CN103115827B - Asphalt repeats to load four-point bending stiffness modulus method of testing - Google Patents
Asphalt repeats to load four-point bending stiffness modulus method of testing Download PDFInfo
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- CN103115827B CN103115827B CN201310052796.0A CN201310052796A CN103115827B CN 103115827 B CN103115827 B CN 103115827B CN 201310052796 A CN201310052796 A CN 201310052796A CN 103115827 B CN103115827 B CN 103115827B
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Abstract
The invention discloses a kind of asphalt to repeat to load four-point bending stiffness modulus method of testing, belong to field of road.The feature of the method: in four-point bending load repeat function process, to measure in the middle part of test specimen the difference of 1/3 maximum defluxion produced under each load action across the neutral surface within the scope of footpath and minimum amount of deflection, and calculate the maximum stretching strain of test specimen on this basis, calculate actual flexion stiffness modulus and the bending-type panel Decay Law of test specimen under four-point bending Repeated Loading of test specimen under load action each time further.Stiffness modulus method of testing of the present invention overcomes the defect that prior art can only obtain the average bending-type panel of whole test specimen, the actual Decay Law that asphalt accurately and reliably repeats to load four-point bending stiffness modulus and asphalt bending-type panel under Repeated Loading can be obtained, there is good application value.
Description
Technical field
The present invention relates to field of road, specifically a kind of asphalt repeats to load four-point bending stiffness modulus method of testing.
Background technology
In the fatigue behaviour of asphalt is evaluated, conventional Experimental Method in Laboratory is the torture test of asphalt four-point bending, and the bending-type panel that the end condition of torture test is test specimen decays to 50% of initial value, if the bending-type panel of test specimen under four-point bending load repeat function accurately can not be obtained, the accuracy of the evaluation of fatigue performance of asphalt mixture will be had influence on.Traditional asphalt four-point bending torture test is in the test of test specimen bending-type panel, suppose that the bending-type panel of whole test specimen under load repeat function is equal all the time, whole test specimen maximum defluxion is measured poor in process of the test, and using the average bending-type panel of whole test specimen that calculates the on this basis bending-type panel as moment of flexure maximum region in test specimen.Obviously, this method is irrational.In the middle part of test specimen 1/3 across moment of flexure within the scope of footpath maximum and all the time in equal this region i.e. tension maximum and equal all the time, so this region material bending-type panel along with load repeat function decay amount maximum and identical, the bending-type panel of this region material is less than the average bending-type panel of whole test specimen, and namely the bending-type panel actual attenuation speed of test specimen is faster than classic method.Therefore, the method for testing of existing asphalt bending-type panel has influence on the accuracy of fatigue performance of asphalt mixture evaluation.
Summary of the invention
Technical assignment of the present invention is for above-mentioned the deficiencies in the prior art, provides a kind of asphalt to repeat to load four-point bending stiffness modulus method of testing.Utilize the method to obtain actual Decay Law that asphalt accurately and reliably repeats to load four-point bending stiffness modulus and asphalt bending-type panel under Repeated Loading.
Technical assignment of the present invention realizes in the following manner: asphalt repeats to load four-point bending stiffness modulus method of testing, be characterized in four-point bending load repeat function process, to measure in the middle part of test specimen the difference of 1/3 maximum defluxion produced under each load action across the neutral surface within the scope of footpath and minimum amount of deflection, and calculate the maximum stretching strain of test specimen on this basis, calculate actual flexion stiffness modulus and the bending-type panel Decay Law of test specimen under four-point bending Repeated Loading of test specimen under load action each time further.
Preferably to utilize in the middle part of LVDT sensor measurement test specimen the difference of 1/3 maximum defluxion produced under each load action across the neutral surface within the scope of footpath and minimum amount of deflection.
In order to ensure that the maximum defluxion difference of test specimen under load action of surveying is the maximum and region that material modulus is equal of test specimen flexural tensile stress, the preferred following specific implementation step of said method:
1) LVDT sensor is installed
In the middle part of the asphalt beam specimen prepared, 1/3 installs LVDT sensor across footpath place;
2) four-point bending reloading applies
According to test request, start to load after setting load control mode, Loaded contact analysis, frequency;
3) experimental data processing
The peak load of each applying collected by collecting device and the maximum defluxion that test specimen produces under load action poor, calculate the bending-type panel of asphalt test specimen under each four-point bending load action and analyze the Decay Law of test specimen bending-type panel in four-point bending Repeated Loading process.
Step 1) in when LVDT sensor is installed, the support installing LVDT is by being pasted onto in the middle part of beam specimen 1/3 across footpath place neutral surface is bolted on test specimen; The sheet metal contacted with the gauge head of LVDT, is bolted on test specimen by two of being pasted onto on the neutral surface of test specimen span centre.
Asphalt of the present invention repeats to load four-point bending stiffness modulus method of testing and compared with prior art has following outstanding beneficial effect:
(1) the method is according to choosing the test section of the maximum and region that material modulus is equal all the time of flexural tensile stress in test specimen as test specimen stiffness modulus under four-point bending Repeated Loading, the actual flexion stiffness modulus of test specimen under four-point bending Repeated Loading and Decay Law thereof can be obtained, overcome false whole test specimen material modulus under Repeated Loading in prior art identical all the time, the defect of the average bending-type panel of whole test specimen can only be obtained;
(2) this method solve the fatigure failure limit in existing asphalt mixture fatigue testing and judge inaccurate problem.
Accompanying drawing explanation
Accompanying drawing 1 is the force diagram of test specimen under four-point bending load action and moment curve in embodiment;
Accompanying drawing 2 is LVDT installations diagram of test specimen in embodiment;
Accompanying drawing 3 is that embodiment Asphalt Mixture test specimen repeats to load four-point bending stiffness modulus and the relation curve loading number of times.
Mark in accompanying drawing represents respectively:
1. test specimen; 2.LVDT sensor; 3.LVDT mounting bracket; 4. with LVDT gauge head contacting metal plate; 5, the set bolt of 6.LVDT mounting bracket; 7. with the set bolt of LVDT gauge head contacting metal plate.
Embodiment
Repeat to load four-point bending stiffness modulus method of testing with specific embodiment to asphalt of the present invention with reference to Figure of description to be described in detail below.
Embodiment
Asphalt of the present invention repeats loading 4 method for testing fatigue, comprises the following steps (for middle grain formula bituminous concrete AC-25):
A) LVDT sensor is installed
Across footpath place, LVDT sensor 2 is installed at the middle part 1/3 of the asphalt beam specimen 1 prepared.
As shown in Figure 2, the support 3 installing LVDT sensor 2 is by being pasted onto in the middle part of beam specimen 1/3 across the set bolt 5 on footpath place neutral surface, 6(A, A ' two point) be fixed on test specimen 1; The sheet metal 4 contacted with the gauge head of LVDT sensor 2, by being pasted onto the set bolt 7(B point on the neutral surface of test specimen span centre) be fixed on test specimen 1.
The preparation method of test specimen 1 is known technology.
B) four-point bending reloading applies
According to test request, start to load after setting load control mode, Loaded contact analysis, frequency.What this test adopted is control strain method, and have employed altogether 70 μ ε, 100 μ ε, 200 μ ε, 300 μ ε totally 4 strain levels, Loaded contact analysis is half-sine wave, and loading frequency is 10Hz.Stressed and the moment of flexure of test specimen as shown in Figure 1.
C) experimental data processing
The peak load of each applying collected by collecting device and the maximum defluxion that test specimen produces under load action poor
then through type (1) calculates the maximum stretching strain in test specimen bottom surface, finally by the bending-type panel of formula (2) calculation testing piece under each load action, by to repeating the stiffness modulus data that obtain of repeated loading and loading number of times, adopt excel software can draw the Decay Law of test specimen bending-type panel in four-point bending Repeated Loading process, as shown in Figure 3.
formula (1)
formula (2)
In formula:
The maximum stretching strain in=test specimen bottom surface;
=maximum defluxion difference (m);
The height (m) of h=test specimen;
The spacing of the spacing (m) of n=standing screw, i.e. A, A ' two;
The peak load (N) that P=applies;
L=test specimen across footpath (m);
E=bending-type panel (N/m
2);
The width (m) of b=test specimen.
Claims (4)
1. asphalt repeats to load four-point bending stiffness modulus method of testing, it is characterized in that:
In four-point bending load repeat function process, to measure in the middle part of test specimen the difference of 1/3 maximum defluxion produced under each load action across the neutral surface within the scope of footpath and minimum amount of deflection, and calculate the maximum stretching strain of test specimen on this basis, calculate actual flexion stiffness modulus and the bending-type panel Decay Law of test specimen under four-point bending Repeated Loading of test specimen under load action each time further
Maximum stretching strain and bending-type panel are calculated by formula (1), formula (2) respectively:
formula (1)
formula (2)
In formula:
the maximum stretching strain in=test specimen bottom surface;
=maximum defluxion difference (m);
The height (m) of h=test specimen;
The spacing (m) of n=standing screw;
The peak load (N) that P=applies;
L=test specimen across footpath (m);
E=bending-type panel (N/m
2);
The width (m) of b=test specimen.
2. asphalt according to claim 1 repeats to load four-point bending stiffness modulus method of testing, it is characterized in that: the difference utilizing in the middle part of LVDT sensor measurement test specimen 1/3 maximum defluxion produced under each load action across the neutral surface within the scope of footpath and minimum amount of deflection.
3. asphalt according to claim 2 repeats to load four-point bending stiffness modulus method of testing, it is characterized in that comprising the following steps:
1) LVDT sensor is installed
In the middle part of the asphalt beam specimen prepared, 1/3 installs LVDT sensor across footpath place;
2) four-point bending reloading applies
According to test request, start to load after setting load control mode, Loaded contact analysis, frequency;
3) experimental data processing
The peak load of each applying collected by collecting device and the maximum defluxion that test specimen produces under load action poor, calculate the bending-type panel of asphalt test specimen under each four-point bending load action and analyze the Decay Law of test specimen bending-type panel in four-point bending Repeated Loading process.
4. asphalt according to claim 3 repeats to load four-point bending stiffness modulus method of testing, it is characterized in that: step 1) in when LVDT sensor is installed, the support installing LVDT is by being pasted onto in the middle part of beam specimen 1/3 across footpath place neutral surface is bolted on test specimen; The sheet metal contacted with the gauge head of LVDT, is bolted on test specimen by two of being pasted onto on the neutral surface of test specimen span centre.
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Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104915480B (en) * | 2015-05-22 | 2018-02-13 | 山东省交通科学研究院 | Semi-rigid asphalt pavement crack damage state determines method |
| CN105043896B (en) * | 2015-06-18 | 2018-06-05 | 宁波东方电缆股份有限公司 | The test method of underwater cable bending stiffness |
| CN105203414A (en) * | 2015-09-24 | 2015-12-30 | 长沙理工大学 | Testing method for dynamic modulus of bituminous mixture |
| CN107389475B (en) * | 2017-08-21 | 2019-10-11 | 西南交通大学 | Asphalt interlaminar shear strength test device based on four_point bending beam method |
| CN108956325B (en) * | 2018-07-05 | 2021-04-09 | 广西大学 | Method for measuring bending moment strength of concrete |
| CN109724863A (en) * | 2018-12-11 | 2019-05-07 | 南京工程学院 | Apply the device and its test method of constant load for cement-based material test specimen |
| CN110658086B (en) * | 2019-08-31 | 2022-05-27 | 长沙理工大学 | Asphalt pavement load response analysis method considering tension-compression modulus difference |
| CN112697608B (en) * | 2020-12-10 | 2022-09-13 | 太原理工大学 | Method for judging plastic bending resistance bearing capacity of full section of steel member under bidirectional bending |
| CN113670709A (en) * | 2021-08-30 | 2021-11-19 | 河南省交通规划设计研究院股份有限公司 | Method for evaluating fatigue resistance of waterproof adhesive layer and bridge deck pavement composite structure |
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| US4895027A (en) * | 1988-01-19 | 1990-01-23 | Battelle Development Corporation | Determining plane strain fracture toughness and the J-Integral for solid materials using stress field modified miniature specimens |
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|---|---|---|---|---|
| US4895027A (en) * | 1988-01-19 | 1990-01-23 | Battelle Development Corporation | Determining plane strain fracture toughness and the J-Integral for solid materials using stress field modified miniature specimens |
| CN102252916A (en) * | 2011-04-25 | 2011-11-23 | 山东省交通科学研究所 | Method for testing fatigue damage of inorganic binding material stabilizing material |
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