P2-0270 — Annual report 2012
1.
Evaluation of corrosion resistance of AA6082-T651 aluminium alloy after laser shock peening by means of cyclic polarisation and ElS methods

Laser shock peening (LSP) without ablative coating at various power densities was applied to AA6082 aluminium alloy to investigate corrosion behaviour in a 0.6 M NaCl solution. Cyclic polarisation results showed enhanced passivity with corrosion current reduction by as much as a factor of 12, compared to the untreated specimen. Additionally, EIS after 24 h confirmed almost seven times higher polarisation resistance after LSP, compared to the untreated specimen (45 and 6.7 k cm2). XPS analysis indicated Al2O3 enrichment, which contributed to higher corrosion resistance with reduced anodic dissolution of the LSP-treated surface due to plasma ablation and shock waves.

COBISS.SI-ID: 12293915
2.
Optodynamic energy-conversion efficiency during an Er:YAG-laser-pulse delivery into a liquid through different fiber-tip geometries

The influence of different fiber-tip geometries and Er:YAG-laser pulse parameters on the dynamics of a vapor-bubble induced by Er:YAG-pulse-water interaction is presented. The optodynamic energy-conversion efficiency, i.e., the ratio between the mechanical energy of the liquid medium and the pulse energy is examined using shadow photography. The presented results are especially important for biomedical applications, where the collateral heating of the surrounding medium should be reduced (e.g., laser cleaning root canals). Moreover, these results also greatly helps to understand the key mechanisms in laser dentistry and are therefore of a great importance for the development of new laser medical applications.

COBISS.SI-ID: 12358939
3.
Two-dimensional measurements of laser-induced breakdown in air by high-speed two-frame shadowgraphy

A new method is presented that enables 2D visualization of a laser-induced break-down event in two time instances, which are delayed by an arbitrary time interval in the range from 300 ps to 30 ns. Exploiting polarization of the probe pulses, we capture two temporally and spatially separated frames with two CCD cameras. Special attention is given to the subsequent data processing, especially to the minimization of the systematic error due to alignment of both images, and to the determination of 2D velocity distribution from the captured image pairs.

COBISS.SI-ID: 12421659
4.
Discovering autonomous structures within complex networks of work systems

Modern theories propose autonomous structures as building blocks of next-generation manufacturing systems. However, their size and scope are not agreed upon and remain a subject of research. The paper presents a method for discovering autonomous structures within existing manufacturing systems. Firstly, it is shown how a complex network model of a manufacturing system can be obtained. Then, a method for discovering structure in complex networks is applied in order to find cohesive subnetworks - candidates for the formation of autonomous work systems. The approach is illustrated in a case study of engineer-to-order production.

COBISS.SI-ID: 12273179
5.
Image-based electrode tip displacement in resistance spot welding

The paper presents a new image processing-based algorithm for electrode tip displacement measurement. Its accuracy is evaluated by a comparison with a conventional optical sensor. The results show a clear advantage of the proposed image processing algorithm. A special program was written in order to analyze the algorithm. The electrode tips are detected by the program. It also determines the size of the reference areas on the electrode tips and tracks these areas during the welding process. Due to a multi-thread implementation of the algorithm the execution time was reduced significantly as compared to previously presented work. Consequently this approach is now applicable for control-related resistance spot welding purposes.

COBISS.SI-ID: 12476699