A surface roughness model for a turning operation

A mathematical model for the surface roughness in a turning operation was developed in terms of the cutting speed, feed and depth of cut. Utilizing PL1 language and an IBM 360/50 computer, the model was used to generate contours of surface roughness in planes containing the cutting speed and feed at different levels of depth of cut. The surface roughness contours were used to select the machining conditions at which an increase in the rate of metal removal was achieved without sacrifice in surface finish.     

Interference methods for measuring surface roughness

Conclusions It is possible without incurring large expenditure, to apply under production conditions methods of interference microscopy by means of appropriately designed instruments for checking the production of components with a required degree of surface finish; in the first instance in lapping operations.The equidensity line, immersion, and Zehender methods extend the range of roughness which can be measured by means of interferometer microscopes.From a report by H. Trumpold D. Sc. (Eng) (Higher Technical School, Karl-Marxstadt, GDR) read at the Bauman Moscow Higher Technical School. The report was arranged for publication in Measurement Techniques by O. Ya. Egor'ev.     

Mould surface roughness and interfacial heat transfer using heat flow model

Abstract

The heat resistance at the metal/mould interface, represented by the interfacial heat transfer coefficient (IHTC), plays an important role in the rate of heat transfer from the metal to the mould. The objective of the present work was to determine the influence of the mould inner surface roughness on the IHTC using steel moulds of diameter 55 mm and height 56 mm with different surface roughnesses to solidify pure zinc with a superheat of 80 K. A computer program solving the heat conduction equation taking into consideration the convection in the molten zinc was used, together with the experimental temperature history, to determine the IHTC at the metal/mould interface. The results show that IHTC decreases as mould surface roughness increases.     

Instruments for contactless monitoring of internal surface roughness

Instruments Dozor-V and Dozor-VK are described whose operation is based on a reflexometric method. Test results are presented for cylindrical surfaces with a diameter of 30–100 mm with various forms of machining and materials. The instruments replace visual monitoring for roughness specimens and they are intended for application directly under industrial conditions. __________ Translated from Izmeritel’naya Tekhnika, No. 3, pp. 29–32, March 2006.     

A fatigue crack initiation model incorporating discrete dislocation plasticity and surface roughness

Although a thorough understanding of fatigue crack initiation is lacking, experiments have shown that the evolution of distinct dislocation distributions and surface roughness are key ingredients. In the present study we introduce a computational framework that ties together dislocation dynamics, the fields due to crystallographic surface steps and cohesive surfaces to model near-atomic separation leading to fracture. Cyclic tension–compression simulations are carried out where a single plastically deforming grain at a free surface is surrounded by elastic material. While initially, the cycle-by-cycle maximum cohesive opening increases slowly, the growth rate at some instant increases rapidly, leading to fatigue crack initiation at the free surface and subsequent growth into the crystal. This study also sheds light on random local microstructural events which lead to premature fatigue crack initiation.     

A geometric model for fatigue crack closure induced by fracture surface roughness under mode I displacements

A geometric model dealing with the roughness-induced fatigue crack closure under mode I displacements is proposed. It is shown that roughness-induced crack closure can also be acquired without mode II and III displacements at the crack tip. In this mechanism, the severe contact region is near the crack tip. The average crack closure ratio is the result of discrete asperities which come into contact.     

Quantifying the surface roughness effect in microindentation using a proportional specimen resistance model

The influence of the surface roughness on the indentation size effect in microindentation was examined using the proportional specimen resistance model. Stainless steel, aluminium, and copper surfaces were polished to different levels of roughness and subjected to microindentation. The results showed that the indentation size effect increases with increasing surface roughness, according to the proportional specimen resistance model. A normalized hardness equation H/H ₀ = (c ₀ + c ₁ R _a)/(a ₂ d) + 1 was established, and the value of c ₁ can be used to quantify the effect of surface roughness on the severity of the indentation size effect; this value was found to be highest for stainless steel, followed by copper and aluminium.     

Hybrid vision system for online measurement of surface roughness

A hybrid vision system for online measurement of surface roughness is introduced. The hybrid vision system applies two cameras for capturing the laser speckle pattern and scattering images simultaneously. With the help of advanced image processing, several features of texture and shape are computed for the surface roughness characterization. On the basis of experimental tests, feature fusion to improve measurement range and linearization of the measurement is also discussed.     

Single-layer graphene-based surface plasmon resonance sensor with dynamic evanescent field enhancement for biomarker study

ABSTRACT

In this work, we have developed a kind of single-layer graphene-based surface plasmon resonance (SLG-SPR) biosensor to detect C-reactive protein (CRP) and Prostate-specific antigen (PSA). In the experiment of testing CPR, the results obtained revealed that the changes in resonance wavelength of SLG-SPR biosensors are higher than that of the gold-film based SPR (Au-SPR) biosensors. Moreover, for the experiment of testing PSA, due to the dynamic evanescent field enhancement produced by a strong electric field coupling between the localized SPR (LSPR) of AuNPs and SPR of single-layer graphene-based film (SLG-film) that further amplify the evanescent field signal. We verified the SLG-SPR biosensors exhibited higher sensitivity than the Au-SPR biosensors and the SLG-SPR biosensor exceeded the traditional biosensor detection limit. Accordingly, the SLG-SPR biosensor based on dynamic optical enhancement can realize high sensitivity detection of low concentration biomarkers and can be applied to most of the trace biomarkers in theory.     

Wavelet uniformity of plasma-processed surface roughness

A technique to characterize the nonuniformity of surface roughness (NSR) is presented. A discrete wavelet transformation (DWT) was used to quantitatively differentiate surface patterns. The technique was evaluated with the data collected from the etching of silicon oxynitride films in a C₂F₆ inductively coupled plasma. 3-D surface images were obtained by using atomic force microscopy. Vertical and lateral NSRs were investigated as a function of process parameters, including radio frequency source power, bias power, and pressure. The NSR data were correlated to experimental measurements of the surface roughness. It is noticeable that for any parameter variations there exist nearly identical NSRs. For each parameter variation, there was at least one specific NSR consistent with the surface roughness measurement. Selected NSRs can be utilized to monitor a variation in NSR and surface roughness simultaneously. Also, NSR may be more stringently optimized by controlling NSRs in a directional fashion.     

A theoretical model for roughness induced crack closure

A theoretical model for the effects of grain size on the magnitude of roughness induced crack closure (RICC) at fatigue crack growth threshold has been proposed. With the basic configuration of a crack propagating incrementally along planar slip bands and deflecting at grain boundaries, an idealized zig-zag crack path is considered. The effective slip band length is considered to be equal to grain size. It is assumed that the dislocations emitted from the crack tip upon loading to form the pile-up are completely irreversible to produce a comnined mode I and mode II displacement at the crack tip. The assumption of continuously distributed dislocations in the pile-up facilitated the calculation of crack tip sliding displacement (CTSD) along the slip plane from which the mode I closure disregistry just behind the crack tip can be calculated. The closure stress intensity factor at threshold, K _el,th could then be expressed as a function of critical resolved shear stress, average macroscopic yield stress, angle subtended by the slip plane with the crack plane and the length of the slip band. Comparisons of the predicted trends with experimental data from various alloy systems indicate good agreement.

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Résumé On propose un modèle théorique pour décrire les effets de la taille du grain sur l'importance de la rugosité associée à la fermeture d'une fissure lors du franchissement du seuil de propagation en fatigue. On considère un chemin de fissuration en zig-zag idéalisé, avec une configuration de base d'une fissure qui se propage par incréments le long des bandes de glissements et par déviations aux frontières des grains. La longueur effective d'une bande de glissement est prise comme égale à la taille du grain. On suppose que les dislocations émises de l'extrémité de la fissure sous charge et qui forment l'empilement, sont totalement irréversibles au point de produire un déplacement combiné de mode-I et de mode-II à cette même extrémité. L'hypothèse de dislocations continûment distribuées dans l'empilement facilite le calcul du dèplacement par glissement de l'extrémité de la fissure le long du plan de glissement, à partir duquel on peut établir les conditions de fermeture en mode-I juste derrière l'extrémité de la fissure. Le facteur d'intensité de contraites de seuil peut dès lors être exprimé en fonction de la contrainte critique de cisaillement, de la limite élastique macroscopique moyenne, de l'angle entre le plan de glissement et le plan de la fissure, et de la longueur de la bande de glissement. Un bon accord est trouvé entre les tendances prévues et les données expérimentales, dans le cas de divers alliages.