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Numerical and Experimental Modal Analysis of Car Roof Incorporating Viscoelastic Damper
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ScienceDirect Materials Today: Proceedings 5 (2018) 22254–22261
www.materialstoday.com/proceedings
ICASE_2017
Numerical and Experimental Modal Analysis of Car Roof Incorporating Viscoelastic Damper N.M. Bhaskar a, P. M. Sureshb, Satish Babuc, B. T. Chandruc* a
Department of Mech Engg, Bengaluru, India b ACS College of Engg., Bengaluru, India c Department of Mech Engg., EWIT, Bengaluru, India
Abstract Roof is one of the vital component in the passenger car, it not only provides safety against the outside obstacles which are disturbing driver and passengers and also it gives supports against the wind and also offers aerodynamic effects while in motion, roof will vibrate due to wind force and by the less strong or weak reinforcement, this can be overcome by adding some dampers. The present work deals with extraction of frequencies of car roof with viscoelastic damping conventional car roof by modelling using CATIA V5, meshed with meshing software Altair Hypermesh and analysed using ABACUS software. The experimental modal analysis, FEA analysis of the conventional viscoelastic car roof was carried out for free – free conditional to evaluate the natural frequencies. The results from EMA and FEA were agreeing with each other. It was found that the viscoelastic car roof revealed better NVH characteristics. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Science & Engineering ICASE - 2017. Keywords: Noise vibration, Harshness, EMA, FEM, Frequency, Roof, Viscoelastic damping.
1. Introduction Enhancing the riding experience and comfortness of the car has been taken as a very important parameter for passengers.
* Corresponding author. Tel: +91 9448170148 E-mail address: [email protected]
2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Science & Engineering ICASE - 2017.
N.M. Bhaskar.et.al., / Materials Today: Proceedings 5 (2018) 22254–22261
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Revamping is done by reducing or controlling Noise, Vibration and Harshness of the parts are concerned; noise produced due to vibration can be reduced by dampers. Roof functions as a protective component of a Automobile. Roof in automotive industry is usually made of metal and alloys. Roof is a very important part in achieving aerodynamics, better design of roof gives better resistance against air flow. Roof is of 4 variants, which are fully open type, closed type, sliding type and integrated with door. Conventional roof shows good resistance to NVH when it is incorporated with damping material – Viscoelastic damping. 2. Literature review Mahesh Suresh sabale et al [1]: in their work described regular increase of pressure on vehicle manufacture were urging towards reduction of vehicle emission. Thus lightweight strengthing solutions were required for roof strength. In their paper they have discussed about design of vehicle roof. So vehicle rollover was investigated the implementation of adequate material models. The benefits of those new materials were including reduced mass intern they got more efficiency. Thus they compared the performance of initial and new models and substantially they got vehicle with new material is able to secure and as well as met the required standards. Suresh PM et al [2] performed modal analysis of conventional and sandwich constructed passenger car roof. The Sandwich constructed car roof exhibited improved frequencies over the conventional one which will be helpful in combating NVH characteristics. Darshan k Thakur et al [3]: showed the plastic – hybrid composite technology was complimentary to metals and can be used for several kinds of applications. Their main intention was to combine stiffness, impact resistance and integration function to reduce the cost and lighter in weight. They confirmed that the use of plastic composite material as a means to reduce weight and improve the performance of automotive roof. The metals were used at where high stiffness and strength can be exploited, while the plastic composite gave better balance of stiffness and impact resistance. Overall, in their paper their main baseline was to found alternative. Manoranjan S N et al [4]: In their paper, main intention was to comment on the current trend and develop a new thing in the field of automotive roof using experimental modal analysis. To reduce the vibration in component they used FE and experimental modal analysis methods. Initially they generated CATIA model and analysed using HYPERWORKS software. The analysis was carried out in two ways without stiffener and with stiffener only for free - free condition. To compare the modal analysis result they did experimental analysis using original components. Overall they conclude that adding the stiffener reduced the noise and vibration. 3. Objectives and Methodology 3.1. Objectives
3-D model of the car roof is generated/modeled using CATIA V5 R20 software. Meshing the model by importing it into meshing software. Analyzing the result using HYPERVIEW software. Modifying the design and repeating the above procedure once again. Result comparison with 3experimental results.
3.2. Geometry The 3-D model of the car roof was modelled using a multiplatform CAD/ CAM/ CAE package is shown in the Fig. 1.
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Fig. 1. 3 – D model of car roof
3.3. Meshing Mesh generation is defined as approximation of geometry domain in the form of polygon. FEA contains tetrahedron, pyramids, prisms or hexahedron in 3D meshing (Fig. 2). HYPERMESH, a high performance FEM preprocessor was employed to generate the meshing of the roof
Fig. 2. Meshed model of car roof
N.M. Bhaskar.et.al., / Materials Today: Proceedings 5 (2018) 22254–22261
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3.4. Meshed parameters Table 1 shows the data of meshed parameter car roof Quality check parameters
Values
Minimum size
<1
Maximum size
> 10
Aspect ratio
>5
War page
> 15
Maximum angle quad
> 140
Minimum angle quad
< 40
Maximum angle tria
> 120
Minimum angle tria
< 30
Skew
> 40
Jacobian
< 0.6
Quality index
>1
3.5. Material and its properties Material and its properties play a vital role for the analysis of any component. Viscoelastic damper was incorporated to the car roof to study the NVH characteristics. The material property details of the viscoelastic dampers is tabulated in Table 2 Table 2. Material properties Item
D – 300 N (Unit)
Thickness
1.50 mm
Density
1.50 gm/cm3
90º peeling adhesion
102.37 N/25 mm
3.6. Numerical analysis without modification for free – free condition 7th mode shape of conventional car roof for free- free condition is shown in Fig. 3. Natural frequencies of the conventional car roof are tabulated in Table 3 Table 3. Natural frequency of Conventional car roof for free – free condition Mode shape
Frequency (in Hz)
7
47.980
8
86.528
9
114.49
10
125.29
11
143.71
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N.M. Bhaskar.et.al., / Materials Today: Proceedings 5 (2018) 22254–22261
Fig. 3. 7th mode shape of conventional car roof for free- free condition
3.7. Numerical analysis of car roof with viscoelastic damper for free – free condition Fig. 4 represents the 7th mode shape of car roof with viscoelastic damper for free- free condition. Natural frequencies of the car roof with viscoelastic damper are tabulated in Table 4
Fig. 4. 7th mode shape of car roof with viscoelastic damper for free- free condition
N.M. Bhaskar.et.al., / Materials Today: Proceedings 5 (2018) 22254–22261
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4. Experimental Modal Analysis Experimental analysis is used to validate the old results and we are only in the field of experimental that is only dynamic analysis. The vibration characteristics of analysis are natural frequency, damping and mode shapes, in our analysis we are using natural frequency and mode shapes after finish of analysis we are all three characteristics. The features of experimental analysis are: Interest in only load where acting with respect to time. Per second there will be 1000 sinusoidal waves are occurring. Interested to reduce the vibration or dynamics Table 4 Natural frequency of car roof for free – free condition Mode shape
Frequency (in Hz)
7
11.685
8
59.690
9
91.919
4.1. Experimental results of conventional car roof for free – free condition Figs. 5 and 6 show the 7th mode shape of car roof with viscoelastic damper for free- free condition. Natural frequencies of the conventional car roof is tabulated in Table 5 Table 5. Natural frequency of the car roof for free – free condition Mode shape
Frequency (in Hz)
7
53.9
8
91.1
9
109
10
120
11
131
Fig. 5. 7th mode shape shape of car roof with viscoelastic damper for free- free condition
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N.M. Bhaskar.et.al., / Materials Today: Proceedings 5 (2018) 22254–22261
4.2. Experimental results with car roof with viscoelastic damping for free – free condition A natural frequency of the car roof with viscoelastic damping is shown in Table 6 Table 6. Natural frequency for free – free condition Mode shape
Frequency (in Hz)
7
9.95
8
54.1
9
89.2
Fig. 6. 7th mode shape shape of car roof with viscoelastic damper for free- free condition
4.3. Comparison of Finite Elemental Analysis and Experimental Modal analysis for Conventional Car roof The results of Finite Elemental Analysis and Experimental Modal analysis of conventional car roof match each other as shown in Table 7 Table 7. Comparison of FEM and EMA of conventional Car roof Finite Elemental Analysis
Experimental Modal Analysis
Mode shape
Frequency (in Hz)
Mode shape
Frequency (in Hz)
7
47.980
7
53.9
8
86.528
8
91.1
9
114.49
9
109
4.4. Comparison of Finite Elemental Analysis and Experimental Modal analysis for Car roof with visco elastic damping The results of Finite Elemental Analysis and Experimental Modal analysis of car roof with viscoelastic damping match each other as shown in table 8
N.M. Bhaskar.et.al., / Materials Today: Proceedings 5 (2018) 22254–22261
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Table 8. Comparison of FEM and EMA of Car roof with visco elastic damping Finite Elemental Analysis
Experimental Modal Analysis
Mode shape
Frequency (in Hz)
Mode shape
Frequency (in Hz)
7
11.685
7
9.95
8
59.690
8
54.1
9
91.919
9
89.2
4.5. Comparison of Finite Elemental Analysis and Experimental Modal analysis for Conventional Car roof and car roof with visco elastic damping The results of Finite Elemental Analysis and Experimental Modal analysis of Conventional car roof and car roof with viscoelastic damping match each other as shown in table 9 Table 9. Comparison of FEM and EMA of conventional Car roof and car roof with viscoelastic damping Experimental Modal Analysis
Finite Elemental Analysis Conventional Car roof
Car roof with Viscoelastic damper
Conventional Car roof
Car roof with Viscoelastic damper
Mode shape
Frequency (in Hz)
Mode shape
Frequency (in Hz)
Mode shape
Frequency (in Hz)
Mode shape
Frequency (in Hz)
7
47.980
7
11.685
7
11.685
7
53.9
8
86.528
8
59.690
8
59.690
8
91.1
9
114.49
9
91.919
9
91.919
9
109
5. Conclusion The analysis and improvement of a vehicle body structure based on NVH behaviour is investigated by fem or numerical method. Firstly, the surface modelling is accomplished for the vehicle body in CATIA and meshed in HYPERMESH software. Then the FE Method is analyzed through free - free mode shapes and experimental modal analysis also done in free - free mode. From the two conditions without viscoelastic damper and with viscoelastic the frequency values obtained from the FE method and Experimental method are compared due to increase in the frequency values the vibration of the component decreases. And also due to decrease in the vibration automatically the noise of the component also decreases. By Finite elemental analysis and experimental analysis we can understand that the car roof with visco elastic damper provides better NVH results. References [1] Mahesh Suresh Sabale, N. Vivekanandan, Swap nil S. Kulkarni, Sabale, “Design of an automotive roof for cabin using plastic composite material as an effective alternative”, International Journal of Advanced Engineering Research and Studies EISSN2249–8974. [2] Suresh PM.Modal analysis of conventional and sandwich constructed Passanger car roof –International journal of applied engineering research ISSN 0973-4562 volume x, number x (2011) [3] Darshan. K.. Thakur, Prof. Devendra Sadaphale, Swapnil Kulkarni.Design through FEA for plastic composite material for suitability to automotive roof with compliance to ‘roof crush’ regulations- International journal of advanced engineering research and studies E-ISSN 2249-8974. [4] Manoranjan S N, Dr. Maruthi B H, Chandru B T, Mohan Kumar G R, “Noise vibration control of a roof of a car”, International Journal for Technological Research in Engineering, Volume 2, Issue 11, July-2015 ISSN (Online): 2347 – 4718
ScienceDirect Materials Today: Proceedings 5 (2018) 22254–22261
www.materialstoday.com/proceedings
ICASE_2017
Numerical and Experimental Modal Analysis of Car Roof Incorporating Viscoelastic Damper N.M. Bhaskar a, P. M. Sureshb, Satish Babuc, B. T. Chandruc* a
Department of Mech Engg, Bengaluru, India b ACS College of Engg., Bengaluru, India c Department of Mech Engg., EWIT, Bengaluru, India
Abstract Roof is one of the vital component in the passenger car, it not only provides safety against the outside obstacles which are disturbing driver and passengers and also it gives supports against the wind and also offers aerodynamic effects while in motion, roof will vibrate due to wind force and by the less strong or weak reinforcement, this can be overcome by adding some dampers. The present work deals with extraction of frequencies of car roof with viscoelastic damping conventional car roof by modelling using CATIA V5, meshed with meshing software Altair Hypermesh and analysed using ABACUS software. The experimental modal analysis, FEA analysis of the conventional viscoelastic car roof was carried out for free – free conditional to evaluate the natural frequencies. The results from EMA and FEA were agreeing with each other. It was found that the viscoelastic car roof revealed better NVH characteristics. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Science & Engineering ICASE - 2017. Keywords: Noise vibration, Harshness, EMA, FEM, Frequency, Roof, Viscoelastic damping.
1. Introduction Enhancing the riding experience and comfortness of the car has been taken as a very important parameter for passengers.
* Corresponding author. Tel: +91 9448170148 E-mail address: [email protected]
2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Advances in Science & Engineering ICASE - 2017.
N.M. Bhaskar.et.al., / Materials Today: Proceedings 5 (2018) 22254–22261
22255
Revamping is done by reducing or controlling Noise, Vibration and Harshness of the parts are concerned; noise produced due to vibration can be reduced by dampers. Roof functions as a protective component of a Automobile. Roof in automotive industry is usually made of metal and alloys. Roof is a very important part in achieving aerodynamics, better design of roof gives better resistance against air flow. Roof is of 4 variants, which are fully open type, closed type, sliding type and integrated with door. Conventional roof shows good resistance to NVH when it is incorporated with damping material – Viscoelastic damping. 2. Literature review Mahesh Suresh sabale et al [1]: in their work described regular increase of pressure on vehicle manufacture were urging towards reduction of vehicle emission. Thus lightweight strengthing solutions were required for roof strength. In their paper they have discussed about design of vehicle roof. So vehicle rollover was investigated the implementation of adequate material models. The benefits of those new materials were including reduced mass intern they got more efficiency. Thus they compared the performance of initial and new models and substantially they got vehicle with new material is able to secure and as well as met the required standards. Suresh PM et al [2] performed modal analysis of conventional and sandwich constructed passenger car roof. The Sandwich constructed car roof exhibited improved frequencies over the conventional one which will be helpful in combating NVH characteristics. Darshan k Thakur et al [3]: showed the plastic – hybrid composite technology was complimentary to metals and can be used for several kinds of applications. Their main intention was to combine stiffness, impact resistance and integration function to reduce the cost and lighter in weight. They confirmed that the use of plastic composite material as a means to reduce weight and improve the performance of automotive roof. The metals were used at where high stiffness and strength can be exploited, while the plastic composite gave better balance of stiffness and impact resistance. Overall, in their paper their main baseline was to found alternative. Manoranjan S N et al [4]: In their paper, main intention was to comment on the current trend and develop a new thing in the field of automotive roof using experimental modal analysis. To reduce the vibration in component they used FE and experimental modal analysis methods. Initially they generated CATIA model and analysed using HYPERWORKS software. The analysis was carried out in two ways without stiffener and with stiffener only for free - free condition. To compare the modal analysis result they did experimental analysis using original components. Overall they conclude that adding the stiffener reduced the noise and vibration. 3. Objectives and Methodology 3.1. Objectives
3-D model of the car roof is generated/modeled using CATIA V5 R20 software. Meshing the model by importing it into meshing software. Analyzing the result using HYPERVIEW software. Modifying the design and repeating the above procedure once again. Result comparison with 3experimental results.
3.2. Geometry The 3-D model of the car roof was modelled using a multiplatform CAD/ CAM/ CAE package is shown in the Fig. 1.
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Fig. 1. 3 – D model of car roof
3.3. Meshing Mesh generation is defined as approximation of geometry domain in the form of polygon. FEA contains tetrahedron, pyramids, prisms or hexahedron in 3D meshing (Fig. 2). HYPERMESH, a high performance FEM preprocessor was employed to generate the meshing of the roof
Fig. 2. Meshed model of car roof
N.M. Bhaskar.et.al., / Materials Today: Proceedings 5 (2018) 22254–22261
22257
3.4. Meshed parameters Table 1 shows the data of meshed parameter car roof Quality check parameters
Values
Minimum size
<1
Maximum size
> 10
Aspect ratio
>5
War page
> 15
Maximum angle quad
> 140
Minimum angle quad
< 40
Maximum angle tria
> 120
Minimum angle tria
< 30
Skew
> 40
Jacobian
< 0.6
Quality index
>1
3.5. Material and its properties Material and its properties play a vital role for the analysis of any component. Viscoelastic damper was incorporated to the car roof to study the NVH characteristics. The material property details of the viscoelastic dampers is tabulated in Table 2 Table 2. Material properties Item
D – 300 N (Unit)
Thickness
1.50 mm
Density
1.50 gm/cm3
90º peeling adhesion
102.37 N/25 mm
3.6. Numerical analysis without modification for free – free condition 7th mode shape of conventional car roof for free- free condition is shown in Fig. 3. Natural frequencies of the conventional car roof are tabulated in Table 3 Table 3. Natural frequency of Conventional car roof for free – free condition Mode shape
Frequency (in Hz)
7
47.980
8
86.528
9
114.49
10
125.29
11
143.71
22258
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Fig. 3. 7th mode shape of conventional car roof for free- free condition
3.7. Numerical analysis of car roof with viscoelastic damper for free – free condition Fig. 4 represents the 7th mode shape of car roof with viscoelastic damper for free- free condition. Natural frequencies of the car roof with viscoelastic damper are tabulated in Table 4
Fig. 4. 7th mode shape of car roof with viscoelastic damper for free- free condition
N.M. Bhaskar.et.al., / Materials Today: Proceedings 5 (2018) 22254–22261
22259
4. Experimental Modal Analysis Experimental analysis is used to validate the old results and we are only in the field of experimental that is only dynamic analysis. The vibration characteristics of analysis are natural frequency, damping and mode shapes, in our analysis we are using natural frequency and mode shapes after finish of analysis we are all three characteristics. The features of experimental analysis are: Interest in only load where acting with respect to time. Per second there will be 1000 sinusoidal waves are occurring. Interested to reduce the vibration or dynamics Table 4 Natural frequency of car roof for free – free condition Mode shape
Frequency (in Hz)
7
11.685
8
59.690
9
91.919
4.1. Experimental results of conventional car roof for free – free condition Figs. 5 and 6 show the 7th mode shape of car roof with viscoelastic damper for free- free condition. Natural frequencies of the conventional car roof is tabulated in Table 5 Table 5. Natural frequency of the car roof for free – free condition Mode shape
Frequency (in Hz)
7
53.9
8
91.1
9
109
10
120
11
131
Fig. 5. 7th mode shape shape of car roof with viscoelastic damper for free- free condition
22260
N.M. Bhaskar.et.al., / Materials Today: Proceedings 5 (2018) 22254–22261
4.2. Experimental results with car roof with viscoelastic damping for free – free condition A natural frequency of the car roof with viscoelastic damping is shown in Table 6 Table 6. Natural frequency for free – free condition Mode shape
Frequency (in Hz)
7
9.95
8
54.1
9
89.2
Fig. 6. 7th mode shape shape of car roof with viscoelastic damper for free- free condition
4.3. Comparison of Finite Elemental Analysis and Experimental Modal analysis for Conventional Car roof The results of Finite Elemental Analysis and Experimental Modal analysis of conventional car roof match each other as shown in Table 7 Table 7. Comparison of FEM and EMA of conventional Car roof Finite Elemental Analysis
Experimental Modal Analysis
Mode shape
Frequency (in Hz)
Mode shape
Frequency (in Hz)
7
47.980
7
53.9
8
86.528
8
91.1
9
114.49
9
109
4.4. Comparison of Finite Elemental Analysis and Experimental Modal analysis for Car roof with visco elastic damping The results of Finite Elemental Analysis and Experimental Modal analysis of car roof with viscoelastic damping match each other as shown in table 8
N.M. Bhaskar.et.al., / Materials Today: Proceedings 5 (2018) 22254–22261
22261
Table 8. Comparison of FEM and EMA of Car roof with visco elastic damping Finite Elemental Analysis
Experimental Modal Analysis
Mode shape
Frequency (in Hz)
Mode shape
Frequency (in Hz)
7
11.685
7
9.95
8
59.690
8
54.1
9
91.919
9
89.2
4.5. Comparison of Finite Elemental Analysis and Experimental Modal analysis for Conventional Car roof and car roof with visco elastic damping The results of Finite Elemental Analysis and Experimental Modal analysis of Conventional car roof and car roof with viscoelastic damping match each other as shown in table 9 Table 9. Comparison of FEM and EMA of conventional Car roof and car roof with viscoelastic damping Experimental Modal Analysis
Finite Elemental Analysis Conventional Car roof
Car roof with Viscoelastic damper
Conventional Car roof
Car roof with Viscoelastic damper
Mode shape
Frequency (in Hz)
Mode shape
Frequency (in Hz)
Mode shape
Frequency (in Hz)
Mode shape
Frequency (in Hz)
7
47.980
7
11.685
7
11.685
7
53.9
8
86.528
8
59.690
8
59.690
8
91.1
9
114.49
9
91.919
9
91.919
9
109
5. Conclusion The analysis and improvement of a vehicle body structure based on NVH behaviour is investigated by fem or numerical method. Firstly, the surface modelling is accomplished for the vehicle body in CATIA and meshed in HYPERMESH software. Then the FE Method is analyzed through free - free mode shapes and experimental modal analysis also done in free - free mode. From the two conditions without viscoelastic damper and with viscoelastic the frequency values obtained from the FE method and Experimental method are compared due to increase in the frequency values the vibration of the component decreases. And also due to decrease in the vibration automatically the noise of the component also decreases. By Finite elemental analysis and experimental analysis we can understand that the car roof with visco elastic damper provides better NVH results. References [1] Mahesh Suresh Sabale, N. Vivekanandan, Swap nil S. Kulkarni, Sabale, “Design of an automotive roof for cabin using plastic composite material as an effective alternative”, International Journal of Advanced Engineering Research and Studies EISSN2249–8974. [2] Suresh PM.Modal analysis of conventional and sandwich constructed Passanger car roof –International journal of applied engineering research ISSN 0973-4562 volume x, number x (2011) [3] Darshan. K.. Thakur, Prof. Devendra Sadaphale, Swapnil Kulkarni.Design through FEA for plastic composite material for suitability to automotive roof with compliance to ‘roof crush’ regulations- International journal of advanced engineering research and studies E-ISSN 2249-8974. [4] Manoranjan S N, Dr. Maruthi B H, Chandru B T, Mohan Kumar G R, “Noise vibration control of a roof of a car”, International Journal for Technological Research in Engineering, Volume 2, Issue 11, July-2015 ISSN (Online): 2347 – 4718