采用有限元分析法量化不同中空玻璃边缘密封的热位移

Quantification of Differential Thermal Movement in Insulating Glass Edge Seals Using Finite Element Analysis

间隔条和玻璃板片之间的相对热位移是中空玻璃边缘密封乃至中空玻璃(IGU)本身老化的主要原因之一。作者采用有限元分析法(FEA),建立了发生在大尺寸(1.5 m×2.1 m)的中空玻璃边缘密封的热位移与温差变化之间的模型,这是三种商业化的、不同材质的、不同设计的间隔条,在温度变化为-30^+60℃范围内的模型。此模型是基于铝间隔条和镀锌钢间隔条与尼龙插角的搭配,不锈钢间隔条和弯曲插角的搭配。尼龙插角假定为实心的并稳固地固定于间隔条上;弯曲插角被建模成实心弯曲的金属插角,并同样稳固地固定于间隔条上。由于实际的弯曲插角是空心的,模型可能高估了这种转角设计的应力。正如预期那样,在低温时,插角会被向内拉,导致弯曲角度大于90°;在高温下,插角会被向外推,导致弯曲角度小于90°。通过检测发生在中空玻璃周边第一道密封的聚异丁烯密封胶厚度的变化,作者发现,到目前为止,不锈钢间隔条对于截面积的变化影响最小;铝制间隔条的影响最大。这个发现与基于间隔条材料与浮法玻璃之间热膨胀系数差异而预期的性能一致。因此,热位移引起的第一道密封的有效扩散横截面变化,可以解释为何具有不同间隔条材料的中空玻璃之间的性能差异。

Differential thermal movement between the spacer frame and the glass panes is a key contributor to the aging of insulating glass edge seal and of the insulating glass unit-IGU- itself. Using finite element analysis _ FEA _ the authors modeled the thermal movements occurring in the edge seal of a large IGU （1.5 × 2.1 m^2） as a result of temperature variations -- 30℃ to ＋ 60℃ -- for three commercially available spacer bars of different material and design. The model was based on nylon corner keys for the aluminum and galvanized steel spacers and bent corners for the stainless steel spacers. The nylon corner keys were assumed to be solid and firmly bonded to the spacers; whereas the bent corners were modeled as solid, bent metal corner keys, also firmly bonded to the spacers. Since actual bent corners are hollow, the model tends to overestimate the stresses for this corner design. As expected, at the low temperature, the corners are pulled inward, resulting in a bending angle --90° while at the high temperature, the corners are pushed outwards, resulting in a bending angle --90°. Monitoring the changes occurring in the thickness of the polyisobutylene primary seal along the circumference of the IGU, the authors found that the stainless steel spacer had, by far, the least effect on the change in the crosssectional area, while the aluminum spacer had the most substantial effect. This finding is in keeping with the expected performance based on the difference in thermal expansion coefficients between spacer material and float glass. Thus, changes in the effective cross-sectional area of the primary seal available for diffusion that arise from differential thermal movements, are likely to account for the observed performance differences of IGUs haying different spacer materials.