Wyniki 1-4 spośród 4 dla zapytania: authorDesc:"Zuzana GÁBRIŠOVÁ"

Weld line displacement during deep drawing of tailor welded blanks consisting of different sheet materials or sheet thicknesses DOI:10.15199/24.2017.8.25

  Introduction. Reduction of both vehicle weight and fuel consumption has been a constant demand in automotive in dustry without compromising other attributes such as safety, performance, recyclability and manufacturing costs. A prom ising opportunity to meet these requirements is using of tai lor welded blanks (TWBs) consisting of high strength steels. A car body manufactured using TWBs and high strength steels can achieve a 25% weight reduction. TWBs are blanks where multiple sheets of material are welded together prior to the forming process. The differences in the material within a TWB can be in the thickness, grade or coating of the mate rial [1-3]. Important advantage of using TWBs is to reduce the amount of scrap due to the odd shapes of the blanks. Smaller pieces of metals can be nested easily for better mate rial utilization. Another main advantage of using TWBs is specific characteristics at distinct parts of the TWB to reduce the material weight and cost. Certain sections of the TWB can be made from a thicker or high strength material to in crease stiffness while having a thinner material at other sec tions. The sections of the TWB can be made of coated steel to increase the resistance to corrosion while having bare steel at other sections too [3-5]. An example of using TWB consisting of sheets with different thicknesses is the reinforcement of longitudinal beam in car body structure. The reinforcement is produced by deep drawing process and three steps of its manufactur ing are documented in fig. 1 to 3. The TWB for symmetric deep drawing is in fig. 1. It consists of sheets with different thicknesses and different materials which were laser weld ed before deep drawing process. Two drawn part are deep drawn in one tool. Both right and left deep drawn part of reinforcements are in fig. 2. The position of right reinforce[...]

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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