• Coupled systems mechanics
• /
• v.7 no.5
• /
• pp.583-610
• /
• 2018

This paper discusses the issues associated with modeling frictional contact between solid bodies undergoing large deformations. The most common model for friction on contact interfaces in solid mechanics is the Coulomb friction model, in which two distinct responses are possible: stick and slip. Handling the transition between these two phases computationally has been a source of algorithmic instability, lack of convergence and non-unique solutions, particularly in the presence of large deformations. Most computational models for frictional contact have used penalty or updated Lagrangian approaches to enforce frictional contact conditions. These two approaches, however, present some computational challenges due to conditioning issues in penalty-type implementations and the iterative nature of the updated Lagrangian formulation, which, particularly in large simulations, may lead to relatively slow convergence. Alternatively, a plasticity-inspired implementation of frictional contact has been shown to handle the stick-slip conditions in a local, algorithmically efficient manner that substantially reduces computational cost and successfully avoids the issues of instability and lack of convergence often reported with other methods (Laursen and Simo 1993). The formulation of this approach, however, has been limited to the small deformations realm, a fact that severely limited its application to contact problems where large deformations are expected. In this paper, we present an algorithmically consistent formulation of this method that preserves its key advantages, while extending its application to the realm of large-deformation contact problems. We show that the method produces results similar to the augmented Lagrangian formulation at a reduced computational cost.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.17 no.2
• /
• pp.23-29
• /
• 2008

This study analyzes the rolled circular rod strip with radius of loom and length of 350cm by using finite element analysis. The material strength and its durability of the rolled strip can be predicted through this study. As the penetration tolerance by contact decreases, the contact rigidity of strip increases. As the contact rigidity becomes the highest at the elapsed time of 1.2 second, the contact stress becomes the lowest. On the contrary, von-Mises stress becomes highest at this time. The total deformation on strip increases from the upper part of strip at the position near to rotating roll to the lower part of strip at the position near to fixing roll.

• Tribology and Lubricants
• /
• v.13 no.3
• /
• pp.48-55
• /
• 1997

The ball bearing with thin-section raceways which is much lighter than other conventional bearings used in most modem passenger cars and small tracks. The important design parameters of this bearing is the groove radius of raceways, the diametral clearance, the free contact angle and so on. The optimal value of these parameters were determined by considering the dynamic load capacity, the contact angle and the calculated fatigue life. The contact angle between a ball and raceways was calculated by considering the local contact deformation and the structural deformation of thin-section raceways which was estimated by FEM. The raceways were made by means of the press-forming process. The fatigue life tester was designed and manufactured. The fatigue life test was executed and the reliability of this bearing was confirmed.

• Journal of Welding and Joining
• /
• v.19 no.4
• /
• pp.384-390
• /
• 2001

There have been many problems due to deformation in industry field. Especially, it is severe in parts with small size and thin thickness and in products that must have excellent airtightness and anti-noise. The countermeasures for this deformation in field have mainly been dependent on the rule of trial and error by operator's experience because of productivities. Systematic study about this product with deformation is also insufficient that deformation is complex problem with shape, size, material of product, joining method and conditions, etc.. It is efficient to apply CAE technique without influence on productivity to this problem. There is, however much difference between the result analyzed by CAE and appearances in working field because of the insufficiency of communication between simulator and worker and of sensing data for boundary condition in analysis. In this study, to solve this deformation problem, we intend to make a simulation model that is adapted from working conditions by tuning and feedback between sensing data and simulation results. This paper include temperature monitoring and make a heat transfer model using sensing data in product as previous step for deformation analysis. The heat transfer analysis of shrinkage fit process is considerably difficult due to contact heat transfer between case and core. To solve this contact problem, gap element is used in present study.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.10
• /
• pp.2180-2186
• /
• 2002

In a micro-scale contact, capillary force and van der Waals interaction significantly influence the contact between asperities of rough surfaces. Little is, however, known about the variation of these surface forces as a function of chemical property of the surface (wet angle), relative humidity and deformation of asperities in the real area of contact. A better understanding of these surface forces is of great necessity in order to find a solution for reducing friction and adhesion of micro surfaces. The objective of this study is to investigate the surface forces in micro-scale rough surface contact. We proposed an effective method to analyze capillary and van der Waals forces in micro-scale contact. In this method, Winkler spring model was employed to analyze the contact of rough surfaces that were obtained from atomic force microscopy (AFM) height images. Self-mated contact of DLC(diamond like carbon) coatings was analyzed, as an example, by the proposed model. It was shown that the capillary force was significantly influenced by relative humidity and wet angle of the DLC surface. The deformation of asperities to a critical magnitude by external loading led to a considerable increase of both capillary and van der Waals forces.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.6 no.6
• /
• pp.536-541
• /
• 2005

Large displacement and rigidity about rubber component are expected by nonlinear and large deformation analysis in this study. Rubber is also used by the model of Mooney-Rivlin and the self contact between rubbers is established. There is the friction between rigid body and rubber, wall and floor. The nonlinear simulation analysis used in this study is expected to be widely applied in design, analysis and development of several rubber components which are used in automotive, railroad, and mechanical elements etc. By utilizing this method, time and cost can also be saved in developing new rubber product. The analysis of rubber components requires special material modeling and non-linear finite element analysis tools that are quite different from those used for metallic parts. The objective of this study is to analyze the rubber component with large deformation and non-linear properties.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.11
• /
• pp.150-157
• /
• 2003

In this paper, the large deformation of hollow silicon rubber gasket is treated. The frictional contact occurs between groove and the outer part of hollow gasket, and the frictional self-contact exists in the inner parts of hollow gasket. The silicon rubber has the nonlinear elastic behavior and its material property is approximately incompressible. Hence, the stress analysis requires an existence of a strain energy function, which is usually defined in terms of invariants or stretch ratio such as generalized Mooney-Rivlin and Ogden model. Considering large compressive deformation and friction, Mooney-Rivlin 3rd model and Coulomb's friction model are assumed. The numerical analysis is obtained by the commercial finite element program MARC. But, due to large deformation, the elements degenerate in the inner parts of hollow gasket. This means that the analysis of subsequent increments is carried out with a very poor mesh. In order to continue the analysis with a sufficient accuracy, it is necessary to use new finite element modeling by remesh. Experiments are also performed to show the validity of present method. As a conclusion, numerical results by this research have good agreements with experiments.

• Nuclear Engineering and Technology
• /
• v.45 no.1
• /
• pp.53-60
• /
• 2013

Bentonite is generally used as a buffer material in high-level radioactive waste disposal facilities and consists of 50% quartz by weight. Quartz strongly affects the behavior of bentonite over very long periods. For this reason, quartz dissolution experiment was performed under high-pressure and high-alkalinity conditions based on the conditions found in a high-level radioactive waste disposal facility located deep underground. In this study, two quartz dissolution experiments were conducted on 1) quartz beads under low-pressure and high-alkalinity conditions and 2) a single quartz crystal under high-pressure and high-alkalinity conditions. Following the experiments, a confocal laser scanning microscope (CLSM) was used to observe the surfaces of experimental samples. Numerical analyses using the finite element method (FEM) were also performed to quantify the deformation of contact area. Quartz dissolution was observed in both experiments. This deformation was due to a concentrated compressive stress field, as indicated by the quartz deformation of the contact area through the FEM analysis. According to the numerical results, a high compressive stress field acted upon the neighboring contact area, which showed a rapid dissolution rate compared to other areas of the sample.

• 제어로봇시스템학회:학술대회논문집
• /
• 1997.10a
• /
• pp.1395-1398
• /
• 1997

Flexible parts comparing with rigid parts can be deformed by contact force during assembly. for successful assembly, information about their deformation as well as possible misalignment between mating parts is essential. Howecer, because of the complex relationship between parts deformation and reaction forces, it is difficult to acquire all required information from the reaction forces alone. In this paper, we measure parts deformation and misalignments by using the visual sensing system presented for flexible parts assembly. Experimental results show that the system can be effectively used for detecting parts deformation and misalignments between mating parts.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.23 no.3
• /
• pp.259-265
• /
• 2014

When the brakes of a vehicle are applied, large amounts of heat are generated on the surfaces of the brake discs owing to friction between the discs and the brake pads. A high temperature gradient on the disc surfaces leads to thermal deformation and severe disc abrasion. Ultimately, the thermal deformation and disc wear give rise to a thermal judder phenomenon, which has a major effect on the stability of the vehicle. To investigate and propose a solution to these problems, thermoelastic instabilities under applied thermal and mechanical loads were analyzed using the commercial finite element package ANSYS by considering the contact surfaces between the discs and pads. Direct-contact three-dimensional finite elements between the discs and pads were applied to investigate the disc friction temperature, thermal deformation, and contact stress so that the thermal judder phenomenon on the surface of the disc could be predicted.