Wyniki 1-5 spośród 5 dla zapytania: authorDesc:"Alena BRUSILOVÁ"


  In this work, the influence of the processing conditions on the microstructure and abrasive wear behaviour of composite laser clad coatings with Ni based matrix reinforced with 50 % WC particles is analyzed. Composite powder was applied in the form of coatings onto a mild steel substrate (Fe‐0.17 % C) by different laser powers and cladding speeds. The microstructure of the coatings was analyzed by scanning electron microscopy (SEM). Tribological properties of coatings were evaluated by pin‐on‐disc wear test. It appeared that the hardness of the matrix of composite coatings decreases with increasing cladding speed. However, wear resistance of composite coatings with decreasing hardness of Ni based matrix increases. Significantly enhanced wear resistance of WC composite coatings in comparison with Ni based coatings is attributed to the hard phase structures in composite coatings. Keywords: NiCrBSi powder, W, composite laser clad; wear resistance ODPORNOŚĆ NA ŚCIERANIE LASEROWO WYTWARZANYCH POWŁOK KOMPOZYTOWYCH NA BAZIE Ni WZMOCNIONYCH CZĄSTECZKAMI WĘGLIKA WOLFRAMU W niniejszej pracy przeanalizowano wpływ warunków obróbki na mikrostrukturę i właściwości ścierne napawanych laserowo kompozytowych powłok na osnowie Ni wzmocnionych 5 % cząsteczek węglika wolframu. Proszek kompozytowy był nakładany w formie powłoki na podłoże ze stali miękkiej (Fe‐0,17 % C) przy różnej mocy lasera i prędkości powlekania. Mikrostruktura powłok była badana za pomocą elektronowej mikroskopii skaningowej (SEM), natomiast właściwości tribologiczne metodą tarcza‐trzpień (ang. pin on disc). Stwierdzono, że twardość osnowy powłok kompozytowych maleje ze wzrostem prędkości powlekania, natomiast ich odporność na ścieranie rośnie ze spadkiem twardości osnowy na bazie Ni. Znacząco większą odporność na ścieranie powłok kompozytowych z węglikami wolframu w porównaniu z powłokami na bazie Ni przypisuje się strukturze fazy twardej powłoki kompozyto[...]

Comparison of simulated and experimental weld line movement of deep drawn parts made of BH220 and DP600 steel sheets DOI:10.15199/24.2017.8.26

  Introduction. Tailor welded blanks (TWBs) were deve􀀐 loped mainly for automotive applications. They are semi-fi􀀐 nished parts that usually consist of materials with different stress strain properties, but they can be made of materials with different thicknesses or coatings too [1-3]. Several grades of steel such as deep drawing steels, interstitial free steels, high strength low alloy steels, bake hardening steels, dual phase steels, complex phase steels, TRIP steels, mar􀀐 tensitic steels and TWIP steels are used in TWBs design. Using of various steels in TWBs design enables to achieve the different stress strain characteristic in certain sections of the drawn parts [4, 5]. The individual steel sheets used in TWBs are joined by welding with concentrated energy sources such as laser or plasma welding. Minimal deformation of TWBs because of small heat affected zones together with high welding speed and large flexibility are the main advantages of these we􀀐 lding methods. The ability of welded joints to support of load are controlled by some basic mechanical testing me􀀐 thods such as tensile test, Erichsen deep drawing test, three point bending test, etc. [6-8]. Apart from the weldability, the formability is the most important property of TWBs. The formability is influenced by different stress and strain properties of particular sheets from the view of planar and normal anisotropy. The signi􀀐 ficant differences of these properties give higher require􀀐 ment on formability evaluation and measuring of stress strain parameters. These are used for boundary conditions at simulation of drawing processes and they are defined by proof strength, tensile strength, ductility, planar anisotropy coefficient, true stress versus true strain curve, deformation strengthening coefficient and forming limit diagram [7-9]. Experiment. The aim of the work was to compare si􀀐 mula[...]

Technological properties of materials for tailor welded blanks DOI:10.15199/24.2017.8.19

  Introduction. Tailor welded blanks (TWBs) have been found the most application in automotive industry. The sheets used in TWBs are often made of materials with different stress-strain characteristics [1]. Many material combinations have been used in design of TWBs such as conventional deep-drawing steels of grades DC01 to DC05 with conventional high strength steels IF-HS, HSLA, BH and IS or ultra-high strength steels DP, CP, TRIP, MART and TWIP [2]. The sheets have been joined by concentrated power source by laser or plasma welding process. The main function of welded joints is transfer of forming forces dur ing drawing and bending processes [3]. This ability can be verified by the static tensile test according to ISO 6892-1, by Erichsen cupping test according to ISO 20482:2014-05 and by three-point bending [4]. Except experimental methods, the simulation software for example AutoForm, Pam-Stamp and Dynaform have been used at the evaluation of TWBs forming with different stress-strain characteristics. The softwares are equipped with stress-strain characteristics of majority materials used in TWBs design and they determine the border conditions for forming process simulations. It´s very important to ob tain topical parameters of technological properties, to edit them manually into software and to get more accurate re sults comparable with real state [5, 6]. Among them belong proof strength, tensile strength, percentage elongation after fracture and percentage reduction of area (ISO 6892-1), coefficients of normal and planar anisotropy (ISO 10113), work hardening coefficient (ISO 10275), flow curve and forming limit diagram. The considerable differences betwe en measured material parameters and parameters declared by t[...]

Tubes bending by tool from abrasion resistance cast iron DOI:10.15199/24.2018.8.6

  Introduction. The rods, profiles and tubes bending is specific technology which is characteristics by complicated combination of stress states [1, 2] characterised by a spatial 3D bending in formed material [3, 4]. An extremely small bending radius of tubes results in the danger of formed material overstrength in outer bending location [5], a large wall thickness increasing in inner bending location and undesirable ovality creating [6]. These all facts, besides required geometry, are affected also by suitable construction and material of forming tool. The closed area of heat exchanger cramped because it hasn’t been assumed any another change. It was necessary to increase size of heat transfer area by means of exchanger tube bodies number increasing because of efficiency improving. This enlarging has been possible to obtain by bending radius minimization of anguineform tube exchanger system. Required tube bending radius has been possible to gain by choice of suitable tube material and forming tool adjustment by a bending rail change. These changes affected to a coefficient friction during bending process. Problem characteristics. The heat exchanger is compound of casing and anguineformly arranged tube system according to Fig. 1. For the area enlarging of heat-delivery surface water heater, the anguine seamless tubes with changed bending radius have been designed in such a way that it has been possible to give more pieces of anguine tubes into the original heater area. The bending radius up to the neutral axis of anguine tubes has been reduced to R = 40 mm. The designed heavy-wall seamless tubes in sizes 38 × 5 mm made of material 1.0345 (P235GH) with chemical composition according to table 1. It is a carbon plain heat resistant steel suitable for pressure vessels and Fig. 1. The scheme of re-designed heat exchanger internal arrangement Rys. 1. Schemat budowy wewnętrznych układów przeprojektowanego wymiennika ciepła T[...]

Process parameters optimization and their influence on friction rate during deep drawing DOI:10.15199/24.2018.9.3

  Introduction. The forming tools construction and technological processes design are based many times on the empirical evidences. However, the numerical simulations progress allows in high accurary rate the objective determination of forming, stresses and strains distribution and wall thickness of drawn part during single stages of techmological processes and number of attempts decreasing at production technology design [1, 2]. The numerical simulation and experimental adjusting of square box deep drawing provide many information about strain characteristics of process. The forming of two flat sides and their transition on the corner of an axially symmetric drawn cup is possible to analyse as three independet remoulded areas [3, 4]. The drawn cup corner with intensive thickness increasing of material is a problem area especially during deep drawing of galvanized highstrength steels [5]. This effect influences on friction rate under a blankholder and on drawing edge, surface quality and galvanized layer compactibility of drawn cup in exposed sites. The analyzed model example is possible to generalize for deep drawing of ground complex shaped drawn cups. The aim was to determine through simulation and experiments of square box deep drawing from sheet metals of highstrength steel TRIP: - appropriate drawing gap geometry of experimental tool, - stress-strain material characteristics of blank used for experiments for simulation enter data optimization, - non-st[...]

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