Probability of Failure of Sylgard-Mounted Optical Lenses in Head-Up Display During Thermal Cycle Testing

• Published in: International journal of thermophysics 2018-09, Vol.39 (9), p.1-12, Article 106
• Main Authors: Shravan Kumar, R. R., Vijayasankar, A., Rakesh, K., Jindal, T. K.
• Format: Article
• Language: English
• Subjects: Automobiles; Classical Mechanics; Condensed Matter Physics; Elastomers; Failure; Finite element method; Geophysics; Head-up displays; Industrial Chemistry/Chemical Engineering; Lenses; Optical glass; Physical Chemistry; Physics; Physics and Astronomy; Strain analysis; Surface finish; Thermal cycling; Thermal strain; Thermal stress; Thermodynamics
• ISSN: 0195-928X; 1572-9567
• DOI: 10.1007/s10765-018-2420-1

Lenses made from optical glass do not have a single characteristic strength. The strength of any optical glass is highly dependent on the area under stress and its surface finish. The nominal design strength of manufactured glass is typically in the 6.9–70 MPa range. This study presents an analysis of measured strain data and an approach to quantify the failure probability of optical lenses that are used in head-up display systems for aircraft applications when these lenses are subjected to accelerated thermal cycling. The thermal cycling produces thermal stress within the elastomerically mounted optical lens of the head-up display. We used a combination of experimental methods and finite element modeling to determine the thermal strain in the optical lens. The thermal strain values that were obtained using these methods were validated and were found to be in a cumulative distribution. This cumulative strain provides a quantitative estimate of the effects of thermal stress in the optical lens. We then determined the failure probability using Weibull parameters.