Wyniki 1-3 spośród 3 dla zapytania: authorDesc:"Marcela POKUSOVÁ"

Deep drawability of tailor welded blank of dual phase steel DP 600 affected by laser weld DOI:10.15199/24.2019.8.3

  Introduction. The tailor welded blanks (TWBs) are in large extent used for the parts producing of car body construction (Fig. 1) [1]. TWBs are consisting of materials with different stress-strain characteristics or different thickness. The aim is to achieve required stiffness, strength, low weight but also an ability to energy deformation absorb during crash. The dual phase steels DP-HCT along with another steels (DP, BH, TRIP) are very often used as materials for TWBs. The structure changes in a heat-affected zone (HAZ) affect negatively the material flow properties and can be the cracks formation origin at work pieces producing. The joining of individual parts is realised by various welding processes (Fig. 2) [2]. The most frequent method of a weld formation is a laser beam welding with the narrowest heat-affected zone. The appropriate choice of technological welding conditions allows to keep the material flow properties of a weld what closest to basic material [3]. Eperiment conditions. The following conditions for determination of a laser weld effect on the strain characteristics and a deep drawability of a laser weld of the steel DP-HCT 600 with a yield point Rp0,2=330-460 MPa, a tensile strength Rm=580-670 MPa and a ductility A=22% were chosen: - The effect of welding speed was observed on the samples of set A, B and C. The samples of group A were welded at a speed vA = 20 mm s-1, a group B at vB = 30 mm s-1 and a group C at vC = 40 mm s-1 and an output power 4 kW under the p rotection of argon gas. - The effect of protective gas composition on a deep drawability of the weld was observed on the samples of set D and E. The samples of group D were welded under protection of helium gas and the samples of group E under protection of argon gas. The output power was 3 kW, the welding speed vA = 20 mm s-1. The weld joint - the weld bead. For the experiments, the weld of TWB was replaced by remelting of base material by la[...]

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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