Wheel Shape Research Articles

A precision grinding method for screw rotors using CBN grinding wheel

Aiming at the high precision machining of screw rotors, a new grinding method for screw rotors using cubic boron nitride (CBN) grinding wheel is presented in this paper. Small electroplated CBN grinding wheel is firstly used to grind screw rotors. The mathematical model for the axial profiles of CBN grinding wheel is developed based on gear engagement theory. Taking the backlash of screw rotors and the coating thickness of CBN layer into consideration, the modification of the base body of the wheel shape is introduced into the design of the CBN grinding wheel. Wire cut electrical discharge machining low speed (WEDM-LS) was used to machine the base body of the CBN grinding wheel. The formed turning tools of the base body of CBN grinding wheel using WEDM-LS and the wheel shapes of CBN grinding wheel using the formed turning tool were performed. The CBN grinding wheels for the screw rotors were made to verify the validity and effectiveness of the presented method. The electroplated CBN grinding wheels were used to machine the screw rotors, and the machining experiments were performed. The data obtained in the experiments reach the fifth class of Chinese Standard GB10095-88.

Regular Surface Texture Generated by Special Grinding Process

Most of the methods for generating regular surface texture (RST) consist of shaping a set of regular grooves (cavities) arranged in a regular way. This paper presents possibilities for regular surface texture generation by so-called “pattern grinding” with the wheel prepared in a special way. The simple variant of the method involves grinding with the wheel having helical grooves. The grooves shaped on the work material are the result of specific wheel surface reproduction. The ratio between work-material feed and wheel speed is an important factor, determining the layout of the grooves generated on the work-material and the shape of the groove sides. Surface texture consists of two components: deterministic, resulting from the nominal wheel active surface, and random, resulting from the random shape and arrangement of abrasive grains. The limited contribution of the random component of surface texture is discussed based on the ratio between the undeformed chip thickness and the sizes of the grooves. Kinematical analysis of the wheel reproduction process is performed for description of nominal surface texture. Experimental results of flat and cylindrical surfaces, obtained with pattern grinding are also provided. Two critical values of the ratio between work-material feed and wheel speed were derived, and three ranges of this ratio are discussed. The kinematical approach provided relationships between input data of the process (wheel shape and grinding parameters) and nominal groove dimensions and groove layout. The geometrical characteristics of the work-material nominal surface texture are presented for each of the three types of surface texture. It is important to ensure that the work feeds are greater than the lower critical value. For achievable work feeds the shape of the sides of the grooves is cycloid. Experiments revealed the limited contribution of the random component of the surface structure of the work material. Random arrangement of abrasive grains is important only at local (micro-) level and affects the roughness of groove bottoms, while the dimensions and arrangement of the grooves are affected only to a minimal degree.

Design and analysis of low-stress and low-noise lightweight railway wheel

The finite-element and boundary-element methods were applied to develop the low-stress and low-noise lightweight railway wheel. First, stress analyses for the existing wheels under the condition of drag braking or track loading were performed. Following these analyses, a design methodology was developed and applied, leading to the development of new plate shapes of the wheel, whose stresses generated were lower than those of conventional wheels. Candidate plate shapes were selected based on the analyses. Next, eigenvalue analyses and transient dynamic analyses were carried out for the wheels. At the same time, to verify the analytical results, these wheels were manufactured and experiments implemented. Finally, acoustic analyses were performed and results compared with those obtained by field measurements. From this study, a new plate shape of the lightweight railway wheel was obtained, which reduces the radiated noise as well as the maximum stresses generated in the plate region to a remarkable extent.

Development of Wheel Surface Forming Technique for Ultra-smoothness Vertical Surface Grinding Method (2nd Report)

In the ultra-smoothness vertical grinding method developed previously, the wheel surface conditions are found to influence largely on ground workpiece surface. Thus the building of wheel surface forming technique is important. In the 1st report, from the point of view, the change of ground workpiece surface and wheel surface with grinding process of silicon carbide ceramic by using #140 resin bonded diamond wheel is examined and discussed. In the report following the 1st report, first of all, the change of macroscopic wheel shape in addition to surface conditions such as cutting edge wear, depth of chip pocket and so on with grinding time is examined. It is cleared that the wheel wear begins to occur at wheel outside edge and proceeds to wheel inside. Wheel life is ascertained to occur due to the contact of workpiece with bond, which is caused from the radial wheel wear. On the basis of the results, trued wheel shape for low rate of radial wheel wear is discussed. The sharp edge in the wheel outside shape is found to be effective for long wheel life in grinding of silicon carbide ceramic.

Effect of Chain Wheel Shape on Crank Torque, Freely Chosen Pedal Rate, and Physiological Responses during Submaximal Cycling

The development of noncircular chain wheels for the enhancement of cycling performance has been in progress for a long time and continues apace. In this study we tested whether submaximal cycling using a non-circular (Biopace) versus a circular chain wheel resulted in lower peak crank torque at preset pedal rates as well as resulting in lower pedal rate and metabolic response at freely chosen pedal rate. Ten trained cyclists (mean+/-SD: 27+/-3 years of age, 182+/-4 cm tall, 77.5+/-7.0 kg of body mass, and peak oxygen uptake of 61.7+/-4.4 ml kg(-1) min(-1)) cycled with a Biopace and a circular chain wheel at 180 W at 65 and 90 rpm for recording of crank torque profiles, and at their freely chosen pedal rate for recording of pedal rate and metabolic response, including oxygen uptake and blood lactate concentration. Crank torque profiles were similar between the two chain wheels during cycling at preset pedal rates. During cycling at the freely chosen pedal rate (being 93+/-6 and 93+/-4 rpm for the Biopace and circular chain wheel, respectively), blood lactate concentration was significantly different between the two chain wheels, being on average 0.2 mmol l(-1) lower with the Biopace chain wheel. A musculoskeletal simulation model supported the idea that a contributing factor to the observed difference in blood lactate concentration may be slightly reduced muscle activity around the phase where peak crank torque occurs during cycling with the Biopace chain wheel. In that particular phase of the crank revolution, the observed slightly lower muscle activity may result from larger transfer of energy from the legs to the crank.

Modeling and Analysis of Triangle Flexible Hinge

The triangle flexible hinge as a rotational element can be used to construct flexible module or compliant mechanism with better performance, such as wheel shape hinge and butterfly hinge.Building an accurate force-bearing model and analyzing its load-displacement characteristic is the key to designing a complicated hinge or mechanism.Based on an approximate cantilever model, an accurate rotation angle model of triangle flexible hinge under simultaneous actions of bending moment, tangential force and axial force is built.The calculation formula for axis drift without approximation is obtained, and a practical axis drift model is derived.The rotation angle and axis drift models all concisely represent the load-displacement relationship.The accuracy of built models is verified through finite element analysis.

A fast time-domain model for wheel/rail interaction demonstrated for the case of impact forces caused by wheel flats

The prediction of impact forces caused by wheel flats requires the application of time-domain models that are generally more computationally demanding than are frequency-domain models. In this paper, a fast time-domain model is presented to simulate the dynamic interaction between wheel and rail, taking into account the non-linear processes in the contact zone. Track and wheel are described as linear systems using impulse-response functions that can be precalculated. The contact zone is modelled by non-linear contact springs, allowing for loss of contact. This general model enables the calculation of the vertical contact forces generated by any kind of roughness excitation between wheel and rail. Here, the model is adapted to the excitation caused by wheel flats by introducing the irregular wheel shape as a form of extreme roughness. A brief parameter study is presented to demonstrate the functioning of the model. The results from the model are discussed and compared with results from literature.

626 鉄道用低応力・低騒音軽量車輪の開発

Finite element method and boundary element method were applied to develop the low-stress and low-noise lightweight wheel. A design methodology was developed and applied, leading to the development of new plate shapes of wheel whose stresses generated were lower than those of conventional corrugated wheels. Candidate plate shapes were selected based on the analyses. Next, transient dynamic analyses were carried out for the wheels. At the same time, to verify the analytical results, these wheels were manufactured and experiments were implemented. Finally, sound analyses were performed and results were compared with that obtained by field measurements. From this study, a new plate shape of lightweight railway wheel was obtained that reduces the radiated noise as well as the maximum stresses generated in the plate region.

Precise profile of grinding wheel and interference elimination for high-lead ball-nut

In order to solve interference between wheel shaft and internal surface of ball-nut in the process of high-lead ball-nut grinding, a method for Gothic arc grinding of high-lead ball-nut is presented. The presented method is based on the theoretical fundament of helicoids shape grinding. According to the principle that the contact points of the grinding wheel and the internal surface of the ball-nut form a space curve, a calculation model is established for surface calculation of the grinding wheel, by which collision can be avoided. The method is applicable to calculate the profile of grinding wheel in any angle, as well as to choose the best process parameters for the shape grinding. This method is simple and convenient for modification of grinding wheel shape when it needed. Lastly, taking a high-lead ball-nut as an example, the validity of the method is approved by grinding wheel optimum profile calculation and error analyze of the results.

Diagnostic Pitfalls of Spinal Echinococcosis

To critically examine and elucidate the diagnostic pitfalls of spinal echinococcosis. SUMMARY OF PATIENTS: From October 1957 to June 2006, 25 consecutive cases drawn from 5721 cases of echinococcosis were collected in the First Affiliated Hospital of Xinjiang Medical University. The selected cases comprised 11 males and 14 females; all were treated with debridement operations. The average age was 28.3 years (15 to 56 y). The average duration of infestation with spinal hydatid disease was 3.2 years (0.5 to 12 y). Nineteen of the 25 cases underwent magnetic resonance imaging (MRI) scanning, which identified 17 out of 19 cases as having hydatid disease. The lesion was located in the cervical vertebrae in 3, the thoracic vertebrae in 11, the lumbar vertebrae in 5, and the sacrum in 6 cases. Eighteen cases were available for follow up; the period ranging from 0.5 to 15 years with an average of 3.6 years. The Casoni test was performed in 15 cases and was positive in 12 patients (80%). In addition, 4 cases were positive in all of the so-called 8 tests of immunodiagnostic methods. MRI examination was performed in 19 of the 25 cases and 17 of these were diagnosed as having spinal hydatid disease (89.47%). The typical MRI appearance is that of a multilocular cyst and the signal of the parent cyst is similar to that of muscle and higher than that of secondary cyst in the T1Weighted image (WI). The signal of the secondary cyst is similar to water, either located in or overflowing or adjacent to the parent cyst. Both the parent and the secondary cysts showed high signals in the TW1 with either rose or wheel shapes. In the 18 cases, which were reviewed, 11 cases had relapsed (61.11%). Although x-ray or computed tomography images of spinal echinococcosis are similar to tuberculosis, metastases, giant cell tumors, or cysts of the bone, MRI shows distinctive diagnostic features of spinal hydatid disease. Serologic examinations are important to confirm the correct diagnosis.

Development of Low-stress and Low-noise lightweight Railway Wheel

Finite element method and boundary element method were applied to develop the low-stress and low-noise lightweight wheel. First, stress analyses for the existing wheels under the condition of drag braking and track loading were performed. Following these analyses, an optimization methodology was developed and applied, leading to the development of new plate shapes of wheel whose stresses generated were lower than that of conventional wheels. Candidate plate shapes were selected based on the analyses. Next, eigenvalue analysis and transient dynamic analysis were carried out for the wheels. At the same time, to verify the analytical results, these wheels were manufactured and experiments were implemented. Finally, sound analyses were performed and results were compared with that obtained by field measurements. From this study, a new plate shape of lightweight railway wheel was obtained that reduces the radiated noise as well as the maximum stresses generated in the plate region.

307 転動騒音に影響する在来線車輪の形状評価

307 転動騒音に影響する在来線車輪の形状評価

Review of research into wheel/rail rolling noise reduction

Rolling noise is the main source of noise from railway operations at conventional speeds, and even at 300 km/h, it is at least as important as aerodynamic noise. In the last decade, several large research projects have been carried out across Europe with the aim of reducing wheel/rail rolling noise at source. Much of the research has concentrated on freight traffic as this has been perceived as the major source of nuisance because of its relatively high noise levels and the operational necessity of running at night. The solutions considered have included means of reducing wheel and rafl surface roughness, improved wheel and track designs for low noise generation, and local shielding applied to the vehicle and track. These have demonstrated a number of successful concepts, including wheel shape optimization, wheel damping, rail damping, bogie shrouds, low barriers, and modified tread braking. This article summarizes the main results obtained and discusses the prospects for implementation of the technology in practice.

Multi-disciplinary optimization of railway wheels

A numerical procedure for multi-disciplinary optimization of railway wheels, based on Design of Experiments (DOE) methodology and automated design, is presented. The target is a wheel design that meets the requirements for fatigue strength, while minimizing the unsprung mass and rolling noise. A 3-level full factorial (3LFF) DOE is used to collect data points required to set up Response Surface Models (RSM) relating design and response variables in the design space. Computationally efficient simulations are thereafter performed using the RSM to identify the solution that best fits the design target. A demonstration example, including four geometric design variables in a parametric finite element (FE) model, is presented. The design variables are wheel radius, web thickness, lateral offset between rim and hub, and radii at the transitions rim/web and hub/web, but more variables (including material properties) can be added if needed. To improve further the performance of the wheel design, a constrained layer damping (CLD) treatment is applied on the web. For a given load case, compared to a reference wheel design without CLD, a combination of wheel shape and damping optimization leads to the conclusion that a reduction in the wheel component of A-weighted rolling noise of 11 dB can be achieved if a simultaneous increase in wheel mass of 14 kg is accepted.

Nonlinear Stability and Bifurcation of Multi-D.O.F. Chatter System in Grinding Process

The nonlinear chatter in grinding machine system is discussed analytically in the paper. In higher speed grinding process, the self-excited chatter vibration is mostly induced by the change of grinding speed and grinding wheel shape. Here the grinding machine tool is viewed as a nonlinear multi-D.O.F. autonomous system, in which hysteretic factors of contact surfaces are also introduced. Firstly, the DOFs of the above system are reduced efficiently without changing its dynamic properties by utilizing the center manifold theorem and averaging method. Then, a low dimensional system and corresponding averaging equations are obtained. The stability and bifurcation of chatter system are discussed on the base of deduced averaging equations. It is proved that chatter occurs as a Hopf bifurcation emerging from the steady state at the origin of system. The theoretical analyses on the multi-DOF chattering system will lead to further understanding of the nonlinear mechanisms of higher speed grinding processes.

Studies on CCD On-Line Detection in Curve Grinding

An on-line image measurement system for curve grinding was schemed out according to the working process. Because of interaction between detection precision and field of view, it is difficult to realize high detection precision at a large field of view. In order to settle this problem, a detection method based on circular tolerance zone was presented according to grinding process and wheel shape. Real-time images of work piece can be gathered while using synchronal control and outer trigger technology. Using curve fitting method, the work piece image edge can be located to sub-pixel values. Experiments show that the proposed method in this paper is effective, and its detection precision and results are reasonable.

Fabrication process and system for neutron refractive optics

The authors developed a new fabrication process and system for neutron refractive optics, and propose a new design for Fresnel lens refracting cold-neutron beam in this paper. Applying the ultraprecision electrolytic in-process dressing (ELID) micro-grinding technique using cast-iron-bonded diamond wheels with edges sharpened by electrical and mechanical processes, the authors successfully fabricated the required element with sharp and smooth V-faced Fresnel structures using quartz glass or MgF 2 glass. The relationship of the form accuracy of the fabricated Fresnel lens and changes in grinding wheel shape is also discussed.

Fabrication process and system for neutron refractive optics

The authors developed a new fabrication process and system for neutron refractive optics, and propose a new design for Fresnel lens refracting cold-neutron beam in this paper. Applying the ultraprecision electrolytic in-process dressing (ELID) micro-grinding technique using cast-iron-bonded diamond wheels with edges sharpened by electrical and mechanical processes, the authors successfully fabricated the required element with sharp and smooth V-faced Fresnel structures using quartz glass or MgF 2 glass. The relationship of the form accuracy of the fabricated Fresnel lens and changes in grinding wheel shape is also discussed.

Investigation of pre-dressing time for ELID grinding technique

The grinding wheel topography and the macroscopic wheel shape generated by truing and dressing are one of the major concerns of the manufacturers of high accuracy component parts. Decreasing the dressing time is always desirable as it may reduce the processing time and production costs. A new dressing technique—electrolytic in-process dressing (ELID)—has attracted special interest recently because eliminates the conventional dressing times while it increases the ground surface quality. The primary purpose of the ELID is the generation or regeneration on the desired topography of the grinding wheel that is necessary for assuring the quality of the finished part. Excellent smooth surfaces can be achieved with the use of extremely fine abrasives. This paper presents the results of a theoretical and experimental study of the pre-dressing time for an ELID setup applied to a CNC surface-grinding machine. The theoretical analysis of the pre-dressing time was completed based on the fundamental electrochemical laws. The model of Hong and James concerning the electric field or current density distribution around a diamond particle embedded in a metal anode during ELID was employed. In parallel, a predictive model of the pre-dressing time values was built on the basis of recorded experimental data. Good correlation of the predicted values given by the theoretical and the experimental model was found. An optimization of the pre-dressing time for the considered case was performed in order to improve the efficiency and productivity of the process.

The Effect of Wheel Velocity and Shape on Rotating Airflow in Super-High-Speed Grinding

The Effect of Wheel Velocity and Shape on Rotating Airflow in Super-High-Speed Grinding