8/1/2009. CAE 7962 Presentation

Transcription

1 CAE 7962 Presentation Gavin Patey Dameion Moores Aaron Henstridge Ashley Burke Brendan Harvey Fabio Faragalli Introduction Choosing mesh properties Explanation of the types of studies available and the limitations of each Static Frequency Buckling Thermal Drop Test Fatigue Optimization Nonlinear Conclusions COSMOS Works is a powerful application which allows Finite Element Analysis studies to be conducted on 3D models FEA is a numerical technique for finding approximate solutions of partial differential equations (PDE) as well as of integral equations Requirements Geometry Boundary Conditions Loads & Restraints System Response Expectations Testing Define Meshing and Element Type Conduct Appropriate Test (Based on Response Expectations) Mesh Types Solid Mesh Shell Mesh (Surfaces & Mid surfaces) Beam Mesh Mixed Mesh Mesh Options Mesh size control User Defined Automatic Transition Smooth Surface Mesh Quality Jacobian Check Assumptions Static Assumption Linearity Assumption Inputs Restraints Loads Results / Outputs Deformation 1

2 Water Storage Tower 7,666,515 N Load Applied Analysis Analysis No Force Applied Deformation Analysis Analysis Loads are approximated across an entire planar face To approximate a point load, a small flat surface must be modeled This alters the shape of the part Does not provide absolute results regarding whether or not part will beak Inputs Restraints Modes to be extracted Results / Outputs Plots (X,Y,Z) Deformation Mode Shapes Thermal Effects Diving Board System displaying Frequency Analysis Displays modal (resonant) frequencies of the system Can be compared to surrounding frequencies such as: Frequency caused by a diver running down the board Frequency output of a nearby filtration pump Cannot compute stress, strain, or factor of safety Loads such as the members weight is ignored Do not need to apply load for frequency study, if loads are applied, the results may skew. If applying loads its important to be accurate 2

3 Inputs Completed Static Study Results / Outputs (X,Y,Z, Maximum Resultant Displacement) Deformation The Buckling Study is an extension of a static study This study can help to define the axial load and crosssectional area limitations of the part in question Example: Long slender rod axially loaded Outputs only include displacement and deformation Type Steady State Transient (Non linear) Load Conditions Temperature Convection Radiation Heat Flux Heat Power Contact Resistance Results / Outputs Temperature Distribution Temperature Gradients Heat Flux Properties at specified times (transient ) A burger being cooked on a BBQ was modeled to demonstrate the capabilities of the thermal study The following thermal constraints were applied to the system Heat power on the bottom surface of the BBQ Heat flux and convection loads on the grill Radiation on the surfaces Contact resistance between the burger and the grill Conduction is automatically calculated by Cosmos based on material properties selected BBQ Before thermal effects Steady State Thermal Conditions 3

4 Many user input variables needed for accurate results Transient analysis is very time consuming and requires much computational resources Some required variables such as shape factors need to be calculated manually Inputs Acceleration Constraints Drop Height Orientation of Impact Plane Target Impact Properties (Stiffness, Rigid, Flexible) The Drop Test Study was represented by dropping a ceramic dinner plate from a height of 1.5m. Analysis of Stress, Strain, Displacement and Deformation are shown in the following images. Results / Outputs (Throughout Specified Interval) Displacement Analysis Does not predict the failure of solid parts or separation of bonded components due to impact Strain Analysis Stress Analysis Requires large amounts of memory and computation time Often cannot be conducted on non simplistic models using standard computers (MUN) Drop Clip 4

5 Extension of Static Study Applies a static load for a specified number of cycles Inputs Completed Static Study Torque or cyclic load Number of Cycles Restraints Results / Outputs Life of the part Areas of failure Step Shaft Without load Applied Step Shaft With a Torque of 30N m Accurately choosing the number of cycles to best evaluate the part Allows selected model aspects to be optimized with respect to specific selected parameters Material variety with corresponding S N curves Typical aspects would include mass, cost, and dimensions. Typical parameters would be stress, strain, and displacement Design optimization will increase the value of a product by improving its performance and reducing production costs Requirements Static Study Buckling Study Frequency Study Thermal Study Inputs Objective Function (mass, dimensions, cost) Design Variables (material, dimensions, cost) Behavior Constraints (Stress, Strain, FOS, etc.) Results / Outputs Optimized design based on chosen input parameters A mounting bracket was statically optimized with respect to total mass, dimensions, stress, and strain. Objective Function: Mass Design Variable: Dimensions (Thickness) Behavioural Constraints (Stress and Displacement) Displacement Stress 5

6 Thickness of part was reduced Applied to a transient system, or a system containing nonlinear elements Can be applied to any available COSMOS study which can be nonlinear in nature Static studies typically involve nonlinear materials. Assumptions made regarding stating loading (forces applied slowly etc.) can now be neglected Original Design Optimal Design Thermal studies can generally be transient in nature Test Suitability Material non linearity Geometric non linearity Boundary non linearity Overall nonlinear system (transient) Inputs Material Behavioral Properties Nonlinear Elastic Viscoelastic Ogden Hyperelastic Loads & Restraints Results (Time dependent) Plastic (High Density Polyethylene) hanger showing displacement over a 10 second time interval Initial Time = 5 seconds Max Load of 450N Residual stress remains even after loading have been removed Hanger has been plastically deformed Evident from the displacement plot Requires larges amounts of memory and computation time Often cannot be conducted on non simplistic models 6

7 Define your requirements: Material, Loads, Restraints, Mesh Properties, etc COSMOS Works uses FEA to conduct various studies which output plots displaying: Resonant Frequency Buckling Thermal Fatigue Generates deformation representations and optimum designs. COSMOS Works has multiple limitations including: Loads are applied across an entire planar face. Drop test and non linear test requires much memory and long computation time which increases with the complexity of the part. Combinations of specific types of studies. COSMOS Works is a powerful tool, but user familiarity is import in order to ensure the proper parameters are selected to provide accurate results. 7