Dynamic birefringence of poly-(4,4′-hydroxydiphenylene) pyromellitic amic acid solutions

Acrylic is widely used in aquariums, windows of planes and submarines, and even scientific experiments like the Sudbury Neutrino Observatory (SNO) and the Jiangmen Underground Neutrino Observatory (JUNO). Internal stress has a significant impact on the properties and characteristics of acrylic such as strength, fracture and creep, which is highly concerned and has become a hotspot in research field. The measurement of internal stress is an important issue, which includes two aspects - the calibration of stress-optical coefficient of acrylic and the measurement of birefringence optical path difference (BOPD) caused by internal stress. The measuring equipment mainly realize the measurement of BOPD, and currently have the largest dynamic range of 50–3000 nm. Dynamic range is considered as one of the core performance indicators of measuring equipment, and a larger dynamic range is urgently required to meet the needs of different scenarios. The novel equipment for measuring internal stress in acrylic has been designed and developed based on photo-elastic principle and spectrometric method, which has the dynamic range of 20–12000 nm and the uncertainty of stress measurement better than 3%. The measuring principle, components, functions and measurements of the novel measuring equipment are introduced and discussed in this article.

Section: The Design and Development Of The Novel Measuring Equipment ...mentioning

confidence: 99%

The novel equipment for measuring internal stress in acrylic

Yang,

Heng,

Chen

et al. 2024

“…There are three fitting parameters -"a" stands for sin 2 (2𝛼), "b" stands for optical path difference 𝛿 and "s" stands for additional step when there is absorption effect for ordinary light and extraordinary light [13, pp. 147-150], [14][15][16][17][18]. R-square (𝑅 2 ) as goodness of fit is used to evaluate fitting.…”

Section: Jinst 18 P03044mentioning

confidence: 99%

The automatic measurement system for internal stress of acrylic

Yang

Heng

Chen³

et al. 2023

The manual measurement system for internal stress of acrylic was designed and realized, which is based on photo-elastic principle and spectrometric method. The manual measurement system can support mobile and quantitative measurement, and plays an important role in the fields of material research and engineering project. With the extensive application of the stress measurement system, automation is required to promote measuring efficiency and overcome the shortcomings of the manual measurement system. Electric control turntable was chosen as the key component for automation and adopted in the automatic measurement system. The automatic measurement system is controlled by program and user interface for operation has also been improved. The automatic measurement system has been realized and used for measuring internal stress of acrylic in the laboratory, which achieved the expected effect. The components of the automatic measurement system, the user interface for control program and data processing, and the stress measurements of the acrylic samples by the automatic measurement system are discussed in this article.

“…Birefringence will happen when the light passes through the acrylic with internal stress. Ordinary light and extraordinary light are produced, the polarization directions of which are perpendicular [14][15][16][17][18]. The optical path difference 𝛿 derives from the coherent superposition of ordinary light and extraordinary light, and the decomposition figure of the magnitude of a light vector is shown in figure 8.…”

Section: The Modification Of Objective Function Of Numerical Fitting ...mentioning

confidence: 99%

The study of acrylic bonding gap stress for the JUNO Central Detector

Yang¹,

Heng²,

Li³

et al. 2022

The Central Detector (CD) of Jiangmen Underground Neutrino Observatory (JUNO) has a huge acrylic spherical vessel, which will contain 20000 tons of liquid scintillator, being immersed in pure water, endure about 3 × 107 N of buoyancy. It is composed of 263 pieces of acrylic spherical panels bonded by the mass polymerization. Acrylic stress is critical to the structural safety of the JUNO CD, and it is required not to be greater than 3.5 MPa. The specialized measurement system for acrylic stress of the JUNO CD has been designed and realized, which supports non-destructive and quantitative measurement. The measurement system was applied to the main acrylic spherical panels without bonding gap first to verify stress level, which met JUNO's requirement. The bonding quality of acrylic spherical panels is critical, and the stress of bonding gap is concerned. The stresses of acrylic bonding gaps were measured using acrylic samples to help study the bonding techniques. The stress optical coefficient of acrylic bonding gap was calibrated and different bonding methods were studied and compared. We found that the objective function of numerical fitting for acrylic bonding gap needs modification when the measured optical path difference is large, which was analyzed and discussed in this article.