1.1本文件给出了确定塑料载荷下挠曲（三点载荷下的弯曲应力）温度的通用试验方法。定义了不同类型的试样和不同的恒定载荷以适应不同类型的材料。 1.2 ISO 75-2对塑料（包括加工前纤维长度不超过7.5 mm的填充塑料和纤维增强塑料）和硬橡胶提出了具体要求，而ISO 75-3对加工前纤维长度大于7.5 mm的高强度热固性层压板和长纤维增强塑料提出了具体要求。 1.3规定的方法适用于评估不同类型材料在高温下以规定的升温速率负载下的相对行为。所获得的结果不一定代表最高适用温度，因为在实践中，诸如时间、加载条件和标称表面应力等基本因素可能与测试条件不同。只有具有相同室温弯曲模量的材料才能实现数据的真正可比性。 1.4这些方法规定了试样的优选尺寸。 1.5使用所述测试方法获得的数据不用于预测实际最终使用性能。这些数据不用于设计分析或预测材料在高温下的耐久性。 1.6这种方法通常被称为热偏转温度或热变形温度（HDT）测试，尽管没有正式文件使用这种名称。

1.1 This document gives a general test method for the determination of the temperature of deflection under load (flexural stress under three-point loading) of plastics. Different types of test specimen and different constant loads are defined to suit different types of material. 1.2 ISO 75-2 gives specific requirements for plastics (including filled plastics and fibre-reinforced plastics in which the fibre length, prior to processing, is up to 7,5 mm) and ebonite, while ISO 75-3 gives specific requirements for high-strength thermosetting laminates and long-fibre-reinforced plastics in which the fibre length, prior to processing, is greater than 7,5 mm. 1.3 The methods specified are suitable for assessing the relative behaviour of different types of material at elevated temperature under load at a specified rate of temperature increase. The results obtained do not necessarily represent maximum applicable temperatures because, in practice, essential factors, such as time, loading conditions and nominal surface stress, can differ from the test conditions. True comparability of data can only be achieved for materials having the same room-temperature flexural modulus. 1.4 The methods specify preferred dimensions for the test specimens. 1.5 Data obtained using the test methods described are not intended to be used to predict actual end-use performance. The data are not intended for design analysis or prediction of the endurance of materials at elevated temperatures. 1.6 This method is commonly known as the heat deflection temperature or heat distortion temperature (HDT) test, although there is no official document using this designation.