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1

Application of Two Advanced Vision Methods Based on Structural and Surface Analyses to Detect Defects in the Erichsen Cupping Test

Jasiński C., Świłło S., Kocańda A.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 3

1041--1049

EN

Due to the wide range of various sheet metal grades and the need to verify the material properties, there are numerous methods to determine the material formability. One of them, that allows quick determination of sheet metal formability, is the Erichsen cupping test described in the ISO 20482: 2003 standard. In the presented work, the results of formability assessment for DC04 deepdrawing sheet metal were obtained by means of the traditionally carried out Erichsen cupping test and compared with the resultsobtained by using two advanced methods based on vision analysis. Application of these methods allows extending the traditional scope of analysis during Erichsen cupping test by determination of the necking and strain localization before fracture. The proposed methods were compared in order to dedicate appropriate solution for the industrial application and laboratory tests respectively, where the simplicity and reliability are the mean aspects need to be considered when applied to the Erichsen cupping test.

2

A New Approach to Experimental Testing of Sheet Metal Formability for Automotive Industry

Jasiński C., Kocańda A., Morawiński Ł., Świłło S.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 4

1231--1238

EN

Advanced vision method of analysis of the Erichsen cupping test based on laser speckle is presented in this work. This method proved to be useful for expanding the range of information on material formability for two commonly used grades of steel sheets: DC04 and DC01. The authors present a complex methodology and experimental procedure that allows not only to determine the standard Erichsen index but also to follow the material deformation stages immediately preceding the occurrence of the crack. Accurate determination of these characteristics in the sheet metal forming would be an important application, especially for automotive industry. However, the sheet metal forming is a very complex manufacturing process and its success depends on many factors. Therefore, attention is focused in this study on better understanding of the Erichsen index in combination with the material deformation history.

3

Detection of defects in bulging processes by means of dynamic laser speckle

Jasiński C., Morawiński Ł., Kocańda A.

Computer Methods in Materials Science

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2016

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Vol. 16, No. 1

12--19

EN

The method described in this paper has been used to determine the moment when defects appear in the form of strain localization and grooves in the Marciniak bulging tests. In this method based on dynamic laser speckle, the sheet is illuminated by laser. Interference after reflection from the specimen surface creates a characteristic image of bright and dark spots. Specimen surface changes related with deformations and movements cause changes in the shape and size of spots, which are presented by authors in the form of speckle activity image. In order to identify the type of defect, the additional 3D microscopy measurements were performed. This paper presents analysis of the changes in the speckle activity image during the bulging process which enabled the defects identification during the bulging process.

PL

Przedstawiona w artykule metoda wykorzystuje zmienne obrazy plamkowe do określenia momentu powstania wad w postaci lokalizacji odkształceń oraz bruzd w próbach wybrzuszania metodą Marciniaka. W metodzie tej blacha oświetlana jest światłem laserowym, które w wyniku interferencji po odbiciu od powierzchni próbki tworzy charakterystyczny obraz jasnych i ciemnych plamek. Zmiany powierzchni blachy związane z odkształcaniem i przemieszczaniem powodują zmiany kształtu i wielkości tych plamek, co jest przedstawiane przez autorów w postaci obra-zów OAP. W celu identyfikacji rodzaju wady wykonywane byty dodatkowe pomiary geometrii, między innymi za pomocą mikroskopu 3D. W niniejszej pracy przedstawiono analizę zmian obrazu aktywności plamek OAP w trakcie procesu wybrzuszania, której celem była identyfikacja powstających wad.

4

Extended evaluation of Erichsen cupping test results by means of laser speckle

Kocańda A., Jasiński C.

Archives of Civil and Mechanical Engineering

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2016

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Vol. 16, no. 2

211--216

EN

Erichsen cupping test has usually been used to determine the height of the cup at the moment of sheet metal fracture, defined as the Erichsen Number IE. The paper presents a proposal of using Erichsen cupping test to determine the additional parameter – the height of the cup LN-IE at the moment of localized necking in sheet metal, which usually precedes fracture of sheet metal. For this purpose, a method of localized necking detection was developed. It is based on the phenomenon of laser speckle. The results of height measurements were presented for three different grades of sheet metals used in the automotive industry: 5754 H22 aluminum alloy, DC04 deep drawing steel, and Dogal 800DP high strength steel. The differences in cup heights at the moments of localized necking (LN-IE) and fracture (IE) of the tested sheet metals were in the range of 0–8%.

5

Application of laser speckles to localized necking and cracking detection in Erichsen cupping test

Jasiński C., Kocańda A.

Przegląd Mechaniczny

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2014

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nr 9

49--54

EN

This paper deals with a measurement method based on the laser speckles phenomenon to detect localized necking and cracking of sheet metal in Erichsen cupping test. The vision system was used for the measurement of sample height. The proposed method was verified and the results of Erichsen cupping test for sheet metal grade DC04 were presented.

PL

W artykule przedstawiono metodę pomiarową wykorzystującą zjawisko plamkowania do detekcji powstającej bruzdy i pękania materiału w próbie tłoczności blachy metodą Erichsena. Przedstawione zostało stanowisko wizyjne, które umożliwia pomiar wysokości wytłaczanej próbki wraz z detekcją bruzdy i pęknięcia. Zaprezentowany został sposób weryfikacji zaproponowanej metody oraz wyniki pomiarów w próbie tłoczności metodą Erichsena dla blachy DC04.

6

Spectral analysis of dynamic laser speckle patterns by using a full-field temporal modulation method

Dake W, Chasteen E, Onyeuku C

Optica Applicata

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2013

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Vol. 43, nr 4

871--882

EN

We introduce an approach for analyzing the power spectrum of the time-varying intensity in the dynamic laser speckle patterns. The method is free from the limitation imposed by the Nyquist criterion on the minimum sampling rate. The temporal modulation shifts the intensity fluctuation spectrum by an amount that is equal to the modulation frequency. The subsequent integration of the intensity signal, performed at each detector pixel, acts effectively as a low-pass filter allowing the extraction of the spectral component at the modulation frequency. Within the speed range from 1 to 10 mm/s investigated in our experiment, the result demonstrates that the moving speed of the diffuse object can be determined with a good accuracy.

7

Monitorowanie zjawiska fotonowego czyszczenia powierzchni zabytkowej cegły za pomocą laserowych speckli

Klemm K., Klemm P., Rożniakowski K.

Fizyka Budowli w Teorii i Praktyce

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2010

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T. 5, nr 3

27-31

PL

W pracy przedstawiono wyniki badań fotonowego czyszczenia powierzchni cegły pochodzącej z obiektów zabytkowej Łodzi przemysłowej. Do monitorowania tego procesu zaproponowano zjawisko odbicia światła lasera He-Ne od powierzchni tego materiału. Zaobserwowano zależność między liczbą „strzałów" w to samo miejsce próbki, a natężeniem i parametrami laserowych speckli w kierunku zwierciadlanego odbicia. Ta zależność może być przydatna do oszacowania stopnia wyczyszczenia powierzchni próbki za pomocą nanosekundowych impulsów lasera Nd:YAG.

EN

The work present the results of experimental examinations of the laser photon cleaning of the surface of ancient brick. Lasers (He-Ne) speckles are proposed to monitoring these phenomenon. The parameters of lasers speckles were analysed. Large differences between numbers of laser "shots" and parameters of lasers speckles were observed.

8

Laser speckle contrast imaging for measuring blood flow

Briers J. D.

Optica Applicata

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2007

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Vol. 37, nr 1-2

139-152

EN

When a diffuse object is illuminated with laser light, a random interference effect known as a speckle pattern is produced. If there is movement in the object, the speckles fluctuate in intensity. These fluctuations can be used to provide information about the movement. A simple way of accessing this information is to image the speckle pattern - the fluctuations cause a blurring of the speckle, leading to a reduction in the local speckle contrast. Thus velocity distributions are coded as speckle contrast variations. The same information can be obtained by using the Doppler effect, but producing a two-dimensional Doppler map requires scanning: speckle imaging provides the same information without the need to scan. This paper reviews the development of laser speckle imaging, starting with the connection established between speckle fluctuations and movement in the nineteen-seventies. In the eighties, a photographic technique for monitoring retinal blood flow was developed, and ten years later a digital version was used to monitor capillary blood flow in the skin. Today, many groups around the world are either using or researching the technique, and the paper will close by presenting some of their recent results.