On the Implementation of Virtual Machines in Computer Aided Education

August 22, 2009

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Leszek A. Dobrzański and Rafał Honysz

Institute of Engineering Materials and Biomaterials, Silesian University of Technology, Konarskiego St. 18a, 44-100 Gliwice, Poland. leszek.dobrzanski@polsl.pl, rafal.honysz@polsl.pl

ABSTRACT

The purpose of this article is to describe the Materials Science Virtual Laboratory, which is an open scientific, investigative, simulating and didactic medium helpful in the realization of the didactic and educational tasks from the field of material engineering, in the Institute of Engineering Materials and Biomaterials of the Silesian University of Technology in Gliwice, Poland. The use possibilities of such a virtual laboratory are practically unrestricted. It can be a base for any studies, course or training programme performed by traditional and e-learning methods. Practically imperishable, cheap in exploitation and safe in usage, virtual simulated scientific equipment encourages students and scientific workers to independent discussions and experiments, in situations where the possibilities for their execution in the physical research laboratory are restricted. During the work with the simulations, users learn the functioning principles, as well as being exposed to the investigations and experimental guidance methodology of the real device that is simulated. As an implementation example of the laboratory for didactic and educational tasks, several virtual workrooms with equipment simulations and didactic materials are presented. This project corresponds also with the global trend of expanding investigative and academic centers by means of training and experiments performed with the aid of virtual reality.

Keywords: computational material science; e-learning; computer aided teaching; virtual laboratory; training simulations

1. INTRODUCTION

The material science virtual laboratory is an open scientific, investigative, simulating and didactic medium designed to enable the performance of educational tasks by traditional and e-learning methods. It was created to help the engineers, designers and students to extend their skills in topics of materials science research, to acquaint them with the scientific tools built for research and to introduce the methodology of investigations performed with those tools.

Generally, a virtual laboratory is created to facilitate the work of students and engineers interested in acquiring skills and abilities from the field of engineering materials. It offers a perfect environment to learn about operation of real equipment, to which the students do not have access, or which they do not want to use because of inadequate knowledge of its operation procedure.^1,2,3

Consistent with the growing interest in traditional and e-education in materials, the Institute of Engineering Materials and Biomaterials of the Silesian University of Technology in Gliwice, in October 2004, started The Educational Platform, based on project Moodle (Figure 1). It offers access for students and academic staff to the electronic didactic materials helpful in courses conducted in the traditional way in the university. It is also the basis for material engineering e-learning courses offered by the Mechanical Technological Department.⁴

a)

b)

Figure 1. E-learning platform applied by the Institute of Materials and Biomaterials,
a) main screen, b) three of many courses managed by the Institute

2. THE VALUE OF THE PROJECT IN THE WORLD EDUCATION

The project presented corresponds with the global trend of expanding research and academic centers by means of training and experiments performaned with the use of virtual reality. Many of these centers abroad and in Poland already operate similar virtual laboratories used for the realization of their own research projects with the use of new possibilities, which this laboratory offers. At many such universities, learning via virtual reality is the normal form of knowledge transfer.

In Poland the creation of virtual laboratory facilities for materials science education has not been undertaken yet. This project tries to fill this gap by means of methodology and lecture guidance performed with the use of virtual equipment.^5,6,7

3. THE DEVELOPMENT OF A MATERIAL SCIENCE VIRTUAL LABORATORY

Virtual laboratories are very dynamically developed environments for simulations, gaining knowledge, and raising skills. The creators of such laboratories are in most cases the research and academic centers and specialist technical firms, using virtual reality to design their products and test their performance before they are committed to mass production. Such a form of data collection is widespread in Western Europe and the United States of America.

The systems of computer aid CAD / CAM / CAMS are already generally well-known and used. This is the symptom of the active economic politics of enterprises aiming to raise the quality and reduce the costs of offered products^8–13.

3.1. Project and the Content of the Virtual Laboratory

In the virtual laboratory are placed the virtual simulations of research equipment installed in the laboratories owned by the Institute of Engineering Materials and Biomaterials, Silesian University of Technology. In addition to this, the user will also find statements and educational materials necessary for execution of training experiments in virtual reality, the description of real investigative equipment and scientific research application methodology, current information on subjects connected with the widely understood material science topics, multimedia scientific help for better under-standing of problems, educational animations, supervisory, examination tests and advises, thematic services, the notes for the lesson and instructional presentations.

The open architecture of the laboratory will enable its continuous extension. The created virtual simulations of devices and the technical documentation of training experiments executed with their use will constantly enlarge the supplies of the laboratory, creating only in their own scientifical and didactic environment.
During the work with the simulation, the student should exactly understand the functioning principle as well as the proper usage of the given device in research. After this experience with virtual reality, re-executing of the training experiments during the work in real conditions is easy and safe, without the need for continuous reference to the instruction manual. There is also no need to ask persons already trained in its service about every detail.

However, we should clearly note that the best programmed virtual laboratory will never replace a modest real laboratory. These systems are not equivalent and they should not be exchanged, one system for the second one. Technologies virtual and real mutually complement and extend each other. Applied together, they offer larger possibilities for education and experimental experience than would be available if the real and virtual approaches were applied separately. (Fig.2) ^4,8–14

Figure 2. The conception of the virtual laboratory - replacement
of expensive equipment by the computer simulations in virtual reality on the initial
level of education and laboratory practices.

3.2. Application of the Virtual Laboratory for Material Science Purposes

The use possibilities of the virtual laboratory are practically unlimited; it can be a base for any studies, course or training programme. It is assumed that projects of the laboratory are fully multimedial. The participants of this laboratory can e.g. investigate training experiments from the definite field of material engineering, ask questions, pass tests, make contact with lecturers and the different users of the laboratory, and participate in development of its design and content.

a)

b)

c)

d)

Figure 3. Material science virtual laboratory of the Institute of Engineering
Materials and Biomaterials, Gliwice, Poland, a) entrance, b) workrooms, c) entrance door
to virtual laboratory of light and confocal microscopy, d) inside the laboratory.

Possession of equipment that is practically imperishable, cheap to operate, and easy to use certainly will encourage students and scientific workers to do independent audits and experiments in situations where the possibilities for conducting them in a real research laboratory will be limited because of high material costs, difficult access to real equipment or the possible risk of damage.

The languages of the network programming applied for creation of the virtual laboratory make possible the access to the laboratory without regard for the configuration of the computer equipment which users operate (Figure 3). The operating system installed on the computer and the internet browser used for displaying the laboratory content on the monitor screen are of no consequence.^14–16

The laboratory was tested on machines working under control of operating systems such as Windows 98/Me, Windows 2000/XP, Mandriva Linux and FreeBSD 6.2. Browsers used to the view laboratory supplies were Microsoft Internet Explorer 6/7, Firefox 2.0, Opera 9 and Conqueror 3.5. No difficulties were encountered in any of these cases. Access to the system and its service was fast and smooth.^17–21

4. VIRTUAL SIMULATIONS OF LABORATORY EQUIPMENT AS EXAMPLES OF LABORATORY IMPLEMENTATION

As the implementation examples of the virtual laboratory for the didactic and educational tasks, several simulations of laboratory equipment will be presented. All devices were made by the application for creating interactive content for the Internet, Adobe Flash.¹⁹

Figure 4. Virtual simulation of light microscope. The loaded sample is 51CrV4 steel.

4.1. Virtual Light Microscope

The light microscope is a device for observing objects under strong magnification. The light used for image generation passes through the special optical lens set, consisting usually of a combination of several adjustable optical lenses27. The simulation of the light microscope is based on the model Leica MEF 4A/M ²².

The virtual light microscope (Figure 4) simulates the basic functions of a real device, such as: the displacement of the objective table, the change of magnification, different observation techniques in the bright field, in the dark field and in polarized light with contrast. In real devices all functions are controlled by use of suitable levers or knobs. In a simulated micro-scope, they are controlled by “clicking” on corresponding buttons, or by pressing appropriate keys on the keyboard. All buttons and switches are placed in positions that are customary on real instruments.

4.2. Virtual Confocal Microscope

Confocal microscopy is a variant of light microscopy, being characterized by increased contrast, and thus higher resolution. It is used for collecting high quality pictures and/or reconstruction of pictures in three dimensions. The source of the light is the laser. This microscope enables the making of optical cross-sections of the sample, by light analysis, identifying only one layer at a time, and eliminating the light entering from layers above and below the layer of interest. The technique of confocal microscopy has found wide use in biological sciences and in technology (e.g. for the investigation of semiconductors)²⁷. The simulated confocal microscope is Zeiss LSM500 ²³.

The simulation (Figure 5) lets the user become acquainted with the basic possibilities of the confocal microscope. Reduced images of the microstructure are presented on the monitor, but the full size image is accessible through the ocular. Simulation gives control over three channels of data acquisition, red, green and blue, steered through the menus on the microscope.

Figure 5. Virtual simulation of confocal microscope.

A switch placed on the right side regulates the depth of scanning. Options on the keyboard tune up the parameters of the picture, such as brightness or contrast. Additionally, the help buttons explaining the meaning of individual options and the way of their use.

4.3. Virtual Scanning Electron Microscope

The scanning electron microscope uses an electron beam to acquire the magnified image of the investigated sample. Scanning the surface of the studied material with this beam allows the user to perceive objects a million times smaller than a human hair. It is a remarkable tool for surface topology observation²⁷. The simulation was based on building and working principles of the DSM 940 model manufactured by Opton (Figure 6).

It is possible to translate and rotate the sample inside the sample chamber. Suitable buttons and knobs on the microscope front panel control such processes as vacuum creation in the sample chamber. They also allow the user to set a suitable potential on the cathode and to set the speed of scanning the sample with the electron beam. The user can also set the required magnification and optimize the sharpness of the observed image. The simulation makes possible the observation of samples with a magnification up to 3000 times. Also several different methods of observation are implemented.

Figure 6. Virtual simulation of scanning electron microscope.

4.4. Virtual Hardness Tester

Hardness is the property of materials, which describes the susceptibility or resistance to surface deformation under the influence of an external force. Investigations are applied for various types, using various principles of hardness tests²⁷.

The universal automatic multi-hardness tester (Figure 7) enables investigation of the sample with the use of Brinell, Rockwell and Vickers methods. The user has control over the objective table, on which he has to attach the sample. Then, it is necessary to arm the machine in suitable indenter, depending on the chosen measurement method. After setting the required strength and duration of the pressure, the machine is ready to run.

Figure 7. Virtual simulation of hardness tester. In this stage of investigation
procedure the user panel for method selection is activated.

4.5. Virtual Impact Testing Machine

The Charpy hammer is a device which enables impact resistance measurement on specially prepared samples. Impact tests are performed

with the aim of determining how strong are the influences of the load and deformation speed on the mechanical properties of materials under dynamic conditions²⁷.

Investigations using the simulated device are as simple as in the real world. After lifting the pendulum of the hammer, the user should place the sample on supports. Then, it is necessary to clear the indicator by pressing the reset button. Press the release catch of the pendulum and read the indication value. The result depends on the chosen sample type. (Figure 8)

Figure 8. Virtual simulation of the impact testing machine, Charpy V sample
of 25CrMo4 steel is ready for examination.

5. THE PREPARATION METHOD-OLOGY OF VIRTUAL SAMPLES

Since the whole group of virtual investigative machines was created it could not overlook the question of the sample material. To generate the virtual steel sample, the user should use the sample generator panel, created especially for this aim. Possible is the creation of virtual sample of any material, whose parameters are enclosed in given ranges. Input data which are required by the generator are: chemical com-position, kind of thermal processing and its parameters, kind of mechanical processing, and the shape and dimensions of the of the sample. (Figure 9)

Figure 9. Sample generator panel for steel materials

The specific ranges of chemical elements, temperatures, times and kinds of cooling media for hardening, tempering, and normalization of steels are presented in Table 1.

Table 1. Ranges of input data for steels sample generator.

range	Size	Shape	Chemical Composition [%]										Mechanical treatment
	[mm]		C	Mn	Si	P	S	Cr	Ni	Mo	W	V
min	30	-round -square	0,01	0,25	0,16	0	0	0	0	0	0	0	-rolling -forging
max	220		0,57	1,57	1,20	0,3	0,28	2,20	2,08	1,10	0,32	0,26

range	Hardening			Tempering			Normalizing
	Temperature [°C]	Time [min]	Cooling medium	Temperature [°C]	Time [min]	Cooling medium	Temperature [°C]	Time [min]	Cooling medium
min	760	30	-oil -polymer -water	550	45	-air -oil -water	180	30	-air
max	980	630		750	600		980	500

To determine the properties assigned to the materials for study in the virtual devices, we used the data set consisting of over 14000 industrial melting after mechanical and heat treatment executed in the “Batory” foundry in Chorzów, Poland. The intelligent processing of data was applied with the use of artificial neural nets for prediction of material properties. For every studied property the separate neuronal net was created. Nets were trained by the method of back propagation and the conjugate gradient method^25–27.

An example of a neural net which is used to predict yield stress is shown in Figure 10. It is a multi-layer perceptron with 17 input values, 21 neurons in one hidden layer and one output value.

a)

b)

Figure 10. Neural net used to predict yield stress a) composition (MLP 17:21-9-1), b) comparative graph of values calculated with use of the neural net and determined experimentally. The correlation = 96%.

6. CONCLUSIONS

The limitations of this article allowed only for a very cursory presentation of the virtual laboratory as a didactic environment. However, these few examples show potential use possibilities for virtual reality to address scientific and educational purposes. The interaction with simulation of the investigative device opens new possibilities for acquiring knowledge and skill in the field of material science.

Creation of virtual laboratory posts had in view the reproduction of real microscope functionality, and this goal was reached. Working virtual posts give the possibility of access to an unrestricted number of students simultaneously, and are accessible on every computer connected to the global net. Virtual light microscopes provide superb training software for students who have no experience in working with real equipment. It also provides a good opportunity for practice before advancing to real investigations performed in the real world.

ACKNOWLEDGEMENTS

The authors would like to express their thanks to “Batory” foundry for access to their research results, and to Zeiss Polska for the biological samples which were helpful in the building of the virtual confocal microscope.

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