CN-121977951-A - Method for testing fatigue crack critical healing point of cyclic loading-multistage intermittent asphalt material

CN121977951ACN 121977951 ACN121977951 ACN 121977951ACN-121977951-A

Abstract

The invention provides a cyclic loading-multistage intermittent asphalt material fatigue crack critical healing point testing method, which aims at testing the critical point of self-healing failure of a material by gradually increasing the fatigue damage degree of an asphalt material, and comprises three stages, namely a non-destructive load cyclic loading stage, a multistage intermittent loading stage and a non-destructive loading stage; in addition, the damage density variation of the asphalt material after the fatigue crack is healed is used as an evaluation index of a healing critical point, the physical meaning of the damage density variation is that the crack area reduction ratio of the asphalt material before and after the fatigue crack is healed in an intermittent period, the smaller the numerical value is, the closer the damage density variation is to the material critical healing point under the current damage degree, the limitation of indirect evaluation of macroscopic performance depending on experience in the prior art is overcome, and technical support is provided for the healing capacity evaluation of the asphalt material and the crack resistance optimization design of the material.

Inventors

LI HUI
LIANG ZHENZHONG
TIAN WEIWEI
LUO XUE
LU JIABIN
LI CHUNLEI
ZHANG YUQING

Assignees

东南大学

Dates

Publication Date: 20260505
Application Date: 20260128

Claims (8)

1. A cyclic loading-multistage intermittent asphalt material fatigue crack critical healing point testing method, which is characterized by comprising the following steps of: S1, carrying out a non-destructive load cyclic loading stage, namely selecting a non-destructive load level of an asphalt material according to the type, load mode and loading working condition of the asphalt material, applying non-destructive load to the asphalt material for a plurality of times, and obtaining mechanical performance parameters of the material under the non-destructive load level; S2, carrying out a lossy load cyclic loading stage, namely selecting a lossy load level of the asphalt material according to the type, load mode and loading working condition of the asphalt material, applying a plurality of lossy loads to the asphalt material, and calculating mechanical performance parameters and damage density of the material under the lossy load level; S3, carrying out multi-stage intermittent and lossless loading, namely carrying out intermittent and lossless loading on the asphalt material for a plurality of times, gradually increasing the intermittent time of the asphalt material, and calculating the mechanical performance parameters of the asphalt material in the subsequent multi-stage intermittent stage; S4, acquiring initial modulus parameters of the asphalt material after the non-destructive load cyclic loading stage, and calculating the damage density variation of the asphalt material after the fatigue crack is healed by combining the damage density value after the destructive load cyclic loading.
2. The cyclic loading-multistage intermittent asphalt material fatigue crack critical healing point test method according to claim 1, wherein in step S2, calculating mechanical performance parameters of the material at a lossy loading level comprises calculating a fatigue crack length of the asphalt material, as follows: (1), wherein, c is the fatigue crack length of the asphalt material, r is the radius of the sample of the asphalt material; Is the apparent modulus of the asphalt material; Is the true modulus of the asphalt material.
3. The cyclic loading-multistage intermittent asphalt material fatigue crack critical healing point test method according to claim 2, wherein in step S2, the damage density of the asphalt material at the level of the damage load is represented by the ratio of the fatigue crack area of the test specimen to the cross-sectional area, as follows: (2), wherein: S c is crack area, S is cross section area of the sample; and (3) bringing the formula (1) into the formula (2) to obtain a damage density calculation formula, wherein the damage density calculation formula is as follows: (3)。
4. the cyclic loading-multistage intermittent asphalt material fatigue crack critical healing point test method according to claim 3, wherein in step S2, the damage density value of the asphalt material after undergoing the cyclic loading of the damage load is calculated according to the following calculation formula: (4), wherein: 、 The damage density and apparent modulus of the asphalt material after being subjected to the Nth damaged load cyclic loading are respectively shown.
5. The cyclic loading-multistage intermittent asphalt material fatigue crack critical healing point testing method according to claim 4, wherein, In step S3, mechanical performance parameters of the asphalt material in a subsequent multi-stage intermittent period are calculated, including calculating a damage density value of the asphalt material after multi-stage intermittent, where a calculation formula is as follows: (5), wherein: 、 Respectively representing the damage density and the apparent modulus of the asphalt material in the ith intermittent period of the multi-stage intermittent and non-destructive loading stages; Representing the true modulus of the intact asphalt material at the initial intact loading stage.
6. The method for testing fatigue crack critical healing point of asphalt material with cyclic loading-multistage intermittence according to claim 5, wherein in step S4, the variation of the damage density of asphalt material after the fatigue crack is healed The following formula is calculated: (6)。
7. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the processor implements the steps of the method of any one of claims 1 to 6 when the computer program is executed by the processor.
8. A computer readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor, implements the steps of the method according to any one of claims 1 to 6.

Description

Method for testing fatigue crack critical healing point of cyclic loading-multistage intermittent asphalt material Technical Field The invention belongs to the technical field of road engineering, and particularly relates to a cyclic loading-multistage intermittent asphalt material fatigue crack critical healing point testing method. Background The asphalt material is easy to generate microcracks under the action of cyclic load, and the self-healing characteristic of the asphalt material can enable the material to partially or completely recover the mechanical property after the material is subjected to proper recovery time, so that the degradation process of the material is delayed. Self-healing ability is essentially an inherent property of asphalt materials to resist the development of damage, the extent of which is significantly affected. In a low-damage state, the material realizes contact and closure of a microcrack interface through deformation recovery, so that a molecular chain segment is diffused and recombined, and healing strength is rebuilt. However, as the degree of injury increases, the ability to self-heal gradually decreases or even is lost, resulting in failure of the performance recovery mechanism. Therefore, the determination of the self-healing critical point of the asphalt material crack has important significance for delaying material performance degradation, prolonging service life and guiding material design. Currently, the prior art focuses on both self-healing performance testing and evaluation of asphalt materials. The test method for evaluating the self-healing performance of the asphalt material mainly comprises 1) a time scanning test, which is to apply cyclic shear load to the asphalt material to induce damage, set an intermittent period to heal, reload and compare the recovery degree of parameters such as complex modulus and the like to evaluate the healing performance, 2) a three-point bending fatigue healing test, which is to apply repeated bending load to the asphalt material under the condition of controlling strain or stress, introduce rest intermittence after fatigue damage, quantify the healing effect by comparing the rigidity of a test piece or the change of the fatigue life before and after intermittence, and 3) a direct stretching healing test, which is to apply cyclic load to the asphalt material in a stretching mode to generate microcracks, to rest intermittence after unloading, and to characterize the self-healing behavior by measuring the recovery rate of strength, fracture energy or elongation before and after healing. Regarding the self-healing evaluation index of the asphalt material, the characteristic of the healing performance of the existing asphalt material is mostly based on the recovery degree of macroscopic mechanical parameters, and common indexes comprise 1) a healing index which is generally defined as the ratio or the change rate of modulus before and after healing and is used for quantifying the recovery degree of the performance of the asphalt material, 2) a fatigue life recovery rate, the influence of healing on the durability of the material is evaluated by comparing the cycle times of the asphalt material reaching damage under the same load condition before and after healing, and 3) the change rate of dissipation energy is calculated based on the difference of the dissipation energy of the asphalt material in a damage stage and in a healing stage so as to indirectly reflect the healing effect of cracks. Although the prior art provides a plurality of methods for testing and evaluating the asphalt healing performance, the problems still exist that firstly, the prior test method is mostly used for comparing the healing capacities of different asphalt materials under specific working conditions, the crack critical healing point of the materials cannot be accurately determined, and the self-healing potential of the asphalt materials cannot be obtained. Secondly, the existing characterization indexes mainly depend on recovery conditions of macroscopic mechanical parameters such as modulus, energy and the like, and although the recovery conditions can indirectly reflect the recovery degree, the physical process of crack area reduction cannot be directly described, so that limitations exist in the aspect of characterization of the recovery mechanism of the asphalt material, and direct quantification indexes for the recovery behavior of the asphalt material are still lacking. Disclosure of Invention Aiming at the problems existing in the prior art, the invention provides a cyclic loading-multistage intermittent testing method for the critical healing point of the fatigue crack of the asphalt material, which is characterized in that the critical healing point of the fatigue crack of the asphalt material is tested by gradually increasing the damage level and testing the healing behavior of the asphalt material, the critical point of failure occurs in s