Analysis of Plate Bending Machine using RADIOSS and OptiStruct

Transcription

1 Analysis of Plate Bending Machine using RADIOSS and OptiStruct K. Rajasekar Reddy Assistant Manager Larsen & Toubro Limited, Heavy Engineering Ship Building Center, Godavari Gate, Scindia Road, Visakhapatnam ,India rajasekar.reddy@vzw.ltindia.com Keywords: Concept Design, Finite Element model, Structure Optimization. Abstract The paper speaks about the Linear Static Analysis of Structure for Plate Bending Machine using HyperMesh, RADIOSS and OptiStruct. Finite Element Model is built using HyperMesh and Linear Static Analysis is carried out using RADIOSS to find the stresses & deformations induced in the structure. After the study of Stresses and Deformation contours using HyperView, the Basic design is worked upon for optimization using Optistruct to reduce the material & manufacturing costs. Optimization of the Structure is carried out using Topology Optimization Technique and the results obtained are used to finalize the Optimized Structure for Plate Bending Machine. Introduction Bending machine is intended for bending plates of 20mm thickness and 6500mm width and estimated capacity for carrying out bending is 300T. 4nos Hydraulic cylinders with 75T capacity each are accommodated in the structure. Basic design given by Production Department in line with the existing 200T capacity bending machine. The details of the weight of the structure of Plate Bending Machine as per the Basic design is as follows 1) Vertical Pillar Assembly T 2) Punch T 3) Bed Assembly T Total weight T The Basic design is analyzed to find the stresses and deformations induced due to the self weight and reaction forces exerted by the hydraulic cylinders mounted in the machine. Based upon the results from Linear Static analysis using RADIOSS, it is optimized using OptiStruct. The Optimized design is analyzed to find the stresses and deformations in order to check whether they are within the acceptable limits specified by customer. Process Methodology The Process Methodology involved in carrying out Linear Static Analysis using RADIOSS and OptiStruct is elaborated in the following steps: a. Building of Finite Element Model using HyperMesh b. Linear Static Analysis using RADIOSS c. Optimization using OptiStruct d. Validation of Final design using RADIOSS a. Building of Finite Element Model: The Finite Element Model is built using HyperMesh from Altair HyperWorks Simulation Driven Innovation 1

2 The structure of Plate Bending Machine is divided into three sub assemblies ( Refer Figure-1) as below i. Vertical Pillar Assembly ii. iii. Punch Bed Assembly The model is build with Shell elements at the mid surface and rigid elements to represent the Hydraulic cylinders. The number of triangle elements existing are less than 5% of total number of elements in the Finite element model. Following Quality checks are maintained for the elements i. Warpage :<10 ii. Aspect : <5 iii. Skew : <60 iv. Jacobian : <0.6 v. Max. quard angle: <135 vi. Min. quard. angle: >45 Following Pre checks are done before Boundary Conditions and loads are applied to the model i. Elimination of Free Edges and T-connections in the model ii. iii. iv. Normal's check Renumbering Assignment of material and physical properties to the respective components created Boundary Conditions and loads are applied to the individual assemblies as shown in Figure 2a, 2b, 2c. Vertical Pillar Assembly Representation of Hydraulic Cylinder with Rigid elements Punch Bed Assembly Figure 1: Finite Element Model of Plate Bending Machine Simulation Driven Innovation 2

3 Vertical Reaction Load of 300T(load by Hydraulic Cylinder) applied vertically at 4 locations Constraints applied at the bottom surface Figure 2.a: Details of Boundary Conditions and Loads applied on Vertical Pillar Assembly Load of 300T(75Tx4) by Hydraulic Cylinders at 4 locations Constraints applied at the Bottom surface when it is in contact with the Plate to be bended Figure 2.b: Details of Boundary Conditions and Loads applied on Punch Uniformly distributed load of 300T is applied on the Rollers Constrains applied at the bottom surface of the bed Figure 2.c: Details of Boundary Conditions and Loads applied on Bed Assembly Simulation Driven Innovation 3

4 b. Linear Static Analysis using RADIOSS: The Linear Static Analysis is carried out using RADIOSS for the subassemblies of Basic design of Plate bending machine. Obtained results are illustrated in Figure 3.a, 3.b, 3.c.In reference to the Displacement and VonMises Stress contours, the Basic design is worked upon for Optimization. Figure 3.a: Vertical Pillar Assembly- Maximum Deformation is 4.09mm and VonMises stress is 195.8N/mm 2 Figure 3.b: Punch-Maximum Deformation is 0.176mm and VonMises stress is 154.3N/mm 2 Figure 3.c: Bed Assembly-Maximum Deformation is 0.138mm and VonMises stress is 46.8N/mm 2 Simulation Driven Innovation 4

5 c. Optimization of Basic design using OptiStruct: Optimization of the Structure of sub assemblies is carried out using Topology Optimization Technique by applying Displacement and Stress as the constraints and Volume Fraction as the Objective using OptiStruct. The Element Densities and Element Thicknesses contours obtained are illustrated in Figure 4.a, 4.b, 4.c. The Output results from OptiStruct are used to finalize the Optimized Structure for Plate Bending Machine. The final design obtained is lead to approx 45% reduction in Material & Manufacturing cost. Figure 4.a: Vertical Pillar Assembly- Element Densities and Element Thicknesses contours Figure 4.b: Punch- Element Densities and Element Thicknesses contours Figure 4.c: Bed Assembly- Element Densities and Element Thicknesses contours Simulation Driven Innovation 5

6 d. Validation of Final design using RADIOSS The Final design is achieved by removing the unwanted material and by reducing the thicknesses were ever applicable from the Basic design in reference to the Element Densities and Element Thicknesses contours. Linear Static analysis is carried out for the Final design to find the stresses and deformations. Results obtained are illustrated in Figure 5.a, 5.b, 5.c.It is found that the deformations and stresses obtained are well within the allowable limits specified by customer. Figure 5.a: Vertical Pillar Assembly- Maximum Deformation is 3.385mm and VonMises stress is 194.3N/mm 2 Figure 5.b: Punch- Maximum Deformation is 0.186mm and VonMises stress is 156.3N/mm 2 Figure 5.c: Bed Assembly- Maximum Deformation is 0.178mm and VonMises stress is 64.9N/mm 2 Simulation Driven Innovation 6

7 Results & Discussions: The details of results obtained through Linear Static Analysis of Basic and Final Designs are summarized as below: Sub Assemblies of Plate Bending Machine Weight(T) Table I: Summary of Results Basic Design Final Design(Post Optimization) VonMises VonMises Disp(mm) Weight(T) Disp(mm) Stress(N/mm 2 ) Stress(N/mm 2 ) Vertical Pillar Assembly Punch Bed Assembly Approx 45% of weight reduction in the Final Design is obtained as compared with its Basic design. The values of displacements and stresses obtained are found within the limits specified by the customer. Benefits Summary Following benefits are achieved : a. Instant decision making for Structure modification by studying the contours b. Approx 45% of reduction in manufacturing and material cost c. Enhance the level of customer confidence d. Expecting more number of projects related to Design modifications and Optimizations Challenges One of the major challenges faced while undergoing the project is decision making on identification of material reduction. With the help Stresses and Displacement contours from RADIOSS solver and Element Densities & Element Thicknesses contours from OptiStruct solvers the mentioned problem is dissolved by which we achieved the final design with 45% reduction in manufacturing and material cost. Future Plans In view to the achievement of optimized design with customer satisfaction and in expectations of increase in Projects related to Design modifications, optimizations, proposal is put to the Management to upgrade the existing software. Conclusion The Final design obtained post Optimization reduced the Material and Manufacturing costs to approx.45% and it is released for manufacturing post approval from Customer. The machine will be seen under Operations in the next 3months. The Results and Contours achieved through RADIOSS and OptiStruct Solvers provided value addition to the Project by reducing approx. 45% in material and manufacturing costs and reduction in time in finalizing the Design. ACKNOWLEDGEMENTS I would like to acknowledge Mr.A.K.Srivastav, Head Of Department,Production Engineering, L&T, Heavy Engineering for supporting and guiding throughout the project. I would like to acknowledge Mr.Ramesha B S, Technical Manager and Mr.Anshuman Panda, Sales Manager from Sales and Service Department of Altair Engineering India Pvt. Ltd. for providing Temporary License to run OptiStruct solver and for resolving the technical queries raised throughout the project. Simulation Driven Innovation 7