# Dr. Ireneusz Iwanowski

## 2019-(IV)-ScienceBridge GmbH: Root sided monitoring system for laser welding

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- Written by Iwanowski
- Category: Projects

The newly developed method improves the monitoring and control process for beam welding. In contrast to most commonly used methods, the new monitoring process is root sided, i. e. it takes place on the back part of the workpiece. Furthermore, the invention describes a monitoring device optimized for beam welding. Beam welding using the invention avoids incomplete fusion at the weld interface and increases the stability of the weld joint.

Macro material processing via beam welding puts high demands on the alignment and positioning accuracy of the system. Typically the welding process is monitored at the upper side of the workpiece where the optical analysis of the keyhole provides a measurement for the quality of the weld. However, incomplete fusion cannot be excluded by only monitoring the upside of the workpiece. It is, for example, not possible to register a tilt between the beam and the joining gap. Already small angles lead to incomplete fusion if the material is thick. But not only a tilted beam can lead to incomplete fusion - also the geometry of the workpiece might introduce an angle between the beam axis and the joining gap. Such an angle results in incomplete fusion at the root area even if the process is monitored on the upper side of the workpiece. The error can only be detected by monitoring the welding from the root side. Some workpieces do not allow for a perpendicular alignment between workpiece and beam axis, in this case monitoring the upside of the workpiece is equally insufficient. Finally, besides the need to adjust the alignment of the beam it is also often necessary to adjust the power of the laser beam in order to maintain the necessary welding depth. *Figure: Construction model (left) and realization (right) of the root sided process monitoring system. (Image Source: Stefan Kaierle, LZH)*

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## 2019-(III)-ScienceBridge GmbH: Resonant material processing using (ultra-)short laser pulses

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- Written by Iwanowski
- Category: Projects

The invention relates to the usage of a tunable, resonant electromagnetic field for both, the targeted fabrication of structures with dimensions smaller than the used beam diameter and the targeted fabrication of ultra small particles. Therefore, the electromagnetic field that is created by an ultra short laser pulse on the surface of an object is superposed with an external field to achieve a resonance rise specific to the processed material.

*Figure: Setup for resonant surface treatment using a laser and an external field. Via two electrodes which are located on the work piece (left- and right-hand side) of the area to be treated, a tunable electrical field can be applied. This field superposes the electro-magnetic field of the laser making it much easier to reach the material dependent resonance condition. (Source: V. Schütz)*

The conventional fabrication of micro- or nano-structured surfaces is of great interest for a huge amount of industrial or R&D applications. Using (ultra) short laser pulses, so called LISOS ("laser induced self organizing structures") can be produced quite easily. Since the process is taking place in close vicinity to the ablation threshold, small laser intensities suffice to fabricate these LISOS. However, to process larger areas the average laser power needs to be increased to several kilowatts. Taking today's state of the art, this results in high acquisition and maintenance costs for the needed laser systems consequently raising the inhibition threshold in industry.

How to solve this problem? Read More at MBM ScienceBridge here

## 2019-(II)-ScienceBridge GmbH: Laser transmission welding using carbon fiber reinforced polymers

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- Written by Iwanowski
- Category: Projects

The invention deals with laser transmission welding of glass fiber reinforced polymers or unreinforced polymers with CFRTP. The absorption of the laser beam occurs mainly on the carbon fibers, thus, adding additives for absorption is not necessary.

Different joining techniques for reinforced composites exist. Among them are the use of adhesives, rivets, induction welding, electric resistance welding or ultrasonic welding. All the available processing techniques have certain limitations. Adhesive bonds need extensive steps for surface preparation and cannot be tested for stability without destruction. Induction welding works only on conductive materials. Electric resistance welding uses a conductive mesh at the welding area which constrains the achievable geometries and remains in the material after welding. The necessity of adding absorbing additives to the joining partners is also a frequent problem with laser transmission welding. *Figure (Scheme of the laser transmission welding (Source: Peter Jäsch**ke, LZH))*

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## 2019-(I)-ScienceBridge GmbH: Absorbing nanoparticle-suspension for laser drilling

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- Written by Iwanowski
- Category: Projects

To protect the material at the backside of a workpiece during laser drilling or cutting, an absorbing material is used. Here a nanoparticle-suspension provides a particularly efficient protection with further advantages like cooling. During laser drilling, material situated behind the bore can be easily damaged by laser radiation. A common problem, for example, during the manufacturing of injection nozzles. To prevent the damage, a material which absorbs the majority of the laser radiation is placed at the working side. The material can be a solid which typically absorbs almost all of the radiation but has the disadvantage that it cannot be used if the geometry of the workpiece makes it impossible to place a solid material behind the bore. *Figure (Laser drilling without backing material damages the workpiece. A nanoparticle-suspension helps to prevent the damage. (Source: Patent application DE102013212665B4))*

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## 20180819 - SECRETS OF ALGEBRA - Logarithms in music

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- Written by Iwanowski
- Category: Forgotten Mathematics

Musicians are rarely interested in mathematics; most of them do not feel respect for this science, try to keep as far as possible from it. Meanwhile, musicians - even those who do not believe, like Salieri in Pushkin in "harmonic algebra" are confronted with mathematics much more often than they suspect, also with such "scary things" like logarithms. Let me quote a passage from the article on the subject of the Russian physicist Prof. A. Eichenwald:

"*My junior high school friend liked to play the piano, but he did not like mathematics. He even spoke with a shade of contempt that music and mathematics has nothing to do with each other. Admittedly, Pythagoras found some relations between voice vibrations, but the Pythagorean range did not find any application in our music world. Just imagine how unpleasantly surprised my friend was when I proved to him that playing on the keys of a contemporary piano, he plays, in fact, based on ... logarithms.*"

Indeed, the so-called "grades" of the tempered chromatic range are not spaced at equal distances either in terms of the number of vibrations, or in terms of the wavelength of the corresponding tones, but they are represent by the logarithms of these quantities. Only the base of these logarithms is equal to 2, not 10, as accepted in other cases.

Let us assume that the note "*do*" the lowest octave - we call it the octave zero - corresponds to *n* vibrations per second. Then "*do*" of the first octave corresponds to *2n* vibrations, and "*do*" of m-octave n * 2m vibrations, etc. We will mark all the notes of the chromatic piano range with the* p*-numbers, assuming the fundamental tone to each octave as zero; then, for example, the tone of "*sol*" will be seventh, and "*la*" will be ninth, etc .; 12th ton will be "*do*" again, only an octave higher. Due to the fact that in the tempered chromatic range each next tone has greater number of vibrations than the previous ones, the number of vibrations of any tone can be expressed by the formula:

The logarithm of the formula, is:

or

And assuming the number of vibrations to "*do*" for one (n = 1) and bringing all logarithms to the basis of 2 (or just accepting log 2 = 1), we have:

Thus, we can see that the key numbers represent the logarithms of the vibrations of the corresponding sounds (multiply by 12). We can even say that the octave numbers represent the characteristic of a logarithm, the number of the sound in a given octave (divided by 12) - the mantissa of this logarithm.

For example:

In the "*sol*" tone of the third octave, 3 + 7/12 (= 3.583), the number 3 is the logarithm of the number of vibrations of this tone, and 7/12 (= 3,583) is the mantissa of this logarithm with base 2; the number of vibrations is therefore 2^(3.583) - it is 11.98 times greater than the number of vibrations "*do*" of the first octave.

## 20180727- SECRETS OF ALGEBRA - "Difficult Task"

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- Written by Iwanowski
- Category: Forgotten Mathematics

Let us say somebody ask you to solve the next equation without using any technical aid.

Can you do this?

## 20180725- SECRETS OF ALGEBRA - TO HELP ARTYMETICS AND GEOMETRY

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- Written by Iwanowski
- Category: Forgotten Mathematics

Arithmetic often cannot prove some of its strongholds with vague means. In these cases, we need more general algebra methods. For this kind of arithmetic theorems, which justified in an algebraic manner, many rules for shortened calculation operations result. However this project is a sub-project of forgotten math and a part of **Secrets fo Algebra**.

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