Subject: STRUCTURAL ANALYSIS OF THE LIFTING DEVICE FOR THE TWO DETECTOR SUPPORTS
Group:Engineering dept. NIKHEF
Date:april 2004
Prepared by:M.J. Kraan
Checked by: C. Snippe, J. Buskop; M. Doets
Project ID:LHCb NIKHEF Document No:MT-VELO 04-02
Cern Safety Code :D1 Lifting equipment CERN EDMS No:466608
TIS Safety Study Report :SSR 469287 Material test certificate :DOMEX 420 MC D
Lifting test Document: RHH8297
PDF document MAIN document / APPENDIX

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.

Introduction

LHCb is one of the four particle physics experiments around the LHC accelerator, which is located at CERN. The LHCb VErtex LOcator (VELO) is one of the subdetectors of the LHCb experiment For installation of the two detector supports is a lifting device designed. Figures below shows the lifting device 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.

Design of the Lifting device

The two main plates of this lifting device, 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.

  • Drawings in PDF Format

    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:

    F1 = 510 / 1100 x 1100 [N] x 2.4 = 1224 N
    F2 = 590 / 1100 x 1100 [N] x 2.4 = 1416 N

    Material data:

    This Lifting device will be made from Steel 47 (1.8905)

      Tensile strengthRm [MPa]min.580
      Yield strengthRp 0.2% [MPa]min. 430
      Young's modulusE [GPa]min.210
      Density[g/cm3].7.85
      Poisons ratio..0.30

    FEA:

    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.

    Lifting plate: to simulate the 'worse case scenario', the first support point 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.
    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 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.

      Finite Element Mesh
      Lifting plate
      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: F1=1224 N / F2=1416 N
      cross plate: F=1416 N
      Type of Solution: Linear Statics
      Units:Length [mm]; Force [N]; Stress/Pressure [Mpa]

    Calculation bolt and sliding axle:

    Sliding Axle:

      Material AISI 304
      Yield strength = 290 N/mm2
      F = 1416 N ; a = 30 mm; d = 12mm

      Bending:
      Shear:
      Total:

    Bolt M6:

      Material AISI 304
      Yield strength = 290 N/mm2
      Force F is divided over 2 M6 bolts: F = 1416/2 = 708 N
      d = 4.7 mm (M6)

      Tension:

    • RESULTS:

    LIFTING PLATE:

      stress
      max. 377 MPa      		detail stressdisplacement
      max. 20.4 mm
      stress
      200Mpa limited      		stress
      150Mpa limited      		stress
      100Mpa limited      		stress
      50Mpa limited
      Buckling mode 1
      factor 8.9      		 Buckling mode 2
      factor 10.3      		 Buckling mode 3
      factor 11.5      		 Buckling mode 4
      factor 14.3

      Strain energy error norm = 1.7%

    CROSS PLATE:

      stress 0 deg.
      max. 90.2 MPa      		stress 30 deg.
      max. 349 MPa      		displacement 0 deg.
      max. 0.25 mm      		displacement 30 deg.
      max. 4.2 mm

      Strain energy error norm = 5.2%

    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).