•A new test bed for testing the impact of hail on solar modules was developed.•The research methodology of determination of the contact force limit was described.•Solar module materials experimental ...and theoretical modal analysis was conducted.•The impact of a hail ball on solar modules was examined.•A theoretical study of improving the resistance of solar modules was performed.
Climatic conditions, such as hail, strongly affect the efficiency of photovoltaic (PV) modules. The aim of this paper is to present comprehensive analytical and experimental research results and to evaluate the impact of hail on PV modules. The experimental study was conducted using a new approach in hail simulation testing the impact on PV modules. The impact of hail was compared using mechanical parameters, which were in turn reflected by electric power produced by a PV module. Based on both simulation and experimental results, optimization guidelines were proposed to improve mechanical resistance of PV modules. The scientific novelty of the article is the optimization of the theoretical model of the PV element based on experimental data. Mechanical impact parameters in PV modules, such as force transmission and final stress, decreased from 236 kN/m2 to 109.8 kN/m2 during the optimization process (geometry packages to obtain the lowest stresses).
The durability and endurance of the exploitation of railway bridges depend on the intensity and the manner of the static and dynamic loads affecting them. Heavy freight trains passing the bridges ...cause huge vertical and dual-axis vibrations, which are evidenced by the fatigue of the construction of the bridge. The scatter of the acceleration intensity of the railway bridge vibratory oscillation and their parameters are analysed while applying the theory of covariation functions. The results of the measurements of the intensity of the acceleration of vibratory oscillation in the points of support beams recorded in the timescale in the form of arrays (matrixes). Applied covariance function method provides measurement equipment and experimental simplicity of the analysis of the railway bridge vibration signals. The standard scores of mutual covariation functions of the array of the measurement results of the acceleration of digital vibratory oscillation and the standard scores of the auto-covariance functions of separate arrays are altering considering the interval of quantization in the timescale. Results gained by analysis prove the advantage of the rationed auto-covariational functions method while analysing the dynamic oscillation of bridges.
•Some surface roughness parameters of metal parts are analysed.•The programme for the graphical visualization of digital images was developed.•The calculations for evaluating of digital images are ...presented.
The article analyses some surface roughness parameters of metal parts determining the ability of the surface of digital image identification, covariance functions and Wavelet’s wave theory. Expressions of covariance functions are formed using random functions, made by spreading digital image pixel arrays by columns in the form of individual vectors. The digital images used for research may vary in scale, because the frequencies of colour waves with individual pixels remain constant in the images, therefore, the image change does not influence the scale in computing covariance functions. The colour spectrum of RGB format was applied to identify the surface images of the parts. There was analysed the influence of individual RGB colour tensor components on the estimates of digital image covariance functions. The identity of digital images was evaluated by the change of correlation coefficient values in the range of RGB colours. The software was applied to compute the above process.
The impact of hail ice cubes on composite structures (such as solar cells) causes actual defects. This article presents a series of tests, in which solar cell modules were exposed to hail simulation ...testbed balls, allowing to assess the following: the impact energy, which causes the major defects in solar cells; the formed micro-cracks in the structure of solar cells, resulting in the loss of power generated by a solar cell; and the solar cell parameters necessary for modelling. In addition, this article presents a digital analysis of hail simulation. Information received from the digital analysis was used to optimize the structure of solar cells in order to improve its resistance properties. The aim of this study was to present a simple method for experimental hail simulation. The proposed hail impact estimation method can be successfully applied to study the influence of the mechanical–dynamic impact of photovoltaic (PV) modules of different structures on the technical characteristics of these modules (structural stability, power generation, etc.). The study showed that PV modules are subjected to an irreversible effect of the excitation force (i.e., micro-cracking) and it can reduce the generated power by 2.33% to 4.83%.
There were used the spherical lenses in industry conventional for long time, but new types of lenses were created during innovation processes. One type of lenses is aspherical. Two main parameters ...describing quality of aspherical lenses are accuracy of the form shape and surface roughness. These parameters can be obtained after last operation – polishing. Technical parameters that give the biggest influence to form shape and surface roughness were investigated in this experiment and optimal technical parameters for polishing process were established. Melted quartz ,,UVFS” was used in this research, investigations were carried out according by full factorial design. Five axis CNC machine Schneider SCPA100 was used for polishing and profilometer Nanoscan 855 was used for measurements. After analysis of results it was found out that speed of rotation and penetration depth are the most important factors in polishing process. For getting the best shape it’s necessary to use the smallest chosen values of speed of rotation and penetration depth, for getting the best surface roughness polishing parameters changing conversely. The smallest value of surface roughness Rz was 0.06 µm, and shape deviation was 2.6 µm. Optimal polishing parameters for the best quality of aspherical lenses was provided.
Method of processing water-soluble potassium dihydrogen phosphate (KDP, KH2PO4) crystal is presented in this article. Diamond wire cutting machine “RTS 440“ was used for cutting. Only one of cutting ...parameters – vertical feed rate of diamond wire – was varied during experiments. Other cutting parameters (speed and strain of wire, cutting method, cutting angle) were constant. Original kerosene cooling system was designed and produced. Results are presented as graphs of dependence of arithmetic average surface profile deviation Ra of KDP and cutting time on vertical feed rate. Optimal interval of feed rates was obtained.
The article analyzes vibrational oscillation’s strength dissemination and the parameters in the centering and leveling table using the covariance function theory. The implementation of measurement ...techniques requires to use most advanced ideas, and to seek and develop new tools, based on which the direction of angle calibration system’s development could be substantiated and calibration methodologies could be enabled. Vibrational oscillation strength measurements across fixed five ring points’ observations were recorded on a time scale in five vectors arrays (matrices). The covariance functions have enabled the evaluation of the influence of the vibrations of the corresponding rings on the accuracy of the measurement results. Expressions of auto-covariance and cross-covariance functions show the changes in the time scale of the interdependence between the parameters of the corresponding vibrations of the rings on the smoothing device. These changes significantly affect the measurement data errors. The digital vibrational strength measurement arrays’ reciprocal covariance functions were calculated, and estimates of individual arrays’ auto-covariance functions, by changing the quantization interval on the time scale. The covariance model proposed by the authors for the analysis of the dynamical parameters of the centering–leveling devices can be used to investigate the dynamic characteristics of the angular comparators containing the said devices and at the same time to determine the ways of improving the precision of these angular comparators. The calculations were carried out using the special computer program developed by the authors of the Matlab7 Operator Package (The MathWorks, Inc. R2012a 7.14.0.739 License Number 699298).
Descriptions of polishing process, using technologies, materials of optical details are given in this article. High quality requirements are raising for optical details – smoothness of surface, ...non-existence of effects, form deflections, which are obtainable in polishing process. Results of modelling and experimental data are given in published scientist researches; various cutting rates were used in polishing process. Experiment plan for polishing plane details from optical glass BK7 with different cutting rates is given in this article. Multicriterion optimization in polishing process using for high quality optical details.
Straipsnyje aprašomas optinių detalių poliravimo procesas, naudojamosios technologijos ir medžiagos. Optinėms detalėms keliami aukšti tikslumo reikalavimai – paviršiaus glotnumo, defektų nebuvimo, formos nuokrypių ir kt., jie gaunami poliravimo proceso metu. Mokslininkų paskelbtuose tyrimuose pateikiami modeliavimo rezultatai, gauti eksperimentų metu, tirtos įvairios apdirbamosios medžiagos, jų paviršiaus kokybė, poliruota įvairiais pjovimo režimais. Šiame straipsnyje aprašomas eksperimento planas, skirtas plokščioms detalėms iš optinio stiklo BK7 poliruoti, kai varijuojama keliais apdirbimo režimais. Siekiama gauti aukštą gaminių kokybę daugiakriterio optimizavimo būdu.
Solar cells are one of the most popular renewable energy generation technologies, because they are reliable, low operating and maintenance costs, to conclude without any moving parts and is a ...boundless source of energy. In any solar cell can avoid mechanical vibrations, which may produce the solar cell glass, damage to the inner structure. In order to determine the influence of mechanical vibrations of the solar cell structure was carried out theoretical and experimental modal analysis. The study found dangerous solar cell frequencies and their deformation and optimize the method of attachment which provides a better solar cell stability.
Saulės elementai – vieni populiariausių atsinaujinančių energijos gavybos technologijų, nes jie patikimi, jų mažos eksploatavimo ir priežiūros išlaidos, šie elementai sudaryti be jokių judančių dalių ir yra beribis energijos šaltinis. Bet saulės elementas neišvengia mechaninių virpesių, kurie gali įskelti saulės elemento stiklą, pažeisti vidinę konstrukciją. Siekiant nustatyti mechaninių virpesių įtaką saulės elemento konstrukcijai, buvo atliktos teorinės ir eksperimentinės modalinės analizės. Tyrime buvo rasti pavojingi saulės elemento dažniai ir jų deformacijos, rastas optimalus tvirtinimo būdas, kuris suteikia geresnį saulės elemento stabilumą.
Paper presents dynamic field test and analysis results of a three span railway steel continuous truss bridge over river Neris in Jonava. Bridge was originally constructed in 1914. In the period of ...the World War II and afterwards the bridge was many time destroyed by German and Soviet armies. In 1948 the new railway bridge was constructed. Object of the present paper is to evaluate dynamic behaviour of the railway bridge after 67 years in service. Experimental dynamic analysis was divided into resonance-vibration, forced-vibration and free vibration studies. Resonance-vibrations of the bridge were excited by separate actions of shock loading and standard locomotive 2M62. Forced-vibrations were measured under the action of locomotive 2M62. Additionally, free vibration tests under passage of freight and passenger trains have been carried out. Structural dynamic response of the bridge was analysed using Brüel & Kjær LAN XI dynamic test system and software. As a result, main dynamic parameters of the bridge were obtained. The main results include: mode shapes, frequencies of natural and forced vibrations, damping ratios, maximum amplitudes of accelerations, dynamic displacements. The obtained values were compared to the requirements of different design codes. Based on the achieved results concluding remarks and recommendations regarding the condition of the bridge after long-term period in service were presented.
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