National Institute for Nuclear Physics and High Energy Physics Kruislaan 409 1098 SJ Amsterdam The Netherlands NIKHEF Reference no.: MT-VELO 04-2 EDMS no: 466608 OF THE LIFTING DEVICE DETECTOR SUPPORTS FOR THE LHCb VERTEX LOCATOR (VELO) M. J. Kraan, C. Snippe, J. Buskop, M. Doets Abstract The structural verification of the 'LHCb VELO detector support' lifting device is the subject of this document. Purpose of these calculations is to investigate stress and stability of this lifting device. This lifting device has to comply with the D1 CERN Code. Numerical analysis was performed with the IDEAS TM finite element analysis software April 2004
Table of Contents 1. Introduction...3 2. General description of the Lifting Device...4 2.1 Design...4 2.2 Material properties...5 2.3 Operational conditions...5 3. Finite Element Analysis...6 3.1 Lifting plate...6 3.2 Cross plate...6 4. FEA results...8 4.1 Lifting plate...8 4.2 Cross plate...10 5. Calculation bolt and sliding axle...12 5.1 Sliding Axle...12 5.2 Bolt M6...12 6. Conclusion...13 APPENDICES A.. All Technical Drawings B.. More FEA results 2
1. Introduction LHCb is one of the four particle physics experiments around the LHC accelerator, which is located at CERN. The LHCb VErtex LOcator (VELO), shown in figure 1.1, is one of the sub detectors of the LHCb experiment Fig 1.1: VELO detector. For installation of the two detector supports a lifting device has been designed. Figure 1.2 shows the lifting device (in yellow) with the two detector supports in front of the vacuum vessel. The scope of this document is to investigate stress and stability of this lifting device. This lifting device has to comply with the D1 CERN Code. Fig 1.2: Lifting device for installation of the two detector supports. 3
2. General description of the Lifting Device 2.1 Design The two main plates of this lifting device (shown in fig. 2.1), so called 'lifting plates', are bolted together with 4 intermediate plates. Between these two lifting plates are two cross plates hanging in capacious slots. On the cross plates are the detector supports mounted. To get a reasonable weight (43 Kg) for handling of this lifting device, all plates are cut with a triangular or circular pattern. Fig 2.1: Lifting device 4
2.2 Material properties This Lifting device will be made from Steel 47 (1.8905): Tensile strength Rm [MPa] Min. 580 Yield strength Rp 0.2% [MPa] Min. 430 Young's modulus E [GPa] Min. 210 Density [g/cm3] 7.85 Poissons ratio 0.30 2.3 Operational conditions The load of the lifting device is determined by the weight of the two detector supports. The weight for each detector support is 1100 N. This weight and the center of gravity is calculated in the 3D modeling software. There are 8 holes to put in a lifting bar for adjusting the center of gravity. A safety factor used in the simulation is 2.4. With a weight (G) of each detector of 1100 N, the load at each lifting point is: F 1 = 510 1100[ N] 2.4= 1224N 1100 F 2 = 590 1100[ N] 2.4= 1416N 1100 Fig 2.2: Center of gravity of a detector support. 5
3. Finite Element Analysis A finite element analysis has been done to verify that the stresses are below the Yield strength, and within the limits defined by the CERN safety code for lifting devices D1. The finite element analysis is done with the finite element analysis module of Ideas TM. 3.1 Lifting plate To simulate the 'worse case scenario', the first support point (see fig 3.1) of the 'lifting plate' is used (largest distance to the cross plates) and the forces are in vertical direction placed on the surface on which the 'cross plates' are. The model is build up with 2D Thin Shell parabolic quadrilateral. A buckling analysis is presented as the stresses in some 'relative thin' sections are compressive. Fig 3.1: FEA model of the lifting plate. 3.2 Cross plate Due to the symmetry of the cross plate, half of the 'cross plate' has been simulated. Two angle directions of the force are analyzed: 0 (vertical) and 30 degrees. This 30 degrees (shown in fig 3.2) is a worse case lifting scenario. Under normal conditions this force will always be vertical. The model is build up with 3D Solid parabolic tetrahedron elements. 6
Fig 3.2: 30 degrees lifting angle. Fig 3.3: FEA model of the cross plate Mesh types: lifting plate: 2D Thin Shell parabolic quadrilateral cross plate: 3D Solid parabolic tetrahedron Safety Factor: 2.4 Load type: Load on surface Weight 1 detector support: 1100 N Load Amplitude: lifting plate: F 1 =1224 N / F 2 =1416 N cross plate: F=1416 N Type of Solution: Linear Statics Units: Length [mm]; Force [N]; Stress/Pressure [Mpa] Table 3.1; summery of FEA properties. 7
4. FEA results 4.1 Lifting plate Fig 4.1: Von Misses stress results. Max. 377 MPa. Fig 4.2: Detail Von Misses stress results. 8
Fig 4.3: Deflection results. Max. 20.4mm. Without safety factor 20.4/2.4=8.5mm Fig 4.4: First buckling mode. Buckling factor = 8.9. Strain energy error norm = 1.7% 9
4.2 Cross plate Fig 4.5: 0 degrees; Von Mises stress results. Max. 90.2 MPa. Fig 4.6: 0 degrees; deflection results. Max. 0.25 mm. 10
Fig 4.7: 30 degrees; Von Mises stress results. Max. 349 MPa. Fig 4.8: 30 degrees; deflection results. Max 4.2 mm. Strain energy error norm = 5.2% 11
5. Calculation bolt and sliding axle Fig 5.1 detail cross plate with the 2 bolts and sliding axle. 5.1 Sliding Axle Material AISI 304 Yield strength = 290 N/mm 2 F = 1416 N ; a = 30 mm; d = 12mm Bending: Shear: σ M F a 1416 30 = = = = 250 N / mm b b 3 3 Wb π d π 12 32 32 τ = F F 1416 12.5 N / mm 2 2 A = π d = π 12 = 4 4 2 2 σ σ τ t?t = b + 3 = 251 N / mm 2 2 2 5.2 Bolt M6 Material AISI 304 Yield strength = 290 N/mm 2 Force F is divided over 2 M6 bolts: F = 1416/2 = 708 N d = 4.7 mm (M6) Tension: σ = F F 708 t 41 N / mm 2 2 A = π d = π 4.7 = 4 4 2 12
6. Conclusion For both lifting parts counts from the stress analysis point of view that the simulation shows an stress level (lifting plate: max. 377 MPa; cross plate max. 349 MPa) below the Yield strength (430 MPa). Deformations on both parts are not critical and can only be a point of discussion for installation reason. For what concerns stability of the lifting plate, the linear buckling analyses shows a comfortable safety margin (buckling mode 1, buckling load factor = 8.9). 13