In this study, the bond fatigue performance of ultra-high-performance concrete (UHPC) and normal-strength concrete (NSC) repair material is investigated based on the roughness factor. A single-side ...shear test is performed to evaluate the bond fatigue performance under stress levels of 0.7, 0.8, and 0.9. The results indicate that the NSC-NSC specimen exhibits a bond failure mode, whereas the UHPC-NSC specimen exhibits substrate failure or substrate and bond mixing failure. Roughness is a key factor affecting bond fatigue life. Fatigue life prediction equations for UHPC-NSC and NSC-NSC are developed. The overlay transition zone of UHPC-NSC is denser than that of NSC-NSC.
•The single side shear test was used to evaluate bond fatigue performance.•Ultra-high-performance concrete repair materials could increase bond fatigue life by more than 121%.•Fatigue life prediction equations for UHPC-NSC and NSC-NSC were developed.
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•DED-Arc manufacturing technique was successfully on large-scale structure.•Pressure test up to 111 bar was performer to DED-Arc structure.•Coupons extracted from the structure were ...subjected to quasi-static and fatigue testing.•Fatigue strength assessment considering local quality was introduced.
Wire-arc direct energy deposition was used in this study to manufacture a standing pressure vessel made of stainless steel. Considering the thickness of the additively manufactured sections, the fabricated part was divided into two major components: the shell and the head. The shell with a nominal wall thickness of 5 mm was manufactured using a single-pass technique, while the relatively thicker head, with a maximum thickness of 30 mm, was fabricated using a multi pass approach. The transition from the shell to the 15–30 mm thick head was done by variating wall thickness, enabled by additive manufacturing. After additive manufacturing, the full-scale component was tested up to the maximum internal water pressure of 111 bar (defined per the vessel’s industrial application). Further, to evaluate the mechanical properties of the additively manufactured steel and the effects of pressure loads on it, quasi-static tensile and fatigue tests were conducted on coupons prepared from the material in two conditions: as-built (without any preload) and preloaded (after the pressure test) extracted from various sections. Finally, metallurgical characterization was performed to establish a correlation between the microstructural features and the mechanical performance. The results showed that it is possible to manufacture high-performance and quality pressure vessels using the wire-arc direct energy deposition method.
The GFRP (Glass Fiber Reinforced Polymer) is prospective in bridge and building engineering for its advantageous material property. The connection configuration of hybrid bonded/bolted joint of GFRP ...is thought superior in mechanical performance compared with the traditional bonded and bolted joints. However, the fatigue issue of this type of joint remains unclear which impedes its engineering applications. The presented work experimentally and numerically investigated the fatigue behavior of the GFRP hybrid bonded/bolted single-lap joints under shear loading. High-cycle fatigue tests on single-bolt, four-bolt, and nine-bolt specimens were conducted to study the failure process, rigidity degradation, failure mode, and fatigue life of the hybrid joints, where the nondestructive monitoring techniques of AE (Acoustic Emission) and 3D-DIC (Three-Dimensional Digital Image Correlation) were adopted, respectively to detect the material damages and overall deformation of specimens. Finite element modelling was further carried out to reveal the fatigue failure mechanism of hybrid joints, in which the property degradation of GFRP plates and adhesive layer were considered. Results showed that the failure process of GFRP hybrid single-lap joints under fatigue shear loading can be divided into four stages: (1) steady and (2) rapid development of adhesive damage, (3) steady and (4) rapid development of GFRP damage, of which the (2) and (4) stages account for less than 3% of the total fatigue life of joint, respectively. Stiffness degradation of 14–35% were read for the tested joints before final failure, and the joints with more bolts performed a superior degradation resistance compared to the less ones. Besides debonding and bolt inclination, the single-bolt joints failed with bearing failure of GFRP material, while the failure mode of multi-bolt joints were dominated by shear failure in GFRP plate with Y-shaped zone. The simulation results well supported the observations in experimental test. Based on the experimental results, the S-N curve of the GFRP hybrid single-lap joints is proposed, which can provide support for the engineering design of this type of joints.
•High-cycle fatigue test of GFRP hybrid bonded/bolted single-lap joints under shear loading is conducted.•Finite element analysis considering fatigue degradation and failure of GFRP and adhesive is carried out.•Progressive failure stages, failure modes, and rigidity degradation of GFRP hybrid joints are revealed.•S-N curve for design of GFRP hybrid bonded/bolted single-lap joints under shear fatigue loading is proposed.
In this study, the effects of Ultrasonic Nano-crystal Surface Modification (UNSM) on residual stresses, microstructure changes and mechanical properties of austenitic stainless steel 304 were ...investigated. The dynamic impacts induced by UNSM leads to surface nanocrystallization, martensite formation, and the generation of high magnitude of surface compressive residual stresses (−1400MPa) and hardening. Highly dense deformation twins were generated in material subsurface to a depth of 100µm. These deformation twins significantly improve material work-hardening capacity by acting both as dislocation blockers and dislocation emission sources. Furthermore, the gradually changing martensite volume fraction ensures strong interfacial strength between the ductile interior and the two nanocrystalline surface layers and thus prevents early necking. The microstructure with two strong surface layers and a compliant interior embedded with dense nanoscale deformation twins and dislocations leads to both high strength and high ductility. The work-hardened surface layers (3.5 times the original hardness) and high magnitude of compressive residual stresses lead to significant improvement in fatigue performance; the fatigue endurance limit was increased by 100MPa. The results have demonstrated that UNSM is a powerful surface engineering technique that can improve component mechanical properties and performance.
•Full-scale physical model of CRTS III slab ballastless track structure under heavy haul train load.•Force analysis of CRTS III slab ballastless track self-compacting concrete layer structure under ...fatigue load.•Explanation of fatigue characteristics and damage law of self-compacting concrete layer of CRTS III slab ballastless track.•Research on fatigue life prediction of self-compacting concrete layer of CRTS III slab ballastless track structure under different axle loads.
To further explore the fatigue characteristics of the CRTS (China Railway Track System) type III slab ballastless track structure generally used for high-speed railways, the fatigue damage of CRTS III type slab ballastless track structure system under the action of heavy-haul trains was studied. Based on the three-stage model, the CRTS III slab ballastless track structural system fatigue finite element numerical model was established, with particular emphasis on the fatigue characteristics of the self-compacting concrete of the CRTS III slab ballastless track under a load of heavy haul trains. To verify the reliability of the established model, the track structure displacement and stress under static load and fatigue load were analyzed and compared. The results shows that the model can be used to explore the fatigue damage law of the structural system of the CRTS III slab ballastless track under the action of heavy-haul trains. The results of further analysis showed that: (1) For self-compacting concrete, the maximum longitudinal tensile stress is greater than the maximum lateral tensile stress (2) For the longitudinal direction of the lower surface of the self-compacting concrete, once the tensile stress reaches the tensile strength of concrete, the self-compacting concrete cracks; as the number of fatigue loads further increases, more cracks will develop from the sides of the slab centre in the self-compacting concrete (3) The larger the axle load, the higher the stress level of each layer of the track structure, the faster the concrete damage rate, and the earlier the concrete cracks. As axle load is greater than 35 t, the damage of self-compacting concrete is more pronounced.
•Better surface quality and residual compressive stress are obtained by ultrasonic vibration.•Residual compressive stress suppresses initiation of C/SiC interface fatigue cracks.•Fiber machining ...damage aggravates fiber crack to weakening anti-fatigue performance.•Residual strength is enhanced close to tensile strength by rotary ultrasonic milling.
Rotary ultrasonic milling technology (RUM), as a surface strengthening machining method, was proposed to utilize in processing of C/SiC composites for enhancing anti-fatigue performance innovatively. Static tensile, intermittent fatigue and residual strength test were carried out. Due to constant impingement of high-frequency and low-amplitude vibration, surface residual compressive stress was formed near 2 GPa maximally. Axial thermal residual stress in fiber achieved -662.4 MPa proved by loading-unloading test. The peak value of fatigue damage parameter was reduced significantly. RUM surface restrains most of interface cracks because of residual compressive stress, and hinder the growth of fiber cracks for better machined surface quality. The damage accumulation, the first stress redistribution and fiber reinforcement stage were delayed. Average damage rate was decreased by 80.5 %. Residual tensile strength of RUM C/SiC was improved after fatigue, up to 95.8 % of tensile strength. The strengthening effect from RUM on fatigue property of C/SiC is significant and valuable.
•Systematic review of the literature regarding the incorporation of plastic waste into asphalt mixtures.•Analysis of the impact of incorporating plastic waste on rutting and fatigue ...performances.•Plastic waste incorporation extends pavement life and helps to mitigate plastic pollution.
The disposal of plastic waste has become a great challenge for the current generation due to the large-scale production and non-degradable properties of plastics. Additionally, fatigue and rutting are the most common problems that bituminous pavements face. Thus, the incorporation of plastic waste into road pavements has been studied as a possible solution to help mitigate the problems related to plastic disposal and possibly improve the performance of road pavements. This paper presents a systematic review of the literature regarding the incorporation of plastic waste into asphalt mixtures and its impact on rutting and fatigue performance. The main objective is to evaluate the effect of adding plastic on rutting and fatigue performance by analyzing the results of the most commonly performed laboratory tests reported in a dataset, systematically selected following the PRISMA 2020 methodology for systematic reviews. Although deeper research considering short- and long-term ageing is still necessary, the incorporation of plastic waste generally improves the rutting resistance of asphalt mixtures. However, the effect on fatigue behaviour is not clear yet. Finally, it can be said that plastic waste has the potential to be incorporated into asphalt mixtures and help mitigate the environmental problem related to its disposal.
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•The mechanism of cold treatment affects the fatigue life of carburized steel.•Cold treatment before tempering is not beneficial to the fatigue property.•Cold treatment after ...tempering improves the fatigue property.•The cold treatment sequence will cause different fatigue failure modes.•The location of crack source varies greatly due to the cold treatment process.
In this paper, the role of cold treatment (before tempering and after tempering) on the fatigue properties of 18CrNiMo7-6 carburized steel are systematically investigated, and the fatigue crack initiation mechanism of 18CrNiMo7-6 carburized steel is clarified through the observation of fatigue fracture surfaces. In addition, the changes of hardness, microstructure and residual stress during fatigue test were observed in situ. The results revealed that after cold treatment (after tempering), the fatigue limit increased from 830 MPa to 870 MPa. The fracture of cold treatment group after tempering was caused by inclusions. On the contrary, the cold treatment before tempering is not beneficial to the fatigue property. Furthermore, the cracking induced by high density twinned martensite was observed in the cold treatment group before tempering. Finally, the retained austenite content of the surface layer after the cold treatment (before tempering) decreased significantly. However, under the action of cyclic load, the high hardness and residual compressive stress of the surface layer continue to decrease due to the cyclic softening and stress relaxation effects, respectively. The poor persistence of hardness and residual compressive stress is not conducive to the fatigue properties.
•Submerged micro-abrasive waterjet peening is proposed to improve the metal surface integrity and fatigue performance.•The surface integrity state of TA19 titanium alloy after the SMA-WJP is ...systematically analyzed.•The high-cycle fatigue life of TA19 titanium alloy treated by SMA-WJP is increased by a maximum of 2.72 times.•The improved fatigue life is attributed to the plastic deformation layer and large CRS induced by SMA-WJP.
Waterjet peening has become a critical surface treatment technology due to its great potential for improving the surface integrity and fatigue performance of metallic materials. The present study aims to investigate the influence of submerged micro-abrasive waterjet peening (SMA-WJP) on the surface integrity and fatigue properties of TA19 titanium alloy. First, the SMA-WJP with different water pressure (P = 70, 100, and 130 MPa) was conducted on the TA19 specimen. The surface integrity of the specimen before and after SMA-WJP treatment was studied, including the microstructure, surface roughness, microscopic morphology, microhardness, and residual stress. Results showed that the SMA-WJP treated specimen with different water pressure formed a plastic deformation layer with a depth of 24–44 μm, the minimum surface roughness of Ra = 0.363 μm and Sa = 0.95 μm. The depth of the work-hardened layer and compressive residual stress (CRS) layer was approximately 100–150 μm and 160–290 μm. The microstructure evolution on the top surface and sub-surface of the as-received and SMA-WJP treated specimens were characterized by transmission electron microscopy (TEM), which showed that nanocrystals with an average size of 12 nm and high density of dislocations formed on the top surface of the SMA-WJP treated specimen. Finally, stress-controlled high-cycle fatigue (HCF) tests were carried out to study the fatigue behavior of the TA19 titanium alloy before and after SMA-WJP treatment. The HCF life of the specimen is increased by a maximum of 2.72 times. The fatigue fracture surface was examined with scanning electron microscopy (SEM), which revealed that the existence of the plastic deformation layer and large CRS induced by SMA-WJP could effectively inhibit the initiation and propagation of cracks. This work enriches the waterjet peening process by investigating submerged abrasive waterjet peening and brings a new solution for improving the surface integrity and fatigue performance of TA19 titanium alloy.
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