Sahil Naghate, Sandeep Patil / International Journal of Engineering Research and Applications                    (IJERA)  ...
Sahil Naghate, Sandeep Patil / International Journal of Engineering Research and Applications                    (IJERA)  ...
Sahil Naghate, Sandeep Patil / International Journal of Engineering Research and Applications                    (IJERA)  ...
Sahil Naghate, Sandeep Patil / International Journal of Engineering Research and Applications                    (IJERA)  ...
Sahil Naghate, Sandeep Patil / International Journal of Engineering Research and Applications                    (IJERA)  ...
Sahil Naghate, Sandeep Patil / International Journal of Engineering Research and Applications                    (IJERA)  ...
Sahil Naghate, Sandeep Patil / International Journal of Engineering Research and Applications                    (IJERA)  ...
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Lv2419731979

  1. 1. Sahil Naghate, Sandeep Patil / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1973-1979 Modal Analysis of Engine Mounting Bracket Using FEA Sahil Naghate*, Sandeep Patil** *Department of Mechanical Engineering, Marathwada Institute of Technology, Aurangabad, Maharashtra, India. ** Department of Mechanical Engineering, Marathwada Institute of Technology, Aurangabad, Maharashtra, India.Abstract The engine mounting plays an important Automobile engine-chassis-body system mayrole in reducing the noise, vibrations and undergo undesirable vibrations due to disturbancesharshness for improving vehicle ride comfort. from the road and the engine. The vibrations inducedThe first and the foremost function of an engine by the road or the engine at idle are typically at themounting bracket is to properly balance the frequencies below 30Hz. In order to control the idlepower pack (engine &transmission) on the vehicle shake and the road-induced vibrations, the enginechassis for good motion control as well as good mount bracket should be stiff and highly damped. Onisolation. the other hand, for a small amplitude excitation over the higher frequency range (30- 250Hz) from the Present work deals with FEA analysis of engine, a compliant and lightly damped mountengine mounting bracket. It includes the modeling bracket is required for vibration isolation andof the engine mounting brackets by changing the acoustic comfort. So, the engine mount bracket mustmaterial of component. Materials selected are satisfy these two essential criteriaAluminum alloy and magnesium alloy. Analysisincludes Static and Modal Analysis of engine In diesel engines the engine mounting is onemounting bracket using Square Cross section. The of the major problems. Due to the Un-throttledstudy shows that this bracket will have a dramatic condition, and higher compression ratio of the dieselweight reduction compare to standard aluminum engine, the speed irregularities particularly at lowalloy material and withstand high stress. Speed and Low load conditions and are significantly higher than gasoline engines. Thus this results inKeywords- Engine, Mounting, FEA, Modal vibration excitation. Due to vibration of engine theAnalysis. holes on the engine mounting Bracket get enlarged which results in the failure of bracket. By optimizing the thickness and shape of major mounting pointsI. INTRODUCTION made it possible to design a vehicle with optimized The need for light weight structural weight and performance at initial designing stagesmaterials in automotive applications is increasing as [1]. Studies shows that the brackets saved 38% massthe pressure for improvement in emissions and fuel (0.86 kg the expected and resultant benefit iseconomy increases. The most effective way of different for each application. Range of savings areincreasing automobile mileage while decreasing 20% to 38% in the authors’ experience to 0.53 kg)emissions is to reduce vehicle weight. The [4]. Structural optimization is an effective tool tomagnitude of the production volumes has obtain an optimum design. Comparison in terms oftraditionally placed severe requirements on the weight and component performance illustrates thatrobustness of the processes used in manufacturing. structural optimization techniques are effective toThe strong emphasis on the cost has demanded the produce higher quality products at a lower cost [5].component manufacturers to improve the Dynamic analysis of vehicle components and systemsperformance of their materials and to find the is now an integral part of the engineering designmethods to deliver these materials at reduced cost. process in the automotive industry [9]. The topologyThere are a number of noise and vibration sources based design is used in the conceptual design phasethat affect the vehicle body. The noise and vibration and then, the shape optimization is subsequentlyoccur because the power that is delivered through employed using initial optimal topology.bumpy roads, the engine, and suspension result in theresonance effect in a broad frequency band. The ride The objective is to do a modal analysis ofand noise characteristics of a vehicle are significantly the engine bracket to determine whether the currentaffected by vibration transferred to the body through design has a natural frequency which is lower thanthe chassis mounting points from the engine and the excitation frequency of the engine bracket, insuspension. It is known that body attachment which case the design will be considered safe. Oncestiffness is an important factor of idle noise and road safety of the design is established, and thennoise for NVH performance improvement. The optimization will be done material Optimization: The 1973 | P a g e
  2. 2. Sahil Naghate, Sandeep Patil / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1973-1979design will be tested for different materials, PRE PROCESSING:Aluminum and magnesium alloy, and suitability of The pre-processing of the engine mountingmaterial will be tested. bracket is down for the purpose of the dividing the problem into nodes and elements, developingII. METHODOLOGY equation for an element, applying boundaryBASIC STEPS IN THE FEA conditions, initial conditions and for applying loads. The basic steps involved in any finite The information required for the pre-processing stageelement analysis consist of the following of the bracket is as follows,  Material properties: The values of young’s PREPROCESSING PHASE modulus, poisons ratio, density, yield strength for Aluminium and magnesium are taken from material library of the FEA PACKAGE. At the point only one material is selected at a time, which SOLUTION PHASE is sufficient to show that a change of material is made depending upon the analysis results. Meshing: A solid element mesh is required to be POSTPROCESSING PHASE generated. The meshing of the mounting bracket is done as hex mesh for steel, for Aluminium and for magnesium also. Fig.1. FEA process  Loads: Specific values of load are implemented for a typical mounting bracket. The load is taken as 1000N which is considerable as the distributedSTATIC STRUCTURAL ANALYSIS weight of the engine is less than this value. Load is A static structural analysis is the analysis applied at the three holes of the engine mountingdisplacements, stresses, strains and forces on bracket, which are connected to the enginestructure or a component due to load application. The structure with the help of rigid elements such as nutstructures response and loads are assumed to vary and bolts.slowly with respect to time. There are various types  Constraints: The nodes around the bracketof loading that can be applied in this analysis which mounting holes have a rigid element connectingare externally applied forces and pressures, and them to the centre of the hole which has of itstemperatures. A static structural analysis can either degree of freedom fixed. The element which isbe linear or non linear. used to fix engine mounting bracket and body of the vehicle is fixed and used as a rigid element.MODAL ANALYSIS  The FE mesh together with the loads and Modal analysis determines the vibration constraints is made in the meshing environment.characteristics of a structure or a particular The minimum and maximum are set, together withcomponent in the form of natural frequencies and other mesh parameters such as element type andmode shapes. From this analysis we can do more material. The selected object is ready for furtherdetailed dynamic analysis such as transient dynamic analysis.analysis, harmonic analysis or spectrum analysis. Thenatural frequencies and mode shapes are important in POST PROCESSING:the design of a structure for dynamic loading The acceptability of the design of the engineconditions. In this analysis, only linear behavior is mounting bracket needs to be considered from thevalid. Damping is not considered and applied loads results of the analysis. The guidance for theare ignored in modal analysis. A static structural modification of the bracket need to be available if theanalysis is required first for performing pre stressed design is not considered to be acceptable for themodal analysis. engine mounting bracket are as follows. 1) Model acceptance criteria: the maximum von- The analysis of many engineering and Mises stress must be less than the material yieldautomotive components is done with the help of strength for the duration of the component. Thefinite element techniques. These analysis are very deflection is considered and the maximum Von-helpful for approving or making some design changes Mises stress must be less than the yield strength forduring the post processing stage. The design changes abuse load case.mainly depend on the product life cycle and helps 2) Design modification criteria: the modifications aredesign engineers or the analysts to finales dimensions made if the design is not acceptable, such asand material of the components. This analysis of an increasing fillet, increasing material thickness andengine mounting bracket is done with the help of altering material specifications. The output in theFEA software. form of the stress value is generated, when the analysis has been completed. This output data in the form of figures is then checked for determining 1974 | P a g e
  3. 3. Sahil Naghate, Sandeep Patil / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1973-1979 the relevant information and compared with the Young’s modulus – 7.1e+10 N/m2 acceptance criteria. Poisson’s ratio – 0.333) Result interpretation: from the results of the Density – 2770 Kg/m3 analysis the engineer required to understand the Yield strength in tension & compression – 2.8e+8 failure criteria for the particular component. N/m24) The Design Failure Criteria: maximum allowable deflection, maximum allowable stress is required to Stress analysis: be known and documented. For this purpose the Stress analysis of the engine mounting values of the Von-Mises stress is considered. There bracket is carried out by fixing the bracket at the is also a requirement for recognizing the effect of large size end which is fixed to the vehicle body. the analysis on the engine mounting bracket due to Then the load is applied at the other end of the load applied. bracket for the purpose of static structural analysis.ALUMINUM: Aluminum has only about one third thedensity of steel and the most commercial Aluminumalloys posses substantially higher specific strengththan steel. A vehicle weight reduction would not onlyresult in higher oil savings, but also gives asignificant reduction in emission. For these reasonsthere is preference to use more Aluminum andreplace steel in automotive applications. But there are several obstacles in implementation ofAluminum in automotive industry. Some of these are,  The forming limits of Aluminium are significantly lower than the steel. There are several chances of Aluminium to tearing at Fig 2: Meshed Model bends. This limits the shapes that can be fabricated and slows die design, die tryout and applications. Von-Mises stresses can be derived from the  Spring back problem is more in thicker sheets static analysis of structure. As shown in figure 3 the of Aluminium and it is hard to keep von mises stresses plots are taken. As seen from these dimensional tolerances. plots of stress we can see that maximum stress of the  Traditional vehicle body manufacturing value 26.758 MPa is found out at the bracket which is technology implementing stamped sheet steel fixing the bracket and the vehicle structure. This is component cannot be sufficiently improved to due to the load concentration at the fixed point. meet future vehicle requirements because of the higher weight of the steel and the high cost and more time required for stamping tool development. The analysis of the engine mounting bracketis done with the help of FEA PACKAGE software. Inthis process first the material selection done from theengineering data sheet of the FEA PACKAGEsoftware. Then the meshing of the component is donefrom the MESH function of the software. Theimportance of the meshing in the whole process ofanalysis is very important from the point of result Fig.3 Von-mises stress plot Fig 4: Deformation ofimplementation. The element used in the meshing is Bracketsolid 186 which are 20 node brick, hexagonal inshape and very good for the deformation problems. Above figure 4, shows the deformation ofThe size and shape of the meshing is the factor which the engine mounting bracket, when the load isspecifies the method of solution of FE problem in the applied at the side of bracket which is towards theany FEA software. By the process of refining, which engine connection. As seen from the deformation plotis nothing but the changing the size of the mesh deformation is more at the end of the bracket due toaccurate result can carry out. the maximum load application is at this side of theAluminum Alloy bracket. The deformation of this part is 1.6258 mm, Aluminum alloy under consideration has which can be seen from the above result. Thefollowing material properties: deformation plot shows the variation in values from 1975 | P a g e
  4. 4. Sahil Naghate, Sandeep Patil / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1973-1979fixed side to the engine side of bracket. It is conclude that the maximum value deformation isminimum at the fixed side and highest on the engine taking place at the bottom side of the bracketside. connected to the engine. The frequency of vibration for this particular mode is 322.78 Hz.MODAL ANALYSIS: The modal analysis of the engine mountingbracket is carried out for determining naturalfrequencies and shapes of the natural vibrationmodes. These frequencies are the outputs given bythe analysis of the engine mounting bracket. Fig 9: Fifth mode of vibration Fig 10: Sixth mode of vibration As seen from the above figure 9 the values of deformation increasing minimum to maximum from the end which is connected to the vehicle structure to the end of engine. The maximum value of Fig 5: First mode of vibration Fig 6: Second mode of deformation is seen at the ends of engine. The vibration frequency of vibration for this particular mode is 462.57 Hz. From the above plot (figure 10) of the From the above plot (figure 6) of the total total deformation of the engine mounting bracket wedeformation of the engine mounting bracket we can can conclude that the maximum value deformation isconclude that the maximum value deformation is taking place at the bottom side of the brackettaking place at the side of the bracket connected to connected to the engine. The frequency of vibrationthe engine. This is due to the fact that vibrations are for this particular mode of vibration is 630.5 Hz.going to act on this part of the bracket. Thedeformation for the other side which is fixed to the ALTERNATIVE MATERIAL “MAGNESIUMbody of the vehicle is almost zero for some part of it. ALLOY”The frequency of vibration for this particular mode of Magnesium is the lightest of all metals usedthe bracket is 142.78 Hz. as the basis for constructional alloys. It is this property due to which automobile manufactures has to replace denser materials, not only steels, cast irons and copper base alloys but even Aluminum alloys by magnesium base alloys. The requirement to reduce the weight of car components as a result in part of the introduction of legislation limiting emission has triggered renewed interest in magnesium. A wider use of magnesium base alloys necessitates several parallel programs. These can be classified as alloy development, process development improvement and Fig 7: Third mode of Fig 8: Fourth mode design considerations. The requirement to reduce the vibration of vibration weight of car components as a result in part of the introductions of legislation limiting emission has The third mode of vibration of the engine triggered renewed interest in magnesium.mounting bracket is seen in the plot (figure 7) formodal analysis. The part towards the engine of the The advantages of magnesium alloys arevehicle is not deformed too much, but from this point listed as follows, lowest density of all metallicto the side of the bracket which is fixed to the vehicle constructional materials. It posses high specificstructure is varying with deformation. The higher strength, good cast ability, which suitable for highvalue of deformation is at the upper corner of the pressure die casting good welding properties, higherbracket. The side towards the vehicle structure is corrosion resistance. Also compared with polymericlargely deformed as seen from the figure. The materials it posses better mechanical properties,frequency of vibration for this particular mode is better electrical and thermal conductivity and it is213.26 Hz. recyclable. The requirement to reduce the weight of From the above plot (figure 8) of the total car components as a result in part of the introductiondeformation of the engine mounting bracket we can of legislation limiting emission has triggered renewed 1976 | P a g e
  5. 5. Sahil Naghate, Sandeep Patil / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1973-1979interest in magnesium. The application of die cast the other side after some definite intervals. Themagnesium for automobile components produced in frequency of vibration for this particular mode of thelarge quantities is the one method for reducing bracket is 75.261 Hz.vehicle weight. But these components must be costcompetitive with material and processes in currentmanufacturing and gives high qualities to ensureadequate mechanical properties. One of the reasonsfor the limited use of magnesium has been some poorproperties exacerbated by a lack of developmentwork. It is not possible to use conventional alloyingtechniques to improve some of the properties, e.g.elastic constants. The solubility of alloying elementsin magnesium is limited, restricting the possibility of Fig 13: First mode of vibration Fig 14:Second mode ofimproving the mechanical properties and chemical vibrationbehavior. The crystal structure of magnesium ishexagonal which limited its inherent ductility. From the plot (figure 14) of the total deformation of the engine mounting bracket we canMagnesium Alloy conclude that the maximum value deformation isMagnesium alloy under consideration has following taking place at the side of the bracket connected tomaterial properties the engine. This is due to the fact that vibration is Young’s modulus – 4.5e+10 N/m2 going to act on this part of the bracket. The Poisson’s ratio – 0.35 deformation for the other side which is fixed to the Density – 1800 Kg/m3 body of the vehicle is almost zero for some part of it. Yield strength in tension and compression – The deformation goes on increasing from the fixed 1.93e+8 N/m2 end towards the side of the engine. The frequency of vibration for this particular mode of the bracket isStress Analysis 140.6 Hz. As shown in the figure 11) lot of the totaldeformation of the engine mounting bracket we canconclude that the maximum value deformation istaking place at the bracket connected to the engine.This is the fact that maximum load and vibrations aregoing to act on this part of the bracket. The highestvalue deformation takes place on this side which ishaving value of 2.5696 mm. the deformation for theother side which is fixed to the body of the vehicle, isalmost zero for some part of it. The deformation goes Fig 15: Third mode of Fig16: Fourth mode ofon increasing from the fixed end towards the side of vibration vibrationthe engine. The third mode of vibration of the engine mounting bracket is seen in the plot (fig 15) for modal analysis. The part towards the engine of the vehicle is not deformed too much, but from this point to the side of the bracket which is fixed to the vehicle structure is varying with deformation. The higher value of deformation is at the upper corner of the bracket. The side towards the vehicle structure is largely deformed as seen from the figure above. The frequency of vibration for this particular mode is Fig 11: Total deformation Fig 12: Stress distribution 210.62 Hz. From the above plot (figure 16) of the totalMODAL ANALYSIS: deformation of the engine mounting bracket we can It can be seen from the below plot of the conclude that the maximum value deformation isdeformation of the engine mounting bracket the taking place at the bottom side of the bracketdeformation is maximum at the end part which is connected to the engine. The frequency of vibrationconnected to the engine of the vehicle. The maximum for this particular mode is 318.52 Hz. As seen fromvalue of the deformation is less at the end which is the figure 17 the values of deformation increasingconnected to the vehicle, which can be said at a fixed minimum to maximum from the end which isone. The deformation increases from the fixed end to connected to the vehicle structure to the end of 1977 | P a g e
  6. 6. Sahil Naghate, Sandeep Patil / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1973-1979engine. The maximum value of deformation is seen at Table-3: Frequency comparison for Aluminum andthe of engine. The frequency of vibration for this magnesium Alloy’sparticular mode is 455.91 Hz. The need for lowweight materials in the vehicle is driving automobilemanufacturers to look to new material for use in theirproducts. Some studies suggest that 4.5 to 6% fuelefficiency can be gained for every10% reduction invehicle weight. The typical magnesium alloy castpart, is lighter compare to Aluminum or steel part.Comparison between steel, Aluminum’s andmagnesium can be done for the material of the enginemounting bracket as follows,RESULTS AND DISCUSSIONSTRESS ANALYSIS: Graph: Magnesium Alloy Graph: Aluminum Alloy Aluminum Magnesium alloy alloy From above graphs we can conclude that the Von-Mises 26.758 Mpa 26.483 Mpa convergence of a frequency for magnesium material stress(max) is good. The first excitation frequency value for Total 1.6258 mm 2.5696 mm magnesium is higher than that of excitation frequency deformation range of engine. (max) CONCLUSION Table 2: Stress Analysis for Engine Mounting Bracket The finite element analysis tool has been used to analyze the engine mounting bracket using It can be seen from the above results that the CAE Package. This work is a contribution to thevalue of the stress on the Aluminum bracket is not development of new material for engine mountingvarying too much than the stress value of magnesium bracket. The results obtained for the static structuralbracket for the same load. This is because of the fact and modal analysis have shown that the magnesiumthat the area and force for both brackets are same. is better than aluminum. From the results it can beThe values of the total deformation are varying in seen that the magnesium bracket is safe for thesome large values. This is due to difference in the required application.density of the materials. The main advantage of the magnesium engine mounting bracket is its light weight. It willMODAL ANALYSIS help in decreasing the weight of the power train The values of frequencies are nearly same assembly, which can increase fuel efficiency.for gray cast iron, Aluminum and magnesium Magnesium is recyclable; therefore it is an ecobracket. The first excitation frequency value for friendly material. The magnesium bracket can bemagnesium is higher than that of excitation frequency manufactured with less amount of time and it possesrange of engine (1-150 HZ). longer life compared to an aluminium bracket. The magnesium bracket is less susceptible to corrosion; Frequency Aluminum Magnesium therefore they are better for the application of alloy in Alloy in Hz bracket. The main problem of using magnesium Hz instead of aluminum is its higher cost; but recent First 76.121 75.108 studies have shown that the difference between costs Frequency of aluminium and magnesium is decreasing. Also if the use of magnesium in industries increases, its Second 142.78 140.6 manufacturing cost will be definitely reduced. Frequency Third 213.26 210.62 Thus it can be concluded that magnesium Frequency can be preferred over aluminum as a material for an Fourth 322.78 318.52 engine mounting bracket. Research in the direction of Frequency implementing magnesium engine mounting bracket Fifth 462.57 455.91 instead of aluminum bracket has also proved that Frequency magnesium brackets are better in various operating Sixth 630.5 622.94 conditions. Frequency 1978 | P a g e
  7. 7. Sahil Naghate, Sandeep Patil / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1973-1979REFERENCES [6] Guizhi Sun, Minxiang Wei, Jinju Shao and Man Pei, Automotive Powertrain Modeling [1] Kichang Kim and Inho Choi, Design and Simulation Based on AMESim, SAE Optimization Analysis, SAE TECHNICAL, TECHNICAL,PAPER SERIES, 2007-01- 2003-01-1604 3464. [2] Doo-Ho Lee, Jeon, Woo Chang, Chan-Mook [7] Doo-Ho Lee, Woo-Seok Hwang, Chan- Kim, Optimal Shape Design of an Air- Mook Kim, Noise Sensitivity Analysis of an Conditioner Compressor Mounting Bracket Engine Mount System using the Transfer in a Passenger Car, SAE TECHNICAL Function Synthesis Method, SAE PAPER SERIES, 2003-01-1667 TECHNICAL,PAPER SERIES, 2001-01- [3] Hong Suk Chang, A Study on the Analysis 1532. Method for Mounting Brackets, SAE [8] K.S. Raghavan, T. Howard, J. Buttles, TX TECHNICAL,PAPER SERIES, 2006-01- N. Law, Weight Reduction of Structural 1480 Vibration Isolation Hydro-Mount Bracket [4] Michael Champrenault and Clayton A. through Design Analysis and Use of Maas, Jack Cunningham, Magnesium Advanced High Strength Steels, SAE Powertrain Mount Brackets: New TECHNICAL,PAPER SERIES, 09M-0168. Application of Material Being usedin this [9] R SINGH, Dynamic design of automotive Sub-System for VehicleMass Reduction, systems: Engine mounts and structural SAE TECHNICALPAPER SERIES, 2007- joints, , Vol. 25, Part 3, June 2000, pp. 319- 01-1031 330 [5] Xiao-Yong Pan and Doni Zonni,Tuopu [10] H. Muhammad, Muhardi, W. Kuntjoro and Group,Guo-Zhong Chai, Yan-Qing Zhao B.E. Sritjahjono, In- flight thrust and Cui-Cui Jiang, Structural Optimization determination by load measurement on the for Engine Mount Bracket, SAE engin mounting system, ICAS 2000 TECHNICAL,PAPER SERIES, 2007-01- CONGRESS,2000. 2419. 1979 | P a g e

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