Final Fea Report
Finite Element Analysis
Report
Introduction
Stressed skin structures are used prominently in aircraft design. These are placed under load on a daily basis, and thus must be monitored for safety reasons. When a metal or plate is placed under a load, the stress is usually never uniformly distributed throughout the part. Instead, it is concentrated in certain areas. Naturally, these areas of stress concentration are subject to fatigue and cracking more so than other elements on the metal. Furthermore, stress concentrations occur mostly, and are magnified by any discontinuities on the part, such as holes or cracks. The stress concentration factor is a measure of how localised these stresses are. This factor can be easily obtained through the use of specialised software offering finite element analysis.
Modelling Approach & Assumptions
Assumptions and Simplifications
The type of analysis conducted was a linear static analysis. This involves applying static loads to a model and using these to analyse the stresses formed. This particular type of analysis was used to simplify the model. Furthermore, in a static analysis, the loads are applied gradually. This eliminates any additional displacements and stresses otherwise caused by suddenly applied loads.
There are three main assumptions made when conducting a linear static analysis: Linearity Assumption: The induced response is directly proportional to the applied loads. This means that if you double the magnitude of the loads, the response of the material (Stresses, Displacements, etc.) will also double. Elasticity Assumption: The part is not stressed beyond its yield point. This means that there is no permanent deformation and the part will return to its original shape if the loads are removed. Static Assumption: Loads are applied slowly and gradually until they reach their full magnitudes.
Symmetry
Since all of the cut-outs in the assessment task are symmetrical in 2 planes, symmetry was used in
Report
Introduction
Stressed skin structures are used prominently in aircraft design. These are placed under load on a daily basis, and thus must be monitored for safety reasons. When a metal or plate is placed under a load, the stress is usually never uniformly distributed throughout the part. Instead, it is concentrated in certain areas. Naturally, these areas of stress concentration are subject to fatigue and cracking more so than other elements on the metal. Furthermore, stress concentrations occur mostly, and are magnified by any discontinuities on the part, such as holes or cracks. The stress concentration factor is a measure of how localised these stresses are. This factor can be easily obtained through the use of specialised software offering finite element analysis.
Modelling Approach & Assumptions
Assumptions and Simplifications
The type of analysis conducted was a linear static analysis. This involves applying static loads to a model and using these to analyse the stresses formed. This particular type of analysis was used to simplify the model. Furthermore, in a static analysis, the loads are applied gradually. This eliminates any additional displacements and stresses otherwise caused by suddenly applied loads.
There are three main assumptions made when conducting a linear static analysis: Linearity Assumption: The induced response is directly proportional to the applied loads. This means that if you double the magnitude of the loads, the response of the material (Stresses, Displacements, etc.) will also double. Elasticity Assumption: The part is not stressed beyond its yield point. This means that there is no permanent deformation and the part will return to its original shape if the loads are removed. Static Assumption: Loads are applied slowly and gradually until they reach their full magnitudes.
Symmetry
Since all of the cut-outs in the assessment task are symmetrical in 2 planes, symmetry was used in
References: Websites Patran Tutorials: http://www.mscsoftware.com/training_videos/patran/Reverb_help/index.html#page/Finite%20Element%20Modeling/mesh_forms.03.4.html Modelling Errors and Accuracy Notes: http://www.me.mtu.edu/~bettig/MEEM4405/Lecture10.pdf Linear Static Analysis Notes: http://www.kxcad.net/SolidWorks/COSMOSXpress_Tutorial/topics_general/Assumptions_of_Linear_Static_Analysis.htm Books “Finite Element Modeling for Stress Analysis”, R D Cook, Wiley 1995 “Mechanics of Materials”, R C Hibbeler, Pearson Prentice Hall