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Modeling and characterization of contact behavior of asperities with irregular shapes 认领 引用
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作者 Jiaxin Huang Chen Sun Jubing Chen 《Theoretical & Applied Mechanics Letters》 EI CAS CSCD 2025年第1期32-42,共11页
This paper introduces a model for characterizing the contact behavior of irregular asperities,transforming it into a superposition of sinusoidal asperity contact behaviors.A new sinusoidal asperity model is developed ... This paper introduces a model for characterizing the contact behavior of irregular asperities,transforming it into a superposition of sinusoidal asperity contact behaviors.A new sinusoidal asperity model is developed for bilin-ear hardening under plane strain conditions.Empirical equations are proposed,considering geometric shapes,tangent modulus,and Young’s modulus.The frequency of asperity height is extracted through Fourier transform for irregular asperities.Contact area and pressure are predicted using the sinusoidal asperity model,and the behavior of irregular asperities is obtained by superimposing those with the first three frequencies.Experimen-tal validation is conducted with milling and knurling-formed asperities,showing good alignment between the model and experimental results.In rough surface models,the proposed irregular asperity model exhibits greater accuracy in predicting contact behavior than a single sinusoidal asperity when interference exceeds 10%of the amplitude. 展开更多
关键词 Experimental characterization Finite element method Plastic deformation Asperity contact
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Numerical parametric study on the influence of location and inclination of large-scale asperities on the shear strength of concreterock interfaces of small buttress dams 认领 引用 被引量：1
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作者 Dipen Bista Adrian Ulfberg +3 位作者 Leif Lia Jaime Gonzalez-Libreros Fredrik Johansson Gabriel Sas 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第10期4319-4329,共11页
When assessing the sliding stability of a concrete dam,the influence of large-scale asperities in the sliding plane is often ignored due to limitations of the analytical rigid body assessment methods provided by curre... When assessing the sliding stability of a concrete dam,the influence of large-scale asperities in the sliding plane is often ignored due to limitations of the analytical rigid body assessment methods provided by current dam assessment guidelines.However,these asperities can potentially improve the load capacity of a concrete dam in terms of sliding stability.Although their influence in a sliding plane has been thoroughly studied for direct shear,their influence under eccentric loading,as in the case of dams,is unknown.This paper presents the results of a parametric study that used finite element analysis(FEA)to investigate the influence of large-scale asperities on the load capacity of small buttress dams.By varying the inclination and location of an asperity located in the concrete-rock interface along with the strength of the rock foundation material,transitions between different failure modes and correlations between the load capacity and the varied parameters were observed.The results indicated that the inclination of the asperity had a significant impact on the failure mode.When the inclinationwas 30and greater,interlocking occurred between the dam and foundation and the governing failure modes were either rupture of the dam body or asperity.When the asperity inclination was significant enough to provide interlocking,the load capacity of the dam was impacted by the strength of the rock in the foundation through influencing the load capacity of the asperity.The location of the asperity along the concrete-rock interface did not affect the failure mode,except for when the asperity was located at the toe of the dam,but had an influence on the load capacity when the failure occurred by rupture of the buttress or by sliding.By accounting for a single large-scale asperity in the concrete-rock interface of the analysed dam,a horizontal load capacity increase of 30%e160%was obtained,depending on the inclination and location of the asperity and the strength of the foundation material. 展开更多
关键词 Concrete dam Buttress dam Sliding Shear strength Concrete-rock interface Asperity inclination Asperity location
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Instantaneous stress release in fault surface asperities during mining-induced fault-slip 认领 引用 被引量：4
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作者 Atsushi Sainoki Hani S.Mitri 《Journal of Rock Mechanics and Geotechnical Engineering》 CSCD 2016年第5期619-628,共10页
Fault-slip taking place in underground mines occasionally causes severe damage to mine openings as a result of strong ground motion induced by seismic waves arising from fault-slip. It is indicated from previous studi... Fault-slip taking place in underground mines occasionally causes severe damage to mine openings as a result of strong ground motion induced by seismic waves arising from fault-slip. It is indicated from previous studies that intense seismic waves could be generated with the shock unloading of fault surface asperities during fault-slip. This study investigates the shock unloading with numerical simulation. A three-dimensional （3D） numerical model with idealized asperities is constructed with the help of discrete element code 3DEC. The idealization is conducted to particularly focus on simulating the shock unloading that previous numerical models, which replicate asperity degradation and crack development during the shear behavior of a joint surface in previous studies, fail to capture and simulate. With the numerical model, static and dynamic analyses are carried out to simulate unloading of asperities in the course of fault-slip. The results obtained from the dynamic analysis show that gradual stress release takes place around the center of the asperity tip at a rate of 45 MPa/ms for the base case, while an instantaneous stress release greater than 80 MPa occurs near the periphery of the asperity tip when the contact between the upper and lower asperities is lost. The instantaneous stress release becomes more intense in the vicinity of the asperity tip, causing tensile stress more than 20 MPa. It is deduced that the tensile stress could further increase if the numerical model is discretized more densely and analysis is carried out under stress conditions at a great depth. A model parametric study shows that in-situ stress state has a significant influence on the magnitude of the generated tensile stress. The results imply that the rapid stress release generating extremely high tensile stress on the asperity tip can cause intense seismic waves when it occurs at a great depth. 展开更多
关键词 Shock unloading Mining-induced fault-slip Asperity Dynamic analysis
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Study on the characteristics of rock failure strain and acoustic emission field for two parallelling faults with the same slip direction including asperities 认领 引用
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作者 焦明若 张国民 +1 位作者 马胜利 马宏生 《Acta Seismologica Sinica(English Edition)》 2002年第4期374-382,共9页
By dealing with strain and acoustic emission (AE) data for two parallelling faultss instability and failure with the same slip direction including asperities, the temporal-spatial evolution of strain and AE field dist... By dealing with strain and acoustic emission (AE) data for two parallelling faultss instability and failure with the same slip direction including asperities, the temporal-spatial evolution of strain and AE field distribution on the asperity of parallelling faults is analyzed. Furthermore the failure process of asperities and interaction among the asperities, i.e., positive and negative seismicity are discussed. Results show that instability and failure for the parallelling faults is a kind of negative seismicity. 展开更多
关键词 experiment asperity instability negative seismicity numerical simulation
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A Novel Algorithm for the Sound Field of Rectangular-Shaped Transducers 认领 引用
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作者 丁德胜 沈长圣 吕华 《Chinese Physics Letters》 SCIE EI CAS CSCD 2015年第12期83-87,共5页
An alternative extension to the Gaussian-beam expansion technique is provided to simplify the computation of the ~esnel field integral for rectangular symmetric sources. From a known result that the circle or rectangl... An alternative extension to the Gaussian-beam expansion technique is provided to simplify the computation of the ~esnel field integral for rectangular symmetric sources. From a known result that the circle or rectangle function is approximately decomposed into a sum of Gaussian functions, the cosine function is similarly expanded by the Bessel Fourier transform. Two expansions are together inserted in this field integral, it is then expressible in terms of the simple algebraic functions. As examples, the numerical results for the sound pressure field are presented for the uniform rectangular piston transducer, in a good agreement with those directly evaluated from the Fresnel integral. A wide applicability of this approach is discussed in treatment of the ultrasonic field radiation problem for a large and important group of piston sources in acoustics. 展开更多
关键词 exp A Novel Algorithm for the Sound Field of Rectangular-Shaped Transducers
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基于荧光原位杂交技术的川续断(Dipsacus asper)45S和5S rDNA的染色体定位分析 认领 引用 被引量：1
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作者 李鹏飞 杨教童 +2 位作者 杨惠尹 肖承鸿 周涛 《分子植物育种》 CAS 北大核心 2025年第19期6581-6585,共5页
本研究以45S和5S rDNA重复序列为探针,利用双色荧光原位杂交技术对川续断有丝分裂中期染色体上的rDNA位点进行物理定位,研究川续断的FISH核型特征。结果表明:(1)川续断核型公式为:2n=2x=18=12m(2SAT)+4sm+2st(2SAT),1号和2号染色体具有... 本研究以45S和5S rDNA重复序列为探针,利用双色荧光原位杂交技术对川续断有丝分裂中期染色体上的rDNA位点进行物理定位,研究川续断的FISH核型特征。结果表明:(1)川续断核型公式为:2n=2x=18=12m(2SAT)+4sm+2st(2SAT),1号和2号染色体具有随体,染色体相对长度范围为8.67%~14.56%,核型属于2A型。(2)川续断具有2对45S rDNA位点、2对5S r DNA位点,45S rDNA位点分别位于1号染色体长臂随体和2号染色体长臂随体处,5S rDNA位点分别位于6号染色体短臂中部和8号染色体短臂端部。本研究对川续断染色体rDNA位点的定位,将为该物种的遗传多样性分析和基因组结构解析提供新的信息。 展开更多
关键词 川续断 荧光原位杂交 rDNA 核型
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Scratching by pad asperities in copper electrochemical-mechanical polishing 认领 引用
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作者 边燕飞 翟文杰 +1 位作者 程媛媛 朱宝全 《Journal of Central South University》 SCIE EI CAS 2014年第11期4157-4162,共6页
Low dielectric constant materials/Cu interconnects integration technology provides the direction as well as the challenges in the fabrication of integrated circuits(IC) wafers during copper electrochemical-mechanical ... Low dielectric constant materials/Cu interconnects integration technology provides the direction as well as the challenges in the fabrication of integrated circuits(IC) wafers during copper electrochemical-mechanical polishing(ECMP). These challenges arise primarily from the mechanical fragility of such dielectrics, in which the undesirable scratches are prone to produce. To mitigate this problem, a new model is proposed to predict the initiation of scratching based on the mechanical properties of passive layer and copper substrate. In order to deduce the ratio of the passive layer yield strength to the substrate yield strength and the layer thickness, the limit analysis solution of surface scratch under Berkovich indenter is used to analyze the nano-scratch experimental measurements. The modulus of the passive layer can be calculated by the nano-indentation test combined with the FEM simulation. It is found that the film modulus is about 30% of the substrate modulus. Various regimes of scratching are delineated by FEM modeling and the results are verified by experimental data. 展开更多
关键词 electrochemical-mechanical polishing scratch pad asperities nano-scratch model nano-indentation
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Landslide monitoring and mechanism analysis based on asperity theory:a case study of Rongwu Expressway,Inner Mongolia 认领 引用
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作者 XING Yuanhao LI Chi +3 位作者 ZHANG Baolong CAO Wenhai LI Shuanhu GAO Yu 《Journal of Mountain Science》 SCIE CSCD 2025年第9期3433-3448,共16页
Varied slope structures have different landslide initiation mechanisms.However,the role of interfacial asperities in controlling sliding initiation is unclear.This study develops a novel analytical method for interfac... Varied slope structures have different landslide initiation mechanisms.However,the role of interfacial asperities in controlling sliding initiation is unclear.This study develops a novel analytical method for interface mechanisms in practical landslide scenarios.Based on asperity theory,theoretical derivations were conducted,yielding an equilibrium equation grounded in the maximum shear length of asperities(Llimit).A method was proposed to evaluate slope stability by integrating Llimit with monitored displacement data.On-site displacement monitoring and slope state analysis determined the distribution range of asperities,providing theoretical support for slope remediation.Between July 2023 and July 2024,a large landslide located in Shagudu Town,Zhungeer Banner,Ordos,Inner Mongolia,underwent multiple deformation stages.This landslide seriously affected the operations of the Rongwu Expressway.This study initially examined the geological structure of the landslide through geological drilling and surveys.The distribution of asperities in the landslide area was determined through physical and mechanical tests and on-site geological mapping.A layout plan for landslide disposal and monitoring points was developed based on the interface landslide asperity theory.Analysis of 20 days of displacement monitoring data was used to determine asperity distribution and analyze slope movement,informed by asperity theory.This study pioneers the systematic application of asperity theory as the primary framework for analyzing and managing a large-scale interface landslide in engineering practice.Its rationality and effectiveness are rigorously demonstrated through the successful determination of the asperity distribution range within the Rongwu Expressway landslide,leading to effective remediation and favorable monitoring outcomes.This work not only validates the asperity theory for interface landslides but,crucially,establishes a novel,practical method for their stability assessment.Furthermore,a key theoretical advancement is the development of the concept that asperity-controlled main sliding surfaces can induce secondary sliding surfaces,based on field evidence and analysis. 展开更多
关键词 Interfacial landslide Asperity theory Monitoring method Theoretical innovation
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NORMAL CONTACT STIFFNESS OF THE ELLIPTIC AREA BETWEEN TWO ASPERITIES 认领 引用 被引量：2
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作者 Zhiqiang Liu Junping Shi +1 位作者 Fusheng Wang Zhufeng Yue 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2015年第1期33-39,共7页
A new expression for contact deformation is given, and the normal contact stiff- ness between single asperities is derived according to Hooke＇s law. A contact model between two ellipsoidal asperities is simulated by ... A new expression for contact deformation is given, and the normal contact stiff- ness between single asperities is derived according to Hooke＇s law. A contact model between two ellipsoidal asperities is simulated by the FE method, the result compared with the theoretical solution. It is found that the curves of the normal contact stiffness versus the included angle in the principal curvature direction show similar trends and evolve as a cosine feature. The effects of the parameters on normal contact stiffness are found to show that normal contact stiffness increases and reaches the upper limit gradually with an increase in these parameters. 展开更多
关键词 contact stiffness joint surface elliptical area asperity
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Study of hydro-mechanical behaviours of rough rock fracture with shear dilatancy and asperities using shear-flow model 认领 引用 被引量：2
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作者 Luyu Wang Weizhong Chen Qun Sui 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第10期4004-4016,共13页
The geometric properties of fracture surfaces significantly influence shear-seepage in rock fractures,introducing complexities to fracture modelling.The present study focuses on the hydro-mechanical behaviours of roug... The geometric properties of fracture surfaces significantly influence shear-seepage in rock fractures,introducing complexities to fracture modelling.The present study focuses on the hydro-mechanical behaviours of rough rock fractures during shear-seepage processes to reveal how dilatancy and fracture asperities affect these phenomena.To achieve this,an improved shear-flow model(SFM)is proposed with the incorporation of dilatancy effect and asperities.In particular,shear dilatancy is accounted for in both the elastic and plastic stages,in contrast to some existing models that only consider it in the elastic stage.Depending on the computation approaches for the peak dilatancy angle,three different versions of the SFM are derived based on Mohr-Coulomb,joint roughness coefficient-joint compressive strength(JRC-JCS),and Grasselli’s theories.Notably,this is a new attempt that utilizes Grasselli’s model in shearseepage analysis.An advanced parameter optimization method is introduced to accurately determine model parameters,addressing the issue of local optima inherent in some conventional methods.Then,model performance is evaluated against existing experimental results.The findings demonstrate that the SFM effectively reproduces the shear-seepage characteristics of rock fracture across a wide range of stress levels.Further sensitivity analysis reveals how dilatancy and asperity affect hydraulic properties.The relation between hydro-mechanical properties(dilatancy displacement and hydraulic conductivity)and asperity parameters is analysed.Several profound understandings of the shear-seepage process are obtained by exploring the phenomenon under various conditions. 展开更多
关键词 Rock fracture Stress-seepage coupling Shear-flow model Fracture asperity Shear dilatancy
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Decadal Seismicity Prior to Great Earthquakes at Subduction Zones: Roles of Major Asperities and Low-Coupling Zones 认领 引用 被引量：5
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作者 Lynn R. Sykes 《International Journal of Geosciences》 CAS 2021年第9期845-926,共82页
Decadal forerunning seismic activity of magnitude Mw ≥ 5.0 is mapped for all 45 mainshocks of Mw 7.7 to 9.1 at subduction zones of the world from 1993 to mid 2020. The zones of high slip in nearly all great earthquak... Decadal forerunning seismic activity of magnitude Mw ≥ 5.0 is mapped for all 45 mainshocks of Mw 7.7 to 9.1 at subduction zones of the world from 1993 to mid 2020. The zones of high slip in nearly all great earthquakes were nearly quiescent beforehand and are identified as the sites of great asperities and zones of strong seismic coupling. Much forerunning activity occurred at smaller asperities along the peripheries of the rupture zones of many great and giant mainshocks. Those sizes of great asperities as ascertained from forerunning activity generally agree with the areas of high seismic slip as determined by others from geodetic and tide-gauge data and finite-source seismic modeling. Asperities are strong, well-coupled portions of plate interfaces. Different patterns of forerunning activity on time scales of about 5 to 45 years are attributed to either the sizes and spacing of asperities (or lack of). This permits many great asperities to be mapped decades before they rupture in great and giant shocks. Several poorly coupled subduction zones such as Java, Lesser Sunda, Marianas, Tonga and Kermadec are characterized by few great thrust earthquakes and little, in any forerunning activity. Rupture zones of many great and giant earthquakes are bordered either along strike, updip, or downdip by zones of lower plate coupling. Several bordering regions were sites of forerunning activity, aftershocks, and slow-slip events. The detection of forerunning and precursory activities of various kinds should be sought on the peripheries of great asperities as well as within zones of high co-seismic slip. 展开更多
关键词 Earthquakes Subduction Prediction Plate Coupling Asperities
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Decadal Seismicity before Great Earthquakes—Strike-Slip Faults and Plate Interiors: Major Asperities and Low-Coupling Zones 认领 引用 被引量：4
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作者 Lynn R. Sykes 《International Journal of Geosciences》 CAS 2021年第9期784-833,共50页
Decadal forerunning seismic activity is examined for very large, shallow earthquakes along strike-slip and intraplate faults of the world. It includes forerunning shocks of magnitude Mw ≥ 5.0 for 21 mainshocks of Mw ... Decadal forerunning seismic activity is examined for very large, shallow earthquakes along strike-slip and intraplate faults of the world. It includes forerunning shocks of magnitude Mw ≥ 5.0 for 21 mainshocks of Mw 7.5 to 8.6 from 1989 to 2020. Much forerunning activity occurred at what are interpreted to be smaller asperities along the peripheries of the rupture zones of great mainshocks at transform faults and subduction zones. Several great asperities as ascertained from forerunning activity agree with the areas of high seismic slip as determined by others using geodetic, mapping of surface faulting, and finite-source seismic modeling. The zones of high slip in many great earthquakes were nearly quiescent beforehand and are identified as the sites of great asperities. Asperities are strong, well-coupled portions of plate interfaces. Different patterns of forerunning activity on time scales of up to 45 years are attributed to the sizes and spacing of asperities (or lack of). This permits at least some great asperities along transform faults to be mapped decades before they rupture in great shocks. Rupture zones of many great mainshocks along transform faults are bordered either along strike, at depth or regionally by zones of lower plate coupling including either fault creep  forerunning activity, aftershocks and/or slow-slip events. Forerunning activity to transforms in continental areas is more widespread spatially than that adjacent to oceanic transforms. The parts of the San Andreas fault themselves that ruptured in great California earthquakes during 1812, 1857 and 1906 have been very quiet since 1920;moderate to large shocks have been concentrated on their peripheries. The intraplate shocks studied, however, exhibited few if any forerunning events, which is attributed to the short period of time studied compared to their repeat times. The detection of forerunning and precursory activities for various time scales should be sought on the peripheries of great asperities and not just along the major faults themselves. This paper compliments that on decadal forerunning activity to great and giant earthquakes along subduction zones. 展开更多
关键词 Earthquakes Strike-Slip Faults Transform Faults Intraplate Prediction Plate Coupling Asperities
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Elastic-plastic nonlinear contact model for rough interfaces based on monotonically continuous contact pressure 认领 引用
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作者 Bo Li Yufan Zhang +4 位作者 Sanmin Wang Yesen Fan U.Xuan Tan Gantes J.Charis Jihong Zhu 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2026年第3期237-247,共11页
The contact pressure of an asperity is the fundamental parameter for constructing a single asperity contact model and analyzing the contact load and contact stiffness of the mechanical joint surfaces.In response to th... The contact pressure of an asperity is the fundamental parameter for constructing a single asperity contact model and analyzing the contact load and contact stiffness of the mechanical joint surfaces.In response to the defects of existing models in contact pressure analysis that have non-monotonic changes or do not conform to physical laws,this paper proposes a novel nonlinear contact model that can achieve continuous monotonic changes in contact pressure in accordance with physical laws.This model considers the continuous deformation of the asperity after load application,and can describe three deformation states:elastic,elastic-plastic,and plastic during the loading process.For the elastic and plastic deformation stages,this paper characterizes them using the classic Hertz elastic contact theory and the complete plastic contact theory.For the elastic-plastic deformation stage,the contact pressure is characterized using an empirical pressure function,and expressions for other contact parameters are derived.Furthermore,based on the principle of probability and statistics,the solution expression for the contact parameters of the rough interface is obtained,and a novel rough interface contact model is established.By comparing with existing experimental and simulation results,it is found that:1)The model in this paper achieves monotonic and continuous changes in contact pressure during the contact process of the asperity,while complying with physical laws;2)The new model is in good agreement with experimental and simulation results,verifying the universal effectiveness and correctness of the proposed model in solving the contact parameters of the rough interface;3)The new model has simplicity in expression and high computa-tional efficiency. 展开更多
关键词 Asperity Mechanical joint surface Elastic-plastic deformation Statistics Numerical calculation
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基于超声合成孔径的孔缺陷成像与重构研究 认领 引用
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作者 武静 林泽宇 +3 位作者 杨颖锋 刘阳 郑明方 张伟伟 《机械强度》 CAS CSCD 北大核心 2026年第7期148-155,共8页
【目的】针对超声波传播衰减导致缺陷回波幅值减小、漏检率升高,以及传统合成孔径成像受硬件成本与数据处理方法制约的问题,提出一种基于超声合成孔径的缺陷成像与三维重构方法,为金属构件内部孔缺陷检测提供参考。【方法】首先,采用单... 【目的】针对超声波传播衰减导致缺陷回波幅值减小、漏检率升高,以及传统合成孔径成像受硬件成本与数据处理方法制约的问题,提出一种基于超声合成孔径的缺陷成像与三维重构方法,为金属构件内部孔缺陷检测提供参考。【方法】首先,采用单个圆形直探头结合合成孔径聚焦技术实现缺陷二维成像,以降低硬件成本与系统复杂度;其次,构造基于信号强度变化的自适应时间增益补偿曲线,对不同深度回波信号进行增益处理,以补偿声波衰减;然后,采用双线性插值提升图像分辨率,结合-6 dB阈值分割与Canny边缘检测算法完成缺陷定量分析;最后,引入动态阈值改进Marching Cubes算法,实现缺陷三维重构。【结果】结果表明,该方法可将孔缺陷直径检测相对误差从40%、74%降至9%、8.5%,轴向分辨率提升24.7%~32.5%,二维成像与三维重构运算效率分别提升16.9%、3.2%,能够快速、高质量完成金属构件内部缺陷检测。 展开更多
关键词 超声成像 合成孔径聚焦技术 时间增益补偿 缺陷三维重构 孔缺陷检测
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不同生境川续断形态特征以及传粉者多样性的地理变异模式 认领 引用
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作者 李杨 吕晓琴 +3 位作者 伍英 陈孝旺 颜国浩 王晓月 《生物多样性》 CAS CSCD 北大核心 2026年第5期13-28,共16页
传粉者介导的花形态变异多集中在特化的传粉系统中,对于广泛分布且泛化传粉的植物,其形态特征以及传粉者类群如何随着地理环境而产生变异,以及二者与经纬度、海拔因子的相关性,目前尚不清楚。我们前期的研究发现川续断科植物川续断(Dips... 传粉者介导的花形态变异多集中在特化的传粉系统中,对于广泛分布且泛化传粉的植物,其形态特征以及传粉者类群如何随着地理环境而产生变异,以及二者与经纬度、海拔因子的相关性,目前尚不清楚。我们前期的研究发现川续断科植物川续断(Dipsacus asper)在我国西南地区广泛分布,具有典型的泛化传粉系统,为探究该问题提供了理想材料。本研究以川续断为研究对象,在湖北、四川、云南和贵州13个野生川续断的集中分布居群开展实验,通过测量植物的形态特征,比较了其在不同居群内和居群间的变异系数;观察每个川续断居群访花昆虫的类型并计算了访花频率,测量了主要传粉熊蜂的虫体特征;统计了川续断不同居群的自然结实率。结果表明,川续断不同居群的形态特征有显著变化,叶片和茎的变异系数较大,而花序大小的变异系数较小,其中小金、建始、盐源和习水居群的花序大于其他居群。川续断主要的传粉者为熊蜂属(Bombus)、蜜蜂属(Apis)、管状蚜蝇属(Eristalis)、蛾蝶类等,其中蜂类是重要的传粉者。川续断不同居群的传粉者类型以及访花频率存在显著差异,小金、建始、盐源和习水居群主要是由虫体较大的熊蜂传粉,川续断的花管长和广泛分布的弗里熊蜂(Bombus friseanus)的吻长没有显著相关性。川续断的植株高度、茎、叶、花序大小和弗里熊蜂的虫体长等特征均随着海拔的升高显著减小;植株高度、弗里熊蜂的吻长随着经度的增加显著增加,茎、叶、花序大小、弗里熊蜂腹部随着经度的增加显著减小;叶、花序大小、弗里熊蜂头和胸的厚度、腹部随着纬度的增加显著增加,弗里熊蜂的吻长随着纬度的增加显著减小。不同地理分布的川续断自然结实率随着经度的增加而增加,随纬度的增加显著减小,随着海拔升高呈现增加的趋势。广布种的形态特征和传粉者的多样性随着地理梯度的变化呈现显著变异,这种变异可能源于植物与传粉者以及生境中经纬度以及海拔因子的共同作用。不同地理环境中的植物通过花形态的变化并借助多样化的传粉者来保障自身的繁殖成功。 展开更多
关键词 地理变异 川续断 形态特征 传粉者 繁育成功
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考虑细观形貌特征的岩石裂隙受压时变闭合规律 认领 引用
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作者 宋振宇 颜炳明 +2 位作者 李博 邹良超 石振明 《地球科学》 EI CAS CSCD 北大核心 2026年第2期496-512,共17页
基于不同高径比微凸体的受压时效性试验,根据赫兹接触理论,得到了不同微凸体弹性模量随时间的衰减规律.对红砂岩和石灰岩新鲜裂隙面开展了不同法向应力条件下的受压时变闭合试验,结合小波分析法、区域生长算法和参考面法,提出了一种岩... 基于不同高径比微凸体的受压时效性试验,根据赫兹接触理论,得到了不同微凸体弹性模量随时间的衰减规律.对红砂岩和石灰岩新鲜裂隙面开展了不同法向应力条件下的受压时变闭合试验,结合小波分析法、区域生长算法和参考面法,提出了一种岩石裂隙细观尺度微凸体形貌的识别方法,对比了试验前后微凸体数量、高度和高径比的差异.建立了考虑微凸体间相互作用的接触力学模型,求解Boussinesq方程并考虑弹性模量随时间的衰减,对两种岩石裂隙开展了逐级增加应力条件下的受压时变闭合计算.通过对比计算和试验得到的损伤面积和蠕变变形验证了模型的有效性,阐明了微凸体的应变、接触面积和接触应力随时间的演化规律,揭示了不同细观形貌特征的微凸体在裂隙受压时变闭合过程中的关键性作用. 展开更多
关键词 岩石裂隙 微凸体 形貌特征 时变闭合 赫兹接触 岩石力学
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高温工况下滚子−轨道表面介观接触特性研究 认领 引用
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作者 高志强 张宇 +2 位作者 张东亚 王雯 傅卫平 《力学学报》 EI CAS CSCD 北大核心 2026年第7期2043-2052,共10页
高端制造装备精密进给系统中,滚子-轨道的接触静动态特性对装备的精度具有重要影响.现有研究多聚焦于微观粗糙表面特征(如粗糙度、形貌、纹理方向等)对接触行为的影响,而温度与力学行为之间的接触机制尚需进一步探索.尤其在外载荷和局... 高端制造装备精密进给系统中,滚子-轨道的接触静动态特性对装备的精度具有重要影响.现有研究多聚焦于微观粗糙表面特征(如粗糙度、形貌、纹理方向等)对接触行为的影响,而温度与力学行为之间的接触机制尚需进一步探索.尤其在外载荷和局部高温共同作用下,常温假设下的接触模型难以准确表征实际工况中的接触性能变化.为此,本文建立了考虑温度效应的滚子-轨道介观粗糙表面统计接触模型,重点分析了温度对微凸体弹塑性临界变形量、塑性指数等基础接触参数的作用机制,并揭示了温度对接触力、接触面积和接触刚度等关键参数的影响规律.本研究同时构建了边界元法(BEM)模型进行验证,结果表明:在高温全变形区间内,模型与仿真结果吻合良好,但在低温大变形工况下仍存在一定偏差.研究结果为热-力效应服役环境下进给系统的精度设计与精度保持性预测提供了重要的理论支撑. 展开更多
关键词 高温 微凸体临界变形 塑性指数 粗糙表面接触性能
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考虑微凸体间相互作用的结合面卸载过程接触特性分形理论建模 认领 引用
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作者 王颜辉 郭强 +2 位作者 孙万 王南山 王崴 《润滑与密封》 CAS CSCD 北大核心 2026年第8期46-52,共7页
弹塑性及塑性变形阶段结合面的接触特性与微凸体间相互作用密切相关。在考虑微凸体间相互作用情况下,基于MB模型对结合面卸载过程的接触特性开展研究。建立第一、第二弹塑性变形阶段中加载后即完全卸载的单个微凸体接触载荷与接触刚度... 弹塑性及塑性变形阶段结合面的接触特性与微凸体间相互作用密切相关。在考虑微凸体间相互作用情况下,基于MB模型对结合面卸载过程的接触特性开展研究。建立第一、第二弹塑性变形阶段中加载后即完全卸载的单个微凸体接触载荷与接触刚度理论模型,建立其在各变形阶段的临界接触面积与临界接触变形理论模型;针对卸载过程的弹性、第一弹塑性及第二弹塑性变形阶段,研究结合面微凸体面积分布修正函数和载荷修正函数;基于分形理论建立卸载过程结合面各变形阶段的接触载荷和接触刚度模型,并完成结合面卸载过程实际接触载荷、接触刚度理论模型的分形建模。结果表明,结合面卸载过程中,微凸体间的相互作用对接触载荷、接触刚度有显著影响;在相同参数条件下,两者均高于忽略微凸体间相互作用时的结果。结合面接触特性与分形维数、尺度系数有直接关系,其变化规律与忽略微凸体间相互作用时的影响趋势一致。接触刚度随分形维数、尺度系数的增大而增大;随着接触面积增大,分形维数、尺度系数对接触刚度—接触面积关系曲线的影响趋于显著。相关成果可为后续开展结合面反复加卸载研究提供理论支撑。 展开更多
关键词 微凸体间相互作用 结合面 卸载过程 接触特性 分形理论
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基于分形理论的多尺度接触热导特性研究 认领 引用 被引量：1
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作者 曹小岗 陈剑 +4 位作者 曹敏 杨海 李国豪 朱鑫龙 李海洋 《轻工机械》 CAS 2026年第1期1-11,共11页
为提高粗糙表面接触热导(Thermal Contact Conductance, TCC)预测模型的精度和适用性,课题组构建了一种基于分形理论和Kogut-Etsion模型的多尺度接触热导预测模型。该模型系统引入弹性、第一弹塑性、第二弹塑性和完全塑性共4阶段接触变... 为提高粗糙表面接触热导(Thermal Contact Conductance, TCC)预测模型的精度和适用性,课题组构建了一种基于分形理论和Kogut-Etsion模型的多尺度接触热导预测模型。该模型系统引入弹性、第一弹塑性、第二弹塑性和完全塑性共4阶段接触变形机制,全面考虑不同微凸体等级(不同频率指数n)在界面传热中的贡献,并且推导出多尺度条件下接触热导的解析表达式。研究结果表明:低阶大尺度微凸体在实际接触面积和热流传递中占主导作用,而高阶小尺度微凸体的影响相对较小;分形参数对TCC具有显著影响,其中分形维数D的增大可提高接触热导,而尺度参数G的增大则会降低热导。实验数据及经典模型对比验证表明:该模型不仅提高了预测精度,也拓展了适用范围,为复杂工程界面热管理的设计与优化提供了参考。 展开更多
关键词 接触热导 分形理论 多尺度 微凸体等级 分形维数
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Hybrid finite-discrete element modelling of asperity degradation and gouge grinding during direct shearing of rough rock joints 认领 引用 被引量：10
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作者 H. Y. Liu Haoyu Han +1 位作者 H. M. An J. J. Shi 《International Journal of Coal Science & Technology》 EI CAS 2016年第3期295-310,共16页
A hybrid finite-discrete element method was implemented to study the fracture process of rough rock joints under direct shearing. The hybrid method reproduced the joint shear resistance evolution process from asperity... A hybrid finite-discrete element method was implemented to study the fracture process of rough rock joints under direct shearing. The hybrid method reproduced the joint shear resistance evolution process from asperity sliding to degradation and from gouge formation to grinding. It is found that, in the direct shear test of rough rock joints under constant normal displacement loading conditions, higher shearing rate promotes the asperity degradation but constraints the volume dilation, which then results in higher peak shear resistance, more gouge formation and grinding, and smoother new joint surfaces. Moreover, it is found that the joint roughness affects the joint shear resistance evolution through influencing the joint fracture micro mechanism. The asperity degradation and gouge grinding are the main failure micro-mechanism in shearing rougher rock joints with deeper asperities while the asperity sliding is the main failure micro-mechanism in shearing smoother rock joints with shallower asperities. It is concluded that the hybrid finite-discrete element method is a valuable numerical tool better than traditional finite element method and discrete element method for modelling the joint sliding, asperity degradation, gouge formation, and gouge grinding occurred in the direct shear tests of rough rock joints. 展开更多
关键词 Hybrid FEM-DEM Rock joint Asperity sliding Asperity shearing Fragment grinding
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