B37 ゴルフボールとクラブの衝突特性 : 摩擦係数の影響(ボール特性)

This sheet deals with characteristics of the oblique impact system, which is composed of the golf ball and elastic supported clubface. The impact system is modeled by both a nonlinear spring and a nonlinear dashpot using Hertz's contact theory. This model is applied to the oblique impact system of golf ball and elastic supported clubface. The characteristics of the oblique impact were obtained by using this model. The results show that the spin rate increased in proportion to the angle of incidence and impact velocity and a coefficient of friction. Also, in the case of increase the tangential stiffness, the spin rate was decreased.

This sheet deals with characteristics of the oblique impact system, which is composed of the ball and flat surface. The impact system is modeled by both a nonlinear spring and a nonlinear dashpot using Hertz's contact theory. This model is applied to the oblique impact system of ball. The characteristics of the oblique impact were obtained by using this model. The results show that the spin rate increased in proportion to the angle of incidence and impact velocity. Also, in the case of increase the tangential stiffness, the spin rate was decreased and the angel of reflection was increased.

Changes in frictional coefficient with increased tendon surface tear—An experimental animal model

In order to study the influence of clamping force and friction coefficient on the stress distribution of drill pipe joint during the buckling process, the nonlinear contact problem and elastoplastic mechanical properties of Φ139.7mm × 9.17mm drill pipe were simulated by finite element analysis method in this paper, and the stress distribution and size of drill pipe joint during the buckling process were obtained. And the effect of clamping force and friction coefficient on the joint of drill pipe. It is found that the stress of drill pipe joint is mainly concentrated in the contact position of drill pipe and the stress value of drill pipe joint shows a trend of increasing. When the friction coefficient is 0.15 and the clamping force is 600KN, although there is stress concentration in the contact position between the clamp teeth and the drill pipe joint, it does not exceed the yield limit of the drill pipe joint, and no plastic deformation occurs. Through the simulation calculation, it is found that the maximum clamping force and the maximum torque are 1200KN and 81.9KN.m respectively. When the torque is fixed, the change of friction coefficient has a great influence on the maximum clamping force of drill pipe joint. With the increase of friction coefficient, the maximum clamping force of drill pipe joint decreases continuously, and the friction coefficient is inversely proportional to the maximum clamping force. The research in this paper enriches the understanding of the buckling process of punching pliers and provides a reference for the rational buckling of pipe string.

Problems connected with a shock interaction of a thin elastic cylindrical bar and an elastic sphere with an Uflyand-Mindlin plate of a finite size are considered. In enumerated problems, an impact process is accompanied by material local deformations and propagation of wave surfaces of a strong or weak discontinuity in elastic bodies coming in contact. The local deformations are taken into account in terms of the Hertz's contact theory, but the dynamic deformations behind the fronts of incident and reflected waves are determined by means of truncated power series with variable coefficients (what is known as ray series). These two types of deformations are mated on the contact region boundary. As the truncated ray series, as a rule, are not uniformly applicable in the whole region of the wave solution existence, then for their improvement the method of “forward-area” regularization is used which is based on a combination of the recurrent equations of the ray method with the method of multiple scales. The method of power series (ray method) allows one to find the main characteristics of the impact theory in an analytical form.

The ball-on-ring (BOR) test is an effective technique used to characterize the biaxial fracture strength of brittle materials. In particular, damages induced by wafer backgrinding process can be evaluated using the BOR test. It is difficult to measure directly the radius of contact area between the loading ball and a specimen, which is needed for stress determination by an analytic solution. In this study, parametric finite element analyses were performed to compare with known closed-form solutions. It was found that the effect of small loading area must not be ignored and that the radius of contact could be precisely determined using Hertz's contact theory. This can serve as a guideline to accurately obtain the fracture strength of a BOR specimen.

In this paper, photoelastic experimental hybrid method using external traction free boundary condition and using the relative equation of two stress functions in contact problems are developed. Their validities are confirmed through experiments and discussions Hertz's contact theory and two photoelastic experimental hybrid methods explained above are applied to the stress analysis of O-ring under 10% or 20% squeeze rate. Among them, the photoelastic experimental hybrid method using the relative equation of two stress functions in contact problems is most effective. When squeeze rates of O-ring are 20%, Maximum of absolute σ_x is greater than maximum of absolute σ_y by little. But they are almost equal to each other. Maximums of absolute τ_<xy> are 1/5 of absolute σ_x when squeeze rate of O-ring is 20%.

Our sense of touch is spatially focused and has a far lower bandwidth in comparison with visual sense that has the largest bandwidth. While most haptic studies utilize point interactions, resulting in a conflict between this low information bandwidth and relative complexity of virtual scene. In this paper, we investigate a novel multi-resolution force evaluation scheme of hybrid virtual models in a unified haptic interaction framework. Force contact model of tool-object interaction based on Hertz's contact theory is integrated in our work. Physical properties with different object materials expressed by Poisson's Ratio and Young's Modulus are involved to investigate most realistic perception during multi-resolution haptic interaction. The hierarchical impostor representation of surface and volumetric models are constructed, and the optimal performance based on cost and benefit evaluation at run time is employed to meet both the visual and hapic perceptual qualities. During this multi-resolution haptic interaction, our scheme adaptively determines the rendering mode using graphics and haptics impostors represented in the virtual environments. Our experimental results have demonstrated the satisfactory performance of proposed multi-resolution haptic interaction framework applicable for hybrid virtual models.

An effective method for calculating elasto-plastic contact pressure and contact patch size under elliptical, circular and line contact conditions

In industrial plants and pressurized equipment, leakage control and prevention are key tasks in preventive maintenance programs. The most critical element in these types of equipment is the seals. Several types of seals are used and the most popular are flat seals and O-rings. Two conditions affect the proper functioning of the seals: the mounting configuration and the initial loading parameters during operation. In this work, the analysis of the mechanical and leakage behaviour of the O-ring seal, when installed either in a cylindrical concave groove or in a rectangular one, is presented. Two finite element models were developed with Ansys software to study the behaviour of the assemblies in both cases when the clamping load is applied and when the assembly is pressurized. The results of the numerical models are compared to the analytical approach based on Hertz's contact theory. This study shows that the use of a cylindrical concave groove for mounting elastomeric O-rings can improve sealing in pressurized systems.

We report on the results of extensive computer simulation of the effect of deformation on the morphology of a porous medium and its fluid flow properties. The porous medium is represented by packings of spherical particles. Both random and regular as well as dense and nondense packings are used. A quasistatic model based on Hertz's contact theory is used to model the mechanical deformation of the packings, while the evolution of the permeability with the deformation is computed by the lattice-Boltzmann approach. The evolution of the pore-size and pore-length distributions, the porosity, the particles' contacts, the permeability, and the distribution of the stresses that the fluid exerts in the pore space are all studied in detail. The distribution of the pores' lengths, the porosity, and the particles' connectivity change strongly with the application of an external strain to the porous media, whereas the pore-size distribution is not affected as strongly. The permeability of the porous media strongly reduces even when the applied strain is small. When the permeabilities and porosities of the random packings are normalized with respect to their predeformation values, they all collapse onto a single curve, independent of the particle-size distribution. The porosity reduces as a power law with the external strain. The fluid stresses in the pore space follow roughly a log-normal distribution, both before and after deformation.

Estimating coke fracture toughness using acoustic emissions and changes in coefficient of friction during scratch testing

A study of the reciprocating-sliding wear performance of plasma surface treated titanium alloy

The induced earthquake recently has gained an increasing public awareness of environmental and safety issue. The earthquakes associated with fluid injection and extraction, reservoir impoundment and mining/rock removal have been extensively reported. Here, we reviewed injection induced earthquakes and their mechanisms from a view of rock mechanics. This review begins by briefly introducing the classification and the state-of-the-art research of induced earthquakes. From a view of rock mechanics, three fundamental mechanisms of induced earthquakes, i.e., pore pressure increase, stress change, and change in coefficient of friction, are introduced in details. Firstly, we discussed pore pressure increase due to fluid injection and reservoir impoundment, and explained earthquakes caused by fluid injection and related to reservoirs according to the Mohr–Coulomb failure criterion and effective stress law in the saturated rock. Secondly, we discussed stress change resulting from fluid extraction, temperature change, reservoir loading and quarry unloading. Thirdly, we investigated factors determining coefficient of friction, i.e., mineralogy, fluid pressure and temperature. Moreover, it is a remarkable fact that additional physical or chemical effects of fluids may lead to weakening of materials in fault zones owing to stress corrosion and stable slip, according to the rate and state friction law. Finally, we summarized and compared mechanisms of induced earthquakes that occurred in a variety of past human activities and projects, and recommended future potential means and scopes to investigate the mechanism of induced earthquakes.

Effect of sidewall modification in the determination of friction coefficient of vertically aligned carbon nanotube films using friction force microscopy