Structural Analysis: LHC Magnet Collar

Analyst: Rudy Alforque, 10/30/96
E-Mail: rudy@bnl.gov

I. General

The coil pack of the LHC superconducting magnet that will be built here at BNL will be a collared construction as in the old SSC magnets, and the Rhic DX magnets.

II. FEM Model:

A linear, static 2-D finite element structural analysis of the central collar was performed using ANSYS REV5.2. The LHC central collar has the following geometry: Inner Radius, 2 in., which corresponds to a coil outer radius of 50mm; A study was made with two collar thicknesses, i.e. 15mm, and 20mm.

Also, the relevant material properties used in the model were as follow: Young's Modulus, 30x10⁶ psi, and Poisson's ratio, 0.29. The thickness of the coil pack was also given to be 10 mm.

A single plate model was generated with quadrilateral, 4-node plane stress elements (Plane42). The applied loads and boundary conditions are described below.

III. Loads:

The pressure load on the inner surface of the collar was 2400 psi which corresponds to a coil compression of 12,000 psi. This is derived from the assumption that the coil pack is fully circular and obeys the simple hoop stress equation for thin cylinders, S = PR/t, where S is the prescribed compressive stress on the coil pack, R is outer radius of the coil, 50 mm, and t = coil thickness, 10 mm.

IV. Boundary conditions:

For this single plate model, it is assumed that the surface of the plate that rests on the key are restrained vertically since the neighboring plate actually exerts that reactive force, keeping the key restrained in the y-direction.

Furthermore, the corresponding nodes at the ends of the plate that push against each other are related by constraint equations along the x-axis. Similarly, the nodes at the tack welds are also related by constraint equations.

V. Results:

Graphical Displays of the Model:

Fig.1: 20 mm Collar: Ux, Deformation along the x-axis

Fig.1: 20 mm Collar: Uy, Deformation along the y-axis

Fig.1: 20 mm Collar: SI, Tresca criterion, or stress intensity distribution

Fig.1: 15 mm Collar: Ux, Deformation along the x-axis

Fig.1: 15 mm Collar: Uy, Deformation along the y-axis

Fig.1: 15 mm Collar: SI, Tresca criterion, or stress intensity distribution