persistent slip bands, which cause intrusions/extrusions and fatigue cracking in bulk metals under high stress amplitudes. The experimental findings indicate that the fatigue behavior of small-sized metal single crystals is characterized by the absence of vein formation.

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.

Natural Rubber/Styrene-Butadiene Rubber Blend Composites Potentially Applied in Damping Bearings.

Natural rubber (NR) composites have been widely applied in damping products to reduce harmful vibrations, while rubber with only a single composition barely meets performance requirements. In this study, rubber blend composites including various ratios of NR and styrene butadiene rubber (SBR) were prepared via the conventional mechanical blending method. The effects of the rubber components on the compression set, compression fatigue temperature rising and the thermal oxidative aging properties of the NR/SBR blend composites were investigated. Meanwhile, the dynamic mechanical thermal analyzer and rubber processing analyzer were used to characterize the dynamic viscoelasticity of the NR/SBR blend composites. It was shown that, with the increase in the SBR ratio, the vulcanization rate of the composites increased significantly, while the compression fatigue temperature rising of the composites decreased gradually from 47 °C (0% SBR ratio) to 31 °C (50% SBR ratio). The compression set of the composites remained at ~33% when the SBR ratio was no more than 20%, and increased gradually when the SBR ratio was more than 20%.