Wyniki wyszukiwania - BazTech

1

Prediction of crack depth and position in vibrating beams using artificial neural networks

Bouboulas Athanasios, Nikolakopoulos Pantelis, Anifantis Nikolaos

Diagnostyka

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2022

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Vol. 23, No. 3

art. no 2022307

EN

The aim of this paper is to develop a finite element procedure for crack prediction in vibrating beams. Based on this procedure, full frictional contact conditions are introduced between the crack surfaces in order to consider the breathing of crack. The region surrounding the crack is simulated by two-dimensional finite elements. An incremental-iterative procedure is employed to solve the nonlinear dynamic equations governing this problem. The obtained time response is processed with Fast Fourier Transform to extract its frequency components. The first three natural frequencies are input to a trained Artificial Neural Network for depth and position prediction of the crack. This study is validated for a dynamic loading cantilever beam. It is found that the proposed procedure is capable of predicting the crack depth and position with high accuracy.

2

Influence of machining conditions on friction in metal cutting process – A review

Grzesik Wit, Rech Joel

Mechanik

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2019

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R. 92, nr 4

242--248

EN

This paper presents a range of variable machining factors which influence substantially friction directly or by the tool wear developed in the cutting zone. The group of direct factors include the workpiece and cutting tool materials coupled, the cutting/sliding velocity, cooling media supplied to the tool-chip contact zone, modification of the tool contact faces by micro-texturing. Special attention was paid to the tool wear evolution and its pronounced effect on changes of the contact conditions.

PL

Przedstawiono wiele zmiennych czynników procesowych, które istotnie wpływają – bezpośrednio lub pośrednio przez zużycie ostrza – na tarcie występujące w strefie skrawania. Grupa czynników bezpośrednich obejmuje: materiał obrabianego przedmiotu i narzędzia skrawającego, prędkość skrawania/poślizgu, media chłodzące dostarczane do strefy kontaktu oraz modyfikację powierzchni kontaktowych ostrza narzędzia przez mikroteksturyzowanie. Specjalną uwagę zwrócono na ewolucję zużycia narzędzia i jej dominujące oddziaływanie na zmiany warunków kontaktowych.

3

Wpływ warunków kontaktu pomiędzy studnią startową do mikrotunelowania i gruntem na nośność graniczną podłoża

Szajna W. S.

Budownictwo i Inżynieria Środowiska

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2013

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Vol. 4, no. 1

79--86

PL

W pracy analizuje się nośność graniczną podłoża gruntowego, w którym osadzona jest cylindryczna, żelbetowa studnia startowa, obciążona poziomą siłą wywołaną mikrotunelowaniem. Zadanie sformułowano w kategoriach metody elementów skończonych. Omówiono poszczególne składowe modelu numerycznego: model konstrukcji studni, model podłoża gruntowego oraz model warunków kontaktu studni i podłoża. Przyjęto sprężysto-plastyczny model gruntu z warunkiem plastyczności Treski. Rozważano jedynie przypadek obciążenia bez drenażu. Skoncentrowano się na analizie wpływu modelu kontaktu na uzyskane wyniki nośności granicznej. Wzięto pod uwagę dwa modele kontaktu: pełen kontakt oraz kontakt z tarciem (przy różnych wartościach współczynnika tarcia) i więzach jednostronnych pomiędzy konstrukcją a podłożem. Przyjęcie najprostszego modelu – pełnego kontaktu – powoduje znaczne zawyżenie nośność granicznej układu i zaniżenie wartości przemieszczeń studni w stosunku do rozwiązań dla modelu z więzami jednostronnymi.

EN

The paper contains the analysis of the ultimate bearing capacity of subsoil, where a cylindrical starting shaft is imbedded. The reinforced-concrete shaft is loaded with a horizontal force induced by microtunneling. The problem has been considered in terms of the finite element method. The following components of the numerical model have been discussed: the model of the shaft structure, the model of the subsoil as well as the model of the shaft-subsoil contact conditions. Elastic-plastic model of subsoil has been assumed with the Tresca plasticity condition and an undrained load case was exclusively discussed. The paper focuses on the analysis of the influence of the contact model on the obtained results of the load bearing capacity. Two contact models have been considered: full contact and contact with friction (with various values of friction coefficient) and unilateral constraints between the structure and the subsoil. The adoption of the simplest model – the full contact – results in a considerable overestimation of the ultimate load bearing capacity and an underestimation of the shaft displacements in relation to the unilateral constraints model.

4

Examination of conditions in contact interface using ultrasonic measurement

Saiki H., Marumo Y., Ruan L., Matsukawa T., Zhan Z. H., Sakata Y.

Archives of Materials Science and Engineering

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2007

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Vol. 28, nr 2

113-118

EN

Purpose: In metal forming, the conditions of contact interface have a great effect on the characteristics of interface friction and heat transfer between tool and workpiece. Estimation of contact conditions in the toolworkpiece interface is required in order to optimize process conditions. Ultrasonic examination is an effective method to estimate the contact conditions. In this study, we investigated the effects of ultrasonic frequencies and intermediate air/lubricant films in the contact interface on the properties of penetration and reflection of incident ultrasonic waves. Design/methodology/approach: We have presented a method by which the contact conditions are evaluated from the relative intensity of reflected ultrasonic waves at the interface. Using this evaluation method, the relative intensity was measured continuously during processes. Findings: The effects of ultrasonic frequencies and intermediate films on the properties of penetration and reflection of incident ultrasonic waves were revealed. The presented method was effective for evaluating the variation of contact interface conditions. Research limitations/implications: Thickness of intermediate films can be measured using this ultrasonic examination. The performance of lubricants can be estimated. Practical implications: The optimization of forming processes will be achieved based on the evaluation results of contact conditions. Originality/value: Tribological conditions including intermediate air/lubricants were evaluated by ultrasonic examination. This shows the possibility that the lubricant behaviour in the contact interface is examined during processes.