Recent experiments and analyses have revealed that threaded fasteners subjected to axial vibration can experience either loosening or tightening. In this paper, the authors examine the variation of clamping force in a single-bolt assembly model due to axial vibration. Specifically, the effect of vibration level and initial pre-load on clamping force is studied. It is found that the clamping force can remain steady, decrease, or increase when the assembly is subjected to axial vibration. However, changes in clamping force are generally transient and a steady value is reached over time.
{"title":"Variation of Clamping Force in a Single-Bolt Assembly Subjected to Axial Vibration","authors":"D. Hess, Srinivas Basava, I. Rasquinha","doi":"10.1115/imece1996-0019","DOIUrl":"https://doi.org/10.1115/imece1996-0019","url":null,"abstract":"\u0000 Recent experiments and analyses have revealed that threaded fasteners subjected to axial vibration can experience either loosening or tightening. In this paper, the authors examine the variation of clamping force in a single-bolt assembly model due to axial vibration. Specifically, the effect of vibration level and initial pre-load on clamping force is studied. It is found that the clamping force can remain steady, decrease, or increase when the assembly is subjected to axial vibration. However, changes in clamping force are generally transient and a steady value is reached over time.","PeriodicalId":267384,"journal":{"name":"Elasto-Impact and Friction in Dynamic Systems","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124587383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper gives a short account on the experimental and numerical study of a piecewise based excited symmetrical linear oscillator undergoing non-linear vibrations. The details of the adopted design and the state-of-the-art experimental setup are explained in a great detail. The regions of chaotic motion predicted theoretically were confirmed by the experimental results arranged into bifurcation diagrams, which were obtained by numerical and experimental means. Clearance and amplitude of the external force were used as branching parameters. The discussion of the system’s dynamics is based on bifurcation diagrams, Lissajous curves and power spectrums. The investigated system tended to be periodic for large clearances and chaotic small ones. This is picture is reversed for the amplitude of the forcing, where periodic motion occurred for its small values and chaos dominated for larger forcing.
{"title":"Experimental and Numerical Study of a Symmetrically Piecewise Linear Oscillator","authors":"V. Sin, M. Wiercigroch","doi":"10.1115/imece1996-0015","DOIUrl":"https://doi.org/10.1115/imece1996-0015","url":null,"abstract":"\u0000 The paper gives a short account on the experimental and numerical study of a piecewise based excited symmetrical linear oscillator undergoing non-linear vibrations. The details of the adopted design and the state-of-the-art experimental setup are explained in a great detail. The regions of chaotic motion predicted theoretically were confirmed by the experimental results arranged into bifurcation diagrams, which were obtained by numerical and experimental means. Clearance and amplitude of the external force were used as branching parameters. The discussion of the system’s dynamics is based on bifurcation diagrams, Lissajous curves and power spectrums. The investigated system tended to be periodic for large clearances and chaotic small ones. This is picture is reversed for the amplitude of the forcing, where periodic motion occurred for its small values and chaos dominated for larger forcing.","PeriodicalId":267384,"journal":{"name":"Elasto-Impact and Friction in Dynamic Systems","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125646031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nonsmooth dynamical systems become increasingly important in engineering and other applied sciences since nonsmooth effects are taken into account and are no longer smoothed out. Due to the lack of smoothness, classical mathematical methods are not or only limited applicable and require often extensions in order to apply analytical and numerical methods. In mechanical systems the consideration of e.g. friction and impacts leads to discontinuities in the corresponding mathematical models. In the proposed paper different methods will be applied, based either on models or on measured or simulated time signals. The investigation comprises a friction oscillator with self- and external excitation and a simple impact oscillator. The methods under consideration are one-dimensional maps, bifurcation and stability analysis, the determination of Lyapunov exponents, and the phase-space reconstruction by the help of general mutual information and false nearest neighbours.
{"title":"Signal and Model Based Analysis of Systems With Friction and Impacts","authors":"M. Oestreich, Nikolaus Hinrichs, K. Popp","doi":"10.1115/imece1996-0009","DOIUrl":"https://doi.org/10.1115/imece1996-0009","url":null,"abstract":"\u0000 Nonsmooth dynamical systems become increasingly important in engineering and other applied sciences since nonsmooth effects are taken into account and are no longer smoothed out. Due to the lack of smoothness, classical mathematical methods are not or only limited applicable and require often extensions in order to apply analytical and numerical methods. In mechanical systems the consideration of e.g. friction and impacts leads to discontinuities in the corresponding mathematical models.\u0000 In the proposed paper different methods will be applied, based either on models or on measured or simulated time signals. The investigation comprises a friction oscillator with self- and external excitation and a simple impact oscillator.\u0000 The methods under consideration are one-dimensional maps, bifurcation and stability analysis, the determination of Lyapunov exponents, and the phase-space reconstruction by the help of general mutual information and false nearest neighbours.","PeriodicalId":267384,"journal":{"name":"Elasto-Impact and Friction in Dynamic Systems","volume":"67 6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122891540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The flexural vibration of a beam-like structure damped with a displacement-dependent Coulomb friction force is examined. Due to the geometry of the dry friction damping element, the friction force grows linearly with the beam’s transverse displacement. Recent studies have shown that the damping of systems with displacement-dependent dry friction forces resembles linear structural damping. Taking advantage of this fact, the energy loss per cycle can be made to grow like the square of the vibratory displacement amplitude rather than linearly with amplitude as in the case of frictionally damped systems with constant normal forces. Furthermore, dry friction is well suited to hostile environments such as the high temperatures and high rotation speeds associated with gas turbines. These observations suggest that displacement-dependent dry friction may be an effective means of flutter suppression in turbine and fan blade applications. Destabilizing aerodynamic forces are represented in this study as negative viscous damping. This simple aerodynamic model is often used to capture the basic features of flutter in aeroelastic systems. Both single and multiple-mode analyses are conducted. Results show that energy losses from the displacement-dependent dry friction damper are large enough to overcome the destabilizing negative viscous damping under certain conditions. This result further suggests that it may be possible to design the geometry and location of frictional interfaces in turbine blade systems so that damping may be enhanced and flutter better controlled.
{"title":"Stability and Forced Response of Beam-Like Structures Having Negative Viscous Damping and Displacement-Dependent Dry Friction Damping","authors":"W. Whiteman, A. Ferri","doi":"10.1115/imece1996-0013","DOIUrl":"https://doi.org/10.1115/imece1996-0013","url":null,"abstract":"\u0000 The flexural vibration of a beam-like structure damped with a displacement-dependent Coulomb friction force is examined. Due to the geometry of the dry friction damping element, the friction force grows linearly with the beam’s transverse displacement. Recent studies have shown that the damping of systems with displacement-dependent dry friction forces resembles linear structural damping. Taking advantage of this fact, the energy loss per cycle can be made to grow like the square of the vibratory displacement amplitude rather than linearly with amplitude as in the case of frictionally damped systems with constant normal forces. Furthermore, dry friction is well suited to hostile environments such as the high temperatures and high rotation speeds associated with gas turbines. These observations suggest that displacement-dependent dry friction may be an effective means of flutter suppression in turbine and fan blade applications. Destabilizing aerodynamic forces are represented in this study as negative viscous damping. This simple aerodynamic model is often used to capture the basic features of flutter in aeroelastic systems. Both single and multiple-mode analyses are conducted. Results show that energy losses from the displacement-dependent dry friction damper are large enough to overcome the destabilizing negative viscous damping under certain conditions. This result further suggests that it may be possible to design the geometry and location of frictional interfaces in turbine blade systems so that damping may be enhanced and flutter better controlled.","PeriodicalId":267384,"journal":{"name":"Elasto-Impact and Friction in Dynamic Systems","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130364101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper addresses the effects of a compliant contact on the dynamical friction behaviors in mechanical systems. Contact compliance is due to the elastic deformation at the contact point or the surrounding structure. This paper is divided into two parts. The first part focuses on oscillations with continuous macroscopic sliding. An idealized model consisting of a mass sliding harmonically on a massless compliant contact produces the hysteresis feature seen in friction-velocity plots. Transition features, depending on the contact stiffness, friction level, and frequency/amplitude of oscillation, are predicted and quantified. Experiments have been conducted to verify the model. The model and associated analysis provide a means for interpreting experimental transition behaviors. The second part of the paper addresses the sticking dynamics associated with a macroscopic stick-slip process. During a stick, the mass undergoes a microscopic oscillation at the contact. This can involve a microscale stick-slip process. We refer to the entire process as a double stick-slip event. Numerical and experimental studies are compared.
{"title":"The Effects of Tangential Contact Stiffness on a Harmonically Forced Friction Oscillator","authors":"J. Liang, B. Feeny","doi":"10.1115/imece1996-0018","DOIUrl":"https://doi.org/10.1115/imece1996-0018","url":null,"abstract":"\u0000 This paper addresses the effects of a compliant contact on the dynamical friction behaviors in mechanical systems. Contact compliance is due to the elastic deformation at the contact point or the surrounding structure. This paper is divided into two parts. The first part focuses on oscillations with continuous macroscopic sliding. An idealized model consisting of a mass sliding harmonically on a massless compliant contact produces the hysteresis feature seen in friction-velocity plots. Transition features, depending on the contact stiffness, friction level, and frequency/amplitude of oscillation, are predicted and quantified. Experiments have been conducted to verify the model. The model and associated analysis provide a means for interpreting experimental transition behaviors.\u0000 The second part of the paper addresses the sticking dynamics associated with a macroscopic stick-slip process. During a stick, the mass undergoes a microscopic oscillation at the contact. This can involve a microscale stick-slip process. We refer to the entire process as a double stick-slip event. Numerical and experimental studies are compared.","PeriodicalId":267384,"journal":{"name":"Elasto-Impact and Friction in Dynamic Systems","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114402505","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study introduces an algorithm for the simultaneous estimation of Coulomb and viscous damping effects from free-vibration decrements in a damped linear single degree-of-freedom (DOF) mass-spring system. Numerical and experimental estimations are included. The algorithm complements existing ideas for the estimation of either viscous or Coulomb as the sole damping source in a system. Analysis shows that both damping effects can indeed be separated. Numerical study of a combined-damping system demonstrates a perfect match between the simulation parameters and the estimated values. Experimental study includes two types of real systems. Experimental results illustrate the reliability of this method. An analysis provides conservative bounds on different estimations errors.
{"title":"Estimating Coulomb and Viscous Friction From Free-Vibration Decrements","authors":"J. Liang, B. Feeny","doi":"10.1115/imece1996-0011","DOIUrl":"https://doi.org/10.1115/imece1996-0011","url":null,"abstract":"\u0000 This study introduces an algorithm for the simultaneous estimation of Coulomb and viscous damping effects from free-vibration decrements in a damped linear single degree-of-freedom (DOF) mass-spring system. Numerical and experimental estimations are included. The algorithm complements existing ideas for the estimation of either viscous or Coulomb as the sole damping source in a system. Analysis shows that both damping effects can indeed be separated. Numerical study of a combined-damping system demonstrates a perfect match between the simulation parameters and the estimated values. Experimental study includes two types of real systems. Experimental results illustrate the reliability of this method. An analysis provides conservative bounds on different estimations errors.","PeriodicalId":267384,"journal":{"name":"Elasto-Impact and Friction in Dynamic Systems","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121070790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Modal survey testing of the Space Station Common Module Prototype in a test fixture designed to simulate Shuttle Orbiter constraints revealed a number of sources of nonlinearities in the measured frequency response functions. First, the test fixture original design, which utilized spherical bearing joints and an airbag suspension system for offloading the test article weight, is described in detail in order to provide a basis for understanding the test data. Several experimental and analytical lowest-frequency mode shapes are compared, and differences are pointed out. One of the basic modes predicted by the finite element model was not observed at all in the experimental data. Then the measured acceleration/force frequency response functions are examined for different shaker force amplitudes and air pressure levels in the airbag offload system. It is shown that the character of the response functions, and the mode shapes and frequencies of the Common Module, varied depending on the test parameters. Static stiffness and stick-slip measurements for the fixture-to-test-article interfaces were made to provide insight into the behavior of the bearing mechanisms. Careful examination of the experimental mode shapes, frequency responses, static stiffness curves, and bearing stick-slip data led to a determination that the spherical joint interfaces between the Common Module test article and the test fixture were not functioning as designed. Friction in some interface joints prevented relative motion between the test article and fixture that was essential for simulating Shuttle Orbiter constraints of the Common Module in its flight configuration. In other instances, clearances between the spherical bearings and the surfaces of the test article interface structures caused highly nonlinear response as a function of load at the interface. The severity of the unintended joint friction and clearances and the resulting nonlinearities made necessary a redesign of the modal test fixture in the interface regions before the flight constraints of the test article could be adequately simulated.
{"title":"Nonlinearities due to Joint Friction and Clearance in a Structural Dynamic Test Fixture","authors":"M. Tinker","doi":"10.1115/imece1996-0012","DOIUrl":"https://doi.org/10.1115/imece1996-0012","url":null,"abstract":"\u0000 Modal survey testing of the Space Station Common Module Prototype in a test fixture designed to simulate Shuttle Orbiter constraints revealed a number of sources of nonlinearities in the measured frequency response functions. First, the test fixture original design, which utilized spherical bearing joints and an airbag suspension system for offloading the test article weight, is described in detail in order to provide a basis for understanding the test data. Several experimental and analytical lowest-frequency mode shapes are compared, and differences are pointed out. One of the basic modes predicted by the finite element model was not observed at all in the experimental data. Then the measured acceleration/force frequency response functions are examined for different shaker force amplitudes and air pressure levels in the airbag offload system. It is shown that the character of the response functions, and the mode shapes and frequencies of the Common Module, varied depending on the test parameters. Static stiffness and stick-slip measurements for the fixture-to-test-article interfaces were made to provide insight into the behavior of the bearing mechanisms.\u0000 Careful examination of the experimental mode shapes, frequency responses, static stiffness curves, and bearing stick-slip data led to a determination that the spherical joint interfaces between the Common Module test article and the test fixture were not functioning as designed. Friction in some interface joints prevented relative motion between the test article and fixture that was essential for simulating Shuttle Orbiter constraints of the Common Module in its flight configuration. In other instances, clearances between the spherical bearings and the surfaces of the test article interface structures caused highly nonlinear response as a function of load at the interface. The severity of the unintended joint friction and clearances and the resulting nonlinearities made necessary a redesign of the modal test fixture in the interface regions before the flight constraints of the test article could be adequately simulated.","PeriodicalId":267384,"journal":{"name":"Elasto-Impact and Friction in Dynamic Systems","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125365760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An experimental analysis was conducted to study the rebound velocities of a freely dropped bar on a large external surface. The low velocity collision occured in the presence of a frictional impact. A 3D motion analysis system was used to capture the kinematic data. Tests were performed for central and oblique collisions. A spatial theoretical model is presented for the impact with friction of a flexible body. This model consists of a system of nonlinear differential equations which considers the multiple collisions as well as frictional effects at the contacting end, and allows one to predict the rigid and elastic body motion after the impact. The model uses a dry coefficient of friction, a nonlinear contact force, and the sound radiation from the impact. Analytical and experimental results were compared to establish the accuracy of the model.
{"title":"Spatial Impact of a Flexible Link Using a Nonlinear Contact Force","authors":"D. Marghitu, D. Boghiu","doi":"10.1115/imece1996-0020","DOIUrl":"https://doi.org/10.1115/imece1996-0020","url":null,"abstract":"\u0000 An experimental analysis was conducted to study the rebound velocities of a freely dropped bar on a large external surface. The low velocity collision occured in the presence of a frictional impact. A 3D motion analysis system was used to capture the kinematic data. Tests were performed for central and oblique collisions. A spatial theoretical model is presented for the impact with friction of a flexible body. This model consists of a system of nonlinear differential equations which considers the multiple collisions as well as frictional effects at the contacting end, and allows one to predict the rigid and elastic body motion after the impact. The model uses a dry coefficient of friction, a nonlinear contact force, and the sound radiation from the impact. Analytical and experimental results were compared to establish the accuracy of the model.","PeriodicalId":267384,"journal":{"name":"Elasto-Impact and Friction in Dynamic Systems","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122062996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Experimental measurements of dry friction between sliding surfaces under harmonic excitation show that the friction force consists of periodic components with superimposed random fluctuations. The stochastic nature of the friction can be Gaussian or non-Gaussian, depending on the normal force and excitation amplitude levels. The normal force experiences random fluctuations due to ploughing and generation of surface asperities. The main influence of friction damping on the system response has been examined under different levels of normal loading. It is found that with increasing normal force the relative displacement deviates from the original sinusoidal nature and becomes essentially nonlinear with periodic motion. Regions of high displacement show this nonlinear behavior, which experiences extensively stick-slip with increasing normal force. Numerical simulation results are found to be in good agreement with experimental results.
{"title":"Stochastic Description of Dry Friction in Metal-to-Metal Contact Under Harmonic Excitation","authors":"S. Zielke, R. Ibrahim, K. Popp","doi":"10.1115/imece1996-0010","DOIUrl":"https://doi.org/10.1115/imece1996-0010","url":null,"abstract":"\u0000 Experimental measurements of dry friction between sliding surfaces under harmonic excitation show that the friction force consists of periodic components with superimposed random fluctuations. The stochastic nature of the friction can be Gaussian or non-Gaussian, depending on the normal force and excitation amplitude levels. The normal force experiences random fluctuations due to ploughing and generation of surface asperities. The main influence of friction damping on the system response has been examined under different levels of normal loading. It is found that with increasing normal force the relative displacement deviates from the original sinusoidal nature and becomes essentially nonlinear with periodic motion. Regions of high displacement show this nonlinear behavior, which experiences extensively stick-slip with increasing normal force. Numerical simulation results are found to be in good agreement with experimental results.","PeriodicalId":267384,"journal":{"name":"Elasto-Impact and Friction in Dynamic Systems","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121201937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Friction induced self-sustained oscillations, also known as stick-slip vibrations, occur in mechanical systems as well as in everyday life. Examples are stick-slip motions which lead to squealing railway wheels, grating brakes, rattling machine tools or the cozy sound of a violin. The robust limit cycles of stick-slip motions can be broken up by an additional harmonic external excitation. The extended nonsmooth system of a friction oscillator including a nonsmooth friction law and an additional external excitation shows rich bifurcational behaviour. On the basis of a one-dimensional map stability analysis and the determination of Lyapunov exponents has been carried out similar to the logistic map (Oestreich et al., 1996a). The present paper focuses on the comparison of the dynamical behaviour of a simple mechanical model and the dynamics observed in experiments. Since in engineering systems the friction characteristic is often not known or is varying for different test parameters, first the friction characteristic is determined from experiments with different test conditions. In the next step the results of the simulations using the identified friction characteristics will be compared with measurements of the dynamics of the friction oscillator with pure external excitation, pure self-excitation and simultaneous self- and external excitation. An additional verification of the identified friction characteristic can be done by means of a comparison of phase curves, trajectories in the three dimensional state space and bifurcation diagrams.
{"title":"Experimental and Numerical Investigation of a Friction Oscillator","authors":"Nikolaus Hinrichs, M. Oestreich, K. Popp","doi":"10.1115/imece1996-0014","DOIUrl":"https://doi.org/10.1115/imece1996-0014","url":null,"abstract":"\u0000 Friction induced self-sustained oscillations, also known as stick-slip vibrations, occur in mechanical systems as well as in everyday life. Examples are stick-slip motions which lead to squealing railway wheels, grating brakes, rattling machine tools or the cozy sound of a violin. The robust limit cycles of stick-slip motions can be broken up by an additional harmonic external excitation. The extended nonsmooth system of a friction oscillator including a nonsmooth friction law and an additional external excitation shows rich bifurcational behaviour. On the basis of a one-dimensional map stability analysis and the determination of Lyapunov exponents has been carried out similar to the logistic map (Oestreich et al., 1996a).\u0000 The present paper focuses on the comparison of the dynamical behaviour of a simple mechanical model and the dynamics observed in experiments. Since in engineering systems the friction characteristic is often not known or is varying for different test parameters, first the friction characteristic is determined from experiments with different test conditions. In the next step the results of the simulations using the identified friction characteristics will be compared with measurements of the dynamics of the friction oscillator with pure external excitation, pure self-excitation and simultaneous self- and external excitation. An additional verification of the identified friction characteristic can be done by means of a comparison of phase curves, trajectories in the three dimensional state space and bifurcation diagrams.","PeriodicalId":267384,"journal":{"name":"Elasto-Impact and Friction in Dynamic Systems","volume":"133 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133067197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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