BS 7034-7-1988 玻璃粘度和测定粘度固定点.第7部分:采用射束弯曲法对退火点和应力点的测定方法

标准号：BS 7034-7-1988
中文标准名称：玻璃粘度和测定粘度固定点.第7部分:采用射束弯曲法对退火点和应力点的测定方法
英文标准名称：Viscosity and viscometric fixed points of glass - Method for the determination of annealing point and strain point by beam bending
标准类型：Q30
发布日期：1989/1/31 12:00:00
实施日期：1989/1/31 12:00:00
中国标准分类号：Q30
国际标准分类号：81.040.10
适用范围：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