The purpose of this study is to analyze the accumulation and distribution of stress across fault planes using an analytical model based on the reflection of the detector spectrum on the roughness of the fault surfaces during the failure. Fault Modeling is based on Asperities making half-spaces separated from each other. This model considers mechanical interaction between contact points and, therefore, can provide a physical explanation of how to redistribute stress at fail time at a locked fault plane. For a boundary condition, a certain displacement, normal and shear forces are calculated at contact points and compared to the failure criterion. If one or more locked surfaces of the fault do not work, the stresses are recalculated. The stress redistribution that is caused by the failure may cause other locked surfaces to fail. This process continues to achieve a stable state or complete failure of entire fault plane for analysis with detector spectrum. The distribution of stresses as well as the onset and progress of failures depend on the contact geometry and roughness.

In this study, we estimated a local seismic hazard map for the Alborz tectonic region located in north of Iran. The technique of mapping local recurrence time, TL, was used to map major Asperities of the region and the Asperities considered as the area with maximum hazard probability. The analysis was done on the epicenter of more than 5000 events recorded in 19 stations of the Institute of Geophysics, University of Tehran (IGUT), during 1996-2008. Based on the idea that b-value is inversely related to applied stress, we calculated local b-values for each grid and areas with lowest b- and a-values, and as a result shortest TL were interpreted as Asperities. Because the ruptures start from the Asperities, the mentioned regions have considered as the region with the maximum seismic hazard. The rupture location of MW 6.3 Kojour-Firooz Abad earthquake compared to the recurrence time map and it resulted in the location of this event had showed anomalously short TL based on the background seismicity of region in a decade before it. We computed TL map based on the seismicity before and after Kojour-Firooz Abad earthquake and showed that this large event redistributed the applied stress in the Alborz region. Redistribution by large earthquake led to migration of the applied stress from west of region to east. Based on the microseismicity of the region after Kojour-Firouz Abad earthquake, there are three anomalies in TL map positioned in eastern Alborz. These anomalies are introduced as the regions with maximum seismic hazard for future large earthquake.

In this research, the friction between the contact surfaces was modeled and simulated with random distribution of roughness in Nano scale. For this purpose, firstly the modified AMM friction model was derived for the contact between smooth flat/ rough flat surfaces on the basis of JKR contact model, HK friction model and random distribution of Greenwood-Williamson (GW) model. According to the results of simulation, the modified AMM friction model predict more value for the friction force considering Nano scale surface interaction forces, and it also has more accuracy in comparison to the initial AMM model. In the following, the obtained model was extended for evaluating the friction between smooth spherical/rough flat surfaces and finally the friction between the tip of Atomic Force Microscopic on the rough surface, then the effects of geometric parameters of surface included of standard deviation of Asperities’ height and radius of Asperities’ peak on the magnitudes of normal load, friction force and finally friction coefficient between atomic force microscopic tip and rough surface has been investigated. The achieved results demonstrate that normal force and friction force both will raise by rising of standard deviation of Asperities’ height while as friction coefficient will decrease. Furthermore, the normal and friction forces and also friction coefficient will increase by increase of roughness’ peaks radius. It is also observed that the effects of standard deviation of Asperities’ height on friction parameters is more than the effects of Asperities’ peaks radius.

Due to the energy concerns, it is always desired to run the mechanical elements under optimized operating conditions. Many lubricated mechanical elements such as gears, rolling element bearings, cam and followers etc. usually operate under mixed-lubrication regime. In this regime, both the lubricant film as well as the Asperities contribute in carrying the load. The life span of these elements is divided into two regimes: running-in and steady-state. In this research an efficient model has been presented to predict the variation in Asperities height during running-in. The predicted results are verified with experimentally-obtained published data. A parametric study on the effect of operating conditions such as load and speed as well as initial surface roughness and material hardness on the roughness variation during running-in has been conducted.

This paper presents a new model to study the friction between rough surfaces with random distribution of the Asperities, taking into account the contact mechanics. The results obtained show that as the surface separation decreases, the normal and friction forces increase and the coefficient of friction decreases. This model predicts higher friction forces and coefficient of friction than the model based on the Hertzian contact model. The sensitivity of the coefficient of friction to material properties is investigated using two sets of material properties. Assuming that the standard deviation and the radius of the Asperities are constant, the first set investigates the variation of the adhesion energy, length of Burgers vectors, and elastic modulus parameters for the base material silicon. In the second set, real materials such as silicon, Fe, Cu, Au, and Ag are studied in contact with a silicon substrate. The results show that the friction coefficient decreases with the increase of the adhesion energy and increases with the increase of the length of Burgers vectors and elastic modulus.

This paper analytically derives the Maxwell slip model associated with a frictional rough contact interface using the multi-asperity contact theory in the elastic region. The multi-asperity contact theory based on the Mindlin solution relates interface roughness, material properties, and preload to the contact interface Jenkins element parameters of the discrete Maxwell slip model and continuous Iwan model distribution function. The rough surface properties are obtained from the measured roughness profile of two contacting surfaces. The main advantage of the proposed analytical Maxwell slip model is there is no need to update or identify any parameter using experimental test data. In achieving a rough interface discrete Maxwell slip model, the interface contacting Asperities are grouped based on their heights, called a height-region element group of the contact interface model. Each height-region Asperities' contact area is divided into annular areas; the number of annular areas determines sliding motion states. Using the classical Mindlin solution, a Jenkins element is assigned to each specified annular area using the Hertzian normal pressure distribution function of the contact area and contribution to the tangential contact stiffness. The Iwan and Maxwell slip model's resultant hysteresis curves are compared with the analytical multi-asperity contact model to verify the proposed contact model procedure's accuracy. Model predictions of the proposed procedure are also validated against measured frictional contact behavior, resulting in good agreements with experimental observations.

The Bakharden-Quchan Faulted Zone is located in central Part of thrusted-folding belt of kopeh Dagh in NE border of Iran-Turkmenistan with array of active right lateral strike-slip faults by trending NW-SE that their ends have bent to joint blind faults in thrusts. Mechanism changing faults to reverse have caused to increase stress, shortening by thrusting in their ends bending. Most of the historical and instrumental earthquakes have distributed around faulted system of Bakharden-Quvhan Zone. Seismicity results of this zone with microseismics and computing parameters of b-value, fractal dimension (D) and mapping of local stresses distribution could have achieved us precious data on crust tension distribution, mechanism faults and system fault changes during time and place of probable occurrence future earthquakes. In neo-tectonic active zone b < 0/6 to 1/1 and D changes between zero to 2. If b< 0/6 and D closes to zero, faults and earthquakes will concentrate in Asperities with high rate of stress but if b> 0/6 and D closes to 2 faults and earthquakes will scatter in whole of zone with low rate of stress. Occurrence of major earthquakes are not far away expectation in edge of Asperities although there is a possibility that they gradually loss energy to get inactive because the seismology way of releasing energy in these faults is, when group of faults approach to motion threshold are increased b-values and other group of faults are accumulating energy, so their b-values are decreased.

Effect of discontinuities roughness including tooth-shaped asperity, rough undulating and smooth plane having different orientations respect to confining pressure on the strength of rock under triaxial stresses has been investigated in this research. 15 groups of specimens having three types of discontinuities roughness and five types of slope angles from 0 to 90 degrees have been successfully prepared and tested under triaxial stresses. The axial strength of rough undulating and tooth-shaped asperity discontinuities decreases a little with increasing slope angle from 30 to 45 degrees under constant confining pressure and in general the axial strength of smooth plane discontinuities having different orientations is less than the axial strength of rough undulating and tooth-shaped asperity discontinuities under the different confining pressures. For tooth-shaped asperity discontinuities having orientation angles 45 degrees, failure also occurred at the body of the specimens particularly with increasing the confining pressure. Sliding occurred at the one side of tooth-shaped Asperities of discontinuity having orientation angles of 60 degree under uniaxial loading and displacement took place at the direction of discontinslopeuities. But tooth-shaped Asperities were broken along the discontinuities under the higher confining pressures. The effect slope angle on the axial strength decreases with an increase of confining pressure and rate of reducing the axial strength increases with an increase of discontinuity roughness. As, the strength of specimens having very rough discontinuities under high confining pressures approaches to the strength of massive (intact) rock. The maximum axial strength to the minimum axial strength ratio (Rtriax) has high value for the zero confining pressure and it decreases sharply as a negative power function of confining pressure then approaches to a constant value.

Roughness is one of the geometrical properties of rock joints that can be expressed through various methods. In this paper, eight different parameters were used to estimate the joint roughness coefficient (JRC) of 112 joint roughness profiles. The range of variation of these parameters in a given roughness class is relatively large. These roughness values overlap with their adjacent classes. In order to use two parameters simultaneously to estimate the JRC matrix, the interaction of these parameters on the JRC value were evaluated. The resolution of different roughness classes in different scenarios was evaluated using Pearson correlation coefficient and using engineering judgment. So in this paper, a new method based on the classification of joint roughness coefficient (JRC) by support vector machine (SVM) is purposed. So in this paper, a new method based on the classification of joint roughness coefficient (JRC) by support vector machine (SVM) is purposed. Different joint roughness parameters including Z2, RP, Grasselli2D, standard deviation of Asperities height (SDH), standard deviation of profiles height variation (SDPHV), standard deviation of Asperities angle (SDA), and geostatistical parameters including range (a), sill (C), CA and SRv were evaluated for 112 joint roughness profiles. Using these 8 parameters, an 8 by 8 interaction matrix was created which consequently resulted in 28 individual two-dimensional JRC classification scenarios. A graph with SDH and SDA was selected for the Statistical classification of JRC (SCJRC) because of the relatively obvious boundary between JRC classes and easy calculation. Finally, data classification was performed by SVM. The estimation of SCJRC was checked by 20 experimental direct shear test data. A good agreement is observed between SCJRC and experimental results. The results illustrate that SCJRC is an appropriate method for the estimation of JRC.