Hollow Roller Research Articles

Study on the Performance of Wollastonite Modified PTFE Composite Material

In the research, Polytetrafluoroethene (PTFE) is applied in a newly elastic composite cylindrical roller bearing, i.e. PTFE is modified into the traditional hollow cylindrical roller bearing so as to improve the vibration, wearing properties and life span of the roller bearing. The results show that bearing capacity of the same dimension of WF/PTFE composite materials is higher than that of WP/PTFE composite materials. Small dimension of WF-PTFE composite materials has the best wearing properties under light load conditions; large dimension of WF-PTFE composite materials has better bearing capacity and wearing properties than small dimension of WF filler under heavy load conditions. Compare to traditional method, Rolling stress improves by filler PTFE materials using our method reduces by 17.1% under light load conditions and reduces by 27.7% under heavy load conditions. The research provides basis for the modified material of the elastic composite cylindrical roller bearing.

Parameters of Force Interaction of Elements the Wave Transmission with Intermediate Rolling Bodies in Geokhd's Transmission

Parameters of interaction forces arising in the harmonic gear drive with a hollow shaft and intermediate rolling elements are considered.

Numerical simulation of three-dimensional flow field in compact spinning with Hollow Roller

Purpose – Condensing roller is the most key parts of compact spinning system. Hollow Roller is one of the most important kinds of condensing roller, the surface structure of which influences the flow field in condensing zone directly and affects the qualities of spun yarn. The purpose of this paper is to study the effect of Hollow Roller surface structure on flow field in condensing zone is investigated by using Fluent Software. Design/methodology/approach – In this paper, the effect of Hollow Roller surface structure on flow field in condensing zone is investigated by using Fluent Software. The numerical simulations of the three-dimensional flow field in Hollow Roller compact spinning with two different kinds of roller surface structure, round hole structure and strip groove structure, are given according to the three-dimensional physical model of condensing zone. The flow velocity and static pressure distributions in condensing zone are given. Findings – It is shown that the flow velocity streamline distribution is denser with strip groove structure than that of round hole structure, especially on the center line of strand, and flow velocity value is also larger in both Y-Z and X-Y cross-sections, and in X-Z cross-section shows the embracing inlet airflow, which is benefit for fiber condensing directly and improving negative pressure use efficiency. Furthermore, the simulations with three strip groove widths 0.4, 0.8 and 1.2 mm are given. The theatrical results obtained are illustrated by experiments. Originality/value – In this paper, the effect of Hollow Roller surface structure on flow field in condensing zone is investigated by using Fluent Software in detail. A more accurate three-dimensional physical model of condensing zone is given. A new kind of strip groove structure of Hollow Roller is proposed. The theatrical results obtained are illustrated by experiments, and lay a foundation for practical Hollow Roller design.

와이어 소 머신용 중공롤러의 변위량과 응력해석에 관한 연구

본 연구에서는 원통형 중공롤러를 갖는 와이어 소 머신에 대한 변위와 응력강도 안전성 해석결과를 제시하고 있다. 유한요소법을 사용하여 세 개의 튜브 사이에 Y형상의 편위형 컬럼과 수직형 컬럼을 설치한 중공롤러에서 변형거동과 응력강도 안전성을 높인 중공롤러를 개발하고자 한다. 동일한 직경과 길이를 갖지만, 중량을 달리하는 중공롤러 모델에서 Y 형상의 편위형 및 수직형 중공롤러에 작용하는 변위거동 안전성은 중공롤러의 전체길이에 의해 더 많은 영향을 받는 것으로 나타는데, 이것은 중공롤러의 굽힘 모멘트와 밀접한 관련이 있다. 그러나, 중공롤러의 응력강도는 중량 차이가 크지 않을 경우 절단면의 형상에 의해 더 큰 영향을 받는 것으로 나타났다. 따라서, 중공롤러의 강도안전성을 높이고, 총중량을 낮추기 위해서는 Y형상을 갖는 중공롤러를 사용하는 것이 바람직함을 알 수 있다. In this paper, the displacement and stress strength safeties have been presented for cylindrical hollow rollers of a wire saw machine. Using the finite element method, the hollow roller with Y-shaped shift and vertical columns between three tubes has been developed to analyze the displacement behavior and stress strength safeties. For the same diameter and length of hollow roller models with a different weight, the displacement behavior safety of Y-shaped shift column and vertical column models is heavily depending on the total length of a hollow roller, which is closely related to the bending moment of a hollow roller structure. But, the stress strength of a hollow roller is more influenced by the cross sectional area of a hollow roller for the similar weight. Thus, this paper recommends Y-shaped hollow roller for increasing the roller strength safety and decreasing a total roller weight.

원통형 중공롤러의 변형거동 안전성에 관한 연구

본 연구에서는 원통형 중공롤러의 변위거동 안전성에 대한 해석적 연구를 수행하였다. 세 개의 튜브들 사이에 Y형상을 갖는 컬럼 구조물을 설치한 중공롤러를 개발하여 유한요소법으로 변형거동 안전성을 해석하였다. 동일한 크기와 중량을 갖는 두 개의 중공롤러 모델에 대한 해석결과에 의하면, 기존의 중공롤러는 세 개의 튜브 사이에 새로이 설계된 Y형상을 갖는 컬럼을 설치한 중공롤러에 비해 4~6.6% 낮은 변형거동 안전성을 보여주고 있다. 따라서 본 연구에서는 중공롤러의 강도 안전성을 높이고, 전체적인 중량을 낮춰 소비되는 전기에너지를 줄이기 위해서는 Y형상 컬럼을 설치한 새로운 중공롤러를 사용하는 것이 바람직함을 알 수 있다. This paper presents an analytical study on the displacement behavior safety of cylindrical hollow rollers. Using the finite element method, the hollow roller with Y-shaped column structures between three tubes has been developed to analyze the displacement behavior safety. For the same dimension and weight of two hollow roller models, the displacement behavior safety of a typical hollow roller is lower 4~6.6% than that of the newly designed hollow roller with Y-shaped column structures between three tubes. Thus, this paper recommends Y-shaped hollow roller for increasing the roller strength safety and decreasing a total roller weight, which may save a consuming electrical energy.

Simulation Analysis of Cross Wedge Rolling Hollow Parts with Mandrel

Cross wedge rolling hollow shafts with a mandrel has attracted much attention in the recent years because of the demand for light components. Finite element method was used to simulate the rolling process of hollow part and validated by experiment. By tracking strain change of the typical points and analyzing the strain contour maps of cross-section at four typical moments, the cause of cross section oval and shaft shoulder protuberance of part is expounded.

The Effects of Load on the Radial Bearing Properties of Pre-Loaded Cylindrical Roller Bearings

According to the theory of contact mechanics, the radial stiffness, the maximum contact stress, and the maximum radial load of pre-loaded cylindrical roller bearings, including both solid roller and hollow roller bearings, are calculated with the finite element method. The effects of load on the radial stiffness, the maximum contact stress, and the maximum radial load of bearing are analyzed. The analysis results show that the effect of load on the radial stiffness is complex. Under the different magnitude loads, the effects of both hollowness and interference magnitude on the radial stiffness and on the maximum contact stress are not same. Thus the effects of load magnitude must be considered in the design and application of pre-loaded cylindrical roller bearings.

Analysis of Hollow Rollers Implementation in Flexible Manufacturing of Large Bearings

Analysis of Hollow Rollers Implementation in Flexible Manufacturing of Large Bearings

Predicting optimum hollowness of normally loaded cylindrical rollers using finite element analysis

Fatigue life investigations have been made for hollow rollers in pure normal loading. Different hollowness percentages between 20 and 80% have been tested to find the optimum percentage hollowness that gives the longest fatigue life. Two main models were built for this purpose: model 1 with two identically sized rollers and model 2 with two non-identically sized rollers. In each model, two cases have been studied: when both rollers are hollow and when one roller is hollow while the other one is solid. The Ioannides–Harris (IH) theory was used to calculate the relative fatigue life of the hollow rollers with respect to solid rollers under the same loading. Investigations have been made for five different materials: CVD 52100, carburised steel, VIMVAR M50, M50NiL and induction hardened steel. The finite element package ABAQUS has been used to study the stress and deformations in the loaded rollers. In general, the optimum hollowness percentage with the longest fatigue life ranges between 60 and 70% based on the kind of the material, whether the rollers are of the same or different size and whether one or both rollers are hollow. Using the IH theory for fatigue life calculation resulted in having infinite fatigue life for those rollers made of induction hardened steel that relatively has high fatigue limit value. Rollers in the optimum range are flexible enough to get the best redistribution of stress in the contact zone. For models of a hollow cylindrical roller in contact with a solid roller, the optimum hollowness is around 70%. When both cylindrical rollers are hollow, the optimum hollowness decreases between 60 and 65%. At the optimum hollowness, small differences in the fatigue life have been found between models of one hollow roller and models of two hollow rollers, even though having both hollow rollers means less weight, thus saving more material and more stability for the system.

Numerical prediction of optimum hollowness and material of hollow rollers under combined loading

Fatigue life investigations have been made for cylindrical hollow rollers in pure rolling contact. In addition to normal loading, the rollers have been subjected to tangential loading of 1/3rd the normal load value. Sufficient coefficient of friction has been used to ensure no slipping occurs. Two main models were built with different hollowness percentages to investigate the hollowness percentage that gives the longest fatigue life. The first model consists of two cylindrical rollers of same size, while the second model consists of two rollers of different sizes. Two cases have been studied, when both rollers are hollow and when only one roller is hollow. The stress distribution in the roller body and the resulting deformation has been investigated using the finite element package, ABAQUS. Then the Ioannides–Harris (IH) theory was used to predict the fatigue life of the hollow rollers in pure rolling contact. Investigations have been made for five different materials, CVD 52100, Carburized steel, VIMVAR M50, M50NiL and Induction-hardened steel. It has been found that the optimum hollowness percentage with the longest fatigue life ranges is around 50%. Many factors affect the optimum hollowness percentage, like the kind of the material used for the cylindrical roller, whether the rollers in contact are of the same size or different size and whether the hollow roller is in contact with another hollow roller or in contact with solid roller.

Relative fatigue life estimation of cylindrical hollow rollers in general pure rolling contact

AbstractSolid and hollow cylindrical rollers in pure rolling contact have been modelled. The two rollers are subjected to a combined normal and tangential loading. The tangential loading is one‐third of the normal loading value. The finite element package, ABAQUS, is used to study the stress distribution and the resulting deformations in the bodies of the rollers. Then the Ioannides–Harris fatigue life model for rolling bearings is applied on the ABAQUS numerical results to investigate the fatigue life of the solid and hollow rollers. Using the fatigue life of the solid rollers as the reference fatigue life, the relative fatigue lives of hollow rollers are determined. Four main different hollowness percentages are been studied: 20, 40, 60 and 80%. The hollowness percentage is the ratio of the diameter of the hole to the outer diameter of the cylinder. For each of those hollowness percentages, two cases are studied – when the two rollers in contact are hollow and when one hollow roller is in contact with a solid roller. This study includes two main models: Model 1, where the two cylindrical rollers in contact are of the same size, and Model 2, where the two rollers in contact are not of the same size. The estimated relative fatigue lives of hollow rollers showed a great improvement of the fatigue life compared with solid rollers under the same loading conditions. This was a result of the redistribution of stresses in the contact zone in the case of hollow rollers. Redistribution of stresses over a larger volume of the roller body decreased the peak stress and reduced the volume under risk. Increasing the hollowness percentage from 20 to 60% increased the flexibility of the roller, and better stress distribution was achieved, which resulted in improving the fatigue life. Although 80% of hollowness rollers have more flexibility than 60% of hollowness rollers, the bending stresses (σb) on the inner surface of the rollers tend to decrease the fatigue life. Copyright © 2007 John Wiley & Sons, Ltd.

Fatigue life investigation of solid and hollow rollers under pure normal loading

AbstractTwo solid and hollow cylindrical rollers in pure rolling contact subjected to pure normal loading have been modelled. Using a finite element package called ABAQUS, the stress and strain distributions in the two rollers in contact have been determined. The relative fatigue life of the hollow rollers compared to solid rollers has been investigated using the fatigue life model for rolling bearings developed by Ioannides and Harris. Different hollowness percentages have been studied: 20, 40, 60 and 80%. The hollowness percentage is the ratio of the diameter of the hole to the outer diameter of the cylinder. Both cases were studied – when the two rollers in contact are hollow and when only one of them is hollow while the other one is solid. Making the rollers hollow will result in redistribution of stresses over a larger volume in the contact zone due to the flexibility of the hollow rollers. That decreases the peak stress in the contact zone of the hollow cylinder when compared to the solid cylinder. Hollow cylinders have more flexibility when subjected to normal loading. And so, the stresses are redistributed so that the fatigue life is improved. The best stress redistribution and so fatigue life improvements have been found when both cylinders have around 60% hollowness. Copyright © 2007 John Wiley & Sons, Ltd.

Development of a critical friction model for cross wedge rolling hollow shafts

In the manufacturing community, there has been a significant movement towards forming hollow shafts with the cross wedge rolling (CWR) process. This trend has presented the engineering community with a significant challenge because all of the current failure models for the CWR process have been based on the rolling of solid billets. In the present investigation, an analytical model has been developed for determining the minimal friction required at the tool workpiece interface to achieve rolling (critical friction) in the cross wedge rolling of hollow shafts. By means of the explicit dynamic finite element method and specialized experiments, the accuracy of the analytical model was evaluated for the rolling of hollow 6061 T6 Aluminum billets. Based on the numerical and experimental results, trends for the variation of the critical friction as a function of CWR process parameters were subsequently ascertained and discussed with respect to excess slip failure.

Spherical grating monochromator with interferometer control and in-vacuum reference

Physical Science Laboratory’s new generation of spherical grating monochromators incorporates a laser interferometer to control scan angle and an in-vacuum absolute angle reference, as well as other improvements. The design accommodates up to six gratings which can be moved axially (under motor control, with encoder position readback) at any scan angle. The gratings are cooled by means of spring-loaded clamps which conduct heat to a water-cooled plate. The instruments feature hollow roller bearings on the scan axis to minimize bearing runout, and a pseudosine-bar drive for precise control of grating angle. The interferometer angle-measuring optics are mounted inside the vacuum chamber and measure the angle between the grating scan axis and the instrument’s granite base. The laser interferometer measures the grating angle with a resolution of approximately 0.02 arcsec over the entire scan range of 40°. To provide a reference for the interferometer angle measurement, we have built an in-vacuum optical reference which uses custom chrome-on-glass reticles mounted inside the vacuum chamber. Collimated light from a source outside the vacuum passes through the reticles to yield quadrature signals which precisely define an absolute reference angle for the interferometer. Repeatability of the grating angle is within a range of ±0.05 arcsec. Two of these instruments are in operation at SRRC (Taiwan) and a third instrument has been delivered to NSLS (Brookhaven).

Analysis of Load Distributions Within Solid and Hollow Roller Bearings

The virtual contact loading method is further developed in this paper tostudy the multi-body contact phenomena within solid and hollow roller bearings. The distributive virtual contact loads are used to simulate the contact constraint forces on each contact surface. The deepest penetration criterion is proposed to select and determine the contact nodes in an orderly way, so as to ensure the local iteration process converged and to increase the computational efficiency. The load distributions within the solid and hollow roller bearings have been studied in more detail and some reasonable results are obtained.

Surface durability of Tufftrided rolling elements

With increasing demands for higher speed bearings, hollow rolling elements find wider applications. Hollow rolling elements perform better than solid elements. The surface durability of Tufftrided hollow rolling elements is highlighted in the present paper. During tests the Tufftrided layer was seen to spread, similarly to the behaviour of thin coated films. This improves the wear characteristics by presenting a harder surface on top of the pitted surface.

High Speed Testing of the Hollow Roller Bearing

This bearing with its preloaded, hollow rollers has the qualities required for high speed operation. Roller hollowness improves cooling ability and its lighter weight reduces the centrifugal force against the raceway. Preloading between inner and outer races for 360 deg insures good roller guidance and minimizes roller skidding. However, the problems of operating a full complement of rollers at very high speeds were unknown. Also, limitations caused by roller bending fatigue needed investigation. To answer these questions, a high speed test machine was constructed and a hollow roller test bearing was designed for operation at 3 million DN. This paper describes the construction of a high speed test cell and subsequent testing of a full complement, preloaded, 115 mm hollow roller bearing. Testing culminated in a successful endurance test of 1000 hours at 26,100 RPM (3 million DN). The results verified several advantages regarding roller stability and antiskidding qualities as well as demonstrating a unique fail-safe condition.

The Rotational Accuracy Characteristics of the Preloaded Hollow Roller Bearing

The rotational characteristics of the cageless, hollow roller radial bearing are investigated. The preloading of the hollow rolling elements in the annular space between the inner and the outer races in such a bearing provides a well controlled and consistent shaft rotational pattern. This pattern is determined by the dimensional and geometrical features of the rollers’ external and internal diameters and roundnesses, the outer and inner ring raceway roundnesses and the eccentricity of the inner race with respect to the shaft axis. The various patterns of shaft runout associated with these causes are identified and the sensitivity of the shaft runout to these factors is examined qualitatively and quantitively. The shaft runout in the present context is not merely the initial static offset of the shaft axis, but is a dynamic, cyclic pattern consisting of certain frequencies resulting from the geometrical features of the bearing components. The somewhat elusive, complex and dynamic nature of this apparent shaft runout makes it difficult to be measured. In addition, the importance of the need to control the circumferential clearance to a minimum is demonstrated. It is thus shown that through the proper control of the component geometry and certain design parameters, the hollow roller bearing can provide an extremely accurate bearing for precision applications.

The Hollow Roller Bearing

The paper deals with the unique functional characteristics that the use of hollow rolling elements induce in a radial type cylindrical roller bearing. The ability to consistently and successfully preload these hollow rollers between the inner and the outer races together with, of course, the necessary but usual degree of precision of the bearing components, provides an effective control of the shaft run-out. This makes the bearing especially suitable for high precision applications. The roller preloading also eliminates the need for a roller guidance from a retainer which, combined with the lighter rollers, generally means higher speed capabilities. In addition to the inherent superior rotational accuracy of the hollow roller bearing, it is also demonstrated as to why, contrary to the common belief, the preloading ability of the hollow rollers results in significant stiffness improvements over, say, a corresponding solid roller bearing. The significance of the roller hollowness is discussed with regard to the stiffness, load capacity and life characteristics of this bearing. Finally, the suitability of the various lubrication systems for this bearing are discussed.

A Hollow Roller Bearing for Use in Precision Machine Tools

The Performance characteristics of a radial bearing using preloaded hollow rollers in the annular space between the inner and the outer races are investigated with regard to its radial stiffness, high speed capability and the shaft runout during rotation. It is shown that the preloading of the hollow rollers, in addition to providing a complete control of the shaft rotation which is important in precision machine tools, also yields improved bearing stiffness. Moreover, the control of the circumferential position and the motion of every roller eliminates the need for a cage which enhances the high speed capabilities of the hearing. The investigation has shown that the provision of the proper roller hollowness and preload are critical to the satisfactory operation of the hollow roller bearing. For high precision applications, spindle assemblies with total indicated runouts of 0.5 μm or less can be obtained consistently through the control of the dimensional and geometrical features of the bearing components, namely, the roller and the raceway roundnesses and the external and internal diameters of the rollers together with their circumferential clearances.