scholarly journals Theoretical Study of Path Adaptability Based on Surface Form Error Distribution in Fluid Jet Polishing

2018 ◽  
Vol 8 (10) ◽  
pp. 1814 ◽  
Author(s):  
Yanjun Han ◽  
Lei Zhang ◽  
Cheng Fan ◽  
Wule Zhu ◽  
Anthony Beaucamp
Keyword(s):  
Material Removal ◽  
Bulk Material ◽  
Critical Evaluation ◽  
Error Distribution ◽  
Residual Error ◽  
Polished Surface ◽  
Surface Form ◽  
Optimization Strategy ◽  
Form Error ◽  
The Difference

In the technology of computer-controlled optical surfacing (CCOS), the convergence of surface form error has a close relationship with the distribution of surface form error, the calculation of dwell time, tool influence function (TIF) and path planning. The distribution of surface form error directly reflects the difference in bulk material removal depth across a to-be-polished surface in subsequent corrective polishing. In this paper, the effect of path spacing and bulk material removal depth on the residual error have been deeply investigated based on basic simulation experiments excluding the interference factors in the actual polishing process. With the relationship among the critical evaluation parameters of the residual error (root-mean-square (RMS) and peak-to-valley (PV)), the path spacing and bulk material removal depth are mathematically characterized by the proposed RMS and PV maps, respectively. Moreover, a variable pitch path self-planning strategy based on the distribution of surface form error is proposed to optimize the residual error distribution. In the proposed strategy, the influence of different bulk material removal depths caused by the distribution of surface form error on residual error is compensated by fine adjustment of the path spacing according to the obtained path spacing optimization models. The simulated experimental results demonstrate that the residual error optimization strategy proposed in this paper can significantly optimize the overall residual error distribution without compromising the convergence speed. The optimized residual error distribution obtained in sub-regions of the polished surface is more uniform than that without optimization and is almost unaffected by the distribution of parent surface form error.

COMPRESSION OF IMAGES REPRESENTED USING MULTI-TRANSFORMS

1996 ◽  
Vol 06 (01) ◽  
pp. 41-57 ◽  
Author(s):  
ARUN RAMASWAMY ◽  
WASFY B. MIKHAEL
Keyword(s):  
Image Representation ◽  
Adaptive Algorithms ◽  
Residual Error ◽  
Transform Domain ◽  
Optimization Strategy ◽  
Efficient Coding ◽  
Transform Coefficients ◽  
Snr Improvement ◽  
The Difference

Constrained image representation employing multi-transforms has been recently developed. First, the image is divided into smaller non-overlapping subimages. Each subimage is resolved appropriately into 2-D subsignals, each of which is compactly represented in a specific transform domain. The subimage is efficiently represented by superimposing the dominant components corresponding to the subsignals. The residual error, which is the difference between the original subimage and the reconstructed subimage is minimized by adaptive algorithms. An optimization strategy selects the dominant coefficients from the various domains for adaptation. An efficient coding technique is presented to code the multi-transform coefficients. An image representation example is presented employing the DCT-Haar combination. Objective evaluations are made where it is shown that images represented using the multi-transform technique are more accurate than using the DCT for the same number of retained transform coefficients. Test subimages with a high amount of detail represented using the proposed technique show an SNR improvement of about 3 to 4 dB over using DCT alone. Finally, images, coded at bit rates of 0.44 bits/pixel and 1.23 bits/pixel employing the proposed technique verify the good quality of reconstruction.

Ultra Smooth Planarization Polishing Technique Based on the Cluster Magnetorheological Effect

2010 ◽  
Vol 135 ◽  
pp. 18-23 ◽  
Author(s):  
Qiu Sheng Yan ◽  
Jie Wen Yan ◽  
Jia Bin Lu ◽  
Wei Qiang Gao
Keyword(s):  
Surface Roughness ◽  
Carbonyl Iron ◽  
Material Removal ◽  
Optical Glass ◽  
Removal Rate ◽  
Polished Surface ◽  
Mr Fluid ◽  
Magnetorheological Effect ◽  
The Difference ◽  
Mr Effect

A new planarization polishing method based on the cluster magnetorheological (MR) effect is presented to polish optical glass in this paper. Some process experiments were conducted to reveal the influence of the content of carbonyl iron and the abrasive materials in the MR fluid on the machining effect, and the machining characteristic of polished surface was studied. The results indicate that the surface roughness of the polished workpiece can be reduced rapidly when the strong magnetic field is applied, and ultra smooth surface with Ra 1.4 nm can be achieved while the CeO2 abrasives are used in the MR fluid. The content of carbonyl iron obviously influences the machining effect of this planarization polishing method based on cluster MR-effect. With the increase of the content of carbonyl iron in the MR fluid, the material removal rate improves and the surface roughness reduces rapidly. However, the difference of abrasive material results in various machining effects. As for the K9 optical glass, the CeO2 abrasive is better polishing abrasive than the SiC abrasive in the planarization polishing technique based on the cluster MR-effect.

Accurate Extraction of Normal Residual Error for Compensation Grinding

2012 ◽  
Vol 565 ◽  
pp. 100-104
Author(s):  
Feng Jun Chen ◽  
Shao Hui Yin ◽  
Jian Wu Yu
Keyword(s):  
Measurement Data ◽  
Residual Error ◽  
Form Error ◽  
Original Measurement ◽  
Partitioning Algorithm ◽  
The Difference ◽  
Gaussian Regression ◽  
Ground Profile ◽  
Iterative Partitioning ◽  
The Ideal

An extracting method of normal residual error from a ground profile was proposed in this paper. Original measurement data was re-processed for obtaining an actual ground profile in an on-machine contact measurement system. The robust Gaussian regression filtering and NURBS fitting methods were employed to filter and fit these discrete data for getting the accurate realistic ground profile. By utilizing iterative partitioning algorithm, the normal residual error could be accurately obtained between the actual ground profile and the ideal one. Measurement data achieved from grinding experiment of aspheric mould were dealt with. After form error compensation grinding, the difference between normal residual error and original reached 40 nm in stead of initially 140 nm.

Modeling Methods of Cylindrical Surface Form Error by Precision Turning for Assembly

2013 ◽  
Vol 300-301 ◽  
pp. 248-252
Author(s):  
Xin Jin ◽  
Xi Zhang ◽  
Zhi Jing Zhang ◽  
Ting Yu Zhang ◽  
Jian Feng Chen
Keyword(s):  
Cylindrical Surface ◽  
Error Distribution ◽  
Simulation Software ◽  
Modeling Method ◽  
Least Square ◽  
Surface Form ◽  
Form Error ◽  
Distribution Law ◽  
Precision Turning ◽  
Measuring Machine

A modeling method of parts surface form error distribution by precision turning for assembly is proposed in this paper. Selecting cylindrical surface by turning as the research objective, the study of modeling method of form error distribution law is carried out. According to the data from the precision surface which is measured by coordinate measuring machine (CMM), we model form error using the mathematical and numerical simulation software, followed by studying the form error distribution law of the cylindrical surface by precision turning. Finally, the form error numerical model for assembly is established based on the least square method. All the research above can provide guidance for the precision microminiature parts assembly and the improvement of assembly accuracy of precision parts.

scholarly journals Numerical Simulation of Effect of Different Initial Morphologies on Melt Hydrodynamics in Laser Polishing of Ti6Al4V

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 581
Author(s):  
Kai Li ◽  
Zhenyu Zhao ◽  
Houming Zhou ◽  
Hao Zhou ◽  
Jie Yin ◽  
...  
Keyword(s):  
Flow Behavior ◽  
Processing Parameters ◽  
Surface Finishing ◽  
Polished Surface ◽  
Laser Polishing ◽  
Starting Position ◽  
Double Spiral ◽  
The Difference ◽  
Thermocapillary Forces ◽  
Surface Morphologies

As a surface finishing technique for rapid remelting and re-solidification, laser polishing can effectively eliminate the asperities so as to approach the feature size. Nevertheless, the polished surface quality is significantly sensitive to the processing parameters, especially with respect to melt hydrodynamics. In this paper, a transient two-dimensional model was developed to demonstrate the molten flow behavior for different surface morphologies of the Ti6Al4V alloy. It is illustrated that the complex evolution of the melt hydrodynamics involving heat conduction, thermal convection, thermal radiation, melting and solidification during laser polishing. Results show that the uniformity of the distribution of surface peaks and valleys can improve the molten flow stability and obtain better smoothing effect. The high cooling rate of the molten pool resulting in a shortening of the molten lifetime, which prevents the peaks from being removed by capillary and thermocapillary forces. It is revealed that the mechanism of secondary roughness formation on polished surface. Moreover, the double spiral nest Marangoni convection extrudes the molten to the outsides. It results in the formation of expansion and depression, corresponding to nearby the starting position and at the edges of the polished surface. It is further found that the difference between the simulation and experimental depression depths is only about 2 μm. Correspondingly, the errors are approximately 8.3%, 14.3% and 13.3%, corresponding to Models 1, 2 and 3, respectively. The aforementioned results illustrated that the predicted surface profiles agree reasonably well with the experimentally measured surface height data.

scholarly journals Influence of Apical Patency and Cleaning of the Apical Foramen on Periapical Extrusion in Retreatment

2013 ◽  
Vol 24 (5) ◽  
pp. 482-486 ◽  
Author(s):  
Marili Doro Andrade Deonizio ◽  
Gilson Blitzkow Sydney ◽  
Antonio Batista ◽  
Roberto Pontarolo ◽  
Paulo Ricardo Bittencourt Guimarães ◽  
...  
Keyword(s):  
Material Removal ◽  
Filling Material ◽  
Mean Values ◽  
Filtration System ◽  
Root Canal Retreatment ◽  
Significant Difference ◽  
Before And After ◽  
The Mean ◽  
The Difference ◽  
Removal Technique

This study evaluated the influence of apical patency, root filling removal technique and cleaning of the apical foramen, concerning the amount of debris extruded during root canal retreatment. Forty mandibular incisors were randomly assigned to 4 groups - GIM (n=10), GIIM (n=10), GIPT (n=10) and GIIPT (n=10), which were named according to leaving (I) or not (II) apical patency during canal preparation and filling removal technique (manual - M or ProTaper system - PT). After filling material removal, each specimen of each group had the apical foramen cleaned by sizes 15, 20 and 25 instruments, generating 12 subgroups: GIM15, GIM20, GIM25, GIIM15, GIIM20, GIIM25, GIPT15, GIPT20, GIPT25, GIIPT15, GIIPT20 and GIIPT25. Extruded filling debris was collected by a Milipore filtration system, an HV-durapore, 0.45 µm pore filter with a 25 mm diameter. The filters were weighed before and after the collection on an analytical scale (10–5 g), and the difference was calculated. The mean weight of extruded filling debris was analyzed statistically by Kruskal-Wallis and Friedman ANOVA tests (α=0.05). The mean values found in the groups (in mg) were: GIM (0.95±0.94), GIIM (0.47±0.62), GIPT (0.30±0.31) and GIIPT (0.32±0.44). There was no statistically significant difference among any of the groups or subgroups (p>0.05). ProTaper provided the smallest amount of extruded filling material, regardless of presence or absence of apical patency, followed by manual technique, without and with apical patency. Additional amounts of debris were collected during cleaning of the apical foramen, regardless of the instrument, presence/absence of patency or root filling removal technique.

Mechanical Properties and Microstructure of Self-Lubricating Ceramic Cutting Tool Materials

2004 ◽  
Vol 471-472 ◽  
pp. 221-224 ◽  
Author(s):  
Jian Xin Deng ◽  
Tong Kun Cao ◽  
Jia Lin Sun
Keyword(s):  
Mechanical Properties ◽  
Cutting Tool ◽  
Solid Lubricants ◽  
Polished Surface ◽  
Ceramic Tool ◽  
Tool Materials ◽  
Ceramic Cutting Tool ◽  
Micro Cracks ◽  
The Difference ◽  
Cutting Tool Materials

Al2O3/TiC ceramic tool materials with the addition of solid lubricants such as BN and CaF2 were produced by hot pressing. Effect of the solid lubricants on the microstructure and mechanical properties has been studied. Results showed that AlN phase resulted from the reaction of Al2O3 with BN was formed in Al2O3/TiC/BN composite after sintering. Significant micro-cracks resulted from the residual stress owing to the difference in the thermal expansion coefficient were found on the polished surface, and caused large mechanical properties degradation. While Al2O3/TiC/CaF2 composite showed higher flexural strength, fracture toughness, and hardness compared with that of Al2O3/TiC/BN composite owing its porosity absent and finer microstructure.

Development of Tool Path Correction Algorithm in Incremental Sheet Forming

2014 ◽  
Vol 622-623 ◽  
pp. 382-389 ◽  
Author(s):  
Antonio Fiorentino ◽  
G.C. Feriti ◽  
Elisabetta Ceretti ◽  
C . Giardini ◽  
C.M.G. Bort ◽  
...  
Keyword(s):  
Tool Path ◽  
Error Distribution ◽  
Sheet Forming ◽  
Incremental Sheet Forming ◽  
Correction Algorithm ◽  
Forming Process ◽  
Part Geometry ◽  
Toolpath Planning ◽  
The Difference ◽  
Tool Path Correction

The problem of obtaining sound parts by Incremental Sheet Forming is still a relevant issue, despite the numerous efforts spent in improving the toolpath planning of the deforming punch in order to compensate for the dimensional and geometrical part errors related to springback and punch movement. Usually, the toolpath generation strategy takes into account the variation of the toolpath itself for obtaining the desired final part with reduced geometrical errors. In the present paper, a correction algorithm is used to iteratively correct the part geometry on the basis of the measured parts and on the calculation of the error defined as the difference between the actual and the nominal part geometries. In practice, the part geometry is used to generate a first trial toolpath, and the form error distribution of the resulting part is used for modifying the nominal part geometry and, then, generating a new, improved toolpath. This procedure gets iterated until the error distribution becomes less than a specified value, corresponding to the desired part tolerance. The correction algorithm was implemented in software and used with the results of FEM simulations. In particular, with few iterations it was possible to reduce the geometrical error to less than 0.4 mm in the Incremental Sheet Forming process of an Al asymmetric part, with a resulting accuracy good enough for both prototyping and production processes.

Some sources of error and possible bias in Danscan ultrasonic measurements of cattle

1983 ◽  
Vol 37 (1) ◽  
pp. 67-71
Author(s):  
J. P. Gibson ◽  
J. C. Alliston
Keyword(s):  
Measurement Error ◽  
Mean Value ◽  
Time Of Day ◽  
Error Distribution ◽  
The Body ◽  
Residual Error ◽  
Ultrasonic Measurements ◽  
The Mean ◽  
Ultrasonic Images ◽  
Account Variation

ABSTRACTPhotographs of ultrasonic images of 10 animals were taken. Two replicate photographs were taken at each of four body positions (10th rib, 13th rib, 3rd lumbar and hindquarter) on both sides of the body in the morning and the afternoon of the day of scanning. Several measurements were taken on each photograph by an experienced interpreter. Replicate photographs failed to account for all possible sources of measurement error. Since neither time of day nor side of the body affected the mean value, taking observations at different times of the day or on both sides of the body could permit most sources of measurement error to be taken into account. Variation due to errors of measurement and differences among animals are presented. The residual error distribution contained several extreme outliers.It was concluded that a better understanding of all the sources of bias and error will be needed if ultrasonic measurements are to be more widely used.

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