Influence of bucket wheel vertical vibration on bucket-wheel excavator (BWE) digging force

Ovaj rad daje postupak određivanja sile kopanja rotornog bagera uzimajući u obzir karakteristike kopanog materijala, reznu ivicu lopatice, brzinu rezanja i vertikalne vibracije radnog kotača (rotora). Sila kopanja ovisi o specifičnom otporu kopanju (SOK) i ukupnoj duljini reznih rubova lopatice koje su istovremeno u zahvatu s kopanim materijalom. SOK je uvjetovan karakteristikama kopanog materijala, brzine rezanja i slučajna je veličina, dok ukupna duljina reznih rubova lopatice ovisi o broju lopatica koje su istovremeno u zahvatu s kopanim materijalom i vertikalnim vibracijama radnog kotača. Funkcija promjene ukupne duljine reznih rubova lopatica u ovisnosti od vremena dobivena je na osnovu dinamičkog modela rotornog bagera u vertikalnoj ravni, uzimajući u obzir pomak središta radnog kotača.This paper provides a method of determining the BWE digging force considering the characteristics of soil which needs to be excavated, bucket cutting contour, cutting speed and vertical vibration of the bucket wheel. Digging force depends on the specific force resistance to excavation (SFRE) and the total length of buckets cutting contours that are simultaneously in mesh with the material. The SFRE is conditioned by the characteristics of material, cutting speed and it is random variable, while the total length of buckets cutting contours depends on the number of buckets that are simultaneously in mesh with the soil and vertical oscillations of the bucket wheel. Total length of buckets cutting contours time function is determined considering moving of bucket wheel center point, based on a dynamic model of BWE in the vertical plane

Influence of temperature and exploitation period on the behaviour of a welded joint subjected to impact loading

Presented in this paper is the analysis of the influence of temperature and exploitation period on the measure of fracture resistance of welded joint constituents in both new and exploited low-alloyed Cr-Mo steel A-387 Gr. B subjected to impact load. Exploited parent material was a part of the reactor mantle in exploitation for over 40 years and is currently in the repair stage, wherein a part of the mantle is being replaced with newly built-in material. Performed are impact tests of a notched specimen of new and exploited parent material (PM), weld metal (WM) and heat affected zone (HAZ), at both the exploited and new PM sides, in order to determine total impact energy, and its components, crack initiation-and crack propagation energy. Based on test results, analysis of tendency toward brittle fracture, i.e. toward an increase of in-service brittleness (ageing) represents the comparison of values obtained for characteristic areas of welded joints and the justification of the selected welding technology

Influence of temperature and exploitation period on the behaviour of a welded joint subjected to impact loading

Presented in this paper is the analysis of the influence of temperature and exploitation period on the measure of fracture resistance of welded joint constituents in both new and exploited low-alloyed Cr-Mo steel A-387 Gr. B subjected to impact load. Exploited parent material was a part of the reactor mantle in exploitation for over 40 years and is currently in the repair stage, wherein a part of the mantle is being replaced with newly built-in material. Performed are impact tests of a notched specimen of new and exploited parent material (PM), weld metal (WM) and heat affected zone (HAZ), at both the exploited and new PM sides, in order to determine total impact energy, and its components, crack initiation-and crack propagation energy. Based on test results, analysis of tendency toward brittle fracture, i.e. toward an increase of in-service brittleness (ageing) represents the comparison of values obtained for characteristic areas of welded joints and the justification of the selected welding technology

Terrorist attacks sharpen the binary perception of "Us" vs. "Them"

Terrorist attacks not only harm citizens but also shift their attention, which has long-lasting impacts on public opinion and government policies. Yet measuring the changes in public attention beyond media coverage has been methodologically challenging. Here we approach this problem by starting from Wikipedia's r\'epertoire of 5.8 million articles and a sample of 15 recent terrorist attacks. We deploy a complex exclusion procedure to identify topics and themes that consistently received a significant increase in attention due to these incidents. Examining their contents reveals a clear picture: terrorist attacks foster establishing a sharp boundary between "Us" (the target society) and "Them" (the terrorist as the enemy). In the midst of this, one seeks to construct identities of both sides. This triggers curiosity to learn more about "Them" and soul-search for a clearer understanding of "Us". This systematic analysis of public reactions to disruptive events could help mitigate their societal consequences.Comment: Peer-reviewed; Publishe

Analysis of the Laser Forming of Shaped Surfaces Using the Adaptive Neuro-fuzzy Technique

Three-dimensional (3-D) shape modelling from a flat sheet by lasers needs numerous irradiations along surface paths with different parameters of heating. In this study it was attempted to form a three-dimensional shaped surface by laser. The main aim of the study was to analyse the impact of various machining parameters like laser power, scan speed and spot diameters on the surface modelling process. Adaptive neuro-fuzzy inference system (ANFIS) and variable selection procedure was used in order to determine the parameters influence on the surface heights prediction. The selection procedure was done to obtain the found the process parameters which has the highest influence on the surface heights. The method can produce results to simplify the surface heights prediction

Influence of bucket wheel vertical vibration on bucket-wheel excavator (BWE) digging force

Ovaj rad daje postupak određivanja sile kopanja rotornog bagera uzimajući u obzir karakteristike kopanog materijala, reznu ivicu lopatice, brzinu rezanja i vertikalne vibracije radnog kotača (rotora). Sila kopanja ovisi o specifičnom otporu kopanju (SOK) i ukupnoj duljini reznih rubova lopatice koje su istovremeno u zahvatu s kopanim materijalom. SOK je uvjetovan karakteristikama kopanog materijala, brzine rezanja i slučajna je veličina, dok ukupna duljina reznih rubova lopatice ovisi o broju lopatica koje su istovremeno u zahvatu s kopanim materijalom i vertikalnim vibracijama radnog kotača. Funkcija promjene ukupne duljine reznih rubova lopatica u ovisnosti od vremena dobivena je na osnovu dinamičkog modela rotornog bagera u vertikalnoj ravni, uzimajući u obzir pomak središta radnog kotača.This paper provides a method of determining the BWE digging force considering the characteristics of soil which needs to be excavated, bucket cutting contour, cutting speed and vertical vibration of the bucket wheel. Digging force depends on the specific force resistance to excavation (SFRE) and the total length of buckets cutting contours that are simultaneously in mesh with the material. The SFRE is conditioned by the characteristics of material, cutting speed and it is random variable, while the total length of buckets cutting contours depends on the number of buckets that are simultaneously in mesh with the soil and vertical oscillations of the bucket wheel. Total length of buckets cutting contours time function is determined considering moving of bucket wheel center point, based on a dynamic model of BWE in the vertical plane

Vibro-Impact System Based on Forced Oscillations of Heavy Mass Particle along a Rough Parabolic Line

This paper analyses motion trajectory of vibro-impact system based on the oscillator moving along the rough parabolic line in the vertical plane, under the action of external single-frequency force. Nonideality of the bond originates of sliding Coulomb’s type friction force with coefficient μ=tgα0. The oscillator consists of one heavy mass particle whose forced motion is limited by two angular elongation fixed limiters. The differential equation of motion of the analyzed vibro-impact system, which belongs to the group of common second order nonhomogenous nonlinear differential equations, cannot be solved explicitly (in closed form). For its approximate solving, the software package WOLFRAM Mathematica 7 is used. The results are tested by using the software package MATLAB R2008a. The combination of analytical-numerical results for the defined parameters of analyzed vibro-impact system is a base for the motion analysis visualization, which was the primary objective of this analytic research. Upon the phase portrait of the heavy mass particle obtained, the energy of the considered vibro-impact system is analyzed. During the graphical visualization of the energetic changes, one of the steps is the process of the phase trajectory equations determination. For this determination, we have used interpolation process that utilizes Lagrange interpolation polynomial

Analysis of the Laser Forming of Shaped Surfaces Using the Adaptive Neuro-fuzzy Technique

Three-dimensional (3-D) shape modelling from a flat sheet by lasers needs numerous irradiations along surface paths with different parameters of heating. In this study it was attempted to form a three-dimensional shaped surface by laser. The main aim of the study was to analyse the impact of various machining parameters like laser power, scan speed and spot diameters on the surface modelling process. Adaptive neuro-fuzzy inference system (ANFIS) and variable selection procedure was used in order to determine the parameters influence on the surface heights prediction. The selection procedure was done to obtain the found the process parameters which has the highest influence on the surface heights. The method can produce results to simplify the surface heights prediction

Prediction of Laser Formed Shaped Surface Characteristics Using Computational Intelligence Techniques

The main purpose of this study was to establish a prediction model for parameters of shaped surface based on laser forming process. Shape modelling from a flat sheet by lasers forming process needs numerous irradiations along surface paths with different heating parameters. Since the prediction of the parameters of shape modelling could be very complex task, computational intelligence techniques could be used for the prediction process. In this article support vector regression (SVR) was applied for the shaped surface parameters prediction. The SVR model was compared with other computational intelligence models like artificial neural network (ANN) and genetic programming (GP) techniques as benchmark models. Laser power, laser scan speed and spot diameter were used as inputs. The crucial aim of the study was to predict favourable and unfavourable shape forms according to the machining parameters. By the way one should make optimal machining conditions in order to avoid unfavourable shape forms. Based on the results, SVR model outperformed ANN and GP models for the shaped surface parameters prediction

Prediction of Laser Formed Shaped Surface Characteristics Using Computational Intelligence Techniques

The main purpose of this study was to establish a prediction model for parameters of shaped surface based on laser forming process. Shape modelling from a flat sheet by lasers forming process needs numerous irradiations along surface paths with different heating parameters. Since the prediction of the parameters of shape modelling could be very complex task, computational intelligence techniques could be used for the prediction process. In this article support vector regression (SVR) was applied for the shaped surface parameters prediction. The SVR model was compared with other computational intelligence models like artificial neural network (ANN) and genetic programming (GP) techniques as benchmark models. Laser power, laser scan speed and spot diameter were used as inputs. The crucial aim of the study was to predict favourable and unfavourable shape forms according to the machining parameters. By the way one should make optimal machining conditions in order to avoid unfavourable shape forms. Based on the results, SVR model outperformed ANN and GP models for the shaped surface parameters prediction