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Vibration Resistance Calculation Applied to Luminaires

Cost reduction through engineering studies : testing less and better thanks to simulation

PHIMECA carried out a vibration resistance study on behalf of PHILIPS, to ensure compliance with applicable norms and safety standards of great-size light fixtures meant to be set in public premises.

PHIMECA provides turnkey solutions : from the prior design study permitting to spot the product’s possible fragilities up to the setting and completion of compliance tests.

PHILIPS Lighting, global leader in the lighting sector, has called out to PHIMECA to assist in developing their luminaires, and more specifically the lightings’ Heatsinks parts.

PHILIPS has designed a new improved model of heat dissipator aiming for production cost optimization (manufacturing process, weight, materials…). PHIMECA’s mission consisted in checking-up product’s compliance with current norms in terms of mechanical resistance to dynamic stress.

Two types of vibratory stresses have been checked :

  • Sinus vibration of 3g amplitude applied to the luminaire’s fundamental frequency. During this "resistance under resonance" test, 100 000 cycles have been applied.
  • Half-sine impact of amplitude 50g within 11 milliseconds.

To achieve this project’s objectives, PHIMECA took up, turnkey-wise, mechanical design calculation using FEM-type (Finite Element Model) simulation for the whole luminaires and handled the setting and completion of vibratory tests along with a partner laboratory.

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  • 1 : Initial study : identification of a break risk thanks to simulation

First, an engineering phase (CAD) has been carried out to maximize the mechanical tests’ probability to be successful . Lightings were modeled using FEM method in Ansys Workbench to enable application of the dynamic stress to be tested.

Based on available test results history, the numerical model has been recalibrated which allowed us to improve its representativeness. The numerical analysis of impact resistance showed acceptable constraint levels inferior to the material’s elasticity threshold. However, numerical simulation of resistance under resonance lead to identification of an excessive fatigue damage inducing fatigue crack initiation risk.

  • 2 : Re-engineering of the product under FEM

To remedy this issue, PHIMECA adviced to proceed to local reinforcements of the Heatsinks as well as using a different material endorsed with more adequate properties under cyclic stress to achieve better fatigue strength.

  • 3 : New test specification writing

PHIMECA then covered laboratory testing phase set up. A new test specification has been written which which describes the prescribed protocole in detail. This document exhaustively lists up the information necessary to accurate test completion, which are : mounting conditions, tightening torques, constraint levels, testing processes order, accelerometers’ amount and positions, measurement captors...

  • 4 : Test fitting : tool dimensioning calculation for product assembly on the test mean

PHIMECA also handled design and sizing of the parts meant for the luminaire’s assembly on the laboratory test mean, a vibrant electrodynamic pot. FEM tool calculation allowed verification of their mechanical resistance and making sure that the assembly-related testing conditions would not impact dynamic behavior, modal behavior or fundamental frequencies of the tested lighting.

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  • 5 : Test completion and normative validation

Finally, the project was successfully completed by physical testing in laboratory. All of the vibratory stresses were applied to the luminaire. The Heatsinks successfully resisted to impacts and no crack initiation has been detected. PHIMECA provided PHILIPS with a testing report summarizing the main obtained results guaranteeing the heatsinks’ compliance with vibratory stress-related mechanical resistance norms.

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PHIMECA Engineering est une société d’ingénierie spécialisée dans l’évaluation et l’optimisation des performances des produits et des systèmes. Sa vocation est de proposer des solutions en ingénierie robuste et en fiabilité en s’appuyant sur un socle scientifique solide, un esprit d’entreprise et des valeurs morales partagés par tous ses collaborateurs.