GB/T 38250-2019 English PDF (GBT38250-2019)

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GB/T 38250-2019: Metallic materials -- Verification of the alignment of fatigue testing machines
GB/T 38250-2019
Metalic materials - Verification of the alignment of reliable testing machines
ICS 19.060; 77.040.10
N71
National Standards of People's Republic of China
Test of coaxiality of metal material fatigue testing machine
(ISO 23788.2012, IDT)
Published on.2019-10-18
2020-05-01 implementation
State market supervision and administration
China National Standardization Administration issued
Foreword
This standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This standard uses the translation method equivalent to ISO 23788.2012 "Metal material fatigue testing machine coaxiality test".
The documents of our country that have a consistent correspondence with the international documents referenced in this standard are as follows.
--- GB/T 16825.1-2008 Inspection of static single-axis testing machines - Part 1. Tensile and/or
Inspection and calibration (ISO 7500-1.2004, IDT).
This standard has made the following editorial changes.
--- Unify the expression of the term "percent bend" in the text, and change "β" in the text to "B";
--- Fixed the symbol error in Figure 3b), c), changed "W" to "w" and "Wg" to "wg".
This standard was proposed by the China Machinery Industry Federation.
This standard is under the jurisdiction of the National Testing Machine Standardization Technical Committee (SAC/TC122).
This standard was drafted. China National Machinery Testing Equipment Co., Ltd., Shenzhen Wan Testing Equipment Co., Ltd., China Aviation Industry Corporation
Beijing Great Wall Metrology and Testing Technology Research Institute, Jinan Xinguang Testing Machine Manufacturing Co., Ltd., Guangzhou University, Chengde Precision Testing Machine Co., Ltd.
Division, Shenzhen Hua Test Co., Ltd.
The main drafters of this standard. Liu Jilin, An Jianping, Tian Feng, Wang Jianguo, Xu Zhonggen, Wang Xinhua, Xu Weijia.
introduction
The coaxiality of the test machine in this standard refers to the consistency of the fixture geometry (loading) axis. Any deviation from this ideal state will result in
Load the chain's angle and/or lateral offset (or different axes) (see Appendix A). Different axes are represented by specimens or coaxiality measuring devices (hereinafter referred to as
There is an additional bending stress/strain zone on the "coaxiality sensor"). The bending stress/strain zone is superimposed on the assumed assumed uniformity
Stress/strain field. In a pure torsion test, any different axis will result in an additional bending stress/strain condition for biaxial torsion.
Different axial axes of the load chain have been shown to significantly affect fatigue test results in axial fatigue test systems (see references [1], [2] and
[3]).
The main cause of bending caused by different axes is nothing more than a combination of the following factors.
---The consistency of the fixture center line is poor;
--- The inherent defect of the sample or the coaxiality sensor itself.
Ideally, the bending component produced by the tester will remain the same for all specimens or concentricity sensors. Sample or coaxiality sensor
The resulting bending component varies from device to device.
Recent studies (see references [4] and [5]) have shown that no matter how fine the sample or sensor is processed, the inherent bending error
Always there. Inherent defects (ie eccentricity and tilt) arise from the geometric asymmetry of the axial centerline of the device and the type of strain gauge selected, installed,
Other measurement errors related to performance. The inherent bending error of the device can be significant, sometimes even exceeding the bending error caused by the different axes of the machine.
This standard eliminates the error caused by the inherent defects of the coaxiality sensor by the following method. Rotating the coaxiality sensor around its longitudinal axis
Turn 180° and subtract its bending component from the measured overall maximum surface bending strain. Therefore, the same material and nominal size are not
With the same device, the same coaxiality measurement results should be given; see the example of Figure 10 in Reference [2].
Test of coaxiality of metal material fatigue testing machine
1 Scope
This standard specifies the coaxiality test method for testing machines using strain gauges.
This standard applies to dynamic uniaxial tension and/or pressure, pure torsion, composite pull and twist, composite pressure twist and composite tension and compression fatigue of metal materials
Labor test machine.
The methods outlined in this standard are general and can be applied to static testers and non-metallic materials.
2 Normative references
The following documents are indispensable for the application of this document. For dated references, only dated versions apply to this article.
Pieces. For undated references, the latest edition (including all amendments) applies to this document.
Testing of static uniaxial testing machines for metal materials - Part 1 . Tensile and/or
Inspection and calibration
3 Terms and definitions
The following terms and definitions apply to this document.
3.1
Coaxial alignment
Consistency of the forcing axis of the load chain assembly (including the sample).
Note. Failure to meet this consistency results in additional bending moments on the specimen.
3.2
Coaxiality sensor alignmentcel
Strain gauge measuring device for coaxial machine inspection of precision machining test machine.
3.3
Coaxial gauge alignmentgauge
A precision machined mechanism consisting of a pair of split rods and a through stop gauge for fixture compliance inspection.
3.4
Average axial strain averageaxialstrain
Εo
The average longitudinal axis strain measured by a set of strain gauges distributed in the same cross section on the surface of the concentricity sensor.
Note. The average axial strain represents the strain at the geometric center of the section.
3.5
Loading chain loadtrain
All parts between the two, including the beam and the drive.
Note. The loading chain includes the sample.
3.6
Bending strain bendingstrain
Εb
The difference between the local strain measured by the strain gauge and the average axial strain.
Note. Bending strain is a vector characterized by size, direction, and discrete points of action. It usually varies with the position of the surface of the coaxiality sensor.
3.7
Testing machine coaxiality machinealignment
The degree of consistency of the fixture axis characterized by the maximum bending strain component εb, max, mc.
Note. Different axes of the machine appear to have lateral offset and/or angular tilt for the forcing axis of the upper and lower clamps.
3.8
Test machine orientation machineaspect
Front, rear, left and right sides of the test machine.
3.9
Maximum bending strain maximumbendingstrain
Εb,max
The vector with the largest bending strain amplitude in a given cross section.
Note. The maximum bending strain vector is characterized by size, direction, and discrete points of action.
3.10
Percentage percentagebending
The maximum bending strain is multiplied by 100 and divided by the average axial strain.
3.11
Measuring plane measurementplane
The cross section of the transverse axis of a set of strain gauges on the concentricity sensor.
3.12
Measuring orientation measurementorientation
The position of the coaxiality sensor relative to its longitudinal axis (0°, 90°, 180°, and 270°). The measurement orientation defines the strain gauge 1 or the coaxiality sensor
A permanent mark on the surface relative to the po...