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Background
Uphill quenching (UHQ) of heat treatable aluminium alloy components is a long established but rarely practiced or investigated method of reducing residual stresses. The efficacy of the technique has not been quantified on thin walled structures before and this investigation will address that deficiency.
Objective
To quantify the impact...
Context in source publication
Context 1
... quenched into the 30% PAG solution. It is clear that quenching into PAG has had a dramatic influence on the residual stress magnitudes compared to CWQ. All three walls of the box are almost free of residual stress. Like the CWQ box, the 1.5 mm wall surface did have a large residual stress in the y (LT) direction (σ yy = -87 ± 4 MPa) as shown in Fig. 11. The same sectioning process was undertaken, and in the unconstrained wall, the residual stress became equibiaxial of magnitude -18 ± 2 ...
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This paper presents the results of residual stress distribution measured by the neutron diffraction (ND) method in an extruded 7050 aluminum alloy used to fabricate the second rib structure of an aircraft wing. Residual stresses introduced due to heat treatments still remain following stress relief steps by stretching and extrusion and are complete...
Citations
This work describes the design and implementation of optics for EXCLAIM, the EXperiment for Cryogenic Large-Aperture Intensity Mapping. EXCLAIM is a balloon-borne telescope that will measure integrated line emission from carbon monoxide at redshifts z < 1 and ionized carbon ([CII]) at redshifts z = 2.5 − 3.5 to probe star formation over cosmic time in cross-correlation with galaxy redshift surveys. The EXCLAIM instrument is designed to observe at frequencies of 420–540 GHz using six microfabricated silicon integrated spectrometers with spectral resolving power R = 512 coupled to kinetic inductance detectors. A completely cryogenic telescope cooled to a temperature below 5 K provides low-background observations between narrow atmospheric lines in the stratosphere. Off-axis reflective optics use a 90-cm primary mirror to provide 4.2′ full-width at half-maximum resolution at the center of the EXCLAIM band over a field of view of 22.5′. Illumination of the 1.7 K cold stop combined with blackened baffling at multiple places in the optical system ensures low (<−40 dB) edge illumination of the primary to minimize spill onto warmer elements at the top of the dewar.
The wing edge (large 7050 aluminum alloy cambered forging) is the major force-bearing component of the aircraft. Reducing the quenching residual stress on the wing edge is crucial after manufacturing. In this paper, a novel cold compression process is proposed to reduce the quenching residual stress by integral deformation along the arc length direction and subsection deformation along the width direction. The obtained results demonstrate that the residual tensile stress is concentrated in the center where the sternum and ribs intersect after quenching. Matching the quenching residual stress distribution, an adaptive cold compression (2% rib + 0.5% sternum) was implemented, the residual tensile stress along the arc length direction decreases almost 80%; especially the residual stress on the rib is effectively reduced. There is little difference between the simulation results and the practical measured results, and the simulation results have great reference value.
This paper investigated the evolution of residual stress of 7050 aluminum alloy during solid solution, uphill quenching and aging treatments through finite element simulation method (FEM) and experiments. The effects of residual stress on processing deformation and tensile properties were explored. The results showed that overall residual stress amplitude of the sample was increased with the decrease in cryogenic temperature, which was independent of the cooling rate. The combination of uphill quenching and aging treatment can release the quenching residual stress by 55%. The mechanism of uphill quenching was related to the temperature difference between the surface and core of the sample. With the increase in temperature difference, the direction of residual stress caused by heating was consistent with quenching residual stress, which resulted in stress superposition and consequently released the residual stress through plastic deformation. With the decrease in temperature difference, the direction was opposite to the quenching residual stress, and they interacted with each other to induce the release of residual stress. Original residual stress with low amplitude and uniform distribution after combined uphill quenching and aging treatment made contribution to improve the dimensional accuracy of aluminum alloy components after machining without no obvious deterioration in tensile strength.
