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有机玻璃(聚甲基丙烯酸甲酯)型材,具有表面光滑、透明、可热弯、易粘结、有一定强度等优点,故在水工模型中尤其在制作模拟孔洞、管道时被广泛采用。但有机玻璃也有一个明显的缺点:即热变形大。其线胀系数α约为7.3×10~(-5)/℃,此值约为混凝土的7倍或钢的6倍。当温度变化较大,模型不能自由变形时将会产生不可忽视的温度应力。例如当模型两端固结,温度变化ΔT=20℃,按一维温变应力问题计算其温度应力σ为:
Plexiglas (polymethylmethacrylate) profiles, with the surface smooth, transparent, can be bent, easy to bond, have some strength, etc., so in the hydraulic model, especially in the production of simulated holes, pipes are widely used. However, plexiglass also has a significant drawback: the large thermal deformation. The linear expansion coefficient α is about 7.3 × 10 -5 / ℃, which is about 7 times of concrete or 6 times of steel. When the temperature changes a lot, the model can not be deformed freely and it will produce the non-negligible temperature stress. For example, when the model is fixed at both ends, the temperature change ΔT = 20 ℃, according to one-dimensional temperature stress calculation of the temperature stress σ is: