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Joint Interface Effects on Machining System Vibration
KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Machine and Process Technology.
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Vibration problems are still the major constraint in modern machining processes that seek higher material removal rate, shorter process time, longer tool life and better product quality. Depending on the process, the weaker structure element can be the tool/tool holder, workpiece/fixture or both. When the tool/tool holder is the main source of vibration, the stability limit is determined in most cases by the ratio of length-to-diameter. Regenerative chatter is the most significant dynamic phenomenon generated through the interaction between machine tool and machining process. As a rule of thumb, the ratio between the tool’s overhang length and the tool’s diameter shouldn’t exceed 4 to maintain a stable machining process while using a conventional machining tool. While a longer tool overhang is needed for specific machining operations, vibration damping solutions are required to ensure a stable machining process. Vibration damping solutions include both active and passive damping solutions. In the passive damping solutions, damping medium such as viscoelastic material is used to transform the vibration strain energy into heat and thereby reduce vibration amplitude. For a typical cantilever tool, the highest oscillation displacement is near the anti-node regions of a vibration mode and the highest oscillation strain energy is concentrated at the node of a vibration mode. Viscoelastic materials have been successfully applied in these regions to exhibit their damping property. The node region of the 1st bending mode is at the joint interfaces where the cantilever tools are clamped. In this thesis, the general method that can be used to measure and characterize the joint interface stiffness and damping properties is developed and improved, joint interfaces’ importance at optimizing the dynamic stiffness of the joint interface is studied, and a novel advancing material that is designed to possess both high young’s modulus and high damping property is introduced. In the joint interface characterization model, a method that can measure the joint interface’s stiffness and damping over the full frequency range with only the assembled structure is presented. With the influence of a joint interface’s normal pressure on its stiffness and damping, an optimized joint interface normal pressure is selected for delivering a stable machining process against chatter with a boring bar setting at 6.5 times overhang length to diameter ratio in an internal turning process. The novel advancing material utilizes the carbon nano particles mixed in a metal matrix, and it can deliver both high damping property and high elastic stiffness to the mechanical structure.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , ix, 48 p.
Series
TRITA-IIP, ISSN 1650-1888 ; 13:05
Keyword [en]
Joint Interface, Vibration, Damping, Chatter, Machining, Carbon NanoComposite, PECVD, HiPIMS
National Category
Engineering and Technology
Research subject
SRA - Production; Järnvägsgruppen - Ljud och vibrationer
Identifiers
URN: urn:nbn:se:kth:diva-122392ISBN: 978-91-7501-778-5 (print)OAI: oai:DiVA.org:kth-122392DiVA: diva2:622118
Presentation
2013-05-24, Sal M311, Brinellvägen 68, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
PoPJIM, HydroMod, XPRES, NanoComfort
Funder
EU, FP7, Seventh Framework Programme, G62241EU, FP7, Seventh Framework Programme, G62240XPRES - Initiative for excellence in production researchEU, European Research Council, E4329
Note

QC 20130521

Available from: 2013-05-21 Created: 2013-05-20 Last updated: 2015-11-11Bibliographically approved
List of papers
1. Joint interface characterization method using frequency response measurements on assembled structures only: theoretical development and experimental validation on a workholding fixture for machining
Open this publication in new window or tab >>Joint interface characterization method using frequency response measurements on assembled structures only: theoretical development and experimental validation on a workholding fixture for machining
2015 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 77, no 5-8, 1213-1228 p.Article in journal (Refereed) Published
Abstract [en]

A computation model based on inverse receptance coupling method is presented in this paper aiming for obtaining the joint interface's stiffness and damping properties using frequency response functions measured on assembled structures only. In the model, it is emphasized that the joint stiffness and damping should be modeled with frequency dependency. The model's validity is checked both through finite element (FE) simulation and experimental analyses. In the FE simulation example, the computation model gives more accurate results with noise-free data. In the experimental example, where noise in the data is unavoidable, the computation model is explored further for its applicability in the real industrial environment. Results from applications of the computational model show that it is even capable of obtaining the joint interface stiffness and damping values over the structure's resonance frequency. A viable process of predicting behaviors of workpiece with receptance coupling method through identifying the joint interface properties is presented in the end of the paper. The applicability of this computation model and the factors that influence the accuracy of the model are discussed in the end of the paper.

Keyword
Joint interface, Joint stiffness, Joint damping, Frequency response functions, Receptance coupling method, Inverse receptance coupling method, Finite element method
National Category
Production Engineering, Human Work Science and Ergonomics
Research subject
Production Engineering; Machine Design
Identifiers
urn:nbn:se:kth:diva-163992 (URN)10.1007/s00170-014-6539-3 (DOI)000350120000036 ()2-s2.0-84925467019 (Scopus ID)
Funder
EU, FP7, Seventh Framework Programme, 260048
Note

QC 20150427

Available from: 2015-04-27 Created: 2015-04-13 Last updated: 2017-12-04Bibliographically approved
2. Improving machining performance against regenerative tool chatter through adaptive normal pressure at the tool clamping interface
Open this publication in new window or tab >>Improving machining performance against regenerative tool chatter through adaptive normal pressure at the tool clamping interface
2013 (English)In: Journal of Machine Engineering, ISSN 1895-7595, Vol. 13, no 1, 93-105 p.Article in journal (Refereed) Published
Abstract [en]

Chatter in machining process is one of the common failures of a production line. For a cantilever tool, such as a boring bar, the rule of thumb requires the overhang length of the tool to be less than 4 times the diameter. The reason is because longer overhang will induce severe tool vibration in the form of chatter during machining. When a longer overhang than 4 times diameter is necessary for performing special machining operations, damping methods are needed to suppress tool chatter. One of the methods is the constrained layer damping method. Materials, such viscoelastic material, are applied in the vibration node regions of the structure to absorb the concentrated vibration strain energy and transform the mechanical energy to heat. With a cantilever tool clamped in a tool holder, the clamping interface is usually the vibration node region. The friction in the joint interface with low normal pressure became another source of damping and can be used for tool chatter suppression in mechanical structures. Joint interfaces are well known to possess normal pressure dependent stiffness and damping. The normal pressure’s effect on the structures frequency response function had been observed by H. Åkesson [1] et al, and L.Mi [2] et al. However, the direct effect of the joint interface normal pressure on machining process stability hasn’t been investigated. In this paper, a cantilever tool with 6.5 overhang length to diameter ratio is investigated. The direct effect of the tool clamping interface’s normal pressure on the machining process stability is studied. Three different levels of clamping normal pressure are tested with an internal turning process. The machining results indicate another adaptable solution on shop floor for suppressing tool chatter.

Place, publisher, year, edition, pages
Poland: , 2013
Keyword
chatter, tool, internal turning, vibration, clamping, damping, interface
National Category
Production Engineering, Human Work Science and Ergonomics
Research subject
Järnvägsgruppen - Ljud och vibrationer; SRA - Production
Identifiers
urn:nbn:se:kth:diva-122424 (URN)
Projects
POPJIMXPRES
Funder
XPRES - Initiative for excellence in production researchEU, FP7, Seventh Framework Programme, FoF.NMP.2010-1
Note

QC 20130521

Available from: 2013-05-21 Created: 2013-05-21 Last updated: 2015-11-11Bibliographically approved
3. Anti-vibration Engineering in Internal Turning Using a Carbon Nanocomposite Damping Coating Produced by PECVD Process
Open this publication in new window or tab >>Anti-vibration Engineering in Internal Turning Using a Carbon Nanocomposite Damping Coating Produced by PECVD Process
2014 (English)In: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, Vol. 23, no 2, 506-517 p.Article in journal (Refereed) Published
Abstract [en]

Machining dynamic stability has been enhanced through a damping coating based on a novel carbon-based nanocomposite material. The coating was synthesized using a plasma enhanced chemical vapor deposition method, and deposited on to the round-shank boring bar used for internal turning and tested during machining. Comparisons between an uncoated and a coated boring bar were carried out at 0.25 mm and 0.5 mm depth of cut using a five times length to diameter ratio overhang, which are typical conditions known to generate detrimental mechanical vibrations. From sound pressure measurement it was found that the measured absolute sound level during process could be reduced by about 90% when using the tool coated with damping layer. Surface roughness measurements of the processed workpiece showed decreased Ra values from approximately 3-6 mu m to less than 2 mu m (and in 50% of the cases < 1 mu m) when comparing an uncoated standard tool with its coated counterpart. Moreover, it was found that the addition of an anti-vibration coating did not adversely affect other tool properties, such as rigidity and modularity.

Place, publisher, year, edition, pages
Springer-Verlag New York, 2014
Keyword
chatter, machining, vibration damping, coating, PECVD, HIPIMS, metal matrix composite, carbon nanocomposite
National Category
Applied Mechanics Production Engineering, Human Work Science and Ergonomics Composite Science and Engineering Fluid Mechanics and Acoustics Nano Technology Fusion, Plasma and Space Physics
Research subject
Järnvägsgruppen - Ljud och vibrationer; SRA - Production
Identifiers
urn:nbn:se:kth:diva-122425 (URN)10.1007/s11665-013-0781-y (DOI)000330594800019 ()2-s2.0-84893576587 (Scopus ID)
Projects
Eurostars Nanocomfort E!4329, Vinnova
Funder
Vinnova, E!4329XPRES - Initiative for excellence in production research
Note

QC 20140228. Updated from submitted to published.

Available from: 2013-05-21 Created: 2013-05-21 Last updated: 2017-12-06Bibliographically approved

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