A quantitative study on the thermomechanical coupling effect of elasticity and plasticity of polymethyl methacrylate. (January 2023)

• Record Type: Journal Article
• Authors: Liu, Bingquan; Li, Liyun; Guo, Yanshuang; Liu, Peng; Cheng, Cheng; Jiao, Xiaojie; Fan, Shuaijie
• Is Part Of: Polymer testing. Volume 117(2023)
• Publication Date: 2023-01
• Subjects: Thermomechanical coupling effect -- Polymethyl methacrylate (PMMA) -- Infrared monitoring; Polymers -- Testing -- Periodicals; Polymères -- Tests -- Périodiques; 620.1920287
• DOI: 10.1016/j.polymertesting.2022.107809
• Languages: English
• ISSNs: 0142-9418

Abstract

Abstract: Quantitative study on the elastic and plastic thermomechanical coupling effect of solid materials has important theoretical significance for monitoring the deformation state and stability evaluation of engineering components. In this study, the sample is made of polymethyl methacrylate (PMMA), and uniaxial compression experiments are carried out. The sample experiences the elastic state and then the plastic state until the failure of the sample. The thermoelastic effect and thermoplastic effect in the deformation process of PMMA materials are monitored by infrared thermography and digital speckle system (DIC). That is, the relationship between the reversible elastic temperature change Δ T e and average stress change Δ σ m, and the relationship between the irreversible plastic temperature rise Δ T p and the dissipated energy Δ U p during the failure deformation process. The results show that when the sample is in the elastic regime, there is only elastic temperature change Δ T e inside the sample. When the sample enters the plastic deformation regime, the total temperature change Δ T includes elastic temperature change Δ T e and plastic temperature change Δ T p, and the temperature change has an obvious memory effect on the previous maximum load. When the previous maximum load exceeded, Δ T p increases rapidly. When the load P is removed, Δ T e disappears, and Δ T p remains. Combined with the theory of thermodynamics and solid mechanics, starting from the 3D stress state, the approximate linear incremental relationship between T e and σ m, and the accurate exponential total quantity relationship are derived. The incremental relationship and the full relationship combined with thermodynamic theory and the energy conservation principle, the relationship between the overall plastic temperature rise Δ T p and local plastic temperature rise Δ T pmax of the sample and the energy dissipation value Δ U p experienced by the sample and the local dissipation specific energy Δ u p is obtained. The theoretical calculation results of Δ T e and Δ T p are in good agreement with the experimental results. The research results can provide a new method for monitoring and identifying the stress and deformation state of engineering components through the temperature field. Highlights: The elastic heating coefficient of PMMA is constant. In the elastic regime, the temperature of many areas after unloading will fall back to the initial value. The sample has obvious creep, accompanied by obvious thermal mechanical coupling effect. The maximum local temperature rise of the sample can exceed 30 K. Through theoretical analysis, the constitutive relationship of thermal mechanical coupling effect of PMMA is obtained.