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GB/T 16920-2015

Chinese Standard: 'GB/T 16920-2015'
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BASIC DATA
Standard ID GB/T 16920-2015 (GB/T16920-2015)
Description (Translated English) Glass - Determination of coefficient of mean linear thermal expansion
Sector / Industry National Standard (Recommended)
Classification of Chinese Standard N64
Classification of International Standard 81.040.01
Word Count Estimation 9,968
Date of Issue 2015-12-31
Date of Implementation 2016-07-01
Older Standard (superseded by this standard) GB/T 16920-1997
Drafting Organization National Light Industry Product Quality Supervision and Inspection Center of glass
Administrative Organization National Glass Instrument Standardization Technical Committee (SAC/TC 178)
Regulation (derived from) State Standard Announcement 2015 No.43
Proposing organization China Light Industry Federation
Issuing agency(ies) Administration of Quality Supervision, Inspection and Quarantine of People's Republic of China; Standardization Administration of China

GB/T 16920-2015
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 81.040.01
N 64
Replacing GB/T 16920-1997
Glass - Determination of coefficient of
mean linear thermal expansion
玻璃 - 平均线热膨胀系数的测定
(ISO 7991.1987, NEQ)
ISSUED ON. DECEMBER 31, 2015
IMPLEMENTED ON. JULY 01, 2016
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Terms and definitions ... 4 
4 Instruments ... 5 
5 Test samples ... 6 
6 Procedures ... 7 
7 Representation of results ... 8 
8 Test of instrument performance ... 10 
9 Test report ... 11 
Appendix A (Informative) Collimation self-adjusting device for sample and push
rod shaft ... 12 
Glass - Determination of coefficient of
mean linear thermal expansion
1 Scope
This standard specifies the method for determining the coefficient of mean
linear thermal expansion of elastic solid glass.
This standard applies to the determination of the coefficient of mean linear
thermal expansion of glass of various materials.
2 Normative references
The following documents are essential to the application of this document. For
the dated documents, only the versions with the dates indicated are applicable
to this document; for the undated documents, only the latest version (including
all the amendments) are applicable to this standard.
GB/T 1216 External micrometer
GB/T 21389 Vernier dial and digital display calipers
3 Terms and definitions
The following terms and definitions apply to this document.
3.1
Coefficient of mean linear thermal expansion
α (t0; t)
Within a certain temperature interval, the ratio of the length change of the
specimen to the temperature interval and the initial length of the specimen,
expressed by the formula (1).
Where.
performance. The method is as shown in the calibration and verification of the
performance test of instrument.
4.3 Heating furnace
The heating furnace shall be matched with the dilatometer device. The upper
limit of temperature shall be about 50 °C higher than the expected determined
temperature of transformation (t). The working position of the heating furnace
as relative to the dilatometer shall have a reproducibility within 0.5 mm in the
axial and radial directions.
Within the range of test temperature (i.e., the upper limit temperature is 150 °C
lower than the highest expected transformation temperature tg, at least the
temperature difference between 300 °C and tg is greater than 150 °C, and shall
not be lower than 300 °C), throughout the determination interval of the entire
specimen length, the furnace’s temperature shall be constantly controlled within
±1 °C.
The heating furnace shall be able to meet the control requirements of 5 °C/min
± 1 °C/min. Within the range of the test temperature, the ideal rate of
temperature rise is 5 °C/min ± 1 °C/min.
4.4 Temperature measuring device
In the temperature range of t0 and t, it may be able to accurately determine the
temperature of the specimen, the error is less than ±1 °C.
5 Test samples
5.1 Shape and size
The specimen is usually rod-shaped, the shape of which depends on the type
of dilatometer used, the length L0 shall be at least 5 × 105 times the resolution
of the length measuring device of the dilatometer.
Note. For example, the specimen may be a round bar which has a diameter of
5 mm, length of 50 mm ± 1 mm; or according to the structure of the dilatometer,
it may also be a square bar which has a section of 5 mm × 5 mm and a length
of 25 mm ~ 100 mm. The specimen of other square or rectangular sections
shall be able to ensure the accuracy and repeatability of the measurement (see
Appendix A).
5.2 Preparation of specimen
Select the glass which has no defects such as stones, bubbles, and streaks.
Use the mechanical cutting or hot working methods to prepare it into the shape
and size required for the specimen, then make it annealed. The annealing
difference between the hot joint of the thermocouple and the specimen, the
apparent temperature of the specimen shall plus the corrected value.
Note. The magnitude of this corrected value depends on the rate of temperature
change as well as the rate of heat exchange between the heating furnace and
the specimen. Fundamentally, the corrected value is to be determined by
comparison with a constant temperature test.
6.4 Constant temperature test
At the initial temperature t0, determine the position of the dilatometer. Use this
reading as the zero point of the uncorrected amount of change of length ΔLmeas
to be measured. Then rise the temperature of furnace to the selected end-point
temperature t, keep the furnace’s temperature constantly at ±2 °C. After 20 min,
take the reading of ΔLmeas from the dilatometer.
Note. Although the temperature-rise test can determine the coefficient α (t0; t)
of various temperatures t during the test, if only one end-point temperature t is
required, it shall give priority to the constant-temperature test, because this test
may provide better accuracy.
7 Representation of results
7.1 Calculation of final length
From the measured length variable ΔLmeas, the corrected length L at the
temperature t is calculated by the use of formula (2).
Where.
The correction terms ΔLQ and ΔLB are explained in 7.2 or 7.3, respectively.
7.2 Calculation of expansion of specimen-bearing device (ΔLQ)
In the case of a single-pusher-type dilatometer, the correction term ΔLQ in the
formula (2) is the thermal expansion of the portion (length = L0) of the specimen-
bearing device which is located near the specimen at a temperature of t0.
In the case of a differential-pusher-type dilatometer, the correction term ΔLQ is
the thermal expansion of the standard bar. The standard bar has a same length
as the sample, which is L0 at the temperature of t0.
In either case, the correction term ΔLQ is calculated by the use of formula (3).
determination of glass. It shall repeat the blank test each time when performing
the test of instrument performance in accordance with clause 7.
7.4 Calculation of coefficient of average linear thermal expansion
To calculate the coefficient of average linear thermal expansionα (t0; t),
substitute the measured values of L0 and ΔLmeas, the correction value as
established in accordance with 6.2 and 6.3, the measured value of t0, the t value
(if it is the temperature-rise test, use the corrected value) into the formula (4).
Calculate α (20 °C; 300 °C) of two specimens (5.3). It may also determine α
(20 °C; 200 °C), α (20 °C; 100 °C) or α (20 °C; 400 °C), respectively, as needed.
If α (20 °C; t) < 10 x 10-6 K-1, take two significant digits; if α (20 °C; t) ≥ 10 x 10-
6 K-1, take 3 significant digits.
If the deviation of the results of the two specimens is not more than 0.2 × 10-6
K-1, take the arithmetic mean. Otherwise, use the other two specimens to repeat
the test.
8 Test of instrument performance
In order to check whether the entire test device is operating normally, use the
standard materials ......
Related standard:   GB/T 35595-2017  GB/T 35596-2017
Related PDF sample:   GB/T 15726-1995
   
 
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