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GB/T 4161-2007 English PDF (GBT4161-2007)

GB/T 4161-2007 English PDF (GBT4161-2007)

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GB/T 4161-2007: Metallic materials -- Determination of plane-strain fracture toughness
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.10 H 22
GB/T 4161-2007
Replacing GB/T 4161-1984
Metallic Materials –
Determination of Plane-Strain Fracture Toughness
(ISO 12737.2005, MOD)
Issued on. September 11, 2007 Implemented on. February 01, 2008
Issued by. General Administration of Quality Supervision, Inspection and Quarantine; Standardization Administration of PRC.
Table of Contents
Foreword ... 4
1 Scope ... 6
2 Normative References ... 6
3 Terms and Definitions ... 6
3.1 Plane-strain stress intensity factor (KI) ... 6
3.2 Plane-strain fracture toughness (KIc)... 7
3.3 Crack-plane orientation ... 7
3.4 Notch opening displacement (V) ... 7
4 Symbols and Designations ... 8
5 Principle ... 9
6 Apparatus ... 10
6.1 Testing machine and force measurement ... 10
6.2 Fatigue cracking preparation ... 10
6.3 Extensometer ... 10
6.4 Testing fixtures ... 11
7 Specimen Size, Shape and Preparation ... 11
7.1 Specimen size ... 11
7.2 Recommended specimen proportions ... 12
7.3 Specimen preparation and fatigue precracking ... 12
8 Test Program ... 13
8.1 Specimen measurement... 13
8.2 Specimen test temperature ... 14
8.3 Fixture measurement of bend specimen ... 14
8.4 Fracture appearance observation ... 14
9 Test Procedures ... 15
10 Calculation and Interpretation of Test Results ... 15
11 Test Report ... 15
Appendix A (Normative) Fatigue Precracking of KIc Fracture Toughness
Specimens ... 18
Appendix B (Normative) Bend Specimen Test ... 19
Appendix C (Normative) Compact Tensile Specimen Test ... 21
Appendix D (Informative) Test Fixtures ... 23
Appendix E (Informative) C-Shaped Tensile Specimen Test ... 25
Appendix F (Informative) Circular Compact Tensile Specimen Test... 30
Metallic Materials –
Determination of Plane-Strain Fracture Toughness
1 Scope
This Standard specifies the method for determining the plane-strain fracture toughness of the homogeneous metallic materials using a specimen that is notched and precracked by fatigue and subjected to slowly increasing crack displacement force.
2 Normative References
The provisions in following documents become the provisions of this Standard through reference in this Standard. For dated references, the subsequent amendments (excluding corrigendum) or revisions do not apply to this Standard, however, parties who reach an agreement based on this Standard are encouraged to study if the latest versions of these documents are applicable. For undated references, the latest edition of the referenced document applies.
GB/T 8170 Rules of Rounding off for Numerical Values
GB/T 12160 Calibration of Extensometers Used in Uniaxial Testing (GB/T 121602002, idt ISO 9513.1999)
GB/T 16825.1 Verification of Static Uniaxial Testing Machines – Part 1. Tension/Compression Testing Machines -Verification and Calibration of the Force-Measuring System (GB/T 16825.1-2002, idt ISO 7500-1.1999)
GB/T 20832 Metallic Materials -Designation of Test Specimen Axes in relation to Product Texture (GB/T 20832-2007, ISO 3785-2006, IDT)
3 Terms and Definitions
The following terms and definitions are applicable to this Standard.
3.1 Plane-strain stress intensity factor (KI)
Magnitude of the elastic stress field at the tip of the crack subjected to opening mode displacement (Mode I).
NOTE 3. For chevron notch. suggested notch root radius 0.025 mm maximum. Notch tip angle 90° maximum, A = C within 0.01W. Fatigue crack shall emerge on both surfaces of specimen.
Figure 2 – Crack Starter Notches and Maximum Permissible Notch/Crack
Envelope
6 Apparatus
6.1 Testing machine and force measurement
The testing machine shall be calibrated in accordance with GB/T 16825.1 and shall be of at least grade 1. The testing machine shall have provisions for automatic recording of the force applied to the specimen; alternatively, a computer data acquisition system may be used to record force and displacement for subsequent analysis. The combination of force-sensing device and recording system shall permit, so that the force FQ (as defined in Clause 10) to be determined from the test diagram with the accuracy of ± 1%.
6.2 Fatigue cracking preparation
When possible, the fatigue machine and force-indicating device shall be calibrated statically in accordance with GB/T 16825 and shall have a grade of at least 2. If the machine cannot be calibrated statically, the error of applied force shall be known to no greater than ± 2.5 %. Careful alignment of the specimen and test device is necessary to encourage straight fatigue cracks. The installment of test device shall be such that the stress distribution is uniform across the specimen thickness and symmetrical about the plane of the prospective crack.
6.3 Extensometer
The extensometer output shall represent the relative displacement of accuracy positions on two sides of the notch mouth. The design of the extensometer and knife edges shall allow free rotation of the points of contact between the extensometer and the knife edges.
The extensometer shall be calibrated in accordance with GB/T 12160, and shall be of at least grade 1; however, calibration shall be performed at least weekly during the time the extensometer is in use. Periodic verification of greater frequency may be required, depending on use and agreement between contractual parties.
Verification of the extensometer shall be performed at the temperature of test to ±5°C. The response of the extensometer shall correspond to the calibration apparatus to ± environmentally-conditioned state. Normally, specimens shall also be machined in this final state. However, for material that cannot be machined in the final condition, the final treatment may be carried out after machining, provided that the required specimen dimensions are met; however, the specimen dimension tolerance, shape and surface roughness shall meet the requirements (see Figures B.1 and C.1), and that full account is taken of the effects of specimen size on metallurgical condition induced by certain heat treatments, e.g. water quenching of steels.
7.3.2 Crack-plane orientation
The fracture toughness of a material is usually dependent on the orientation and direction of propagation of the crack in relation to the principal directions of metal working, grain flow or otherwise-produced texture. Orientation of the crack plane shall be decided before machining (see 7.3.3), identified in accordance with the prescribed coordinate systems (see 3.3) and recorded (see Clause 11).
7.3.3 Machining
Specimen sizes, shapes. dimensional tolerances and surface finishes shall be as given in Figures B.1 and C.1.
7.3.4 Fatigue precracking
Fatigue precracking normally shall be done at room temperature with the specimen in the finally heat-treated, mechanically-worked or environmentally-conditioned state in which it is to be tested. Different fatigue precracking temperatures and intermediate thermal/mechanical/environmental treatments between fatigue precracking and testing shall be used only when such treatments are necessary to simulate the conditions for a specific structural application; and required dimensions and tolerances on specimen size and shape can be maintained. Such fatigue precracking shall be performed according to the requirements of Appendix A.
8 Test Program
8.1 Specimen measurement
Measure specimen thickness (B) to the nearest 0.025 mm or to 0.1%, whichever is larger, at not less than three equally spaced positions along the anticipated crack extension path. Take the average of these measurements as the thickness.
Measure specimen width (W) to the nearest 0.025 mm or to 0.1%, whichever is larger, at not...
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