Analiza faktora koji utječu na mikrootporno mjerenje

The micro-resistance measuring principle with specific forms of current distribution in the plated through-hole of printed circuit board (PCB) is analyzed in this paper. Special attention is paid to the following factors that influence the micro-resistance measuring: the hole diameter, the type of the measuring probe and the PCB thickness, and their two and three-factor interactions. The experiment with three repetition of measurement is carried out for which the dispersion analysis includes: the calculated values of the sum of the square of deviation, the mean of the square of deviation and a comparison between the calculated factors and the relevant factor given for five percent α-risk. The results of the dispersion analysis clearly indicate that the strongest factor that influences the micro-resistance measures is the PCB thickness. The overall conclusion is that the effect of each considered factor to the micro-resistance measures is expressive, but the effect of their mutual interactions is not significant in the measuring practice.U radu je analizirano načelo mikrootpornog mjerenja sa specifičnim oblikom raspodjele struje u metaliziranoj rupi tiskane ploče. Poseban je osvrt dan na faktore koji utječu na mikrootporno mjerenje – promjer rupe, tip mjerne sonde i debljinu tiskane ploče te na njihove dvo-faktorske i tro-faktorske interakcije (interakcije 1. i 2. reda). Proveden je pokus, uz tri ponavljanja mjerenja, za koji disperzivna analiza uključuje: računske vrijednosti suma kvadrata odstupanja i srednjih kvadrata odstupanja, te usporedbu vrijednosti izračunatih koeficijenata i referentnog tabličnog koeficijenta relevantnog za pet postotni α-rizik. Rezultati disperzivne analize jasno pokazuju da na vrijednosti izmjerenog mikrootpora najjače utječe debljina tiskane ploče. Zaključeno je da je djelovanje promatranih faktora na vrijednosti rezultata mikrootpora izraženo, dok je djelovanje njihovih međusobnih interakcija bez većeg značaja u mjeriteljskoj praksi

Razvijena procedura za strukturalnu dinamičku reanalizu

Structural dynamic modification techniques can be defined as methods by which dynamic behavior of a structure is improved by predicting the modified behavior brought about by adding modifications like those of lumped masses, rigid links, dampers, beams etc. or by variations in the configuration parameters of the structure itself. The methods of structural dynamic modification, especially those with their roots in finite element models, have often been described as reanalysis. The present paper deals with the problem of improving of dynamic characteristics some structures. New dynamic modification procedure is given as using distribution of potential and kinetic energy in every finite element is used for analysis. The main goal of dynamic modification is to increase natural frequencies and to increase the difference between them. Some information should be prepared, before setting up the FE model. The first pack of information includes referent peaces of information about the structure: size, material, and boundary conditions.U ovom radu je razvijena procedura za popravljanje dinamičkog ponašanja strojarskih konstrukcija u eksploataciji. U osnovi ove procedure je distribucija kinetičke i potencijalne energije na glavnim oblicima osciliranja konstrukcije. Inače, tehnika strukturne dinamičke modifikacije može se definirati kao skup metoda pomoću kojih se dinamičko ponašanje konstrukcije može popraviti procjenom modificiranog ponašanja dobivenog dodavanjem modifikacija kao na primjer koncentriranih masa, krutih veza, prigušenja, novih elemenata, i sl. ili promjenom konfiguracijskih parametara u samoj strukturi. Takve metode kod kojih je osnova metoda konačnih elemenata često se nazivaju metode reanalize. Jedan od osnovnih ciljeva u ovom radu, s obzirom na gore spomenuto, jest da se u metode reanalize ugradi još jedna s jasno predstavljenom procedurom korištenja

Developed procedure for dynamic reanalysis of structures

Structural dynamic modification techniques can be defined as methods by which dynamic behavior of a structure is improved by predicting the modified behavior brought about by adding modifications like those of lumped masses, rigid links, dampers, beams etc. or by variations in the configuration parameters of the structure itself. The methods of structural dynamic modification, especially those with their roots in finite element models, have often been described as reanalysis. The present paper deals with the problem of improving of dynamic characteristics some structures. New dynamic modification procedure is given as using distribution of potential and kinetic energy in every finite clement is used for analysis. The main goal of dynamic modification is to increase natural frequencies and to increase the difference between them. Some information should be prepared, before setting up the FE model. The first pack of information includes referent peaces of information about the structure: size, material, and boundary conditions

Optimization of thin-walled constructions in CAE system ANSYS

Znanstveni pristup rješavanju problema optimiranja sa stanovišta naprezanja i deformacije u konstrukciji provedeno je u ovom radu na primjeru teleskopske ruke. To je uglavnom zbog činjenice da, unatoč širokom spektru uporabe teleskopskih ruku, ne postoje općenito valjana, znanstveno dokazana i prezentirana teorijska načela za njihovo projektiranje. Sa stajališta mehanike, krak teleskopske ruke, kao predmet istraživanja može se svrstati u tankostjene konstrukcije. U stvari, riječ je o zatvorenom tankostjenom presjeku opterećenom kombinacijom savojnih i torzijskih momenata. Primjenjujući metodu konačnih elemenata (MKE) povezanu s CAE sustavom ANSYS moguće je projektirati optimalan oblik poprečnog presjeka poluge teleskopske ruke. Uspoređujući izračunate vrijednosti naprezanja i deformacije s vrijednostima dobivenim eksperimentalnim mjerenjima, moguće je procijeniti učinkovitost procesa optimiranja.Solving optimization problems from the standpoint of structural stresses and strains can be carried out scientifically on the example of telescopic jib. It is mainly due to the fact that despite a broad spectrum of the telescopic jib utilization there are no generally valid, scientifically proven and presented theoretical principles for their designing. From the viewpoint of the classification of mechanics, the arm of telescopic jib as a subject of study can be ranked among thin-walled constructions. In fact, it is a case of enclosed thin-walled bars stressed in operation by a combination of bending and torsion moments. Applying the Finite Element Method (FEM) in connection with the CAE system ANSYS, it is possible to design an optimum shape of the cross-section of the telescopic jib arm. Comparing the calculated values of stresses and deformations with the values obtained by experimental measuring, it is possible to evaluate the effectiveness of the optimization process

Strain Measurement on the Glass-Fiber Reinforced Plastic by Using Optical Measurement System

This paper deals with experimental determination of the mechanical properties of the fiber glass-reinforced plastic. Nine test samples were made from fiber-glass plastic, where three series with three samples each were with different thickness. All samples were of nominal length 250 mm with fibers of length 50 mm. The width of the specimens was 25 mm, and the thickness was 0,35 mm; 0,8 mm and 1,16 mm, respectively. The samples were subjected to tensile testing on a tensile machine in order to determine the mechanical properties. The force and longitudinal displacement (actuator displacement) were measured on the tensile testing machine, while with the optical measuring system, strains in the transverse direction (perpendicular to the tensioning direction) were measured. The results of the measurements on the tensile test machine, presented in the form of stress-displacement diagrams, are shown first within the same series (equal thickness of the test sample) and then the results are compared for different thicknesses of the test sample. By tensometric measurements, the change of the principal strains over time was determined. The engineering stress-strain curve for all nine test specimens was obtained using the optical measuring system and given in form of diagrams. It was found that the best tensile properties of all considered specimens have test specimens with the largest thickness, which also had glass fibers of knitted structure

Analiza faktora koji utječu na mikrootporno mjerenje

The micro-resistance measuring principle with specific forms of current distribution in the plated through-hole of printed circuit board (PCB) is analyzed in this paper. Special attention is paid to the following factors that influence the micro-resistance measuring: the hole diameter, the type of the measuring probe and the PCB thickness, and their two and three-factor interactions. The experiment with three repetition of measurement is carried out for which the dispersion analysis includes: the calculated values of the sum of the square of deviation, the mean of the square of deviation and a comparison between the calculated factors and the relevant factor given for five percent α-risk. The results of the dispersion analysis clearly indicate that the strongest factor that influences the micro-resistance measures is the PCB thickness. The overall conclusion is that the effect of each considered factor to the micro-resistance measures is expressive, but the effect of their mutual interactions is not significant in the measuring practice.U radu je analizirano načelo mikrootpornog mjerenja sa specifičnim oblikom raspodjele struje u metaliziranoj rupi tiskane ploče. Poseban je osvrt dan na faktore koji utječu na mikrootporno mjerenje – promjer rupe, tip mjerne sonde i debljinu tiskane ploče te na njihove dvo-faktorske i tro-faktorske interakcije (interakcije 1. i 2. reda). Proveden je pokus, uz tri ponavljanja mjerenja, za koji disperzivna analiza uključuje: računske vrijednosti suma kvadrata odstupanja i srednjih kvadrata odstupanja, te usporedbu vrijednosti izračunatih koeficijenata i referentnog tabličnog koeficijenta relevantnog za pet postotni α-rizik. Rezultati disperzivne analize jasno pokazuju da na vrijednosti izmjerenog mikrootpora najjače utječe debljina tiskane ploče. Zaključeno je da je djelovanje promatranih faktora na vrijednosti rezultata mikrootpora izraženo, dok je djelovanje njihovih međusobnih interakcija bez većeg značaja u mjeriteljskoj praksi