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Effect of pulse shape and duration on dynamic response of a forging system

Trąbka Arkadiusz

Acta Mechanica et Automatica

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2019

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Vol. 13, no. 4

226--232

EN

Forging hammers are machines whose operation causes negative effects both at the place of their foundation (the soil settlement) and in their surroundings (e.g., vibrations propagating to the other devices, noise, etc.). Knowledge of the parameters characterizing the time history of the force that arises as a result of impact of a ram on a shaped material is of fundamental importance for the correct analysis of both the structure of the hammer and its impact on the surroundings. In the paper, the effect of the shape and duration of a pulse load on the dynamic response of a hammer-foundation forging system was assessed. An analytical method of description of the forces that arise as a result of impact of the ram on the forged material, using different forms of pulses was presented. The forces defined in this way as loads in a mathematical model of three degrees of freedom forging system were used. The equations of motion derived from d'Alembert's principle were solved numerically in the Matlab program. The analyses for eight forms of the pulse loads with the same pulse sizes but different durations were performed. The results in the graphs were presented. It was found, among other things, that a greater impact on the maximum displacement, velocity and acceleration of each component of the hammer-foundation system as well as on the maximum forces transmitted to the soil has the duration of a pulse than its shape.

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Investigation on the applicability of the time domain analysis of discharges in gases for the defect identification at AC voltage

Lühring U., Wienold D., Jenau F.

Transactions on Environment and Electrical Engineering

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2017

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Vol. 2, No. 1

34--41

EN

The partial discharge diagnosis is an established instrument for the condition assessment of high voltage insulations and equipment. Under AC voltage stress the phase resolved pattern is of great significance in order to become aware of the type of fault. As a result of the inapplicability for DC voltage stress, approaches for alternative interpretation techniques such as the time domain analysis of partial discharges were identified in recent investigations. In these different types of fault are taken into account as well as different insulating media. The purpose of this paper is to investigate whether an analysis of the pulse shape is also applicable for the defect identification under AC voltage stress. By focussing on gaseous insulating media, contact noise and surface discharges are emulated in ambient air, whereas corona discharges are emulated in ambient air and oxygen. A method for analysing discharges, occurring in the negative and the positive half-wave of the test voltage, is proposed and discussed.

3

Numerical study for determination of pulse shaping design variables in SHPB apparatus

Baranowski P., Malachowski J., Gieleta R., Damaziak K., Mazurkiewicz L., Kolodziejczyk D.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2013

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Vol. 61, nr 2

459--466

EN

High strain rate experimental tests are essential in a development process of materials under strongly dynamic conditions. For such a dynamic loading the Split Hopkinson Pressure Bar (SHPB) has been widely used to investigate dynamic behaviour of various materials. It was found that for different materials various shapes of a generated wave are desired. This paper presents a parametric study of Split Hopkinson Pressure Bar in order to find striker’s design variables, which influence the pulse peak shape in the incident bar. With experimental data given it was possible to verify the developed numerical model, which was used for presented investigations. Dynamic numerical simulations were performed using explicit LS-Dyna code with a quasi-optimization process carried out using LS-Opt software in order to find striker’s design variables, which influence the pulse peak shape.

4

Applying of PAW for Standarization of CsI(Tl) Light Output

Borgensztajn J.

Computational Methods in Science and Technology

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2010

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Vol. 16, No. 2

157-159

EN

The basis of a new method of automatic particle identification for CsI(T1) scintillators is described and discussed. A useful tool for this purpose is PAW (Physics Analysis Workstation). PAW is an interactive and object-oriented utility for visualizing data, statistical analysis and some other tasks, which combines different CERN packages. A special procedure for CsI(T1) data analysis, running under PAW in a batch mode, has been written and tested. The recent paper presents the main idea of the method and results obtained for simulated data. As the first step of the test, a relatively simple case of data has been examined. Obtained results indicate that for more complicated cases the procedure should work effectively as well.

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Partial discharge analyses ‒ a comparison of different parameters used

Benzerouk D., Patsch R., Menzel J.

Prace Naukowe Instytutu Podstaw Elektrotechniki i Elektrotechnologii Politechniki Wrocławskiej. Konferencje

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2004

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Vol. 40, nr 15

46-50

EN

In the past many approaches have been made to use partial discharge signals to monitor and characterize degradation processes in electric equipment. For the on-line monitoring of large machines or transformers or periodic off-line inspections in many cases only the change of the phase angle distributions of the occurrence of discharges is taken as an indicator for ageing processes in the insulating system. This is sufficient as an indication for the need of a more detailed examination, but often even with off-line experiments the actual change in the defect and especially its relevance for the service life remains unclear. A more detailed insight into the physics of the local degradation processes and their relevance for the ageing process of the equipment can be gained in most cases only with measurements with a continuously increased voltage load and the evaluation of the data via Pulse Sequence Analysis. The paper will discuss and compare different methods to analyze partial discharge data, starting with 'simple' frequency distributions of different parameters of the externally applied voltage load derived from the data set as a whole. As the main point sequence correlated data such as time differences between consecutive discharges will be discussed. It will be shown that in dependence on the type of defect the significance of different parameters is different.