Effect Of Loading Research Articles

Damaged mortise–tenon joint strengthened using an assembled spring–steel hoop based on a design of similar rotational stiffness

The excessive enhancement of rotational stiffness leads to an uneven distribution of rotational stiffness across the entire timber frame. This uneven distribution concentrates the load effect on the strengthened mortise–tenon joints (MJs), causing localized failure in advance. To address this issue, a reversible and non-destructive strengthening method for the damaged MJs is devised, involving the utilization of an assembled spring-steel hoop. The rotational stiffness of a strengthened MJ is derived from the springs that link the steel hoop of the beam and column, resembling the rotational stiffness of an intact MJ. A comparison of the measured moment-rotation curves of various types of MJ reveals that the rotational stiffness similarity necessitates the strengthened MJ's yield moment and ultimate moment, along with the associated rotation angles, to closely resemble those of the intact MJ. Secondly, a design methodology is developed for the assembled spring-steel hoop, which involves determining the parameters of the connecting spring. The comparative analysis of the hysteretic test results on multiple strengthened and intact MJs indicates that the strengthened MJs exhibit rotational stiffness deviations of less than 12.2 % during the elasticity stage and 6.6 % during the plasticity stage, in comparison to the intact MJs. A spring exhibits a lower ultimate extension compared to timber, leading to a maximum discrepancy of 37.5 % in the ductility coefficients between the strengthened MJs and intact MJs. The strengthened and intact MJs display similar patterns of stiffness reduction and energy dissipation progression.

Characterizing the spatial structure and aliasing effect of ocean tide loading on InSAR measurements

Ocean tide loading (OTL) displacements, shown as long-wavelength errors in Interferometric Synthetic Aperture Radar (InSAR), must be considered in large-scale applications. Despite efforts to explore the impacts of OTL on InSAR, most studies use individual interferograms and simple metrics, which fail to characterize the spatial structure of OTL. Moreover, the OTL contribution to InSAR time series remains relatively unexplored. The aliasing effect and related biases due to OTL, which are common to space-geodetic time series, are primarily theoretical with few practical observations for InSAR. This study comprehensively explores the statistical properties of OTL and their impacts on InSAR measurements, using the Southwest United Kingdom and Northwest France as study areas. Spatially, OTL artifacts on interferograms exhibit an escalating magnitude along the principal direction that aligns with the coastline's orientation. Temporally, the aliasing effect originating from OTL introduces periodic signals with prominent 15/64-day cycles into the Sentinel-1 InSAR time series, causing high velocity biases (up to ∼1 cm/yr) and uncertainties (up to ∼5 mm/yr) for short time spans. Applying OTL correction mitigates the noise level in the displacement time series, leading to a 16% improvement in accuracy, as validated against the Global Navigation Satellite System (GNSS). The study proposes the “overlapping effect” concept, which links InSAR tropospheric delay errors and OTL effects. It underscores the importance of accurate error assessment and removal. Neglecting this interaction may result in a 13% underestimation of the tropospheric error correction efficacy.

Coupling effect of freezing-thawing cycles and dynamic loading on the accumulative deformation and microstructure of foam concrete

Coupling effect of freezing-thawing cycles and dynamic loading on the accumulative deformation and microstructure of foam concrete

Wind influence numerical simulations on stadium structures in RWIND module of the DLUBAL RFEM software

This paper examines the effect of wind load on the stadium building, designed as a possible replacement for the stadium in the city of Mariupol, which was destroyed as a result of hostilities. The problems of using domestic standards in the design of stadium structures are considered. The approach of European regulatory documents to taking into account the effect of wind influence is considered. An analysis of previous scientific studies concerning the determination of aerodynamic parameters for stadium structures has been carried out. An analysis of the domestic regulatory document regulating the collection of wind loads showed the need for additional research into the aerodynamic parameters for stadium structures. Using a special RWIND module as part of the Dlubal RFEM software package, numerical modeling was used to simulate the wind flow flowing around the model of the stadium building, which best corresponded to the adopted design decisions, as if it were carried out in a real wind tunnel. A project was considered for an ellipsoidal stadium, the configuration of the stands and the covering of which is a full bowl with an incomplete covering. The covering over the stadium stands is designed in the form of a canopy formed by cantilever flat steel trusses. The basis of the stadium building frame is made up of vertical steel frames with a rigid connection of nodes, to the central post of which cantilever trusses of the canopy are attached. The result of theoretical testing of the stadium model was distribution diagrams of aerodynamic coefficients, the maximum values of which were used to further determine the values of wind pressure on these structures. An analysis of the research results was was carried out. The use of numerical simulation tools for wind flows made it possible to increase the complexity of the system both at the level of the design solution and at the level of the calculation model. Analysis of the design solution allowed us to competently select the necessary design solutions for load-bearing structures, taking into account the requirements of current design standards and Eurocode 1 regulations.

Sorption enhanced DME synthesis by one-step CO2 hydrogenation

DME synthesis by direct CO2 hydrogenation was studied on physical mixture of commercial CuZnO/Al2O3 (CZA) and in-house synthesized PTA (phosphotungstic acid)/γ-Al2O3 catalysts. Effects of PTA loading (0–50 % by mass) and relative amounts of the catalysts on CO2 conversion and DME yield were investigated. The process was intensified through integration of in-situ steam separation by Zeolite 3A (Z3A) adsorbent mixed with the catalysts. Experiments were run at 498 K, 30 bar, H2:CO2=3:1 and GHSV=1750 h−1 (based on CZA catalyst). Optimum PTA loading and CZA:PTA/γ-Al2O3 mass ratio were 30 % and 1:2, respectively, that gave ∼21 % CO2 conversion and 6.3 % DME yield. These values remained below the respective thermodynamic limits (28.5 % and 21 %), which were exceeded upon adsorbent integration. Catalytic performance depended strongly on adsorbent quantity studied at the catalyst (CZA+PTA/γ-Al2O3):adsorbent mass ratio range of 1:0.33–4. Catalysts and the adsorbent remained stable during the pressure swing driven adsorption-regeneration cycles. Sorption assistance at catalyst:adsorbent ratio=1:4 increased catalyst productivity from 5.5×10−3 to 2×10−2 kgDME h−1 kgcat−1. The latter value was comparable to those of the sorption enhanced CO2+CO hydrogenation systems due to the PTA-based dehydration catalyst with strong acidic features and was promising when the strong thermodynamic limitations of CO2-DME conversion was considered.

A Review of Stability of Dam Structures in Coal Mine Underground Reservoirs

Coal has remained the primary component of China’s energy structure, and high-intensity extraction has continued in the central and western coal-producing regions of China. In contrast to the abundant coal resources, water resources have become extremely scarce in these regions, creating a conflict between coal resource extraction and water resource conservation. The coal mine underground reservoir (CMUR), as a typical technology for combined coal and water extraction and water-preserving coal mining, has been applied in numerous mines in central and western China. This effectively alleviates water resource shortages and achieves the goal of water resource conservation. The CMURs utilizes the goaf created by longwall mining as the water storage space. The reservoir dam structure comprises coal pillars, which serve as protective coal pillars in the mining area, and artificial dam structures that filled the gaps between these coal pillars. The stability of the dam structure under the complex stress effects of hydraulic coupling has been identified as the key to maintaining the safe operation of the CMUR. The mechanical properties, stress field, fracture field, and seepage field (“three fields”) change mechanisms, as well as the research results on size optimization of coal pillar dams and artificial dams in CMURs, were systematically reviewed. The core content included the instability and failure mechanisms of dam structures under the comprehensive coupling effects of factors such as dry–wet cycles of mine water, long-term immersion, chemical effects of high-salinity water, dynamic and static loads, and cyclic loads. This paper is considered to have certain reference value for the study of the stability of dam structures in CMURs and to provide some guidance for the safe operation of CMURs.

Polyurethane-Asphaltic Concrete as an Alternative Solution for Road Pavement Distress – A Review

Road traffic accidents are the primary source of injuries and fatalities worldwide, accounting for 20–50 million long term disabilities and 1.25 million deaths annually. Pavement conditions rank as the second most common cause of traffic accidents. The combined effects of environmental factors and traffic loads lead to pavement discomfort. Ensuring proper pavement design and maintenance can assist in lowering accident rates and preventing long-term disability associated with drivers. Physical maintenance procedures like overlays, seal coatings, patching, and filling joints are carried out in practice; nevertheless, they only offer temporary fixes by treating the symptoms rather than the underlying issue. An alternative method for road pavement maintenance is using polyurethane to improve the properties of asphalt due to the excellent properties of polyurethane. This study conducts a systematic review of the polyurethane asphaltic characteristics and performance based on the previous study by researchers. It is found that the pavement maintenance work using polyurethane is able to sustain longer periods and is moisture resistant due to its excellent bonding with the existing pavement material. Keywords: polyurethane, asphalt, pavement, distress, road

Production of bio-crude from co-pyrolysis of oil shale and peanut shell over semi-coke supported Ni catalyst

Bio-crude producted from the co-pyrolysis of oil shale and peanut shell over a Ni-based catalyst supported on semi-coke was investigated in a vertical double-temperature zone fixed bed reactor. The effect of Ni species loading on the characteristics of bio-crude was evaluated. Results indicated that the effective H/C and calorific value of bio-crude gradually increased and the average carbon chain length gradually decreased with the increase of Ni species loading. The average carbon chain length decreased from 17.54 to 12.61 when the Ni loading was 9 %. An analysis of liquid product components indicated that the presence of the catalyst promoted the combination of small molecular side chains generated by oil shale fractures and active molecules generated by peanut shell thermal decomposition, increasing the generation of phenolic compounds. Furthermore, the phenolic compounds were further converted to aromatic hydrocarbons by promoting the alkylation transfer of the methoxy group to the benzene ring, demethoxylation, and dehydration reactions.

α-Al2O3-loaded promoted the N-desorption reaction and inhibited NH3 decomposition in chemical looping ammonia generation: Experiments and DFT simulations

Chemical looping ammonia generation is a promising, efficient, and environmentally friendly synthesis of ammonia by cycling N-absorption and N-desorption reactions. A portion of the generated NH3 decomposes at the reaction temperature of the N-desorption reaction. In order to promote the N-desorption reaction and inhibit the decomposition of NH3, the effect of α-Al2O3 loading on the N-desorption reaction was investigated in this paper by fixed-bed experiments. The mechanism was revealed using Density functional theory (DFT) calculations. The results showed that when the reaction temperature increased, the conversion of AlN and the yield of NH3 increased, but the actual NH3 conversion decreased. When the steam concentration increased, the conversion of AlN, the yield of NH3, and the actual NH3 conversion increased. The loading of α-Al2O3 could facilitate the N-desorption reaction and inhibit the decomposition of NH3. The 40 wt% α-Al2O3 had the highest conversion of AlN. The 80 wt% α-Al2O3 had the highest yield of NH3. The actual efficiency of ammonia production at 1075 °C with 80 wt% load increased from 45.5% without load to 58.5%. The DFT calculations revealed the mechanism: α-Al2O3 surface promotes the dissociation of H2O molecules to make more hydroxyl groups in the reaction system, which promotes the transfer of H+ and the N-desorption reaction. Meanwhile, the adsorption of NH3 by the α-Al2O3 surface protected NH3 and inhibited its decomposition.

Enhanced mineralization of bisphenol A by electric arc furnace slag: Fenton-like oxidation

Bisphenol A (BPA) aqueous solution was treated through a heterogeneous Fenton-like oxidation process with electric arc furnace slag (EAFS), a waste product from an Argentinian steel processing plant, as the catalyst. SEM/EDS, XRD, and Mössbauer spectroscopy characterization revealed a significant presence of Fe and minor amounts of Cu and Mn in EAFS, known to play active roles in the Fenton-like reactions. The predominant crystalline form of iron in EAFS was magnesiowüstite, accompanied by minor amounts of hematite, magnetite, maghemite, and metallic iron. Batch Fenton-like oxidation experiments were conducted under acidic conditions (pH 2.8–3), examining the effect of temperature (25, 50, and 70 °C) and catalyst load (0.1, 0.5, and 1 g/L) on BPA degradation and mineralization over 180 min. BPA was completely degraded within the first minutes, while mineralization levels improved from 40% to an outstanding 70% as the temperature increased from 25 to 70 °C. The catalyst gradually lost its activity after five cycles at 25 °C, but raising the temperature up to 70 °C allowed maintaining mineralization levels between 70 and 50% over ten cycles. The oxidation process involved a combined Fenton-like homogeneous/heterogeneous mechanism, and deactivation was linked to a lower leaching of active cations over the cycles, reduction of the Fe(II)/Fe(III) ratio in the iron phases, and blocking of active sites by adsorption of reaction intermediates. EAFS demonstrated an exceptional performance in the Fenton-like oxidation of BPA. The utilization of this type of industrial waste materials represents a promising technological alternative that could benefit both steel processing and water treatment plants.

A cross sectional pilot study utilising STrain Analysis and Mapping of the Plantar Surface (STAMPS) to measure plantar load characteristics within a healthy population

BackgroundNo in-shoe systems, measuring both components of plantar load (plantar pressure and shear stress) are available for use in patients with diabetes. The STAMPS (STrain Analysis and Mapping of the Plantar Surface) system utilises digital image correlation (DIC) to determine the strain sustained by a deformable insole, providing a more complete understanding of plantar shear load at the foot-surface interface. Research questionsWhat is the normal range and pattern of strain at the foot-surface interface within a healthy population as measured by the STAMPS system? Is STAMPS a valid tool to measure the effects of plantar load? MethodsA cross-sectional study of healthy participants was undertaken. Healthy adults without foot pathology or diabetes were included. Participants walked 20 steps with the STAMPS insole in a standardised shoe. Participants also walked 10 m with the Novel Pedar® plantar pressure measurement insole within the standardised shoe. Both measurements were repeated three times. Outcomes of interest were global and regional values for peak resultant strain (SMAG) and peak plantar pressure (PPP). ResultsIn 18 participants, median peak SMAG and PPP were 35.01 % and 410.6kPa respectively. The regions of the hallux and heel sustained the highest SMAG (29.31 % (IQR 24.56–31.39) and 20.50 % (IQR 15.59–24.12) respectively) and PPP (344.8kPa (IQR 268.3 – 452.5) and 279.3kPa (IQR 231.3–302.1) respectively). SMAG was moderately correlated with PPP (r= 0.65, p < 0.001). Peak SMAG was located at the hallux in 55.6 % of participants, at the 1st metatarsal head (MTH) in 16.7 %, the heel in 16.7 %, toes 3–5 in 11.1 % and the MTH2 in 5.6 %. SignificanceThe results demonstrate the STAMPS system is a valid tool to measure plantar strain. Further studies are required to investigate the effects of elevated strain and the relationship with diabetic foot ulcer formation.

Enhancing hydrogen adsorption through optimized magnesium dispersion on fibrous nano-silica scaffold: Kinetic and thermodynamic studies

Silica material, particularly, fibrous nano-silica (FNS) is one of the potential scaffolds for hydrogen storage, however, low hydrogen adsorption limits its application. To improve its adsorption capacities, the incorporation of active metal, particularly magnesium (Mg), was prepared. FNS with well-developed pore structures and a good surface area were synthesized. Various amounts of Mg (1–5 wt%) were infiltrated into the FNS. To study the effect of metal loading, the adsorbents were characterized by their chemical structure, crystal phase, morphology/elemental composition, and textural properties. Subsequently, hydrogen adsorption studies were conducted where different reaction conditions, including metal loading, catalyst loading, and temperature were studied. Furthermore, kinetic and thermodynamic studies were conducted based on the Langmuir and Van't Hoff models. The results of the characterizations show that the Mg metal was well dispersed into the porous FNS with no significant changes in the original structure. The optimum adsorption of 1.90 wt% was achieved at 1.0 wt% Mg loading, 0.1 g catalyst loading, and 423 K temperature. Kinetic studies demonstrated that the adsorption process fits the pseudo-second-order reaction. The 1%Mg/FNS adsorbents showed good reusability where 5 runs were conducted with <5 % loss in activity. Therefore, this result indicated that infiltration of Mg into the silica is one of the most active approaches in improving the hydrogen adsorption capacities of FNS.

Parameters estimation and sensitivity analysis of lithium-ion battery model uncertainty based on osprey optimization algorithm

To advance the field of lithium-ion battery (LIB) research, this paper unveils an accurate modelling of LIB that primarily relies on the equivalent circuit model, backed by the Osprey Optimization Algorithm (OOA). In the modelling stage, both single and double resistance-capacitance models are evaluated to depict the charge dynamics, incorporating the effects of fading, load, and temperature variations. The OOA approach is utilized to minimize integral squared errors between the actual measured and model-predicted battery voltages under constraints imposed by the model design variables. This approach is applied to a commercial 2.6 Ahr Panasonic LIB, with the performance of the OOA-based model being benchmarked against models developed by means of other optimization algorithms for further validation. Moreover, the robustness of the OOA method is assessed under battery uncertainty conditions or model parameter variation. A sensitivity analysis is performed on the battery model by employing a proposed approach that evaluates the impact of varying each parameter of the battery model by ±5 %, in a sequence that ascends and descends from 0 to 5 %. The single resistance-capacitance model is selected for in-depth validations. Notably, the OOA approach excels in estimating parameters for LIB modeling under both normal and abnormal operating conditions.

A simplified method for estimating bridge frequency effects considering train mass

The dynamic response of a railway bridge depends on several parameters; the primary parameter is the fundamental natural frequency of vibration of the bridge itself. It is considered a critical parameter of the bridge as the driving or the forcing frequencies arising from moving trains may coincide with the fundamental frequency of the bridge and initiate a resonant response amplifying the bridge load effects. This condition may adversely affect the stresses experienced on bridge members and, consequently, the remaining fatigue life of the structure. Because the train adds additional time-varying mass to the bridge, this introduces a time-varying change in the bridge’s fundamental natural frequency of vibration. As a result, train critical speeds will have a certain range depending on the train configuration. This article presents a simplified method using a power-law relationship to predict the frequency characteristics of a bridge as a function of the train-to-bridge mass ratio. The method is presented in a generalized form, which enables the frequency characteristics to be determined for any given combination of trains and simply supported bridges of short to medium span typically found on the UK rail network. The method is then demonstrated in a case study of a single-span, simply supported plate girder bridge. By considering the BS-5400 train traffic types, the proposed method is used to calculate bridge frequency effects, dynamic amplification, and train critical speed bandwidth for each train type. The simplicity of the proposed method, as it does not require any complex computational modeling, makes it an ideal and effective tool for the practicing engineer to carry out a quick and economical assessment of a bridge for any given train configuration.

Effects of multiple overloads and high-low sequence loading on the fatigue crack propagation of AZ31B magnesium alloy

An experimental study was conducted to examine the initiation of cracks in the AZ31B magnesium (Mg) alloy for tensile overload effects, exploring the influence of overload cycle number, magnitude, and multiplicity of the applied overloads (OL). The number of cycles to failure increased from 8 % to 15 % for overload ratio (OLR) of 1.5 and 2.0 respectively applied as first cycle when compared with constant amplitude loading (CAL). However, the number of cycles to failure increased from 25 % to 43 % for OLR of 1.5 and 2.0 respectively when overload was applied at 5000th cycle. The onset of cracks was delayed when two overloads were applied as the first and 5000th loading cycles. The longitudinal-transverse (L-T) specimens were tested using a two-step high-low sequence loading procedure by varying maximum and minimum load. The fractography results also depict variations in the initial crack formations under different overload conditions. The effects of different overloads on the fracture surfaces of Compact Tension specimens were examined using the Field Emission Scanning Electron Microscopy, indicating substantial reduction in both the number and size of microcracks. 3D profilometer tests were performed, indicating a surface roughness of 0.20 μm to 0.30 μm.

Effects of different loading on the bifurcation of annular elastic rods: Theory vs. experiments

The bifurcation problem of a circular Euler–Bernoulli rod subject to a uniform radial force distribution is investigated under three distinct loading conditions: (i.) hydrostatic pressure, (ii.) centrally-directed, and (iii.) dead load. Previous studies on this apparently ‘familiar’ structural problem have yielded controversial results, necessitating a comprehensive clarification. This study shows that results previously labelled as ‘correct’ or ‘wrong’ simply refer to different external constraints, whose presence becomes necessary only for the two latter loads, (ii.) and (iii.). Moreover, the paper presents the first experimental realization of a circular rod subjected to centrally-directed loads. The experimental findings align with the theoretical predictions and show the exploitation of a new type of load acting on a continuous structural element. The feasibility of this load is demonstrated through the use of inextensible cables and opens the way to applications in flexible robotics when cables are used for actuation.

Social small group optimization algorithm for large-scale economic dispatch problem with valve-point effects and multi-fuel sources

Economic dispatch is an important issue in the management of power systems and is the current focus of specialists. In this paper, a new metaheuristic optimization algorithm is proposed, named Social Small Group Optimization (SSGO), inspired by the psychosocial processes that occur between members of small groups to solve real-life problems. The starting point of the SSGO algorithm is a philosophical conception similar to that of the social group optimization (SGO) algorithm. The novelty lies in the introduction of the small group concept and the modeling of individuals’ evolution based on the social influence between two or more members of the small group. This conceptual framework has been mathematically mapped through a set of heuristics that are used to update the solutions, and the best solutions are retained by employing a greedy selection strategy. SSGO has been applied to solve the economic dispatch problem by considering some practical aspects, such as valve-point loading effects, sources with multiple fuel options, prohibited operating zones, and transmission line losses. The efficiency of the SSGO algorithm was tested on several mathematical functions (unimodal, multimodal, expanded, and composition functions) and on power systems of varying sizes (ranging from 10-units to 1280-units). The SSGO algorithm was compared with SGO and other algorithms belonging to various categories (such as: evolution-based, swarm-based, human behavior-based, hybrid algorithms, etc.), and the results indicated that SSGO outperforms other algorithms applied to solve the economic dispatch problem in terms of quality and stability of the solutions, as well as computation time.

Durability of glass FRP bar‐reinforced seawater–sea sand concrete beams under sustained loading in a subtropical coastal environment

AbstractThe replacement of conventional bars with fiber‐reinforced polymer (FRP) bars in seawater–sea sand concrete (SSC) structures is a promising method for sustainable construction. To promote the engineering application of the aforementioned structures, the primary objective of this study was to investigate the concerns regarding the durability of SSC beams reinforced with GFRP bars. For this purpose, three‐point bending tests were conducted on GFRP bar‐reinforced SSC beams to examine the coupled effects of sustained loading and exposure to a subtropical coastal environment on the flexural behavior of exposed SSC beams. The test results revealed that SSC beams reinforced with GFRP bars exhibited excellent durability in a subtropical coastal environment. The coupled effect of sustained loading and exposure to the subtropical coastal environment had an insignificant negative influence on the ultimate flexural capacity of GFRP bar‐reinforced SSC beams at 540 days of age. The failure mechanism of the exposed GFRP bar‐reinforced SSC beams was concrete crushing due to overreinforcement. Finally, the flexural capacity of the exposed beams was predicted by a function of the degradation in the tensile strength of the GFRP bars.Highlights The coupled effects of loading and environmental exposure on GFRP‐SSC beams were examined. The failure mechanisms of the exposed GFRP‐SSC beams was investigated. The long‐term flexural capacity of the GFRP‐SSC beams was predicted.

An Analysis of the Effect of Functional Load on ESL Learners' Perception of Vowel Contrasts

Functional load (FL), which ranks segmental contrasts based on their communicative value in pronunciation, is essential to the development of pronunciation instruction in that it indicates the priority of certain segmental contrasts that may seriously affect the intelligibility and comprehensibility of spoken language for English as a Second Language (ESL) learners. Despite the widespread use of FL in pronunciation pedagogy for ESL learners, there is little evidence on whether FL affects ESL learners perception of vowel contrasts. In this paper, 20 ESL learners from two Chinese universities are selected to participate in two tasks to observe their performance in discriminating vowel contrasts with different FLs in listening and word pronunciation. The effects of functional load on ESL learners perception of vowel contrasts are investigated in terms of both input and output dimensions. The overall findings indicate that high FL vowel contrasts are more likely to be captured in listening and more consciously distinguished in pronunciation, a piece of evidence proving the necessity of applying FL principle to English pronunciation teaching.

An impact-damping model of collision body with multi-point contact and external load, and its application in gear transmission

The damping term is an important component of the calculation model of the contact force of collision bodies because it simulates the energy dissipation of collision bodies during the contact-impact process. Therefore, an impact-damping model of a collision body with multi-point contact and external load is established by considering the restitution coefficient. The algorithm for solving this model is proposed based on iterative methods. Then, the accuracy of the established model is verified by the consistency between the calculated and tested results. The effect of multi-point contact and external load on the contact-impact process of the collision body is studied. The results show that the hysteresis damping factor increases from small to large when the collision body enters a stable state through repeated impacts. Further, the established damping model is applied to the dynamics model of a spur gear pair with backlash, extended teeth contact, and structure coupling effect of the gear body. The nonlinear dynamic characteristics, multi-state mesh, and teeth impact of the system are studied through the root-mean-square of transmission error, bifurcation diagrams with multi-mapping sections, and contact forces. The calculation results of the gear dynamics model with the impact-damping model are more consistent with the tested results than the calculation results of the gear dynamics model with the traditional damping model. Meanwhile, the connection between system resonance, response coexistence, teeth disengagement, and teeth impact is revealed.