scholarly journals Aerodynamic Performance of a Nanostructure-Induced Multistable Shell

Aerospace ◽  
2021 ◽  
Vol 8 (11) ◽  
pp. 350
Author(s):  
Shenghui Yi ◽  
Lu Shen ◽  
Chih-Yung Wen ◽  
Xiaoqiao He ◽  
Jian Lu
Keyword(s):  
Wind Tunnel ◽  
Flat Plate ◽  
Aerodynamic Performance ◽  
Surface Mechanical Attrition Treatment ◽  
Stable Configuration ◽  
Adaptive Structures ◽  
Venus Flytrap ◽  
Mechanical Attrition

Multistable shells that have the ability to hold more than one stable configuration are promising for adaptive structures, especially for airfoil. In contrast to existing studies on bistable shells, which are well demonstrated by the Venus flytrap plant with the ability to feed itself, this work experimentally studies the aerodynamic response of various stable configurations of a nanostructure-induced multistable shell. This multistable shell is manufactured by using nanotechnology and surface mechanical attrition treatment (SMAT) to locally process nine circular zones in an original flat plate. The aerodynamic responses of eight stable configurations of the developed multistable shell, including four twisted configurations and four untwisted configurations with different cambers, are visually captured and quantitively measured in a wind tunnel. The results clearly demonstrate the feasibility of utilizing different controllable configurations to adjust the aerodynamic performance of the multistable shell.

Ultrasonic Evaluation of Compressive Residual Stress of Surface Treated Metals

2005 ◽  
Vol 490-491 ◽  
pp. 184-189 ◽  
Author(s):  
Farid Belahcene ◽  
Xiaolai Zhou ◽  
Jian Lu
Keyword(s):  
Experimental Data ◽  
Residual Stresses ◽  
Nondestructive Evaluation ◽  
Subsurface Layer ◽  
Surface Mechanical Attrition Treatment ◽  
Shallow Subsurface ◽  
Ultrasonic Evaluation ◽  
Mechanical Attrition ◽  
Machine Parts ◽  
Compressive Residual Stresses

Shot peening is an effective method of improving fatigue performance of machine parts in the industry by producing a thin surface layer of compressive residual stresses that prevents crack initiation and retards crack growth during service. Nondestructive evaluation of the prevailing compressive residual stresses in the shallow subsurface layer is realized by the critically refracted longitudinal (Lcr) waves. This paper presents experimental data obtained on SMAT (surface mechanical attrition treatment) steel alloy S355 sample. Comparative travel-time shows that there are statistically significant differences in treated and untreated specimen. With knowledge of the acoustoelastic constants which are obtained by a test calibration, the experimental data indicates that compressive residual stresses are distributed near subsurface (hundreds of micron). These stress results show that the Lcr technique is efficient for evaluation of residual stresses after the surface treatment.

Influence of the Side Walls on the Turbulent Center-Plane Boundary-Layer in a Square Duct

1978 ◽  
Vol 100 (1) ◽  
pp. 91-96 ◽  
Author(s):  
V. de Brederode ◽  
P. Bradshaw
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Flat Plate ◽  
Cross Section ◽  
Secondary Flows ◽  
Plane Boundary ◽  
Square Duct ◽  
Streamwise Pressure Gradient ◽  
Side Walls ◽  
Working Section

Measurements in the entry region of a square duct (specifically, a wind-tunnel working section) show that the direct effect of stress-induced secondary flows in the corners on the center-plane boundary layer is negligible for boundary layers thinner than about one-fourth of the duct width. Further, the effects of streamwise pressure gradient and of quasi-collinear lateral convergence tend to cancel so that the velocity profiles and skin friction are quite close to those on a flat plate. This shows that the boundary layer on the floor of a wind tunnel of constant, square cross section can be used to simulate a flat-plate flow even when the boundary layer thickness is as large as one-fourth of the tunnel height.

Comparison of Surface Nanostructured Electrodeposited Cu Produced from Different Power Types: Microstructure and Tensile Properties

2009 ◽  
Vol 614 ◽  
pp. 189-196
Author(s):  
H.L. Chan ◽  
Jian Lu
Keyword(s):  
Mechanical Properties ◽  
Tensile Properties ◽  
Direct Current ◽  
Pulse Power ◽  
Double Pulse ◽  
Surface Mechanical Attrition Treatment ◽  
Electrodeposition Process ◽  
Mechanical Attrition ◽  
Off Time

Different Power types and parameters in the electrodeposition process result in different microstructures and hence mechanical properties. In this paper, direct current and double pulse power with different combinations of on and off time have been used for electrodeposition. The tensile properties of the electrodeposited (Ed) Cu with different parameters in process have been studied and also the microstructures of the Cu obtained have been examined by SEM. This paper aims at explaining the effects of one of the important parameters in electrodeposition: different power types on the tensile properties. The tensile properties of Ed Cu after Surface Mechanical Attrition Treatment (SMAT) are also shown in this paper.

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