Papers by Keyword: Probability

Abstract: Comparison of experimental and calculated data of the excavator utilization factor in time (K_u) according to the current methods showed the absence of even a correlation between them r = 0.17, which indicates the inexpediency of using the basic models that are the basis of these methods. The reason for the low correspondence is that the excavation processes are complex random dynamic non-stationary processes, and the models that are the basis of almost all current methods are simple deterministic static models that cannot successfully operate at the level required for such processes. In the work with the application of the theory of mass service systems, a set of probabilistic dynamic non-stationary models in the form of Markov-Kolmogorov equations was developed to describe the probability of states, both for each of the selected subsystems of downtime of excavation works, and for the “excavator face” system as a whole. Comparison of the actual values of the coefficient (K_u) obtained as a result of the experiment allows us to recommend the developed set of models as the basis of the methodology for calculating K_u (r = 0.70).

Abstract: The presented study demonstrates the possibility of an analytical approach called the multi-optional hybrid-effectiveness functions uncertainty measure conditional optimization doctrine. This method is applied in order to obtain the known, therefore considered proven, solutions by-passing the entirely probabilistic approach. It is made in application to the stochastic process measures determination. Supposedly, the process is developing in the aircraft engine system’s element (the state condition of its material). The solution is found in the framework of the entropy paradigm. It helps assess the newly emerged materials applications rationality and the novelty technologies implementations expediency on condition of the operational options uncertainty.

Abstract: Experimental densities of intensity distribution for main deformations, as well as the stress strain state of a metal on the side edges of an aluminum strip during its flat rolling, have been determined. Strain, spread and extrusion ratio have been evaluated. The dimensions of the strip cross-section have been chosen in a way that minimizes spreading. Therefore, the deformed state under rolling is close to a flat one. The correlation between the deformation intensity and the stress-strain state of macro-volumes occurred on strip edges has been estimated. The parameters of two-dimensional probability-density function for the joint distribution of deformation intensity and the Nadai-Lode stress-strain parameter have been determined. Distribution densities for longitudinal, transverse deformations and the intensity of main deformations in the zone of strip rolling are bimodal, which corresponds to both forward and backward slip zones under rolling. The results of the work can be used to predict the depletion of plasticity resources during strip rolling.

Abstract: The contribution focuses on the effect of selected input parameters on probabilistic estimation of chloride induced reinforced concrete bridge deck corrosion initiation. The reinforced concrete bridge deck with steel protected by epoxy-coating is considered. A finite element diffusion model in conjunction with a probabilistic method using Monte Carlo technique is used to address the inherited randomness of input variables. Presented parametric study shows the sensitivity of estimation of the corrosion initiation likelihood on variation of input parameters.

Abstract: The strain intensity as well as the stress-strain state of grains has been experimentally estimated for aluminum sample in strip rolling. The level of correlation between the intensity of deformation and stress-strain state of individual grains in the sample has been calculated. An experimental two-dimensional function of its joint distribution has been constructed. The parameters of two-dimensional function of probability densities have been defined. A relative number of grains with deformation twice as high as the average deformation of the sample has been obtained. The results allow predicting the plasticity exhaustion in individual grains of the sample during rolling and can be used to estimate the likelihood of defects (micro pores and micro cracks) arising during the rolling of aluminum strips.

Abstract: The last accidents of the NPP in Chernobyl and Fukushima give us the new inspiration to verify the safety level of the NPP structures. This paper presents the new requirements to test of the safety and reliability of the NPP structures due to the last accidents in the world. The risk assessment to verify of the safety and reliability of the NPP structures based on probabilistic and nonlinear analysis is presented. The uncertainties of the loads level (long-time temperature and dead loads), the material model (concrete cracking and crushing, behaviour of the reinforcement and liner), degradation effects and other influences following from the inaccuracy of the calculated model and numerical methods were taken into account in the LHS method. The results of the deterministic and probabilistic analysis of the NPP structures are presented.

Abstract: The probabilistic design analyses a plate involving uncertain input parameters. These input parameters (geometry, material properties, boundary conditions, etc.) are defined in the software model. The variations of input parameters are defined as random input variables and are characterized by their distribution type (Gaussian, lognormal, etc.) and by their distribution parameters (mean values, standard deviation, etc.). During a probabilistic analysis, software executes multiple analysis loops to compute the random output parameters as a function of the set of random input variables. The values for the input variables are generated either randomly (using Monte Carlo simulation) or as prescribed samples (using Response Surface Methods). In the conclusion, some results of these probabilistic methods are presented.

Abstract: This paper presents an application of the probabilistic analysis of structural resistance of the bubble tower structure of a VVER 440/213. The evaluation is based on an extension of the smeared crack model developed on base of Kupfer's bidimensional failure criterion, rotated crack, CEB-FIP model of failure energy and implemented into the ANSYS system. The non-linear analysis was considered for the median values of the input data and the probabilistic analysis models the uncertainties of loads, material resistance and other modeling issues.

Abstract: One of the basic means of improving the reliability of technical equipment is increasing their reliability through targeted maintenance. When designing any technical equipment should be chosen minimum necessary set of technical resources that are necessary to the achievement of the required scope and quality of its functions. By setting an appropriate preventive maintenance plan can be timely and effective interventions to prevent adverse consequences of failure. This paper describes the proposal of optimal plan of preventive maintenance of experimental equipment designed for 3D machining rotating parts with AWJ technology.

Abstract: This paper presents the probabilistic safety assessment of nuclear power plant (NPP) in Slovakia due to earthquake event. The experiences from the deterministic and probabilistic seismic analyses of the structure resistance are mentioned. On the base of the geophysical and seismological monitoring of locality the peak ground acceleration was defined for the return period 10⁴ years using the Monte Carlo simulations. The synthetic spectrum compatible accelerograms generated in program COMPACEL are presented in comparison with requirements of ASCE4/98 standard.