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2.
Matematični model ocene negotovosti pri merjenju ravnosti
Andrej Gusel, 2009, dissertation

Abstract: Meritve ravnosti predstavljajo sredstvo za vrednotenje ravnosti merilnih plošč in ostalih površin, ki služijo kot osnova pri meritvah lege in oblike. Kljub poznavanju postopkov, metod in merilne opreme za merjenje ravnosti ter kljub vedno novim metodam, ki poskušajo poenostaviti postopek, se vedno pojavljajo isti problemi. En glavnih problemov so vplivni faktorji, ki učinkujejo na meritev. Te vplivne faktorje, še bolj pa njihove učinke na meritev, moramo poznati in biti sposobni ovrednotiti, saj predstavljajo osnovo za določanje negotovosti meritve ravnosti. Vplivni faktorji so na splošno sicer znani, manj znani pa so njihovi vplivi na meritev, kar vpliva na odločitev, katere upoštevati in kako, katere pa lahko zanemarimo oziroma preprečimo. Prej ali slej se soočimo tudi s pomanjkljivostmi obstoječih metod. Večino meritev ravnosti izvajamo po metodi Union Jack, ki poleg vrste prednosti prinaša tudi nekaj pomanjkljivosti. Glavna pomanjkljivost je, da mreža že v osnovi bolj slabo pokrije obravnavano površino. Bolj groba mreža res pohitri postopek merjenja, vendar pa se zato pokritost površine še dodatno zmanjša, s tem pa se nam lahko iz obravnave izmuzne katero od odstopanj površine, to pa seveda vpliva na rezultat in negotovost. Zdi se, da bi za bolj drobne nepravilnosti potrebovali bolj gosto mrežo, za večja odstopanja pa bi zadoščala bolj groba mreža. Če torej glede na obliko površine določamo gostoto merilne mreže, gostota merilne mreže pa spet pogojuje stopnjo pokritosti površine, moramo najti odgovor na vprašanje, ki sledi: kako sta povezani oblika površine in negotovost meritve? Ali bi bilo res možno (in smiselno), da bi za različne oblike površin vnaprej definirali različne merilne mreže? Pri odgovoru na te izzive si pomagamo z metodo Monte Carlo. Model meritve služi za osnovo algoritma, s katerim je mogoče preko serije simulacij določiti negotovost meritve. Rezultati za različne merilne mreže, prilagojene obliki površine, kažejo presenetljive izsledke.
Keywords: model negotovosti ravnosti, simulacija ravnosti Monte Carlo, simulacija merilne plošče
Published: 19.05.2009; Views: 3135; Downloads: 177
.pdf Full text (4,80 MB)

3.
Measurement uncertainty in calibration of measurement surface plates flatness
Andrej Gusel, Bojan Ačko, Vedran Mudronja, 2009, original scientific article

Abstract: Ravno merilno površino, kot je to na primer merilna plošča, lahko smatramo kot izhodišče za izvajanje večine meritev oblike in lege merjenih objektov. Da bi merilne plošče v ta namen zadovoljivo uporabljali, moramo najprej zagotoviti, da so res ravne in primerne za meritve. Ravnost merilne ploskve ugotavljamo posredno, tako da najprej določimo premost posameznih linij, ki so sestavni del merilne mreže. Te linije so še dodatno razdeljene na merilne korake, ki so prirejeni meram merilne opreme. Premost merilne linije izračunamo z merjenjem nagiba posameznega merilnega položaja za vsako linijo posebej, neravnost celotne površine pa tako, da rezultate po linijah povežemo v celoto. Osnove, postopki in merilne naprave za izvajanje meritev so torej znani, neznanka pa ostaja negotovost tovrstne kalibracije merilne površine. Meritev brez ustrezno izražene negotovosti ne pomeni ničesar, zato moramo zagotoviti, da bomo lahko negotovost določili. Pričujoči članek predstavlja nov pristop določanja merilne negotovosti pri merjenju ravnosti, ki temelji na uporabi metode Monte Carlo. Pri tem celoten merilni sistem razstavimo na posamezne komponente ter ocenimo njihovo veličino in vplive le teh, meritve pa simuliramo. Zanima nas tudi vpliv parametrov merilne mreže na meritev.
Keywords: production measurements, length measurements, measuring uncertainty, calibration, uncertainty measurement, flatness measurement
Published: 31.05.2012; Views: 1137; Downloads: 22
URL Link to full text

4.
ANALIZA NEČISTOČ KOVINSKIH ULITKOV
Aleksandra Trokšar, 2016, undergraduate thesis

Abstract: Naloga vključuje raziskave analiz nečistoč kovinskih ulitkov
Keywords: ultrazvočno pranje, površinska obdelava ulitkov, spiranje ulitkov pod tlakom
Published: 14.10.2016; Views: 726; Downloads: 58
.pdf Full text (2,61 MB)

5.
Lastnosti zlitine Cu-Cr-Zr izdelane po nekonvencionalnem postopku : [diplomsko delo]
Leo Gusel, 1991, undergraduate thesis

Keywords: bakrove zlitine, kontinuirano litje
Published: 26.07.2007; Views: 1462; Downloads: 0

6.
ANALIZA IN IZBOLJŠANJE IZSEKOVANJA ODPRTIN NA VOTLIH PROFILIH IZ ALUMINIJEVIH ZLITIN
Danijel Duronjič, 2010, undergraduate thesis

Abstract: Diplomsko delo pred vami analizira postopek izsekovanja odprtin na votlih profilih iz aluminijevih zlitin. Na podlagi te analize je v nadaljevanju dela podanih nekaj predlogov, kako omejiti izmet. V začetku diplomskega dela je predstavljeno izsekovanje in konkreten postopek, ki ga obravnava to delo. Po analizi izsekovanja so podani podatki o izmetu in o mehanskih lastnostih materiala profilov. Za konec je navedena povezava med mehanskimi lastnosti materiala in izmetom, ter predlaganih nekaj sprememb izsekovalnega stroja in orodja, ki bi pripomogle k zmanjšanju izmeta. Delo zaključuje sklep, ki pravi, da dobra konstrukcija stroja ni dovolj, pomembno je tudi redno vzdrževanje stroja.
Keywords: izsekovanje, rezilna orodja, pestič, matrica, votel profil iz aluminijeve zlitine, sila rezanja
Published: 02.11.2010; Views: 1703; Downloads: 126
.pdf Full text (2,17 MB)

7.
Modeling of impact toughness of cold formed material by genetic programming
Leo Gusel, Miran Brezočnik, 2006, original scientific article

Abstract: In the paper, an approach completely different from the conventional methods for determination of accurate models for the change of properties of cold formed material, is presented. This approach is genetic programming (GP) method which is based on imitation of natural evolution of living organisms. The main characteristic of GP is its non-deterministic way of computing. No assumptions about the form and size of expressions were made in advance, but they were left to the self organization and intelligence of evolutionary process. First, copper alloy rods were cold drawn under different conditions and then impact toughness of cold drawn specimens was determined by Charpy tests. The values of independent variables (effective strain, coefficient of friction) influence the value of the dependent variable, impact toughness. On the basis of training data, different prediction models for impact toughness were developed by GP. Only the best models, gained by genetic programming were presented in the paper. Accuracy of the best models was proved with the testing data set. The comparison between deviation of genetic model results and regression model results concerning the experimental results has showed that genetic models are more precise and more varied then regression models.
Keywords: metal forming, genetic programming, evolutionary computing, impact toughness, copper alloy, modelling
Published: 30.05.2012; Views: 1344; Downloads: 67
URL Link to full text

8.
Yield strength modelling of formed material using evolutionary computational method
Leo Gusel, Rebeka Rudolf, 2009, original scientific article

Abstract: In this paper we propose an evolutionary computation approach for the modelling of yield strength in formed material. One of the most general evolutionary computation methods is genetic programming, which was used in our research. Genetic programming is an automated method for creating a working computer program from a problemćs high-level statement. Genetic programming does this by genetically breeding a population of computer programs using the principles of Darwinianćs natural selection and biologically inspired operations. During our research, material was cold formed by drawing using different process parameters and then determining yield strengths (dependent variable) of the specimens. On the basis of a training data set, various different genetic models for yield strength distribution were developed during simulated evolution. The accuracies of the best models were proved by a testing data set and comparing between the genetic and regression models. The research showed that very accurate genetic models can be developed by the proposed approach.
Keywords: metal forming, yield strength, genetic programming, modelling
Published: 31.05.2012; Views: 1274; Downloads: 23
URL Link to full text

9.
Dependence of material characteristics on lubrication in bulk forming process
Leo Gusel, 2009, published scientific conference contribution

Abstract: In the paper the influence of coefficient of friction (lubricant) on different properties of cold formed material has been examined. Tensile tests, hardness measurements and electrical conductivity measurements were performed.In the frame of the experimental work the process of cold forward extrusion of a cylinder made from copper alloy was investigated. The specimens were extruded at four different lubricants coefficients of friction. The results have shown that use of different lubricators with different coefficients of friction can have effects on the material properties during and after cold forming process.
Keywords: lubrication, cold forming, copper alloy, mechanical properties
Published: 31.05.2012; Views: 878; Downloads: 9
URL Link to full text

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