Space Frame Design at Station 2 for PHENIX Muon Detector

Los
Alamos National Laboratory Memorandum

UPDATED

SUBJECT: Space Frame Design at Station 2 for PHENIX Muon Detector

Design Considerations:

The basic space frame configuration was formed by the configuration of muon chambers and restricted by octagonal lampshade that has been designed at LLNL. The geometry should be simple and modular for low cost. Instalability, maintainability and reparability for all muon chambers have been highly considered.

Material Selection:

The comparisons have been done on a space frame with 75mmX50mm tube having 3.175mm wall thickness. After static analysis on the same structure, the maximum displacements on AL_6061 structure is 1.996mm, but on the SST it is 0.399mm. After then all studies, structure analysis and calculations were based on stainless steel space frame.

Decision for Beam Section Configuration:

Analytical solution on several types of beam section has been done. The maximum displacements and the weight per meter are shown in Table 1.

Beam Size (mm)	50x50x3.175 Tubing	75x50x3.175 Tubing	75x30x3.175 Tubing	75x20 Plate
Space Frame Max. Disp.(mm)	0.90	0.363	0.527	0.374
Weight (Kg/m)	4.75	6.03	5.01	12

TABLE 1. MAX. DISP. vs. Beam Size & Weight

After a series of calculations and comparisons, the stainless steel tubing with 75mmX50mm cross section and 3.175mm wall thickness has been accepted as the space frame material to support the muon chambers at station 2.

Structural Analysis Summary:

The analysis effort of the muon space frame structure focused on evaluating its stability and optimizing its design.

A finite element model (FEM) of the structure was constructed using the COSMOS/M finite element package. Considering the muon chambers themselves, the stiffness has to be associated with the space frame. Thus, the finite element model of the structure was constructed with the muon chambers and the space frame together. The structure was modeled using three-dimensional beam elements for the radialized longerons and cross bracing. The support tubing and its flanges at both of the ends were modeled using a 4-node quadrilateral thin shell element. Considering the actual assembly structure of muon arm station 2, the stainless steel space frame has to be tightly connected with the AL-6061 muon chamber frame, and the wires and foils do not carry a lot of stiffness. So the method of Multiple Constraints with Composite Beam was used to model the structure is more actual and precise for performance of structure analysis. A series of calculations for properties of the composite beams with different sections and materials were done by hands as the input for the Finite Element Analysis.

The result for the maximum displacement is 0.363mm as Table 1 shows. The first five natural frequencies were calculated using FEA and are shown in Table 2.

Mode #	1	2	3	4	5
Freq. (Hz)	7.940	12.568	16.580	25.434	27.619

Table 2. Frequency Results for Composite Beam Modeling (Shown in Figures 2-6)

The dynamic analysis on this structure will be following soon after we get the force functions in the Detector operating environment.

cy: R. Martin, ESA-DE, MS H821
W. Sondheim, P-25, MSH846
Z. Chen, ESA-DE, MS H821
ESA-DE File

cy:	R. Martin, ESA-DE, MS H821
	W. Sondheim, P-25, MSH846
	Z. Chen, ESA-DE, MS H821
	ESA-DE File

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