According to international standards/Domestic core standards（GB/T 16491-2008TheISO 7500-1:2018），0.5 Displacement measurement error of tensile testing machineless than or equal to±0.5%±1Mm(Some devices can be optimized to±0.5%±0.5Mm）The core focus is on two measurement scenarios: "horizontal beam movement displacement" and "specimen deformation displacement". The specific requirements are as follows:

1、 Core definition and scope of application of displacement measurement error

1. Definition of Error and Computational Logic

The displacement measurement error is divided into "beam displacement error" (the positioning accuracy of the equipment's own beam movement) and "deformation displacement error" (the actual deformation accuracy of the sample measured by an extensometer), both of which must meet the requirements of 0.5 Level requirements:

Formula for displacement error of crossbeam：

Displacement error= |(Actual displacement measurement)-Standard displacement/Standard displacement| × 100% +Fixed deviation（±1Mm）

(The standard displacement is provided by legal calibration equipment such as laser interferometers and traced back to the national length standard)

Deformation displacement error：

The accuracy of extensometer (the core component for measuring sample deformation) is required≥±0.1%（0.5 Standard equipment configuration), some models can achieve±0.05%The error calculation logic is consistent with the displacement of the crossbeam, but the fixed deviation is smaller（±0.5Mm）.

2. Scope of Application

Beam displacement: within the effective measurement range (such as0~1000mm）All must meet the error requirements and have no load range limitations;

Deformation displacement: within the range of the extensometer gauge length (such as25mmThe50mm）The deformation amount of the sample needs to be≥The range of the extensometer10%(Avoid error amplification under small deformations).

Example Description

beam movement100mmWhen, the maximum allowable error is:100mm×±0.5% + 1Mm = ±0.5mm + 0.001mm = ±0.501mmThe measured displacement needs to be within99.499mm~100.501mmWithin the scope;

Using gauge length50mmThe extensometer measures the deformation of the specimen5mmWhen, the maximum allowable error is:5mm×±0.1% + 0.5Mm = ±0.005mm + 0.0005mm = ±0.0055mmThe measured deformation needs to be within4.9945mm~5.0055mmWithin the scope.

2、 Specific requirements for different standard systems (globally consistent)

Mainstream standards 0.5 The displacement error of the tension machine requires a high degree of uniformity, with only slight differences in fixed deviation:

Key explanation:ASTM E4Standard none“0.5level”Definition of displacement error, which 1 Level equipment displacement errorless than or equal to±1.0%If it is necessary to meetASTMStandard and required 0.5 Grade accuracy, compatibility needs to be selected simultaneouslyISOandASTMThe accuracy of the equipment and extensometer needs to be improved≥±0.1%.

3、 Key considerations in practical applications

1. of error“Two-factor authentication”requirement

0.5 The displacement accuracy of the equipment needs to be verified through two calibrations:

Beam displacement: Calibrate with a laser interferometer (standard for legal metrology institutions), and the calibration certificate should specify each travel point (such as10mmThe50mmThe100mm）Actual measurement error≤±0.5%±1Mm；

Deformation displacement: calibrate the extensometer with a standard gauge block to ensure the accuracy of deformation measurement≥±0.1%Otherwise, it will affect the calculation of deformation dependent indicators such as yield strength and elastic modulus.

2. Matching relationship with force accuracy

0.5 The core of a tension machine is' force value accuracy '+Double standard of displacement accuracy is indispensable:

If only the force value error meets the standard and the displacement error exceeds the standard (such as beam displacement error)±0.8%）The device still does not meet the requirements 0.5 Level requirements;

Research and development, third-party testing, and other scenarios need to be considered simultaneously to avoid displacement errors“力-Displacement curve”Distortion (such as yield point deviation, elongation calculation errors).

3. The impact of environment and usage on errors

Temperature impact: The equipment needs to be10~35℃Used in the environment, every deviation in temperature 20℃±5℃The displacement error may increase0.1%~0.2%(Thermal expansion and contraction affect the accuracy of ball screws);

Vibration impact: The laboratory needs to avoid strong vibrations (such as near hydraulic presses and machine tools), otherwise it may cause positioning deviation of the crossbeam;

Fixture and specimen: Eccentricity in specimen clamping can cause“Additional displacement”If the inclination of the sample causes the actual movement distance of the crossbeam to be inconsistent with the deformation of the sample, it is necessary to reduce the error through standardized clamping.

4. Common Misconception: Confusion“Displacement accuracy”and“Itinerary scope”

Travel range (such as0~1000mm）It is the maximum distance that the device can move and is not directly related to accuracy;

For example:1000mmThe itinerary 0.5 Grade equipment, in10mmSmall itinerary and1000mmUnder large travel, displacement errors are required≤±0.5%±1MmThe larger the travel distance, the greater the error.

summary

accuracy class 0.5 A grade tensile testing machine, whichMeasurement error of beam displacementless than or equal to±0.5%±1Mm，Sample deformation displacement error (extensometer)≥±0.1%(Core indicators), and must be within the valid itinerary/Meet the requirements within the gauge range. In actual use, a calibration certificate from a legal metrology institution (laser interferometer) is required+Based on the calibration of standard measuring blocks, while controlling environmental conditions and clamping specifications, ensure the consistency of displacement data and force data, and meet the requirements of high-precision scenarios such as research and development and testing.