Wyniki wyszukiwania - BazTech

1

Investigation on the formation of central damage in cross wedge rolling of GH4169 alloy

Li Junling, Li Zheng, Wang Baoyu, Sun Chaoyang, Chen Ping, Fang Shuang

Archives of Civil and Mechanical Engineering

|

2023

|

Vol. 23, no. 3

art. no. e204, 2023

EN

Cross wedge rolling process provides a new way with short production chain and precise control for high-performance blade preforming used in aeroengine, but the issue of central damage needs to be paid attention and investigated. Therefore, this paper aims to understand the formation mechanism of central damage on CWR of GH4169 alloy. The uniaxial hot tensile test and CWR experiments were carried out to explore the high-temperature deformation behavior of GH4169 alloy, as well as the central damage of GH4169 alloy CWR process. Moreover, the finite element model was established and used to analyze the evolution of stress and strain at different position. The results showed that central part of the workpiece is in the state of higher stress triaxiality η, which is easy to cause damage. And the micro-holes in the center of workpiece mainly nucleated around the detached NbC carbide. Meanwhile, the first principal stress and the maximum shear stress are the dominant factors which affect the central damage. Therefore, a novel damage criterion suitable for CWR of GH4169 alloy was developed with considering the effect of stress triaxiality η and the sensitivities of deformation temperature and strain rate on the central damage evolution. In addition, initial forming temperature T0 is the most important factor affecting the central damage, and the maximum area reduction and rolling speed n are related to the initial deformation temperature T0. And in order to inhibit the damage, the initial forming temperature should be controlled below 1020℃, and the area reduction and rolling speed should not be higher than 55% and 10r/min, respectively.

2

Microstructure and mechanical properties of TC4 titanium alloy hollow shaft formed by cross wedge rolling

Feng Pengni, Yang Cuiping, Wang Baoyu, Li Junling, Liu Ronge

Archives of Civil and Mechanical Engineering

|

2021

|

Vol. 21, no. 3

737--751

EN

Production of hollow shafts satisfying mechanical performance requirements can well meet the needs of lightweight. The purpose of this work is to investigate the effect of cross wedge rolling (CWR) process parameters on microstructure and mechanical properties of TC4 titanium alloy hollow shafts, so as to ensure the feasibility of forming TC4 titanium alloy hollow shaft by CWR. The results demonstrate that the initial deformation temperature, area reduction, wall thickness, and mandrel have significant effects on the volume fraction of primary alpha phase (fα_p), morphology of alpha phase and interface of alpha/beta phase. The decrease of the fα_p, the increase of fine secondary alpha phase content and the increase of the number of alpha/beta phase interfaces can increase the strength of TC4 alloy hollow shafts, but decrease the elongation. When the initial deformation temperature is 950 °C, the contribution of the thick secondary alpha phase is similar to that of the primary alpha phase, resulting in the decrease of strength. The strength is further improved owing to the grain refinement with the increase of area reduction to 60%. The strength decreases as the wall thickness increases owing to the non-uniform microstructure distribution, which can be improved by increasing the area reduction appropriately. The comprehensive mechanical properties of the workpiece rolled with a mandrel are evidently higher than that rolled without a mandrel. Under any forming condition in this work, every fracture surface is covered with abundant dimples and voids, showing good ductile fracture characteristics.

3

Investigation of the microstructure evolution and mechanical properties of a TC6 alloy blade preform produced by cross wedge rolling

Li Junling, Wang Baoyu, Fang Shuang, Chen Ping

Archives of Civil and Mechanical Engineering

|

2020

|

Vol. 20, no. 3

91--101

EN

Cross wedge rolling (CWR) is one of the most effective plastic deformation methods utilized for the production of shaft parts or non-shaft preforms with refined grains and improved mechanical properties. The main goal of this work was to study the influence of CWR process parameters on the microstructure evolution and mechanical properties of a TC6 alloy and determine the suitable process parameters for a TC6 alloy blade preform fabricated with CWR. The results showed that the volume fraction of the equiaxed α phase (fα_e) decreased from ~ 0.38 to ~ 0.04 by increasing the initial deformation temperature, and the elongation (El) also decreased from ~ 19.6 to ~ 11.8% because dislocation slip first started in the equiaxed grains and then dispersed into the adjacent grains. Thus, additional equiaxed grains contributed to an increased plasticity. Moreover, with an increasing area reduction, the value of fα_e increased from ~ 0.14 to ~ 0.31, and the grain refinement and microstructure uniformity also increased. In addition, the El was significantly reduced by over 50%, but the ultimate tensile strength (UTS) and yield strength (YS) increased under WC (water cooling) conditions due to the precipitation of the acicular secondary α phase and pinning effect of the small equiaxed α phase. Based on the determined suitable parameters, the TC6 alloy blade preform was successfully manufactured by CWR, the microstructure was evenly distributed, and the UTS, YS and El were 1120.1 MPa, 1020.9 MPa and 15.2%, respectively, which meet the current technical requirements.

4

Analiza procesu walcowania klinowego odkuwki wałka stopniowanego

Pater Z., Tomczak J., Bulzak T.

Mechanik

|

2013

|

R. 86, nr 11

966--970

PL

Przedstawiono wyniki analizy dwóch procesów walcowania klinowego wałka stopniowanego, mającego stopnie skrajne o średnicy mniejszej od średnicy stopnia środkowego (kołnierza). W jednym z nich wykorzystano typowe narzędzia w kształcie płaskich klinów, w drugim zaś do kształtowania zastosowano innowacyjne narzędzia powstałe poprzez śrubowe nawinięcie klinów na walec. W analizie obu procesów wykorzystano metodę elementów skończonych. W trakcie symulacji potwierdzono możliwość kształtowania osiowosymetrycznych odkuwek wielostopniowych wałków w procesie walcowania skośnego. W rezultacie możliwe jest zwiększenie wydajności wytwarzania półfabrykatów oraz ograniczenie zużycia materiałów. W trakcie obliczeń wyznaczono również rozkłady intensywności odkształcenia, temperatury oraz przebiegi parametrów siłowych procesów, na podstawie których dokonano oceny efektywności opracowanej metody wytwarzania. Przedstawiono także wady i zalety obu przypadków kształtowania.

EN

Presented are the results of comparison of the two wedge rolling operations to produce stepped shaft forging with the end steps smaller than the middle step (collar) diameter. In the first case typical tools in the form of flat wedges were used, whereas for the other case innovative tools generated by means of wedges helically wound on the roll were applied. The finite element method was applied to provide for comparison of the two processes. The simulation has positively proved that the skew rolling method can be used to produce the axially symmetric multiple stepped shafts. It is thus practicable to increase outputs of the half finished products and to reduce materials consumption. Revealed in the work were the deflection and temperature distribution outlines and the process strain changes for estimation of the production process effectiveness. Also discussed are benefits and drawbacks of both production methods.