Recent studies of strong motion data consistently show that the risetime (duration of slip at particular locations on the fault) is significantly shorter than the overall rupture duration. The physical explanation for this observation and its implications have become central issues in earthquake source studies. Two classes of mechanisms have been proposed to explain short risetimes. One explana...

A study on the evaluating equivalent damping and response modification factors of frames equipped by Pall Friction Dampers is presented. To do so, buildings with various stories were considered. Nonlinear and linear dynamic time history analysis has been performed to evaluate equivalent damping for Pall Friction Dampers. Ground motions with various frequency characteristics scaled with Iranian ...

After clutch engagement in the post-lockup phase, the contact stiffness between friction materials and separators plays an important role in the dynamic behaviour of an Automatic Transmission (AT). The friction material deteriorates progressively during the service-life of a clutch, thus affecting the contact stiffness. The deterioration therefore changes the dynamic behaviour of the AT. In ord...

The origin of friction comes from the atomic interaction at interfaces. Analytic theories indicated that there is no static friction on clean incommensurate interfaces, while a recent experiment revealed that the static friction coefficient was anisotropic with respect to the lattice orientation, but did not vanish on two clean Ni(100) mis-orientated surfaces. To understand this friction anisot...

We present a microscopic theory for dynamic friction on an intramolecular vibrational coordinate of a diatomic molecule dissolved in a simple liquid. Previous theoretical approaches to calculating dynamic friction have either used molecular hydrodynamics or employed a concept of instantaneous normal modes. Both methods have their limitations: molecular hydrodynamics is unable to correctly descr...

This work presents a nonlinear control algorithm to be applied to the trajectory tracking of a pneumatic positioning system. The objective is to compensate the highly nonlinear effects that are inherent to such systems due to the dynamic behavior of pressurized air inside the chambers and to friction forces. In order to accomplish this task, the proposed algorithm employs the feedback lineariza...

Wearless dry friction of an elastic block of weight N , driven by an external force F over a rigid substrate, is investigated. The slider and substrate surfaces are both microscopically rough, interacting via a repulsive potential that depends on the local overlap. The model reproduces Amontons’s laws which state that the kinetic friction force is proportional to the normal loading force N and ...

Melt produced by friction during earthquakes may act either as a coseismic fault lubricant or as a viscous brake. Here we estimate the dynamic shear resistance (tau(f)) in the presence of friction-induced melts from both exhumed faults and high-velocity (1.28 meters per second) frictional experiments. Exhumed faults within granitoids (tonalites) indicate low tau(f) at 10 kilometers in depth. Fr...

We introduce a method of observer design for systems described by a linear part with a nonlinear perturbation, where the perturbation is parameterized by a vector of unknown, constant parameters. The design is modular, and consists of a modified high-gain observer that estimates the states of the system together with the full perturbation, and a parameter estimator. The parameter estimator is c...

in this study, the effects of linear and rotational speed of the friction stir welding tool was investigated on the heat generation and distribution at surface and inside of workpiece, material flow and geometry of the welding area of poly methyl methacrylate (pmma) workpiece. the commercial cfd fluent 6.4 software was used to simulation of the process with computational fluid dynamic technique...