標準號：BS 7034-7-1988
中文標準名稱：玻璃粘度和測定粘度固定點.第7部分:采用射束彎曲法對退火點和應力點的測定方法
英文標準名稱：Viscosity and viscometric fixed points of glass - Method for the determination of annealing point and strain point by beam bending
標準類型：Q30
發(fā)布日期：1989/1/31 12:00:00
實施日期：1989/1/31 12:00:00
中國標準分類號：Q30
國際標準分類號：81.040.10
適用范圍：This part of ISO 7884 specifies a method of determining the an-nealing point and the strain point of a glass by beam bending. These values have been found useful for specifying the cooling programme in the production of glassware. The annealing point and strain point include a well-defined temperature decrease during the measurement.At temperatures corresponding to the annealing and strain points, the viscosity of glass is highly time dependent. Hence, any viscosities that might be derived or inferred from measurements carried out according to this part of ISO 7884 cannot be assumed to represent equilibrium structural con-ditions. Therefore, the insertion of the strain point into the VFT-equation (see ISO 7884-1) is always impossible. The inser-tion of the annealing point causes in some cases marked failures.NOTE —The annealing and strain points by beam bending can also be determined using devices as specified in ISO 7884-4, but these devices are more expensive and the procedures lead to some viscosity-temperature and viscosity-time relationships besides the fixed points. In this part of ISO 7884, however, the device and procedure are restricted to the fixed-point determination.note:* 1 dPa·s = 1 dN·s/m