Subsurface Pore-Induced Quilting During Machining of Metal Foams
01 Jun 2020-Journal of Micro and Nano-Manufacturing (American Society of Mechanical Engineers Digital Collection)-Vol. 8, Iss: 2
TL;DR: In this article, the authors investigated the possible use of monolithic foam structures with such interfaces wherein the porous structure provides needed light-weighting while the nonporous region provides a functional surface such as the one needed for optics.
Abstract:
Metal foams made by the melt route naturally have an interface region between the porous and nonporous structures. We investigate here the possible use of monolithic foam structures with such interfaces wherein the porous structure provides needed light-weighting while the nonporous region provides a functional surface such as the one needed for optics. Face turning is carried out in the nonporous region very near the interface to the porous areas. Using micro-computed tomography scans, pore positions are determined and the proximal effect of pores on the machined surface quilting effects are studied. Studies show that pore as near as 400 μm to the machined surface can cause significant quilting. Progress in developing finite element models to enable such predictions is also shown. This study could pave the way for the use of such structures for telescopic mirrors.
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03 Mar 1983
TL;DR: In the mid-1990s, NASA plans to orbit a giant telescope, whose aperture may be as great as 30 meters, for infrared and sub-millimeter astronomy as mentioned in this paper, and each segment must be shaped to precise curvature tolerances so that diffraction-limited performance will be achieved at 30 micron (nominal operating wavelength).
Abstract: In the mid-1990s, NASA plans to orbit a giant telescope, whose aperture may be as great as 30 meters, for infrared and sub-millimeter astronomy. Its primary mirror will be deployed or assembled in orbit from a mosaic of possibly hundreds of mirror segments. Each segment must be shaped to precise curvature tolerances so that diffraction-limited performance will be achieved at 30 micron (nominal operating wavelength). All panels must lie within 1 micron on a theoretical surface described by the optical precipitation of the telescope's primary mirror. To attain diffraction-limited performance, the issues of alignment and/or position sensing, position control of micron tolerances, and structural, thermal, and mechanical considerations for stowing, deploying, and erecting the reflector must be resolved. Radius of curvature precision influences panel size, shape, material, and type of construction. Two superior material choices emerged: fused quartz (sufficiently homogeneous with respect to thermal expansivity to permit a thin shell substrate to be drape molded between graphite dies to a precise enough off-axis asphere for optical finishing on the as-received a segment) and a Pyrex or Duran (less expensive than quartz and formable at lower temperatures). The optimal reflector panel size is between 1-1/2 and 2 meters. Making one, two-meter mirror every two weeks requires new approaches to manufacturing off-axis parabolic or aspheric segments (drape molding on precision dies and subsequent finishing on a nonrotationally symmetric dependent machine). Proof-of-concept developmental programs were identified to prove the feasibility of the materials and manufacturing ideas.
1 citations
TL;DR: In this article , a model of magic-mirror (Makyoh) imaging with the mirror backside relief as the input is described, and the mechanical pattern transfer is modelled by a convolution approach while the optical imaging using a nonlinear geometrical optical model, more general than previous approaches.
Abstract: A model of magic-mirror (Makyoh) imaging with the mirror backside relief as the input is described. The mechanical pattern transfer is modelled by a convolution approach while the optical imaging using a nonlinear geometrical optical model, more general than previous approaches. Characteristic features of the imaging is analysed and the linear approximation is examined. Diffraction effects are also treated. Characteristic features for the ancient mirror and applications in semiconductor wafer inspection are discussed.
References
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TL;DR: In this paper, a cumulative-damage fracture model is introduced which expresses the strain to fracture as a function of the strain rate, temperature and pressure, and the model is evaluated by comparing computed results with cylinder impact tests and biaxial (torsion-tension) tests.
4,744 citations
TL;DR: The possibilities for manufacturing metal foams or other porous metallic structures are reviewed in this article, where various manufacturing processes are classified according to the state of matter in which the metal is processed, such as solid, liquid, gaseous or ionised.
3,294 citations
TL;DR: In this article, finite element analysis (FEA) of micromachining using the arbitrary Lagrangian-Eulerian (ALE) method showed that chip is formed through material extrusion under a critical a/r
118 citations
15 Feb 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: Subbiah et al. as discussed by the authors investigated the effect of finite edge radius on ductile fracture by performing a series of experiments with inserts of different edge radii at various uncut chip thickness values ranging from 15 to 105μm.
Abstract: Evidence of ductile fracture leading to material separation has been reported recently in ductile metal cutting [S. Subbiah, S.N. Melkote, ASME J. Manuf. Sci. Eng. 28(3) (2006)]. This paper investigates the effect of finite edge radius on such ductile fracture. The basic question of whether such ductile fracture occurs in the presence of a finite edge radius is explored by performing a series of experiments with inserts of different edge radii at various uncut chip thickness values ranging from 15 to 105 μm. Chip–roots are obtained in these experiments using a quick-stop device and examined in a scanning electron microscope. Clear evidence of material separation is seen at the interface zone between the chip and machined surface even when the edge radius is large compared to the uncut chip thickness. Failure is seen to occur at the upper, middle, and/or the lower edges of the interface zone. Based on these observations, a hypothesis is presented for the events leading to the occurrence of this failure when cutting with an edge radius tool. Finite element simulations are performed to study the nature of stress state ahead of the tool edge with and without edge radius. Hydrostatic stress is seen to be tensile in front of the tool and hence favors the occurrence of ductile fracture leading to material separation. The stress components are, however lower than those seen with a sharp tool.
82 citations
TL;DR: Optical Fundamentals, R.R. Vukobratovich as mentioned in this paper and D.A. Paquin (PreMaTechs, Inc., Oro Valley, Arizona) Lightweight Mirror Design, D.E. Engelhaupt (Center for Applied Optics, University of Alabama, Huntsville, Alabama) Index
Abstract: Optical Fundamentals, R.R. Willey (Lexalite International Corporation, Charlevoix, Michigan) and R.E. Parks (Optical Sciences Center, University of Arizona, Tucson, Arizona) Optomechanical Design Principles, D. Vukobratovich (National Optical Astronomical Observatory [NOAO], Tucson, Arizona) Materials for Optical Systems, R.A. Paquin (PreMaTechs, Inc., Oro Valley, Arizona) Metal Mirrors, R.A. Paquin (PreMaTechs, Inc., Oro Valley, Arizona) Lightweight Mirror Design, D. Vukobratovich (National Optical Astronomical Observatory [NOAO], Tucson, Arizona) Optical Mounts: Lenses, Windows, Small Mirrors, and Prisms, P.R. Yoder, Jr. (Consultant in Optomechanical Engineering, Norwalk, Connecticut) Adjustment Mechanisms, A. Ahmad (Center for Applied Optics, University of Alabama, Huntsville, Alabama) Structural Analysis of Optics, V. Genberg (Eastman Kodak Company, Rochester, New York) Thermal and Thermoelastic Analysis of Optics, V. Genberg (Eastman Kodak Company, Rochester, New York) Fabrication Methods, D. Engelhaupt (Center for Applied Optics, University of Alabama, Huntsville, Alabama) Index
67 citations