Rolled Aluminum Plate Research Articles

Formation mechanism and control strategy of M-shaped and W-shaped profile defects in hot rolling of aluminum plate

Good profile is one of the important control objectives in hot rolling of aluminum plate. However, M-shaped profile defect often appears for wide aluminum plate and W-shaped profile defect often appears for narrow aluminum plate. In order to reveal the formation mechanism of the two typical profile defects, the evaluation indexes of the M-shaped profile defect and W-shaped profile defect are proposed, and the roll-plate coupling deformation model and the roll thermal expansion model are established. The effects of rolling force, bending force and work roll thermal expansion on the profile are analyzed using these models. The results show that the rolling force and bending force has little effect on M-shaped profile defect, and the main reason for this problem is the uneven thermal expansion of work roll. Meanwhile, the W-shaped profile defect is produced under the combined action of the roll thermal expansion and large roll deflection, and the roll thermal expansion is the necessary condition for the formation of W-shaped profile defect. The greater the thermal crown of the roll, the smaller the rolling force and the greater the bending force, the more obvious the W-shaped profile defect. Based on the above conclusions, industrial tests were carried out. By increasing the cooling flow in the middle of the roll, the frequency of M-shaped profile defect decreases from 29.4% to 9.0%. Meanwhile, by increasing the positive shifting of CVC rolls, reducing the bending force, and decreasing the cooling flow of work roll at the edge of the plate, the frequency of W-shaped profile defect decreases from 42.1% to 14.1%. The profiles of the hot rolled aluminum plates are effectively improved by the developed control strategies.

Влияние горячей прокатки на анизотропию механических свойств алюминиевого сплава 6061

The influence of change of the hot rolling velocity modes on the mechanical properties of plates of the Al-Mg-Si system aluminum alloy 6061 was studied. The hot rolling was performed in two modes: at the smallest time and at the decreased rolling velocity. After hot rolling the samples were selected from the central part of the strips to determine the standard characteristics describing the mechanical properties of the material: ultimate tensile strength, yield strength and elongation. The obtained values revealed anisotropy of the strength properties. The strength properties in all ca­ses were maximal across the direction of rolling and minimal at an angle of 45º to it. The decrease of the rolling velocity led to higher hardening. The plastic properties of the plate were nearly isotropic. The orientation analysis based on the Electron Backscatter Diffraction (EBSD) showed that the clearly defined crystallographic texture was observed regardless the hot rolling mode. The main components of the texture were the orientations: two from {110}<112>, two from {112}<111>, and also (001)[010] and (110)[001]. By means of the software of the Oxford Instruments analysis system the Taylor factors for axial tension that represents the crystallographic characteristics of the relative strength of the material were calculated. The obtained values of the Taylor factors for the samples selected for the mechanical tests proved that anisotropy of the mechanical stress characteristics of the hot rolled aluminum plate mainly depend on the texture of the material, the indicator of which was a Taylor factor averaged according to the crystallographic

Crack path prediction in rolled aluminum plates with fracture toughness orthotropy and experimental validation

The paper presents a numerical procedure for the accurate calculation of crack paths in plane structures. The J-integral is used to determine crack tip loading quantities such as stress intensity factors or the energy release rate. Crack paths are predicted applying a modified maximum energy release rate approach accounting for the fracture toughness orthotropy in rolled plates of aluminum alloy Al-7075-T651 where the anisotropy of elastic constants is negligible. Experiments with CT-specimens are carried out to determine the fracture toughnesses in and perpendicular to the rolling direction. The numerically predicted crack paths for differently shaped specimens are in good agreement with those obtained from experiments.

Fiber Bragg Gratings Array for Structural Health Monitoring

Impact event monitoring and source location in some critical structures. The current work evaluated the feasibility and limitation of using fiber Bragg gratings (FBGs) for this purpose. Impact testing carried out on a cold rolled aluminum plate showed that impact event monitoring with the FBGs is feasible with the current intensity modulation interrogation method. Source location is successful at part of the impact location but not at the others. This phenomenon is caused by the complex wave propagation pattern on the plate so that differently oriented FBGs receive the signal from the same impact at different time.

Mechanical Properties of Aluminum Coatings Produced by Cold Spraying

A cold spraying process has been developed for dense and clean and tightly bonded coatings in contract with other established thermal spraying processes. The cold sprayed aluminum is particularly well suited for metallic coatings, such as electric conductor and corrosion resistance. However, the mechanical properties of aluminum coatings formed by the cold spraying have not always been clarified. Two kinds of free-standing aluminum specimens, which were formed by the cold spraying process and an atmospheric plasma spraying process, were machined from the thick coatings and were used for measuring the Young's modulus, Poisson's ratio and bending strength etc. in comparison with a rolled aluminum plate. The experimental results suggested that the crack length and crack density in aluminum coatings had an important effect on the mechanical properties. Namely, high bending strength and high Young's modulus of aluminum coatings could be obtained from the cold spraying process, because of the short crack length and the low crack density.

Orientation Coherence of Rolled and Annealed Aluminum Plate

Change of spatial orientation distributions is investigated in 95 % cold rolled aluminum plates annealed at 300 °C temperature for 10, 60, 180 and 300 seconds. Spatial distribution of orientations is measured by Electron Back Scattered Diffracting (EBSD) technique and spatial correlation of orientations is calculated using the two-point orientation coherence function (OCF). the orientational relationship around each main orientation can be found as a function of annealing time. Copper, S and brass components are initially distributed in mixture as thin bands but as annealing time increases to 300 seconds, S and brass components form distinct bands wider than 5 µm along sample normal direction and copper component exists in the brass bands.

Residual stress, stress relief, and inhomogeneity in aluminum plate

Through-thickness residual-stress profiles in rolled 7050-T74 aluminum plate were measured before and after stress relief by stretching (-T x51). Measurement required adapting the crack-compliance method to measure both in-plane stress components. Unexpected features in the profiles could be explained by through-thickness yield strength variations caused by crystallographic texture.

電子セラミックスのメタライジング技術開発 （第１報） アルミニウム溶射皮膜の微構造と機械的特性

The thermal spraying process is widely used to the metalizing of electronic ceramic for forming the electric conductor and/or the underlayer for bonding. However, mechanical properties of thermal sprayed coatings, which have an important effect on the adherent strength, have not always been clarified. Two kinds of free-standing aluminum specimens, which were formed by an atmospheric plasma spraying (APS) process and an electric arc spraying (EAS) process, were machined from the thick coatings and were used for experiments. The Young's modulus, Poisson's ratio, four-point bending strength and bending angle were measured at room temperature in comparison with a rolled aluminum plate. The experimental results suggested that the crack length and crack density in aluminum coatings, which were composed of pores and aluminum oxide, had an important effect on the mechanical properties. Namely, low strength, high ductility, high thermal conductivity and low electric resistivity could be obtained from the aluminum coatings sprayed by APS process, because of low pore volume and low oxide content.

Representing the Effect of Crystallographic Texture on the Anisotropic Performance Behavior of Rolled Aluminum Plate

Rolled aluminum alloys are known to be anisotropic due to their processing histories. This paper focuses on measuring and modeling monotonic and cyclic strength anisotropies as well as the associated anisotropy of the elastic/elastic-plastic transition of a commercially-available rolled plate product. Monotonic tension tests were conducted on specimens in the rolling plane of 25.4 mm thick AA 7075-T6 plate taken at various angles to the rolling direction (RD). Fully-reversed tension/compression cyclic experiments were also conducted. As expected, we found significant anisotropy in the back-extrapolated yield strength. We also found that the character of the elastic/elastic-plastic transition (knee of the curve) to be dependent on the orientation of the loading axis. The tests performed in RD and TD (transverse direction) had relatively sharp transitions compared to the test data from other orientations. We found the cyclic response of the material to reflect the monotonic anisotropy. The material response reached cyclic stability in 10 cycles or less with very little cyclic hardening or softening observed. For this reason, we focused our modeling effort on predicting the monotonic response. Reckoning that the primary source of anisotropy in the rolled plate is the processing-induced crystallographic texture, we employed the experimentally-measured texture of the undeformed plate material in continuum slip polycrystal plasticity model simulations of the monotonic experiments. Three types of simulations were conducted, upper and lower bound analyses and a finite element calculation that associates an element with each crystal in the aggregate. We found that all three analyses predicted anisotropy of the back-extrapolated yield strength and post-yield behavior with varying degrees of success in correlating the experimental data. In general, the upper and lower bound models predicted larger and smaller differences in the back-extrapolated yield strength, respectively, than was observed in the data. The finite element results resembled those of the upper bound when initially cubic elements were employed. We found that by employing an element shape that was more consistent with typical rolling microstructure, we were able to improve the finite element prediction significantly. The anisotropy of the elastic/elastic-plastic transition predicted by each model was also different in character. The lower bound predicted sharper transitions than the upper bound model, capturing the shape of the knee for the RD and TD data but failing to capture the other orientations. In contrast, the upper bound model predicted relatively long transitions for all orientations. As with the upper bound, the FEM calculation predicted gentle transitions with less transition anisotropy predicted than that of the upper bound. [S0094-4289(00)00201-2]

Acoustoelasticity in Layered Composites

Acoustoelasticity is a nondestructive technique used for determining applied and residual stresses in structural materials. It is based on the fact that as a material undergoes deformation, the longitudinal and shear wave speeds change. This technique has been successfully used in slightly anisotropic materials such as rolled aluminum plates. The purpose of this study is to examine the acoustoelastic response in layered composites: materials which are extremely anisotropic. The acoustoelastic response of these polymers is highly nonlinear and very different than that of metals.

Ultrasonic measurement of slight anisotropy in a cold‐rolled aluminum plate

Abstract In this paper, anisotropic wave propagation theory was utilized to measure the slight anisotropy of a cold‐rolled aluminum plate. To reveal the slight anisotropy (texture) in such a medium, the deviation of the energy and phase velocity was taken into account. A numerical algorithm was developed to calculate the phase velocity from the measured energy velocity, and hence, to determine the elastic constant matrix of the cold‐rolled aluminum plate. It is found, from the measurements, that the rolled aluminum plate preserves slight transverse isotropy with the axis of symmetry along the rolling direction. The Young's modulus along the rolling direction is slightly smaller than those along the other two directions.

Crystallographic texture in rolled aluminum plates: neutron pole figure measurements: Reno, R.C.; Fields, R.J.; Clark, A.V. Jr. Review of progress in quantitative nondestructive evaluation, Williamsburg, Virginia (United States), 22–26 Jun. 1987. vol. 7B, pp. 1439–1446. Edited by D.D. Thompson and D.E. Chimenti, Plenum Press, 1988

The process of ductile crack initiation has been investigated for a ferritic, pearlitic and a bainitic structural steel. A three-dimensional analysis has revealed that the ductile crack initiation occurs by formation of disconnected microcracks along the crack front. While the distribution of inclusions and highly strained regions governs the microcracking in the ferritic-pearlitic steel, the geometrical inhomogeneities produced by fatigue precracking act as the sites for formation of microcracks in the bainitic steel. In the latter steel, the size of the carbides is two orders of magnitude smaller than the crack tip opening produced by fatigue precracking, and hence, ductile crack initiation can not be modeled as the coalescence of the first microvoid with the crack tip.