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result(s) for
"Surface roughness"
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Rough and smooth
\"Compares and contrasts common rough and smooth objects, both in nature and man-made. Includes comprehension activity\"--Provided by publisher.
Book
Data-driven prediction of the equivalent sand-grain height in rough-wall turbulent flows
This paper investigates a long-standing question about the effect of surface roughness on turbulent flow: What is the equivalent roughness sand-grain height for a given roughness topography? Deep neural network (DNN) and Gaussian process regression (GPR) machine learning approaches are used to develop a high-fidelity prediction approach of the Nikuradse equivalent sand-grain height $k_s$ for turbulent flows over a wide variety of different rough surfaces. To this end, 45 surface geometries were generated and the flow over them simulated at ${Re}_\\tau =1000$ using direct numerical simulations. These surface geometries differed significantly in moments of surface height fluctuations, effective slope, average inclination, porosity and degree of randomness. Thirty of these surfaces were considered fully rough, and they were supplemented with experimental data for fully rough flows over 15 more surfaces available from previous studies. The DNN and GPR methods predicted $k_s$ with an average error of less than 10 % and a maximum error of less than 30 %, which appears to be significantly more accurate than existing prediction formulae. They also identified the surface porosity and the effective slope of roughness in the spanwise direction as important factors in drag prediction.
Journal Article
Is it smooth or rough?
Discusses the properties of matter pertaining to whether an object is smooth or rough, defining both words and using examples to illustrate the differences.
Book
Linking energy loss in soft adhesion to surface roughness
A mechanistic understanding of adhesion in soft materials is critical in the fields of transportation (tires, gaskets, and seals), biomaterials, microcontact printing, and soft robotics. Measurements have long demonstrated that the apparent work of adhesion coming into contact is consistently lower than the intrinsic work of adhesion for the materials, and that there is adhesion hysteresis during separation, commonly explained by viscoelastic dissipation. Still lacking is a quantitative experimentally validated link between adhesion and measured topography. Here, we used in situ measurements of contact size to investigate the adhesion behavior of soft elastic polydimethylsiloxane hemispheres (modulus ranging from 0.7 to 10 MPa) on 4 different polycrystalline diamond substrates with topography characterized across 8 orders of magnitude, including down to the angstrom scale. The results show that the reduction in apparent work of adhesion is equal to the energy required to achieve conformal contact. Further, the energy loss during contact and removal is equal to the product of the intrinsic work of adhesion and the true contact area. These findings provide a simple mechanism to quantitatively link the widely observed adhesion hysteresis to roughness rather than viscoelastic dissipation.
Journal Article
Assessing and Mapping of Road Surface Roughness based on GPS and Accelerometer Sensors on Bicycle-Mounted Smartphones
The surface roughness of roads is an essential road characteristic. Due to the employed carrying platforms (which are often cars), existing measuring methods can only be used for motorable roads. Until now, there has been no effective method for measuring the surface roughness of un-motorable roads, such as pedestrian and bicycle lanes. This hinders many applications related to pedestrians, cyclists and wheelchair users. In recognizing these research gaps, this paper proposes a method for measuring the surface roughness of pedestrian and bicycle lanes based on Global Positioning System (GPS) and accelerometer sensors on bicycle-mounted smartphones. We focus on the International Roughness Index (IRI), as it is the most widely used index for measuring road surface roughness. Specifically, we analyzed a computing model of road surface roughness, derived its parameters with GPS and accelerometers on bicycle-mounted smartphones, and proposed an algorithm to recognize potholes/humps on roads. As a proof of concept, we implemented the proposed method in a mobile application. Three experiments were designed to evaluate the proposed method. The results of the experiments show that the IRI values measured by the proposed method were strongly and positively correlated with those measured by professional instruments. Meanwhile, the proposed algorithm was able to recognize the potholes/humps that the bicycle passed. The proposed method is useful for measuring the surface roughness of roads that are not accessible for professional instruments, such as pedestrian and cycle lanes. This work enables us to further study the feasibility of crowdsourcing road surface roughness with bicycle-mounted smartphones.
Journal Article
A comparison between profile and areal surface roughness parameters
Surface roughness has an important influence on the service performance and life of parts. Areal surface roughness has the advantage of accurately and comprehensively characterizing surface microtopography. Understanding the relationship and distinction between profile and areal surface roughness is conducive to deepening the study of areal surface roughness and improving its application. In this paper, the concepts, development, and applications of surface roughness in the profile and the areal are summarized from the aspect of evaluation parameters. The relationships and differences between surface roughness in the profile and the areal are analyzed for each aspect, and future development trends are identified.
Journal Article
Kinematics and improved surface roughness model in milling
Surface roughness has a significant influence on the mechanical properties and service life of a component. During face milling, surface roughness greatly varies in the tool step direction and can be controlled by using a surface roughness prediction model. However, the issues of accuracy and efficiency of surface roughness prediction models have not been adequately addressed. This study aims to address these research constraints. An improved surface roughness prediction model is proposed, taking into consideration the influences of insert back cutting and stepover ratio. First, the profile-forming mechanism is analyzed based on geometry and kinematics. Subsequently, an improved surface roughness prediction model is established. Thereafter, the influence of feed per tooth, stepover ratio, corner radius, and minor cutting edge angle on surface roughness are analyzed through numerical simulation. Finally, the experiment of face milling aerospace aluminum alloy 7075 is suggested to verify the improved model, and the Z-Map model is introduced for comparison. Results show that the surface roughness is nonlinear with a feed per tooth and stepover ratio, a monotonic variation with corner radius, and a minor cutting edge angle. The predicted values of the improved model and the Z-Map model for the
Rsm
are equal to the experimental values. However, the improved model reduces the prediction error of
R
a
from 11.2 to 4.2% in the non-overlapping compared with the Z-Map model and from 62.58 to 13.34% in the overlapping. In addition, the improved model performs better than the Z-Map model in predicting the shape parameters. This work serves as a significant reference for selecting and optimizing the milling parameters to enable machining quality control.
Journal Article
Review of single-point diamond turning process in terms of ultra-precision optical surface roughness
Ultra-precision machining is the recent realm subsequent to conventional precision machining processes. Recently, achieving nanoscale features on products has become important in manufacturing of critical components. One of the main objectives in advanced manufacturing of optics is to reach ultimately high precision in accuracy of optical surface generation. Through further development of computer numerical controlled machinery technology, single-point diamond turning (SPDT) has evolved rapidly and became a key step in the process chain of nano-machining. In SPDT, advanced and competitive technology for optical surface generation combined with ultra-precision fixtures and accurate metrological systems, high-precision surface machining with scales down to 1 nanometer, even less than 1 nanometer, are successfully achieved. Different engineering applications including medical, dental, defense, aerospace, computer science, and electronic components demand extreme smoothness and optical quality of the machined surfaces. However, there are limitations and drawbacks in SPDT process and surface generation using this technology. Different factors may significantly influence turning conditions, affect surface generation, and limit the outcome of the process. This paper attempts to provide a review of ultra-precision SPDT: technology and characteristics, manufacturing process, applications, machinable materials, and surface generation. Subsequently, influencing factors on surface generation are introduced and comprehensively discussed. Studying influencing factors on surface generation could enable setting optimized sets of machining factors and providing best possible machining conditions for generating high quality optical surfaces. Furthermore, limitations and drawbacks of standard structure SPDT process is discussed. Although a number of published studies have attempted to provide a good perspective of the SPDT process by looking into the effect of influencing factors on surface generation and existing limitations, more investigation needs to be undertaken to discover all destructive effects, origins, and influences in order to further extend the machinability of materials, reduce side effects, and improve the outcome of SPDT.
Journal Article
Rough Surface Aerodynamic Computation in Rarefied Gas Flow Applying the Solution of Inverse Problem
Most effective method to find the roughness parameters in rarefied gas flow is to calculate them from aerodynamic measurements, solving the inverse problem. The value of the main roughness parameter obtained from the solution of inverse problem is substantially higher (at least 1,25–1,5 times) than similar value of the same parameter measured from the profile diagrams. Thus, the effect of surface roughness in aerodynamic values of rough surface in rarefied gas flow is always significantly underestimated. First main reason of it is the low precision of roughness parameter measurements from the profile diagrams, and the second is based on usual lack of taking into account aerodynamic shadowing effect.
Journal Article
Superfluid dripping: a new analog for continuous time crystals
Time crystals refer to a state realized in an open system that spontaneously breaks time translation symmetry. There are ongoing discussions, both theoretical and experimental, regarding their realization and potential extensions, which highlights the need to explore new demonstrations in non-equilibrium systems. In this study, we demonstrate that the dripping of a superfluid can exhibit time crystallinity. We visualized pendant droplets of superfluid ⁴He dripping from various shaped surfaces and observed that the dripping period became consistently discretized when the edge of the droplet was free to move along the surface. This edge motion resulted in oscillation periods that were independent of the droplet’s volume, effectively eliminating the influence of variations in volume and flow rates on the timing of the dripping. Consequently, the dripping process became regular. The unimpeded movement of the droplet’s edge is a characteristic of superfluids and is facilitated by a preexisting superfluid thin film on the surface, which minimizes the effects of surface roughness and enhances the mobility of the edge. We examined the stability of the discretized periods as a function of input flow rate and concluded that the superfluid dripping system spontaneously broke continuous time translation symmetry, making it analogous to a continuous time crystal, but with multiple stable phases. In contrast, when the edge of the droplet was pinned, the dripping period displayed a wide distribution, resembling the irregular dripping behavior seen in classical fluids.
Journal Article