GOST 26446-85

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  ГОСТ 26446-85

GOST 26446−85 Connections soldered. Test methods for fatigue

GOST 26446−85

Group B09

STATE STANDARD OF THE USSR

CONNECTION BRAZED

Test methods for fatigue

Brazed and soldered joints. Methods of fatigue testing

AXTU 0072

Valid from 01.07.86
to 01.07.91*
__________________________________
* Expiration removed
Protocol 5−94 N Interstate Council
for standardization, Metrology and certification
(IUS N 11/12, 1994). — Note the manufacturer’s database.

DEVELOPED by the State Committee of USSR on standards by the Ministry of higher and secondary special education of the RSFSR

PERFORMERS

V. K. Andrikanis, PhD. tech. Sciences; A. V. Savchenkov, V. A. Asmolova, O. E. Spinel; Gruzdev, B. L., Cand. tech. Sciences; V. A. Kharitonov, I. V. Chervyakova

MADE with the USSR State Committee for standards

Zam. President V. P. Yunitskiy

APPROVED AND put INTO EFFECT by Decision of the USSR State Committee on standards of 22 February 1985, N 376


This standard specifies the testing methods of brazed joints of metals and alloys to fatigue in the bunch — and low-cycle elastic and elastic-plastic region in tension-compression, bending, shear and torsion; for a symmetric and asymmetric cycles of stress or strain, is given by a simple periodic law with constant parameters.

Fatigue test is carried out to:

determine the limit of endurance;

the selection of the optimal technological process of manufacturing brazed structures;

comparison of fatigue characteristics of solder joints of different materials;

periodic monitoring of the stability of the production process.

Terms, definitions and symbols used in the standard — GOST 23207−78 host 17325−79.

1. SAMPLE REQUIREMENTS

1.1. For the test solder joints on fatigue should be applied to the samples type I (Fig.1, tab.1), II (Fig.2, table 2), III (Fig.3, tab.3).

Damn.1. Type I

Type I

Damn.1

Notes:

1. The thickness of the solder joint is determined by Assembly clearance and physico-chemical properties of the soldered material and solder.

The choice of Assembly gap — according to GOST 19249−73.

2.  — the length of the working part of the specimen:

when the thickness of the solder joint is less than 0.5 mm;

«""" equal to or more than 0.5 mm.

Table 1

mm

Sample number
1	10	16	10
2	8	14	10
3	6	12	10
4	5	10	5
5	4	8	5

Damn.2. Type II

Type II

Damn.2

Notes:

1.  — blunting of the lateral faces of the sample.

2. Overlap width is determined by the physico-chemical properties of the materials brazed and solder technology soldering, circuit testing and design of solder joints for the necessary strength of the connection, and must provide the specified form of destruction.

3.  — the length of the working part of the sample .

Table 2

mm

To 0.5	5	-	5
From 0.5 to 1.0	8	0,2	10
From 1.0 to 3.0	10	0,5	10
From 3.0 to 5.0	15	0,28	10
SV. 5,0	20	0,28	10

Damn.3. Type III

Type III

________________
* Dimensions for reference

Damn.3

Notes:

1. The value is determined by the physico-chemical properties of the materials brazed and solder technology soldering, circuit testing and design of solder joints for the necessary strength of the connection, and must provide the specified form of destruction.

2.  — the length of the working part of the sample .

Table 3

mm

Sample number
1	10	M10	25	10	100
Two	8	M8	15	10	60
3	5	M5	10	5	45

For t-tests of brazed joints used samples of type IV, the shape and size of which is given in recommended Appendix 1.

1.2. The type and dimensions of the samples should be selected depending on the type of solder joint, the size of the parts with the most accurate reproduction of the stress state characteristic of the conditions of the test part.

1.3. The form and sizes of heads samples and transitional parts depend on the adopted method of mounting the specimen in the grips of the testing machine, material properties of the specimen and soldered joints.

Variants of execution of the heads of specimens is given in reference 2 below.

1.4. When testing samples of type I in main should be applied to samples N 4, at test samples of type III — 1 N samples.

1.5. The working part of the samples should be made with an accuracy not below 7-th class according to GOST 25347−82.

1.6. Tolerances of flatness, parallelism and alignment of samples should be below the 14th degree of accuracy 24643−81.

1.7. In the manufacture of samples of types II, III and IV, the maximum deviations of the sizes of the horizontal () and vertical () of the legs of fillet shall not exceed ±0.2 mm, the tolerance of straightness of the surface of the throat — ±0.1 mm (see the devil.4).

Damn.4. Limit deviations of dimensions in the manufacture of samples of types II, III and IV

Damn.4

1.8. Samples to be tested in heat-treated, subjected to heat treatment during or after soldering to the final processing of samples.

Note. If after heat treatment the metal has poor cuttability, brazed blanks for samples must be brought to the dimensions, including allowance for final processing and possible warping.

1.9. The distance between the grips of the test machine chosen so as to prevent buckling of the sample and the impact of efforts to capture the tension of the whole working part of the specimen.

1.10. When testing the type and number of defects on the samples shall not exceed the permissible values established for the solder products.

2. REQUIREMENTS FOR EQUIPMENT AND APPARATUS FOR TESTING

2.1. Requirements for equipment and testing equipment for fatigue — according to GOST 25.502−79.

2.2. Testing machines, fatigue should ensure the loading of samples on one or several schemes listed in the table.4.

Table 4

Circuit loading and the formulae for calculation of nominal voltage samples

Circuit loading	Sample type	The formula for calculating nominal stress samples
1. Re-AC-expansion-compression	I
II
III
II. Transverse deflection under cantilever loading	II
III. Pure bending in one plane	II
IV. Transverse bending during the rotation	I
III
V. Pure bending when rotating	I
VI. Re-alternating twist	I
III

	— the average value of the load cycle
	— the amplitude of the load cycle
	— torque
	the average value of the moment
	is the amplitude value of the moment
	— the angular velocity of rotation of the sample
	— distance from point of load application to the point of destruction
,	— the distance from the center of the solder joint to the point of load application
	— distance from point of load application to the point of mounting the sample

3. PREPARATION FOR TESTING

3.1. When testing the number of samples determined by the method given in the recommended attachment 3.

To build the fatigue curve and determine the endurance limit of the number of samples should be at least 10.

3.2. Samples for testing are produced from a minimum quantity of blanks.

3.3. Details of workpieces are cut with a specific orientation in relation to the macrostructure and the stress condition of the material.

3.4. Samples of the same batch should be soldered in one process cycle to ensure the identity of the form and dimensions of the fillets of the samples.

3.5. Samples it is recommended to solder together or one of the modes with the controlled product.

3.6. The shape and dimensions of blanks for the manufacture of samples of type III according to GOST 23047−78.

3.7. When soldering of workpieces grade brazed material, surface preparation, solder, or flux environment, the gap between the brazed workpieces, the method and mode of soldering, as well as the mutual arrangement of the heterogeneous parts in the sample of type III should be the same as in developed or controlled the process.

3.8. The gap when soldering ensure by means of appropriate devices.

Allowed to provide a gap through technological gasket. Gaskets are made from soldered material.

Plot of the solder joint with pads should be removed in the process of making samples.

3.9. Fillet brazed blanks, labeling and preparation of samples should not significantly influence the fatigue properties of the source material, heating of the sample in the manufacture should not cause structural changes and physical-chemical transformations in the metal. When carrying out mechanical processing, it is necessary to provide the minimum shot peening, to eliminate local overheating of the samples and the formation of surface defects.

3.10. Removing the last chip from the working part and of the heads of samples produced in a single clamping of the sample.

3.11. Straightening and edit brazed blanks are not allowed.

3.12. Samples from the brazed workpieces must be made on machine tools or with anode-mechanical cutting. Samples of sheet materials is allowed to cut vulcanite disks.

Burrs on the side faces of the samples should be removed easy zapilovku with a radius of curvature less than 1 mm.

3.13. Fillet samples for testing should be no more than 0.3 mm, if the purpose of the test is to study the influence of fillets on the fatigue properties of brazed joints.

Allowed machining of fillets, with a corresponding entry in the test report.

3.14. The working part of the flat specimens with a thickness of 2 mm or less, and cylindrical samples is measured with an accuracy of at least 0.01 mm, flat specimens with a thickness more than 2 mm not more than 0.05 mm.

3.15. Before the tests measure:

the cross section of the cylindrical specimen at the location of the solder joint;

the dimensions of the throat;

the length and width of the solder joint flat samples.

According to the obtained results calculate the area of the solder joint, rounding value to 0.5 mm.

When calculating the area of the solder joint cross-section of the throat is not considered.

4. TESTING AND PROCESSING OF RESULTS

4.1. The tests — according to GOST 25.502−79.

4.2. The test will be considered invalid:

at break of the specimen in the grips of the testing machine;

when breaking the sample out of the working part;

defects of the solder joint in fracture of the specimen (foreign inclusions, pores, Naropa, nespi — more than 10% of the area of the solder joint).

Note. With the exception of tests performed to determine the effect of solder joint defects on the characteristics of fatigue resistance of solder joints.

4.3. The results of tests on fatigue produce:

the curve of the distribution of longevity and the estimate of the average value and standard deviation of the logarithm of durability according to GOST 25.502−79, recommended app 5;

the construction of a set of fatigue curves on the parameter of failure probability according to GOST 25.502−79, recommended app 6;

building a distribution curve of endurance limit and an estimate of its average value and standard deviation according to GOST 25.502−79, recommended app 7;

the construction of the fatigue curve and the determination of the fatigue limit and limited quantity samples.

4.4. When comparing test results to consider the impact of scale factor.

4.5 Form of test protocols to record baseline data and test results of each sample — GOST 25.502−79.

The form of the consolidated test report to record the original data and test results of a series of identical samples are given in recommended Appendix 4.

4.6. Example of curve plotting fatigue test results on a limited batch of reference samples is given in Annex 5.

ANNEX 1 (recommended). THE SHAPE AND DIMENSIONS OF SAMPLES OF TYPE IV

ANNEX 1
Recommended

Version 1

From 1.0 to 3.0	10
From 3.0 to 5.0	15
SV. 5,0	20

Version 2

Version 3

Notes:

1. The size is prescribed depending on the method of mounting the sample.

2. , , ,  — the working part of the samples.

3. .

4. size choose from a range of — 3; 5; 8; 10 mm.

5. size choose from a range of 10; 15; 20; 30 mm.

6. .

7. Schematic of sample loading select table.4 of this standard:

for the performance of 1 — scheme II;

«" 2 and 3 of scheme IV, V, VI.

ANNEX 2 (informative). EMBODIMENTS OF HEADS SAMPLES

ANNEX 2
Reference

Samples of type I

Damn.1


The samples of a type II

Damn.2

Table 1

mm

5	20	25	5
8	20	25	Five
10	25	30	10
15	30	35	10
20	35	40	10

Note. Allowed the use of reinforcing pads on the gripper parts of the samples.

Samples of type III

Damn.3

Table 2

mm

Sample number
1	10	16	M12x1,5	25
2	8	14	M10x1,5	15
3	5	10	М6х0,75	10

APPENDIX 3 (recommended). PLANNING EXTENT OF TESTS

APPENDIX 3
Recommended

1. When planning the amount of testing necessary to determine the minimum number of samples for obtaining defined characteristics of fatigue resistance with a given accuracy and reliability.

2. The number of samples at each stress level is determined by table.1−3, asking the following source data:

relative error of average values of determined characteristics ;

a unilateral confidence level ;

the anticipated coefficient of variation ;

the form of the distribution of the designated features.

Table 1

The number of samples with normal distribution law

		when
0,10	0,15	0,20	0,25	0,30
0,05	0,90	8	Fifteen	25	40	65
0,95	13	25	40	65	100
0,99	25	50	100	150	200
0,10	0,90	3	5	8	13	15
0,95	5	8	13	20	25
0,99	8	15	25	32	50
0,15	0,90	-	3	4	6	8
0,95	3	5	6	10	13
0,99	5	8	13	15	25
0,20	0,90	-	-	4	5	6
0,95	-	4	5	6	8
0,99	4	6	8	10	15

Table 2

The number of samples in the Weibull distribution

		when
0,4	0,5	0,6	0,7	0,8	0,9	1,0	1,1	1,2	1,5	1,8	2,0	3,0
0,05	0,90	100	200	250	400	500	500	650	1000	1000	-	-	-	-
0,95	150	250	400	500	650	800	1000	-	-	-	-	-	-
0,99	315	500	800	1000	1000	-	-	-	-	-	-	-	-
0,10	0,90	32	50	65	100	125	150	200	250	315	400	500	500	1000
0,95	50	80	100	150	200	250	400	500	650	800	800	800	1000
0,99	100	150	200	315	400	500	650	650	800	1000	-	-	-
0,15	0,90	15	25	32	40	65	80	80	125	150	200	250	315	500
0,95	25	40	50	Eighty	100	125	150	200	200	315	400	500	800
0,99	40	65	100	150	200	250	315	400	500	800	1000	-	-
0,20	0,90	10	15	20	32	40	40	50	65	80	125	150	200	310
0,95	15	25	32	40	50	80	100	125	150	200	250	250	400
0,99	25	40	65	80	125	150	150	200	250	315	400	500	1000

Table 3

The number of samples logarithmically normal law of distribution

		when
0,4	0,5	0,6	0,7	0,8	0,9	1,0
0,05	0,90	100	150	250	315	400	500	650
0,95	150	250	400	Five hundred	650	800	1000
0,99	315	500	800	-	-	-	-
0,10	0,90	25	40	65	80	100	125	150
0,95	40	65	100	125	150	200	250
0,99	80	125	200	250	315	400	500
0,15	0,90	13	20	25	40	50	50	65
0,95	20	32	40	50	80	100	100
0,99	40	50	80	125	150	200	200
0,20	0,90	6	10	15	20	25	32	40
0,95	10	15	25	32	40	50	65
0,99	20	32	50	65	80	100	125

3. Relative accuracy describes the degree of measurement accuracy and is selected from the range: 0,05; 0,10; 0,15; 0,20.

4. The value of the unilateral confidence choose from a number of: 0,90; 0,95; 0,99. For General engineering purposes , usually taken equal to 0.95.

5. The values of fatigue resistance characteristic usually obeys the normal distribution law, however, the distribution of other laws.

6. In the case where the test results obtained coefficient of variation less than or equal to the given one, then the test is stopped. If the coefficient of variation is greater than specified, the accuracy is insufficient, and needs more testing. In this case, the amount of testing to recalculate the values .

APPENDIX 4 (recommended). The test solder joints on fatigue

ANNEX 4
Recommended

PROTOCOL N____
testing solder joints for fatigue

1. The purpose of the tests

2. The type and number of sample

3. Materials

— brazed I

grade or chemical composition

— direction of fibers

— brazed II

grade or chemical composition

— direction of fibers

— the brand or the chemical composition of the solder

— flux or a gas environment

4. Technological parameters of production of samples

— the number of samples from a single blank

— method of surface preparation for soldering

— the amount of Assembly clearance

— the mass of solder

technological cusp

— soldering method (GOST 17349−79)

— soldering temperature

— the dwell time during soldering

— pressure: a) gas environment in the working volume

b) compression sample (load sample)

— treatment after brazing

5. Test conditions

— type of loading

— loading (according to table.4)

— asymmetry factor

— loading frequency

— database testing

— type testing machine

method to determine the nominal voltage

— features a mustache conditions test

Responsible for testing in this series of samples

signature

Head of laboratory

signature

Note. In the field «note» specify the defects found in the soldered seam and the heat affected zone after the destruction of the sample.

ANNEX 5 (reference). THE CURVE OF FATIGUE ON THE TEST RESULTS OF A LIMITED BATCH OF SAMPLES

ANNEX 5
Reference

1. The test was subjected to lap flat samples of type II alloy KHN60VT, soldered by solder VPR 7 ( — 1190°C, exposure time — 15 min) in a mixture of argon with dissociirovati perborate potassium.

The dimensions of the samples:

1.2 mm, 8 mm, 1.1 mm, 3.4 mm, 0.4 mm

Tests were carried out according to the scheme of transverse bending of cantilever loading on the symmetric cycle. The oscillation frequency of the sample — 50 Hz.

Values of maximum stress cycle () for each of the 10 samples tested () are given in table.1.

Table 1

	MPa	cycles
1	390	2,6·10
2	360	7·10
3	310	1,8·10
4	280	1,1·10
5	275	5,4·10
6	270	3,3·10
7	220	5,2·10
8	215	1,3·10
9	195	1,9·10
10	180	4,5·10
	2695

2. When regression analysis of the test results for the independent value taking , and the dependent variable is , in this case, the check values to a normal distribution is carried out according to GOST 8.207−76.

3. For brazed joints, the equation of the regression line has the form:

, (1)

where , the coefficients of the linear equation;  — the number of cycles.

4. The estimation of the parameters of the equation of the regression line produced by the formulas derived from the method of least squares.

The results of intermediate and final calculations are given in table.2.

Table 2

1	4, 415 bln	120,5	14520,25	+535,6	Of 4.125	0,0841
2	4,845	90,5	8190,25	+438,5	4,433	0,1721
3	4,255	40,5	1640,25	+172,3	4,945	0,476
4	5,041	10,5	110,25	+52,9	5,253	0,0446
5	5,732	5,5	30,25	+31,5	5,304	0,2202
6	4,519	0,5	0,25	+2,03	5,355	0,7001
7	5,716	-49,5	2450,25	-282,9	5,868	0,023
8	6,114	-54,5	2970,25	-333,2	5,919	0,0381
9	6,279	-74,5	5550,25	-467,25	6,124	0,024
10	6,653	-89,5	8010,25	-595,5	6,278	0,141
	53,58	43472,5	-446,02	1,9212

4.1. The average value determined by the formula:

, (2)

where  — the maximum stress of the cycle on a sample, MPa;

 — number of samples;

1, 2, 3….

MPa.

4.2. Define coefficients of the equation of the regression line and by the formulas:

(3)

, (4)

where , the value of the logarithm of the number of cycles on the sample;

 — the arithmetic average of the values .

4.3. Evaluation of the theoretical equation of the regression line is the empirical equation of the line.

(5)

After substitution computed by the formulas (2), (3), (4) values , and equation (5) would be:

(6)

4.4. Substituting in equation (6) values , we find values for each tested sample.

5. With the aim of building a condence region for the regression line produced an assessment of the empirical variance around the regression line by the formula

, (7)

where  — dispersion;

 — the value of the logarithm of the number of cycles on the specimen, calculated according to the regression equation.

.

6. Assessment of the dispersion equation parameters of the empirical regression line and the values produced by the formulas

; (8)

; (9)

, (10)

where , ,  — dispersion equation parameters of the regression line.

;

;

Then . (11)

The determined values of for values is the largest, the smallest and closest to the average (i.e. for 1st, 4th and 10th samples).

; ;

; ;

; .

7. Confidence intervals for the parameters of the equation of theoretical regression line and the General average value calculated by the formulas

; (12)

; (13)

, (14)

where  — criterion of student, which depending on the confidence probability and the number of degrees of freedom , find at the table.7 GOST 25.501−78.

For General engineering purposes confidence probability , usually taken equal to 0.95.

The number of degrees of freedom determined by the formula:

,

where is the number of samples.

8. The computed bounds of the condence region of the equation of the regression line. Find the value for a is 0.95 and the number of degrees of freedom 8:

Substituting the values in formula (14), we get:

9. Based on these data, we build the empirical regression line and the border of the condence region (see drawing).

The empirical regression line and the border of the condence region

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M.: Publishing house of standards, 1985