1.1 这些试验方法的目的是为确定应变计性能特性提供统一的试验方法。包括建议的测试设备设计。 1.2 试验方法 E251 描述了确定五种应变计性能特征的方法和程序: 部分 第一部分- 一般要求 7. 第二部分- 参考温度下的电阻 8. 第三部分- 参考温度下的表压系数 9 第四部分- 表压系数温度系数 10 第五部分- 横向灵敏度 11 第六部分- 热输出 12 1.3 应变计是一种非常敏感的设备，其分辨率基本上是无限的。然而，它们对压力的反应很低，在使用时必须非常小心。必须以可接受的精度了解这些测试方法确定的性能特征，以便在现场应用中获得有意义的结果。 1.3.1 应变计电阻用于平衡仪表电路，并为测量提供参考值，因为所有数据都与应变计电阻相对于已知参考值的变化有关。 1.3.2 应变计系数是应变计的传递函数。它涉及应变计中的电阻变化及其承受的应变。应变计数据的精度不能优于应变计系数的精度。 1.3.3 随着温度的变化，表压系数的变化也会影响精度，尽管影响程度要小得多，因为变化通常很小。 1.3.4 横向灵敏度是测量应变计对垂直于其测量轴的应变的响应。尽管横向灵敏度通常远小于10 % 在量规系数中，如果不以合理的精度知道该值，则可能会出现较大的误差。 1.3.5 热输出是应变计对温度变化的响应。热输出是一种加法（非乘法）误差。因此，它通常可能比结构载荷的应变计输出大得多。为了纠正这些影响，必须通过连接到要进行测试的相同材料的试样上的应变计来确定热输出，通常是连接到测试结构本身。 1.4 金属粘结电阻应变计与伸长计的不同之处在于，它们测量标称标距长度上的平均单位伸长率（ΔL/L），而不是确定标距点之间的总伸长率。实践 E83 不适用于这些应变计。 1.5 这些测试方法不适用于使用粘结电阻应变计作为传感元件的传感器，如称重传感器和伸长计。 1.6 应变计是一个复杂系统的一部分，该系统包括结构、粘合剂、应变计、引线、仪器和（通常）环境保护。因此，许多因素会影响应变计的性能，包括用户技术。另一个复杂的问题是，应变计一旦正常安装，就无法重新安装到其他位置。因此，只能在统计基础上说明应变计特性。 1.7 本标准并非旨在解决与其使用相关的所有安全问题（如有）。 本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.8 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 4.1 应变计是最广泛使用的设备，用于确定材料、性能和分析结构中的应力。然而，应变计的性能特性受其制造材料及其几何设计的影响。这些测试方法详细说明了应变计若要以可接受的测量精度使用时必须附带的最低信息。 4.2 应变计的大多数性能特征都需要进行破坏性的机械测试。由于测试应变计不能再次使用，因此有必要对数据进行统计处理，然后将值应用于同一批次或批次的剩余群体。不承认由此产生的不确定性可能会产生严重影响。电阻测量是非破坏性的，可以对每个应变计进行测量。 4.3 正确设计和制造的应变计，其性能特征已准确确定，并具有适当的不确定性，代表了强大的测量工具。它们可以以极高的精度确定结构中的微小尺寸变化，远远超过其他已知设备。然而，必须认识到，单个应变计无法校准。如果需要对标准进行校准和可追溯性，则不应使用应变计。 4.4 要使用应变计，必须将其粘接到结构上。良好的结果在很大程度上取决于用于清洁粘合表面、粘合应变计和提供保护涂层的材料。安装人员的技能是成功的另一个主要因素。最后，必须仔细设计仪器系统，以确保它们不会过度降低应变计的性能。在许多情况下，实现这一目标是不可能的。如果是这样，在考虑数据准确性时，必须考虑到余量。在某些情况下，测试条件可能非常严重，以至于应变计系统的误差信号远远超过待测量结构变形的误差信号。在记录误差信号的幅度时必须非常小心，以便可以将实际值放置在相关的不确定性上。

1.1 The purpose of these test methods are to provide uniform test methods for the determination of strain gage performance characteristics. Suggested testing equipment designs are included. 1.2 Test Methods E251 describes methods and procedures for determining five strain gage performance characteristics: Section Part I— General Requirements 7 Part II— Resistance at a Reference Temperature 8 Part III— Gage Factor at a Reference Temperature 9 Part IV— Temperature Coefficient of Gage Factor 10 Part V— Transverse Sensitivity 11 Part VI— Thermal Output 12 1.3 Strain gages are very sensitive devices with essentially infinite resolution. Their response to strain, however, is low and great care must be exercised in their use. The performance characteristics identified by these test methods must be known to an acceptable accuracy to obtain meaningful results in field applications. 1.3.1 Strain gage resistance is used to balance instrumentation circuits and to provide a reference value for measurements since all data are related to a change in the strain gage resistance from a known reference value. 1.3.2 Gage factor is the transfer function of a strain gage. It relates resistance change in the strain gage and strain to which it is subjected. Accuracy of strain gage data can be no better than the accuracy of the gage factor. 1.3.3 Changes in gage factor as temperature varies also affect accuracy although to a much lesser degree since variations are usually small. 1.3.4 Transverse sensitivity is a measure of the strain gage's response to strains perpendicular to its measurement axis. Although transverse sensitivity is usually much less than 10 % of the gage factor, large errors can occur if the value is not known with reasonable precision. 1.3.5 Thermal output is the response of a strain gage to temperature changes. Thermal output is an additive (not multiplicative) error. Therefore, it can often be much larger than the strain gage output from structural loading. To correct for these effects, thermal output must be determined from strain gages bonded to specimens of the same material on which the tests are to run, often to the test structure itself. 1.4 Metallic bonded resistance strain gages differ from extensometers in that they measure average unit elongation (ΔL/L) over a nominal gauge length rather than total elongation between definite gauge points. Practice E83 is not applicable to these strain gages. 1.5 These test methods do not apply to transducers, such as load cells and extensometers, that use bonded resistance strain gages as sensing elements. 1.6 Strain gages are part of a complex system that includes structure, adhesive, strain gage, lead wires, instrumentation, and (often) environmental protection. As a result, many things affect the performance of strain gages, including user technique. A further complication is that strain gages once installed normally cannot be reinstalled in another location. Therefore, strain gage characteristics can be stated only on a statistical basis. 1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 4.1 Strain gages are the most widely used devices for the determination of materials, properties and for analyzing stresses in structures. However, performance characteristics of strain gages are affected by both the materials from which they are made and their geometric design. These test methods detail the minimum information that must accompany strain gages if they are to be used with acceptable accuracy of measurement. 4.2 Most performance characteristics of strain gages require mechanical testing that is destructive. Since test strain gages cannot be used again, it is necessary to treat data statistically and then apply values to the remaining population from the same lot or batch. Failure to acknowledge the resulting uncertainties can have serious repercussions. Resistance measurement is non-destructive and can be made for each strain gage. 4.3 Properly designed and manufactured strain gages, whose performance characteristics have been accurately determined and with appropriate uncertainties applied, represent powerful measurement tools. They can determine small dimensional changes in structures with excellent accuracy, far beyond that of other known devices. It is important to recognize, however, that individual strain gages cannot be calibrated. If calibration and traceability to a standard are required, strain gages should not be employed. 4.4 To be used, strain gages must be bonded to a structure. Good results depend heavily on the materials used to clean the bonding surface, to bond the strain gage, and to provide a protective coating. Skill of the installer is another major factor in success. Finally, instrumentation systems must be carefully designed to assure that they do not unduly degrade the performance of the strain gages. In many cases, it is impossible to achieve this goal. If so, allowance must be made when considering accuracy of data. Test conditions can, in some instances, be so severe that error signals from strain gage systems far exceed those from the structural deformations to be measured. Great care must be exercised in documenting magnitudes of error signals so that realistic values can be placed on associated uncertainties.