Rate Dependent Friction Model Research Articles

Performance Comparison Analysis of a Bridge Installed with Anti-seismic Devices using PVDF/MgO Friction Material According to Friction Analysis Models

In this study, structural analyses were conducted to analyze the performance of a bridge to which friction pendulum systems (FPSs) were applied using different friction models. A Coulomb friction model and a rate dependent friction model were constructed using the friction coefficient of a PVDF/MgO friction material to analyze the effect of different friction analysis models. The Coulomb friction model uses a single friction coefficient regardless of friction velocity, while the rate dependent friction model can reflect the change in the friction coefficient with friction velocity. Nonlinear time history and seismic fragility analyses were conducted to confirm responses of the bridge. The seismic responses of a deck and a column were used to evaluate the performance of the base isolated bridge, and a friction model that can effectively evaluate the performance of isolated bridges was analyzed.

Experimental and numerical analyses of carbon steel sheet metal forming process using strain rate dependent friction model

Abstract The main objective of this study is to test experimentally and model numerically the forming process of a carbon steel cylinder including deep drawing, walls ironing, and annealing steps. The experimental tests were conducted using two drawing and ironing rings separated by a spacer ring. The geometric modeling of various stages of formation was conducted by applying the finite element method (FEM). The results obtained from the finite element model were compared and verified with the experimental tests. The output results showed a good agreement with the experimental tests. In addition, the effects of the forming parameters such as drawing speed on residual stresses and drawing force and cup height were investigated through FEM in two friction modes: strain rate-dependent coefficient of friction model and constant coefficient of friction. The results show that the coefficient of friction has a major effect on the drawing force and the wall thickness reduction.

Temperature and strain rate dependent friction model for hot forming of Ti-6Al-4V titanium alloy

Abstract Friction plays a significant role in hot deformation processes of metals. The effect of friction is especially important during hot deformation of titanium alloys. In this study friction factors in Levanov and shear laws during deformation of the Ti-6Al-4V titanium alloy at the temperature of 925 °C without lubrication, with lamellar graphite, tungsten disulfide and hexagonal boron nitride lubrication were studied. Effect of temperature in range of 825 °C–925 °C and strain rate in range of 0.01 s−1–1 s−1 on the friction factor with hexagonal boron nitride lubrication also was studied.

Numerical Analysis of Fretting-Wear With a Hybrid Elastoplastic Friction Model

Fretting-wear is a common problem in different industries, especially when it comes to interactions between metallic components. Flow-induced excitation forces in heat exchangers for instance cause tube-support interactions. The long-term interaction is an important phenomenon, which may cause fretting-wear of the tubes. Experimental tests of the interaction show the occurrence of stick–slip intermittent behavior in the tube response. To precisely simulate the intermittent stick–slip behavior, it is crucial to refine the conceptual model of the coefficient of friction for the entire motion from absolute zero velocity to gross slip phase. The incorporated friction model plays an important role in the determination of the level of fretting-wear in the system. The friction model should satisfy two important criteria. The first important aspect is the strategy of the friction model to detect the cessation of sticking, the beginning of partial-slipping, and establishment of the sliding region. The second important aspect is defining a friction coefficient function for the entire system response to precisely represent the transient stick–slip regions. In the present work, the velocity-limited friction model was compared with the LuGre model, which is a rate-dependent friction model. The effect of varying the break-away force and Stribeck effect on the stick–slip region were also investigated. Furthermore, the criteria to demarcate the stick–slip region in the LuGre model are discussed, and a different method to incorporate the Stribeck effect and presliding damping in the Dahl friction model is proposed. Using the tangential stress distribution in the contact area, a new hybrid spring-damper friction model is developed. The model is able to estimate the elastic, plastic, and partial-slipping distances during the relative motion. The ability of the model to reproduce experimental tests is investigated in the present work.

Experimental verification of rate-dependent elastoplastic analogy friction model and its application to FE analysis

When two solid bodies in contact slide slowly past each other without lubrication, an intermittent vibration phenomenon might be observed. Such rate-dependent frictional behaviors are referred to as stick–slip motions, and such motions can impair the stability of machines and structures. The aim of this study is to propose a numerical approach for analyzing stick–slip motion; the approach is based on the finite element method implemented using a rate-dependent friction model. First, we demonstrate the capability of the rate-dependent friction model by comparing its results with experimental results obtained under various material and dynamic conditions. Then, a simple finite element analysis of rate-dependent frictional sliding behavior, including stick–slip motion, is carried out to examine the effect of the material and geometric properties and boundary conditions on the numerical results. The present numerical approach can consider not only the properties of friction and materials but also variations in boundary conditions.

S1107-1-3 スティックスリップ運動に対する有限要素解析法の一提案([S1107-1]トライボロジーにおける実験・計測・解析手法の新展開)

In the present study, a phenomenological rate-dependent friction model is implemented in the dynamic finite element method. Typical frictional contact problems, which are consisted by elastic and rigid bodies having simple shapes, are then analyzed by the present method. The validity of the present method for the analysis of stick-slip motion under dry condition is examined. It is shown that the present method can solve stick-slip motion within the framework of continuum mechanics, whereas it cannot predict by the conventional finite element method based on the rate-independent friction model.

Coseismic and postseismic deformation associated with the 2003 Chengkung, Taiwan, earthquake

SUMMARY We use GPS-derived coseismic and postseismic displacements of the 2003 Mw 6.8 Chengkung, Taiwan, earthquake to examine seismogenic behaviour of the southern Longitudinal Valley. We invert for fault slip on the Chihshang fault, a segment of the Longitudinal Valley fault, based on a simplified layered earth model and a listric-shape fault geometry. Our model infers that maximum coseismic slip of about 0.72 m occurred at a depth of 15 km. Conversely, postseismic slip of about 0.1 m over a 157 d period mainly occurred at depths less than 10 km. We find an anticorrelation between coseismic and postseismic slip distributions. However, the depth profiles of seismicity before and after the main shock are very similar and both show the peak seismicity at 15–25 km depth, consistent with the depth range of large coseismic slip. The potency distribution at depth reveals a coseismic slip deficit at shallow depths, which is compensated by postseismic and interseismic creep associated with the Lichi Melange. Aseismic slip is an important component of the slip budget on the Chihshang fault. According to the historic earthquake records, interseismic slip rate and coseismic slip on the Chihshang fault, the recurrence interval of this type of event is between 12 and 36 yr. We use a rate-dependent friction model of afterslip to infer the frictional parameter, dτss/dlnV= 0.03–0.5 MPa, at shallow depths on the Chihshang fault. Assuming effective normal stress of 100 MPa at 5 km depth, the rheological parameter, , is about 3 × 10−4–5 × 10−3, which is in good agreement with laboratory experiments.

Polymer entanglement density and its influence on interfacial friction

The entanglement density of amorphous glassy polymers is well known to control their fracture mechanisms under tensile loading. There have been some reports indicating substantial deformation of a glassy polymer's surface region when exposed to interfacial friction. It is shown conclusively here that there is a direct correlation between the entanglement density of a glassy polymer and the deformation mechanisms that facilitate sliding friction. This correlation was shown experimentally by studying the topography of polymer surfaces following a single sliding pass by an inorganic glass sphere. Four different polymers were studied, including polystyrene cross linked to different degrees. It is also shown that permanent plastic deformation accompanies interfacial friction, and, furthermore, that the type of deformation is a direct function of the respective polymer's entanglement density. In contrast, no difference in the observed friction force could be attributed to the entanglement density of the respective polymers. The findings can be explained by the state- and rate-dependent friction model.

State and Rate Dependent Friction Laws for Modeling High-Speed Frictional Slip at Metal-on-Metal Interfaces

In the present paper the applicability of state and rate dependent friction laws in describing the phenomena of high speed slip at metal-on-metal interfaces is investigated. For the purpose of model validation, results of plate-impact pressure-shear friction experiments were conducted by Irfan in 1998 and Irfan and Prakash in 2000 using a Ti6Al4V and Carpenter Hampden tool-steel tribo pair are employed. In these experiments high normal pressures (1-3GPa) and slip speeds of approximately 50m∕s were attained during the high-speed slip event. Moreover, these experiments were designed to investigate the evolution of friction stress in response to step changes in normal pressure and also in the applied shear stress during the high-speed slip event. A step drop in normal pressure is observed to result in an exponential decay of the friction stress to a new steady-state characteristic of the current normal pressure and the current slip velocity. A step drop in applied shear stress is observed to lead to an initial drop in friction stress, which later increases toward a new steady-state friction stress level. In response to the step drop in applied shear stress the slip velocity initially increases and then decreases to a new steady-state level consistent with the new friction stress level. A modified rate and state dependent friction model that employs both velocity and normal stress dependent state variables is used to simulate the experimental results. A good correlation is found between the experimental results and the predictions of the proposed state and rate dependent friction model.

Low-velocity friction between macroscopic solids

We analyze the physical mechanisms taking place in unlubricated friction between surfaces of micrometric roughness at sliding speeds <100 μm ·s −1 . This analysis is based on extensive experimental investigations of the time and velocity dependences of static and dynamic friction forces, and of non-stationary sliding. It fully supports the state and rate dependent friction model first proposed by Rice and Ruina.

Physical analysis of the state- and rate-dependent friction law: Static friction

We report an extensive study of dynamic friction at nonlubricated multicontact interfaces between nominally flat bodies, rough on the micrometer scale, made of identical polymer glasses. This work, which complements a previous study of static friction on the same systems, has been performed at temperatures ranging from $20\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ to close below the glass transitions. The data are analyzed within the framework of the Rice-Ruina state- and rate-dependent friction model. We show that this phenomenology is equivalent to a generalized Tabor decomposition of the friction force into the product of an age-dependent load-bearing area and of a velocity-strengthening interfacial shear stress. Quantitative analysis of this latter term leads to associate velocity strengthening with thermal activation of basic dynamical units of nanometer dimensions. We interpret our results with the help of a model due to Persson, in which shear is localized in a nanometer-thick interfacial adhesive layer, pinned elastically at a low shear level. Sliding proceeds via uncorrelated depinning of ``nanoblocks'' which constitute the layer. It is the competition between the drive-induced loading of these blocks up to their depinning stress and the thermally activated premature depinning events which leads to the velocity-strengthening contribution to the interfacial strength. In our interpretation, friction therefore appears as the localized elastoplastic response of a confined amorphous interfacial layer.

Non‐linear rate dependent deformation under compression due to state variable friction

Observations of strain‐rate effects in brittle failure under compression have been interpreted as suggesting that sub‐critical crack growth plays an important role in the deformation process. We suggest an alternate interpretation in which strain‐rate effects are attributed to rate‐ and state‐dependent friction along parent cracks. Using independently measured friction law parameters we demonstrate that a wing crack model incorporating state variable friction replicates the observed dependence of the stress‐strain curve on applied strain rate. Model results are essentially equivalent to those of an earlier model incorporating sub‐critical crack growth, suggesting that despite their different conceptual foundations, the validity of either model can not be determined on the basis of the observed strain‐rate effects. However, only the rate‐dependent friction model reproduces the observed unsteady growth of wing cracks.