CN105973700B - The method that its fracture toughness is determined by the peak load of low-alloy high-strength steel - Google Patents
The method that its fracture toughness is determined by the peak load of low-alloy high-strength steel Download PDFInfo
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- CN105973700B CN105973700B CN201610277872.1A CN201610277872A CN105973700B CN 105973700 B CN105973700 B CN 105973700B CN 201610277872 A CN201610277872 A CN 201610277872A CN 105973700 B CN105973700 B CN 105973700B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0001—Type of application of the stress
- G01N2203/0003—Steady
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0017—Tensile
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
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- G01N2203/0067—Fracture or rupture
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Abstract
The present invention relates to a kind of methods determining its fracture toughness by the peak load of low-alloy high-strength steel, include the following steps：1）It makes identical size and the unilateral tensile test specimen with incipient crack of different fracture lengths, it is made to stitch high ratioα=a/WRespectively 0.1,0.2,0.3,0.4,0.5,0.6,0.7；2）The test specimen is placed on tensile testing machine or universal testing machine and carries out tension test, measures the peak load of each test specimen；3）After the peak load for measuring the test specimen, by formula（1）Obtain the nominal strength of the test specimenσ n；4）By formula（2）Obtain the equivalent fissure length of each test specimena e；5）It obtainsσ nWitha eAfterwards, formula is brought into（6）Carry out regression analysis, you can obtain the fracture toughness of low-alloy high-strength steelK C.The method of the present invention form is simple, is very easy to realize under the conditions of conventional test room, convenient for promoting, and has enough accuracy.
Description
Technical field
The invention belongs to metal material performance detection technical field more particularly to a kind of maximum lotuses by low-alloy high-strength steel
Carry the method for determining its fracture toughness.
Background technology
Currently, the Fracture of Metal Material conformance testing specifications of domestic and foreign current, as country of the People's Republic of China (PRC) marks
It is accurate --- metal material Plane Strain Fracture ToughnessK ICTest method（GB/T 4161-2007）, country of the People's Republic of China (PRC) mark
It is accurate --- the uniform tests method of the quasi-static fracture toughness of metal material（GB/T 21143-2007）, state of the People's Republic of China (PRC)
Standard --- metal material shows cracked tension sample fracture tough test method for family（GB/T 7732-2008）, U.S. ASTM
E399, Europe BS EN ISO etc., have stringent limitation to test specimen pattern, loads fixture, load mode, pilot system：（1）It surveys
There are strict requirements for the size of sample of having a try, and fracture length, sample thickness and the ligament height of sample must be more than certain numerical value；If
It is tested using expected dimension, measures index and be unsatisfactory for size regulation, also need to re-start experiment；（2）Metal initial crackle
Formation, need carry out fatigue test；（3）It only can determine that metal material Plane Strain Fracture Toughness, and the gold under plane stress
Belong to fracture toughness not provide also；（4）The geometry pattern of test sample uses three-point bending and edge splitting mostly, to test specimen pattern
There is stringent limitation with loads fixture and load mode etc.；（5）Experiment palpus test load-displacement full curve, uses extensometer etc.
Equipment requires pilot system relatively high.Therefore, current techniques measure the fracture toughness needs of Hi-Stren steel strictly
Test specimen and complicated test equipment are processed, and how to determine the fracture toughness of high-strength steel under the conditions of common lab, is become
Technical barrier urgently to be resolved hurrily.
For metallographictest, most facile during experiment is its peak load, relatively simple test specimen
Form is drawing plate sample.And test peak load and do not need complex device, it is extremely low to test requirements document.By single-edge crack drawing plate
Experimental test obtains peak load and is very easy to realize under the conditions of conventional test room, and method is easy and convenient for promoting.
Invention content
In view of the above-mentioned problems, the present invention provides a kind of side determining its fracture toughness by the peak load of low-alloy high-strength steel
Method can solve current high-strength steel fracture toughness test problem.This method form is simple, is very easy under the conditions of conventional test room
Realize convenient for promoting, and there is enough accuracy.
In order to solve the above technical problems, the invention is realized by the following technical scheme：
By long-term practical studies, has devised and a kind of its fracture toughness is determined by the peak load of low-alloy high-strength steel
Method, include the following steps：
1）It makes identical size and the unilateral tensile test specimen with incipient crack of different fracture lengths, makes its fracture length
With the ratio of height of specimen --- stitch high ratioα=a/WRespectively 0.1,0.2,0.3,0.4,0.5,0.6,0.7；
In formulaaFor incipient crack length,WFor height of specimen,αTo stitch high ratio；Height of specimenW30~50mm, test specimen is taken to have
Imitate lengthLTake 50~70mm, specimen thicknessBIt is the length of part of the test specimen in addition to loading head to take 5~15mm, effective length.
2）The test specimen is placed on tensile testing machine or universal testing machine and carries out tension test, measures each test specimen
Peak load；
The experiment can be completed under the conditions of ordinary test room, wherein the loading head of test specimen must be firmly secured on testing machine
On lower collet, and ensure the forced area of test specimen by height of specimenWWith effective lengthLIt is corresponding；
Tension test can refer to《Metal material stretching test part 1：Room temperature test method》(GB/T 228.1-
2010) schedule speed is at the uniform velocity loaded in specification, is loaded into test specimen rupture failure always, records the maximum lotus of each test specimen
It carries.
3）After the peak load for measuring the test specimen, by formula（1）Obtain the nominal strength of the test specimenσ n；
（1）
In formula,P UTFor peak load；BFor specimen thickness；aFor incipient crack length, Δa pIt is split for peak load is corresponding
Tip equivalent plastic area is stitched, experiment measured length value is taken, or 2~6mm of empirical value that camera shooting statistics obtains in experiment；λ
Coefficient is influenced for stress distribution shape,λIn 0.90~0.85 value.
4）By formula（2）Obtain the equivalent fissure length of each test specimena e；
（2）
（3）
（4）
（5）
In formula,B(α) it is geometry influence coefficient,Y ( )(α) influenced for the geometry in the case of single-edge crack uniaxial direct tensile
The factor,Y ( )(α) be single-edge crack simple bending in the case of geometry impact factor,W 1= W - a 0。
5）It obtainsσ nWitha eAfterwards, formula is brought into（6）Carry out regression analysis, you can obtain the fracture toughness of low-alloy high-strength steelK C；
（6）
In formula,σ UTFor ultimate strength.
The present invention has following positive beneficial effect：
（1）The present invention only needs experimental test to obtain the peak load of test specimen, is very easy under the conditions of conventional test room real
Existing, method is easy and convenient for promoting.
（2）Small-size test piece can be used in the present invention, and sample dimensions are not required to meet existing specification measurement Linear Elasticity Fracture condition
Lower height, thickness, incipient crack length etc. will be more than the rigors of certain numerical value.
（3）Formation for the initial crack of fracture toughness test, the present invention is not required to be formed using fatigue test, and only needs
Using line cutting technology joint-cutting, the difficulty in processing sample crack is greatly reduced, alleviates corresponding workload.
（4）The present invention can be relatively thin using the thickness of sample, is not required to meet existing specification plane strain condition, and can obtain and answer
With the fracture toughness of the high-strength steel of the more extensive plane stress condition of rangeK C。
（5）The present invention uses unilateral tensile sample, after using current specifications for measuring cutting used in intensity
Pole sample, and measure three-point bending beam sample and edge splitting sample etc. used in fracture toughness, sample processing and experiment
Loading equipemtn is simplified, and saves testing cost.
Description of the drawings
Specific embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings, wherein：
Fig. 1 is test specimen structural schematic diagram used in the present invention；
Fig. 2 is to be returned to determine fracture toughness (Δ by embodiment test dataa p = 4mm；λ =0.85)；
Specific implementation mode
Technical solution of the present invention is clearly completely described below in conjunction with attached drawing, it is clear that described example is only
The schematical part specific implementation mode of the present invention, is not limited to the scope of the present invention, any those skilled in the art
The equivalent variations made under the premise of not departing from present inventive concept and principle and modification should all belong to the model that the present invention protects
It encloses.
Embodiment 1
Referring to Fig. 1, tensile sample schematic diagram used in the present embodiment makes identical size and different fracture lengthsaIt is unilateral
Drawing plate test specimen with incipient crack, sample dimensionsW=40mm,B=10mm,L=60mm, camber section height are
The size of 20mm, rectangle clamping head is：70mm × 80mm.
The high ratio of seam of sample is made respectivelya/W=0.1,0.2,0.3,0.4,0.5,0.6,0.7 7 groups of samples, every group of system
Make 5 samples, amounts to 35 samples.Wherein the formation of incipient crack must use wire cutting technology, fracture width that must be less than 0.25mm,
Fatigue crack is formed without carrying out fatigue test.
Experiment is pressed《Metal material stretching test part 1：Room temperature test method》In specifications such as (GB/T 228.1-2010)
Schedule speed is at the uniform velocity loaded, and is loaded into test specimen rupture failure always.The peak load of each test specimen is recorded during experiment.
After the peak load for measuring each test specimen, by formula（1）Calculate the nominal strength of each test specimenσ n。
The equivalent fissure length of each test specimena eIt can be by formula（2）、（3）、（4）、（5）It calculates.
It obtains differentσ nWitha eAfterwards, it brings following formula (6) into and carries out regression analysis, you can while showing that the limit of high-strength steel is strong
Degreeσ UTAnd fracture toughnessK C。
Referring to Fig. 2, determine that the yield strength of Hi-Stren steel and fracture are tough by embodiment specimen test data regression
Degree.When considering the influence of yield region, using the ultimate strength for the Hi-Stren steel that the method for the present invention determinesσ UT=577.82 -
607.20 MPa, the product quality certificate with its Anyang Steel ＆ Iron Corporation（Number：20150820148）The pole provided
Limit intensityσ UT=598MPa coincide good.Under plane stress conditionK C = 60.96-65.28 MPa·m1/2。
The experiment of table 1 determines the ultimate strength of low-alloy high-strength steelσ UTWith fracture toughnessK C
。
To the above description of disclosed embodiment, those skilled in the art is enable to realize or use the present invention, it is apparent that
Described embodiment is only the schematical part specific implementation mode of the present invention, is not limited to the scope of the present invention, appoints
The equivalent variations and modification what those skilled in the art is made under the premise of not departing from present inventive concept and principle, should all
Belong to the scope of protection of the invention.
Claims (3)
1. a kind of method determining its fracture toughness by the peak load of low-alloy high-strength steel, which is characterized in that including following step
Suddenly：
1) it makes identical size and the unilateral tensile test specimen with incipient crack of different fracture lengths, makes its fracture length and examination
The ratio of part height --- seam height is respectively 0.1,0.2,0.3,0.4,0.5,0.6,0.7 than α=a/W；
A is incipient crack length in formula, and W is height of specimen, and α is to stitch high ratio；
2) test specimen is placed on tensile testing machine or universal testing machine and carries out tension test, measure the maximum lotus of each test specimen
It carries；
3) after the peak load for measuring the test specimen, the nominal strength σ of the test specimen is obtained by formula (1)n；
In formula, PUTFor peak load；B is specimen thickness；A is incipient crack length, Δ apFor the corresponding crack point of peak load
Equivalent plastic area is held, experiment measured length value is taken；λ, which is stress distribution shape, influences coefficient, and λ is in 0.90-0.85 values；
4) the equivalent fissure length a of each test specimen is obtained by formula (2)e；
In formula, B (α), which is geometry, influences coefficient；
5) σ is obtainednWith aeAfterwards, it brings formula (6) into and carries out regression analysis, you can obtain the fracture toughness K of low-alloy high-strength steelC；
In formula, σUTFor ultimate strength.
2. the method for determining its fracture toughness by the peak load of low-alloy high-strength steel according to claim 1, feature exist
In：The height W of test specimen made by step (1) is 30-50mm, effective length L is 50-70mm, thickness B is 5-15mm, effectively long
Degree is the length of part of the test specimen in addition to loading head.
3. the method for determining its fracture toughness by the peak load of low-alloy high-strength steel according to claim 1, feature exist
In：Step (4) B (α) is obtained by formula (3), (4), (5)：
In formula, Y(i)(α) is the geometry impact factor in the case of single-edge crack uniaxial direct tensile, Y(ii)(α) is single-edge crack simple bending feelings
Geometry impact factor under condition, W1=W-a.
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| CN101566542A (en) * | 2009-05-27 | 2009-10-28 | 中国科学院力学研究所 | Method for extracting fracture toughness of materials |
| CN102519805A (en) * | 2011-12-01 | 2012-06-27 | 三峡大学 | Method and system for testing fracture toughness of incompact soil body |
| CN103604694A (en) * | 2013-10-14 | 2014-02-26 | 中国石油天然气集团公司 | Method for measuring fracture toughness of pipeline steel by using unilateral notched tensile test |
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