Modeling the Bracket in Solidworks - Assignment Example

Number: EAT216 Summary The aim of this assignment was to model a bracket using Solidworks then measure the amount of displacement and stress using Finite element analysis. From the results in the first part, the bracket was to be re modelled using recalibrated dimensions in order to achieve maximum work output when it is put to actual task in a real life application Introduction The entire design process is meant to maximize the potential of the bracket performance through the following ways: By carrying out marginal shape deviation of the model while maintaining the strength and deflection in the desired measure. By reducing the weight of the bracket. The initial procedure is to model the bracket in Solidworks according to the dimensions as per the instructions. Thereafter, Finite element analysis was done to determine the stress and displacement of the bracket. The results are then used to undertake weight optimisation of the model. The limits of the redesigned model are the face bearing the load, strength of the load and the fixed points which are not alterable. The only changing variables are the geometry and materials used. Part A The bracket was modelled from the drawing given and figures 1 shows the 3D model of the bracket. Figure 1: 3D model of the bracket Once the model has been created the material is applied in this case alloy steel. The model was then analysed in the SimulationXpress Analysis Wizard. The first step in this process was to fix the position of the 4 holes where the bracket will be fastened to the body of the structure. This is carried out in the fixtures section and the faces assigned as fixed geometry as shown in figure 2. This fixes the lower section of the bracket to its location in the machine, structure or component where it will be employed. Figure 2: Fixing of the holes of the geometry The external load on the geometry is a force of 1kN and is applied on the region of 750and 50mm from the upper section of the load bearing face. This force does not act on the whole region hence a sketch is created 50mm from the upper section and creating a split line to allow the force to applied on the hatched region of the load bearing face on the drawing. Figure 3 shows the model with the split line created. Figure 3: Model showing the split line separating the load bearing region The force is then applied and the part is subjected to static analysis using the Finite Element analysis method. This is as shown in figure 4 below. Figure 4: The part with all the fixture and loads applied The part was meshed using the default settings in Solidworks and the analysis carried out by running the simulation. The simulation results are produced giving the stress, displacement, deformation and the safety factor. Determining the maximum displacement and stress is the key objective at this point. The maximum Von Misses stress is 737.96mPa while the yield stress is 620.422mPa. This shows that the stress experienced is higher than the yield stress and hence failure due to the 1KN load applied. This is shown in figure 5. Figure 5: Von Misses stress contours The maximum displacement is shown in figure 6. The displacement experienced is maximum at the upper edge of the load bearing region and the value is 0.9134mm. Figure 6: Displacement contours of the part Part B The results from part A are used to carry out a redesign of the bracket which are then validated with Finite Element Analysis. The main objective of this redesign work is to reduce the weight of the bracket by at least 10% and the deflection should not be more than 10%. The bracket was optimised by analysis of the regions which are highly stressed basing the enhancement on the boundaries of the redesign work. The constraints in this case were: 1. All fixing points of the bucket must remain the same in terms of size and position. 2. The load bearing face must undergo no modification in terms of size and position. 3. The load must be the same in terms of size and direction. The fixing points are the holes for fastening the bracket to the component it is attached. The four holes were retained in the redesign. In this redesign work, the material was the main focus for reducing the weight of the bracket. The aim was to select a material similar to steel but is lighter in weight. Aluminium alloys offered the best choice with Aluminium 2014-T6 taken as the best choice (ASHBY, M. F. 2005). The challenge is the strength and this was solved by adjusting the geometry of the stiffening web in the side opposite to the load bearing region and increasing the number. The mass of the initial bracket from the mass properties section is 94.89 grams. The redesigned model is as shown in figure 8. The mass of the model is 85.4 grams. Figure 7: 3D model of the redesign The reduction in weight= The initial bracket shows the maximum stress exceeds the yield stress when the 1kN force is applied. The redesign needs the yield stress to be higher than the maximum stress. The Aluminium 2014-T6 alloy is less strong than alloy steel hence the web supporting the structure is increased in size and the number increased to two. This increases the stiffness of the load bearing region and hence the displacement and the Von misses stress is reduced. The holes for fastening on the component were also fixed as in the previous model and the load of 1kN applied as shown in figure 9. Figure 8: The model with fixture and load applied The maximum Von misses stress is 486mPa and the yield strength is 415mPa. The difference is quite less than for the initial bracket. Figure 10 shows the Von Misses stress contours obtained in the FEA analysis. Figure 9: Von Misses stress contours of the redesigned bracket The displacement contour is as shown in figure 11 and the maximum deflection due the applied force is 0.4091mm. The reduction in the deflection after the redesign is given by Percentage reduction in displacement ==55%. The percentage reduction in deflection is beyond the expectation since aluminium is less strong. Figure 10: Displacement contours of the re-designed bracket Conclusion The analysis of the initial bracket and re-designed one was successful and the objectives set out at the beginning were met. The maximum deflection of the re-designed bracket reduces as compared to that of the original. The material was changed from alloy steel to Aluminium 2014-T6 and hence the weight of the bracket reduces by 10% after the re-design without significant effect on the performance. The maximum stress reduces from 620.422mPa to 486mPa. The design changes made in the bracket during the re-design process are made in this report. References ASHBY, M. F. (2005). Materials selection in mechanical design. Amsterdam, Butterworth-Heinemann. http://www.books24x7.com/marc.asp?bookid=25372. Read More