Delamination Mechanism Research Articles

Effect of thermo-reactive diffusion coatings on microstructure and wear behavior of powder metallurgy steel cutting inserts

In this study, powder metallurgy-produced 1.337 steel (PMS 1.3377) was subjected to boronizing, titanizing, and vanadinizing processes at 950 °C for 2 hours. The influence of boride and carbide coatings formed on the surface of PMS 1.3377 on the microstructure of these steels and their wear behaviors at room temperature and 500 °C were investigated. Characterization of the formed coating layers was carried out through Scanning Electron Microscopy (SEM-EDS), X-ray Diffraction (XRD), microhardness, and wear testing. Wear tests considering the cutting tool turning, milling, and drilling applications of PMS 1.3377 were conducted at room temperature and 500 °C in ambient air with a 10 N load and a 250 m sliding distance against an Al2O3 ball. Metallographic studies showed that coating layers with thicknesses of 98±2.1, 11±0.5, 13.5±0.6 µm and hardness of 2566±125 HV0.1, 2037±104 HV0.1, and 1800±197 were obtained by boronizing, titanizing and vanadinizing processes, respectively. The dominant phase structures in the obtained coatings were determined to be FeB, TiC, and VC for boronizing, titanizing, and vanadinizing, respectively. Due to the high hardness of boride and carbide phases and their ability to form more stable oxide layers during wear, the coated samples exhibited lower friction coefficients and lower wear volume losses. While untreated PMS 1.3377 experienced delamination and oxidation wear mechanisms at room temperature, the wear mechanism at 500 °C transformed into adhesive and oxidation wear. On the other hand, in the coated samples, the wear mechanism was found to occur as adhesive, oxidative, and delamination at both room temperature and 500 °C.

Dyke to sill deflection in the shallow heterogeneous crust during glacier retreat: part II

Changes from dyke to sill propagation in the shallow crust are often caused by dissimilar layer properties. However, most previous studies have not considered the influence of glacial loading and unloading on dyke and sill deflection processes. Here, we attempt to collectively explore mechanical (layer stiffness) and geometrical (dyke dip, layer thickness) realistic parameters subject to two different magma overpressure values (namely 5 MPa and 10 MPa) that promote dyke-sill transitions in both non-glacial and glacial settings. To do this, we use as a field example, the Stardalur laccolith: a multiple stacked-sill intrusion located in SW Iceland. The laccolith lies near the retreating Langjökull glacier and was emplaced at the contact between a stiff lava layer and a soft hyaloclastite layer. We initially model two different stratigraphic crustal segments (stratigraphy a and b) and perform sensitivity analyses to investigate the likely contact opening due to the Cook-Gordon debonding and delamination mechanism under different loading conditions: magma overpressure, regional horizontal extension, glacial vertical load and a thin elastic layer at the stratigraphic contact. Our results show that contact opening (delamination) occurs in both non-glacial and glacial settings when the dissimilar mechanical contact is weak (low shear and tensile stress, zero tensile strength). In non-glacial settings, stiff layers (e.g., lavas) concentrate more tensile stress than soft layers (e.g., hyaloclastites/breccia) but accommodate less total (x–y) displacement than the surrounding host rock (e.g., soft hyaloclastites) in the vicinity of a dyke tip. Yet, a thicker hyaloclastite layer in the stratigraphy, subject to higher magma overpressure (Po = 10 MPa), may encourage dyke-sill transitions. Instead, in glacial domains, the stress conditions imposed by the variable vertical pressure of the ice cap result in higher tensile stress accumulation and displacement in stiff layers which they primarily control sill emplacement.

Delamination mechanism in CF/EPOXY with open hole under mode II loading at different distances

This research addresses limitations in current aviation composite assembly techniques, often constrained by certification challenges. To enhance bonded composite components, open holes are frequently introduced, leading to increased vulnerability to delamination, a prominent failure mode in composite laminates. This study focuses on observing the impact of open holes on the mode II behavior of composites under various distances and hole diameter conditions. Results illustrate distinct load–displacement curves influenced by hole size, with shorter distances accelerating crack propagation, evidenced by reduced elastic regions and lower load values. Analyzing specimen appearances and crack patterns highlights stress concentration at the hole, influencing initiation and propagation. In the absence of a hole, cracks exhibit a zig-zag pattern near the loading point, while with a hole, they concentrate around it. Elastic region length varies with the pre-crack-to-hole distance, indicating accelerated crack propagation in shorter distances. This study underscores the direct influence of hole size on load values, emphasizing its pivotal role in determining composite mechanical properties. This research provides valuable insights into hole characteristics’ interplay with delamination behavior in carbon fiber-reinforced composites, essential for optimizing aerospace component design and structural integrity.

Numerical Modeling of Melting Processes During Slab Break-off: Insights Into Tectonic Setting for Massif-Type Anorthosites

Abstract The concept that lithosphere detachment or break-off has long been conceived as a viable mechanism to explain prominent geological phenomena in Earth’s crust and the surface. One of the strengths of slab delamination mechanism is that it can account for the extensive magmatism in active orogenic belts due to the upwelling of the asthenosphere after the slab break-off. However, in the last 20 years, geodynamic simulations show that the inflow of the asthenosphere upon slab break-off is insufficient to cause significant melting of the overriding lithosphere adjacent to the slab window. The primary reasons include the occurrence of slab break-off at a location that is too deep to effectively heat the overriding lithospheric mantle. Another factor is the presence of a thin film of crustal material that is retained during the slab break- off, inhibiting a significant thermal perturbation within the lithosphere. In this work, we couple petrological–thermomechanical simulations with magmatic melting processes to examine the lithospheric melting and surface lithological expression associated with slab break-off. Our work shows that in the early Earth when the mantle temperature is relatively higher, shallow slab break-off can give rise to significant lithospheric melting during the development of slab break-off. Moreover, because the slab becomes weaker in the earlier hotter mantle, it may break-off prior to the stage of continental collision, thus the magmatism it induced may not give a direct constraint on the time of continental collision. Our study has implications for the interpretation of geological and tomography studies in orogenic belts. It also provides insights into reconciling conflicts between geodynamic and geological studies regarding slab break off-induced melting and magmatism.

Understanding and mitigating delamination in composite materials: A comprehensive review

Delamination significantly undermines the integrity and performance of composite materials, impacting their application in engineering structures. This comprehensive review synthesizes current research on the mechanisms of delamination in composite materials, with a focus on identifying critical factors contributing to this failure mode. It also examines recent advances in detection, prediction, and mitigation strategies. Key findings include the identification of manufacturing processes, moisture absorption, and mechanical loading as primary initiators of delamination. Additionally, innovative methodologies for delamination prediction and prevention are highlighted, showcasing advancements in experimental techniques and computational modeling. This review underscores the importance of understanding delamination to enhance the durability and reliability of composite structures. This analysis aims to guide future research directions and inform the development of more resilient composite structures.

An Oxide Growth-Coupled Viscoplasticity Model and Its Application to Interfacial Stress Analysis near an Air Hole within a Thermal Barrier Coating

Strength assessment for thermal barrier coatings (TBCs) is vital in the safety design of hot-section components in engines. However, several crucial factors, including thermally grown oxide (TGO) growth and creep–plasticity interaction, have been less considered in thermo-mechanical analyses for TBCs near air holes. In this study, a unified viscoplastic constitutive model incorporating TGO growth is developed and integrated into a finite element framework. The model considers multiple factors, including TGO growth, creep–plasticity interaction, interface undulation, and temperature gradient. Additionally, an analytical solution for the non-uniform temperature field of a TBC is derived. The model is then applied to calculate interfacial stresses and accumulated strain energies in the TBC near an air hole, which promote interface debonding. The obtained results can be utilized to investigate the mechanisms of hole edge delamination in TBCs, considering the combined effects of multiple complex factors. A competition for the potential failure initiation location is revealed between the first oxide layer and the evolving TGO/bond coat interface. The developed viscoplasticity model demonstrates effective capability in modelling a range of dynamic behaviors that collectively contribute to hole edge delamination failure.

Delamination of Plasticized Devices in Dynamic Service Environments.

With the continuous development of advanced packaging technology in heterogeneous semiconductor integration, the delamination failure problem in a dynamic service environment has gradually become a key factor limiting the reliability of packaging devices. In this paper, the delamination failure mechanism of polymer-based packaging devices is clarified by summarizing the relevant literature and the latest research solutions are proposed. The results show that, at the microscopic scale, thermal stress and moisture damage are still the two main mechanisms of two-phase interface failure of encapsulation devices. Additionally, the application of emerging technologies such as RDL structure modification and self-healing polymers can significantly improve the thermal stress state of encapsulation devices and enhance their moisture resistance, which can improve the anti-delamination reliability of polymer-based encapsulation devices. In addition, this paper provides theoretical support for subsequent research and optimization of polymer-based packages by summarizing the microscopic failure mechanism of delamination at the two-phase interface and introducing the latest solutions.

Evaluation of the Ejection Pressure for Tracking Internal Cracks during Compaction in Bilayer Tablet Formulations Using Experimental and Finite Element Methods.

This study aimed to evaluate the ejection pressure and the correlation of the findings with the occurrence of internal cracks within bilayer tablets (BLTs) consisting of metformin HCl (MF) and evogliptin tartrate (EG). Then, the mechanism of tablet failure was provided by the finite element method (FEM). The ejection pressure and the difference in diameter depending on MAIN-P were evaluated to understand the correlation between ejection pressure and change in the BLT internal structure. The ejection pressure and the difference in diameter increased as the MAIN-P increased, then steeply decreased from 350 MPa to 375 MPa of MAIN-P, despite there being no pattern in compaction breaking force and porosity. The mechanical integrity at the BLT interface was weakened by internal cracks, reducing ejection pressure. The stress distribution analysis during the compression revealed that crack formation caused by entrapped air located at the center of the BLT interface may not propagate due to concentrated stress, which promotes a tight bond at the edge of the BLT. Furthermore, complete delamination can occur in the ejection process due to localized and intensive shear stresses at the BLT interface. These findings indicate that the mechanisms of internal cracking and delamination were successfully confirmed by FEM simulation. Moreover, measuring ejection pressure before BLT manufacturing can prevent invisible tablet cracks without damaging the tablets.

A lower crust shear zone facilitates delamination and continental subduction under the Apennines

Physical properties and structure of the lithosphere are the first step to constrain the evolution of mountain belts. Here we show detailed shear wave velocity profiles of the lithosphere in the Apennines that clarify a controversial aspect of continental subduction: the intricate mechanism of crust delamination from the downgoing plate. From the analysis of complete and dense teleseismic Receiver Function data set, we find that the delamination of the continental lithosphere is favored by the development of a low seismic shear wave velocity zone in the middle-lower crust. We observe a double Moho below the external portions of the present mountain range, suggesting the progressive formation of the shallow interface. The delamination edge is located in the forearc, far eastward than expected, implying that the re-equilibration of the thermal unbalance, generated by the mantle substitution, may last 10-7 Myr.

Experimental Investigation of the Influence of Various Wear Parameters on the Tribological Characteristics of AZ91 Hybrid Composites and Their Machine Learning Modeling

Abstract In the current work, the AZ91 hybrid composites are fabricated through the utilization of the stir casting technique, incorporating aluminum oxide (Al2O3) and graphene (Gr) as reinforcing elements. Wear behavior of the AZ91/Gr/Al2O3 composites was examined with the pin-on-disc setup under dry conditions. In this study, the factors such as reinforcement percentage (R), load (L), velocity (V), and sliding distance (D) have been chosen to investigate their impact on the wear-rate (WR) and coefficient of friction (COF). This study utilizes a full factorial design to conduct experiments. The experimental data was critically analyzed to examine the impact of each wear parameter (i.e., R, L, V, and D) on the WR and COF of composites. The wear mechanisms at the extreme conditions of maximum and minimum wear rates are also investigated by utilizing the scanning electron microscope (SEM) images of specimen's surface. The SEM study revealed the presence of delamination, abrasion, oxidation, and adhesion mechanisms on the surface experiencing wear. Machine learning (ML) models, such as decision tree (DT), random forest (RF), and gradient boosting regression (GBR), are employed to create a robust prediction model for predicting output responses based on input variables. The prediction model was trained and tested with 95% and 5% experimental data points, respectively. It was noticed that among all the models, the GBR model exhibited superior performance in predicting WR, with mean square error (MSE) = 0.0398, root-mean-square error (RMSE) = 0.1996, mean absolute error (MAE) = 0.1673, and R2 = 98.89, surpassing the accuracy of other models.

A new mechanism based cohesive zone model for Mode I delamination coupled with fiber bridging of composite laminates

Based on identification of the two distinguishing delamination mechanisms within the two delamination zones associated with Mode I fracture toughness testing of composite laminates using the well-known ASTM standard double cantilever specimen (DCB), a new mechanism based cohesive zone model (MB-CZM) is proposed in this work. Overcoming the limitations with the widely used superposed cohesive zone models, the proposed MB-CZM develops two traction-separation relations to individually represent the two distinctive delamination mechanisms. One for the quasi-brittle linear elastic behavior of composite material and another for the nonlinear characteristics of fiber bridging which is commonly simplified with tri-linear to multi-linear approximation in the previous cohesive zone models (CZMs). Energy decomposition is carried out based on different damage and toughening mechanisms associated with delamination initiation and propagation. The proposed new MB-CZM is implemented in the finite element analysis via two UMAT subroutines and used in the numerical simulations. The good agreement of the simulation results with the experimental results provides the verification and demonstration of the capabilities of the proposed MB-CZM.

Degradation of cathode in air and its influences on direct recycling

Delamination has been widely used in direct recycling of spent lithium-ion batteries (LIBs) as the first step to harvest cathode materials from cathodes. The variations of the recycling performance have been documented in many studies. The main mechanism of delamination is the inactivation of bonding forces provided by the polyvinylidene fluoride (PVDF) binder. It is believed that the storage environment (air exposure time) will affect the performances of delamination to some extent. Three representative methods (direct calcination, pressure washing, and NMP solvent extraction) for delamination were studied to elucidate the effect of air exposure time on delamination efficiency. The peel-off efficiency (98–99%) of the direct calcination method was barely influenced by air exposure time. The pressure washing system or NMP solvent extraction method also exhibited high peel-off efficiency using samples after a long air exposure time (1 month), however these methods may have problems regarding Al contamination, i.e., 11.5 mg/g of pressure washing system and 134.4 mg/g of NMP solvent extraction. Results suggest that enhanced adhesion (0.11 MPa/month) could be a potential reason why air contact time affects delamination, with O2 and/or H2O acting as contributors. This finding may help to maximum performance of delamination, as it highlights the importance of storage conditions of the spent LIBs prior to direct recycling.

Analysis of Thermomechanical Delamination Mechanisms in Segmented High-Temperature Protective Coatings and Design Maps for the Durable Coatings

Analysis of Thermomechanical Delamination Mechanisms in Segmented High-Temperature Protective Coatings and Design Maps for the Durable Coatings

High deformation and delamination mechanisms explained through mesoscale and nanoscale phenomena in pearlitic steel wires

Pearlitic steel wires subjected to severe cold drawing deformation exhibit a unique combination of high strength and excellent ductility, making them suitable for critical applications such as hanging bridge cables, crane cables and tire cord. Torsion tests up to rupture are commonly used in the industry for quality control purposes. A flat fracture surface is indicative of wire aptitude, while a delaminated surface suggests degradation of mechanical properties. This paper aims to expand the understanding of the structural evolution and deformation mechanisms that occur during wire drawing, as well as the origin of delamination problems. Different deformation and strengthening mechanisms are identified and discussed, applying different microscopy techniques (optical microscopy, scanning electron microscopy, electron backscatter diffraction), synchrotron diffraction and atom probe tomography. The information is correlated with the cementite stability on the structure studied at meso, nano, and atomic scale, reaching an understanding of the compositional evolution of cementite and ferrite even at the very lowest level. All the obtained information, including thermal analysis and thermodynamic simulation results, allow to identify the deformation mechanisms present during cold drawing and at the delamination process. In addition, the compositional evolution of cementite and ferrite is also clarified by atom probe tomography.

Formation and strengthening mechanism of kink bands in an ultra-coarse-grained Fe-Cr-Al alloy

Fe-Cr-Al alloys, owing to their absence of allotropic transformation, require multiple cycles of rolling and recrystallization annealing processes to achieve substantial grain refinement, ultimately leading to the attainment of outstanding mechanical properties. However, the corresponding manufacturing costs will also increase greatly. In this work, we have proposed a new microstructural preparation process. Simply using warm rolling for an ultra-coarse-grained Fe-Cr-Al alloy to introduce lamellar kink bands (KBs) into the matrix, the mechanical properties can be significantly improved. By using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM), and combined with Schmid factor (SF) calculation, the formation mechanism of KBs has been revealed. When the slip plane and direction are nearly perpendicular to the loading force direction (LFD) during the continuous grain rotation, the dislocation wall will evolve into the KBs boundaries. Simultaneously, a huge orientation separation between the matrix and KBs will be produced. As strain continues to rise, KBs undergo a transformation, transitioning from low-angle-grain boundaries (LAGBs) to high-angle-grain boundaries (HAGBs), occasionally adopting a configuration as coincident site lattice (CSL) boundaries with reduced interface energy. Results of the tensile test, cyclic loading-unloading-reloading tensile test, and the strengthening calculation show that KBs can pronouncedly enhance the strength by their heterogeneous refinement on the original grains and hetero-deformation induced (HDI) strengthening effect from the dislocation density discrepancy between the matrix and internal KBs, the grains containing KBs (KBGs) and the grains without KBs (or KBs-free-grains, KFGs). The theoretical calculation value of the strengthening contribution from KBs on yield strength can be up to 225.5 MPa, with a minimum value exceeding 153 MPa. On the other hand, the ductility can be retained to some extent through stimulating the KBs boundary delamination mechanism. The present study provides a low-cost and feasible processing method for fabricating Fe-Cr-Al alloy with high strength and good ductility.

Ballistic and delamination mechanism of CFRP /aluminum laminates subjected to high velocity impact

This work focus on the experimental study of ballistic and delamination mechanism on carbon/epoxy laminates with [-45/90/45/0] stacking sequence. A series of impact tests were carried out on the monolithic CFRP and Al/CFRP/Al laminates targets. The two targets were compared in terms of ballistic limit, energy absorption, penetration process, damage mechanism and interfacial delamination. Results showed that the Al/CFRP/Al laminates with equal thickness had better ballistic performance than that of the monolithic CFRP laminates. The delamination of adjacent layers was mainly controlled by bending moment, uneven stress distribution of interface and mismatch of wave impedance between layers with different lay-up directions. The shear wave propagated between fiber layers in different layering directions, resulting in interlayer crack extension.

3D numerical investigation on delamination behavior of the epoxy impregnated REBCO pancake coil

Superconducting coils made of rare-earth-barium-copper-oxide (REBCO) coated conductor (CC) exhibit superior electromagnetic performance. Employing epoxy impregnation can improve the structural integrity and mechanical property of the superconducting coils. However, due to the extreme work environment and weak adhesion strength of REBCO CC, the delamination induced by radial thermal stress and electromagnetic force significantly affects the electromagnetic property and the reliability of the superconducting coil. This study proposes a three-dimensional thermal-electromagnetic mechanical delamination model that incorporates the cohesive zone model to investigate the delamination mechanisms in epoxy impregnated REBCO pancake coils during the cooling and coil operation processes. The simulation employs a three-parameter Weibull distribution to account for the inhomogeneity of transverse tensile strength in the CCs. The delamination behavior and mechanisms of the coils under different conditions are analyzed. The simulation results show that the model considering random adhesion strength proves to be more effective in representing the delamination behavior of the coil. And large tensile radial stresses caused by thermal stresses and electromagnetic forces lead to the delamination behavior of the coil during cooling and operation. The main reason for the tensile radial stress is the mismatch in the thermal contraction among components of the coils during cooling process. Furthermore, we investigate the influence of the thermal expansion coefficient (CTE) and thickness of the mandrel, the CTE and prestress of the overband and the initial localized damage. The results indicate that these factors significantly affect the tensile radial stress and the extent of delamination in the windings. And the extent and distribution of delamination is related to the stress release caused by delamination to a certain degree.

Study on the settlement and delamination mechanism and acoustic emission characteristics of mixed aggregate cemented backfill

To study the effects of waste rock (WR) contents on the delamination and mechanical characteristics of the cemented backfill, the backfill specimens with 40%-80% WR content were prepared based on the stacking density of mixed aggregate. The characteristics of the WR distribution inside the cemented backfill with various WR contents were examined by scanning the sections images of the specimens. The strength and damage properties of the cemented backfill were investigated by uniaxial compression acoustic emission (AE) tests, and the strength and damage evolution mechanisms were explained by microstructure testing experiments. The results show that the viscosity and yield stress of the filling slurry gradually decreased with the contents of WR increased, and the WR settlement and delamination more obvious. The uniaxial compressive strength (UCS) has the same trend as the stacking density of the mixed aggregate, showing the trend of “increased first and then decreased” with the content of WR increased. When the content of WR was 60%, it had the highest UCS. As the content of WR increased, the fracture area at the interface of WR and cementitious matrix gradually increased, and the extrusion between coarse aggregates became more obvious, leading to more complex crack extension and higher AE cumulative energy. The main products of hydration in the cemented backfill were calcium silicate hydrated (C-S-H gels), ettringite (AFt), and calcium hydroxide (Ca(OH)2). The specimens with higher content of hydration products have better cementation among aggregate particles, denser microstructure, and higher compressive strength of cemented backfill.

Tribological behavior of ZK60Gd alloy reinforced by SiC particles after precipitation hardening

In this research, the effect of precipitation hardening on the tribological behavior of the ZK60Gd/SiC composite was studied. For this purpose, ZK60Gd alloy containing with 5 and 10 wt% SiC were produced with stir casting method. The microstructure characterization of the samples showed the wide distributions of Mg7Zn3 and Gd(Mg0.5Zn0.5) precipitates were formed during casting. The results of hardness measurement after precipitation hardening at different temperatures showed that the hardness peck was obtained at 175 °C. The wear tests with different loads (10, 40, 60, 90, and 120 N) and velocities (0.1, 0.3, 0.6, and 0.9 m/s) were performed on the as-cast and heat treated sample at 125, 175, and 225 for 12 h. Between the different precipitation hardening conditions, the precipitation hardened samples at 175 °C had the highest hardness values and least wear rate. The sample containing 10% reinforcement had the least wear rate between the unreinforced alloy and the composites. The results showed that abrasive, adhesive, delamination, MML, and fatigue wear mechanisms were the dominant wear mechanisms for the composite samples. In contrast, the dominant wear mechanism for the unreinforced samples was abrasive, adhesive, delamination, MML, and plastic deformation.

Numerical study of thermomechanical delamination mechanisms in segmented high-temperature coatings

This work addresses the thermomechanical delamination mechanisms in segmented multilayered high-temperature coatings system using computational fracture mechanics approach. A representative unit cell model is presented, where the thermomechanical load is generated by combining uniform temperature changes and boundary-loaded displacements. The model is used to analyze coatings over a broad range of material properties, geometries, and loads. The findings suggest that, for a given coatings system, the mechanical load carried by the top-coat layer is the only force that drives delamination developing along the top-coat/bond-coat interface. The introduced multiple vertical cracks lead to stiffness release over a limited region, resulting in reductions in stress and delamination driving forces within that region. An empirical equation is established using multiple regression analyses to evaluate the delamination driving forces. Accordingly, the importance of the influential factors on the delamination is ranked, and design maps are constructed to facilitate the development of durable coatings.