A thermal-solid-liquid complex operational environment induces structural interface developing a typical coupling sliding/impact wear behavior.It results in contact damage until systems fail,which may cause significan...A thermal-solid-liquid complex operational environment induces structural interface developing a typical coupling sliding/impact wear behavior.It results in contact damage until systems fail,which may cause significant economic losses and catastrophic consequences.The key point of solving this problem is to reveal the coupling damage mechanism of the sliding/impact behavior in typical systems and life characterization under a complicate evolving environment.This has been a hot topic in the area of mechanical reliability.The main work in this paper can be concluded as follows.Firstly,the main industries in which the"sliding/impact behavior"takes place have been introduced.Then,existing studies on the wear mechanism and degree analysis are presented,which includes surface morphology analysis,wear debris analysis,and wear degree measurement.Meanwhile,existing problems in theoretical modeling and experiments in current research are summarized,so as to point out a bright direction for future research on wear prediction.They include interface contact modeling,mathematic coupling mechanism modeling,wear equation establishment,and wear life characterization,which can provide some new ideas for improving the existing studies on the sliding/impact wear behavior.展开更多
Composite structures consisting of two-dimensional(2D)materials deposited on elastic substrates have a wide range of potential applications in flexible electronics.For such devices,robust 2D film/substrate interfacial...Composite structures consisting of two-dimensional(2D)materials deposited on elastic substrates have a wide range of potential applications in flexible electronics.For such devices,robust 2D film/substrate interfacial adhesion is essential for their reliable performance when subjected to external thermal and mechanical loads.To better understand the strength and failure behavior of the 2D film/substrate interfaces,two types of graphene/polymer samples with distinct interfacial adhesion properties are fabricated and tested by uniaxially stretching the substrates.Depending on the interfacial adhesion,two drastically different debonding rates are observed,i.e.,rapid snap-through debonding and more progressive crack propagation.Motivated by the experimental observation,we propose an improved shear-lag model with a trapezoidal-shaped cohesive zone to derive an analytical solution for the decohesion behavior.The theoretical model reveals that the decohesion behavior of the frictional adhesive interface is governed by three dimensionless parameters.Particularly,the dimensionless length of the film essentially determines the decohesion rate;while the other two parameters affect the critical substrate strain to initiate debonding.By fitting the experimental data with the theoretical model,the intrinsic adhesion properties of the two samples are obtained with physically meaningful values.This work offers an analytical solution to describing the decohesion behavior of general thin film/substrate systems with a frictional adhesive interface,which is beneficial for characterizing and optimizing the mechanical properties of various thin film/polymer devices.展开更多
Anti-slide piles are one of the most important reinforcement structures against landslides,and evalu-ating the working conditions is of great significance for landslide mitigation.The widely adopted analytical methods...Anti-slide piles are one of the most important reinforcement structures against landslides,and evalu-ating the working conditions is of great significance for landslide mitigation.The widely adopted analytical methods of pile internal forces include cantilever beam method and elastic foundation beam method.However,due to many assumptions involved in calculation,the analytical models cannot be fully applicable to complex site situations,e.g.landslides with multi-sliding surfaces and pile-soil interface separation as discussed herein.In view of this,the combination of distributed fiber optic sensing(DFOS)and strain-internal force conversion methods was proposed to evaluate the working conditions of an anti-sliding pile in a typical retrogressive landslide in the Three Gorges reservoir area,China.Brillouin optical time domain reflectometry(BOTDR)was utilized to monitor the strain distri-bution along the pile.Next,by analyzing the relative deformation between the pile and its adjacent inclinometer,the pile-soil interface separation was profiled.Finally,the internal forces of the anti-slide pile were derived based on the strain-internal force conversion method.According to the ratio of calculated internal forces to the design values,the working conditions of the anti-slide pile could be evaluated.The results demonstrated that the proposed method could reveal the deformation pattern of the anti-slide pile system,and can quantitatively evaluate its working conditions.展开更多
The pre-sliding regime is typically neglected in the dynamic modelling of mechanical systems. However, the change in contact state caused by static friction may decrease positional accuracy and control precision. To i...The pre-sliding regime is typically neglected in the dynamic modelling of mechanical systems. However, the change in contact state caused by static friction may decrease positional accuracy and control precision. To investigate the relationship between contact status and contact force in pre-sliding friction, an optical experimental method is presented in this paper.With this method, the real contact state at the interface of a transparent material can be observed based on the total reflection principle of light by using an image processing technique. A novel setup, which includes a pair of rectangular trapezoidal blocks, is proposed to solve the challenging issue of accurately applying different tangential and normal forces to the contact interface. The improved Otsu＇s method is used for measurement. Through an experimental study performed on polymethyl methacrylate（PMMA）, the quantity of contact asperities is proven to be the dominant factor that affects the real contact area. The relationship between the real contact area and the contact force in the pre-sliding regime is studied, and the distribution of static friction at the contact interface is qualitatively discussed. New phenomena in which the real contact area expands along with increasing static friction are identified. The aforementioned relationship is approximately linear at the contact interface under a constant normal pressure, and the distribution of friction stress decreases from the leading edge to the trailing edge.展开更多
基金supported by the National Natural Science Foundation of China(No.51675025).
文摘A thermal-solid-liquid complex operational environment induces structural interface developing a typical coupling sliding/impact wear behavior.It results in contact damage until systems fail,which may cause significant economic losses and catastrophic consequences.The key point of solving this problem is to reveal the coupling damage mechanism of the sliding/impact behavior in typical systems and life characterization under a complicate evolving environment.This has been a hot topic in the area of mechanical reliability.The main work in this paper can be concluded as follows.Firstly,the main industries in which the"sliding/impact behavior"takes place have been introduced.Then,existing studies on the wear mechanism and degree analysis are presented,which includes surface morphology analysis,wear debris analysis,and wear degree measurement.Meanwhile,existing problems in theoretical modeling and experiments in current research are summarized,so as to point out a bright direction for future research on wear prediction.They include interface contact modeling,mathematic coupling mechanism modeling,wear equation establishment,and wear life characterization,which can provide some new ideas for improving the existing studies on the sliding/impact wear behavior.
基金the National Natural Science Foundation of China(Nos.12025203,11921002,and 11890671)the National Key R&D Program of China(No.2022YFF0706100)the Initiative Program of State Key Laboratory of Tribology in Advanced Equipment(No.SKLT2022A01).
文摘Composite structures consisting of two-dimensional(2D)materials deposited on elastic substrates have a wide range of potential applications in flexible electronics.For such devices,robust 2D film/substrate interfacial adhesion is essential for their reliable performance when subjected to external thermal and mechanical loads.To better understand the strength and failure behavior of the 2D film/substrate interfaces,two types of graphene/polymer samples with distinct interfacial adhesion properties are fabricated and tested by uniaxially stretching the substrates.Depending on the interfacial adhesion,two drastically different debonding rates are observed,i.e.,rapid snap-through debonding and more progressive crack propagation.Motivated by the experimental observation,we propose an improved shear-lag model with a trapezoidal-shaped cohesive zone to derive an analytical solution for the decohesion behavior.The theoretical model reveals that the decohesion behavior of the frictional adhesive interface is governed by three dimensionless parameters.Particularly,the dimensionless length of the film essentially determines the decohesion rate;while the other two parameters affect the critical substrate strain to initiate debonding.By fitting the experimental data with the theoretical model,the intrinsic adhesion properties of the two samples are obtained with physically meaningful values.This work offers an analytical solution to describing the decohesion behavior of general thin film/substrate systems with a frictional adhesive interface,which is beneficial for characterizing and optimizing the mechanical properties of various thin film/polymer devices.
基金The authors gratefully acknowledge the financial support pro-vided by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.41907232)the National Science Fund for Distinguished Young Scholars of China(Grant No.42225702)the State Key Program of National Natural Science Foundation of China(Grant No.41230636).
文摘Anti-slide piles are one of the most important reinforcement structures against landslides,and evalu-ating the working conditions is of great significance for landslide mitigation.The widely adopted analytical methods of pile internal forces include cantilever beam method and elastic foundation beam method.However,due to many assumptions involved in calculation,the analytical models cannot be fully applicable to complex site situations,e.g.landslides with multi-sliding surfaces and pile-soil interface separation as discussed herein.In view of this,the combination of distributed fiber optic sensing(DFOS)and strain-internal force conversion methods was proposed to evaluate the working conditions of an anti-sliding pile in a typical retrogressive landslide in the Three Gorges reservoir area,China.Brillouin optical time domain reflectometry(BOTDR)was utilized to monitor the strain distri-bution along the pile.Next,by analyzing the relative deformation between the pile and its adjacent inclinometer,the pile-soil interface separation was profiled.Finally,the internal forces of the anti-slide pile were derived based on the strain-internal force conversion method.According to the ratio of calculated internal forces to the design values,the working conditions of the anti-slide pile could be evaluated.The results demonstrated that the proposed method could reveal the deformation pattern of the anti-slide pile system,and can quantitatively evaluate its working conditions.
基金Project supported by the National Natural Science Foundation of China(Grant No.11272171)the Natural Science Foundation of Beijing City,China(Contract No.3172017)the Education Ministry Doctoral Fund of China(Grant No.20120002110070)
文摘The pre-sliding regime is typically neglected in the dynamic modelling of mechanical systems. However, the change in contact state caused by static friction may decrease positional accuracy and control precision. To investigate the relationship between contact status and contact force in pre-sliding friction, an optical experimental method is presented in this paper.With this method, the real contact state at the interface of a transparent material can be observed based on the total reflection principle of light by using an image processing technique. A novel setup, which includes a pair of rectangular trapezoidal blocks, is proposed to solve the challenging issue of accurately applying different tangential and normal forces to the contact interface. The improved Otsu＇s method is used for measurement. Through an experimental study performed on polymethyl methacrylate（PMMA）, the quantity of contact asperities is proven to be the dominant factor that affects the real contact area. The relationship between the real contact area and the contact force in the pre-sliding regime is studied, and the distribution of static friction at the contact interface is qualitatively discussed. New phenomena in which the real contact area expands along with increasing static friction are identified. The aforementioned relationship is approximately linear at the contact interface under a constant normal pressure, and the distribution of friction stress decreases from the leading edge to the trailing edge.
