GB/T 24522-2020Metallic materials--Method of test for the determination of resistance to stable crack extension using specimens of low constraint (English PDF)

1 Scope

This standard specifies the low-constrained, easy-to-plastic-deform homogeneous metal materials with cracks when subjected to quasi-static loading, steady-state crack propagation resistance,

Method for measuring crack opening displacement delta5 and critical crack tip opening angle Psic. Tension on compact tensile specimens with notches and central cracks

The specimens were pre-fractured through fatigue and tested under conditions of slowly increasing displacement.

The test methods described in this standard cover those specimens that do not meet the dimensional insensitivity of fracture performance, such as the relatively thin compact tensile

Tensile specimen and central crack tensile specimen.

This standard provides a method for determining the crack propagation resistance curve (R-curve). Determine the breaking of compact tensile specimens with ISO 12135.2002

The characteristic values of crack toughness are similar. In Appendix D, a method for measuring the characteristic values of fracture toughness using a central crack tensile specimen is given.

For the measurement of crack propagation resistance, the multi-sample method and the single-sample method can be used. The multi-sample method requires loading multiple nominally identical samples

To different displacements. The crack growth resistance curve is obtained by identifying the ductile crack growth area and the subsequent measurement of the fracture crack growth line. The single-sample method based on the unloading compliance method and the potentiometric method can also measure crack propagation as long as it meets the specified accuracy requirements.

The recommended single sample method is described by ISO 12135.2002.Either way, the goal is to obtain enough data points to fully describe

Material crack propagation resistance behavior.

Measuring delta5 is relatively simple and easy. The result of delta5 is represented by the resistance curve, showing the uniqueness of the crack propagation within the limited range. keep away

In this limited range, the delta5 resistance curve of the compact tensile specimen shows a strong dependence on the width of the specimen, while the delta5 resistance of the central crack tensile specimen

The force curve shows a weak dependence on the width of the specimen.

The CTOA test is more difficult to determine than delta5.The critical CTOA is represented by a stable value reached after a certain degree of crack propagation. CTOA The concept can be applied to the occasions where the crack propagation is very large, and the applicability exceeds the existing application range of delta5.

Both determinations of crack propagation resistance are suitable for structural evaluation. The concept of delta5 is complete, based on a simple crack driving force formula

The existing evaluation steps can be applied to structural integrity issues.

The concept of CTOA is generally more accurate. Numerical methods are needed in structural applications, such as finite element analysis.

Studies have shown that the compact tensile specimen and the central crack tensile specimen are loaded until the maximum load, stable CTOA and only resistance

The curves are closely related. The establishment of an analytical or numerical relationship between the delta5 resistance curve and the critical CTOA remains to be further studied.

2 Normative references

The following documents are essential for the application of this document. For dated reference documents, only the dated version applies to this article

Pieces. For the cited documents without date, the latest version (including all amendments) applies to this document.

ISO 3785 Marking of metal material sample axis relative to product texture (Metalicmaterials-Designationoftest specimenaxesinrelationtoproducttexture)

Inspection of ISO 7500-1 static uniaxial testing machine for metallic materials. Part 1.Tension and/or compression testing machine force measurement system

Inspection and calibration (Metalicmaterials-Calibrationandverificationofstaticuniaxialtestingmachines-Part 1.

Tension/compressiontestingmachines-Calibrationandverificationoftheforce-measuringsystem)

ISO 9513 Calibration of Extensometer for Metal Material Uniaxial Test (Metalic materials-Calibration of extensometersystemsusedinuniaxialtesting)

ISO 12135.2002 The unified determination method of quasi-static fracture toughness of metal materials (Metalicmaterials-Unified

GB/T 24174 | GB/T 24523 | GB/T 24173 | GB/T 10128 | […]