Distributed Excitation of Crossflow Waves Due to Scattering of Freestream Vortices by Surface Waviness

2021 ◽  
pp. 327-336
Author(s):  
V. I. Borodulin ◽  
A. V. Ivanov ◽  
Y. S. Kachanov
Keyword(s):  
Surface Waviness

Analysis of vibration response and machining quality of hybrid robot based UD-CFRP trimming

2021 ◽  
pp. 095440542098609
Author(s):  
Yan Zhang ◽  
Hao Li ◽  
Xuda Qin ◽  
Jie liu ◽  
Zhuojie Hou
Keyword(s):  
High Performance ◽  
Vibration Response ◽  
Industrial Robots ◽  
Force Characteristic ◽  
Surface Waviness ◽  
Machined Surface ◽  
Machining Quality ◽  
3D Surface Roughness ◽  
Machined Surface Quality ◽  
Vibration Responses

To fulfill the demands of higher precision, better quality, and more flexibility, the usage of high-performance industrial robots is rapidly increased in aerospace industry. Considering the anisotropic and inhomogeneous characteristics of composite materials, this study focuses mainly on dynamic response investigation of a newly designed hybrid robot (named as TriMule) in CFRP trimming process and its influence on the machined quality. First, combined with the cutting force characteristic, the vibration responses of tool center point (TCP) under the dynamic excitation were obtained. The influences of robotic TCP vibration on machined surface quality with different fiber orientations, including surface waviness, cavity, 3D surface roughness, and depth of affected zone, are first studied by comparing hybrid robot and machine tool. From experiment results, it can be concluded the proposed TCP vibration response model has sufficient prediction accuracy. Meanwhile, it is found that larger robotic vibration response is accompanied by higher surface waviness, bigger surface cavity, and greater affected zone. Results also showed that the fiber orientation and milling style are two essential factors that affect robot vibration and machining quality during CFRP trimming.

Acoustic receptivity and evolution of two-dimensional and oblique disturbances in a Blasius boundary layer

2001 ◽  
Vol 432 ◽  
pp. 69-90 ◽  
Author(s):  
RUDOLPH A. KING ◽  
KENNETH S. BREUER
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Acoustic Wave ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Surface Waviness ◽  
S Wave ◽  
Boundary Layer Instability ◽  
Blasius Boundary Layer ◽  
Tollmien Schlichting

An experimental investigation was conducted to examine acoustic receptivity and subsequent boundary-layer instability evolution for a Blasius boundary layer formed on a flat plate in the presence of two-dimensional and oblique (three-dimensional) surface waviness. The effect of the non-localized surface roughness geometry and acoustic wave amplitude on the receptivity process was explored. The surface roughness had a well-defined wavenumber spectrum with fundamental wavenumber kw. A planar downstream-travelling acoustic wave was created to temporally excite the flow near the resonance frequency of an unstable eigenmode corresponding to kts = kw. The range of acoustic forcing levels, ε, and roughness heights, Δh, examined resulted in a linear dependence of receptivity coefficients; however, the larger values of the forcing combination εΔh resulted in subsequent nonlinear development of the Tollmien–Schlichting (T–S) wave. This study provides the first experimental evidence of a marked increase in the receptivity coefficient with increasing obliqueness of the surface waviness in excellent agreement with theory. Detuning of the two-dimensional and oblique disturbances was investigated by varying the streamwise wall-roughness wavenumber αw and measuring the T–S response. For the configuration where laminar-to-turbulent breakdown occurred, the breakdown process was found to be dominated by energy at the fundamental and harmonic frequencies, indicative of K-type breakdown.

Predicting the surface waviness of sheet moulding compound parts by simulating process-induced thermal stresses

2011 ◽  
Vol 31 (8-9) ◽  
Author(s):  
Walter Michaeli ◽  
Christoph Kremer
Keyword(s):  
Thermal Stresses ◽  
Surface Defects ◽  
Computation Method ◽  
Surface Waviness ◽  
Curing Reaction ◽  
Calculated Stress ◽  
Moulding Compound ◽  
Different Types ◽  
Sheet Moulding Compound ◽  
Good Agreement

Abstract This paper describes an opportunity to compute the surface waviness of compression moulded sheet moulding compound (SMC) parts by simulating residual stresses. First, different types of surface defects occurring on SMC parts are discussed. A method for calculating the surface waviness of the compression moulded part is presented, which combines the simulation of the production process and the structural computation. Modelling of the curing reaction and the development of mechanical properties are discussed and implemented. The potential of the computation method is shown for an automotive fender made of SMC. The results state that the curing reaction of SMC can be well described using the approach of Ng and Manas-Zloczower. The position of the measured waviness on the examined fender is in good agreement with the calculated stress distribution.

Enhancing surface waviness

1992 ◽  
Vol 36 (4) ◽  
pp. 18
Keyword(s):  
Surface Waviness

Deterministic retrieval of surface waviness by means of topography with coherent X-rays

2002 ◽  
Vol 9 (4) ◽  
pp. 223-228 ◽  
Author(s):  
A. Souvorov ◽  
M. Yabashi ◽  
K. Tamasaku ◽  
T. Ishikawa ◽  
Y. Mori ◽  
...  
Keyword(s):  
X Rays ◽  
Surface Waviness

Influence of Surface Waviness on the Thermal Elastohydrodynamic Lubrication of an Eccentric-Tappet Pair

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
J. Wang ◽  
C. H. Venner ◽  
A. A. Lubrecht
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Surface Waviness ◽  
Film Pressure ◽  
Oil Film ◽  
Working Cycle ◽  
Temperature Oscillations ◽  
Minimum Film Thickness ◽  
Traction Coefficient ◽  
Oil Film Pressure

The effect of single-sided and double-sided harmonic surface waviness on the film thickness, pressure, and temperature oscillations in an elastohydrodynamically lubricated eccentric-tappet pair has been investigated in relation to the eccentricity and the waviness wavelength. The results show that, during one working cycle, the waviness causes significant fluctuations of the oil film, pressure, and temperature, as well as a reduction in minimum film thickness. Smaller wavelength causes more dramatic variations in oil film. The fluctuations of the pressure, film thickness, temperature, and traction coefficient caused by double-sided waviness are nearly the same compared with the single-sided waviness, but the variations are less intense.

A Numerical Study of Three-Dimensional Natural Convective Heat Transfer From a Plate With a “Wavy” Surface

2001 ◽  
Author(s):  
Patrick H. Oosthuizen ◽  
Matt Garrett
Keyword(s):  
Heat Transfer ◽  
Prandtl Number ◽  
Surface Waves ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Three Dimensional ◽  
Wavy Surface ◽  
Surface Waviness ◽  
Dimensionless Amplitude ◽  
The Mean

Abstract Natural convective heat transfer from a wide isothermal plate which has a “wavy” surface, i.e., has a surface which periodically rises and falls, has been numerically studied. The surface waves run parallel to the direction of flow over the surface and have a relatively small amplitude. Two types of wavy surface have been considered here — saw-tooth and sinusoidal. Surfaces of the type considered are approximate models of situations that occur in certain window covering applications, for example, and are also sometimes used to try to enhance the heat transfer rate from the surface. The flow has been assumed to be laminar. Because the surface waves are parallel to the direction of flow, the flow over the surface will be three-dimensional. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces, this being treated by means of the Boussinesq type approximation. The governing equations have been written in dimensionless form, the height of the surface being used as the characteristic length scale and the temperature difference between the surface temperature and the temperature of the fluid far from the plate being used as the characteristic temperature. The dimensionless equations have been solved using a finite-element method. Although the flow is three-dimensional because the surface waves are all assumed to have the same shape, the flow over each surface thus being the same, and it was only necessary to solve for the flow over one of the surface waves. The solution has the following parameters: the Grashof number based on the height, the Prandtl number, the dimensionless amplitude of the surface waviness, the dimensionless pitch of the surface waviness, and the form of the surface waviness (saw-tooth or sinusoidal). Results have been obtained for a Prandtl number of 0.7 for Grashof numbers up to 106. The effects of Grashof number, dimensionless amplitude and dimensionless pitch on the mean heat transfer rate have been studied. It is convenient to introduce two mean heat transfer rates, one based on the total surface area and the other based on the projected frontal area of the surface. A comparison of the values of these quantities gives a measure of the effectiveness of the surface waviness in increasing the mean heat transfer rate. The results show that while surface waviness increases the heat transfer rate based on the frontal area, the modifications of the flow produced by the surface waves are such that the increase in heat transfer rate is less than the increase in surface area.

Effect of Mechanical Alignment System on Assembly Accuracy

2000 ◽  
Author(s):  
Neville K. S. Lee ◽  
Grace H. Yu ◽  
Y. Zou ◽  
J. Y. Chen ◽  
Ajay Joneja
Keyword(s):  
Alignment Accuracy ◽  
Mechanical Alignment ◽  
Mechanical Assembly ◽  
Surface Waviness ◽  
Form Errors ◽  
Multi Stage ◽  
Assembly Accuracy ◽  
Alignment System ◽  
Simulation Based ◽  
Selection Of

Abstract Mechanical means of positioning are frequently used in mechanical assembly processes. However, very little attention has been paid to the selection of mechanical alignment systems (MAS) for assembly processes. Our analysis shows that if the MAS are not properly selected, the form errors as well surface waviness and roughness of the workpieces to be assembled can badly limit the level of accuracy achievable. A simulation-based methodology is described to study the alignment accuracy for multi-stage processes. Such cases are common, where fabrication operations are done on parts before they are assembled. The study shows that if the workpieces are aligned in the same orientation, using similar or identical MAS for the fabrication processes and assembly processes, then the effect of the form errors as well as surface waviness and roughness of the workpieces can be greatly suppressed.

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