Design of different elements of a pressurized capsule for stratospheric balloons

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Jiménez Higueras DEGREE IN Industrial engineering DIRECTOR OF THE

1 Design of different elements of a pressurized capsule for stratospheric balloons VOLUME II: ANNEXES STUDENT David Lázaro Jiménez Higueras DEGREE IN Industrial engineering DIRECTOR OF THE PROJECT Rafael Weyler Pérez CO-DIRECTOR Montserrat Sánchez Romero DATE June 2014

2 INDEX 1. Structural simulation General considerations Average window P-0041 simulation P-0040 simulation P-0038 simulation Entry study P-0016 simulation P-0017 Simulation P-0015 simulation Little window simulation P-0020 simulation P-0004 simulation Conditions table Catalogues

3 FIGURES INDEX Figure 1: Stress convergence study... 6 Figure 2: Deformations convergence study... 7 Figure 3: Study results... 7 Figure 4: 0002-P-0040 meshing... 9 Figure 5: 0002-P-0040 Stresses... 9 Figure 6: 0002-P-0040 deformations Figure 7: Inner frame mesh Figure 8: inner frame contraction Figure 9: Pressure distribution Figure 10: Meshing control Figure 11: 0002-P-0016 stress graph Figure 12: Entry deformations Figure 13: Inner frame control meshing Figure 14: Convergence graph Figure 15: Inner frame stresses Figure 16: Inner frame contractions Figure 17: Outer frame meshing distribution Figure 18: Outer frame Stress results Figure 19: Outer frame contraction Figure 20: Outer window stresses Figure 21: Outer window deformations Figure 22: Inner frame meshing properties

4 TABLE INDEX Table 1: Windows geometry... 5 Table 2: Convergence study... 6 Table 3: Shell properties... 8 Table 4: Meshing properties Table 5: Thermal converfence study Table 6: 0002-P-0016 meshing Table 7: Inner frame meshing properties Table 8: Convergence study Table 9: Outer frame meshing properties Table 10: Oouter window meshing properties Table 11: Outer window meshing distribution Table 12: Meshing properties Table 13: Inner frame stresses Table 14: Inner frame deformations Table 15: Flying conditions table

5 1. Structural simulation It is important to check the polycarbonate thickness under thermal and pressure conditions in order to find the main concentrations stresses. There is a double security redundancy due to double layering but in case of rupture all the windows shall stand pressure by themselves so we shall take into account our security factor of at least 2.0. The table below resumes the forces produced by the pressure differential in each window: Window Diameter(mm) Area (mm2) Result force (N) , , , , , , , , Table 1: Windows geometry 1.1. General considerations For the finite elements analysis of the windows, the following assumptions have been taken into account: 1. Shell behaviour of the windows. 2. The only load considered is the normal (internal) pressure to the surface. 3. Double layer windows for real considerations but single layer window for the stress/deformation analysis as each layer shall be able to stand all the pressure differentials. 4. The minimum safety factor to be applied is N= The internal pressure shall be fixed in 1 bar. 6. As a first iteration, we will use polycarbonate for the windows. Ideally, a UC specifically treated PC shall be used. 5

6 2. Average window The following simulations are referred to the average window P-0041 simulation Restrictions are defined by the dome s flat surface and the contact area with the inner aluminium frame. For that geometry we will simplify the model as a revolution body and applying a mesh control in the radius that connects the flat surface and the dome. In order to find meshing mistakes we will perform a convergence study to verify the simulation. In this simulation we are omitting all the holes for the screwery but, after the first draft simulation we have concluded that the main stress concentration is far from the hole s area. Meshing size Von Misses Stress Deformations [mm] [Mpa] Table 2: Convergence study Von Misses Stress [Mpa] Von Misses Stress [Mpa] Figure 1: Stress convergence study 6

7 1,5 1,45 1,4 1,35 1,3 1,25 Deformations [mm] Deformations [mm] Figure 2: Deformations convergence study Results show that there is a convergence arround 15,3 Mpa and a deformation about 1.46 mm. In this case the security factor rises to 4 so we could reduce the thinkness arround 2mm. There are other factors to have into account such as a shock from inside or ouside, vibrations, accelerations or the manipulation during the assembly process that could compromise the crew s security. Because of this we will accept 5mm as a good thikness. Figure 3: Study results 7

8 The flat surface deformation is produced mainly by thermal differential and we have to consider that if we adjust the hole to the screw a stress concentration will appear during the contraction. In order to avoid that, we will dimension a gap between the hole and the passing screw so that can absorb the relative contraction between the inner frame and the polycarbonate window. Results from the thermal simulation in the metallic frame shows that there is a contraction about 0.5 mm in the screw area so the relative distance will be about 1mm. The solution will be to mechanize a superior metric hole from 5 to 7mm in order to absorb that dilatation P-0040 simulation In that case we will simulate the inner window fixing the upper surface in one direction because although the adhesive used for that case doesn t allow deformations in the X direction the outer window will contract in the same way so its build in the same material and contour conditions are very similar. Again we will mesh as a revolution model applying pressure and thermal loads from 25ºC to - 70ºC. The supposed pressure differential will be about 1 bar. Meshing: Mesh control is required because stresses are distributed non-uniformly so we will refine the mesh in the radius area and near the external surfaces. Tipo de malla Shell Meshing type Standard shell Meshing size mm Tolerance mm Nodes number Elements Table 3: Shell properties 8

9 Figure 4: 0002-P-0040 meshing Results: Figure 5: 0002-P-0040 Stresses 9

10 Figure 6: 0002-P-0040 deformations Meshing size Max. stress [Mpa] Max. deformations [mm] , ,863 13, , Results obtained from the convergence study show that stresses are around 13.4 Mpa and deformation about 1.23mm. Again we are oversizing our model but in order to obtain low deformations and unify material thickness we will approve this geometry. 10

11 P-0038 simulation In the case of the inner frame results show that it is oversized but we will approve its design for construction and sealing conditions. In this case it is important to perform a thermal study in order to know the maximum dilatations when temperature decreases. Contour restrictions: We will restrict movement in the normal direction of the contact area Meshing: This model is simplified as a revolution model and with shell mesh type. In this case we won t apply a meshing control so that all the regions are affected almost in the same way. Meshing type Meshing size Tolerance Standard shell mm mm Nodes number Elements 4887 Table 4: Meshing properties Figure 7: Inner frame mesh Results: Results show that at the furthest point contraction will be about 0,55mm and 0,4mm at the closest point to the center. 11

Figure 8: inner frame contraction We will check the accuracy with a convergence study: Meshing size Max contraction [mm] 0.5 0.549 0.4 0.55 0.3 0.551 0.2 0.551 0.1 0.5512 0.066 0.

12 Figure 8: inner frame contraction We will check the accuracy with a convergence study: Meshing size Max contraction [mm] Table 5: Thermal converfence study 0,552 Max contraction [mm] 0,551 0,55 0,549 0,548 Max contraction [mm] 0,547 0,5 0,4 0,3 0,2 0,1 0,066 The different iterations converge to a result so we will approve this simulation. 12

13 3. Entry study In this study are involved the polycarbonate dome, the inner and outer frame but the most critical part will be the inner frame because depending on the contractions produced by cold there is a risk that a pressure loss appear. The employed materials will be aluminum 6082 T6 for both frames and polycarbonate makrolon UV from Bayer (see annexes for more info) P-0016 simulation Pressures differential will be applied inside to outside the dome with a 0.1 Mpa distribution and a temperature differential from 25ºC to -70ºC. Meshing: Figure 9: Pressure distribution A meshing control is applied around the maximum stress concentration surfaces with the following properties: Meshing type Standard shell Meshing size mm Tolerance mm Nodes number Elements Table 6: 0002-P-0016 meshing 13

concentration is around the radius with a maximum value of 21.

14 Figure 10: Meshing control Results: Figure 11: 0002-P-0016 stress graph Results reveal that the maximum stress concentration is around the radius with a maximum value of 21.8Mpa and providing a SF of 2.98, safe enough to endure the outer conditions. 14

15 Figure 12: Entry deformations Regarding deformations we can conclude that 0,36mm is an acceptable value that won t introduce special stress concentration due to the different gaps presented during the design stage P-0017 Simulation The force that stands the inner frame is defined by the pressure differential transmitted in the contact región with the polycarbonate dome and restrictions. Meshing: It has been applied a meshing control around the most critical region. The following table describes the meshing properties and its distribution: Meshing type Standard shell Meshing size mm Tolerance mm Nodes number Elements 5276 Table 7: Inner frame meshing properties 15

Figure 13: Inner frame control meshing Results: All the stresses are located at the end of the contact area but are not significant values. Regarding deformations we achieve a 0.7mm contraction.

16 Figure 13: Inner frame control meshing Results: All the stresses are located at the end of the contact area but are not significant values. Regarding deformations we achieve a 0.7mm contraction. The joint housing is a critical region because it provides sealing for the interior of the capsule. The pod s frame is also made of aluminum and we can consider that a contraction will also appear with a relative increment distance between the inner frame and the pod s frame equal to 0. For that reason in this stage we will approve its design but it won t be completely validated until a real and cold test is performed. Meshing size Mpa 0, ,396 0, ,49 0, ,53 0, ,521 0, ,531 Table 8: Convergence study 80,55 80,5 80,45 80,4 80,35 80,3 Mpa Mpa Figure 14: Convergence graph 16

17 Figure 15: Inner frame stresses P-0015 simulation Figure 16: Inner frame contractions The objectives of this study are two: the first one is verifying the thickness of the plate and the second one is to find out the dilatations on the holes in order to design a hole that doesn t introduce tensional stresses. Meshing We will apply a meshing control in the outer surfaces where stresses are higher. The following table resumes its properties: Meshing type Standard shell Mesh control Yes Meshing size mm Tolerance mm Nodes number Elements Table 9: Outer frame meshing properties 17

Figure 17: Outer frame meshing distribution Results: The maximum stress concentration is in the contact region through the screws head but it is shown that stresses are distributed along the whole

18 Figure 17: Outer frame meshing distribution Results: The maximum stress concentration is in the contact region through the screws head but it is shown that stresses are distributed along the whole frame. The maximum value is around 140 Mpa so we will approve its geometry. Figure 18: Outer frame Stress results Regarding deformations, there is a critical deformation of 1.006mm in the screw hole so we shall take into account that the hole have to be at least two metrics bigger than the screw in order to avoid contact during contraction. The screw won t contract in the same way because it is glued to a carbon fiber material with different expansion coefficient. Figure 19: Outer frame contraction 18

19 4. Little window simulation This study is performed in order to know the stresses that affect the smallest window. The thickness has been chosen before during the design of the average window and as commented in the memory the same thickness will be selected with the aim of optimizing costs. Again the inputs will be defined as cold conditions from 25ºC to -70ºC and pressure differential of 1 bar. Mesh: P-0020 simulation A control mesh has been applied around the most critical surfaces. Restrictions are defined limiting the upper surface of the polycarbonate dome in the vertical direction. Meshing properties are defined as: Meshing type Standard shell Meshing size mm Tolerance mm Nodes number Elements Table 10: Oouter window meshing properties Table 11: Outer window meshing distribution Results: 19

20 Results show maximum stress around the radius surface with a top value of 13.8 Mpa. This one is slightly less than the average window because the area that supports the pressure differential is also decreased so we can conclude that results are consistent. Figure 20: Outer window stresses Deformation study reveals that the maximum contraction is valued at 1.66mm and taking into account the contraction of the peripheral elements it can be confirmed that the holes can be dimensioned two metrics bigger than the screw. Figure 21: Outer window deformations 20

4.2. 0002-P-0004 simulation In this case, I have followed the same contour conditions as the 0002-P-0038 part explained above.

0281664 mm Nodes number 19037 Elements 8794 Table 12: Meshing properties Results: Figure 22: Inner frame meshing properties Again, results

21 P-0004 simulation In this case, I have followed the same contour conditions as the 0002-P-0038 part explained above. Meshing type Standard shell Meshing size mm Tolerance mm Nodes number Elements 8794 Table 12: Meshing properties Results: Figure 22: Inner frame meshing properties Again, results show that there is a big SF but for constructive reasons it will be approved. Table 13: Inner frame stresses Deformations are produced mainly by the cold conditions and with a maximum value of 0,5 mm. Table 14: Inner frame deformations 21

22 5. Conditions table The table below show the condition variation inside and outside the capsule as it rises. It is also shown the differential vacuum gauge input. Altitude (m) Pressure (Pa) Temperature (K) Air density (kg/m^3) minibloon external pressure (bar) Input (0 10)[V] minibloon windows internal layer pressure (bar) ,15 1, , , , , ,9 1, , , , , ,65 1, , , , , ,4 1, , , , , ,15 1, , , , , ,9 0, , , , , ,65 0, , , , , ,4 0, , , , , ,15 0, , , , , ,9 0, , , , , ,65 0, , , , , ,4 0, , , , , ,15 0, , , , , ,9 0, , , , , ,65 0, , , , , ,4 0, , , , , ,15 0, , , , , ,9 0, , , , , ,65 0, , , , , ,4 0, , , , , ,15 0, , , , , ,9 0, , , , , ,65 0, , , , , ,65 0, , , , , ,65 0, , , , , ,65 0, , , , , ,65 0, , , , , ,65 0, , , , , ,65 0, , , , , ,65 0, , , , , ,65 0, , , , , ,65 0, , , , , ,65 0, , , , , ,65 0, , , , , ,65 0, , , , , ,65 0, , , ,

23 , ,65 0, , , , , ,65 0, , , , , ,65 0, , , , , ,65 0, , , , , ,65 0, , , , , ,15 0, , , , , ,65 0, , , , , ,15 0, , , , , ,65 0, , , , , ,15 0, , , , , ,65 0, , , , , ,15 0, , , , , ,65 0, , , , , ,15 0, , , , , ,65 0, , , , , ,15 0, , , , , ,65 0, , , , , ,15 0, , , , , ,65 0, , , , , ,15 0, , , , , ,65 0, , , , , ,15 0, , , , , ,65 0, , , , , ,15 0, , , , , ,65 0, , , , , ,15 0, , , , , ,65 0, , , , , ,15 0, , , , , ,65 0, , , , , ,05 0, , , , , ,45 0, , , , , ,85 0, , , , , ,25 0, , , , , ,65 0, , , , , ,05 0, , , , , ,45 0, , , , , ,85 0, , , , Table 15: Flying conditions table 23

24 6. Catalogues In the following pages are shown the different pages of the catalogues employed for the development of this project. 24

25 Bayer Makrolon UV 25

26 26

27 Inserts catalogue: 27

28 28

29 29

30 30

Coupled Analysis of FSI

Coupled Analysis of FSI Qin Yin Fan Oct. 11, 2008 Important Key Words Fluid Structure Interface = FSI Computational Fluid Dynamics = CFD Pressure Displacement Analysis = PDA Thermal Stress Analysis = TSA