			Home About us Contact

Material Removal (material + removal)

Distribution by Scientific Domains

Engineering	25%

Selected Abstracts

Toward Deterministic Material Removal and Surface Figure During Fused Silica Pad Polishing

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2010
Tayyab I. Suratwala
The material removal and surface figure after ceria pad polishing of fused silica glass have been measured and analyzed as a function of kinematics, loading conditions, and polishing time. Also, the friction at the workpiece/lap interface, the slope of the workpiece relative to the lap plane, and lap viscoelastic properties have been measured and correlated to material removal. The results show that the relative velocity between the workpiece and the lap (i.e., the kinematics) and the pressure distribution determine the spatial and temporal material removal, and hence the final surface figure of the workpiece. In cases where the applied loading and relative velocity distribution over the workpiece are spatially uniform, a significant nonuniformity in material removal, and thus surface figure, is observed. This is due to a nonuniform pressure distribution resulting from: (1) a moment caused by a pivot point and interface friction forces; (2) viscoelastic relaxation of the polyurethane lap; and (3) a physical workpiece/lap interface mismatch. Both the kinematics and these nonuniformities in the pressure distribution are quantitatively described, and have been combined to develop a spatial and temporal model, based on Preston's equation, called Surface Figure or SurF. The surface figure simulations are consistent with the experiment for a wide variety of polishing conditions. This study is an important step toward deterministic full-aperture polishing, allowing optical glass fabrication to be performed in a more repeatable, less iterative, and hence more economical manner. [source]

Integrated layout design of multi-component system

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2009
Jihong Zhu
Abstract A new integrated layout optimization method is proposed here for the design of multi-component systems. By introducing movable components into the design domain, the components layout and the supporting structural topology are optimized simultaneously. The developed design procedure mainly consists of three parts: (i) Introduction of non-overlap constraints between components. The finite circle method (FCM) is used to avoid the components overlaps and also overlaps between components and the design domain boundaries. (ii) Layout optimization of the components and supporting structure. Locations and orientations of the components are assumed as geometrical design variables for the optimal placement while topology design variables of the supporting structure are defined by the density points. Meanwhile, embedded meshing techniques are developed to take into account the finite element mesh change caused by the component movements. (iii) Consistent material interpolation scheme between element stiffness and inertial load. The commonly used solid isotropic material with penalization model is improved to avoid the singularity of localized deformation in the presence of design dependent loading when the element stiffness and the involved inertial load are weakened by the element material removal. Finally, to validate the proposed design procedure, a variety of multi-component system layout design problems are tested and solved on account of inertia loads and gravity center position constraint. Solutions are compared with traditional topology designs without component. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Toward Deterministic Material Removal and Surface Figure During Fused Silica Pad Polishing

Surface Finishing of Alumina Ceramics by Means of Abrasive Jet Machining

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2002
Manabu Wakuda
Abrasive jet machining (AJM) is proposed as a new approach to surface finishing of structural ceramics. The effect of AJM on the material removal behavior of a commercially available alumina ceramic, and its effect on mechanical properties, was characterized and compared with identical material subjected to conventional finishing processes. Conventional grinding of the ceramic resulted in a surface that was dominated by intergranular fracture, whereas, during AJM, impact by the abrasives led to material removal in a manner resembling ductile behavior, and the resulting surface appearance was much smoother. A significant improvement in flexural strength was attained, compared with the strength of both the ground and lapped samples, because of an induced compressive residual stress. [source]

Effects of femtosecond laser irradiation on osseous tissues

LASERS IN SURGERY AND MEDICINE, Issue 3 2007
B. Girard DMD
Abstract Background and Objective Few studies have investigated femtosecond (fs) lasers for cutting bone tissue. Study Design/Materials and Methods A 775 nm, 1 kHz, 200 femtosecond, up to 400 µJ laser system was used to irradiate in vitro calcified cortical bone samples and bone tissue culture samples. Results The ablation threshold in cortical bone was 0.69±0.08 J/cm2 at 775 nm and 0.19±0.05 J/cm2 at 387 nm. Plasma shielding experiments determined that the ablation plume and the plasma significantly affect material removal at high repetition rates and appear to generate thermal transients in calcified tissue. Confocal analysis revealed intact enzymatic activity on the surface of cells immediately adjacent to cells removed by fs laser irradiation. Conclusions These experiments demonstrate that fs lasers used for bone tissue cutting do not appear to generate significant temperature transients to inactivate proteins and that cellular membrane integrity is disrupted for only a few cell layers. Lasers Surg. Med. 39:273,285, 2007. © 2007 Wiley-Liss, Inc. [source]

Parametric optimization of magnetic-field-assisted abrasive flow machining by the Taguchi method

QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 4 2002
Sehijpal Singh
Abstract Some hybrid-machining processes have been developed in the recent past with a view to devising composite machining processes, which are able to overcome the limitations of one process with the help of advantageous features of another similar process. The present paper identifies the parameters of abrasive flow machining (AFM) that significantly affect the material removal when a magnetic field is applied around the workpiece. The Taguchi method has been adopted for studying the effect of magnetic-field-assisted AFM parameters, individually, on the abrasion rate of work materials. Optimization of the process parameters has been carried out for the purpose of off-line monitoring of the process. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Application of source removal and natural attenuation remediation strategies at MGP sites in Wisconsin

REMEDIATION, Issue 4 2003
James W. Lingle
This article presents site closure strategies of source material removal and dissolved-phase groundwater natural attenuation that were applied at two manufactured gas plant (MGP) sites in Wisconsin. The source removal actions were implemented in 1999 and 2000 with groundwater monitoring activities preceding and following those actions. Both of these sites have unique geological and hydrogeological conditions. The article briefly presents site background information and source removal activities at both of these sites and focuses on groundwater analytical testing data that demonstrate remediation of dissolved-phase MGP-related groundwater impacts by natural attenuation. A statistical evaluation of the data supports a stable or declining MGP parameter concentration trend at each of the sites. A comparison of the site natural attenuation evaluation is made to compare with the requirements for site closure under the Wisconsin Department of Natural Resources regulations and guidance. © 2003 Wiley Periodicals, Inc. [source]