Subscribe to RSS
Bearings Units
Miniature Bearings
Standard Bearings
Overmolded Bearings
Custom Bearings
England Germany Russia India Turkey SouthAfrica UnitedStates Netherlands Philippines Belgium Australia Brazil Spain China Korean

Advanced numerical simulations for optimized seal designs

These days, numerical simulations are key in developing new products and improving existing ones. To improve the overall product design and the support to customers, SKF is equipping product engineers with Finite Element tools, developed at the SKF Engineering & Research Centre in the Netherlands.

SKF seal design

Complexity of seal designs. Automotive seal and industrial seal.

Numerical simulations are playing an important role in different stages of the life cycle of an increasing number of products. Virtual simulations reduce costs throughout the concept development and prototype phases as a result of extensive numerical analyses, enabling improved prototype designs to be physically tested.

SKF seal design 1

Gearbox simulated with Orpheus.

There are several commercial calculation tools in the market that have proved to be very reliable and widely applicable in different fields. These software packages are designed for general use and thus are able to investigate several types of phenomena. However, highly skilled users are necessary to run such tools as well as to interpret the results and to convert them into meaningful solutions.

SKF seal design 2

Stress-strain relation in an NBR rubber material.

SKF has a long experience in numerical simulations, not only in the use of these commercial simulation packages but also in the development of in-house calculation tools. The Orpheus and BEAST platforms are used daily by SKF engineers to provide answers and to support customers. With these in-house tools, bearing applications have been simulated by SKF in multiple ways and complexity levels. This experience and these tools are continuously being enhanced with new functionality and capability to meet the SKF vision for numerical simulations where all components – bearings, shafts, seals, gears and housings – are simulated as a complete system (fig. 1).

SKF seal design 3

Simulation of the contact of a seal with its rigid counter surface.

Seals and numerical simulations
The first step towards the simulation of complete systems is the simulation of seals as single components (fig. 2). This initial detailed focus on a single component involves SKF gaining an even more in-depth understanding of the performance of the seal once it is installed in its final position.

Numerical simulations of seals involve several mechanical aspects. In the following, these aspects are briefly described to provide an overview of the complexity of seal simulations as well as the technology SKF is developing in order to provide product engineers with powerful and reliable software.

SKF seal design 4

Simulation of a large-diameter seal to fit inside a rigid housing.

Simulations of rubber: a highly non-linear material
Many of the engineering calculations done today are based on the assumption that the material behaves linearly and elastically – that is, that force and displacements are linearly dependent on a constant, which is called stiffness. Rubber materials in general behave non-linearly. It is not enough to define one constant to relate force to displacements or stress to strain. Instead, rubber requires more complex constitutive models that can handle multi-axial non-linearity.

SKF seal design 5

SKF Seal Designer mounting simulation without a garter spring.

Amongst others, hyperelastic models are often used to simulate rubber behaviour. These mater­ial models are elastic, but as shown in fig. 3, outside a certain stretch range the non-linearity of the stress-strain relation deviates significantly from linear behaviour. Moreover, the material response depends highly on the orientation of the deformation.

SKF seal design 6

SKF Seal Designer mounting simulation with a garter spring.

Rubber is the most common seal material, because it enables the seals to follow the movements of the counter surfaces they are in contact with, such as shafts, rods or bearings. For the simulation of seals, it is therefore necessary to have a reliable way of simulating hyperelastic material models that can undergo large deformations in multiple orientations.

Simulations of rubber: an almost incompressible material
Rubber is also a nearly incompressible material – that is, the variation in volume of a compressed or stretched sample of rubber before and after the deformation is almost zero. This is a peculiar material behaviour, which challenges the numerical methods implemented in traditional simulation software. The incompressibility of rubber produces numerical instabilities normally indicated as “volumetric locking”. To cope with such a challenge, a special implementation of the integration scheme has been implemented in order to provide correct and stable results [1].

A literature search has pointed towards the solution of the volumetric locking being the F-bar method [1], which requires a modification to the traditional integration methods presented in literature [2]. On this aspect, collaboration with the academic world, in particular with Twente University in the Netherlands, has demonstrated the accuracy and the precision of the implemented algorithms. This has allowed the quality of the calculation to be comparable to the load calculation predicted by one of the commercial FE packages, such as ABAQUS, Marc or ANSYS.

Simulation of seals: contact mechanics to deal with interference
Sealing elements need to be installed in the working position with a certain given interference between the bore and the shaft. Therefore, it is crucial to be able to simulate the contact between the seals and the surrounding surfaces (such as housings, shafts, flingers or bearings) (figs. 4 and 5).

SKF seal design 7

Existing wiper seal.

To correctly simulate the interference between seals and the surrounding parts of the application, contact mechanics have been one of the key requirements included in the development of the software tool. Contact can be solved in numerical codes in different ways. Considering the nature of the material that is normally in contact (usually rubber against steel), it is assumed that there is no co-penetration between the bodies in contact. This assumption has led to the adoption of the Lagrange multiplier method (the seal deformation is forced to mathematically equal the constraints, given by the surrounding counter surfaces) instead of the penalty method (the seal deformation is forced by means of penalty functions, which are activated as soon as the constraints are violated).

Simulations of a sealing system: FE solver
The best way to combine all the above items in numerical simulations is to use the power of the finite element method (FEM). In fact, this method can easily handle the combined aspects of hyperelastic material models, large deformations, contact mechanics by means of the Lagrange multiplier method and special implementation to avoid the numerical locking problem due to material incompressibility.

SKF seal design 8

Wiper seal, redesigned to fit new customer requirements: smaller housing, same radial load.

SKF Seal Designer
SKF, with the support of the SKF Engineering & Research Centre, has equipped its product engineers with a state-of-the-art calculation tool based on the Orpheus platform. The released tool is called the SKF Seal Designer.

The major capabilities of the software are covering both manufacturing (shrinkage from the mould tooling to finished geometry) and performance (installation on a shaft and/or inside housing) predictions.

Manufacturing simulation capabilities are available to SKF’s product engineers so as to improve the study of the design on the final shape of the seal. It is also used to improve the mould geometry, which is one of the most important parts of the overall design process due to its cost contribution, but also because mould geometry can be reused for other designs.

The capability of calculating the seal installed on a shaft is an additional feature. When a seal is installed, it exerts a force on the counter surface called lip force (fig. 6). Lip force is one of the most important parameters of a seal for both static and dynamic operating conditions. Lip force ensures the desired sealability, but it is also responsible for the seal friction under the lip. In addition, a garter spring could be used to keep the sufficient lip force for sealing as the seal material is ageing (fig. 7). For this reason, an accurate prediction of the lip force under different operating conditions is a crucial requirement for a simulation tool that will help to reduce the number of design iterations, and therefore time-to-market for new products (figs. 8 and 9).

SKF Seal Designer has brought the power of FE simulations to SKF’s product engineers. The tool provides reduced time-to-market by enabling product engineers to assess virtually how seal parameters, customer design requirements and application requirements affect seal perform­ance.

[1]: “Computational Methods for Plasti­city: Theory and Applications”, by EA de Souza Neto, D Peric and DRJ Owen (30 Dec 2008)
[2] “The Finite Element Method”, Sixth Edition, by OC Zienkiewicz and RL Taylor (20 Sep 2005)

By Andrea Bacchetto, team leader at Knowledge and Simulation Tools, SKF Engineering & Research Centre, Nieuwegein, the Netherlands; Alex X Paykin, manager Research and Development, SKF Sealing Solutions, Elgin, Illinois, USA.

source: SKF evolution magazine

0 commentsback to post

Add your comment



Other articlesgo to homepage

무선 진동 분석

무선 진동 분석(0)

PRÜFTECHNIK, VIBCONNECT RF에 새로운 기능 추가 ISMANING – 2014년 3월 25일- 새로운 펌웨어 업데이트를 통해 PRÜFTECHNIK의 무선 온라인 컨디션 모니터링 시스템인 VIBCONNECT RF가 한층 강화됐다. 무선 기술이 장착된 VIBCONNECT RF는 장거리 진동 측정 데이터를 무선으로 전송해야 하는 어플리케이션에 완벽하게 활용될 수 있다. VIBCONNECT RF 의 최신 펌웨어 업데이트는 몇 가지 강력한 특징을 갖는다. 상태 및

진동 측정 장비를 이용한 베어링 윤활처리 모니터링

진동 측정 장비를 이용한 베어링 윤활처리 모니터링(0)

윤활처리된 베어링의 재윤활 시기 자동 연속 윤활 시스템이 점점 더 많은 대형 베어링 들에 장착되고 있지만, 그림 1에서 보여지는 것과 같은 팬에 적용될 경우 비용면에서 효율적이지 않다. 그림 1: 팬 일반적인 팬들은 특정 간격으로 수작업에 의해 윤활처리 되지만, 그렇다면 이런 간격은 얼마나되어야 하는가? PRÜFTECHNIK의 온라인 컨디션 모니터링 시스템이 해답을 제시해 줄 수 있다. 예를 들면,

신뢰성 향상을 위한 윤활 관리

신뢰성 향상을 위한 윤활 관리(0)

공장 내 윤활처리 작업은 공장 뿐만 아니라 기기의 신뢰성에 직접적인 영향을 미친다. 기계 내에서 윤활유가 오염을 최소화 하고, 아무런 화학적 분해없이 효과적으로 작동할 때, 부품의 마모도는 감소하고 기기의 신뢰성은 향상 될 것이다. 마모도 감소와 기기 신뢰성을 향상시키기 위해서는 효과적이고 깨끗한 평균 윤활 막 두께, 즉 좋은 점도를 보호하고 유지하는 것이 가장 중요하다. 윤활 신뢰성이란? 베어링

사례연구: 펌프모터 베어링의 성능 향상

사례연구: 펌프모터 베어링의 성능 향상(0)

이 연구는 STARWOOD Inc.의 수석 엔지니어인 mr.Selcuk Karabay에 의해 진행됐다. 결과: 프레스 기계에 사용되는 핫오일 펌프 모터는 작동온도가 90-100° C에 달했고, 진공 펌프 모터의 경우 100-110° C이며, 작동이 계속적으로 멈추는 현상을 보였다. 또한 높은 작동 온도로 인해 고온의 베어링이 6개월만에 파손되기도 했다. 테스트 핫오일 펌프 모터 테스트 진공 펌프 모터 파손 원인: 상황 분석 후,

볼베어링 & 에저지절약

볼베어링 & 에저지절약(0)

요즘 전 세계적으로, 환경에 미치는 영향을 최소화 하기 위해 그린상품에 대한 수요가 증가되고 있다. 이러 추세는 앞으로도 계속될 전망으로, 기계 및 공장들의 생산능력 향상은 큰 도전과제가 될 것이다. JESA SA는 볼베어링과 폴리머컴포넌트의 설계및 제작에 특화된 회사로써, 성능이 향상된 볼베어링을 제작하기 위한 연구를 시작했으며, 다양한 어플리케이션에 대규모로 사용되는 구성요소들과 깊은 관련이 있어, 잠재적인 에너지 절감이 예상된다.

read more

Contacts and information

Social networks

Most popular categories

Legal Notice

© 2012 BEARING NEWS All rights reserved.