Dynamic Tension Tests Research Articles

Seismic analysis of asphalt concrete core rockfill dams considering the bimodulus effect

In China, with the extensive development of pumped storage power stations, asphalt concrete core rockfill dams have become the preferred dam type because of their good deformation adaptability and impermeability. In seismic-prone western regions of China, the seismic safety of asphalt concrete cores is particularly important. However, asphalt concrete materials used in hydraulic engineering exhibit significant differences in their tensile and compressive moduli under low-temperature conditions, which has not been considered in existing constitutive models. In this study, a dynamic constitutive model considering the bimodulus effect of asphalt concrete was developed on the basis of dynamic tension and compression tests. Using this model, the influence of the bimodulus characteristics on the dynamic response of the core was investigated. The results indicate that a bimodulus constitutive model can effectively simulate the stress‒strain relationship of asphalt concrete materials at low temperatures. Compared with the bimodulus model, the use of the monomodulus model for calculations results in a significant decrease in compressive stress and a substantial increase in tensile stress of the core. Specifically, using the tensile and compressive monomodulus models led to maximum reductions in tensile stress of 42.9 % and an increase by 336.8 %, respectively. Neglecting the bimodulus effect may lead to misjudgment of the damage area, so the bimodulus effect on the seismic safety of dam cores should not be ignored.

Dynamic tensile properties of straw fiber reinforced rubber concrete

Rubber concrete (RC) has received a great deal of attention in the field of construction materials, owing to its outstanding mechanical properties and potential for waste recycling. Despite extensive research on the mechanical behavior of RC, there remains a notable gap in understanding the dynamic characteristics of fiber reinforced rubber concrete. This study specifically focuses on the dynamic characteristics of RC with straw fibers as reinforcement. The investigative methodologies employed scanning electron microscope (SEM) analysis, computed tomography (CT) scans, and split Hopkinson pressure bar (SHPB) with a high-speed camera system for dynamic tension tests. The CT experimental findings reveal a uniform distribution of rubber particles and straw fibers within the concrete matrix. The dynamic tensile strength of straw fiber reinforced rubber concrete (SFRC) demonstrates a linear correlation with increasing loading rates. The results showed that SFRC-1.5 had 4.8 % lower static strength and 15 % lower dynamic strength than RC without straw fibers at the load rate of 110 GPa/s. In terms of energy, the dissipated energy density increased by 5.36 % at this loading rate. In addition, at a straw content of 2.5 %, the initial cracking time reached a maximum value of 220 μs. The highest level of shear resistance was observed at this content. This study emphasizes the heightened capability of SFRC under dynamic loading forces, thereby contributing to its potential application in green civil engineering and other related fields.

Experimental study on dynamic direct tensile performances of steel fiber-reinforced RPC at high strain rates

Reactive power concrete (RPC) exhibits excellent mechanical properties, makes it great potential for applications. RPC has gained increasing attention in academic and engineering areas and has been used in fields such as anti-explosion engineering. The insufficient tensile strength of RPC is one of the critical reasons for its structural failure. Existing studies revealed that the strain rate effect of concrete under dynamic tension is stronger than that under dynamic compression. The existing research focuses either on dynamic splitting and spalling tests, or dynamic uniaxial tensile properties with a strain rate of 0–100/s, neither of which are representative of the effect of RPC subject to explosion. In addition, the study of the dynamic uniaxial tensile constitutive model of RPC has not been reported in the existing research. To solve the existing limitations, this study conducted dynamic direct tension tests on steel fiber-reinforced RPC with a predefined strain rate higher than 100 s−1 using a Split Hopkinson Tension Bar (SHTB) apparatus. RPC dumbbell-shaped samples, including plain RPC and steel fiber-reinforced RPC (SFRPC) with 1 % and 2 % fiber volumetric fractions, were tested at high strain rates of 98–528 s−1. Based on the test results of this study and those derived from existing publications, the relationship between dynamic direct tensile properties, steel fiber fraction, and strain rate was quantitatively analyzed, and corresponding empirical formulae were proposed. To meet the demand for numerical analysis on RPC structures subjected to explosive forces, a dynamic tensile stress-strain model for steel fiber-reinforced RPC considering steel fiber, strain rate, and dynamic toughness, was established.

Dynamic tensile properties of a novel high strength and high toughness bolt steel: Constitutive models and microstructures

With the continuous increase of depth in underground engineering, rock bursts or rock explosions can cause instantaneous shock load and result in rock engineering disasters. To solve these problems, a novel high strength and high toughness (HSHT) bolt steel with constant resistance and large deformation is proposed. This study aims to investigate the dynamic constitutive models and microstructure of HSHT steel under extreme loading conditions. A series of dynamic tension tests were conducted using a Split Hopkinson Tensile Bar (SHTB) system with a high-speed camera. The results revealed that the HSHT steel exhibited a positive strain rate effect. As the strain rate increased from 1000 s−1 to 5000 s−1, the yield strength and ultimate strength of the HSHT steel increased gradually. However, no obvious changes in the uniform elongation. Specifically, the yield strength, tension strength, and uniform elongation of strain rate at 5000 s−1 were 1100 MPa, 1170 MPa, and 30%, respectively. According to the results of the SHTB tests, a modified Johnson-Cook model was proposed. Additionally, we investigated the microstructure of HSHT steel at a high strain rate through microscopic characterization techniques. A large number of fine and deep dimples were observed near the fracture of HSHT steel under dynamic loading. Moreover, the HSHT steel demonstrates a significant presence of nano-twins, which effectively impedes crack propagation both within the grain interior and along grain boundaries. The above findings reveal the relationship between mechanical behavior and microstructure in HSHT steel within dynamic loading conditions, providing valuable insights for the design of HSHT steel in underground engineering.

Demulsification efficiency and mechanism of hydrophobic carbon chains modified hyperbranched polyethylenimide on oil-in-water emulsion

A series of amphiphilic hyperbranched polyethylenimine (HPEI-Cn) with different length hydrophobic carbon chains were synthesized by amidation modification of hyperbranched polyethylenimine (HPEI), which can be used for separation of oil-in-water emulsion. The demulsification effect of HPEI-Cn under different demulsifier concentration, temperature, settling time and pH value were evaluated by bottle test method. The results indicated that the demulsification efficiency (DE) of HPEI-Cn increased with the increase of graft length of carbon chain. Encouragingly, the HPEI-C16 had the characteristics of small amount (50 mg/L), short settling time (30 min) and wide temperature adaptation range (20–60 °C). Through three-phase contact angle tests (CA), dynamic interfacial tension tests (IFT), elastic modulus analysis, Zeta potential and microscope observation, the demulsification mechanism of HPEI-Cn was systematically revealed. The excellent DE of HPEI-C16 was attributed to the high interfacial activity and appropriate length of hydrophobic groups. On the one hand, the high interfacial activity drives hyperbranched macromolecules to rapidly diffuse and adsorb to the oil-water interface. On the other hand, it contains appropriate hydrophobic carbon chains C16 to flocculate and coalesce oil droplets, thus achieving efficient demulsification.

Tuning rheology and fire-fighting performance of protein-stabilized foam by actively switching the interfacial state of the liquid film

Biomolecular self-assembly has lately emerged as an intriguing method for creating stable gas-liquid dispersions with unique functional characteristics. In this work, protein-metal coordination complexes were designed as the stabilizer for generating ultrastable fire-fighting foam and creating interfacial architectures that were actively switched between “rigid” and “mobile” interfacial states of liquid films in response to changes in pH and bulk solution compositions (metal ions or alkyl polyglycosides). The reflected light interferometric technique was used to check interfacial states, and the foaming kinetics and rheological response of aqueous solution and liquid foam were investigated by dynamic surface tension tests and oscillatory rheology analysis. The results showed that liquid foams with mobile films with lower yield limits had a faster spreading rate to cover the burning oil, liquid foams with semi-rigid films cannot extinguish fires due to interfacial instability, and the enhanced rheology of the foam with rigid films established a robust and impenetrable barrier to effectively suppress fuel evaporation and combustion. A new correlation between interfacial properties and the fire-fighting performance of foam was proposed, which showed that the fire-extinguishing time of foam could be well correlated by the interfacial states or film lifetime rather than classical thermodynamics entry, spreading, and bridging coefficients (ESB coefficients).

Calibration and application of damage and rate-dependent constitutive model for SPCE steel

The SPCE steel demonstrates favorable deep-drawing and forming properties, leading to its widespread use in industrial production. However, when subjected to complex loads, it becomes crucial to develop a constitutive model that accurately characterizes its mechanical properties. Such a model serves as the foundation for engineering design and safety assessment. Both quasi-static tension tests and high strain rate tension tests were conducted on SPCE steel samples using static and dynamic tension testing machines at room temperature. The resulting test data was used to introduce three dynamic increase factor indicators (DIFs) that quantify the strain rate effect on SPCE steels. Additionally, the fracture morphology of typical post-test specimens was analyzed using a scanning electron microscope (SEM) to demonstrate the strain rate effect on the mechanical properties of SPCE steels from a microscopic perspective, revealing ductile fracture as the primary fracture mechanism. A double-power plastic constitutive model was developed to describe the material's tensile mechanical behavior prior to necking. Simulation analysis was performed to validate the model, and the parameters of the Ductile damage model were identified based on the simulation data. The proposed constitutive model underwent numerical verification, demonstrating good consistency between the simulation and experimental results. Furthermore, the same constitutive model was applied to process the test data of HC650 steel using the same methodology. The conclusion drawn from this analysis aligned with that of SPCE steel, confirming the suitability of the proposed constitutive model for characterizing the mechanical behavior of steels without yielding a platform under different strain rates.

Effect of thickness on the behavior of aggregate-asphalt-aggregate film subjected to dynamic shearing and uniaxial tension

Although the asphalt-aggregate interface and its film thickness present important effect on performance of asphalt mixtures, there are no effective methods to accurately evaluate those factors. This study focuses on the effect of aggregate-asphalt-aggregate thickness on the shearing and tension mechanical properties of the asphalt-aggregate by using aggregate developed Dynamic Shearing Rheometer (DSR). Utilizing microscopic techniques to observe the surface morphology of different aggregates and the adhesion state of asphalt-aggregate micro-interface zone, and then carried out the dynamic shear rheological test and uniaxial tension test analysis of aggregate-asphalt-aggregate system under different interlayer thickness and different aggregate adhesion conditions. Results indicate that the developed DSR using aggregate plates is a helpful device to simulate the interface in asphalt mixtures. Differences in microscopic morphology and chemical adhesion have a significant impact on the shearing and tension behavior of aggregate-asphalt-aggregate system. The influence of microscopic interaction between aggregate and asphalt on the mechanical behavior of asphalt is dependent on temperature, frequency, interlayer thickness, and loading pattern. The thickness of the interlayer shows different modes subjected to loading, which is reflected as that film thinning means modulus softening during shearing loading and film thinning means modulus strengthening during tension loading.

Experimental and numerical investigation on the dynamic shear failure mechanism of sandstone using short beam compression specimen

In this study, a novel testing method is proposed to characterize the dynamic shear property and failure mechanism of rocks by introducing the short beam compression (SBC) specimen into the split Hopkinson pressure bar (SHPB) system. Firstly, the stress distribution of SBC specimen is comprehensively analyzed by finite element method (FEM), and the results show that the optimal notch separation ratio of SBC specimen is C/H = 0.2 to achieve successful dynamic simple-shear tests. Then, dynamic shear tests are conducted on sandstone using the SBC-SHPB method. Via careful pulse shaping technique, the dynamic force balance is guaranteed for SBC specimens, and the testing results show that the dynamic shear strength of sandstone is significantly rate-dependent. Combining the results of dynamic compression and tension tests, the failure envelopes of sandstone under different loading rates are obtained in the principle stress plane. It is found that the failure envelope of sandstone constantly expands outwards with increasing loading rate. Moreover, the energy partition of SBC specimen is quantified by virtue of high-speed digital image correlation (DIC) technique. The results show that the kinetic energy portion is non-negligible, and the shear fracture energy increases with increasing loading rate. In addition, the microscopic shear cracking mechanism of SBC specimen is analyzed by the thin section observation: the intra-granular (TG) fracture of minerals dominates the dynamic shear failure of sandstone, and the portion of TG fracture increases with increasing loading rate. This study provides a convenient and reliable method to measure the dynamic shear property and failure mechanism of rocks.

The yielding behavior and plastic deformation of oxygen-free copper under biaxial quasi-static and dynamic loadings

This study investigated the yield behavior of oxygen-free copper under complex stress states and different loading rates. An optimized cruciform specimen and a novel electromagnetic biaxial split Hopkinson bar (EBSHB) were used to perform the dynamic biaxial tension tests at three different load ratios. The non-contact digital image correlation technique was adopted for strain measurement. Quasi-static and dynamic yield surfaces were obtained. Classical yield criteria, including the Tresca and von Mises yield criteria, were evaluated based on the experimental results. The von Mises criterion is found to provide better prediction of the yield surface under both quasi-static and dynamic loadings. The Johnson-Cook model from uniaxial test results provides a moderate prediction for experimental curves, while that from biaxial test results shows better prediction. Dynamic biaxial tests are proven necessary to acquire the constitutive models that can accurately describe the mechanical properties of copper under complex stress states.

Numerical modelling of quasi-static and dynamic compact tension tests for obtaining the translaminar fracture toughness of CFRP

In the recent past, several studies have been undertaken to characterise the loading rate dependency of the translaminar fracture toughness GIcf+, however, no consensus has yet been reached. In an attempt to make a first step towards resolving this inconsistency, this work employed a modelling campaign based on the experimental data generated in Hoffmann et al. [Compos Sci Technol 164 (2018) 110–119] in order to identify the driving mechanism behind the negative loading rate trend observed in said study. The numerical analysis employed detailed FE models of the quasi-static and high-rate experiments, as well as a high-fidelity strain-rate- and pressure-dependent user material model to represent the intralaminar behaviour of the composite material. This study found the energy release rate along the macroscopic crack to be practically rate-insensitive. Loading rate, however, was shown to have a pronounced effect on the extent of “secondary” energy dissipation mechanisms away from the macroscopic crack in the form of matrix damage and plasticity. This damage zone was significantly larger under quasi-static than under high-rate loading, thus providing an explanation for the observed drop of GIcf+ under elevated loading rates in Hoffmann et al. (2018).

Amino Acids as Bio-Based Curing Agents for Epoxy Resin: Correlation of Network Structure and Mechanical Properties.

Bio-based alternatives for petroleum-based thermosets are crucial for implementing sustainable practices in fiber-reinforced polymer composites. Therefore, the mechanical properties of diglycidyl ether of bisphenol a (DGEBA) cured with either l-arginine, l-citrulline, γ-aminobutyric acid, l-glutamine, l-tryptophan, or l-tyrosine were investigated to determine the potential of amino acids as bio-based curing agents for epoxy resins. Depending on the curing agent, the glass transition temperature, Young’s modulus, tensile strength, and critical stress intensity factor range from 98.1 ∘C to 188.3 ∘C, 2.6 GPa to 3.5 GPa, 39.4 MPa to 46.4 MPa, and 0.48 MPam0.5 to 1.34 MPam0.5, respectively. This shows that amino acids as curing agents for epoxy resins result in thermosets with a wide range of thermo-mechanical properties and that the choice of curing agent has significant influence on the thermoset’s properties. After collecting the results of dynamic mechanical analysis (DMA), tensile, flexural, compression, and compact tension tests, the functionality f, cross-link density νC, glass transition temperature Tg, Young’s modulus ET, compression yield strength σCy, critical stress intensity factor in mode I KIC, fracture energy GIC, and diameter of the plastic zone dp are correlated with one another to analyze their inter-dependencies. Here, the cross-link density correlates strongly positively with Tg, ET, and σCy, and strongly negatively with KIC, GIC, and dp. This shows that the cross-link density of DGEBA cured with amino acids has a crucial influence on their thermo-mechanical properties and that the thermosets considered may either be stiff and strong or tough, but hardly both at the same time.

Effect of α Phase on Dynamic Mechanical Properties and Failure of Ti-4Al-5Mo-5V-5Cr-1Nb Alloy after Two-Stage Aging

This work studied the high strain rate behavior of the Ti-4Al-5Mo-5V-5Cr-1Nb (Ti-45551) alloy after two-stage aging, with dynamic tension tests conducted using the split Hopkinson tensile bar. The results show that the microstructure, especially the size and distribution of the α phase, significantly affects the mechanical and failure behaviors of the Ti-45551 alloy under dynamic loading. As the strain rate increases, increasing trends can be observed in both ductility and strength, which is intimately related to the activation of the dislocation slip in the α phase. Moreover, obvious strain softening was found in the Ti-45551 alloy under dynamic loading. In this study, the microstructure observations suggest that dislocation slips are highly active in the α phase under dynamic loading. Fractographic characterization of the fracture surfaces under dynamic loading reveals a uniform distribution of ductile dimples, which indicates that a uniform distribution of the nano-scale α phase can effectively reduce brittle fracture tendency. Our studies provide a comprehensive picture of how strain rate drives dynamic plasticity and failure mode in the Ti alloy.

Investigation on the Stability of Janus SiO2-n Nanoparticle-Assisted Nonionic Surfactant-Stabilized Foam and Its Application in Enhanced Oil Recovery

The stability of the foam directly impacts the final efficiency of the foam flooding in enhanced oil recovery (EOR). In the present work, a series of Janus SiO2-n nanoparticles (JSn NPs) with various modification degrees were successfully prepared and employed to improve the stability of the nonionic surfactant polyethylene glycolmonoisodecylether (PMIE)-stabilized foam. The PMIE–JS3 system with a much low JS3 NP concentration (0.1 wt %) displayed extraordinary foamability and stabilizing foam ability via the foam volume, half-life, relative volume decay, and optical microscope photograph measurements. Then, the dynamic surface tension and dilatational viscoelasticity tests were conducted to explore the mechanism. It was found that the PMIE–JS3 system with great interfacial activity and intensive interfacial film highly facilitated the generation of the foam and improved the foam stability. Moreover, the PMIE–JS3-stabilized foam exhibited outstanding stability, even under the influence of crude oil. The sandpack flooding tests indicated that the PMIE–JS3-stabilized foam could effectively plug the high-permeability channels to modify the water injection profile and consequently greatly enhanced tertiary oil recovery (∼15.3% of the initial oil in place).

Suitable Ultra-Thin Asphalt Binder Achieved the Energy Equilibrium

The tensile behaviour of asphalt binder films confined between aggregate particles as an adhesive was investigated to evaluate the direct adhesion bond between asphalt binder and surface of aggregate utilizing several laboratory experiments. The results were interrogated in terms of the mechanical, chemical and surface free energy theories. The preformed tests include dynamic shear rheometer (DSR), sessile drop and direct tension tests. The experimental results demonstrated a strong relationship between the internal work represented by bond energy and the external work represented by the practical work required to fracture from the direct tension test that can be used to estimate asphalt binder-aggregate combinations performance. A simulation for the adhesion behaviour using a static model in terms of external work and internal work to predict the suitable asphalt binder thickness required to prevent fatigue and rutting failures was proposed as a new design criterion for asphalt pavement. Keywords: Internal and external bonding work, asphalt binder, SFE, fracture work, direct tension test, DSR.

Investigation on the dynamic tensile behaviour of rubberized mortar using the Brazilian disc method

The use of tire rubber particles as a partial substitute for fine aggregate in cement-based materials has been proven to potentially have both environmental and economic benefits. Although the studies on the physical and mechanical properties of rubberized mortar are abundant, those related to the dynamic tensile behaviour are scarce. In this study, rubber powders with three sizes (0.125 mm, 0.180 mm, and 0.425 mm) are used to fabricate the Brazilian disc rubberized mortar specimen, with rubber volume percentages up to 40%. A 50 mm-diameter split Hopkinson pressure bar (SHPB) apparatus is then adopted to conduct the dynamic split tension tests, and the static tensile tests are also conducted for comparison purposes. Experimental results show that the dynamic split tensile strength of the rubberized mortar linearly increases with increasing the loading rate, whereas decreases with the increase of the rubber volume percentage. The mortars with smaller rubber powder at the same percentage exhibit more significant dynamic strength loss. As compared with the static tests, the reduction ratio of the dynamic split tensile strength of mortar with different rubber content is much smaller. The dynamic increase factors of the rubberized mortar are more sensitive to the loading rate, and positively correlated to both the rubber volume and the powder size. Besides, the occurring time of the primary crack initiation gradually decreases with increasing the loading rate and rubber size, whereas increases with increasing the rubber volume percentage. In addition, the dissipated energy density of the rubberized mortar is positively correlated with the rubber volume percentage, and the addition of the smaller rubber powder can enhance the dynamic energy absorption capacity.

Stochastically homogenized peridynamic model for dynamic fracture analysis of concrete

Dynamic compact tension tests in concrete are investigated using an intermediately-homogenized peridynamic (IH-PD) model, and the results are compared with a fully-homogenized peridynamic (FH-PD) model as well as with experimental data from the literature. In the IH-PD model, concrete is considered as a two-phase material composed of aggregate and mortar, partially homogenized via a stochastic procedure. Both the FH and IH-PD models capture well the experimentally measured reaction-force time-evolution and crack paths for a wide range of dynamic loading rates, without the need for an explicit representation of microstructure geometry of the concrete material or of rate-dependent parameters. The IH-PD model is more accurate than the FH-PD in reproducing the peak loads and produces crack path tortuosity and randomness, similar to what is observed experimentally. These benefits come from the preservation of some micro-scale heterogeneity, stochastically generated to match the concrete’s aggregate volume fraction. We also find that it matters where one measures the reaction force when trying to connect it to fracture and damage progression in the sample: only when measured on the dynamically loaded side of the pre-notch are features in the reaction-force profile matching critical moments like crack initiation, crack branching, and sample final failure. These results provide guidance for future experiments seeking best placement of damage detection sensors and using elastic wave signal analysis in structural health-monitoring of concrete structures.

Synthesis and Experimental Characterization of a MWCNT-Filled Bio-Based Adhesive

In the present paper, a novel epichlorohydrin/cardanol adhesive was reinforced by multi-walled carbon nanotubes (MWCNTs) and characterized experimentally. The adhesive was reinforced by MWCNTs in weight ratios (wt %) of 0.5%, 1.0% and 2.0%. The bulk properties of the reinforced adhesive were characterized through dynamic mechanical analysis tests, tension tests, and fracture toughness tests, while its shear behavior was characterized through single-lap shear tests on aluminum and composite bonded specimens. The morphology of the reinforced adhesive was characterized using scanning electron microscopy tests. Due to the high viscosity of the bio-based adhesive, special efforts were placed on the dispersion of the MWCNTs into the adhesive, which was achieved through mechanical mixing. The results from the tests show that the presence of the MWCNTs increases the glass transition temperature, the Young’s modulus and the fracture toughness of the reinforced bio-based adhesive, while it decreases its tensile strength. This contradictory finding is attributed to the formation of MWCNT agglomerates into the adhesive. For the content of 2.0 wt %, the shear strength of the reinforced adhesive is increased by 57% for the aluminum joints and by 10.4% for the composite joints. The findings of the study reveal that the reinforcement of the bio-based adhesive by MWCNTs is feasible from a manufacturing viewpoint and may increase the efficiency of the adhesive in structural applications.

Studies on physicochemical properties of three Gemini surfactants with different spacer groups

Three Gemini surfactants with the same hydrophobic chain but different spacer groups, including two cationic Gemini surfactants (CGS and CGS-O) and a zwitterionic Gemini surfactant (ZGS-S), were synthesized, and their chemical structures were characterized by FT-IR and 1H NMR. The effect of spacer group on surface/interface activity, interfacial tension at the oil-water interface, wetting ability, electrolytes tolerance and thermal stability was determined. The results showed the structure of spacer group has a certain influence on the surface/interface activity. Among the three Gemini surfactants, ZGS-S has the strongest ability to reduce surface tension, followed by CGS-O. Three Gemini surfactants can reduce the oil-water interfacial tension to ultra-low value, but the time required to reach the minimum value is different, indicating that the surfactant molecules move at different adsorption rates from solution to the interface. This phenomenon is also confirmed by dynamic surface tension and dynamic contact angle tests. Compared with CGS, CGS-O molecules move slower in the solution, while the adsorption rate of ZGS-S on the interface surpasses that of CGS near the critical micelle concentration. Among the three Gemini surfactants, the electrolytes tolerance of ZGS-S is the strongest, while CGS-O is the lowest. The introduction of sulfate group in spacer group reduces the thermal stability of Gemini surfactant.

Abnormal Magnetic Signals Characterization of Fatigue Crack Propagation Life

In this research, the abnormal magnetic signals were detected in dynamic tension tests on the ferromagnetic material specimens, in order to study the characterization method of abnormal magnetic signals for the crack propagation life. It is indicated that fatigue crack length a is linear with the peak-peak value ΔHpa(y) of abnormal magnetic signals. The ΔHpa(y) of fatigue crack and the gradient of magnetic field intensity k increase with the increase of fatigue cycle number. Therefore, ΔHpa(y) and k are confirmed as the key parameters of characterizing crack propagation life. Then, a life prediction model of abnormal magnetic signals for the crack propagation life is founded based on the Paris equation. The maximum error between measured values and calculated values is less than 15%.