Fiat Surface Research Articles

Thermal creep model of rough fractal surfaces in contact: viscoelastic standard linear solid

Purpose – The purpose of this paper is to construct a continuous time series model to study the thermal creep of rough surfaces in contact.Design/methodology/approach – For normal loading, the contact between rough surfaces can often be modeled as the contact of an effective surface with a rigid fiat surface. A solution for the deformation of such equivalent surface, generated using fractal geometry, can be modified. However, in this study only the case of a single rough surface in contact with a rigid flat surface is considered. In the interface, the material is assumed to follow the idealized constitutive viscoelastic standard linear solid (SLS) model. Fractal geometry, through Cantor set theory, is utilized to model the roughness of the surface.Findings – An asymptotic time series power law is obtained, which associates the creep load, the buck temperature and the creep of the fractal surface.Originality/value – This law is only valid as long as the creep is of the size of the surface roughness. The mo...

DPSM Modeling for Studying Interaction Between Bounded Ultrasonic Beams and Corrugated Plates with Experimental Verification

Periodically corrugated structures play an important role in the field of vibration control and for designing structures with desired acoustic band gaps. Analytical solutions for corrugated plates are available for well-defined, smooth corrugations, such as sinusoidal corrugations that are not very common in the real world. Often corrugated plates are fabricated by cutting grooves at regular intervals in a flat plate. No analytical solution is available to predict the wave propagation behavior in such a periodically corrugated plate in which the equation of the plate surface changes periodically between a planar fiat surface and a nonplanar parabolic groove. This problem is solved here for steady-state case by a newly developed semianalytical technique called distributed point source method (DPSM), and the theoretical predictions are compared with the experimental results generated by reflecting a bounded 2.25 MHz ultrasonic beam by a fabricated corrugated plate. The main difference that is observed in the reflected beam profile from a flat plate and a corrugated plate is that the back-scattering effect is much stronger for the corrugated plate, and the forward reflection is stronger for the flat plate. The energy distribution inside the corrugated plate also shows backward propagation of the ultrasonic energy.

塑性流動現象を利用したアルミニウム合金鋳物の表面改質

Aluminum alloy castings meet a requirement of lightweight vehicles and attract a lot of attention. However they suffer from some defects such as porosity, segregation and others. Fusion processes used to modify the surface locally, lead to secondary defects like porosity and cracking in modified zone. In this paper, a new surface modification process, which uses friction phenomenon, is suggested. It is named as Friction Thermomechanical Process (hereafter referred as FTMP). In this process, a non-consumable rod is forced while rotating, against the substrate surface. The friction heat, generated at the interface between the rod and substrate, makes the substrate metal to undergo plastic deformation. The coarse cast microstructure at the substrate surface is continuously refined due to dynamic recrystallization. As a result, FTMP process is suitable for surface modification of aluminum castings. Cast defects were found to be eliminated in the surface zone of 2 mm depth where large fiat surface region. Modified zone showed refined microstructure and improved hardness.

Enhancement of Natural Convective Heat Transfer from Tall, Vertical Heated Plates.

An enhancement technique was developed for natural convection heat transfer from tall, vertical heated plate to water. Rectangular grid fins attached to the base plate were utilized as a heat transfer promoter. These grid fins redirect the high-temperature fluid ascending along the base plate toward the outside of the boundary layer and introduce the low-temperature ambient fluid toward the base plate instead. The heat transfer coefficients of thus-treated surfaces were measured and compared with a non-treated, fiat surface and a conventional surface with vertical straight fins. The highest performance was achieved for the experimental surfaces. In particular, the experimental surfaces with 5 mm-high, non-conducting grid fins and with 10 mm-high, conducting grid fins show 27% and 80% higher heat transfer coefficients compared to the turbulent heat transfer coefficients of the non-treated, fiat surface, respectively.

Experimental Study on Role of Tangential Force in Tactile Perception.

The role of the tangential force acting upon the finger during tactile perception was experimentally studied. Although the tangential force is usually dealt in regard to the smoothness of the surface and the sensation of a protrusion is often related to the stimulus in normal direction in haptic interface, we believe that the tangential force is indispensable to generate the sensation of a protrusion. We performed the experiment using a virtual protrusion for the investigation. The virtual protrusion is the sensation, as if there is a protrusion on the fiat surface, generated by using ultrasonic vibration. The experiments using five to ten subject showed that the sensation of the virtual protrusion is dosely related to the vibration conditions. Based on the experimental results, the mechanism of generating the sensation was dynamically analyzed. The results showed that the tangential force is important to perceive a protrusion clearly although the tangential force cannot make the sensation of a protrusion alone.

Analytical Solutions for the Unsteady Direct-Contact Melting on a Flat Surface. 1st Report. Isothermal Heating.

An approximate analytical solution for the initial transient process of close-contact melting occurring between a phase change material kept at its melting temperature and an isothermally heated fiat surface is derived. The model is so developed that it can cover both rectangular and circular cross-sectional solid blocks. Normalization of simplified model equations in reference to the steady solution enables the solution to be expressed in a generalized form that depends on the liquid-to-solid density ratio only. A selected result shows an excellent agreement with the previously reported numerical data, which justifies the present approach. The solution appears to be capable of describing all the fundamental characteristics of the transient process. In particular, dependence of the solid descending velocity on the density ratio at the early stage of melting is successfully resolved. The effects of other parameters except the density ratio on the transient behaviors are efficiently represented via the steady solution implied in the normalized result

兵庫県における被災ため池の特色—地形・地質,池の構造および老朽度・改修歴との関連を中心にして—

There are many farm ponds in the western part of Japan and they play important and essential roles in rice field agriculture. Hyogo Prefecture has 51, 679 farm ponds, the most of any Japanese prefecture. Of the farm ponds in Hyogo Prefecture, 1, 372 were damaged by the Southern Hyogo Prefectural Earthquake on January 17, 1995. The author attempted to clarify the geographical features of those damaged farm ponds. First research was conducted on relationships between damaged farm ponds in Hyogo Prefecture, excluding Awaji Island, and their topography, geology and structure. Damaged farm ponds are located on valley plains, terraces, small fans and boundaries between two topographies, for example, terrace and valley plain, terrace and back marsh, etc. The subsurface geology of damaged farm ponds are Holocene deposits, terrace deposits (Pleistocene deposits), Osaka Group (Pleistocene deposits), Kobe Group (Pleistocene deposits) and Arima Group (Miocene deposits). Furthermore, they are classified by structure as valley closed ponds (tani-ike in Japanese) that enclose valley plains with embankments and flat ponds (sara-ike) that are surrounded by large embankments on an almost fiat surface. Farm ponds located on valley plains of which the subsurface geology is Holocene deposits are very easily damaged during an earthquake, because their bottom gradients are steep and their grounds are weak or unstable. Next, the author conducted research for owners of damaged farm ponds to clarify their superannuation and history of repair. It was found that most severely damaged farm ponds were old and had not been repaired for many years. Few of the old ponds were only slightly damaged or undamaged. Farm ponds that were built more than 200 years ago and have not been repaired in the past 50 years are very susceptible to earthquake damage.

Mobile robot localization using a single rotating sonar and two passive cylindrical beacons

SummaryThis paper proposes a new method of estimating the position and heading angle of a mobile robot moving on a fiat surface. The proposed localization method utilizes two passive beacons and a single rotating ultrasonic sensor. The passive beacons consist of two cylinders with different diameters and reflect the ultrasonic pulses coming from the sonar sensor mounted on the mobile robot. The sonar sensor, again, mounted on a pan-tilt device then receives the reflected pulses while scanning over a wide area. The geometric parameter set of beaconis acquired from the sonar scan data obtained at a single mobile robot location using a new data processing algorithm. The presented algorithm is especially suitable for processing the sonar scan data obtained by ultrasonic sensor with wide beam spread. From this parameter set, the position and heading angle of the mobile robot is determined directly. The performance and validity of the proposed method are evaluated using two beacons and a single sonar sensor attached at the pan-tilt device mounted on a mobile robot, named LCAR, in our laboratory.

境界積分の変形公式と面積分法を結ぶ媒介式

Although the surface-integration method is fundamental way to calculate the illuminance by a flat surface source, its application to a complex source has been considered to be difficult, It, however, turned out that this problem can be solved by the perspective figure of the flat surface source on a horizontal picture plane in the height of v from illuminated plane is obtained by the via-perspective method.Then, the illuminance obtained from elementary area t·dtde of the perspective figure in polar-system is calculated by the surface-integration method, as shown in the following equations._??_Where E=the illuminance at calculating point, L=the luminance of the source, t=the radius vector to the elementary area, p=the radius vector to the contour, θ= the radious vector angle from the y axis, n=the intercept on the y axis, l= the distance between the elementary area and the calculating point.The above second intermediate equation obtained from the double-definite-integration when solved for t is transformable to the modiffied-cotour-integration formula, as shown in the third equation.Since this modiffied-contour-integration formula is applicable to all forms of the flat surface source, the application range of surface-integration method can extend even to all types of complex fiat surface source.

First‐ and second‐order smoothing method for rough surface scattering

There have been several recent investigations on rough surface scattering. They are directed at removing restrictions on the conventional perturbation and Kirchhoff approximations and also to devise a theoretical model to explain recent experimental data on backscattering enhancement. This paper presents a theory based on the diagram method of Bass et al. and the smoothing method of Watson and Keller. The rough surface is represented by an equivalent fiat surface as was done by Bass‐Fuks and Watson‐Keller. The first‐order smoothing solution is obtained from the Dyson and Bethe‐Salpeter equations. The coherent field is identical to the Watson‐Keller solutions. The first‐order solution is close to Ito's solution, but it is reciprocal. The second‐order smoothing solution has two terms. The ladder term is close to Ito's but the cross term exhibits some backscattering enhancement. Numerical examples for the one‐dimensional Dirichlet surface are shown and compared with related theoretical calculations. [Work su...

APPLICATION OF NON-INTEGRAL METHOD TO COMBUSTION AND NATURAL CONVECTION PROBLEMS

A straightforward, approximate “ non-integral” method has been introduced and used to solve the governing differential equations of transport problems with certain assumed profiles for the dependent variables. The method also requires that the integrals of the square of the error incurred by attempting to satisfy the governing equations be minimized. The methodology is illustrated by determining ( i) the burning rate of a fuel surface subject to forced convection, and ( ii) the natural convective heat transfer on a heated vertical fiat surface. The accuracy of this non-integral method is comparable to that of the conventional integral method. When the non-integral method is modified slightly ( by setting the total error equal to zero) the solution is identical to the integral solution.

Normal impingement of an axisymmetric turbulent air jet. Experiments.

In order to clarify the flow characteristics of a circular turbulent air jet impinging normally onto a fiat surface, the distributions of jet velocity and its turbulence intensity in the impingement region of the jet were measured in detail by hot-wire anemometry by changing the jet nozzle diameter, initial jet velocity and impinging height etc.. Consequently, those measurements were found to be similar to the velocity distribution in the free or wall jet region respectively, and also showed a reasonable agreement with the results calculated numerically assuming a new velocity distribution on the inflow boundary line of the impingement region.

An asymptotic result for the diffraction of plane waves propagating along a cylindrically truncated flat surface

An asymptotic result is obtained for evaluating the diffraction of a plane wave incident along a perfectly conducting fiat surface toward a drop in this surface. This drop is formed with a convex cylinder smoothly joined to the fiat section, thus creating a discontinuity in curvature at the join. The asymptotic result is also useful for analyzing the radiation of a source mounted on the fiat section of the conducting surface. Unlike a previously available solution which still requires a fair amount of numerical evaluation using a hybrid approach combining the moment method with the geometrical theory of diffraction, the computation of this asymptotic result is simple and efficient. Since this result is expressed in the simple format of the geometrical theory of diffraction, it is easily applied to solving more complicated diffraction problems. An application is found in the aperture-matched horn designs.

Pantographing Self-Adaptive Gap Elements

Abstract A pantographing self-adaptive gap element type contact strategy is presented. Due to the manner of its formulation, it can handle large deformations in the contact zone, contact initiation in a structure that has either positive or indefinite stiffness characteristics, kinematic and material nonlinearities, as well as self-adaptive load (time) stepping. Contact in pre- and post-buckling structures can be treated in this context. Several illustrative benchmark problems are given. These include coming into contact with a fiat surface, and involve large deformation kinematics and inelastic behavior as well as pre- and post-buckling stiffness characteristics.

Field Ion Microscopy of Contacts

A procedure for making contacts between a field ion microscope emitter tip and a fiat surface is described. Iron, tungsten, platinum, and iridium tips were contacted with glass, graphite, nickel, tungsten, gold, or platinum plates. The maximum permissible values for the contact pressure and the current density of the four metals were estimated from the contact load and the current through the contact point, respectively. A contact pressure or a current density above these critical values caused severe plastic deformation of a tip. The measured elastic limits of these metals are quite high and close to the theoretically expected values of the maximum shear stress. The current density through a Contact point is also higher than the permissible current density for the bulk materials. Contaminating surface layers on the nickel plates prevent damage to the tips due to cold welding and yet allow a very high contact current density. The transfer of materials by cold welding or by an arcing between the two metals is described.