Finite Element Analysis of Structure of a Leather Cutting Machine

Transcription

1 e-issn Volume 2 Issue 8, August 2016 pp Scientific Journal Impact Factor : Finite Element Analysis of Structure of a Leather Cutting Machine Asif S. Pathan 1, P.T. Borlepwar 2 1 PG Scholar (MTech-Design), MIT Aurangabad, pathanasif25@gmail.com 2 Assistant Professor, Mechanical Engineering Department, MIT Aurangabad, prashant.borlepwar@mit.asia Abstract- Leather is a material used for the making of artifacts ever since early human history, and which can be used also in contemporary design for various types of interactive and electronic products. Leather cutting serves a crucial role in modifying the shape. Currently technologies which are applied for leather cutting include slitting knifes, manual cutting, die press techniques and Laser Cutting. Use of Die Cutting in collaboration electro-mechanical technology has grown significantly during recent years due to number of advantages over conventional cutting methods; flexibility, high production speed, possibility to cut complex geometries, easier cutting of customized parts, and less leftovers of leather makes Die Cutting more and more economically attractive to apply for leather cutting. Stress concentration and large displacements are usual problems in the components of the structure and that finite element method (FEM) can be a tool to minimize its effects. The Goal of this Paper is to analyse the Structure of Leather Cutting Machine and to get results of stresses and displacements of structure by using FEM for static simulation. For this work, fabricated structure is being designed followed by Finite Element Modeling and Analysis to verify its strength under the given working conditions. The Machine Structure is modeled using commercial software PTC CREO 3.0 and all the specification was accordingly followed the relevant drawing standard. Keyword- Static Simulation, Die Cutting, FEM, PTC CREO 3.0, Structure Analysis. I. INTRODUCTION For most production applications of machine tool structures, (gray cast iron) metal castings remain the primary choice because of cost, ease of sourcing, good damping with relatively high strength, good machinability and well-established and consistently achievable manufacturing and processing requirements. However, fabrications are normally the preferred choice for low volume production of large structures, due mainly to the high up-front molding costs and the difficulties in process control inherent in very large castings. At present, the existing Structure of the machine is being reviewed in the context of its suitability for the given range of applications/variants. In the broad sense, design of structure consists of two parts. The first parts deals with determination of forces at any point(or) of given structure and second part deals with the selection and design of suitable section to resist these forces so that the stresses and formation developed in the structure due to these forces are within permissible limits. The first part is termed as structural analysis and the second as proportioning or dimensioning of members. Before any analysis, we shall require the entire details of the structure, loading and functional properties. The purpose of structure analysis is to determine the reaction, internal forces such as axial, shear, bending and torsional deformations at any point of given structure caused by the applied loads and forces. II. APPLICATION OF FEA TO STRUCTURE OF LEATHER CUTTING MACHINE 2.1 Finite Element Analysis Methods The finite element method (FEM) rapidly grew as the most useful numerical analysis tool All rights Reserved 199

2 engineers and applied mathematicians because of it natural benefits over prior approaches. The main advantages are that it can be applied to arbitrary shapes in any number of dimensions. The shape can be made of any number of materials. The material properties can be non-homogeneous (depend on location) and/or anisotropic (depend on direction). The way that the shape is supported (also called fixtures or restraints) can be quite general, as can the applied sources (forces, pressures, heat flux, etc.). The FEM provides a standard process for converting governing energy principles or governing differential equations in to a system of matrix equations to be solved for an approximate solution. For linear problems, such solutions can be very accurate and quickly obtained. Having obtained an approximate solution, the FEM provides additional standard procedures for follow up calculations (post-processing), such as determining the integral of the solution, or its derivatives at various points in the shape. The post-processing also yields impressive color displays, or graphs, of the solution and its related information. Figure 1: Basic steps in FEA Today, a second post-processing of the recovered derivatives can yield error estimates that show where the study needs improvement. Indeed, adaptive procedures allow automatic corrections and resolutions to reach a user specified level of accuracy. However, very accurate and pretty solutions of models that are based on errors or incorrect assumptions are still wrong. When the FEM is applied to a specific field of analysis (like stress analysis, thermal analysis, or vibration analysis) it is often referred to as finite element analysis (FEA). An FEA is the most common tool for stress and structural analysis. The basic steps for performing analysis are listed below: Create the model geometry and mesh Identify the contact pairs Designate contact and target surfaces Define the target surface Define the contact surface Set the element KEYOPTS and real constants Define/control the motion of the target surface (rigid-to-flexible only) Apply necessary boundary conditions Define solution options and load steps Solve the contact problem Review the results FEA to Existing Machine Structure (Model Geometry) The Machine Structure is modeled using commercial software and all the specification All rights Reserved 200

3 accordingly followed the relevant drawing standard. The table geometry was shown in figure 2. The geometry of machine frame is modeled using competent software PTC CREO Meshing Details: Figure 2: CAD Model of Existing machine Structure Mesh generation is a process of dividing the structure continuum into a number of discrete parts or finite elements. The finer mesh, the better the results but longer the analysis time. Therefore compromise between accuracy & solution speed is usually made, 2-D Quad and Second order 10 noded tetra elements was used to create mesh model. Meshing interface is shown in fig Applying Material Properties: Stiffness of a structure depends on the geometry and its mechanical properties. The geometry of the model has been already defined by the CAD model; now we need to specify the material properties. The following are the material properties of given Leather Cutting Machine Structure, which is selected as per the Applications required Loading and Boundary Conditions: Table 1: Material Properties for Existing Structure The next step after meshing is applying loading and boundary condition. A Static load of N is applied gradually (As Uniformly Applied Load udl) over the entire machine bed through Centre of gravity of entire machine in Z- Direction Applying Constraints: Without constraints, the model is free to float in space and there would be no deflections in the model. Therefore, a model is required to be constraint so that it is allowed to deform, but restricted from a rigid body motion in any of the coordinate directions. Similar to loads, Constraints are always applied at the nodes. Sr. No. Parameter Description 1 Material AS3679 grade 300 (Low Carbon Steel) 2 Yield Strength 300 N/mm 2 3 Ultimate Tensile Stress 400 N/mm 2 4 Young s Modulus 210 X 10 3 N/mm 2 5 Density 7.85 g/cm 3 6 Poisson s ratio All rights Reserved 201

4 Figure 3: Loading and boundary condition For Existing Structure of machine In general, a node has 6-degrees of freedom (DOF), three translations (along x, y, z) and 3 rotations (about x, y, z). Constraints are applied to represent the supports on the model, by suppressing the appropriate translations and rotations Static Analysis (Solver) A static structural analysis determines the displacements, stresses, strains, and forces in structures or components caused by loads that do not induce significant inertia and damping effects. Steady loading and response conditions are assumed; that is, the loads and the structure's response are assumed to vary slowly with respect to time. A static structural load can be performed using the ANSYS, Samcef, or ABAQUS solver. A model is defined by some geometry (in 2D or 3D) in the geometry pre-processor (Creo Parametric). This is not as simple or transparent as it sounds, as discussed below. The model is transferred into Creo Simulate where material properties are specified, loads and constraints are applied, and one of several different types of analysis can be run on the model. This part is modeled using 3D solid elements. The primary results are shown in Figures 4 and 5. These are contours of the Von Mises stress3 on the part, shown in a fringe plot (these are, of course, in color on the computer screen), and a wireframe view of the total (exaggerated) deformation of the part (this can Here, we are usually interested in the value and location of the maximum Von Mises stress in the part, whether the solution agrees with our desired boundary conditions, and the magnitude and direction of deformation of the part Review the Results (Post Processor) The output of a solver is generally a very substantial quantity of raw data. This quantity of raw data would normally be difficult and tedious to interpret without the data sorting and graphical representation referred to as post-processing. Post-processing is used to create graphical displays that show the distribution of stresses, strains, deformations, temperatures, and other aspects of the model. Interpretation of these post-processed results is the key to identifying areas of potential concern (weak areas in a model), areas of material waste (areas of the model bearing little or no load), or valuable information on other model performance characteristics (thermal, modal) that otherwise would not be known until a physical model were built and tested {prototype}.after Applying the Static analysis using the tool CREO SIMULATE (Analysis) to Geometry of Machine Structure which is modeled using competent Software PTC CREO 3.0 the following results are obtained with different Variants, Variant 1: Existing structure Frame Existing Structure consists of two Support Bars having Cross-Section: b=40 & d=75, The Results of simulation are shown in Fig. 4 to Fig. 7 All rights Reserved 202

5 Figure 4: Meshing interface of Existing Machine Structure Figure 5: Displacement analysis for Existing Machine Structure Figure 6: Stress analysis (Von Mises) for Existing Machine Structure Figure 7: Stress analysis (All Principals) for Existing Machine structure VARIANT 2 & 3: Changing the Structure to minimize the Displacements & Stresses Performed taking C/S of Support Bars as 2) b=16 & d=250, and 3) b=20 & d=250 respectively. VARIANT 4: Changing the Structure to minimize the Displacements & Stresses New structure consists of two Support Bars having Cross-Section: b=24 & d=250, the geometry of machine Structure is modeled using competent software PTC CREO 3.0. The Results of simulation are shown in Fig. 8 to Fig. 11 below. Figure 8: Meshing interface New Machine Structure Figure 9: Displacement analysis for New Machine All rights Reserved 203

6 Figure 10: Stress analysis (Von Mises) for New Machine Structure Figure 11: Stress analysis (All Principals) for New Machine structure III. EXPERIMENTATION AND VALIDATION OF FEA RESULTS The reliability of FEA Module is validated by finding the values through iterative method (Formula Based) by Taking Material properties of machine structure. The values of Deflections & Stresses of Beams are calculated by direct integration (Numerical) Method considering there end conditions for Different variants (i.e. variants 1, 2, 3 & 4) and then the results are Quantitatively compared with results from FEA Module on the basis of these Validation the results are discussed. Following is validation of FEA Results, VALIDATION Whenever a beam (Support Bar) is loaded, it deflects from its original position, the amount by which a beam deflects, depends upon its cross-section and the bending moment. Following are the two criteria for deflection of beam considered in design, 1. Strength and 2. Stiffness, Maximum deflection and Stress in Support bar can be found by considering it as FIXED BEAM (Both End are Fixed) for different variants, as Shown in fig. 12. VARIANT 1: Existing structure Frame Cross-Section: b=40, d=75 & Length, l=1530 mm Material: AS3679 grade 300 (Low Carbon Steel) Young s Modulus: 210 GPa (210 X 10 3 ) Figure 12: Fixed Beam The deflection, at the Mid-Point, of a fixed beam under a Point Load is given by, Where, Y Max. Deflection of Beam in mm Y = Wl 3 W Load Carried by beam in N E - Young s Modulus of material in N/mm 2 192EI I Moment of Inertia of Beam about bending axis in mm 4 The total load 5 ton (50000 N) is supported by two beam, i.e. load carried by each beam is, W = N Moment of Inertia of beam about its bending axis, I = bd 3 = 40 x I = mm All rights Reserved 204

7 Max. Deflection of Beam in mm, Y = Wl 3 = (25000) x (1530) EI 192x210x10 3 x Y = mm The Bending moment at a section tends to bend or deflect the beam and the internal stresses resist its bending. This resistance, offered by internal stresses, to the bending, is called Bending Stress (σ b ), The Expression for Bending Equation for finding bending stress in beam is given by, M = σ b = E I y R As, Section Modulus, Z = I/y, Therefore, σ b = M/Z, Where, Moment of Resistance, M = WL/8 For Fixed Beam As, W = 25000, M = (25000x1530)/8... M = mm Also, Z = bd 2 /6.Since, its Bending Axis I =bd 3 /12 and Max. Distance from N.A., y= d/2 Z = 40x75 2 /6. Z = mm Therefore, Maximum Bending Stress in Fixed Beam is given by, σ b = M/Z = ( )/ (37500) =127.5 N/mm 2 For Variant 1.. Y = mm σ b = N/mm 2 VARIANT 2: For New Structure 2 Taking, Cross-Section: b=16, d=250 & Length, l=1530 mm, With Similar Iterations as in Variant 1, Max Deflection & Max Stress in beam are and Y = mm σ b = N/mm 2 VARIANT 3: For New Structure 3 Taking, Cross-Section: b=20, d=250 & Length, l=1530 mm, With Similar Iterations as in Variant 1, Max Deflection & Max Stress in beam are and Y = mm σ b = N/mm 2 VARIANT 4: For New Structure 4 Taking, Cross-Section: b=24, d=250 & Length, l=1530 mm, With Similar Iterations as in Variant 1, Max Deflection & Max Stress in beam are and Y = mm σ b = N/mm 2 IV. RESULT AND DISCUSSION Table 2: Comparison of Maximum displacement in all cases (FEA Results & Numerical) Variant Maximum Displacement (Y) in mm C/S: b=40, d=75 C/S: b=16, d=250 C/S: b=20, d=250 C/S: b=24, d=250 FEA Num. FEA Num. FEA Num. FEA Num e -04 All rights Reserved 205

8 Table 3: Comparison Maximum stresses in all cases (FEA Results) Variant Existing Structure (C/S: b=40, d=75) Structure 2 (C/S: b=16, d=250) Structure 3 (C/S: b=20, d=250) Structure 4 (C/S: b=24, d=250) Maximum Stress (σ b ) in kpa FEA Num. Ranking Based on Stresses & Feasibility in Manufacturing 9.64e e th 1.02e e rd 6.635e e nd e st From the analysis it is found that the existing machine Structure has maximum displacement upto and maximum stress is 9.64e+05 kpa. Among the different alternatives suggested the variant 4 i.e. (C/S: b=24, d=250) variant has lowest stress value among all geometries i.e kpa and displacement is 2.579e -04. As there is more cost involve in casting process and as compare to fabrication it is much complicated, we suggest fabricated structure i.e. variant 4, to be selected as a best possible solution for sponsoring company. V. CONCLUSION The results obtained are quite favorable which was expected. Finite element analysis is effectively utilized for addressing the conceptualization and formulation for the design stages. The stresses derived during the analysis phase normally indicate the potential solution. The iterations are carried out in the analytical phase which yields the suitable values for design parameter. The suggested variant of fabricated machine frame gives satisfactory results. Out of which variant 4 is selected as an optimum design solution by sponsoring company because of their suitability with ease of production, less manufacturing cost as compared to casting machine frame. The variant 4 has low maximum stresses as compare to existing machine Structure and it is much lower than yield stress so there life is much increased. REFERENCES [1] Nikola Korunović*,Miroslav Trajanović, Miloš Stojković, Dragan Mišić, Jelena Milovanović, Finite Element Analysis of a Tire Steady Rolling on the Drum and Comparison with Experiment - JME 57(2011)12, , Sept [2] M. Mahendran, Applications of Finite Element Analysis in Structural Engineering - International Conference on Computer Aided Engineering, pages pp , Chennai, India, [3] Evandro Pereira da Silva, Fábio Moreira da Silva, Ricardo Rodrigues Magalhães, Application of Finite Elements Method for Structural Analysis in a Coffee Harvester , 6, , Scientific Research Publishing Inc, Jan [4] Linko ping Institute of Technology, Department of Mechanical Engineering, S Linko ping, Sweden, Finiteelement analysis and simulation of machining: a bibliography - Journal of Materials Processing Technology 86 (1999) 17 44, Jan [5] Pratik R. Patel, V.K.Patel, Assistant Professor A Review on Structural Analysis of Overhead Crane Girder Using FEA Technique IJESIT Volume 2, Issue 4, July [6] Chittibomma.Tirumalaneelam1, Tippa Bhimasankara Rao2, Structural Analysis of a Milling Cutter Using FEA - IJCE Research, Vol, 03, Issue, 4, April [7] Amith Kalekar 1, S. B. Tuljapure 2, Stress Analysis of a Frame of a Bush Pressing Machine for Pumps IJIRSET, Vol. 4, Issue 2, Feb All rights Reserved 206