Steel Balls Rolling Research Articles

Numerical and experimental study for process improvement of cross-wedge rolling of bearing steel balls

The uniaxial compression experiments were conducted on GCr15 bearing steel to obtain the flow stress curves under hot deformation conditions. Based on the results of uniaxial compression experiments, finite element modeling was conducted on the cross wedge rolling (CWR) of GCr15 bearing steel balls, and numerical simulation was conducted using Simufact Forming 16.0. The results show that the distribution of effective strain of existing CWR steel balls is uneven, which may lead to uneven quality of steel balls. In addition, the three principal stresses at the center of the steel balls are all tensile stresses, and the effective stress at the center of the middle ball is relatively large, which can easily induce central defects. Moreover, different diameter billets were used for steel balls rolling experiments. It can be seen that when the die cavity is underfilled with billet, the rolled steel balls have no central defects. When the die cavity is fulfilled with billet, there is central piercing appearing at the middle ball, while the side balls have no obvious central defects. Finally, the paper proposes the method of even numbered ball rolling (ENBR) which starts from the middle connector to improve the CWR process of steel balls.

A Study on Multiple Tuned Liquid Column Ball Dampers (MTLCBDs)

Tuned liquid column ball dampers (TLCBDs) are a relatively new type of liquid dampers in which the motions of liquid in a U-shaped tube counteracts the forces acting on the structure. Damping in the oscillating liquid is introduced through a steel ball rolling by the liquid passage. The tube and steel ball in a single TLCBD-system may acquire enormously large dimensions. One way to decrease the size, and perhaps the total costs, is to replace a single-TLCBD with a multiple (M)-TLCBDs of smaller dimensions. Current literature lacks to address the governing equations of an M-TLCBD and its application in wind response mitigation of tall buildings. In this paper, the governing equations of motion for an MTLCBD-system has been developed. Next, the dynamic response of a tall building, equipped with various MTLCBDs, to harmonic wind excitations is investigated. The influence of different design parameters such as mass ratio, length ratio, and the number of individual dampers on the response mitigation efficiency of MTLCBDs has been studied. Overall, the performance of a MTLCBD is found to be sensitive to the variations in the design parameters mentioned above.

Effects of solid viscoelasticity on elastohydrodynamic lubrication of point contacts

Dry and lubricated highly deformed contacts appear in engineering, physics, and bio-(fluid)mechanics, with increasingly many applications where the soft materials can exhibit viscoelastic behaviour. In this work, the viscoelastic solid lubricated point contact problem has been studied theoretically and experimentally. An efficient visco-elastohydrodynamic lubrication (VEHL) numerical algorithm has been developed by implementing a novel viscoelastic deformation equation. The relevant dimensionless parameters of the VEHL problem are identified and a parameter study is presented showing the effect of solid viscoelasticy on the pressure and film thickness in the conjunction. In addition experimental results are presented for film thickness measurements in configurations of a PMMA ball rolling against a glass disc, and a steel ball rolling against a glass disc using optical interferometry. Finally the scaling of the pressure and film profiles in the inlet and outlet regions to the contact have been studied, investigating self similarity of the pressure and film solution in these regions. The results presented provide a good framework for the understanding and interpretation of viscoelastic solid effects on the film and pressure behavior in highly deformed (soft) lubricated contacts.

Experimental and numerical study of cold helical rolling of small-diameter steel balls

Cold helical rolling (CHR) is one of the most effective ways to produce small-diameter steel balls. In this study, one kind of work hardening model was established and implemented into Simufact 15.0 to investigate the work hardening phenomenon in the cold forming process. Firstly, based on the helical rolling theory, a set of finite element (FE) simulations was developed. The influence of CHR parameters, including the starting height of convex rib, forming area length, and rolling inclination angle, on the forming process was studied via simulation. Furtherly, the CHR process experiment and FE simulation were carried out; the results showed that the FE simulation was in good agreement with the experimental results and consistent with the predicted value of the theoretical calculation. Finally, the evolution of effective strain, effective stress, rolling force, work hardening, and microstructure during the cold helical rolling of Φ 5.2-mm steel balls was investigated via FE. As a result, the evolution trend of hardness was consistent with that of dislocation density, indicating that the model is credible. Besides, the microstructure of the steel ball at different positions further verified this point.

Dynamic Behavior Analysis of Feed Drive System Using Linear Guideways with Different Ball Diameters

The feed drive system for machine tool consist of rolling elements such as ball screw and linear guides. It is well known that in the positioning of linear guides using steel ball rolling, the contact surface has nonlinear spring characteristics. This phenomenon is deteriorating the accuracy of the machine tool. In this study, we have manufactured a feed drive system in which the physical contacts are only linear guides by using a linear motor as actuator. At first, we measured the responses to some fine feed amount for feed drive system. Next, the same experiment was performed by changing the linear guideways. This paper presents the transition of nonlinear spring characteristic region by considering the response to linear guides under different conditions.

Statics analysis and experimental study on the bi-stable self-amplifying force clutch of hybrid electric vehicles

At present, hybrid electric buses are mainly used for urban buses, which work in two conditions for a long time, such as clutch separation and clutch engagement, but the mono-stable clutch cannot meet the needs. According to the working demands of the clutch, this thesis puts forward a new bi-stable clutch configuration used in hybrid electric vehicles, and then its working principle is described, which realizes self-amplifying force effect and solves self-locking defects through the structure of double-disc steel ball rolling groove mechanism. Based on statics analysis theory, the statics analysis was carried out on the back-and-forward rotating pressure plate, the clutch’s rear end cover and master pin. Then a bi-stable clutch test bed is set up in order to conduct the clutch’s bearing torque, separation thoroughness, heat load test and service life test. Its conclusion provides a good foundation for the further optimal design of the bi-stable clutch.

Coulomb's law for rolling friction

Measurements are presented on the coefficient of rolling friction for steel balls rolling on hard surfaces. Two simple techniques are described, both suitable for use in a student laboratory, and both capable of measuring friction coefficients as small as 0.0001. The coefficient of rolling friction depends strongly on ball radius, an effect first observed by Coulomb in 1785. In this work, the dependence on ball radius is found to be similar to that observed by Tabor in 1955 using steel balls on rubber and on soft metal surfaces. However, it is found that rolling friction on a hard surface is due primarily to surface roughness rather than the hysteresis losses commonly associated with soft balls or soft surfaces. It is also found that the coefficient of rolling friction is approximately proportional to rolling speed.

A nonlinear state-dependent model for vibrations excited by roughness in rolling contacts

A state-dependent method to model contact nonlinearities in rolling contacts is proposed. By pre-calculation of contact stiffness and contact filters as functions of vertical relative displacement, a computationally efficient modelling approach based on a moving point force description is developed. Simulations using the state-dependent model have been analysed by comparison with measurements. Results from the investigated case – consisting of a steel ball rolling over a steel beam having two different degrees of roughness – show good agreement between nonlinear simulations and measured beam vibrations. The promising results obtained with the proposed method are potentially applicable to wheel–rail interaction and rolling element bearings.

Experimental validation of a simplified model for rolling isolation systems

SUMMARYRolling isolation systems (RISs) protect mission‐critical equipment and valuable property from earthquake hazards by decoupling the dynamic responses of vibration‐sensitive objects from horizontal floor motions. These responses involve the constrained rolling of steel balls between bowl‐shaped surfaces. The light damping of steel balls rolling between steel plates can be augmented by adhering thin rubber sheets to the plates, thereby increasing the rolling resistance and decreasing the displacement demand on the RIS. An assessment of the ability of lightly‐ and heavily‐damped RISs to mitigate the hazard of seismically induced failures requires high‐fidelity models that can adequately capture the systems' intrinsic nonlinear behavior. The simplified model presented in this paper is applicable to RISs with any potential energy function, is amenable to both lightly‐ and heavily‐damped RISs, and is validated through the successful prediction of peak responses for a wide range of disturbance frequencies and intensities. The validated model can therefore be used to compute the spectra of peak floor motions for which displacement demands equal capacity. These spectra are compared with representative floor motion spectra provided by the American Society of Civil Engineers 7–10. The damping provided by rolling between thin viscoelastic sheets increases the allowable floor motion intensity by a factor of 2–3, depending on the period of motion. Acceleration responses of isolation systems with damping supplied in this fashion do not grow with increased damping, even for short‐period excitations. Copyright © 2013 John Wiley & Sons, Ltd.

FEM Analysis of Helical Rolling of Steel Balls

In this paper, two helical rolling processes for producing balls with a diameter of 40 mm are compared – the traditionalrolling and wedge rolls rolling. The process analyses were performed using Simufact.Forming, a FEM-based software program, and the same process parameters were applied in the analyses. Based on the calculations results (the distributions of effective strain, damage criterion, roll wear as well as the variations of forces and rolling moments during the processes), advantages and disadvantages of the considered rolling methods could be presented.

Tuned rolling-ball dampers for vibration control in wind turbines

With wind turbines growing in size and cost, it is necessary to reduce their dynamic responses and improve their fatigue lifetime. A passive tuned-mass damper (TMD) is a very efficient solution for vibration control in structures subjected to wind excitations. In this study, a tuned rolling-ball damper characterized by single or multiple steel balls rolling in a spherical container is proposed to be mounted on the top of wind turbines to reduce the wind-induced vibration. A 1/20 scale shaking table model was developed to evaluate the control effectiveness of the damper. The wind-induced dynamic responses of the test model with and without TMD were obtained from the shaking table tests. The test results indicated that the rolling-ball dampers could effectively suppress the wind-induced vibration of wind turbines. The damper with three balls in one container had better control effectiveness than that with only one ball because of the impact effect and the rolling friction. The control effectiveness of the damper cannot be improved further when the number of balls is increased beyond a certain point.

New methods of steel ball rolling

The paper presents three new ball forming methods which have been developed at Lublin University of Technology, Poland. These methods include: cross-wedge rolling (CWR), multi-wedge cross rolling (MWCR), and cross rolling with upsetting (CRWU). The processes have been discussed using an example of a simultaneous forming of four balls with a diameter of 22 mm. The tools securing the forming processes of semi-finished balls are presented. Taking advantage of the FEM, the courses of rolling processes as well as distributions of temperature and strain in obtained products are shown. Conducted in laboratory conditions, the rolling tests have proven that the balls produced by the developed rolling methods meet the requirements for ball mill grinding media.

Dynamics and Control of the Shoot-the-Moon Tabletop Game

The classic tabletop game Shoot-the-Moon has interesting dynamics despite its simple structure, consisting of a steel ball rolling on two cylindrical rods. In this paper, we derive the equations of motion for Shoot-the-Moon using a Lagrangian approach and examine the underactuated, nonlinear, and nonholonomic dynamics. Two ball position controllers are designed, one using a local linearization and another using the nonlinear dynamics. Simulations of both controllers are performed, showing that the ball converges to the setpoint position for the linearized controller and continuous signals can be tracked by the nonlinear controller. Finally, the experimental results are presented for the nonlinear controller applied to a physical implementation of Shoot-the-Moon. The effect of the nonholonomic constraint relating the ball’s linear and angular position is demonstrated. This system has rich dynamics that can provide a challenging problem for control design and serve as a new educational example.

Vladimír Vand (1911–1968): Pioneer of Computational Methods in Crystallography

The Czech scholar Vladimír Vand (1911–1968) substantially enriched many areas of science, from crystallography and astrogeology to computing. His most notable contribution to computing is the invention of a mechanical computer containing approximately 1 million little steel balls rolling through many guide bars. Using this research, Vand collaborated with William Cochran and Francis Crick on the early analysis of the structure of helix molecules.

Experimental investigations of a multi-span flexible structure subjected to moving masses

This paper is concerned with the dynamic response of multi-span flexible structures excited by moving masses. A four-span beam on simple supports was built and the deflections at eight locations along the structure produced by one or two steel balls rolling over it at various speeds are measured by laser displacement transducers. The travelling speeds of the moving masses are also measured by laser sensors. A dynamic (theoretical) model of the structure is established and a statistical assessment of the error variability presented. The numerical results are compared with the experimental results and good agreement is achieved.

Seismic Tests and Numerical Modeling of a Rolling-ball Isolation System

For the seismic isolation of light structures, the use of laminated rubber bearings is neither economical nor, for most cases, technically suited. For the isolation of this type of structure a new system, consisting of steel balls rolling on rubber tracks, has been developed at TARRC (Tun Abdul Razak Research Centre). This article presents the results of experimental tests carried out for the characterization of the behavior of this new device. A numerical model is also proposed that can be used to assess the seismic response of structures with this isolation system. Comparison of the predictions of the numerical model with the experimental data shows that the model is adequate to perform the correct assessment of the seismic response of isolated structures. The results of the experimental campaign of shaking-table tests, as well as the numerical simulations, show that there is an effective reduction of the acceleration levels induced in the isolated structures.

Impact failure analysis of re-circulating mechanism in ball screw

A ball screw driven mechanism is a major component in high-speed/high-precision transmitting systems. In such a mechanism, the return tube has been designed to provide the path for a steel ball rolling in screw grooves. As the driven shaft in the mechanism operates at high rotating speed, forces caused by the impact activity between the steel ball and return tube may generate high stresses and cause damage to the return tube after some significant service times. In order to understand the fracture conditions in the return tube, an impact-contact formula is developed and the transient behavior is investigated based on the finite element method in this paper. From results obtained here, it is shown that the rotational speed of the ball screw may affect the service life of the return tube significantly. Factors that affect the service life of the re-circulating mechanism are then described in detail. Further suggestions for the improvement of the return tube in the design/fabrication processes are also proposed in the final part of this paper.

The surface geometry of rollers with skew rolling of steel balls

The ball shaping process is considered from a geometric viewpoint as a meshing pair of conjugate surfaces at the precise rolling stage. This viewpoint offers a simple method and procedure for determining the groove design of each forming roll in the skew rolling process of steel balls. Based on the envelope theory, a shape design of the forming roll is a composite of two helical grooves with constant pitch and variable pitch. Through this method, the mathematical model of the forming rolls for skew rolling, which can be used to design and manufacture a skew roller for manufacturing steel balls, can be derived and simulated. Finally, the required cutter path is provided for a spherical-end cutter in the manufacturing process. The size of the spherical-end cutter may be identical with or smaller than that of the steel ball.

Study on the method for groove design in the helical rolling of steel balls

Based on two conventional methods, this paper introduces a new method of variable lead of the dual edges of a grooved rib (the CZQ method) for groove design in the cold rolling of steel balls. It is shown by the results of experiment that the shape of the ball is better and the material utilization is greater when dies designed by the CZQ method are used in cold rolling. Thus the use of the new method enabled an improvement to be made in the helical-rolling process.

The Ball and Beam Control Experiment

The construction and use of an electromechanical laboratory control experiment is described. The system, which involves a steel ball rolling on a pivoted beam, presents a mechanically simple system which is nevertheless an illuminating exercise in feedback control.