Razlike u sazrijevanju dviju vrsta djeteline i utjecaj desikacije prije žetve

Experiments were focused on differences in the ripening of crimson clover (Trifolium incarnatum L.) and red clover (Trifolium pratense L.) and on the influence of the pre-har vest treatment with desiccants. The drying of leaves, stems and heads during ripening, regrowing, breakdown of heads and yield parameters including seed were compared. The crimson clover exhibited the natural drying of leaves, stems and heads faster than the red clover. In crimson clover, the drying of leaves, stems and heads before the har vest was 80 - 100%, 50– 95%, and 100 %, respectively. In red clover, the drying of leaves, stems and heads was 25 - 84 %, 20–72% and 45–99%, respectively. There were also dif ferences in the regrowing and in the breakdown of heads. In the pre-harvest treatments of crimson clover and red clover, the effect of diquat was compared with the efficiency of other herbicide substances (pyraflufen-ethyl, carfentrazone-ethyl and pelargonic acid) and with the efficiency of a high dose of DAM fertilizer (liquid fertilizer, urea-ammonium nitrate). Compared with diquat, the drying was slower with the other active substances. Significant effects of tested active substances on yield, WTS (weight of thousand seeds) and germination were not recorded.Cilj ovog istraživanja bio je utvrditi razlike između sazrijevanja djeteline inkarnatke (Trifolium incarnatum L.) i crvene djeteline (Trifolium pratense L.) ovisno o primjeni desikanata prije žetve. Određena je razlika ovisno o vrsti tijekom više godina za odabrane pokazatelje: sušenje listova, stabljike i cvati tijekom sazrijevanja te ponovni porast usjeva, otvaranje plodova i prinos sjemena. Listovi, stabljike i cvati su se prirodno brže sušili kod djeteline inkarnatke negoli kod crvene djeteline. Kod inkarnatke je sušenje listova, stabljike i cvati je prije žetve iznosilo 80 – 100%, 50 – 95%, odnosno 100%, a kod crvene djeteline 25 – 84%, 20 – 72%, odnosno 45 – 99%. Također su utvrđene razlike u pokrovnosti usjeva nakon retrovegetacije i sušenje cvati. U predžetvenim tretmanima inkarnatke i crvene djeteline uspoređena je učinkovitost dikvata s učinkovitošću drugih herbicida (piraflufen-etil, karfentrazon-etil i pelargonska kiselina) te s učinkovitošću visoke doze DAM gnojiva (tekuće gnojivo, urea-amonij nitratom). U usporedbi s dikvatom, kod ostalih djelatnih tvari sušenje je bilo sporije. Nije utvrđen utjecaj korištenih djelatnih tvari na prinos, masu tisuću zrna i klijavost sjemena

Statistical evaluation of impact of technological factors on surface texture of WPC composites

The paper aims at evaluating the impact of technological parameters of a drilling process on the parameter of surface roughness Rz (maximum height of roughness profile) of wood-based material (WPC – Wood Plastic Composite). During drilling with tools 3.0, 5.0 and 7.0 mm in diameter, the spindle speed nc and feed rate f were changed. The evaluation of statistical significance was performed using the ANOVA mathematical tool (two-way with repetition). Using a simple conversion, it is possible to assess which of the set parameters affects the final surface quality, which serves as supporting information for the work of an engineer.Web of Science52332932

Study of surface roughness of machined polymer composite material

The aim of this paper is to evaluate the influence of selected cutting parameters (speed of rotation and feed rate) on the surface topography of drilled WPC material. Objective of the study is to establish dependence of the surface roughness of borehole walls (parameter —average maximum height) on the speed of rotation and feed rate of a drill bit. Technological parameters of experimental drilling were feed rate of 100–300 mm·min−1 and speed of rotation of 2000–6000 rpm.Web of Scienceart. no. 30351

On-line monitoring of technological process of material abrasive water jet cutting

Rad se bavi indirektnim načinima on-line praćenja tehnoloških postupaka rezanja u svrhu projektiranja on-line sustava praćenja primjenom tehnologije rezanja abrazivnim vodenim mlazom. Rezanjem abrazivnim vodenim mlazom javljaju se dva fenomena, a to su generirana površina i vibracije. U svrhu dokazivanja hipotetske pretpostavke ovisnosti kvalitete generirane površine o vibracijama, provedeni su eksperimenti s nehrđajućim čelikom AISI 304 s četiri različita podešavanja brzine prijelaza rezne glave. Vibracije materijala su se pratile pomoću dva odvojena akcelerometra PCB IMI 607 A11. Jedan je bio orijentiran na smjer rezanja, a drugi na pravac okomit na rezanje. Učestalost uzimanja uzorka bila je 30 kHz. Dobivena topografija materijala mjerena je optičkim profilometrom FRT MicroProf. Dobiveni su se rezultati proračunavali virtualnim alatom razvijenim u in LabView 8.5 u obliku analiza vibracija koje su se stalno međusobno uspoređivale. Pokazalo se da obadva fenomena ovise o zajedničkom tehnološkom razlogu, t.j. brzini prijelaza rezne glave. U isto vrijeme u radu se daje teoretski projekt on-line sustava praćenja i smjer budućeg istraživanja u ovom području.The paper deals with the indirect ways of on-line monitoring of technological processes of cutting. The objective of the study is a design of on-line monitoring system for the cutting technology through an abrasive water jet. In cutting by the abrasive water jet two parallel phenomena are formed. The phenomena are represented by generated surface and vibrations. For the purpose of proving of the hypothetical assumptions on dependence of generated surface quality on vibrations the experiments utilizing stainless steel AISI 304 were performed. The experiments were realized at four diverse settings of cutting head traverse speed. The material vibrations were collected by means of two independent accelerometers PCB IMI 607 A11. One of the accelerometers was oriented towards the cutting direction and the other in direction perpendicular to cutting. Sampling frequency was of 30 kHz. The generated topography of the material was measured by an optical profilometer FRT MicroProf. The collected data were evaluated by a virtual tool developed in LabView 8.5 in the form of vibration analyses being consequently mutually compared. Both phenomena proved to be dependent on common technological cause, i.e. on cutting head traverse speed. At the same time the study offers a theoretical design of the on-line monitoring system and of the future heading of the research in this field

Modelling of stress-strain states of nanomaterials created by multiple plastic deformation

The article deals with the identification of changes in the elasticity under compression exerted on the material during intensive plastic deformation using the ECAP method, and specifically on the material of the aluminium alloy EN AW 6060. The results of direct measurements were compared with the results of indirect measurements (i.e., with the results predicted and calculated). During each extrusion, the extrusion forces were measured directly depending on the lengths of the extruded sample, and then the mechanical work applied to the volume of the extruded sample as extrusion stress of the AlMgSi 0.5 material were evaluated. There are many methods available for evaluating the Young's modulus, but the proposed method is especially suitable for the material samples processed by the ECAP process. The research aimed mainly at evaluating the bulk modulus, and then the most accurate estimation of the Young's modulus after each extrusion. When Poisson's ratio and bulk module is known, the Young's modulus for samples of metallic materials can be evaluated using the relationships between elastic modules.Web of Science1687828782

Verfahren zur Bestimmung der Enthalpie und Entropie für das Laserschneiden

This paper is devoted to the mechanisms of laser cutting of material from the point of view of thermodynamics. Thanks to the special properties of a laser beam, lasers have proved to be a reliable tool for the industry. Scientific databases currently include many papers devoted to scientific and engineering research aimed at the development and application of the technology of lasers. Operating costs of a laser system are high when operated inefficiently, therefore efficient operation is quite desirable. High dimensional accuracy and mainly good final product quality must be achieved in order to ensure the effective laser cutting. Investigation into thermodynamic efficiencies and quality assessment of the final product in laser cutting is essential. We have created an analytical expression of the thermo-dynamic parameters of the cut. By expression of the entropy S, enthalpy H, heat flow density q and Gibbs' function of free energy G a complex image of thermo-dynamic conditions of the process was achieved. These are the basic thermodynamic parameters of the laser cutting of materials. All these factors under operating conditions had an impact on the surface quality of the cut, depth of the cut and also on the intensity of changes in the mechanical properties of the material, and last but not least, on productivity and competitiveness. This can be used both for predictions concerning the technology process, as well as for control of the process.Dieser Beitrag ist den Mechanismen des Laserschneidens von Material aus der Sicht der Thermodynamik gewidmet. Durch die speziellen Eigenschaften eines Laserstrahls haben sich Laser als zuverlässiges Werkzeug für die Industrie etabliert. Wissenschaftliche Datenbanken umfassen derzeit viele Beiträge, die der wissenschaftlichen und technischen Forschung an der Entwicklung und Anwendung der Lasertechnologie gewidmet sind. Die Betriebskosten eines Lasersystems sind bei nicht effizienter Betriebsweise hoch, so dass ein effizienter Betrieb wünschenswert ist. Hohe Maßgenauigkeit und vor allem gute Qualität des Endprodukts sind wichtig, um die Effektivität des Laserschneidens zu gewährleisten. Wir haben einen analytischen Ausdruck der thermodynamischen Parameter des Einschnitts abgeleitet. In den Ausdrücken der Entropie S, der Enthalpie H, der Wärmestromdichte q und der Gibbs-Funktion der freien Energie G konnte ein komplexes Bild der thermodynamischen Bedingungen des Verfahrens dargestellt werden. Dies sind damit die grundlegenden thermodynamischen Parameter der Laserschneiden von Materialien. Alle diese Faktoren haben unter Betriebsbedingungen eine Auswirkung auf die Oberflächengüte des Einschnitts, die Schnitttiefe und auch auf die Intensität der Veränderungen der mechanischen Eigenschaften des Materials sowie nicht zuletzt auch auf die Produktivität und Wettbewerbsfähigkeit. Dies kann sowohl für die Vorhersagen über den Technologieprozess als auch zur Steuerung des Prozesses verwendet werden.Web of Science475-646145

Ein neuer Ansatz zur Ermittlung der technologischen Parameter für Wasserstrahlschneiden

A method for the design of a technology for the abrasive waterjet cutting of materials is based on the determination of the constant of cuttability of materials using an abrasive waterjet Kawj according to four different versions. Version A, where three deformation parameters are measured on the test cut/sample, namely selected depth hx [mm], local roughness Rax [μm] at depth hx and local deviation of the cut trace from the normal plane Yretx at depth hx. Version B, where merely two deformation parameters are measured, namely the reference depth het [mm] and deviation of the cut trace from the normal plane Yretx [mm] or, according to version C, where one parameter is mearured, namely either the ultrasonic wave speed vLUZ [m · s–1] or Young's modulus Emat [MPa]; Kawj being calculated from relevant deformation parameters. The last option is version D, where the design of the whole technology is carried out by calculation of Kawj according to the Young's modulus Emat or according to the ultrasonic wave speed vLUZ of the cut material.Es wird ein Verfahren für den Entwurf einer Technologie für das Wasserstrahlschneiden von Materialien vorgestellt, das auf der Bestimmung der Konstanten der Schneidbarkeit von Materialien unter Verwendung eines abrasiven Wasserstrahls Kawj nach vier verschiedenen Ausführungen basiert: Version A, bei der drei Deformationsparameter auf dem Testschnitt gemessen werden, nämlich die ausgewählte Tiefe hx [mm], die lokale Rauheit Rax [μm] in der Tiefe hx und die lokale Abweichung der Schnittspur von der Normalebene Yretx in der Tiefe hx; Version B, bei der lediglich zwei Verformungsparameter gemessen werden, nämlich die Bezugstiefe het [mm] und die Abweichung der Schnittspur von der Normalebene Yretx [mm] oder Variante C, bei der nur ein Parameter gemessen wird, nämlich entweder die Ultraschall-Wellengeschwindigkeit vLUZ [m · s–1] oder der Elastizitätsmodul Emat [MPa] (Kawj wird hierbei aus den entsprechenden Deformationsparametern berechnet). Die letzte Möglichkeit ist die Version D, wobei das Design der gesamten Technologie durch die Berechnung von Kawj mittels des Elastizitätsmoduls Emat oder mittels der Ultraschall-Wellengeschwindigkeit vLUZ des geschnittenen Materials durchgeführt wird.Web of Science475-647146

Quantifying the Mechanical Properties of Materials and the Process of Elastic-Plastic Deformation under External Stress on Material

The paper solves the problem of the nonexistence of a new method for calculation of dynamics of stress-deformation states of deformation tool-material systems including the construction of stress-strain diagrams. The presented solution focuses on explaining the mechanical behavior of materials after cutting by abrasive waterjet technology (AWJ), especially from the point of view of generated surface topography. AWJ is a flexible tool accurately responding to the mechanical resistance of the material according to the accurately determined shape and roughness of machined surfaces. From the surface topography, it is possible to resolve the transition from ideally elastic to quasi-elastic and plastic stress-strain states. For detecting the surface structure, an optical profilometer was used. Based on the analysis of experimental measurements and the results of analytical studies, a mathematical-physical model was created and an exact method of acquiring the equivalents of mechanical parameters from the topography of surfaces generated by abrasive waterjet cutting and external stress in general was determined. The results of the new approach to the construction of stress-strain diagrams are presented. The calculated values agreed very well with those obtained by a certified laboratory VÚHŽ