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Repositorio de la Universidad de Zaragoza – Zaguan http://zaguan.unizar.es Proyecto Fin de Carrera DISEÑO Y CÁLCULO DE UNA ESTRUCTURA REFORZADA PARA LA CABINA DE UN CAMIÓN LIGERO DE TRANSPORTE Autor/es Marcos Cervantes Carcas Director/es Luís Gracia Villa Escuela de Ingeniería y Arquitectura (EINA) 2014 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 2 PFC Ingeniería Industrial DISEÑO Y CÁLCULO DE UNA ESTRUCTURA REFORZADA PARA LA CABINA DE UN CAMIÓN LIGERO DE TRANSPORTE SUMMARY The target of this project is to develop a new structure for a light commercial vehicle interior cabin. It is a real design, based in a vehicle accident when a tree collapsed into the cabin, and killed the two occupants. The target is to add a reinforced structure for the interior of the cabin, and incorporate new resistant conditions so that the new cabin could be under hard conditions, similar to the conditions that happened in the accident in such a way that guarantee the safety of the occupants. It will be done different design proposals and simulations of each one for every load case by using finite element method (FEM). This is a research project in which it has been done analytic calculations, based on the information from the site accident in order to estimate the impact load based on energy balance. The company provided a similar cabin so we could design the cabin, and get all information we could need from the garage. It has been done several calculations, a general one with SOLIDWORKS, and also a specific one from the top part with NASTRAN PATRAN. All the design was done with SOLIDWORKS, the background, truck and reinforced structure. We well try to find the balance between aesthetics, price, and resistance and easy to manufacture because this design is pretended to be incorporated in the new vehicle range mentioned on this project. I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 3 PFC Ingeniería Industrial 1. TABLE OF CONTENTS 1. TABLE OF CONTENTS..............................................................................................................3 3. BACKGROUND.......................................................................................................................4 2. AIM........................................................................................................................................5 4. CABIN SECIFICATIONS...........................................................................................................6 5. PROBLEM DESCRIPTION.........................................................................................................10 5.1 ACCIDENT BACKGROUND................................................................................10 5.2 MANUAL CALCULATION AND LOAD OBTAINED...............................................13 6. MODEL RESEARCH................................................................................................................19 7. FINAL MODEL........................................................................................................................23 7.1 GEOMETRY DESCRIPTION..........................................................................23 7.2 CABIN DESIGN............................................................................................33 7.3 ACCIDENT SITE...........................................................................................42 8. FEM SOLIDWORKS.................................................................................................................47 8.1 FEM DESCRIPTION.....................................................................................47 8.2 MATERIAL SPECIFICATIONS.......................................................................54 8.3 BOUNDARY CNDITIONS.............................................................................55 8.4 LOADS CASES.............................................................................................57 8.5 RESULTS.....................................................................................................61 9. TOP PART ANALYSIS ..............................................................................................................79 9.1 GEOMETRY DESCRIPTION..........................................................................77 9.2 MESH DESCRIPTION...................................................................................79 9.3 LOAD AND BOUNDARY CONDITIONS.........................................................83 9.4 RESUTS.......................................................................................................85 10. ASSEMBLY...........................................................................................................................91 11. STANDARDS.........................................................................................................................97 12. CONCLUSIONS.....................................................................................................................98 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 4 PFC Ingeniería Industrial 2. BACKGROUND The reason for this project is because an accident happened on the cabin of a Toyota, when a 30 meters tree collapsed on the cabin. Two of the occupants of the cabin were killed and the goal of the project is to design a structure strong enough to avoid such an event. The project has been ordered by the Victoria Department of Environment to our company, Enkelam and Associates, who is the responsible of the design of the new structure. In the Figure 1 we can see the result of the cabin, after the tree collapsed on the truck. Figure 1.Cabin after accident I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 5 PFC Ingeniería Industrial 3. AIM The object of this project is to achieve a reinforced structure for the interior of the cabin for truck ISUZU. This project is commissioned by the Environment Department, Victoria. The main goal is to increase the strength of the cabin, getting an interior structure strong enough to avoid future accidents. We made different designs until find the most viable one, an average between price, strength and aesthetic. Our company bought an ISUZU cabin, in this way we can always check in our facility all that we need, as it is a investigation project, and we need to check the relevant dimensions of the cabin. We can see in Figure 2 see our cabin, the survival volume and the impact position (green cylinder). Figure 2. Survival volume and impact load I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 6 PFC Ingeniería Industrial 4. CABIN SPECIFICATION Below there are the specifications of our cabin, as the main details that we have been using within the investigation stage. The ISUZU 300 and 450 cabins are identical. Figure 3. Isuzu specifications 1 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 7 PFC Ingeniería Industrial Figure 4. Isuzu specifications 2 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 8 PFC Ingeniería Industrial Figure 5. Isuzu specifications 3 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 9 PFC Ingeniería Industrial Figure 6. Isuzu specifications 4 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 16 PFC Ingeniería Industrial Ra = Rb = Fstat/2 σy= 250 MPa M = σy*Zmin = 10080x250 Fstat = (10080 x 250 x 8) / 710 = 28394 N = 2894 Kg Max. deflection at centre: - (M*L^3) / (192*E*I) = 28940*0710^3 / 192*978*10^3*200 = -0.3mm Note: Ixx is too large. Unsupported roof. Spam gives false indication. Recalculate Ixx. Y = 114293 – 110*(750x1.1)/1182.5-825 = 66cm Ixx = (1.1*110^3)/12 + 121*11^2 + 1.1*20^3/12 + 22*56^2 + 22*46^2 + (1.1*15^3)/12 + 16.5*38^2 + 22*28^2 + 99*24^2 + (1.1*45^3)/12 + (1.1*60^3)/12 = 371*10^3 mm3 Zxx min = 371*10^3/66 = 5621 mm^3 Zxx max = 371*10^3 / 44 = 8432 mm^3 σy*Zmin = M = 250*5621 = 1.4*10^6 Nmm Fstat = 250*5621*8/750 = 15833 N = 1614 Kg I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 17 PFC Ingeniería Industrial Deflection -WL^3/192EI = 15833*750 / 192*371*10^3*200*10^3 = -0.4mm A static force of 833 N will cause a deflection of 0.4mm A point force in the centre = Fpoint = (1.4*10^6*8)/860 = 13072 N (1334 Kg) Deflection = (-0.4*13072*860^3)/15833*710^3 = 0.59 Impact force S’ = S * ((Wt/Wc)*(3Wt/(3Wt + Wc)))^1/2 Wt = Tree Mass = 1520 Kg Wc = Cabin Mass + Front gear = F A load = 2500 Kg. S’ = 250 * ((1520/2500)*(3*1520/(3*1520+ 2500)))^1/2= 157 MPa ( No Ok) COSNIDER ASMS OF CABIN ONLY S’ = 250 * ((1520/700)*(3*1520/(3*1520+ 700)))^1/2= 157 MPa ( Could be OK) CONSIDER Wc=Wt Then S’ = S * (1 + (1 + (2h/e)); h= 12m E = SI/E I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 18 PFC Ingeniería Industrial S’ = 250 * (1 + (1 + (2*12000/464) = 2075 MPa (High, but possible. Use it!) The calculated force = 1317 Kg It will be with a factor of 8.3 = 1317x2075/250 = 10931 Kg From the manual calculations, we deduce that the impact force is 10932 Kg, almost 11 tons. We have checked that we can use 75x50x3 box section beams, but these calculations are only an approximation. Later we will see that with SOLIDWORKS, the stresses in the joints are really high, so we will have to change their dimensions and also reinforce the beams . The impact load is distributed at the top of the structure, and we will only consider static and linear calculations. I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 19 PFC Ingeniería Industrial 6. MODEL RESEARCH After the hand calculation, we designed a sketch which is the starting point for the rest of the model design. Figure 12. Sketch 1 Figure 13. Sketch 2 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 20 PFC Ingeniería Industrial Before designing, we will try to find an aesthetic model, but we have to check the stresses first. Figure 14. Sketch 3 Figure 15. Sketch 4 That model was the first idea, because it is a small model, aesthetic, economic and easy to assemble. An important point was to retain occupant space within the cabin, and the comfort inside the cabin is an important point. The problem of this model were the stresses, really high, and not sustainable. Figure 16 a. Sketch 5 Figure 16 b. Sketch 6 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 21 PFC Ingeniería Industrial Below, there is a basic analysis where we can see that the stresses are unacceptable Figure 17 a. Basic calculation 1 Figure 17 b. Basic calculation 2 The next idea was using circular section, but we had the same problem as before, the appearance was better but the stresses obtained are unacceptable. Figure 17 a. Sketch 7 Figure 17 b. Sketch 8 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 22 PFC Ingeniería Industrial Here is a picture from SolidWorks of the circular section design. Figure 18. Sketch From these designs we finally decided our model, as we can see in the next pages. These initial determinations helped us to verify the stresses, and decide which the acceptable model is considering strength, price and aesthetics, always falling under the max yield strength of the material, 355 MPa. I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 23 PFC Ingeniería Industrial 7. FINAL MODEL 7.1 Geometry description After several designs, we finally settle down our final model. We chose box section beams, reinforced in the critical points. There are three different assemblies in this model, the top assembly, right side assembly, left side assembly. The top assembly is made of four 150x60x2 box section beams welded to a 100x60x2 box section beam. The central beam is made of welded plates, because it is the only way to reinforce the center of the beam, otherwise the deformation would be unacceptable. Figure 19. Top part Below there is the central beam, 100x60x2, with four gussets, one just in the middle, two in both sides, and other two in the connection between the 150x60x2 beam. Figure 20. 150x60x2 beam I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 24 PFC Ingeniería Industrial Figure 21. Top part Figure 22. Connection 150x60x2 beam with central beam. Reinforces. Another important point is the connection between the top part and the left and right sides for assembly. It was also an important consideration for the comfort of the cabin occupants, so we considered a top plate welded to the top part of the 150x60x2 beam. That part is bolted to both sides. Figure 23. Connection I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 25 PFC Ingeniería Industrial Figure 24. Detail connection Views of the top attachment. Figure 25. Top part views The sides are symmetrical. This assembly is made of three box section 100x60x2. The top beam is made of welded plates, and it is necessary to have an intermediate reinforcement, and also to conform to the. I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 32 PFC Ingeniería Industrial Figure 39. Final model views. I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 33 PFC Ingeniería Industrial 7.2 Cabin design For an accurate design of our model, it was necessary that with an approximate design of the cabin ISUZU. Each part was provided with the real measures, using surfaces in Solidworks. The front and rear cabin supports one down first. Figure 40. Front detail 1 Figure 41. Front detail 2 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 34 PFC Ingeniería Industrial Figure 42. Back detail 1 Figure 43. Back detail 2 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 35 PFC Ingeniería Industrial Here we can see the three main elements which the structure is screwed. Figure 44. Support detail . Figure 45. Back support I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 36 PFC Ingeniería Industrial Figure 46. Front support Figure 47. Supports and chassis. I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 37 PFC Ingeniería Industrial Figure 48. Ground Using these elements, and the rest of the cabin, just an initial design was established with the real measures. Design details are shown below. Figure 49. Cabin design 1 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 38 PFC Ingeniería Industrial Figure 50. Cabin design 2 Figure 51. Cabin design 3 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 39 PFC Ingeniería Industrial Figure 52. Cabin design 4 Figure 53. Cabin design 4 . I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 40 PFC Ingeniería Industrial Figure 54. Cabin design 5 Figure 55. Cabin design 6 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 41 PFC Ingeniería Industrial Figure 56. Final model I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 48 PFC Ingeniería Industrial Figure 66. Top Mesh view Figure 67. Back Mesh view I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 49 PFC Ingeniería Industrial Figure 68. Front Mesh view An important aspect is the mesh continuity. We repeated the meshing process several times until we checked that the mesh was continuous, and each filled. Below is shown the continuity of the mesh. Figure 69. Mesh detail Back support 1 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 50 PFC Ingeniería Industrial Figure 70. Mesh detail Back support 2 Figure 71. Mesh detail Back support 3 Figure 72. Mesh detail Back support 4 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 51 PFC Ingeniería Industrial Figure 73. Top connection mesh detail . Back Figure 74. Top connection mesh detail . Middle 1 Figure 75. Top connections mesh detail . Middle 2 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 52 PFC Ingeniería Industrial Figure 76. Top connections mesh detail . Front 1 Figure 77. Top connections mesh detail. Front 2 Figure 78. Front support mesh detail I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 53 PFC Ingeniería Industrial As we can see, there is continuity in all models. We have used a standard mesh, triangular elements, length 0.0181963m. Figure 79. Element length detail. I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 54 PFC Ingeniería Industrial 8.2 Material specifications We have used for the whole model S 355 JR steel. The average minimum yield for this material is 355 N/mm², hence the name S355. It has a 7850Kg/m3 density. Analysis Carbon 0.20% max Phosphorous 0.025% max Manganese 1.60% max Sulphur 0.025% max Silicon 0.55% max I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 55 PFC Ingeniería Industrial 8.3 Boundary conditions There are three different parts where our model is restricted. In each part, displacement and twist are both restricted in X, Y and Z direction. Below we can see the three different restrictions. Figure 80 a. Front restriction Figure 80 b. Front restriction detail Figure 81 a. Back restriction 1 Figure 81 b. Back restriction detail 1 Figure 81 c. back restriction 2 Figure 81 d. back restriction detail I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 56 PFC Ingeniería Industrial Figure 82. Restrictions 1 Figure 83. Restrictions 2 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 57 PFC Ingeniería Industrial 8.4 Loads cases The impact force obtained is about 10932 Kg (we have considered an impact load of 110000N). There are four different load cases depending where the tree fall. Load case 1 The tree impact exactly from one of the sides, an impact in the three top beams, the load is equality distributed in all of them. Figure 84. Load case 1. ISO Figure 85. Load case 1. Top I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 64 PFC Ingeniería Industrial Displacements Figure 96. Displacements Deformed Figure 97. Deformed I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 65 PFC Ingeniería Industrial Load case 2 Stresses Figure 98. Von Mises Stresses. ISO View Clipping Figure 99 a . Clip 1 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 66 PFC Ingeniería Industrial Figure 99 b. Clip 2 Figure 99 d. Clip 3 Figure 99 d. Clip 4 Figure 99 e. Clip 5 Supports Figure 100 a. Front support Figure 100 b. Back support Connections I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 67 PFC Ingeniería Industrial Figure 101 a. Connection 1 Figure 101 b. Connection 2 Figure 101 c. Connection 3 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 68 PFC Ingeniería Industrial Displacements Figure 102. Displacements Deformed Figure 103. Deformed I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 69 PFC Ingeniería Industrial Load case 3 Stresses Figure 104. Von Mises Stresses. ISO View Clipping Figure 105 a. Clip 1 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 70 PFC Ingeniería Industrial Figure 106 b. Clip 2 Figure 106 c. Clip 3 Figure 106 d. Clip 4 Figure 106 e. Clip 5 Supports Figure 107 a. Front support Figure 107 b . Back supports I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 71 PFC Ingeniería Industrial Connections Figure 108 a. Connection 1 Figure 108 b. Connection 2 Figure 108 c. Connection 3 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 72 PFC Ingeniería Industrial Displacements Figure 109. Displacements Deformed Figure 110. Deformed 1 Figure 110 b. Deformed 2 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 73 PFC Ingeniería Industrial Load case 4 Stresses Figure 111. Von Misses Stresses. ISO View Clipping Figure 112 a. Clip 1 Figure 112 b. Clip 2 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 80 PFC Ingeniería Industrial Figure 125. Hidden line mesh Figure 126. Shaded mesh Figure 127. Element shrink mesh I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 81 PFC Ingeniería Industrial Mesh joint details below. Figure 128. Mesh detail 1 Figure 129. Mesh detail 2 Figure 130. Mesh detail 3 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 82 PFC Ingeniería Industrial Figure 131. Mesh detail 4 Figure 132. Wireframe mesh detail 1 Figure 133. wireframe detail 2 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 83 PFC Ingeniería Industrial 9.3 Loads and boundary conditions We applied a total load about 110000N, as follows Figure 134. Iso view load Figure 135. Front view load We restricted the displacement in X, Y and Z, and also the rotation. Figure 136. Iso view boundary restrictions I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 84 PFC Ingeniería Industrial Figure 137. Restriction detail 1 Figure 138. Restriction detail 2 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 85 PFC Ingeniería Industrial 9.4 Results Stresses Figure 139. Max Von Misses stresses 16.1 MPa Figure 139. Detail Max Von Misses stresses 1 Figure 140. Detail Max Von Misses stresses 2 I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 86 PFC Ingeniería Industrial Figure 141. Detail Max Von Misses stresses 3 Figure 142 Detail Max Von Misses stresses 3 Figure 143. Detail Max Von Misses stresses continuous I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 87 PFC Ingeniería Industrial Figure 144. ISO view Max Von Misses stresses Constrain forces Figure 145. Constraint forces I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 88 PFC Ingeniería Industrial Figure 146. Vector constraint forces .Back Support Figure 147. Vector constraint forces .Front Support I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 89 PFC Ingeniería Industrial Deformation Figure 148. Displacements ISO view (9.48mm) Figure 149. Displacement ISO view continuous Figure 150. Displacements on deformed structure I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 96 PFC Ingeniería Industrial Figure 165. Left side and top side bolted Figure 166. Final assembly I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 97 PFC Ingeniería Industrial 11. STANDARDS - AS/NZS 1252 High strength steel bolts with associated nuts and washers for structural engineering - AS/NZS 3679.2 Structural steel. Welded I sections - AS/NZS 4600 Cold-formed steel structures - AS 4100 Steel structures I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 98 PFC Ingeniería Industrial 12. CONCLUSIONS The aim of this project is to ensure the safety of the occupants in the cabin. The maximum deformation allowed in our model is 40mm, so all calculations had to be under this value. We have been working with two different software's, SOLIDWORKS, and NASTRAN PATRAN. The first one has been very useful for the design and to have a main idea about what is happening in our model. The stresses obtained with this software are not accurate enough, but nevertheless, we can see that the stresses are not over 335 MPa, and also the displacements obtained are less than 40mm. The maximum stresses obtained with that program are under 355 Mpa, and just in some points the stresses are bigger, but it is something that we don't have to worry about. Figure 167. SOLIDWORKS stresses The maximum displacement obtained is 9.25 mm, in the case that the load collapsed into the cabin from one side. Figure 168. SOLIDWORKS displacements. Side load I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 99 PFC Ingeniería Industrial The displacement is larger if we consider that the load falls on the front part. It is about 13.13mm. Figure 169. SOLIDWORKS displacements. Front load Those calculations have been made with SOLIDWORKS, and we can see the displacements and the stresses obtained are correct. The second calculation was the top part, as it is such an important part in this model. It was important to check the displacements with an accurate program. We worked with NASTRAN PATRAN. As we can see, the main stresses obtained by Von Misses are 16.1 MPa. I + D project Design and calculation of a reinforced structure for a light commercial vehicle (LCV) 100 PFC Ingeniería Industrial And the displacements obtained are basically equal to the displacements obtained with SOLIDWORKS. With NASTRAN PATRAN the maximum displacement obtained was 9.48mm In conclusion, it can be said, that the results satisfy the specifications that were required.