Use of Topography Optimization in Developing Bending Pattern of Compressor Mounting Plate in Refrigerator

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1 ISSN Use of Topography Optimization in Developing Bending Pattern of Compressor Mounting Plate in Refrigerator #1 Dayabhushan S. Thorat, #2 Akash.R.Suryavanshi 1 dayabhushanthorat@gmail.com 2 akash.suryavanshi@zealeducation.com #12 Department of Mechanical Engineering, Dnyanganga College of Engineering & Research, Pune-41,Maharashtra, India ABSTRACT The Optimization through FEA is new emerging field. Nowadays it is very necessary to shorten the development process of new components. Therefore tools are necessary that replace the natural evolution process by an automatic procedure. This topic includes the optimization terms that are connected with the optimization and FEA. Types of the optimization based on FEA are Topology optimization, Size optimization, Shape optimization and Topography optimization. The area of the project explains that, the design of the compressor mounting plate used in the refrigerator. The base plate of the refrigerator carries the load of the compressor & when the packaged product is there in the transportation. The compressor on the base plate applies the load on the base plate three times of the standard earth gravity due to uneven road condition and the bumps on the road. The Base plate fails in such loading. Hence, need to increase the stiffness of the base plate. Now a days the compressor mounting plate in the market are of 1.25 mm thickness. The challenge behind the project is to increase the stiffness of the 0.8 mm sheet metal base plate in such a way that the 1 st natural frequency of the base plate should be above the 60 Hz and its deflection should be below 5 mm for the static loading of three times of the standard earth gravity without addition & removal of the material. Study of Topography optimization and the FEA simulation tools has to do in the projects to achieve the success criteria and the final design of the CMP. ARTICLE INFO Article History Received :18 th November 2015 Received in revised form : 19 th November 2015 Accepted : 21 st November, 2015 Published online : 22 nd November 2015 Keywords CMP, FEA, Frequency, Optimization, Topography I. INTRODUCTION Experimental results from several academic and industrial researches have shown that compressor and fan are the main noise sources in a domestic refrigeration system. Simpler refrigerators do not use fan, while high-end refrigerators commonly use fans with low noise and vibration levels. Thus, generally, the compressor is considered the major source of energy for most cases when dealing with noise in refrigerators. Transient excitations generated by the compression process are considered quasi-periodic signals, with fundamental frequency equals to the compressor operation frequency (60Hz in North America and Latin America and 50Hz in Europe and Asia). In practice, as thesignals are quasi-periodic, several harmonics are present in the spectrum representation. Another important source of vibration is the compressor unbalance, which generates high vibration levels mainly in the fundamental frequency and first harmonics. Therefore, it is assumed in this work that the characteristic excitation of a compressor has the spectral distribution schematically illustrated in Figure 1.Topography optimization is an advanced form of shape optimization in which a design region for a given part is defined and a pattern of shape variable-based reinforcements within that region is generated. The approach in topography optimization is similar to the approach used in topology optimization, except that shape variables are used rather than density variables. In Topography optimization stiffness of component is increased by modifying the geometry of component. We prefer rectangular and oval shape bead formation of particular size 3mm in width and height and at an angle of 60 degree. Topography approach indicates the areas for 2015, IERJ All Rights Reserved Page 1

2 reinforcement which result in increase in stiffness of weak area. Figure 1. Characteristics excitation of compressor Sheet metal forming (SMF) is one of the most common manufacturing methods for metal parts and is used widely in industries. Modern software programs are routinely used by industries to study the characteristics of and to reduce the cost of sheet metal parts that are used in automotive and other applications. Virtual simulations that are based on complex math models and state-of-the-art computational tools play a very important role in reducing the high costs associated with prototypes and the time to market the product [6]. Formability studies of a sheet metal part determine if a part is formable by changing the factors that affect its formability. Vibration (or modal) analysis is performed to determine the frequency and mode shapes of the component or the assemblies, With the advent of highspeed computer technology and simulation tools, many industrial establishments are using virtual manufacturing processes to predict formability of sheet metal components before prototypes and testing are performed. Typically, there will be 3 6 different stages of forming operations before a final product is made. Each forming stage involves separate die and punch tool set, that costs several thousands of dollars for careful manufacture and to assemble. With tens and thousands of sheet metal parts in a typical automobile (doors, roof, trunk lid, fenders, etc.), and for several car and truck models, billions of dollars are spent annually by the auto and other transportation industries. Reduction of cost and cycle time to manufacture these parts are of paramount importance leading to lot of research in innovative production and optimization methods involving modern light weight and strong materials for the car body panels. Forming characteristics such as thinning, rupture (or splitting), wrinkling, etc., can be predicted and controlled with high level of confidence using the CAE tools such as Abaqus/Explicit (Simul AutoForm (Auto- Form Engineering), HyperForm (Altair Hyperworks),Dynaform/LS-DYNA etc. The solid model geometry prepared in CAD modelers can be easily imported into meshing algorithms such as Hyper Mesh. The model is then usually exported to high end solvers such as Hyper Form (one-step) or LS-DYNA (incremental) to perform the analysis after which, the formability results can be displayed using a post processor such as Hyper View or LS-Pre Post. Application of design of experiments (DOE) and Optimization procedures to study the inter-relation between the several forming parameters has been reported by many researchers. Both these methodologies have been used for several other applications within the design and manufacturing areas, the literature presented in this section is limited only to select references in the sheet metal forming area. At the beginning of the conventional design process the design engineer defines the shape and the topology of new components using the experience and the results gained from the forerunner. This results in an evolution process, which might lead to an optimum design after some iterations and a long period. Nowadays it is necessary to shorten the development process of new components. Therefore tools are necessary that replace the natural evolution process by an automatic procedure. With FEA Optimization softwares like ANSYS, OPTISTRUCR ( Hyperworks ), MSC/CONSTRUCT etc. it is possible to carry out optimization in the CAE environment. A. Requirement of the project( Need ) ime and cost saving for prototypes P rovides many design responses which can be used as a objective function. D ifferent types of stiffners like Embosses, beads etc. This can be used. U ser friendly. B. Challanges ow a days the compressor mounting plates in the market are of 1.25 mm thickness. The challenge behind the project is to increase the stiffness of the 0.8 mm sheet metal base plate in such a way that the 1 st natural frequency of the base plate should be above the 60 Hz and its deflection should be below 5 mm for the static loading of three times of the standard earth gravity without addition & removal of the material. It is really difficult task to increase the stiffness of 0.8 mm sheet metal plate natural frequency above 50 Hz ( for Asia ). Because the natural frequency of the base plate comes around 21 Hz only. earning of the optimization through FEA (Meshing, Preprocessing & Post processing ) by using Optistruct and analyse its needs. c ombination for the direction of linear beads is not available. M aximum width of the beads can not be controlled. R equired increase in stiffness to reduce the deflection and to increase the 1st natural frequency. C. Scope he scope of the project work leads to minimize, he expanses over the prototypes. 2015, IERJ All Rights Reserved Page 2

3 umber of resources and ultimately the cost for the prototype design. umber of resources and ultimately the cost of the resources for testing. ime required for the prototyping. C ost of the product in the annual income calculations. oise generated due resonance of compressor harmonics and compressor mounting plate. he deflection in the compressor mounting plate. r 1 Modulus of elasticity 2 Poisson s Ratio 3 Mass Density 4 Tangent Modulus 5 Yield Strength N/m2 2.1e5 Unit less 0.30 Kg/mm MPa (N/mm2) 2.1e3 MPa (N/mm2) 250 I. PROJECT WORK earning s of the Finite element procedure for Simulation. earning of properties and understanding the constraints of sheet metal forming. earning of FEA Software ( Ansys ). C ollection of compressor mounting plate data from the lab. C ollection of loading details. B ase plate simulation by using the tool Ansys. The Compressor Plate is used to mount a Compressor. This plate is very important in two aspects, one it take compressor weight and second it carries only vibration and noise source of refrigerator. To avoid damage to plate during transportation and handling it must be capable of handling 3g acceleration. This 3g value come from simulation results and Lab tests conducted for Drop Analysis as per company standards. The size of plate is large enough to have measure impact on cost. To keep the cost under control the thickness of the plate must be as low as possible. D. Problem Definition Objective: Maximize 1st frequency mode. Constrain: Plate deflection under load must be below 5 mm. Load: 3g X 17 Kg (Compressor mass) = 500 N (Distributed equally on 4 bolt location) Design Space: Entire plate except portion near plate mounting and Compressor mounting. Plate Thickness: 0.8 mm Bead Parameters: Minimum width: 10 mm, Draw Height: 5 mm and Draw Angle: 60 Bead Pattern: Cross pattern Material: Cold rolled steel Sr. No Table 1. Material Details Parameters of Connecting Rod Material Paramete Unit Scalar Value Figure 2. FEA model of Base compressor mounting plate II. RESULTS AND OBSERVATIONS A. Base plate simulation Initially the modal and structural simulation on the base plate is done using the tool Ansys. The results of the base plate for 0.8 mm thickness are shown in the fig 3 & fig. 4. Figure 3. First Mode frequency before optimization I n the base plate simulation it is observed that, The first natural frequency of the plate comes Hz. he vertical deflection observed is mm for the static load of 500 N. I t can be concluded from the results that, the 0.8 mm 2015, IERJ All Rights Reserved Page 3

4 base plate is very much weaker and need to increase it s stiffness The above fig.5 shows that the bead pattern to develop on the base plate to maximize the 1st natural frequency. The frequency gets from the above simulation is shown in below fig.6 Figure 4. Deflection in a base plate before optimization The main intension is to increase the stiffness of base plate without adding and removing the material. So, Here came in picture to optimize the base plate. Topography optimization is a special class of shape optimization, which can be used to change shapes of shell structures by introducing stamped beads for a better structural performance. B. Design Variables for topography optimization For topography optimization, a design space and a bead definition need to be defined. In this paper, bead parameters considered are Minimum width is 10 mm, Draw Height 5 mm and Draw Angle 60 deg. Symmetry of the bead pattern should be forced along the symmetry line of the design space.this analysis can be done with the help of software tool Optistruct ( Hyperworks ). The input for this simulation is to give objective function and constrained. In this case the objective function is to maximize the first natural frequency and the constrained is the plate deflection should be below 10 mm. Again need to give the response parameter like 1 plane symmetry, 2 plane symmetry, circular, planer etc. depending on the requirement of bead designs need to select the responses of bead parameter by considering it s functional requirements. The topography optimization results for the base plate are shown below. Figure 6. Natural frequency of optimized plate Figure 7. Change in frequency w.r.t. iteration The results of the optimized plate shows that the 1st natural frequency of the base plate is 90 Hz. If we observe the bead pattern on the base plate fig.5, The bead pattern is generated on flanges also but practically in forming process it is not possible to form the bead pattern on the flanges. Because while punching on flanges the flange it self will some uneven bending due to impact of punch. Hence due to this scenario need to generate its CAD model by avoiding the bead pattern on the flanges and check the results again. The CAD geometry for the above optimized plate is generated by using the CAD software tool Creo 2.0. The CAD geometry with reference to the optimized plate fig. 5 results is shown in below fig.8 Figure 5. Bead Pattern on base plate 2015, IERJ All Rights Reserved Page 4

5 Figure 9. Modal simulation results ( 1 st natural frequency ) F rom the figure 9 it is observed that the 1st natural frequency is Hz. he 1st mode of the compressor mounting plate shows the vertical up and down movement. At the compressor mounting plate but if its 1st natural frequency is Hz then it will not come in + or - 10 % the band of compressor harmonics i.e. 50 Hz ( 45 Hz to 55 Hz ) and there will not be any noise and vibrations. Figure 8. CAD Geometry of optimized plate without bead pattern on the flanges. The fig.8 shows CAD geometry of optimized plate, In the CAD geometry it can be observed that, there is no bead pattern on the flanges because it is not possible in forming process. The solver optistruct just have given these results based on the inputs. In the input bead responses it has been given that the 1 plane symmetry from the centre that s why it is showing the symmetric bead pattern from the centre and showing bead patterns on the flanges also. So, need to observe the results of above fig.8 compressor mounting plate. Because as we have removed the bead pattern from the flanges the plate stiffness will reduce and ultimately its first natural frequency will also reduce. In this project work the objective function is to maximize the 1st natural frequency above 50 Hz ( for Asia ). Because in Asian refrigerators the compressor operating speed is 3000 rpm. Hence it s 1st compressor harmonic will be 3000 / 60 = 50 Hz. Hence the objective function is to increase the 1st natural frequency above 50 Hz. The results for the optimized CAD geometry are shown below. The model analysis is done for the frequency prediction and the structural analysis is done to predict the vertical deflection of the compressor mounting plate by using the software tool Ansys15. Figure 10. Structural simulation result ( vertical deflection ) F rom the figure10 it has been observed that the vertical deflection of the compressor mounting plate is 3.55 mm. he vertical deflection is below the success criteria i.e 5 mm. MODELS 1 st NATURAL FREQUENCY, Hz VERTICAL DEFLECTION OF THE PLATE, mm Table 2. Result Table BASE PLATE OPTIMISED COMPRESSOR MOUNTING PLATE SUCCESS CRITERIA above 50 Hz Below 5 mm The punch for the optimized plate is shown in the below fig. 2015, IERJ All Rights Reserved Page 5

6 Figure 11. Punch for the central part Figure 12. Punch for the outer part Fig. 11 and fig 12 shows the punch for the plate. This punch can use during forming operation. Figure 13. Isometric view of the optimized plate Figure 14. 2D Thickness drawing Figure 15. 2D Front and top view The figure 13 shows the 2 D isometric view of the optimized plate. Figure 14 shows the thickness of the optimized plate and figure 15 shows the 2 D front and top view of the optimized plate. All the dimensions of the optimized plate are given in the figure number 15. C. Conclusion The design of the optimized compressor mounting plate passes the success criteria of the system. Hence instead of 1.25 mm thickness plate the 0.8 mm plate can be used in the refrigerators. It tends to save the material and as well as the cost of the compressor mounting plate. Topography optimization technique is the iterative method to optimize the component with the help of this technique one can give the optimum solution of the component. It tends to save the expanses and time over building the prototype. ACKNOWLEDGEMENT After successfully completion of my project, I would like to express my inner feelings with great facility to all the individuals who have helped me in completion of this project. First and foremost I would like to thank Dr. A. N. Gaikwad, Principal, Dr. G. M. Kakandikar, HOD & Guide Prof. A. R. Suryavanshi, Sir For their valuable guidance constant encouragement and sense of direction they gave me. It was their constant assurances that lead me to completion of this project. REFERENCES 1. Altair Hyper works 9.0 User s Guide, Optimization. 2. NX Nastran Design Sensitivity and Optimization User s Guide. 3. K.L. Yung, S.M. Ko, Weight optimization of sampling instruments for ESA Mars Express mission, Engineering Computations, Year: 2007, Volume: 24, Issue: 1, Page: Ming-Hsiu Hsu, Yeh-Liang Hsu, Interpreting three-dimensional structural topology optimization 2015, IERJ All Rights Reserved Page 6

7 results, Computers and Structures, Year: 2005, Volume: 83, Issues 4-5, Page: M. Vijay Kumar Reddy, P. Chitti Babu, K. C. K. Bharathi, Analysis of Light Motor Vehicle Component Using Topology Optimization Method, International Journal of Emerging Technology and Advanced Engineering, Year: 2014, Volume: 4, Issues 1, Page: Häußler, P.: Shape optimization of dynamically loaded parts in mechanical systems based on fatigue analyses, LMS User Conference on Physical & Virtual Prototyping, Dorint Hotel, Nürburg, Germany, Dr. F. Dirschmid, Optimization of Car Components using MSC/CONSTRUCT, MSC s 1st Worldwide Automotive Conference, Munich Silva, Olavo M.; Guesser, Thiago M.; Guesser, Igor M.; Pellegrini, Claudio de; Vendrami, Carlos E.; and Lenzi, Arcanjo, "Shape Optimization of a Compressor Supporting Plate Based on Vibration Modes" (2014). International Refrigeration and Air Conditioning Conference. Paper , IERJ All Rights Reserved Page 7