Applied Mechanics and Materials Vol. 712

Abstract: Since “Seldom have so many independent studies been in such agreement: simulation is a key element for achieving progress in engineering and science” [National Science Foundation (NSF) Blue Ribbon Panel Report on Simulation-Based Engineering Science: Revolutionizing Engineering Science through Simulation (NSF Press, May 2006)], we attempt to outline briefly new 21st century computational challenges and their potential impact on our future. We present not only the progress in computational science and engineering and/or cyberinfrastructure, but also the necessary steps to overcome the existing educational, cultural and organizational obstacles as well. The authors identify themselves with presented ideas, which have already been expressed in the past (e.g. in different position papers and reports on research directions formulated during discussion panels and workshops organized, among others, by WTEC [Information on http://wtec.org/reports.htm]).

Abstract: Design of experiment (DoE) is a methodology widely used in an industry and an academia. However the fundamentals of DoE are well known since first articles of R.A. Fisher, the uncertainty estimation is still the investigated issue due to the fact that non-linear outcome functions do not preserve the normal distribution. The analytical solutions are known only for a very limited number of transformation. Authors propose to involve a bootstrap approach to estimate the outcome uncertainty of the response surface model.

Abstract: The paper deals with the application of the so-called T-type finite elements [1] to the calculation of the exterior acoustic problems in two dimensions. The method is based on the use of asuitably truncated T-complete set of Trefftz functions over individual subdomains linked by means ofa least square procedure. The vertex singularities and the Sommerfeld radiation condition are readilyincorporated in the trial functions. In order to show the performance of the approach two examples ofcomputations for infinite cylinders (of circular and square cross section) are presented and comparedwith those obtained by means of h-adaptive FE method [2].

Abstract: Work cycle control of a compression ignition internal combustion engine based on cylinder pressure and injection pipe pressure allows optimizing many aspects of engine performance. Selected descriptors of pressure courses can be used for constructing models and classifiers to describe engine work conditions and fuel supply. The work presents the methodology for obtaining classifiers that recognize the type of fuel injected into a cylinder with accuracy acceptable in practical technical applications. These classifiers were constructed by means of two different methods from the field of computational intelligence: classification trees induction and particle swarm optimization of the classification trees. The accuracy and transparency of the proposed models were compared.

Abstract: The article deals with the problem of transition quasi-static contact in global slip under cyclic tangential load. The state of stress in partial contact, the laws of friction and scenarios of transition to slip of metal surface was determined. Partial slip is defined by the existence of stick and slip zones within the contact area. Currently, there are two basic concepts concerning surface damage processes: one connected with surface activation, which involves an increase in free energy in a tribological system, and the other connected with surface passivity, when free energy decreases. Experimental and theoretical studies were conducted to determine the contact between a sphere and a plane, which is the most suitable system for simulating small-amplitude fretting (~ 0–3 microns).

Abstract: This paper treats an iterative shooting method based on sensitivity functions for solving non–linear two–point boundary value problems (BVPs), in the form of a second–order differential equation and four boundary conditions. The solution of this BVP constitutes an in–run profile of a ski jumping hill. It is characterized by reduced a normal reaction force, which has impact on ski jumper’s legs during sliding downhill. In order to use this method, it is necessary to convert the BVP to an appropriate initial value problem (IVP). Consequently, in each iteration, we must solve a system of six first–order differential equations.

Abstract: The work presents a new approach to the power method serving the purpose of solving the eigenvalue problem of a matrix. Instead of calculating the eigenvector corresponding to the dominant eigenvalue from the formula , the idempotent matrix B associated with the given matrix A is calculated from the formula , where m stands for the method’s rate of convergence. The scaling coefficient k_i is determined by the quotient of any norms of matrices B_i and or by the reciprocal of the Frobenius norm of matrix B_i. In the presented approach the condition for completing calculations has the form. Once the calculations are completed, the columns of matrix B are vectors parallel to the eigenvector corresponding to the dominant eigenvalue, which is calculated from the Rayleigh quotient. The new approach eliminates the necessity to use a starting vector, increases the rate of convergence and shortens the calculation time when compared to the classic method.

Abstract: The Cauchy function and characteristic series were applied to solve the boundary value problem of free transverse vibrations of vertically mounted, elastically supported tapered cantilever beams. A concentrated mass was attached at the same distance from the base. The beams were subjected to universal axial loads - conservative and follow wing tangential forces - and distributed loads along the cantilever length. The general form of characteristic equation was obtained taking into account the shape of the tapered cantilever, elastic foundation and nonhomogeneous material. Bernstein-Kieropian double estimators of natural frequency were calculated based on free coefficients of the characteristic series. Good agreement was obtained between the calculated natural frequency results and the exact values available in the literature.

Abstract: The article presents a comparison of the performance of multiple rendering engines for the Blender program. Rendering times for an example model were compared in this work. Both CPU and GPU execution modes were included, using the older, more economical cards based on the Fermi architecture (GeForce GT 440 in this case) and the newer, more efficient based on Kepler architecture (GeForce GTX 680).