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30120140505018 2-3-4 30120140505018 2-3-4 Document Transcript

  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 170-179 © IAEME 170 NORMAL MODE ANALYSIS OF CYLINDER HEAD COVER Shahim Haider Abidi1 , Deo Raj Tiwari2 1 Dept. of Mechanical Engg. ZHCET, Aligarh Muslim University, India 2 Dept. of Mechanical and Automobile Engg., Sharda University, Greater Noida, India ABSTRACT Vibration in IC engines is a significant factor to be considered while designing IC engine as it can have a negative impact on various engine components. This happens when the natural frequency of component coincides with the forced frequency produce by the engine leading to the phenomenon of resonance. One of the part which can be effected is the cylinder head cover, if due consideration is not taken in the designing of the CHC, it might lead to the failure of component. If the CHC fails their might be leakage of engine oil due to which there is possibility of catastrophic accident hence it becomes important to design the CHC properly and this paper is based on evaluating the natural frequency of an Aluminum CHC through the FEM analysis. This paper is based on the work that CHC model is imported to HYPER-WORKS 9.0 to generate a high quality of mesh. Finally the mesh model is ready for analysis using Optistrut. The result obtained are analyzed and further modifications are recommended for optimization of model. Finite Element analysis results for safe Cylinder Head Cover model which is prone to failure due to resonance condition. Keyword: Cylinder Head Cover, FEM Analysis, Hyper-Works 9.0, Optistrut, Natural Frequency. I. INTRODUCTION The use of FEM has also been substantial in development of many theories and and analysis of various models in automobile sector. Initially Prashant D Parikh [1] in 1977 did work on “Finite element analysis of the static and dynamic behavior of automobile tyre”, He used a mathematical model to represent a radial ply passenger car tire for axisymmetric and asymmetric static and dynamic eigenvalue analysis by the use of a direct stiffness finite element method. . The finite element chosen had a shape of a conical frustum with five degrees of freedom at each node in the INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 5, Issue 5, May (2014), pp. 170-179 © IAEME: www.iaeme.com/ijmet.asp Journal Impact Factor (2014): 7.5377 (Calculated by GISI) www.jifactor.com IJMET © I A E M E
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 170-179 © IAEME 171 local coordinate system of the element. The tire properties were derived by assuming the tire to be composed of thin layers of composite materials, linearly orthotropic in nature. Hamilton's principle has been applied to derive the equation of motion of the element. In 1992 work on “A consistent Vlasov Model for analysis of plates on elastic foundations using Finite Element Method” was completed successfully by Wai Hung ho[2]. A one dimensional periodic Vlasov-Poisson equation with various approximations was considered. This included the particle-in-cell method, the upstream-downstream method (a finite element method) and the Lax-Wendroff method (a finite- difference method).ThyssenKrupp Tallent[3], a chassis structural and suspension products developer for the automotive industry, has gone through the HyperWorks CAE platform from Altair Engineering as an enterprise simulation system for design, optimization and virtual manufacturing of its automotive chassis components. The result of this co-operation is ThyssenKrupp's system, which, when combined with HyperWorks, has allowed ThyssenKrupp Tallent to increase productivity and deliver lighter products to their clients in shorter timescales. ABstructures[4] has been using the HyperWorks suite since its foundation in 2008. The company initially employed OptiStruct, from the HyperWorks suite for topology optimization, along with HyperMesh, the HyperWorks meshing tool. In December 2010, the company extended its use of HyperWorks to RADIOSS, the product suite's solver, to its development process for the analysis of the behavior of composite materials. To design and optimize the carbon structures of the yachts, ABstructures is using HyperWorks together with other computer-aided engineering (CAE) tools to simulate composites and fluid-structure interactions. ABstructures has achieved fundamental structural improvements of all the yachts it has designed, compared to older-generation yachts. Arif Senol Sener[5], in his work studied the construction and standardization of a track for performing fatigue and reliability test of light commercial vehicles is described. For the design and process verification of the company’s vehicles one test track is defined. A questionnaire was used to determine the average usage of light commercial vehicles in Turkey. Fatigue characteristics of Turkish roads were determined by analyzing fifty different roads and this article focuses on defining the load spectrum and equivalent fatigue damage of the leaf spring resulting from the accelerated test route. Fatigue analysis and estimated lifespan of the part were calculated using Finite Element Analyses and verified by the Palmgren-Miner rule. When the customer profile is taken into consideration; Turkish customer automotive usage profile, the aim of usage of this kind of vehicle (LCV), fatigue characteristics of Turkish roads for this vehicle were determined and around Bursa one accelerated test tracks were formed for the reliability and fatigue test for the related company, linear analysis executed on the FEA of the spring was more convenient were obtained. II. VIBRATION AND NATURAL FREQUENCY Most of the IC engines developed earlier were less fuel efficient, more polluting and noisy, but recently there has been a growing concern in society toward environment and aesthetic awareness. This had let to the development of advanced engines using state of art technology. Vibration in IC engine has emerged as a significant factor to be considered in designing IC engine as it can have a negative impact in various engine components. This happens when the natural frequency of the component coincides with the forced frequency produce by the engine. One of the parts which can be affected by this phenomenon is the cylinder head cover. If due care is not taken in the designing of the CHC, it might lead failure of component. If the CHC fails their might be leakage of engine oil due to which there is possibility of catastrophic accident hence it becomes important to design the CHC properly. This work is based on evaluating the natural frequency through the FEM analysis.
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 170-179 © IAEME 172 III. REASON OF USING FEM FOR THE WORK In the present scenario the Cylinder Head Cover is being analyzed, and due to the advantage of nondestructive testing associated with FEM, it is possible to analyze a large number of modifications of the component without being actually manufacturing it. Also as observed from previous studies the results of FEM analysis have shown considerable accuracy with the actual results. IV. FEM ANALYSIS The finite element method (FEM) also known as finite element analysis (FEA), with help of this numerical technique we can find approximate solutions of partial differential equations (PDE) as well as of integral equations. This approach for the solution of steady state problems is based either on eliminating the differential equation completely, or rendering the PDE into an approximating system of ordinary differential equations, which are further numerically integrated using standard techniques such as Euler's method, Runge Kutta, etc. The primary challenge in solving partial differential equations, is to create an equation that approximates the equation to be studied, but is numerically stable, meaning that errors in the input and intermediate calculations do not accumulate and cause the resulting output to be meaningless. There are many ways of doing this, all with advantages and disadvantages. The Finite Element Method is a good choice for solving partial differential equations over complicated domains (like cars and oil pipelines), when the domain changes (as during a solid state reaction with a moving boundary), when the desired precision varies over the entire domain, or when the solution lacks smoothness. For instance, in a frontal crash simulation it is possible to increase prediction accuracy in "important" areas like the front of the car and reduce it in its rear (thus reducing cost of the simulation); another example would be the simulation of the weather pattern on Earth, where it is more important to have accurate predictions over land than over the wide-open sea [1]. A variety of specializations under the umbrella of the mechanical engineering discipline (such as aeronautical, biomechanical, and automotive industries) commonly use integrated FEM in design and development of their products. Several modern FEM packages include specific components such as thermal, electromagnetic, fluid, and structural working environments. In a structural simulation, FEM helps tremendously in producing stiffness and strength visualizations and also in minimizing weight, materials, and costs. This powerful design tool has significantly improved both the standard of engineering designs and the methodology of the design process in many industrial applications.[7] The introduction of FEM has substantially decreased the time to take products from concept to the production line. It is primarily through improved initial prototype designs using FEM that testing and development have been accelerated. In summary, benefits of FEM include increased accuracy, enhanced design and better insight into critical design parameters, virtual prototyping, fewer hardware prototypes, a faster and less expensive design cycle, increased productivity, and increased revenue. V. ANALYSIS Meshing This exercise involves changing the shape of a part in order to simplify the geometry. Certain details of the shape, such as small holes or blends, may simply not be necessary for the analysis being performed. When these details are removed, the analysis can run more efficiently. Additionally, mesh quality is often improved as well. Changing the geometry to match the desired shape can also allow a mesh to be created more quickly.
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 170-179 © IAEME 173 Meshing includes -: • Mesh the clip, review the mesh quality, and determine the features to be simplified • Remove surface fillets • Remove edge fillets The model file has geometry that has been midsurfaced. (Surfaces have been created on the mid-plane of the part. Fig 1: Meshing of an small element is shown below.this mesh is generated by using command “auto mesh” Fig 2: The element selected for the meshing is “quads” and the element size is 10.0. Fig 3: The above fig explains how the whole as geometry is meshed. In some places it is required to generate the mesh type of “mixed” Analysis setup in Optistruct This section will contain analysis part of meshed mid plane. The solver used is Optistruct. a) Control cards will be allotted b) Different material to the geometry will be assigned. c) Property card will be assigned. d) Creation of load collectors. e) constrained will be applied
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 170-179 © IAEME 174 Fig 4: Component Table Fig 5: Material Table Constrained Will Be Applied • The process of debarring of the motion is performed by applying constraints on the system during simulation on OPTISTRUCT. • These applied constraint acts as boundary conditions while solving the equations generated by the solver OPTISTRUCT to derive a conclusion.
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 170-179 © IAEME 175 Fig 6: Node to be Constraint Fig 7: Node selection for Constraint Fig 8: Bolt Constraint Fig 9: Constraint along bolt and seal The purpose for using a finite element (FE) pre-processor is to create a model, which can be run by a solver. A finite element solver can solve for responses of parts to loading conditions on them. The loads can be in the form of boundary constraints, forces, pressures, temperatures, etc. In this the solver input files are created using different templates. More specifically, loading conditions on a model specify solver specific controls are defined and input file to a solver from Hyper Mesh will be submitted. Fig 10: The constraints are applied on the place where gasket is to be attached throughout the edges of CHC. The white pattern in above pic shows that constrained has been applied throughout the nodes at the edges (nodes) represented by the color purple
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. For Aluminum material The further analysis results in next mode natural frequency as follows Fig 11: For the mode 1, the graphical representation for displacement. The red color shows the max displacement and then in decreasing order till the blue color Fig 13: White point denotes the location of node formaximum displacement. NODE ID 303314(DOF) International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 6359(Online), Volume 5, Issue 5, May (2014), pp. 170-179 © IAEME 176 The further analysis results in next mode natural frequency as follows -: , the graphical representation for displacement. The red color shows the max displacement and then in decreasing order till the blue color Fig 12: For the mode 1, the graphical representation or stress is shown. The red color shows the maxstress and then in decreasing order till the blue color White point denotes the location of node formaximum displacement. NODE ID 303314(DOF) Fig 14: White point denotes the location of node for maximum stress. NODE ID 325832(DOF) International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), , the graphical representation or stress is shown. The red color shows the maxstress and then in decreasing order till the blue color White point denotes the location of node for maximum stress. NODE ID 325832(DOF)
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 170-179 © IAEME 177 For Aluminum material and thickness is reduced When the thickness of CHC is reduced to half, it will influence the structure. As natural frequency is a geometric property hence get changed. The observed natural frequency at mode1 is 693 Hz. The further analysis results in next mode natural frequency as follows -: VI. RESULTS AND DISCUSSION Natural frequency is a function that depends on the geometry, material properties and structure. Generally for a four stroke vehicle with the engine of 1100cc has the vibrating frequency of 300-400 Hz at full speed. Therefore our first aim is to produce a design which has natural frequency well above the 1000 Hz, so that at any conditions the structure must not fail due to resonance. Fig 15: For the mode 1, the graphical representation for displacement is shown below. The red color shows the max. Displacement and then in decreasing order till the blue color. Fig 16: For the mode 1, the graphical representation for stress is shown. The red color shows the max. Stress and then in decreasing order till the blue color
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 170-179 © IAEME 178 Comparison of natural frequency in different cases. For the given geometry, material properties and structure of the CHC, the analysis comes to the output natural frequency for different cases as below-: Column1 Aluminum Aluminum with halved thickness mode1 1195 Hz 693 Hz mode2 1346 Hz 843 Hz mode3 1542 Hz 1045 Hz mode4 1785 Hz 1241 Hz mode5 2051 Hz 1256 Hz mode6 2288 Hz 1323 Hz This table shows that the min natural frequency so obtained at 1st mode is for the aluminum CHC which is 1195 Hz, but still, it can be concluded aluminum system is well safe for the expected conditions of the vehicle. But to improve the performance and reduction in weight, it requires slight variation. The variation is generated by reducing the thickness of aluminum CHC to half. By reducing the thickness to half, the weight of the aluminum CHC is reduced to half but the strength of the system also decreases mentionable. But as far as natural frequency is concerned, it decreases dramatically to 693 Hz for 1st mode. This means now this CHC is able to avoid resonance condition to a much greater extend and hence, may be used for bigger vehicles. The parameter for the Eigen mode is displacement in our case the Eigen mode gives i.e. displacement for a given mode at every node. To find the required from the multi degree of freedom system it is needed to be solved by the matrix method. In this the parameter to be finding is represented by the Eigen values of the matrix system. Each node has its own boundary condition and its own Eigen value for matrix system. Therefore by solving the matrix system under a given set of boundary conditions i.e. constraint it can be solved for the Eigen value at every node. Hence different parameter such as displacement stress can be finding at each node by appointing them as Eigen value for the each node in the system. Comparison of Eigen modes in different cases In the analysis of CHC to avoid the condition of resonance, it is required to find the natural frequency of the system. When a given system is being vibrated under the set of constraint the each element at molecular level displaces from its position. The molecular level in this case of analysis is defined by the nodes and the rectangular elements. When displacement is defined as the parameter and appointed as Eigen mode then the solver will solve the system equation for the displacement at each node. This whole process of solving the different equation and matrixes is carried out in Optistruct and result so obtain of Eigen values is shown in hyper view. On defining the displacement as Eigen mode the result concluded are as follows for different cases.
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 5, May (2014), pp. 170-179 © IAEME 179 For Mode 1 Natural frequency Maximum displacement Minimum displacement Aluminum 1195 Hz 45.83 mm 5.79 mm Aluminum with halved thickness 693 Hz 67.42 mm 7.49 mm The above displacement-comparison table shows that when “aluminum” is used as material the natural frequency, at first node was 1195 Hz. And the maximum displacement is of 45.83mm mainly at top center part nodes. Also the minimum displacement for the same condition is 5.79mm is observed at edges and nearby regions. Conclusion and future work In our normal mode analysis of cylinder head cover for aluminum material, it is found that natural frequency for mode 1 is natural frequency 1195 Hz. For saving the cost of aluminum material r the thickness of cylinder head cover can be reduced by the factor of 0.5 times. For this thickness we had obtained the natural frequency 693 Hz. After finding the natural frequency of aluminum cylinder head cover. Now we can convert this aluminum CHC into plastic material and can found natural frequency of plastic component, the advantage of conversion may be reduced the cost and weight of the component. REFERENCES 1) Prashant D. parikh, “A finite element analysis of the static and dynamic behavior of automobile tire, 1977. 2) Wai Hung ho, B.S, “A comparison of simulation methods with finite- difference and finite element method for solving Vlasov-Poisson system” August, 1986. 3) www.tallent.thyssenkrupp.com 4) www.abstructures.com 5) Arif Senol SENER Head of Automotive Technology Division, Vocational High Schools, Istanbul Aydin University. 6) Brian D. Camp, “A class of immersed finite element spaces and their Application to Forward and inverse interface problems” November 19, 2003. 7) Syed Faheem Haider Abidi, “Determination of mechanical properties of EN24 alloys using miniature specimen test technique and FEM, may 2008. 8) Rao V. Garimella, “Anisotropic Tetrahedron Mesh Generation” May 1999” 9) Mustafa Elsheikh, “A Generative Approach to Meshing Geometry” September 2010. 10) Rahul Davis, “A Parameteric Design Study of Surface Roughness in Dry Turning Operation of EN24 Steel”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 2, 2012, pp. 410 - 415, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. 11) Madhura.S, Pradeep B Jyoti and Dr.T.V.Govindaraju, “FEM Based Modelling of Amb Control System”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 3, 2013, pp. 191 - 202, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.