Peeling Failure Research Articles

Study on Flexural Performance of Reinforced Concrete Beams Strengthened with FRP Grid–PCM Composite Reinforcement

To study the flexural performance of fiber-reinforced polymer (FRP) grid–polymer cement mortar (PCM)-composite-strengthened RC beams, the finite element numerical simulation of FRP grid–PCM composite RC beams is carried out using ABAQUS to analyze the effects of the amount of FRP grid reinforcement, the type of FRP grid material, and the geometry of FRP grid on the flexural performance of reinforced concrete beams and to establish the flexural capacity calculation formula of FRP grid–PCM-reinforced RC beams in case of debonding failure, based on analysis of the influencing factors. The results show that increasing the reinforcement of the FRP grid and increasing the stiffness of the FRP grid can improve the flexural bearing capacity of RC beams, and the change of FRP grid geometry has little effect on the flexural bearing capacity of RC beams. The established formula for calculating the flexural bearing capacity of FRP grid-reinforced concrete beams can better predict the flexural capacity of reinforced concrete beams under peeling failure.

Lifespan Evaluation for a Standard RV Reducer based on Fatigue Strength Theory

Rotate vector (RV) reducers are the two-stage deceleration device comprising involute and cycloid-pin gear transmission mechanisms. As the typical deceleration elements, they are widely applied in industrial robots, digitally controlled machine tools and automation fields due to their compact structure and high precision. However, a reducer may lose precision after a long-term operation. Moreover, pitting and metal peeling of internal components may also occur, leading to a fatigue failure. Therefore, it is necessary to conduct investigations on lifespan evaluation for RV reducers. In this study, the CRV-80E reducer is taken as the research object. Firstly, according to its transmission characteristics, the lifespan evaluation model for a standard RV reducer is established based on fatigue strength theory and Palmgren-Miner linear cumulative damage law, with the internal crankshaft bearing is considered as the key component. Then, the simulations are carried out on crankshaft bearing by the ANSYS Workbench and SKF SimPro. The contact stress, deformation on bearing rollers, and the rated lifespan of the reducer are simulated. Finally, the accelerated life test is conducted on an RV reducer by increasing the external load with the positioning precision as an output and criterion. After the test, the reducer is disassembled, and metal peeling failure is observed on the crankshaft bearing while other parts are relatively intact. The test results validate the feasibility and accuracy of the service life evaluation model and simulation analysis. This study provides a new research approach for researchers and manufacturers and a design reference for engineers to improve the lifespan of RV reducers by optimizing crankshaft bearings, which have a certain academic value.

Characterization of damage behavior and failure mechanisms of the bonded‐bolted hybrid three‐bolt joint in composite laminates

AbstractIn this paper, the mechanical properties, damage modes, and bolt load distribution of the bonded‐bolted hybrid three‐bolt joint were investigated by a combination of experiments and numerical simulations. Acoustic emission (AE) was used to monitor the tensile process of the connection in real time, and the K‐means clustering algorithm was used to realize the cluster analysis of the damage modes. A numerical simulation model of the tensile process of the joint was established using ABAQUS simulation software. The progressive damage evolution of composite laminates, and adhesive layer was characterized by using the VUMAT subroutine, the B‐K failure criterion, and cohesive element with zero thickness, respectively. The results show that four main damage modes occur in composite laminates during tension: matrix cracking, delamination, fiber pull‐out, and fiber breakage, with corresponding peak frequency ranges of (0–80 kHz), (80–210 kHz), (210–330 kHz), and (330–375 kHz), respectively. The adhesive layer between the laminates mainly exhibits peeling failure because of the secondary bending effect. In the load‐bearing process, the adhesive layer was loaded first and failed, and the bolt loading was delayed. Meanwhile, the results of bolt load distribution showed that the bolts and the adhesive layer at both ends carried greater loads.Highlights Damage modes and damage evolution of the bonded‐bolted hybrid joint in tension were analyzed by combining acoustic emission technology and numerical simulation. The simulation of delamination damage in composite laminates was carried out by inserting zero‐thickness cohesive elements into the laminates, and the delamination damage between the carbon fiber layup and the adjacent glass fiber layup was analyzed. The effect of the inclusion of the adhesive layer on the mechanical properties of the joint and the distribution of the bolt load was analyzed.

Compressive performance of underwater concrete piers reinforced with prefabricated FRP shells

A novel underwater spliceable basalt fiber-reinforced polymer (BFRP) shell-confined concrete structure was proposed that rapidly reinforces underwater piers by lapping the FRP shell with adhesive underwater combined with nondispersive mortar (NDM) filling. Thirty-six prefabricated BFRP shells combined with nondispersive mortar reinforced concrete columns (PFRCs) were made for axial compression testing. The effects of the BFRP layer number, lap length and pouring environment on the specimen performance were compared, and different damage patterns and stressstrain relationship curves were obtained. The test results reveal that the PFRCs exhibited two failure modes: BFRP fracture failure in nonlapped segments and BFRP bond adhesive peeling failure in lap segments, and the specimens with more BFRP layers and shorter lap lengths were prone to BFRP bond adhesive peeling failure. From 2 to 4 layers, the ultimate stress and ultimate strain values increased by 1.18–1.91 times and 5.18–10.32 times, respectively, demonstrating increasing the number of BFRP layers is a more effective means to improve the structural performance. The ultimate strength of the underwater reinforced specimens reached more than 70 % of that of the corresponding specimens on land, which demonstrated the feasibility of using prefabricated FRP-molded shell reinforcing technology for submerged piers. Finally, the calculation model of an FRP-confined concrete column is evaluated, and the full stressstrain curves of the PFRCs are proposed.

Determination traction-separation parameters and its sensitivity analysis of bilinear cohesive zone model through experimental and numerical peeling analysis of electrodes

The optimization of traction-separation parameters within the cohesive zone model (CZM) is crucial for accurately simulating electrode peeling failure in lithium-ion batteries. This study performed 180° peeling tests on NCM electrodes and used Abaqus software alongside the sim-flow optimization tool for simulation analysis, aiming to accurately replicate the failure behavior at the lithium-ion battery electrode interface. Experimental results were used to determine the fracture energy of the electrode interface, while numerical simulations analyzed the peeling performance of the electrode. By fitting the force-displacement curves from both simulation and experiment, the traction-separation parameters within the bilinear CZM were optimized. Additionally, the study analyzed the effects of traction-separation parameters, as well as the modulus and thickness of the current collector, on peeling behavior. The results showed that a significant increase in the interface stiffness and strength increased the steady-state peeling force. Among these, the fracture energy had the most significant influence on the steady-state peeling force. Furthermore, while the modulus and thickness of the current collector affected the maximum peeling force, their effect on the steady-state peeling force was negligible. These findings enhance the accuracy of simulating the failure behavior of the electrode interface.

Cross-sectional shape effect of stay-in-place formwork column on axial compressive behaviour

Experimental and numerical studies on the behavior of composite columns with prefabricated self-compacting mortar (SCM) stay-in-place (SIP) formwork and post-cast normal-strength core concrete were presented.The axial compression of twenty-eight reinforcement concrete (RC) composite columns having square or circular cross-section shapes, with formwork thicknesses of 10 mm or 15 mm, and confined with one or two layers of Carbon Fibre Reinforced Polymer (CFRP (, were tested. A finite element (FE) model was generated to simulate the stress–strain relationship, and failure mode of the column using ABAQUS software. The results show that square cross-section-shaped columns exhibited lower axial load and displacement capacities than their counterparts of equivalent circular cross-section-shaped columns. This behavior maintained consistent regardless of the use of the SCM-SIP formworks or the wrapping with CFRP fabrics. Among the various confinement systems compared in this study, the efficiency of the CFRP was the greatest. Good bonding with no peeling failure was observed between SCM-SIP formwork and core concrete, indicating the good integrity of the composite columns. Consistency between the FE model and experimental results was observed for both cross-section shapes, indicating the precise and plausible characteristics of the model to sensibly estimate the stress-strain behaviors.

Investigation on failure mechanism and time-delay fracturing behavior of hard-rock tunnel under extremely high geostress state

To investigate the failure mechanism and time-delay fracturing behavior of hard-rock tunnel under extremely high geostress state, a series of conventional triaxial compression tests and time-delay loading–unloading mechanical tests on rocks were conducted. Combining testing results and on-site data of deep-buried tunnels, the generation mechanism and failure process of time-delay rockbursts were analyzed. The results indicate that with the increase of confining pressure, the failure mode of hard-rock exhibits a transition from axial splitting type and shear-slip type to special squeezing-expansion type. The progressive damage of rocks under extremely high stress state mainly manifests as aging lateral and volumetric expansion. Under time-delay compression tests, the long-term strength of hard-rock is lower than the threshold stress of σeb. In extremely high stress state, the fracture and dissipated energy evolution of rocks has significant time-dependent characteristics. Under extremely high stress conditions, rocks can store a large amount of releasable energy internally and gradually generate numerous cracks without the need for external work, ultimately leading to sudden unstable failure. Affected by the superposition of time-delay pressure and loading–unloading effects, the hard-rock also exhibits the same time-dependent fracturing behavior as soft-rock under high stress state, but its deformation mechanism is dominated by lateral expansion and crack volumetric dilatancy. When the stress level is far from reaching the ultimate strength required for rockmass failure, it is sufficient to cause the propagation of internal microcracks. Under the action of time-delay loads, the spalling and peeling failure of surrounding rock is significantly reduced, but the scale of unstable blocks is larger. Based on the failure process and microseismic monitoring date of rockburst in hard-rock tunnels, the entire evolution process of time-delay rockbursts can be divided into the following six stages: before excavation, rockmss excavation, aging cracking, squeezing-expansion, instability and spalling, time-delay rockburst. Time-delay rockburst has an obvious acoustic emission calm period before its occurrence, making its incubation process has strong suddenness and randomness.

Assessment of the effect of processing parameters on peel failure of laser-assisted automated fiber placed thermoplastic composites

In this study, thermoplastic composites are fabricated using laser-assisted automated fiber placement, focusing on the influence of compaction force, roller head speed, and temperature. Employing wedge peel testing, digital and electron microscopy, and probabilistic machine learning, the research examines how these parameters affect mechanical performance and failure. Key observations include increased bonding area and peel force with higher processing temperatures, while greater compaction force introduces more variability in bonding and peel strength. Roller head speed shows minimal impact. The study effectively links processing parameters with wedge peel failure, illustrating the complex interactions in composite material behavior.

Study on wear protection performance of HVAF WC–Cr3C2–Ni coatings deposited on crystallizer surface

A crystallizer is the most crucial component of the continuous casting and rolling process, and it is required to operate effectively at high temperatures and loads for an extended period. In this study, WC–Cr3C2–Ni cermet coatings with high strength and wear resistance were deposited on the surface of a copper alloy crystallizer using high-velocity air-fuel spraying. The microstructure of the coating and its protective effect on the substrate at different temperatures were analyzed. The coating on the copper substrate was uniform and dense, with a porosity of 0.34 % and stable phases. Wear test results at room temperature showed that copper substrate underwent oxidative peeling failure when subjected to wear, and exhibited severe abrasive and adhesive wear, while WC–Cr3C2–Ni coating had no peeling damage on the surface when subjected to wear. In addition, the friction coefficient of the substrate was reduced from 0.624 to 0.489, thus significantly improving the wear resistance of the crystallizer surface. At high temperature (300 °C), the friction coefficient of coating increased to 0.676. Although the degree of oxidation and fatigue wear of the coating increased, the surface of the coating remained intact without any failure area. WC–Cr3C2–Ni coating protected the crystallizer continuously under high-temperature loading conditions for a prolonged time, indicating enhanced service life of the crystallizer. This study provides significant findings for developing new crystallizer coatings.

Study on Crack Resistance and Calculation Model of RAC Beams Strengthened with Prestressed CFRP

With the development of recycled aggregate concrete (RAC), the recovery rate of construction waste is improved, and the pollution problem is alleviated. In particular, RAC beams strengthened with prestressed carbon fiber reinforced plastics (CFRP) can exhibit improved mechanical properties, expanding RAC application. Four groups of reinforced RAC beam specimens contained 0%, 40%, 70%, and 100% recycled coarse aggregate, respectively. Each group of beams was first pre-cracked and then strengthened by prestressed CFRP with one layer and two layers respectively. Finally, the bearing capacity tests were performed for these beams. The test results show that as the recycled coarse aggregate content increases, the cracking moment and ultimate load capacity of the beam decrease, while its crack width increases. As the CFRP layer increases, the deformation and crack width of the beam decreases, while the number of cracks increases. The prestressed CFRP also exhibited tensile and peeling failure. A beam deflection calculation model was established by introducing a coefficient k representing the interaction between recycled aggregate and CFRP. The influence coefficient of concrete elongation on the crack width and average crack spacing of the beam was modified, and the crack width analysis model of the beam was established. The calculated results are in good agreement with the experimental observations. It can provide reference for the application and design of recycled concrete beams strengthened with prestressed CFRP.

Research on the oxidation sequence of Ni-Al-Pt alloy by combining experiments and thermodynamic calculations

<p>In this paper, a comprehensive study on 1373 K high-temperature oxidation behaviors in a Ni-20 at.% Al-5 at.% Pt system was performed by coupling experimental investigations with CALPHAD (CALculation of PHAse Diagram) calculations. The discussion was expanded to include the effects of chemical concentrations on the degradation mechanism of thermally grown oxide layers during oxidation at 1373 K. A step-by-step oxidation procedure was established: first, aluminum oxide grows on the underside, followed by nickel oxide, which fully develops and penetrates the original aluminum oxide. The formation of NiO leads to aluminum enrichment and nickel depletion; once the concentration of Al achieves a threshold, θ-Al<sub>2</sub>O<sub>3</sub> transforms into α-Al<sub>2</sub>O<sub>3</sub>, forming a tight structure. At this point, Al diffusion toward the exterior predominates, followed by the inward diffusion of O. The diffusion of Ni is gradually restricted by the establishment of the α-Al<sub>2</sub>O<sub>3</sub> layer. When Al is not enough, Al<sub>2</sub>O<sub>3</sub> combines with NiO to develop NiAl<sub>2</sub>O<sub>4</sub>. Nickel segregation may also occur during subsequent oxidation at the oxide layer/matrix alloy boundary. Small voids are likely to form due to the merging of the vacancies caused by the unbalanced diffusion of Al toward the Al<sub>2</sub>O<sub>3</sub> layer and the opposite diffusion of Ni, resulting in significant peeling failure. Additionally, Pt has a beneficial effect by forming a thinner oxide scale that is more resistant to spallation.</p>

Plate end debonding strength model for RC beams strengthened with FRP/SMA composites

Plate end debonding is a common failure mode for fiber reinforced polymer (FRP) strengthened beams. FRP sheets and shape memory alloy (SMA) composites can effectively slow down plate end debonding and improve beam ductility owing to the anchorage effect of SMA wires on the FRP ends. This work aims to comprehensively study the anchorage performance of FRP/SMA composite strengthened beams through both model analysis and experimental investigation. The plate end debonding strength models of existing FRP strengthened beams were initially summarized and analyzed, and an improved model was proposed to predict the debonding strength of FRP/SMA composite strengthened beams at the plate end. Moreover, the anchorage performance and flexural behavior of beams strengthened with carbon fiber reinforced polymer (CFRP) and SMA composites were studied through experiments. The failure mode of the FRP sheet strengthened beams was plate end debonding failure, while the plate end debonding failure of the CFRP/SMA composite strengthened beams occurred at the strengthening zone end, and the peeling failure was delayed owing to the anchorage effect of SMA wires on the ends of the strengthening CFRP sheets. The recovery effect of SMA wires could successfully introduce prestress into CFRP sheets. Moreover, the CFRP strain corresponding to plate end debonding increased because of the anchorage of SMA wires on the CFRP sheet in the strengthening zone. The strength and ductility of the CFRP/SMA composite strengthened beam significantly improved. The proposed model for predicting the plate end debonding strength of FRP/SMA composite strengthened beams was validated through experiments.

An insight into the mechanical behavior and failure mechanism of CFRP/Al adhesively bonded structures subjected to low-velocity impact

Experimental and numerical methods are used to investigate the effects of different impact surfaces and energies on the mechanical properties and failure behavior of CFRP/Al adhesively bonded structures. To predict the damage initiation and propagation of CFRP laminates, interlaminar and adhesive layer, and aluminum alloy plates, the integrated finite element model containing both low-velocity impact (LVI) and axial tensile after impact (TAI) processes is developed by combining continuum damage mechanics model, cohesive zone model, and Johnson-Cook model. Additionally, LVI and TAI tests have been performed on the corresponding adhesively bonded structures with aluminum alloy 5182 (AA5182) and CFRP laminate as impact surfaces, which verify the effectiveness of the proposed integrated FEM. The results indicate that AA5182, as the impact surface, produces greater impact damage (maximum crater depth and opening width) in the center of the overlap region in comparison with the CFRP. The residual bearing capacity of the joints is the result of the competition between impact behavior and mechanical interlocking. The tensile strength, stiffness, and failure displacement of the joints decrease with the increase of impact energy. The failure modes of the joints include annular and circular cohesive failure of the adhesive layer in the impact region, interface failure, cohesive failure and peeling failure in the non-impact region, delamination damage, and fiber pullout and matrix cracking of the CFRP laminate. This investigation can provide good technical support for the structural design of heterogeneous material connections.

The failure law of the cement plug-casing interface for direct plugging in the casing of old wells for salt cavern gas storage

The old salt hole wells cannot be directly converted into gas storage, injection and production wells, so the old wells must be plugged to ensure the effectiveness of plugging. Aiming at the plugging problem of old wells in salt cavern gas storage, a finite element model of the formation-cement sheath-casing-cement plug assembly suitable for direct plugging in the casing of salt cavern gas storage is established to simulate the fracture stripping process of the cement plug-casing interface. The results show that under the pressure of the gas storage, the cement plug casing bonding interface will undergo shear deformation, and after stacking to a certain extent, peeling phenomenon will occur. As the simulation time increases, the peel failure length gradually increases and tends to stabilize, reaching the limit of peel failure length. In the process of research, the factors and laws affecting the peeling failure length are also analyzed. It is found that the peeling failure length of the cement-casing interface is related to the maximum operating pressure of the gas storage, the length of the cement plug, the diameter of the cement plug, the elastic modulus, Poisson’s ratio. The research results are helpful to judge whether the plugging length in the casing is sufficient, and provide theoretical guidance to ensure the long-term safe operation of the gas storage.

Seismic Retrofit of Diagonal Tension Members in Steel Deck-Truss Bridges Using CFRP Sheets

This study entailed axial cyclic loading tests conducted on full-scale diagonal tension members of steel deck-truss bridges to evaluate the effects of seismic retrofitting methods using carbon fiber–reinforced polymer (CFRP) sheets. The loading tests were performed on CFRP-retrofitted specimens with varying anchoring lengths of the CFRP sheets. The results indicated that the proposed retrofitting methods, which employed the intermediate-modulus CFRP type (390–450 GPa) and polyurea putty (a ductile adhesive), delayed the plastic buckling of the flanges and substantially increased the load-carrying capacities, stiffnesses, and ductility capacities of the retrofitted diagonal tension members. Additionally, the polyurea putty effectively suppressed the peeling failure of the CFRP sheets. It maintained the cross-sectional integrity between the steel members and CFRP sheets even after the plastic buckling of the flanges and rupture failure of the CFRP sheets. Further, finite-element analyses accurately reproduced the loading test results by considering the nonlinear bond-slip performance of polyurea putty, anisotropic characteristics of the CFRP sheets, and cyclic plasticity properties of steel.

Mechanical properties analysis of carbon fiber composite bond-rivet hybrid joints of maglev train body in different service environments

Carbon fiber reinforced composites have the advantages of high specific strength and stiffness, which are widely used in rail vehicles. As one of the most commonly used connection forms for maglev train bodies, it is important to ensure the strength and reliability of the joint under different temperatures. Therefore, the paper takes the perspective of carbon fiber composites in the lightweight application of high-speed train bodies. The optimal geometric parameters (end-diameter ratio e/D, width-diameter ratio w/D) of the bond-rivet hybrid joint connection are investigated. The influence laws on structural strength and load-bearing failure forms are found under typical temperatures such as room temperature environment, high-temperature environment, and alternating high and low-temperature environment. Failure specimens and tensile load-displacement curves were analyzed. At the three-room temperatures, the joint structure with an end-diameter ratio e/D of about 3:1 and a width-diameter ratio w/D of about 6:1 had the highest strength, and the failure form was the ideal extrusion damage around the nail hole. The high-temperature environment has little effect on the overall load-bearing capacity of the connected structure in a short period, but it changes the morphology of the adhesive layer. The structure is more prone to shear and peel failure of the adhesive layer. The strength of the alternating high and low-temperature treated joints is slightly higher than that of the untreated specimens when tensile at room temperature. The epoxy resin and carbon fibers are more closely fitted by the environment, enhancing the ability of the composite laminate to withstand tensile and torsional loads.

P‐12.3: Analysis and Application of COF Peeling Failure in Display

In order to solve the problem of COF peeling on OLB (Outer Lead Bonding) side of high curvature display screen, this paper studied the peeling failure strength of COF Bonding so as to guide product design through the combination of experiment and simulation. Firstly, basic peeling test of the COF was carried out under the condition of 60 ℃/90%RH HTHHO, and the COF peeling load was obtained; Then, the linear stress of COF under the peeling load was 0.18 N/mm by finite element numerical simulation; Finally, the COF twist model of 32‐inch R1000 module was established, and the maximum COF twist value was 3mm under the maximum linear stress of 0.18 N/mm at COF Bonding; The module has passed the 60 ℃/90%RH HTHHO 500h test, which verified the accuracy of COF peeling failure judgment method. Considering the safety factor of 2, the linear stress intensity standard of this Bonding process was determined to be about 0.09 N/mm. Based on the above‐mentioned linear stress intensity standard, the 27‐inch curved surface module was optimized from double PCB to single PCB, which passed the verification of high temperature and high humidity condition and met the product quality requirements. The method proposed in this paper can guide module optimization design, reduce the risk of peeling failure at COF Bonding on the source side of curved screen, and improve product reliability.

Experimental and analytical studies on the flexural behavior of steel plate-UHPC composite strengthened RC beams

In view of the excellent mechanical property of Ultra-High Performance Concrete (UHPC), a new method of using steel plate and UHPC (SP-UHPC) composite to strengthen damaged reinforced concrete (RC) beams was proposed. Four-point bending tests were conducted to investigate the failure modes, deformation characteristics, crack resistance, and bearing capacity of five SP-UHPC strengthened beams (SPUB), one reinforced UHPC strengthened beam (RUB), and one reinforced concrete beam (RCB). Additionally, the impacts of different strengthening techniques, the thickness of steel plate and UHPC on the flexural performance of the strengthened beams were investigated and discussed. The effects of the shear strength of UHPC-RC interface on the bearing capacity of the strengthened beams were analyzed. The test results show that the failure mode of strengthened beams is interface peeling failure. Compared with RCB, the cracking moments of SPUBs and RUB increased by about 214.5%-271.5% and 43.7%, respectively. The bearing capacity of SPUBs and RUB increased by 53.1%-73.7% and 53.4%, respectively. The flexural stiffness of strengthened beams increased by nearly one time on average. Compared with RUB, the SPUBs showed a superior crack resistance and interface slip resistance. The increase in the thickness of the steel plate and UHPC can improve the flexural stiffness and the strain behavior of strengthened beams significantly. Based on the test results, the calculation formulae of UHPC cracking moments and bearing capacity of SP-UHPC strengthened beams were proposed considering the effective anchorage length of interface, the strain hardening behavior of UHPC, and the residual strain in RC beam. The calculation results of UHPC cracking moments and bearing capacity coincide with the test results, demonstrating the accuracy of proposed calculation formulae.

Experimental study on the shear behavior of RC beams strengthened with cementitious grout

Strengthening the existing damaged RC beams with a layer of cementitious grout can effectively overcome the limitations of the conventional concrete–replacement method, which has been considered as an effective way to improve the performance of damaged RC beams. This study presented an experimental study on the shear behavior of 24 RC beams strengthened with cementitious grout. The effects of replacement positions, replacement thicknesses, and shear span to effective depth ratios on the shear behavior of the strengthened beams were discussed. Results indicate that (1) No obvious bonding cracks and peeling failures were observed at the interface between the cementitious grout and concrete. (2) Compared with the beams strengthened on the compressive side, the beams strengthened on the tensile side had a smaller load and deflection index value, which indicated that the beams strengthened on the compressive side had a better reinforcement effect than those on the tensile side. (3) With the increase of the replacement thickness, the load and deflection index value of the specimens with different shear span to effective depth ratios increased gradually, and the increment decreased with the increase of the shear span to effective depth ratio. (4) Calculation methods were proposed to evaluate the shear capacity of RC beams strengthened with cementitious grout based on Code GB 50010-2010 and the truss-arch model, respectively, and verified well with experimental data.

A study of the structure and erosion properties of CrNx/CrAlN coatings with different modulation periods

In this study, we deposited CrNx/CrAlN multilayer coatings with different modulation periods on TC4 titanium alloy substrates via cathodic arc deposition. The effects of the different modulation periods on the microstructure, mechanical properties, erosion resistance, and fracture failure mechanism of the coatings were studied. The results show that the multilayer coatings exhibit a dense structure, with the CrNx layer being mainly composed of the CrN (200) and Cr2N (111) phases and the CrAlN layer being mainly composed of the CrN (111) and CrN (200) phases. The comprehensive mechanical properties of the multilayer coating with a modulation period of 200 nm are the best: The hardness is 3306 HV, the bonding force is 50.0 N, the crack propagation resistance is 483, the residual stress is the smallest, and the erosion resistance is the best. In the process of coating fracture failure, the CrAlN hard layer is mainly wear-resistant, while the CrNx metal-rich ductile layer mainly absorbs the fracture stress and undergoes a ductile–brittle transition, which eventually results in brittle fracture and layered peeling failure.