GB/T 38769-2020Metallic materials - Measurement of fracture toughness at impact loading rates using precracked Charpy-type test pieces (English PDF)

Foreword

This Standard was drafted as per the rules specified in GB/T 1.1-2009.

This Standard uses redrafting method to modify and adopt ISO 26843:2015 Metallic

Materials - Measurement of Fracture Toughness at Impact Loading Rates Using

Precracked Charpy-Type Test Pieces.

There are technical differences between this standard and ISO 26843:2015, and the

terms involved in these differences have been identified by vertical single lines (|) on

the outer margins. These differences and their reasons are as follows:

--- Introduce the relevant technical background in the "Scope" of the international

standard into the "Introduction" to make it easier for standard users to

understand the technical content and related background of the standard (see

Clause 1 of this Edition; Clause 1 of ISO 26843:2015);

--- With regard to normative references, this Standard has made the adjustments

with technical differences to adapt the technical conditions of China. The

adjustments are reflected in Clause 2 "Normative References". The specific

adjustments are as follows:

* Replace ISO 148-1 by the GB/T 229 modified to adopt international standards

(see Clause 3, Clause 4, 5.1, 5.6, 7.1, 9.4.5 of this Edition);

* Replace ISO 148-2 by GB/T 3808 modified to adopt international standards

(see 6.1, A.4, C.2.5 of this Edition);

* Replace ISO 14556 by GB/T 19748 modified to adopts international standards

(see Introduction, Clause 3, Clause 4, 6.2, 7.1, 9.4.5, A.2, D.2.2 of this Edition);

* Replace ISO12135 by GB/T 21143 modified to adopt international standards

(see Clause 3, 5.2, 7.2, 7.6, D.1, D.2.2, F.1, F.2, G.2 of this Edition);

* Replace ISO 26203-2 by GB/T 30069.2 modified to adopt international

standards (see 8.6, F.2 of this Edition).

--- Modify the definition of deltaalphamax, Jg and tf; clarify the definition of the name of the

symbol; make the subsequent legend and formula calculation clearer (see

Clause 3 of this Edition);

--- Stipulate that during the prefabricated fatigue crack process, the minimum and

maximum force ratio shall be controlled between 0 and 0.1, which is consistent

with China's national conditions and consistent with GB/T 21143 (see 5.4 of this

Edition);

--- Modify the international standard "difference from the average value of the nine-

point initial crack" into "difference from the average value of the nine-point final

crack" to make the context consistent and consistent with ISO 12135 and GB/T

21143 (see 9.4.5 of this Edition);

--- Increase the "general" and the classification of three different types of testing

machines; it is more in line with China's national conditions and easier for

standard users to understand (see Appendix A of this Edition);

--- Modify tin=f(t') in the original table into f(t'), keeping the context consistent (see

Table C.1 of this Edition);

--- Modify the symbol Utot in the international standard into Ws, keeping consistent

with the context of Appendix H (see D.2.2 of this Edition);

--- Modify Formula (E.5) to improve the accuracy of the data (see E.2 of this Edition);

--- Add a technical description of the iterative process, which is easy for standard

users to understand and is consistent with GB/T 21143 (see E.3 of this Edition).

This Standard was proposed by China Iron and Steel Industry Association.

This Standard shall be under the jurisdiction of National Technical Committee for

Standardization of Steel (SAC/TC 183).

Drafting organization of this Standard: Baoshan Iron & Steel Co., Ltd.; Shanghai Power

Equipment Research Institute Co., Ltd.; Lishi (Shanghai) Instruments Co., Ltd.;

Shenzhen Wance Testing Machine Co., Ltd.; NCS Testing Technology Co., Ltd.; and

China Metallurgical Information and Standardization Institute.

Chief drafting staffs of this Standard: Fang Jian, Tian Genqi, Dong Li, Gao Yifei, Wang

Bin, Zhang Jianwei, Huang Xing, Shi Kexian, and Hou Huining.

Metallic Materials - Measurement of

Fracture Toughness at Impact Loading Rates

Using Precracked Charpy-Type Test Pieces

1 Scope

This Standard stipulates the principles, specimens, testing machines, test procedures

and measurements, calculation of fracture mechanical parameters and test reports of

instrumental impact and evaluation of fracture toughness of prefabricated cracked

Charpy specimens of metal materials by fracture mechanics methods.

This Standard is applicable to the determination of fracture toughness of the

prefabricated cracked Charpy-type specimens of metallic 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 document.

GB/T 229 Metallic Materials - Charpy Pendulum Impact Test Method (GB/T 229-

2007, ISO 148-1:2006, MOD)

GB/T 3808 Verification of Pendulum-Type Impact Testing Machines (GB/T 3808-

2018, ISO 148-2:2008, MOD)

GB/T 19748 Metallic Materials - Charpy V-Notch Pendulum Impact Test -

Instrumented Test Method (GB/T 19748-2019, ISO 14556:2015, MOD)

GB/T 21143 Metallic Materials - Unified Method of Test for Determination of Quasi-

Static Fracture Toughness (GB/T 21143-2014, ISO 12135:2002, MOD)

GB/T 30069.2 Metallic Materials - Tensile Testing at High Strain Rates - Part 2:

Servo-Hydraulic and Other Test Systems (GB/T 30069.2-2016, ISO 26203-2:2011,

MOD)

Appendix A

(Normative)

Testing Machine Applicable to Various Types of Test

Procedures

A.1 General

The requirements for the general-purpose testing machine that performs the

procedures specified in this Standard are as follows.

A.2 Pendulum impact testing machine

A.2.1 The instrumented Charpy pendulum impact testing machine designed according

to the provisions of GB/T 19748 has the function of changing the position of the

pendulum release, so the testing machine has a variable impact velocity.

A.2.2 Other types of pendulum impact testing machines with fixed anvil/movable

hammer blade or fixed hammer blade/movable anvil and fixed or movable specimen

may be used.

A.2.3 The release position of the pendulum is variable, so the impact velocity of this

type of testing machine is usually variable.

A.2.4 Instrumented hammer blades or anvils may provide force-time or force-

displacement curve.

A.3 Drop-weight impact testing machine

It may be equipped with a spring-assisted energy storage device; and there is no limit

to the impact velocity of the testing machine or the mass of the drop-weight. The

striking hammer blade shall be designed by instrumentation to provide a force-time or

force-displacement curve.

A.4 Hydraulic servo high-speed testing machine

It is able to apply force to the specimen; if the system is in open loop mode, then the

system may be optimized by simulation test or pre-test to obtain a constant

displacement rate. It must be noted that the actuator shall reach the desired rate before

the hammer blade strikes the specimen. The hammer blade, anvil and support shall

meet the requirements of GB/T 3808.

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