Stefan Björklund - Academia.edu (original) (raw)
Papers by Stefan Björklund
Strojniški vestnik, 2010
Gear tooth modifications, such as lead crowning, are often recommended to compensate for misalign... more Gear tooth modifications, such as lead crowning, are often recommended to compensate for misalignment (e.g. assembly deviations). Lead crowning means that the tooth centre is slightly thicker than ...
A new general linear contact-interaction model is derived for treating the dynamic excitation tha... more A new general linear contact-interaction model is derived for treating the dynamic excitation that is due to the rolling contact of rough surfaces. It is shown that the relative-displacement and blockedforce models are special cases of this model. A numerical contactcomputation program is utilised to compute the parameters of the contact-interaction model. This program accounts for the detailed surface geometry within the contact region. Furthermore, since contact between rough surfaces is accompanied by locally high stresses, an approximate method for treating plasticity is integrated in to the contact-computation program. The non-stationary response of the contacting bodies is accounted for by a state-space formulation, utilising a modal representation of the dynamic response of the two structures, respectively. As a consequence, the parameters of the contactinteraction model have to be time-dependent. This is dealt with by employing a Monte-Carlo procedure that generates representative time-dependent parameters.
Wear, 2003
Engineering surfaces can be characterized as more or less randomly rough. Contact between enginee... more Engineering surfaces can be characterized as more or less randomly rough. Contact between engineering surfaces is thus discontinuous and the real area of contact is a small fraction of the nominal contact area. The stiffness of a rough surface layer thus influences the contact state as well as the behavior of the surrounding system. A contact model that takes the properties of engineering surfaces into account has been developed and implemented using finite element software. The results obtained with the model have been verified by comparison with results from an independent numerical method. The results show that the height distribution of the topography has a significant influence on the contact stiffness but that the curvature of the roughness is of minor importance. The contact model that was developed for determining the apparent contact area and the distribution of the mean contact pressure could thus be based on a limited set of height parameters that describe the surface topography. By operating on the calculated apparent pressure distribution with a transformation function that is based on both height and curvature parameters, the real contact area can be estimated when the apparent contact state is known. The model presented is also valid for cases with local plastic flow in the bulk material.
Wear, 1994
Our understanding of the mechanics of contact behaviour for interacting particles has been develo... more Our understanding of the mechanics of contact behaviour for interacting particles has been developed mostly assuming that surfaces are smooth. However, real particles of interest in engineering science are generally rough. While recent studies have considered the influence of roughness on the normal force-displacement relationship, surface roughness was quantified using only a single scalar measure, disregarding the topology of the surface. There are some conflicting arguments concerning the effect of roughness on the tangential or shear force-displacement relationship. In this study, optical interferometry data are used to generate the surface topology for input into a 3D finite element model. This model is used to investigate the sensitivity of the normal force-displacement response to the surface topology by considering different surfaces with similar overall roughness values. The effect of surface roughness on the tangential force-displacement relationship and the influence of loading history are also explored. The results indicate that quantifying roughness using a single value, such as the root mean square height of roughness, S q , is insufficient to predict the effect of roughness upon stiffness. It is also shown that in the absence of interlocking, rough particle surfaces exhibit a lower frictional resistance in comparison with equivalent smooth surfaces.
A well-defined rolling contact problem is studied with the intention to cover interesting aspects... more A well-defined rolling contact problem is studied with the intention to cover interesting aspects of tyre-road contact modeling and rolling contact in general. More specifically, the dynamic response in a steel beam caused by a steel ball rolling over it is studied by theoretical modeling of the beam-and ball dynamics as well as the contact forces. Validation of the dynamic response simulations is achieved by comparison with measurements. The contact model is shown to be greatly dependent on an accurate estimate of the real contact stiffness. A method to estimate the contact stiffness which leads to good accuracy in dynamic response simulations is presented. Although the contact stiffness is significantly lower for rubber-asphalt interaction than for steel-steel contact, the results give useful insight for tyre-road contact modeling.
Tribology International, 2007
Friction, lubrication, and wear have a strong influence on the performance and behavior of mechan... more Friction, lubrication, and wear have a strong influence on the performance and behavior of mechanical systems. This paper deals with different friction models for sliding contacts running under different conditions. The models presented are suited to different situations, depending on the type of contact, running conditions, and the behavior of interest. The models will be discussed from simulation and tribological points of view. The different types of friction models considered are: friction models for transient sliding under dry, boundary and mixed lubrication conditions, friction models for micro-displacements of engineering surfaces subjected to transient sliding, friction models often used in the simulation and control of technical systems, combined friction models that represent physical behaviors fairly well but are also suitable for use in simulating systems, friction models that take into account the stochastic nature of interacting surface asperities.
Tribology International, 2007
The topography of the active surfaces in rolling contact depends on the surface roughness obtaine... more The topography of the active surfaces in rolling contact depends on the surface roughness obtained by different manufacturing process technology (turning, grinding, polishing, lapping, etc.). The aim of this paper work is to evidence the influence of the surface roughness on surface geometry of rolling contacts. The experimental tests were carried out on the AMSLER machine and an experimental setup for pure rolling motion. The surfaces of the rolling samples were analyzed with SEM (scanning electron microscopy) and EDS (energy dispersive X-ray spectroscopy) techniques for structural and chemical analysis and measured with the Taylor Hobson profilometer before and after the experimental tests for surface topography.
Procedia CIRP, 2018
In today's business environment, the trend towards more product variety and customization is unbr... more In today's business environment, the trend towards more product variety and customization is unbroken. Due to this development, the need of agile and reconfigurable production systems emerged to cope with various products and product families. To design and optimize production systems as well as to choose the optimal product matches, product analysis methods are needed. Indeed, most of the known methods aim to analyze a product or one product family on the physical level. Different product families, however, may differ largely in terms of the number and nature of components. This fact impedes an efficient comparison and choice of appropriate product family combinations for the production system. A new methodology is proposed to analyze existing products in view of their functional and physical architecture. The aim is to cluster these products in new assembly oriented product families for the optimization of existing assembly lines and the creation of future reconfigurable assembly systems. Based on Datum Flow Chain, the physical structure of the products is analyzed. Functional subassemblies are identified, and a functional analysis is performed. Moreover, a hybrid functional and physical architecture graph (HyFPAG) is the output which depicts the similarity between product families by providing design support to both, production system planners and product designers. An illustrative example of a nail-clipper is used to explain the proposed methodology. An industrial case study on two product families of steering columns of thyssenkrupp Presta France is then carried out to give a first industrial evaluation of the proposed approach.
The purpose of this work-package within the Quiet-track, FP7, is to develop a noise related track... more The purpose of this work-package within the Quiet-track, FP7, is to develop a noise related track maintenance tool, in the form of an on-board measurement system. As a first step, lab scale tests u ...
Wear, 1996
Mild wear may have damaging effects on contacting components, when the material removal distorts ... more Mild wear may have damaging effects on contacting components, when the material removal distorts component geometry. Surface pressures can then be redistributed in an unfavoumblc way which increases the i~-ohability for surface fatigue, Phenomena like this have Men observed in an ordinary automotive cam-follower contort. The purpose of this work is m derive a simulation model for the mild wear in a nam-foliower contact with follower rotation. The mild wear in such a contact is simulated using the pdnci#e of single point observation. The simulation model is based on a modified Archerd's wear equation. After each simulation step the pressures am recalculated using the topographically changed surfaces. Three eases are studied: one where only follower wear is considered, one where only the cam wear is simulated and finally the case where both cam and f,]lower wear is simulated. An FEM analysis of the follower was used to verify the infinite half plane assumption in the pressare calculations. The present work highlights the importance of including follower relation in the wear simulation and the use of the single point observation method in the derivation of a wear simulation model. The results show that the ease whom only the cam is worn gives the lowest contact pressures. The case where only follower wear is considered is the most unfavnnrablo when it comes to contact pressures and wear.
Wear, 2000
Owing to the curved contact surfaces in a spherical roller thrust bearing, the rollers will under... more Owing to the curved contact surfaces in a spherical roller thrust bearing, the rollers will undergo sliding. For an unskewed roller there will be two points along each contact where the sliding velocity is zero. At all other points along the contact, sliding is present. Under boundary lubricated conditions the sliding can give rise to mild wear. Experimental results show that this wear can cause a significant change in the surface profile outside the zero sliding points. The mild wear in the contact was simulated using Archard's wear law. An iterative wear model is described in which the normal load distribution, the tangential tractions and the sliding distances are repeatedly calculated to simulate the changes in surface geometry due to wear. Good qualitative agreement was achieved between the simulation results and the previously presented experimental results.
Journal of Tribology, 2006
The contact area and pressure distribution in a wheel/rail contact is essential information requi... more The contact area and pressure distribution in a wheel/rail contact is essential information required in any fatigue or wear calculations to determine design life, re-grinding, and maintenance schedules. As wheel or rail wear or surface damage takes place the contact patch size and shape will change. This leads to a redistribution of the contact stresses. The aim of this work was to use ultrasound to nondestructively quantify the stress distribution in new, worn, and damaged wheel-rail contacts. The response of a wheel/rail interface to an ultrasonic wave can be modeled as a spring. If the contact pressure is high the interface is very stiff, with few air gaps, and allows the transmission of an ultrasonic sound wave. If the pressure is low, interfacial stiffness is lower and almost all the ultrasound is reflected. A quasistatic spring model was used to determine maps of contact stiffness from wheel/rail ultrasonic reflection data. Pressure was then determined using a parallel calibra...
International Journal of Machine Tools and Manufacture, 1998
Wear of boundary lubricated spherical roller thrust bearings has been characterised with 3-D surf... more Wear of boundary lubricated spherical roller thrust bearings has been characterised with 3-D surface measurements and analysis. Due to the curved contact surface in a spherical roller thrust bearing, the rollers will undergo sliding in the contact. For an unskewed roller there will ...
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2011
ABSTRACT Striving for higher gear transmission efficiency by using a low-viscosity transmission l... more ABSTRACT Striving for higher gear transmission efficiency by using a low-viscosity transmission lubricant affects the lubricant film thickness. To keep the Λ-ratio (the ratio between the film thickness and the surface roughness) intact, more effort must be put on the surface topography. This paper presents a study of how running-in affects the dry elastic contact area ratio in spur gears using real surface topographies from three common manufacturing methods (green-shaving, honing, and grinding). The test gears were manufactured in case-hardened steel, similar to 20MnCrS5. Surface topography measurements were used as input to a contact analysis boundary element software program. An important hypothesis used in this work is that the dry elastic contact area ratio, i.e. the ratio between real and nominal contact area, can be used as a measure of the contact conditions in gears. It is concluded that running-in differs significantly for the studied manufacturing methods and that the dry elastic contact area ratio gives a consistent description of these changes. The shaved gears have the highest dry elastic contact area ratio after running in, where the ground gears have the lowest dry elastic contact area ratio. The increase in dry elastic contact area ratio is about 30 per cent for the shaved gears, 12 per cent for the honed gears and less than 5 per cent for the ground gears. Extreme value parameters, such as Rp and Rz, showed relatively good correlation to dry elastic contact area ratio. However no genuine correlation could be found between dry elastic contact area ratio and two-dimensional (2D) surface roughness parameters. Furthermore, traditional gear metrology form parameters do not serve as a good measure on the changes occurring during the running-in.
Tribology International, 2012
ABSTRACT
Strojniški vestnik, 2010
Gear tooth modifications, such as lead crowning, are often recommended to compensate for misalign... more Gear tooth modifications, such as lead crowning, are often recommended to compensate for misalignment (e.g. assembly deviations). Lead crowning means that the tooth centre is slightly thicker than ...
A new general linear contact-interaction model is derived for treating the dynamic excitation tha... more A new general linear contact-interaction model is derived for treating the dynamic excitation that is due to the rolling contact of rough surfaces. It is shown that the relative-displacement and blockedforce models are special cases of this model. A numerical contactcomputation program is utilised to compute the parameters of the contact-interaction model. This program accounts for the detailed surface geometry within the contact region. Furthermore, since contact between rough surfaces is accompanied by locally high stresses, an approximate method for treating plasticity is integrated in to the contact-computation program. The non-stationary response of the contacting bodies is accounted for by a state-space formulation, utilising a modal representation of the dynamic response of the two structures, respectively. As a consequence, the parameters of the contactinteraction model have to be time-dependent. This is dealt with by employing a Monte-Carlo procedure that generates representative time-dependent parameters.
Wear, 2003
Engineering surfaces can be characterized as more or less randomly rough. Contact between enginee... more Engineering surfaces can be characterized as more or less randomly rough. Contact between engineering surfaces is thus discontinuous and the real area of contact is a small fraction of the nominal contact area. The stiffness of a rough surface layer thus influences the contact state as well as the behavior of the surrounding system. A contact model that takes the properties of engineering surfaces into account has been developed and implemented using finite element software. The results obtained with the model have been verified by comparison with results from an independent numerical method. The results show that the height distribution of the topography has a significant influence on the contact stiffness but that the curvature of the roughness is of minor importance. The contact model that was developed for determining the apparent contact area and the distribution of the mean contact pressure could thus be based on a limited set of height parameters that describe the surface topography. By operating on the calculated apparent pressure distribution with a transformation function that is based on both height and curvature parameters, the real contact area can be estimated when the apparent contact state is known. The model presented is also valid for cases with local plastic flow in the bulk material.
Wear, 1994
Our understanding of the mechanics of contact behaviour for interacting particles has been develo... more Our understanding of the mechanics of contact behaviour for interacting particles has been developed mostly assuming that surfaces are smooth. However, real particles of interest in engineering science are generally rough. While recent studies have considered the influence of roughness on the normal force-displacement relationship, surface roughness was quantified using only a single scalar measure, disregarding the topology of the surface. There are some conflicting arguments concerning the effect of roughness on the tangential or shear force-displacement relationship. In this study, optical interferometry data are used to generate the surface topology for input into a 3D finite element model. This model is used to investigate the sensitivity of the normal force-displacement response to the surface topology by considering different surfaces with similar overall roughness values. The effect of surface roughness on the tangential force-displacement relationship and the influence of loading history are also explored. The results indicate that quantifying roughness using a single value, such as the root mean square height of roughness, S q , is insufficient to predict the effect of roughness upon stiffness. It is also shown that in the absence of interlocking, rough particle surfaces exhibit a lower frictional resistance in comparison with equivalent smooth surfaces.
A well-defined rolling contact problem is studied with the intention to cover interesting aspects... more A well-defined rolling contact problem is studied with the intention to cover interesting aspects of tyre-road contact modeling and rolling contact in general. More specifically, the dynamic response in a steel beam caused by a steel ball rolling over it is studied by theoretical modeling of the beam-and ball dynamics as well as the contact forces. Validation of the dynamic response simulations is achieved by comparison with measurements. The contact model is shown to be greatly dependent on an accurate estimate of the real contact stiffness. A method to estimate the contact stiffness which leads to good accuracy in dynamic response simulations is presented. Although the contact stiffness is significantly lower for rubber-asphalt interaction than for steel-steel contact, the results give useful insight for tyre-road contact modeling.
Tribology International, 2007
Friction, lubrication, and wear have a strong influence on the performance and behavior of mechan... more Friction, lubrication, and wear have a strong influence on the performance and behavior of mechanical systems. This paper deals with different friction models for sliding contacts running under different conditions. The models presented are suited to different situations, depending on the type of contact, running conditions, and the behavior of interest. The models will be discussed from simulation and tribological points of view. The different types of friction models considered are: friction models for transient sliding under dry, boundary and mixed lubrication conditions, friction models for micro-displacements of engineering surfaces subjected to transient sliding, friction models often used in the simulation and control of technical systems, combined friction models that represent physical behaviors fairly well but are also suitable for use in simulating systems, friction models that take into account the stochastic nature of interacting surface asperities.
Tribology International, 2007
The topography of the active surfaces in rolling contact depends on the surface roughness obtaine... more The topography of the active surfaces in rolling contact depends on the surface roughness obtained by different manufacturing process technology (turning, grinding, polishing, lapping, etc.). The aim of this paper work is to evidence the influence of the surface roughness on surface geometry of rolling contacts. The experimental tests were carried out on the AMSLER machine and an experimental setup for pure rolling motion. The surfaces of the rolling samples were analyzed with SEM (scanning electron microscopy) and EDS (energy dispersive X-ray spectroscopy) techniques for structural and chemical analysis and measured with the Taylor Hobson profilometer before and after the experimental tests for surface topography.
Procedia CIRP, 2018
In today's business environment, the trend towards more product variety and customization is unbr... more In today's business environment, the trend towards more product variety and customization is unbroken. Due to this development, the need of agile and reconfigurable production systems emerged to cope with various products and product families. To design and optimize production systems as well as to choose the optimal product matches, product analysis methods are needed. Indeed, most of the known methods aim to analyze a product or one product family on the physical level. Different product families, however, may differ largely in terms of the number and nature of components. This fact impedes an efficient comparison and choice of appropriate product family combinations for the production system. A new methodology is proposed to analyze existing products in view of their functional and physical architecture. The aim is to cluster these products in new assembly oriented product families for the optimization of existing assembly lines and the creation of future reconfigurable assembly systems. Based on Datum Flow Chain, the physical structure of the products is analyzed. Functional subassemblies are identified, and a functional analysis is performed. Moreover, a hybrid functional and physical architecture graph (HyFPAG) is the output which depicts the similarity between product families by providing design support to both, production system planners and product designers. An illustrative example of a nail-clipper is used to explain the proposed methodology. An industrial case study on two product families of steering columns of thyssenkrupp Presta France is then carried out to give a first industrial evaluation of the proposed approach.
The purpose of this work-package within the Quiet-track, FP7, is to develop a noise related track... more The purpose of this work-package within the Quiet-track, FP7, is to develop a noise related track maintenance tool, in the form of an on-board measurement system. As a first step, lab scale tests u ...
Wear, 1996
Mild wear may have damaging effects on contacting components, when the material removal distorts ... more Mild wear may have damaging effects on contacting components, when the material removal distorts component geometry. Surface pressures can then be redistributed in an unfavoumblc way which increases the i~-ohability for surface fatigue, Phenomena like this have Men observed in an ordinary automotive cam-follower contort. The purpose of this work is m derive a simulation model for the mild wear in a nam-foliower contact with follower rotation. The mild wear in such a contact is simulated using the pdnci#e of single point observation. The simulation model is based on a modified Archerd's wear equation. After each simulation step the pressures am recalculated using the topographically changed surfaces. Three eases are studied: one where only follower wear is considered, one where only the cam wear is simulated and finally the case where both cam and f,]lower wear is simulated. An FEM analysis of the follower was used to verify the infinite half plane assumption in the pressare calculations. The present work highlights the importance of including follower relation in the wear simulation and the use of the single point observation method in the derivation of a wear simulation model. The results show that the ease whom only the cam is worn gives the lowest contact pressures. The case where only follower wear is considered is the most unfavnnrablo when it comes to contact pressures and wear.
Wear, 2000
Owing to the curved contact surfaces in a spherical roller thrust bearing, the rollers will under... more Owing to the curved contact surfaces in a spherical roller thrust bearing, the rollers will undergo sliding. For an unskewed roller there will be two points along each contact where the sliding velocity is zero. At all other points along the contact, sliding is present. Under boundary lubricated conditions the sliding can give rise to mild wear. Experimental results show that this wear can cause a significant change in the surface profile outside the zero sliding points. The mild wear in the contact was simulated using Archard's wear law. An iterative wear model is described in which the normal load distribution, the tangential tractions and the sliding distances are repeatedly calculated to simulate the changes in surface geometry due to wear. Good qualitative agreement was achieved between the simulation results and the previously presented experimental results.
Journal of Tribology, 2006
The contact area and pressure distribution in a wheel/rail contact is essential information requi... more The contact area and pressure distribution in a wheel/rail contact is essential information required in any fatigue or wear calculations to determine design life, re-grinding, and maintenance schedules. As wheel or rail wear or surface damage takes place the contact patch size and shape will change. This leads to a redistribution of the contact stresses. The aim of this work was to use ultrasound to nondestructively quantify the stress distribution in new, worn, and damaged wheel-rail contacts. The response of a wheel/rail interface to an ultrasonic wave can be modeled as a spring. If the contact pressure is high the interface is very stiff, with few air gaps, and allows the transmission of an ultrasonic sound wave. If the pressure is low, interfacial stiffness is lower and almost all the ultrasound is reflected. A quasistatic spring model was used to determine maps of contact stiffness from wheel/rail ultrasonic reflection data. Pressure was then determined using a parallel calibra...
International Journal of Machine Tools and Manufacture, 1998
Wear of boundary lubricated spherical roller thrust bearings has been characterised with 3-D surf... more Wear of boundary lubricated spherical roller thrust bearings has been characterised with 3-D surface measurements and analysis. Due to the curved contact surface in a spherical roller thrust bearing, the rollers will undergo sliding in the contact. For an unskewed roller there will ...
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2011
ABSTRACT Striving for higher gear transmission efficiency by using a low-viscosity transmission l... more ABSTRACT Striving for higher gear transmission efficiency by using a low-viscosity transmission lubricant affects the lubricant film thickness. To keep the Λ-ratio (the ratio between the film thickness and the surface roughness) intact, more effort must be put on the surface topography. This paper presents a study of how running-in affects the dry elastic contact area ratio in spur gears using real surface topographies from three common manufacturing methods (green-shaving, honing, and grinding). The test gears were manufactured in case-hardened steel, similar to 20MnCrS5. Surface topography measurements were used as input to a contact analysis boundary element software program. An important hypothesis used in this work is that the dry elastic contact area ratio, i.e. the ratio between real and nominal contact area, can be used as a measure of the contact conditions in gears. It is concluded that running-in differs significantly for the studied manufacturing methods and that the dry elastic contact area ratio gives a consistent description of these changes. The shaved gears have the highest dry elastic contact area ratio after running in, where the ground gears have the lowest dry elastic contact area ratio. The increase in dry elastic contact area ratio is about 30 per cent for the shaved gears, 12 per cent for the honed gears and less than 5 per cent for the ground gears. Extreme value parameters, such as Rp and Rz, showed relatively good correlation to dry elastic contact area ratio. However no genuine correlation could be found between dry elastic contact area ratio and two-dimensional (2D) surface roughness parameters. Furthermore, traditional gear metrology form parameters do not serve as a good measure on the changes occurring during the running-in.
Tribology International, 2012
ABSTRACT