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Author(s) - Leonardo González López
Author(s) - Leonardo González López
ET-0043A-25
Study of silicon spring blades for a novel cryogenic test-mass suspension system for the Einstein Telescope Gravitational Wave Observatory
Leonardo González López, Nelson Leon, Fabian Peña Arellano, Riccardo DeSalvo, Harry Themann· Scientific/Technical note· Released 16:17, Wednesday the 19th of February, 2025
Abstract
This report complements a broader analysis of a novel cryogenic suspension system incorporating blade springs. These blades introduce vertical compliance in a test-mass suspension system with flexures and suspension beams under compression and tension respectively, compensating for manufacturing variations, as well as incorporating a means of providing vertical thermal noise attenuation.
Designed with an isosceles triangular shape for uniform bending, the blades attach at an angle, with a pre-bent tip so that the area on which the load is supported lays horizontal. Through FEM simulations using Ansys, we identified a configuration in which we can base our future studies, with a 10.5 mm thickness, a 13.63 m curvature radius, and a base tilt of 12.453 mrad, ensuring a maximum surface tensional stress of 52.69 MPa—maintaining a safety factor close to 3.
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Abstract - This technical report serves as a complimentary companion to a more comprehensive document of the first conceptual analysis of a novel cryogenic suspension system, which incorporates horizontal spring blades. The spring blades are part of a test-mass suspension system that uses an assembly of flexures and suspension beams operating in compression and tension respectively. The blades address the necessity for vertical compliance that the beams lack in order to compensate any manufacturing differences among the four beams that hold the mirror. The spring blades are designed with an isosceles triangular shape, optimal for uniform bending and stress distribution. The wider end attaches to a holder at an angle, so the narrow tip of the blade is horizontal after bending in response to supporting the load. The tip is equipped with a straight extension used to pre-bend the blades during assembly. In order to minimize tensional stress at the base and the tip, these sections are thicker. The ANSYS finite element method software was used to simulate the stress distribution and find the best configuration, maintaining a maximum surface tensional stress below 55 MPa. With our finding and a few of the discussed optimization strategies, a conservative case to consider is one with a thickness of 10.5 mm, with a radius of curvature of 12.65 m, a base tilt 12.453 mrad in which the sag of the tip is 1.3 mm when loaded. The upper face experiences an almost uniform tensional stress, with a maximum value of 52.69 MPa. The overall maximum was estimated with Ansys to be 79.55 MPa, occurring along the fillets at the transitions from the thinner to the thicker sections, maintaining a safety factor close to 3 considering the tensional breaking strength of 165 MPa. Anti-springs with optical sensors and electrostatic actuators may be used to lower the resonance frequency and, thus, provide attenuation of the vertical thermal noise of the seismic attenuation chain. -
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