Mechanical Defects Research Articles

Computational Design of Durable and Selective Double Atom Catalysts Toward the Electrochemical NH3 Production: Role of Carbon Defects

Electrochemical NH3 production through nitrogen reduction reaction (N2RR) has received much attention as an energy-efficient way to produce ammonia, which is one of CO2-free hydrogen carriers. Note that electrochemical N2RR is carried out under mild temperature and pressure conditions, unlike the conventional Haber-Bosch process for chemical NH3 production, which requires a lot of energy due to the high temperature and pressure conditions. In recent years, the concept of double atom catalysts (indicated DAC) has been proposed to improve the reactivity of catalyst owing to the maximized utilization and 100% dispersion of active sites. The main problems in the development of DACs are the poor stability [the dissolution of double atoms into electrolyte and agglomeration of double atoms] and the low selectivity [lower onset potential for N2RR than HER (hydrogen evolution reaction)]. In this study, by using density functional theory (DFT) calculations, we examined the role of carbon defects (di, tri, quad vacancies) in graphene in enhancing the stability and selectivity in single and double atom catalysts (Ru, RuRu, and RuFe) and screened the novel double atom catalysts which have high selectivity to NH3 and durability at reaction conditions by ligand and support engineering. First, we found the optimal carbon defect structure to suppress the dissolution and agglomeration of double atoms and unraveled the factors to enhance the selectivity to N2RR over HER. Second, we developed the multiscale model to design the selective and durable double atom catalysts by identifying the descriptors to represent the durability and selectivity of double atoms catalysts. Next, we computationally screened the novel DACs (consisting of transition metals) by using the developed multiscale model. Finally, through the electronic structure calculation, we elucidated the underlying mechanism of defect in determining the durability and selectivity of double atom catalyst. Our study can provide the design factors to efficiently engineer the carbon defect and double atom in the development of NH3 production catalyst.

Analysis, simulation and experimental research on the mechanisms of lantern-shaped strand defects in the conductor construction of transmission line

This paper focuses on theoretical, numerical simulation, and experimental research on the lantern-shaped strand defect that arises in tension stringing constructions of large-section conductors. Starting from considerations for factors such as the construction environment and the characteristics of the conductor passing through blocks, this paper presents the causes of conductor torque generation and analyzes the distribution of axial forces on the outmost layer strands and the outmost adjacent layer strands of the conductor when subjected to bending and twisting. Taking into account the contact forces between strands in different layers, this paper thoroughly examines the mechanical causes that lead to the occurrence of the lantern-shaped strand defect in conductors. It concludes that the axial compression and the external contact force acting on the outermost adjacent layer strands are crucial in the formation of the lantern-shaped strand defect. To numerically simulate the lantern-shaped defect, a finite element model is developed to replicate the passage of a 1250 mm2 large-section conductor through the block system. Furthermore, considering actual working conditions, a test equipment is designed and constructed to replicate the lantern-shaped defect. The shape and size of the lantern-shaped defect obtained from the tests exhibited a substantial agreement with the simulation results, suggesting concordance between theoretical analysis and real situation. This research methodology can be used to analyze defects in conductors with varying sections, serving as a theoretical foundation for the prevention and control of construction defects in conductors.

Mechanical Properties of Vcrmn and Vcrmnti High Entropy Alloys

In this research, magnetron sputtering is employed to fabricate thin films of high entropy alloys. The target materials are derived from VCrMn and VCrMnTi systems. The focus is to pinpoint suitable candidates for robust and long-lasting beam exit windows in e-beam accelerators. The selection process considers their inherent characteristics, their capacity to dissipate power, and how they respond to irradiation in terms of mechanical traits like hardness, ductility, defect density, and strength.For the bulk alloy samples of VCrMn and VCrMnTi, a sequence of nanoindentation tests has been executed to evaluate hardness and elastic modulus. The outcomes reveal that both the hardness and modulus are notably greater than those of any individual metal samples. It is anticipated that fabricated alloy films with same compositions will exhibit robust qualities in terms of mechanical properties, including ductility, defect density, and strength. The incorporation of additional titanium (Ti) alloying elements into the high entropy alloys (HEAs) of VCrMn is projected to enhance electron transmission.The fabricated films have undergone thorough analysis and testing to comprehend their microstructural attributes and chemical composition which involves the utilization of SEM with EDS, FESEM, AFM to investigate microstructural and surface properties of the films. Subsequently, X-ray diffraction has been employed to acquire insights into the morphology and lattice orientation of the films.

Synchrotron X-Ray Topography Studies for Defect Formation at the Early Stage of PVT-Grown 4H-SiC Crystals

Silicon Carbide (SiC), typically 4H-SiC, is replacing conventional silicon materials for high power and high frequency applications due to its excellent electrical and thermal properties [1]. However, high quality SiC wafers with low defect density are still in urgent need for automotive and energy saving applications. SiC wafers are obtained from bulk growth by physical vapor transport (PVT) method and considerable efforts have been expended to optimize growth process to lower defect densities. One major approach is the study of initial stages of crystal growth as most defects are nucleated at this stage and propagate into the boule. Ailihumaer et al [2] demonstrated the behaviors of threading edge dislocations (TEDs), threading screw dislocations (TSDs)/threading mixed dislocations (TMDs), and basal plane dislocations (BPDs) across the seed/newly grown layer interface in PVT-grown 4H-SiC. Sanchez et al [3] revealed the nucleation of TEDs and TSDs at the initial growth stage in PVT-grown SiC.However, more detailed investigations are still in demand for PVT grown 4H-SiC crystals during initial stage of growth. This study investigates 4° off-axis 4H-SiC wafers with several hundred microns of initial-stage growth PVT method. Synchrotron X-ray topography (SXRT) technique is employed and shows dramatically modified defect distribution across the seed/newly grown layer interface (Figure 1). The formation of Shockley stacking fault starting at initial stage of crystal growth is suggested as partial dislocations running along <11-20> directions on basal plane are observed to form rhombus shapes (Figure 2). Prismatic slip is observed to take place near the wafer edges and prismatic dislocations undergo cross slip to form unique dislocation configurations. A statistical analysis on defect changes across the seed/newly grown layer is being carried out and the results will be reported. These results will be complemented by observations from Nomarski optical microscopy (NOM) and Raman Spectroscopy studies to propose the formation mechanism of defects across the seed/newly grown layers.

Revealing the mechanism of oxygen vacancy defect for CO2 adsorption and diffusion on CaO: DFT and experimental study

The calcium looping is a promising technology to achieve industrial CO2 capture, and the introduction of oxygen vacancy can promote the CO2 capture reactivity of CaO-based sorbents. In this work, DFT calculations were performed to investigate the CO2 adsorption by CaO in the presence of oxygen vacancy defect. The presence of oxygen vacancy reduces the band gap of CaO surface, which results from the delocalization of Ca 2p orbital. Besides, the electron accumulation at the oxygen vacancy occurs due to the unsaturated Ca-O bonds, and the reaction possibility is promoted neighbouring the defect. The top site of oxygen vacancy defect of CaO is favourable for CO2 adsorption. The adsorption energy of CO2 on CaO with oxygen vacancy achieves − 2.52 eV, which is 1.81 times as high as that on pristine CaO. Due to strong interaction between CO2 and CaO with oxygen vacancy, CO2 migration from this site is more difficult, while the following diffusion is more prone to occur. In the presence of steam, CO2 adsorption energy is enhanced to − 2.70 eV on CaO with oxygen vacancy, and the distance from CO2 radical to surface is intuitively reduced, which results from the electrons donated from defect and neighbouring Ca atoms, while CO2 diffusion difficulty is increased. This work provides an incisive investigation for structural, electronic, and thermodynamic characteristics of CO2 adsorption and diffusion on CaO in the presence of oxygen vacancy defect, and it can shed light on rational synthesis and functional design of surface-active sites of CaO-based sorbents.

Experimental and theoretical investigations on the lattice defects and sintering atmosphere tuning the colossal permittivity of SrTiO3 ceramics

The Sr0.995La0.005TiO3 ceramics were fabricated with traditional solid-state methods under diverse sintering atmospheres. The dielectric properties have a significant correlation with the sintering atmosphere, while showing favorable temperature and frequency stability. As sintered in a mixed hydrogen-nitrogen atmosphere, Sr0.995La0.005TiO3 ceramics exhibited a colossal permittivity (ԑr ∼ 31307), low dielectric loss (tanδ ∼ 0.038) and good frequency stability synergistic temperature stability (−70 °C-180 °C, ΔC/C25°C ≤ ±15 %). The association mechanism of oxygen vacancies, lattice defects, and dielectric characteristics is evaluated in the context of experiments and first-principles. The phase structure and microstructure analysis revealed that the ceramics contained a two-phase structure with a SrTiO3 phase and a TiO2 second phase. The analysis of elemental valence and dielectric characterization demonstrated that defective dipoles, oxygen vacancies, and defect clusters resulting from non-homogeneous ion substitution are the major reasons for contributing to the colossal permittivity and low dielectric loss of the ceramics. This revealed that the electron-pinned defect dipole (EPDD) effect dominates in Sr0.995La0.005TiO3 ceramics. In addition, it can be established that the SrTiO3 phase and TiO2 phase contribute to the EPDD effect simultaneously, with SrTiO3 main phase taking the main role. According to the ELF plot analysis, when the content of oxygen vacancies is high, electrons accumulate at oxygen vacancies and defect clusters, leading to a high localization of electrons, which contributes to colossal permittivity and low dielectric loss of ceramics. The results are promising in colossal permittivity (CP) materials.

Material Removal Mechanism and Evolution of Subsurface Defects during Nanocutting of Monocrystalline Cu

Multigroup large-scalenanocutting models of monocrystalline Cu were established by molecular dynamics simulations to investigate the influence of cutting parameters on the material removal mechanism. The formation and distribution of subsurface defect structures were revealed, and the evolution behavior of the complete prismatic dislocation loop was analyzed in depth. It was demonstrated that the chips and machined surface of monocrystalline Cu were mainly formed under the coupling effect of shearing and extrusion forces. A diamond tool with a larger edge radius or a negative rake angle could produce a noticeable suppression on the chip formation. The corresponding relationship between the location of defect atoms and the distribution of von Mises stress was studied, which indicated that the shear stress would become larger at the subgrain boundaries, dislocation lines, and the amorphous atoms than that in their nearby regions. The complete prismatic dislocation loop was formed by cross-slip between two sets of stacking faults; meanwhile, the generated multiple Lomer–Cottrell locks hindered its movement and promoted the work-hardening phenomenon. These research results are of great theoretical value to enrich the nanocutting mechanism and technology of plastic materials.

Biomechanical behavior of deep anterior lamellar keratoplasty: a finite element analysis

Deep Anterior Lamellar Keratoplasty (DALK) is a surgical procedure used to restore sight and manage corneal diseases by replacing cloudy corneal tissue with allogeneic normal corneal tissue or artificial corneal material. However, the limited availability and mechanical defects of artificial corneal materials pose challenges in DALK. To predicting postoperative mechanical behavior of Deep Anterior Lamellar Keratoplasty (DALK), a three-dimensional finite element model of the postoperative DALK cornea with suture holes was developed. The postoperative corneal displacement and von Mises (VM) stress changes were also simulated under varying depths of cut (DOC: 0.16-0.26 μm), intraocular pressure (IOP: 12, 15, 18 mmHg), and central corneal thickness (CCT: 420-620 μm). The model indicated that higher IOP and CCT were associated with improved postoperative corneal stability. The postoperative corneal displacement increased from the edge to the center, while the maximum VM stress value occurs at the corneal suture hole. Corneal displacement and VM stress decrease with increasing CCT and decreasing IOP. DOC has a slight effect on corneal displacement and VM stress, with an overall positive relationship. The model has potential application in the preoperative assessment of risk in keratoplasty.

Defects in Perovskite Solar Cells and Their Passivation Strategies

AbstractDue to their excellent photoelectric conversion efficiency and low preparation cost, perovskite solar cells (PSCs) have attracted much attention from researchers and developed rapidly in the past decade. However, the stability and efficiency of perovskite photovoltaic devices still need to be improved for their practical applications. It is mainly because the perovskite thin films are inevitably defective to some extent (such as points defects and extrinsic defects), leading to the occurrence of non‐radiative recombination (NRR) inside the device and at the interface, which is closely related to the stability and efficiency of perovskite materials. Therefore, exploring reliable passivation strategies is essential to overcome the adverse effects of NRR losses of such point defects. Here, this article summarizes the perovskite solar cells, including the crystal structure and calculations of electronic properties of perovskites, composition, and principles of operation of perovskite solar cells, and more importantly, different passivation strategies, including Lewis acid‐base passivation, anionic and cationic passivation, polymer passivation, and alkyl halogen ammonium passivation for the defects involved in perovskite materials. The passivation effects of these strategies and their regulation mechanisms of point defects involving perovskite materials are also presented. We also discuss the intrinsic relationship between crystal defects and device stability and look forward to feasible defect passivation strategy options for future research.

Experimental and optimization of die casting parameters on Al-Si alloy with snail shell reinforcing agent

The demand for aluminum in various fields continuously grows, including in the automotive industry. In this industry, aluminum is used as the material for the spare part. Therefore, aluminum with high mechanical properties and low casting defects is required. One of the available alternatives for producing excellent aluminum is through aluminum casting, including die casting. Die casting offers low cost in mass manufacturing of complex shaped components with acceptable casting results. Further, the selection of die-casting parameters and the addition of reinforcing elements can also improve the mechanical properties of aluminum. In this study, we strengthened the Al-Si matrix using High Pressure Die Casting process with particles from snail shell powder (calcium carbonate). Further, this study also explores the mechanical properties and microstructure of the product produced through experiment and optimization. The optimization was adopted to identify the optimum parameter. For the optimization, we used the Taguchi method. Our analysis results suggested that the reinforcing agent from the snail shell powder has the CaO and Ca(OH)2 phases, with a crystallite size of 106.59 nm. The morphology of the shell powder reinforcing agent showed the presence of agglomeration and interconnected structures, such as skeletons, with average particle size of 0.4 micro. The functional group of the shell powder reinforcing agent showed the OH band during the water absorption by CaO, along with asymmetric C–O with vibration from the carbonate group and Ca–O bound. The most excellent hardness level was identified from T8, with 86.33 HRB and die casting parameters of 0.15% reinforce agents, 750 °C temperature injection, and 50 MPa pressure. Meanwhile, the best tensile strength was found from the T9 sample, with 109,95 MPa and die casting parameters of 0.15% reinforce agents, 800 °C temperature injection, and 60 MPa pressure. Microstructure on the used piston die casting sample with snail shell powder reinforcing agent showed the presence of Al, Si, dendrite, and Al4Ca phases. The multiple response analysis on the three factors indicated that the reinforcing agent presented the most significant effects toward the tensile strength and hardness, followed by pressure and temperature injection. Meanwhile, the Taguchi method and ANOVA results showed the optimal parameter die casting was obtained from a combination of 0.15 wt% reinforce agent, 800 °C injection temperature, and 50 MPa pressure. A multiple linear regression mathematical model for tensile strength and hardness was developed from the observed data. In regression model, the value of R2 of tensile strength 74.02% and R2 of the hardness is 95,18% Thus, the developed model can be effectively used to predict the tensile strength and hardness

Tuning visible light-driven photocatalytic NO removal: Insights from glucose-derived CQDs/ZnO nanorods composite

The potential of visible light photocatalysis in mitigating environmental pollutants has gained significant attention. In this study, we investigate the photocatalytic NO removal efficiency of oxygen defect-rich zinc oxide nanorods (ZnO NRs), facilitated by the incorporation of carbon quantum dots (CQDs) under mild conditions. The successful integration of CQDs with ZnO NRs represents a novel and sustainable approach for efficient NO removal under visible light irradiation. Notably, the CQDs/ZnO NRs shows a substantial increase in NO removal efficiency (71.9%), low toxicity (2.7%) and durability (only 7.7% efficiency reduction after five cycles). The synergetic effects of CQDs and oxygen defects within the ZnO NRs structure, which broadens the light absorption spectrum, facilitates electron separation, thus enhanced photocatalytic NO removal. Furthermore, photoluminescence, active species trapping experiments, and electron spin resonance analysis have confirmed the generation of hydroxyl radicals (•OH) and superoxide radicals (•O2–) during the excitation of electrons. Finally, the synergetic mechanism of CQDs and oxygen defects in ZnO NRs for amplifying visible-light-driven photocatalytic NO removal was elucidated.

On the co-nucleation of adjoining twin pairs at grain boundaries in hexagonal close-packed materials

This work addresses the formation of adjoining twin pairs (ATPs) at grain boundaries (GBs) in hexagonal close-packed (hcp) metals from the perspective of the co-nucleation (CN) of pairs of deformation twins. A continuum defect mechanics model is proposed to investigate the energetic feasibility of the CN of ATPs resulting from the dissociation of GB dislocations. Application of the model to a set of GBs in Mg reveals that CN is largely preferred over the nucleation of a single twin variant for low misorientation angle GBs, which is consistent with previous experimental analyses. The CN events are subsequently analyzed considering the GB character, and the twin system alignment (m′) and Schmid factors to obtain better insights into the conditions governing the formation of ATPs via CN. The likelihood of CN even at low m′ values reveals that CN events could be responsible for the formation of ATP pairs in these scenarios.

Enhancing photostability of 2D Ruddlesden–Popper perovskite via molecular acceptor passivation of metallic lead defects

Two-dimensional (2D) Ruddlesden–Popper (RP) perovskites hold great potential for novel optoelectronic applications. However, their unconventional optoelectronic properties are often compromised by a vulnerability to light irradiation, which leads to the formation of metallic Pb (Pb0) defects. This study investigates the passivation mechanism of these Pb0 defects in phenylethylammonium lead iodide (PEA2PbI4) using a strong molecular acceptor, 2,2′-(perfluoronaphthalene-2, 6-diylidene) dimalononitrile (F6-TCNNQ). In situ x-ray photoelectron spectroscopy results demonstrate that F6-TCNNQ effectively removes the light-induced Pb0 states, leading to the recovery of photoluminescence intensity in photodegraded PEA2PbI4 samples and significantly improving the photostability of pristine PEA2PbI4. F6-TCNNQ protects the terrace edge of PEA2PbI4, which is the site of initial degradation, as evidenced by atomic force microscopy and scanning electron microscopy analyses. In situ ultraviolet photoelectron spectroscopy measurements confirm substantial electron transfer from Pb0 to F6-TCNNQ, causing the oxidation of Pb0 to Pb2+. Furthermore, the staggered energy level alignment prevents electron transfer from the valence band maximum of PEA2PbI4 to the lowest unoccupied molecular orbital of F6-TCNNQ, thereby preserving the pristine electronic structure of PEA2PbI4. These findings provide new insights into defect passivation in 2D RP perovskites and offer a design strategy for highly stable optoelectronic devices.

ELIMINATION OF THE DEFECTIVE LAYER AND STRESS CONCENTRATORS DURING MICROMACHINING OF HOLES IN THIN SHEET BLANKS OF METAL CELLULAR PANELS

Thin-sheet blanks made of aluminum (in particular, AMg2-N), titanium (VT-15, VT-19) or stainless (12X17) alloys are widely used in the production of honeycomb panels in the aviation and space industries. Foil (thickness 0.025-0.055 mm) is used for the production of fillers for cellular sandwich panels; it is pre-perforated with holes of 0.05-0.18 mm and laid out in a corrugated box with adhesive strips. The possibility of making holes by the laser jet method is considered, as it precedes the occurrence of mechanical damage and thermal defects of the surface adjacent to the treatment zone. It is shown that the Water Jet Guided Laser (WJGL) is an effective and efficient method of obtaining profile holes in the fillers of cellular panels and in the panels themselves, which is characterized by high productivity and allows obtaining holes without thermal and mechanical defects. The method can be used both for foil fillers and for metal panels made of stainless steel up to 1.5 mm thick.

The impact of oxygen-clustering on the transformation of electrochemically-derived graphite oxide framework

Oxygen-clustering in graphene oxide is the activated process of diffusion of oxygen functionalities: hydroxyls and epoxides, to form clusters and to trigger sp2 percolation, a key element for electrical conductivity. Impact of oxygen-clustering is thoroughly analyzed in electrochemically-derived graphite oxide (EGO), amine-functionalized frameworks (EGOF), and their pyrolyzed forms. Amine pillars within EGOF were suspected to amplify oxygen-clustering in EGOF as onset temperature of thermal decomposition was smaller in EGOF than in EGO. Thermochemical analysis proves that pillars within EGOF significantly augment oxygen-clustering aiding the reduction mechanism as inferred by the activation energy of thermal decomposition. Defective oxygen-clustering mechanism is evidenced using multiple techniques, including XRD, and is harnessed to enhance nitrogen doping. The pyrolytic morphological transformation from lamellae of EGOF into ravioli is revealed through SEM. A labyrinthic network of array prismatic dislocations provides stability to pyrolyzed EGOF ravioli whilst confining long chains of electron delocalization (localized π-orbitals), as unprecedently confirmed by HR-TEM/EELS and conductive AFM (C-AFM). Oxygen-clustering not only improves nitrogen doping in ravioli, but also improves density of array prismatic dislocations, which ultimately boosts Faradaic redox activity as observed in cyclic voltammetry (CV). Results show that Faradaic response originating from redox-active nitrogen groups predominantly relies on abundance of extended localized π-orbitals, which are geometrically and chemically confined within ravioli array prismatic dislocations. Our first-of-a-kind HR-TEM/EELS, C-AFM, and CV comparative and correlative analysis of pyrolyzed forms of EGO, EGOF, and their oxygen-clustered derivatives, confirms emergent role of confined electron delocalizations in amplifying Faradaic redox activity.

Troponin and a Myopathy-Linked Mutation in TPM3 Inhibit Cofilin-2-Induced Thin Filament Depolymerization.

Uniform actin filament length is required for synchronized contraction of skeletal muscle. In myopathies linked to mutations in tropomyosin (Tpm) genes, irregular thin filaments are a common feature, which may result from defects in length maintenance mechanisms. The current work investigated the effects of the myopathy-causing p.R91C variant in Tpm3.12, a tropomyosin isoform expressed in slow-twitch muscle fibers, on the regulation of actin severing and depolymerization by cofilin-2. The affinity of cofilin-2 for F-actin was not significantly changed by either Tpm3.12 or Tpm3.12-R91C, though it increased two-fold in the presence of troponin (without Ca2+). Saturation of the filament with cofilin-2 removed both Tpm variants from the filament, although Tpm3.12-R91C was more resistant. In the presence of troponin (±Ca2+), Tpm remained on the filament, even at high cofilin-2 concentrations. Both Tpm3.12 variants inhibited filament severing and depolymerization by cofilin-2. However, the inhibition was more efficient in the presence of Tpm3.12-R91C, indicating that the pathogenic variant impaired cofilin-2-dependent actin filament turnover. Troponin (±Ca2+) further inhibited but did not completely stop cofilin-2-dependent actin severing and depolymerization.

Localization of mechanical and electrical defects in dry-type transformers using an optimized acoustic imaging approach.

This paper presents an acoustic imaging localization system designed to pinpoint common defects in dry-type transformers by analyzing the unique sounds they produce during operation. The system includes an optimized microphone array and an improved multiple signal classification algorithm. Sound signal characteristics of typical defects, such as foreign object intrusion, screw loosening, and partial discharge, are investigated. A 64-element, 8-arm spiral microphone array is designed using a particle swarm optimization algorithm. The multiple signal classification algorithm enhances acoustic imaging quality in field environments by transforming the input from time-domain to preprocessed frequency-domain signals. The power spectra of subarray and main array are combined, forming the optimization algorithm's output. Experimental results demonstrate the system's effectiveness and accuracy.

Formation mechanism of surface defect during high-speed ball-end milling process of hardened die steel Cr12MoV

Formation mechanism of surface defect during high-speed ball-end milling process of hardened die steel Cr12MoV

Multiphysics and comparative analysis on failure detection in planetary gears

Gearbox monitoring is considered an important scientific focus for predicting preventative maintenance plans. In these systems, mechanical defects such as loading problems, eccentricity and torsional vibrations lead to shaft fatigue and other damage to various other mechanical components. Various methods have been developed to detect and identify the presence of defects in gearboxes. In this paper, we investigate the effect of gearbox faults on the current signal by defining an analytical correlation between the physical presence of the fault and the stator current. The theoretical development is supported by experimental measurements taken on a back-to-back planetary gearbox. Planetary gearbox faults result in the motor’s input torque oscillations, generating amplitude and frequency modulation (AM-FM). These modulations have an effect on stator current signals. The study of the stator current was followed by that of vibration signal and acoustic pressure taken simultaneously under the same operating conditions. This comparative investigation aims to present the differences between different techniques and highlight the efficiency of each.

Novel Diagnosis Method for GIS Mechanical Defects Based on an Improved Lightweight CNN Model With Load Adaptive Matching

Mechanical defects of GIS equipment seriously threaten power grid security, but on-site complex operating conditions create great challenges for defect diagnosis. Therefore, this paper proposes a novel diagnosis and state assessment method for GIS mechanical defects under varying currents. First, a time-frequency analysis method of GIS vibration signals based on neighboring mode noise suppression was proposed, and a defect type and severity diagnosis model with load adaptive matching was designed with the improved SqueezeNet (RF-SqzNet). Then, vibration datasets with different severities and currents of typical defects were established based on 110 kV GIS mechanical vibration platform. Finally, model validation and comparison analysis are carried out. Results show that the proposed method effectively mines feature and achieves accurate multiobjective diagnoses of the defect type and severity under varying currents, which is more accurate than traditional methods. The smaller model and faster computing speed are more suitable for edge deployment application.