Pub Date : 2020-06-30DOI: 10.46720/8442002eb2020-ebs-017
C. Holtmann
In electric vehicle applications, the braking technology has changed so that a part of the kinetic energy can be fed back into the battery with the traction machine. However in the case of an emergency brake the required braking power in a car is about 8 times and in commercial vehicle applications about 30 times higher than the drive power rating. This circumstance is the reason for the continued necessity of mechanical friction brakes. In large commercial vehicle applications, retarder technologies have a long history of reducing the wear of the mechanical brakes and the maintenance costs. The combination of the electric drive train with a retarder allows to reduce the required size of a mechanical friction brake dramatically. However, the power density of retarders, especially of eddy current retarders are small compared to mechanical friction brakes. The reason for this is the need for a heavy magnetic excitation circuit, while mechanical brakes in addition to the brake disc only need a caliper. From an electromagnetic point of view, the power density of eddy current brakes has been increased by various measures. One of the most effective measures to increase power density from an electromagnetic viewpoint is to apply a thin layer of highly conductive material to the surface of the active eddy current material, as shown in [1]. However, when this type of eddy current brake is optimized for high speeds, the power density is limited by the thermal behavior. From a thermal point of view conventional eddy current brakes are comparable to mechanical brakes because the braking power is converted to heat in a solid disc. Also in detail, both are comparable, since the skin effect ensures that the heat arises as in a mechanical friction brake only in a thin layer on the material surface of the disc. In consequence conventional eddy current brakes can never reach the power density of mechanical friction brakes. In order to reduce the possibility of overheating, a patent [2] describes a liquid-cooled eddy current brake which can also be flooded from the rotor side with water to cool the eddy-current material. The disadvantage of this eddy current brake is that the rotor rotates in the water and the torque cannot be controlled quickly. Another possibility is to place small cooling channels near the surface where the eddy currents occur, as shown in [3], but the cooling channels near the surface weaken the primary magnetic field and the torque density decreases.In this work, an eddy current brake with a magneto-isotropic material structure that eliminates the skin effect is shown. The eddy currents and the heat are thus distributed almost homogeneously in the material. The material structure consists of steel pins that transfer the magnetic flux from the poles through perforated aluminum sheets [4]. Coolant flows between the aluminum sheets and the number and thickness of the sheets can be selected almost freely, thereby dramatically increasing the surfac
{"title":"Design and Optimization Method for a High Power Eddy Current Brake with a Magneto-isotropic Material Structure for the Use in Electrified Heavy Duty Trucks","authors":"C. Holtmann","doi":"10.46720/8442002eb2020-ebs-017","DOIUrl":"https://doi.org/10.46720/8442002eb2020-ebs-017","url":null,"abstract":"In electric vehicle applications, the braking technology has changed so that a part of the kinetic energy can be fed back into the battery with the traction machine. However in the case of an emergency brake the required braking power in a car is about 8 times and in commercial vehicle applications about 30 times higher than the drive power rating. This circumstance is the reason for the continued necessity of mechanical friction brakes. In large commercial vehicle applications, retarder technologies have a long history of reducing the wear of the mechanical brakes and the maintenance costs. The combination of the electric drive train with a retarder allows to reduce the required size of a mechanical friction brake dramatically. However, the power density of retarders, especially of eddy current retarders are small compared to mechanical friction brakes. The reason for this is the need for a heavy magnetic excitation circuit, while mechanical brakes in addition to the brake disc only need a caliper. From an electromagnetic point of view, the power density of eddy current brakes has been increased by various measures. One of the most effective measures to increase power density from an electromagnetic viewpoint is to apply a thin layer of highly conductive material to the surface of the active eddy current material, as shown in [1]. However, when this type of eddy current brake is optimized for high speeds, the power density is limited by the thermal behavior. From a thermal point of view conventional eddy current brakes are comparable to mechanical brakes because the braking power is converted to heat in a solid disc. Also in detail, both are comparable, since the skin effect ensures that the heat arises as in a mechanical friction brake only in a thin layer on the material surface of the disc. In consequence conventional eddy current brakes can never reach the power density of mechanical friction brakes. In order to reduce the possibility of overheating, a patent [2] describes a liquid-cooled eddy current brake which can also be flooded from the rotor side with water to cool the eddy-current material. The disadvantage of this eddy current brake is that the rotor rotates in the water and the torque cannot be controlled quickly. Another possibility is to place small cooling channels near the surface where the eddy currents occur, as shown in [3], but the cooling channels near the surface weaken the primary magnetic field and the torque density decreases.In this work, an eddy current brake with a magneto-isotropic material structure that eliminates the skin effect is shown. The eddy currents and the heat are thus distributed almost homogeneously in the material. The material structure consists of steel pins that transfer the magnetic flux from the poles through perforated aluminum sheets [4]. Coolant flows between the aluminum sheets and the number and thickness of the sheets can be selected almost freely, thereby dramatically increasing the surfac","PeriodicalId":254446,"journal":{"name":"EuroBrake 2020 Technical Programme","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125949142","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}
JSAE restructured its organization to mirror the committees of ISO/TC22 in year 2015.Sustained for many years, JSAE Brake Linings WG consists of 2 laboratories, 10 vehicle and 8 automobile part manufactures.And it promotes activities corresponding to WG10 "Brake Linings and Friction Couples”. Early year 2020, JSAE issued a JASO (Japanese Automotive Standards Organization) standard for brake particle emission measurement and MPU. JSAE would like to introduce it along with the latest activity situation, focus points on standardization, and future policy of activities.
{"title":"JSAE Standardization Activities Update","authors":"Masaki Hayakawa, Shigeru Sakamoto, Masato Yamaguchi, Yuzo Todani, Naoki Hata, Tatsushi Ishikawa","doi":"10.46720/9107873eb2020-ebs-009","DOIUrl":"https://doi.org/10.46720/9107873eb2020-ebs-009","url":null,"abstract":"JSAE restructured its organization to mirror the committees of ISO/TC22 in year 2015.Sustained for many years, JSAE Brake Linings WG consists of 2 laboratories, 10 vehicle and 8 automobile part manufactures.And it promotes activities corresponding to WG10 \"Brake Linings and Friction Couples”. Early year 2020, JSAE issued a JASO (Japanese Automotive Standards Organization) standard for brake particle emission measurement and MPU. JSAE would like to introduce it along with the latest activity situation, focus points on standardization, and future policy of activities.","PeriodicalId":254446,"journal":{"name":"EuroBrake 2020 Technical Programme","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121625714","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}
Pub Date : 2020-06-30DOI: 10.46720/4016435eb2020-ebs-007
Sangbum Kim, I. Park, C. Park
As the demand for passenger cars that are equipped with EPB(electric parking brake) system increases, the automotive parts companies have tried to develop the EPB on all vehicle. As the range of EPB application expands, customer demand for noise reduction during EPB operation also increases. In order to reduce the EPB operating noise, the optimum design of the EPB actuator two-step train gear was carried out. First of all, three gear design factors, such as pressure angle, helical angle, and gear type, were changed to verify the impact on EPB operation noise. As a result of this, the change of transmission error, contact ratio and specific speed were confirmed using KISSSOFT which is gear analysis program. Theoretically, the gear train which has small transmission error, large contact ratio, certain specific slide(-3~+3) is advantageous for noise reduction. As a result of the analysis, it was confirmed that the transmission error is reduced when the pressure angle is reduced, and the contact ratio increases when the helical angle is increased. Also, when the gear type is changed from spur gear to helical gear, transmission error is reduced and contact ratio is increased, which is the most advantageous for noise reduction. The actual sample was manufactured and evaluated in five combinations. The result of the evaluation confirmed that the sample with the reduced pressure angle was the best to reduce noise. It was expected that changing the gear type from spur to helical would be the most advantageous for noise reduction. However, if the shaft rigidity is not strong enough to support thrust which is occurred by gear type change, the load noise increased at the end of EPB operation. The gear optimization of EPB actuator showed the following: First, In the no-load section, it was found that noise reduction can be achieved by optimization of the main gear design factor. Second, in the load section, if the stiffness of the shaft is weak, the noise increases at the end of operation due to thrust. In the future, the EPB actuator will be designed using this gear optimization process to reduce the EPB operation noise.
{"title":"Gear Optimization for Noise Reduction of EPB Actuator","authors":"Sangbum Kim, I. Park, C. Park","doi":"10.46720/4016435eb2020-ebs-007","DOIUrl":"https://doi.org/10.46720/4016435eb2020-ebs-007","url":null,"abstract":"As the demand for passenger cars that are equipped with EPB(electric parking brake) system increases, the automotive parts companies have tried to develop the EPB on all vehicle. As the range of EPB application expands, customer demand for noise reduction during EPB operation also increases. In order to reduce the EPB operating noise, the optimum design of the EPB actuator two-step train gear was carried out. First of all, three gear design factors, such as pressure angle, helical angle, and gear type, were changed to verify the impact on EPB operation noise. As a result of this, the change of transmission error, contact ratio and specific speed were confirmed using KISSSOFT which is gear analysis program. Theoretically, the gear train which has small transmission error, large contact ratio, certain specific slide(-3~+3) is advantageous for noise reduction. As a result of the analysis, it was confirmed that the transmission error is reduced when the pressure angle is reduced, and the contact ratio increases when the helical angle is increased. Also, when the gear type is changed from spur gear to helical gear, transmission error is reduced and contact ratio is increased, which is the most advantageous for noise reduction. The actual sample was manufactured and evaluated in five combinations. The result of the evaluation confirmed that the sample with the reduced pressure angle was the best to reduce noise. It was expected that changing the gear type from spur to helical would be the most advantageous for noise reduction. However, if the shaft rigidity is not strong enough to support thrust which is occurred by gear type change, the load noise increased at the end of EPB operation. The gear optimization of EPB actuator showed the following: First, In the no-load section, it was found that noise reduction can be achieved by optimization of the main gear design factor. Second, in the load section, if the stiffness of the shaft is weak, the noise increases at the end of operation due to thrust. In the future, the EPB actuator will be designed using this gear optimization process to reduce the EPB operation noise.","PeriodicalId":254446,"journal":{"name":"EuroBrake 2020 Technical Programme","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123793188","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}
Pub Date : 2019-05-13DOI: 10.20944/PREPRINTS201905.0152.V1
P. Filip, S. Rhee
This contribution addresses dry sliding friction of a “Non-Asbestos Organic” friction material (pad) rubbed against a pearlitic grey cast iron disc. This configuration is commonly used in brakes in US, Europe and Asia. The initial stage of friction is of particular interest when addressing “creep-groan” phenomena occurring in passenger and sport utility vehicles with automatic transmissions. The custom-built Universal Friction Tester allowing the variation of sliding speed, test temperature, normal load, stiffness and humidity of the system was used in this experiment in combination with surface analysis by polarized light microscopy, scanning electron microscopy and stylus profilometry. The obtained results indicate that the “stick” phase in the so-called “stick-slip” phenomenon does not really exist. The surfaces of pad and disc are in continuous relative movement. The complexity of surfaces does not allow for a definitive description of exact mechanisms responsible for the detected changes of friction forces. The observed friction process can be rather described as a stretching with possible localized relaxations causing the jerky behavior in the stretching phase, followed by slip between two materials in contact. Understanding of factors contributing to the stretching at different scale levels of friction system is necessary for development of proper models. An accurate friction model should also incorporate the vibrational element introduced by phenomena occurring at the friction surfaces. The absence of heterogeneous regions on the friction surface and “evenly distributed friction level” can help when mitigating creep-groan in the investigated brake system. Understanding of factors on different scales of friction is also required when developing the improved brakes.
{"title":"Contribution to the Understanding of “Stick-Slip” Friction and Creep-Groan Phenomena in Automotive Brake Materials","authors":"P. Filip, S. Rhee","doi":"10.20944/PREPRINTS201905.0152.V1","DOIUrl":"https://doi.org/10.20944/PREPRINTS201905.0152.V1","url":null,"abstract":"This contribution addresses dry sliding friction of a “Non-Asbestos Organic” friction material (pad) rubbed against a pearlitic grey cast iron disc. This configuration is commonly used in brakes in US, Europe and Asia. The initial stage of friction is of particular interest when addressing “creep-groan” phenomena occurring in passenger and sport utility vehicles with automatic transmissions. The custom-built Universal Friction Tester allowing the variation of sliding speed, test temperature, normal load, stiffness and humidity of the system was used in this experiment in combination with surface analysis by polarized light microscopy, scanning electron microscopy and stylus profilometry. The obtained results indicate that the “stick” phase in the so-called “stick-slip” phenomenon does not really exist. The surfaces of pad and disc are in continuous relative movement. The complexity of surfaces does not allow for a definitive description of exact mechanisms responsible for the detected changes of friction forces. The observed friction process can be rather described as a stretching with possible localized relaxations causing the jerky behavior in the stretching phase, followed by slip between two materials in contact. Understanding of factors contributing to the stretching at different scale levels of friction system is necessary for development of proper models. An accurate friction model should also incorporate the vibrational element introduced by phenomena occurring at the friction surfaces. The absence of heterogeneous regions on the friction surface and “evenly distributed friction level” can help when mitigating creep-groan in the investigated brake system. Understanding of factors on different scales of friction is also required when developing the improved brakes.","PeriodicalId":254446,"journal":{"name":"EuroBrake 2020 Technical Programme","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117101404","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}
A. Pérez, B. Ferrer, J. Bruyninx, Fabio Squadrani, John O'leary, R. Delgado
{"title":"Brake Particles Emissions Characterization During Novel Real-world Driving Cycle","authors":"A. Pérez, B. Ferrer, J. Bruyninx, Fabio Squadrani, John O'leary, R. Delgado","doi":"10.46720/eb2020-ebs-014","DOIUrl":"https://doi.org/10.46720/eb2020-ebs-014","url":null,"abstract":"","PeriodicalId":254446,"journal":{"name":"EuroBrake 2020 Technical Programme","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134434556","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}
A. Belsak, J. Prezelj, Severin Huemer-Kals, K. Häsler
{"title":"Identification and Classification of Stick-Slip Nonlinear Phenomena on Complex Dynamic Systems","authors":"A. Belsak, J. Prezelj, Severin Huemer-Kals, K. Häsler","doi":"10.4672/EB2020-STP-056","DOIUrl":"https://doi.org/10.4672/EB2020-STP-056","url":null,"abstract":"","PeriodicalId":254446,"journal":{"name":"EuroBrake 2020 Technical Programme","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127302785","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 boundary layer dynamics are significantly responsible for the friction behavior of a tribo contact. A test bench to investigate the processes in the boundary layer was introduced in [1]. The so-called Wear Debris Investigator (WDI) of the Institute of Dynamics and Vibrations (IDS) forms a friction gap between a rotating and a fixed disc. For a measurement, artificial wear particles are added into the friction gap. The rotating disc of the friction contact consists of a transparent material. This allows the boundary layer to be observed in situ using a high-resolution camera. The obtained image data is used, i. a., to make statements about the formation and destruction processes of contact patches. With the measurement data of an implemented force and torque sensor, correlations between the boundary layer dynamics and the occurring friction forces can be made. This requires a high-precision measurement setup. A large number of measurements at the WDI revealed that precision and force measurement are not sufficient for all dynamic phenomena. For this reason, an innovative measuring system has been developed within the framework of this paper, which allows accurate statements to be made about the interactions of the third body with the first bodies. One major advantage of the new measuring device is that there are almost no drift effects observed during the measurement of the normal forces and friction moments. System-related normal force fluctuations are countered by a force adjustment with three adjustable elasticities, whereby the fluctuations are almost eliminated. This design allows to precisely adjust the normal forces in a wide range. Even measurements with smallest load ranges are provided by the innovative test design. First measurements using the new measuring device are presented in this paper.
{"title":"Test Device for Precise Investigations of Transport Phenomena in the Boundary Layer","authors":"G. Ostermeyer, Felix Rickhoff, Johannes L. Otto","doi":"10.46720/eb2020-stp-053","DOIUrl":"https://doi.org/10.46720/eb2020-stp-053","url":null,"abstract":"The boundary layer dynamics are significantly responsible for the friction behavior of a tribo contact. A test bench to investigate the processes in the boundary layer was introduced in [1]. The so-called Wear Debris Investigator (WDI) of the Institute of Dynamics and Vibrations (IDS) forms a friction gap between a rotating and a fixed disc. For a measurement, artificial wear particles are added into the friction gap. The rotating disc of the friction contact consists of a transparent material. This allows the boundary layer to be observed in situ using a high-resolution camera. The obtained image data is used, i. a., to make statements about the formation and destruction processes of contact patches. With the measurement data of an implemented force and torque sensor, correlations between the boundary layer dynamics and the occurring friction forces can be made. This requires a high-precision measurement setup. A large number of measurements at the WDI revealed that precision and force measurement are not sufficient for all dynamic phenomena. For this reason, an innovative measuring system has been developed within the framework of this paper, which allows accurate statements to be made about the interactions of the third body with the first bodies. One major advantage of the new measuring device is that there are almost no drift effects observed during the measurement of the normal forces and friction moments. System-related normal force fluctuations are countered by a force adjustment with three adjustable elasticities, whereby the fluctuations are almost eliminated. This design allows to precisely adjust the normal forces in a wide range. Even measurements with smallest load ranges are provided by the innovative test design. First measurements using the new measuring device are presented in this paper.","PeriodicalId":254446,"journal":{"name":"EuroBrake 2020 Technical Programme","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131256743","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}
Severin Huemer-Kals, Manuel Pürscher, Anton Sternat, P. Fischer
Creep groan is known as an important cause of warranty issues related to disk brake systems. Creep groan’s self-excited and stick-slip related mechanisms lead to strongly perceptible noise and vibrations. Due to creep groan’s nonlinear nature, resulting limit cycle vibrations are known to depend on the operating parameters present in experiment or simulation. So far, this dependency on parameters such as brake pressure and vehicle speed has only been investigated for strongly reduced systems. These reduced systems were often not able to cover all bifurcation phenomena found within vehicle tests. Vehicle tests are, however, more difficult to control, which complicates the detection of stability regions on the full system. In addition, little attention was paid to the startup of creep groan vibrations until now, as most studies focused on the analysis of fully developed creep groan signatures. This study tries to cover this knowledge gap; to discover and explain bifurcation behavior as well as the startup of creep groan vibrations. The investigated system was chosen big enough to show the main bifurcation effects but small enough to be easily controlled: Half-axle tests were performed on a drum-driven test bench. During the tests, creep groan limit cycles were approached for different brake pressures by increasing as well as decreasing speeds. The results give detailed insight in the highly-transient mechanisms of creep groan startup. Two different bifurcations, lowfrequency creep groan at approx. 21 Hz and high-frequency creep groan at approx. 75 Hz, were found. A certain ‘transition’ groan was found as a phenomenon between both stable groan regions. The direction of approach – increasing or decreasing speed – clearly led to different stability regions. Based on these findings, recommendations for future investigations can be derived: Simulative and experimental models should be able to perform both lowand high-frequency groan. Both increasing and decreasing speeds need to be considered in creep groan analysis as well. This can be crucial for the design of simulation models and test procedures in future.
{"title":"Startup and Bifurcation Behavior of Non-Linear Stick-Slip Vibrations: Creep Groan Occurrence for Increasing and Decreasing Speeds","authors":"Severin Huemer-Kals, Manuel Pürscher, Anton Sternat, P. Fischer","doi":"10.4672/EB2020-FBR-032","DOIUrl":"https://doi.org/10.4672/EB2020-FBR-032","url":null,"abstract":"Creep groan is known as an important cause of warranty issues related to disk brake systems. Creep groan’s self-excited and stick-slip related mechanisms lead to strongly perceptible noise and vibrations. Due to creep groan’s nonlinear nature, resulting limit cycle vibrations are known to depend on the operating parameters present in experiment or simulation. So far, this dependency on parameters such as brake pressure and vehicle speed has only been investigated for strongly reduced systems. These reduced systems were often not able to cover all bifurcation phenomena found within vehicle tests. Vehicle tests are, however, more difficult to control, which complicates the detection of stability regions on the full system. In addition, little attention was paid to the startup of creep groan vibrations until now, as most studies focused on the analysis of fully developed creep groan signatures. This study tries to cover this knowledge gap; to discover and explain bifurcation behavior as well as the startup of creep groan vibrations. The investigated system was chosen big enough to show the main bifurcation effects but small enough to be easily controlled: Half-axle tests were performed on a drum-driven test bench. During the tests, creep groan limit cycles were approached for different brake pressures by increasing as well as decreasing speeds. The results give detailed insight in the highly-transient mechanisms of creep groan startup. Two different bifurcations, lowfrequency creep groan at approx. 21 Hz and high-frequency creep groan at approx. 75 Hz, were found. A certain ‘transition’ groan was found as a phenomenon between both stable groan regions. The direction of approach – increasing or decreasing speed – clearly led to different stability regions. Based on these findings, recommendations for future investigations can be derived: Simulative and experimental models should be able to perform both lowand high-frequency groan. Both increasing and decreasing speeds need to be considered in creep groan analysis as well. This can be crucial for the design of simulation models and test procedures in future.","PeriodicalId":254446,"journal":{"name":"EuroBrake 2020 Technical Programme","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127698572","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}
Stick-Slip effects occur at the contact surface between the brake pads and the brake disc. The Creep Groan phenomenon is associated with stick-slip effects in the frequency range up to 500 Hz. It induces vibrations on the entire brake system and influences the structural vibrations of the vehicle. Vibrations are transmitted to large surfaces which produce audible noise. Creep Groan Noise is unpleasant and can be considered as a defect, especially for drivers of luxury cars. Harshness and annoyance caused by Creep Groan noise depends on many factors. For this reason, vehicle tests often include a subjective analysis of the Creep Groan Noise. Unfortunately, subjective tests suffer from the inherent uncertainties of subjective evaluation. A model for the assessment of Creep Groan noise harshness is necessary to reduce these uncertainties and to improve the Creep Groan assessment. For this purpose, experimental tests with over 1000 measurements were carried out. Many different features from the measurement data were extracted and analyzed. Selected features (quasi acoustic emission, simulated sound pressure level and vibration level) were used to classify Creep Groan into eight annoyance classes using Kohonen's Self Organizing Maps and a K-Means algorithm. The results of both unsupervised classification algorithms were correlated with a subjective quantification ranging from 1 (very poor) to 10 (excellent). After the right interpretation of the unsupervised algorithmic classification, performed with the K-Means algorithm, the correlation between the algorithmic classification and the subjective quantification of the creep groan harshness is obtained. It is shown that Kohonen's self-organizing map, in combination with selected features of vibroacoustic signals, provides readily usable results without any need for subjective evaluations.
{"title":"Objective and Subjective Classification of Creep Groan Noise","authors":"J. Prezelj, Severin Huemer-Kals, K. Häsler","doi":"10.4672/EB2020-STP-067","DOIUrl":"https://doi.org/10.4672/EB2020-STP-067","url":null,"abstract":"Stick-Slip effects occur at the contact surface between the brake pads and the brake disc. The Creep Groan phenomenon is associated with stick-slip effects in the frequency range up to 500 Hz. It induces vibrations on the entire brake system and influences the structural vibrations of the vehicle. Vibrations are transmitted to large surfaces which produce audible noise. Creep Groan Noise is unpleasant and can be considered as a defect, especially for drivers of luxury cars. Harshness and annoyance caused by Creep Groan noise depends on many factors. For this reason, vehicle tests often include a subjective analysis of the Creep Groan Noise. Unfortunately, subjective tests suffer from the inherent uncertainties of subjective evaluation. A model for the assessment of Creep Groan noise harshness is necessary to reduce these uncertainties and to improve the Creep Groan assessment. For this purpose, experimental tests with over 1000 measurements were carried out. Many different features from the measurement data were extracted and analyzed. Selected features (quasi acoustic emission, simulated sound pressure level and vibration level) were used to classify Creep Groan into eight annoyance classes using Kohonen's Self Organizing Maps and a K-Means algorithm. The results of both unsupervised classification algorithms were correlated with a subjective quantification ranging from 1 (very poor) to 10 (excellent). After the right interpretation of the unsupervised algorithmic classification, performed with the K-Means algorithm, the correlation between the algorithmic classification and the subjective quantification of the creep groan harshness is obtained. It is shown that Kohonen's self-organizing map, in combination with selected features of vibroacoustic signals, provides readily usable results without any need for subjective evaluations.","PeriodicalId":254446,"journal":{"name":"EuroBrake 2020 Technical Programme","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128664850","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}
Jonathan Schaible, Matthias Brucki, Luis Andrea Hau, Thomas Schopphoven, N. Pirch, J. Schleifenbaum
EHLA (Extreme High-speed Laser Material Deposition) is a process variant of LMD (Laser Material Deposition) that has been developed by Fraunhofer ILT and RWTH Aachen University. EHLA is characterized by the fact that the laser beam melts the powder particles above the melt pool, as opposed to conventional LMD where the particles melt only when they immerse into the melt pool. Due to this difference, EHLA processes can be set up with speeds of up to several hundred meters per minute. The changed process setup is achieved using specially designed coaxial powder nozzles and adapted process parameters. As previous work conducted at ILT has shown, EHLA allows to generate thin and uniform coatings on grey cast iron brake discs, which is desirable for different reasons, ranging from increased resistance to wear and corrosion to optical benefits and reduction of particulate emissions of vehicles. EHLA coatings as thin as 100 μm can be applied with high deposition rates (in this work up to 300 cm2/min). Compared to coatings produced by galvanic or thermal spray processes, EHLA layers exhibit a stronger metallurgical bonding to the grey cast iron substrate. In this work, a stainless steel powder material (316 L) is chosen to demonstrate the feasibility of coating grey cast iron brake discs. Process parameters based on previous experimental results are presented and compared for conventional LMD and EHLA. To underline the differences in process setup, a simulation of the two processes is performed and correlated with the experimental findings. The degree of transmission is calculated and compared as well as the temperature distribution in the substrate, focusing on the depth of the heat affected zone.
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