The reflection of light from the surface of an elastic solid gives rise to various types of elastic waves that propagate inside the solid. The weakest waves are generally those that are generated by the radiation pressure acting during the reflection of the light. Here, we present the first quantitative measurement of such light-pressure-induced elastic waves inside an ultrahigh-reflectivity mirror. Amplitudes of a few picometers were observed at the rear side of the mirror with a displacement-measuring conical piezoelectric sensor when laser pulses with a fluence of 1 J=cm2 were reflected from the front side of the mirror.
COBISS.SI-ID: 13195035
This paper deals with laser coating of ceramics by deposition of a precursor powder mixture of TiB2TiCAl on an EN AW 6082-T651 aluminum alloy. The resulting coating was studied by means of a microstructural and mechanical analysis. The coating has with TiC and TiB2 particles of various shapes and sizes embedded in an Al matrix, as well as being adherent and free of cracks with an average porosity lower than 2%. Microhardness in the coating is 40% higher than the uncoated alloy, while the microhardness in the laser melt zone and heat-affected zone dropped significantly. The wear test showed a great improvement in terms of the mass lost after the 30 min test. The three-point bending test was used to determine the flexural properties of the coated aluminum alloy. Higher content of TiB2 in ceramic components increases the flexural strength of the coated specimens, delaying the occurrence of the first crack in the coating or the occurrence of delamination. The measurements of residual stresses confirmed the presence of favorable compressive residual stresses in the surface coating. With depth, these stresses become tensile.
COBISS.SI-ID: 13047323
We present an improved optodynamic (OD) method which enables measurement of the distance between the OD source on the ablated surface and a piezoelectric sensor above it, with a relative error of about 1%. The method is based on the point explosion model and allows determination of the distance to the OD source and the released energy for each detected OD signal. We estimate the distance and released energy on the basis of two measured OD signal characteristics: the time of flight and the duration of the compressive phase. We show that the finite aperture of the sensor needs to be taken into account to improve measurement accuracy. We present experimental validation of the method using an Er:YAG laser and water as a tissue phantom. We observe an excellent agreement between the measured and theoretical OD signals and between the measured and estimated distances. The method opens the way to practicable implementations of on-line OD monitoring of laser ablation in surgery and medicine.
COBISS.SI-ID: 13202459
Anomaly detection in material flow refers to the detection of irregular patterns in shop floor behaviour. As anomalies often translate to harmful effects on a larger scale, it is important to detect them in due time. In the paper, the manufacturing shop floor is considered as a dynamic network with work systems acting as its nodes and with material flow creating connections between them. Regularities and irregularities are defined as specific patterns within the network. The approach is studied through simulation and applied to an industrial case study. The results suggest potential use for decision making in production management.
COBISS.SI-ID: 12827419
In this paper a novel approach for temperature measurement during resistance spot welding is presented. The temperature is measured by two thermocouples mounted at the ends of both the electrode tips. The authors chose to mount them there because it was expected that it would be possible to measure the temperature at this point using a digital camera in the near future. The research was, therefore, motivated to obtain various pieces of information about the welding process from the measured temperature profiles. The measured temperature profiles showed a good correlation with the weld strength. Other phenomena, such as expulsion and electrode wear, can also be related to a temperature profile.
COBISS.SI-ID: 13109019