MRF applications: measurement of process-dependent subsurface damage in optical materials using the MRF wedge technique

Menapace, Joseph A.; Davis, Paul; Steele, William A.; Suratwala, Tayyab; Miller, Philip E.

doi:10.1117/12.638839

Cited by 38 publications

(35 citation statements)

References 10 publications

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“…In our previous studies, the characteristics and statistical distribution of SSD as a function of different grinding processes using a polished taper technique has been measured and analyzed [14][15][16]. These results suggested that only a small fraction (1 out of tens of thousands of particles) of the abrasive particles were participating in the material removal by comparing the measured crack depth that with that expected from static indentation models.…”

Section: Introductionmentioning

confidence: 92%

“…1). Details of this characterization technique to determine SSD depth and length distributions are provided elsewhere [14][15][16]. Photographs of the grinding setup is shown in Fig.…”

Section: Ground Samplesmentioning

confidence: 99%

“…The SSD damage removal was verified by HF/NH 4 F etching for 30 minutes and inspecting the surface by optical microscopy for any observable surface cracks. The fused silica samples were then repolished for 1 hr with the same polishing slurry contaminated: 1) at various abrasive sizes of 4,6,10,15,20 or 45 µm at various concentrations using rogue diamond particles (Diamond Innovations DMS Poly 285T) on the polyurethane pad, 2) at various loads using 6 um diamond on polyurethane pad, 3) on various laps using the 6 um diamond, 4) at various temperatures using 6 um diamond on pitch, and 5) with various types of rogue particles (dust, diamond, pitch, dried ceria) on pitch. The matrix of experiments for the polishing experiments are shown in Table 2.…”

Section: Polished Samplesmentioning

confidence: 99%

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Effect of rogue particles on the sub-surface damage of fused silica during grinding/polishing

Suratwala

Steele

Feit

et al. 2008

Journal of Non-Crystalline Solids

135

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The distribution and characteristics of surface cracks (i.e., sub-surface damage or scratching) on fused silica formed during grinding/polishing resulting from the addition of rogue particles in the base slurry has been investigated. Fused silica samples (10 cm diameter x 1 cm thick) were: 1) ground by loose abrasive grinding (alumina particles 9-30 µm) on a glass lap with the addition of larger alumina particles at various concentrations with mean sizes ranging from 15-30 µm, or 2) polished (using 0.5 µm cerium oxide slurry) on various laps (polyurethanes pads or pitch) with the addition of larger rogue particles (diamond (4-45 µm), pitch, dust, or dried Ceria slurry agglomerates) at various concentrations. For the resulting ground samples, the crack distributions of the as-prepared surfaces were determined using a polished taper technique. The crack depth was observed to: 1) increase at small concentrations (>10 -4 fraction) of rogue particles; and 2) increase with rogue particle concentration to crack depths consistent with that observed when grinding with particles the size of the rogue particles alone. For the polished samples, which were subsequently etched in HF:NH 4 F to expose the surface damage, the resulting scratch properties (type, number density, width, and length) were characterized. The number density of scratches increased exponentially with the size of the rogue diamond at a fixed rogue diamond concentration suggesting that larger particles are more likely to lead to scratching. The length of the scratch was found to increase with rogue particle size, increase with lap viscosity, and decrease with applied load. At high diamond concentrations, the type of scratch transitioned from brittle to ductile and the length of the scratches dramatically increased and extended to the edge of the optic. The observed trends can explained semi-quantitatively in terms of the time needed for a rogue particle to penetrate into a viscoelastic lap. The results of this study provide useful insights and 'rules-of-thumb' relating scratch characteristics observed on surfaces during optical glass fabrication to the characteristics rogue particles causing them and their possible source.

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Section: Introductionmentioning

confidence: 92%

“…1). Details of this characterization technique to determine SSD depth and length distributions are provided elsewhere [14][15][16]. Photographs of the grinding setup is shown in Fig.…”

Section: Ground Samplesmentioning

confidence: 99%

Section: Polished Samplesmentioning

confidence: 99%

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Effect of rogue particles on the sub-surface damage of fused silica during grinding/polishing

Suratwala

Steele

Feit

et al. 2008

Journal of Non-Crystalline Solids

135

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“…Since the measurement of SSD with destructive methods is complex as well as cost-intensive and time-consuming, several attempts were undertaken to correlate process parameters and measurable output values, like surface roughness. The results of Lambropoulos et al and Wang et al show, however, a broad distribution in the results of these methods [7,8]. Even though there are numerous non-destructive approaches to determine the crack depths beneath the machined surface, the destructive methods still provide the most accurate results [7].…”

Section: Introductionmentioning

confidence: 99%

Influence of Cutting Speed on Subsurface Damage Morphology and Distribution in Ground Fused Silica

2017

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Abstract:In optical fabrication, brittle-hard materials are used for numerous applications. Especially for high-performance optics for laser or lithography applications, a complex and consistent production chain is necessary to account for the material properties. Particularly in pre-processing, e.g., for shaping optical components, brittle material behavior is dominant which leads to a rough surface layer with cracks that reach far below the surface. This so called subsurface damage (SSD) needs to be removed in subsequent processes like polishing. Therefore, it is essential to know the extent of the SSD induced by shaping for an efficient design of precise corrective processes and for process improvement. Within this work the influence of cutting speed on SSD, in fused silica, induced by grinding has been investigated. To analyze the subsurface crack distribution and the maximum crack depth magnetorheological finishing has been appointed to polish a wedge into the ground surface. The depth profile of SSD was analyzed by image processing. For this purpose a coherent area of the polished wedge has been recorded by stitching microscopy. Taking the form deviation of the ground surface in to account to determine the actual depth beneath surface, the accuracy of the SSD-evaluation could be improved significantly. The experiments reveal a clear influence of the cutting speed on SSD, higher cutting speeds generate less SSD. Besides the influence on the maximum crack depth an influence on the crack length itself could be verified. Based on image analysis it was possible, to predict the maximum depth of cracks by means of crack length.

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“…The details of how these rules were developed are described in each of the references included in this summary (1)(2)(3)(4)(5)(6)(7)(8)(9). Figure 2 provides as a summary of some of the more commonly used rules-of-thumbs that have been developed in this study.…”

mentioning

confidence: 99%

FY07 LDRD Final Report A Fracture Mechanics and Tribology Approach to Understanding Subsurface Damage on Fused Silica during Grinding and Polishing

Suratwala¹,

Miller²,

Menapace³

et al. 2008

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The objective of this work is to develop a solid scientific understanding of the creation and characteristics of surface fractures formed during the grinding and polishing of brittle materials, specifically glass. In this study, we have experimentally characterized the morphology, number density, and depth distribution of various surface cracks as a function of various grinding and polishing processes (blanchard, fixed abrasive grinding, loose abrasive, pitch polishing and pad polishing). Also, the effects of load, abrasive particle (size, distribution, foreign particles, geometry, velocity), and lap material (pitch, pad) were examined. The resulting data were evaluated in terms of indentation fracture mechanics and tribological interactions (science of interacting surfaces) leading to several models to explain crack distribution behavior of ground surfaces and to explain the characteristics of scratches formed during polishing. This project has greatly advanced the scientific knowledge of microscopic mechanical damage occurring during grinding and polishing and has been of general interest. This knowledge-base has also enabled the design and optimization of surface finishing processes to create optical surfaces with far superior laser damage resistance.There are five major areas of scientific progress as a result of this LDRD. They are listed in Figure 1 and described briefly in this summary below. The details of this work are summarized through a number of published manuscripts which are included this LDRD Final Report.In the first area of grinding, we developed a technique to quantitatively and statistically measure the depth distribution of surface fractures (i.e., subsurface damage) in fused silica as function of various grinding processes using mixtures of various abrasive particles size distributions. The observed crack distributions were explained using a model that extended known, single brittle indentation models to an ensemble of loaded, sliding particles. The model illustrates the importance of the particle size distribution of the abrasive and its influence on the resulting crack distribution. The results of these studies are summarized in references 1-7.In the second area of polishing, we conducted a series of experiments showing the influence of rogue particles (i.e., particles in the polishing slurry that are larger than base particles) on the creation of scratches on polished surfaces. Scratches can be thought of a as a specific type of sub-surface damage. The characteristics (width, length, type of fractures, concentration) were explained in terms of the rogue particle size, the rogue particle material, and the viscoelastic properties of the lap. The results of these studies are summarized in references 6-7.In the third area of etching, we conducted experiments aimed at understanding the effect of HF:NH 4 F acid etching on surface fractures on fused silica. Etching can be used as a method: a) to expose sub-surface mechanical damage, b) to study the morphology of specific mechanical damage occur...

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MRF applications: measurement of process-dependent subsurface damage in optical materials using the MRF wedge technique

Cited by 38 publications

References 10 publications

Effect of rogue particles on the sub-surface damage of fused silica during grinding/polishing

Effect of rogue particles on the sub-surface damage of fused silica during grinding/polishing

Influence of Cutting Speed on Subsurface Damage Morphology and Distribution in Ground Fused Silica

FY07 LDRD Final Report A Fracture Mechanics and Tribology Approach to Understanding Subsurface Damage on Fused Silica during Grinding and Polishing

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