In the present paper, a new systematic iterative analytical procedure for low-velocity impact analysis of composite plates is presented. In this method, assuming the exponential equation similar to the Hertzian Contact Law, using the principle of minimum potential energy and the energy-balance model between the indenter and the plate, the unknown coefficients of the exponential equation are obtained analytically. The elastic strain energy resulting from bending in the composite plate and external work due to indentation load is evaluated using an appropriate shape function for the composite plate deformation. Using the present method, in addition to reducing the runtime, the problem-solving process is carried out with appropriate convergence. Accordingly, Contact coefficients for various types of composite plates with different boundary conditions have been calculated. The results are in good agreement with the experimental and numerical results. The force-time response and structure response to low-velocity impact with various boundary conditions are investigated. Also, considering the importance of physical and geometrical parameters such as mass and velocity of the impactor, the dimension of the composite plate, and the effect of these parameters on Contact force history are studied. It has been shown that with increasing diameter and velocity of the impactor, exponent value in nonlinear equation Contact will increase, while this parameter decreases with increasing mass of the impactor.

This paper deals with the development and modeling of cylindrical Contact theories and also the simulation of Contact forces to be applied in the manipulation of various biological micro/nanoparticles by means of the AFM. First, the simulation of Contact forces in four environments has been carried out, which are the most commonly used fluid in biomanipulation. Then, the spherical and cylindrical Contact models of Hertz and JKR have been compared for the nanoparticles of gold and DNA, and the developed cylindrical models have been validated by comparing the cylindrical Contact results with the existing spherical Contact results. The biomanipulation of rod-shaped micro/nanoparticles in different biological environments have been modeled and the results have been compared. The modeling results indicated that the JKR cylindrical model, developed in this article, had less deformation for gold nanoparticles compared with biological nanoparticles, which was justifiable in view of the considered particles’ mechanical properties.

In this paper, a finite element model is presented for the transient analysis of low velocity impact, and the impact induced damage in the composite plate subjected to low velocity impact is studied. The failure criteria suggested by Choi and Chang and the Tsai-Hill failure criteria are used for the prediction of the damage in the composite plate; then the effect of various parameters on the impact induced damage is investigated. The first order shear deformation plate theory and the Ritz finite element method are employed for modeling the behavior of plate, and the Modified Hertz Contact low is used for the prediction of the Contact force through the impact. In the numerical results, the time history of indentation, Contact force and stress during the impact and the impact induced damage is investigated. The matrix cracking and delamination in the plies of the laminated composite plate subjected to low velocity impact are studied and the effects of various parameters are investigated.

In the present paper, dynamic behavior of a multilayer composite plate with viscoelastic structural damping is investigated against a low-velocity impact by a spherical indenter. Hertz Contact Law is refined to include effect of the lower layers on the stiffness of the Contact region and used in a non-linear form. Voltra hierarchical integral is employed for modeling the viscoelastic material and the layerwise theory and non-linear strain-displacement relations are used to model the plate more accurately. To solve the governing integro-differential equations, a combination of the finite element method, trapezoidal integration method for the Volterra integrals, and the Newmark numerical time integration method is used. In the results section, effects of the various viscoelasticity parameters and the indenter velocity on the time histories of the Contact force, indentation, and lateral deflection of the plate are investigated. Results show that due to the damping nature of the viscoelastic materials, the plate rigidity and Contact force increase whereas the maximum lateral deflection and the indentation decrease. Furthermore, higher Contact forces do not necessarily indicates higher indentations.

The equations governing the motion of steel balls and their impact onto shell liners in industrial Semi-Autogenous Grinding (SAG) mills are derived in full details by the authors and are used in order to determine the effective design variables for optimizing the working conditions of the mill and to avoid severe impacts which lead to the breakage of SAG mill shell liners. These design variables are the lifter height H, the working coefficient of friction m, lifter face inclination angle j, steel ball size rB, mill rotational velocity w, and mill size R. In order to optimize the operating conditions and avoid severe impacts to its shell liners, the effect of these parameters need to be studied. The effect of lifter height (H) and the coefficient of friction (m) on some of the main impact characteristics are simultaneously investigated for a SAG mill in Sarcheshmeh Copper Complex. It was shown that as the lifter height or the coefficient of friction increases, the impact position tends to move upward, but the maximum impact force and the absolute value of the maximum principal stress decreases, reducing the impact severity.

Assessment of probability of risk occurrence to the railway system is so important because of severe cost which could be imposed to both railway administration and passengers. Wheel movement on rail is one of the factors which has significant role in overall damage of railway infrastructure. Theses interaction-based defects are divided into several categories such as wheel flat and RCF faults. Nowadays, railway administrations are interested in increasing speed and axle load of rail vehicles due to its economical advantages. Therefore, studies on wheel-rail interaction defect-base become a concern for researchers. Implementing finite element method is a major approach in determining fracture behavior of both wheel and rail. In previous studies, simulations were mainly carried out in 2D domain by considering symmetrical assumptions. The main aim of this paper is to implement FE method based on three dimensional situations with more realistic conditions to assess rail surface crack behavior which is exposed to dynamic moving load. For this purpose, stress intensity factors for different depth of crack was obtained and compared also. The results showed that by increasing crack depth and crack tip position from rail surface, the crack tip stresses and consequently stress intensity factors were decreased.

Different types of Contact, including Contact between node pairs, any-Contact of nodes, and Contacts of the entire network, are used to characterize social relations in mobile social networks. Different modes of routing, from the point of view of message delivery semantics, encompass unicasting, multicasting, any-casting, and broadcasting. Studies have shown that using probability distribution functions of Contact data, which is mainly assumed to be homogeneous for nodes, improves the performance of these networks. However, there exists an important challenge in studies on distributions. A lot of works apply the distribution of one type of Contact to other types. Hence in routing applications, it causes to use of the distribution of one type of Contact for any mode of routing. This study provides a complete solution to model each type of homogeneous Contact data distribution and to use them in different modes of routing. We propose a routing algorithm that uses this new model. Results show that our solution improves the average latency of comparing methods Epidemic, TCCB, and DR about 3.5-times, 30%, and 45%, respectively. It achieves a delivery rate of about 5% and 6%, and average latency about 6% and 8% better than that of DR and TCCB, respectively.

In the field of wheel-rail Contact, many researches have been done into rolling profiles in this paper, three wheels from passenger wagons and two standard rails UIC60 and U33 are considered. The calculation of Contact parameters including Contact surface dimensions, stress, and pressure makes it possible to investigate wheel and rail profile conformity in different Contact conditions including straight track, curving, and crossing. Hertz Contact method and finite element analysis were used for this purpose. The comparison of mentioned parameters for six pairs of wheel and rail was conducted. The results show that in the case of straight track and curving wheel III has smaller Contact stresses and pressures but in the case of crossing wheel I represents an acceptable performance in Contact with rail UIC60. Taken together, the results indicate a weak performance of rail U33 in all cases.

In this paper, dynamic analysis of doubly curved composite shells under low velocity impact is studied analytically. The governing equations based on the first-order deformation theory (FSDT) are derived for simply supported boundary conditions. The Contact force history is predicted using two models of complete and improved spring-mass. Considering the displacement components as the doubly Fourier series, equations of motion shell and impactor are solved analytically. By writing code in Matlab softwar, using Galerkin method, the dynamic response of shell is obtained. In this investigation, the effect of geometrical parameters, such as curvature changes, aspect ratio (curvature length ratio), fiber orientation, mass and velocity of impactor, with constant impact energy, on the impact response of shell is determined by two models.