Strain Rate Effect of AE Characteristics in the Whole Process of Uniaxial Tensile of Mortar

Abstract

We completed the uniaxial tensile test of mortar in the range of strain rate from 10⁻⁶ to 10⁻⁴ s⁻¹ in the section containing softening, and carried out acoustic emission monitoring (AE) simultaneously. A series of AE parameters and spectrum analysis methods were used to identify the damage evolution process and cracking mechanism of mortar at different strain rates. The results show that, with the increase of strain rate, the peak stress and tensile elastic modulus of mortar increase obviously, and the stress level corresponding to the starting point of AE activity increases significantly as well, which indicates that the mechanical properties and AE characteristics of mortar have obvious strain rate effect. With the increase of strain rate, the cumulative AE hit decreases gradually, while the average AE hit rate increases significantly, indicating that the increase of strain rate reduces the damage degree of internal microstructure of the specimen, but the crack propagation speed increases. In the pre-peak stress stage, the average of AE ringing count and signal energy decreases with the increase of strain rate, while the average of duration increases; in the post-peak stress stage(f _t − 30% f _t), the average of the three AE parameters all increase with the increase of strain rate, indicating that the strain rate effect on the damage process of mortar is different before and after peak stress, and the damage mechanism represented by different parameters is also different. In the whole process of uniaxial tensile of mortar, with the increase of strain rate, the scatter distribution of AE frequency-amplitude becomes more discrete, and the b-value shows a decreasing trend. In addition, the average level of AE peak frequency decreases with the increase of strain rate, while that of ca8 band wavelet energy spectrum coefficient increases. It is indicated that the increase of strain rate enables the crack propagation state of mortar specimen to become unstable, and the width of macrocrack increases but the proportion decreases.

Keywords

mortar / acoustic emission / uniaxial tension / strain rate

References

[1] Aggelis D G, Mpalaskas A C, Matikas T E. Investigation of Different Fracture Modes in Cement-Based Materials by Acoustic Emission[J]. Cem. Concr. Res., 2013, 48: 1-8.

[2] Wu S X, Wang Y, Zhou J K, et al. Experimental Study of Dynamic Axial Tensile Constitutive Relationship for Mortar[J]. China Civil Engineering Journal, 2012, 45(1): 13-22.

[3] Cadoni E. Strain-rate Effect on the Tensile Behaviour of Concrete at Different Relative Humidity Levels[J]. Mater. Struct., 2005, 34(235): 21-26.

[4] Yang Z W, Li J Z, Huang F L. Study on the Strain Rate Effect of Cement Mortar[J]. Trans. Beijing Inst. Technol., 2019, 39(6): 571-577.

[5] Asprone D, Iucolano F, Cadoni E, et al. Analysis of the Strain-Rate Beahavior of a Basalt Fiber Reinforced Mortar[J]. Appl. Mech. Mater., 2011, 82: 196-201.

[6] Sagar R V, Prasad R V, Prasad B, et al. Microcracking and Fracture Process in Cement Mortar and Concrete: A Comparative Study Using Acoustic Emission Technique[J]. Exp. Mech., 2013, 53(7): 1161-1175.

[7] Tittelboom K V, Belie N D, Lehmann F, et al. Acoustic Emission Analysis for the Quantification of Autonomous Crack Healing in Concrete[J]. Constr. Build. Mater., 2012, 28(1): 333-341.

[8] Wang Y, Chen S J, Ge L, et al. Analysis of Dynamic Tensile Process of Fiber Reinforced Concrete by Acoustic Emission Technique[J]. J. Wuhan Univ. Technol.-Mater. Sci. Ed., 2018, 33(5): 1129-1139.

[9] Ohtsu M, Iwase H, Koyanagit W, et al. Determination of Crack Location, Type and Orientation in Concrete Structures by Acoustic Emission[J]. Mag. Concr. Res., 2015, 43(155): 127-134.

[10] Ozbulut O, Sherif M, Tanks J D. Acoustic Emission Analysis of Cyclically Loaded Superelastic Shape Memory Alloy Fiber Reinforced Mortar Beams[J]. Cem. Concr. Res., 2017, 95: 178-187.

[11] Tajunnisa Y, Shigeishi M, Bayuaji R, et al. Reliability of Alkali-activated and Portland Cement Mortar under Compressive Test by Acoustic Emission[J]. Int. J. GEOMATE., 2019, 17(60): 197-203.

[12] Kourkoulis S K, Dakanali I. Pre-failure Indicators Detected by Acoustic Emission: Alfas Stone, Cement-mortar and Cement-paste Specimens Under 3-point Bending[J]. Frattura ed Integrità Strutturale., 2017, 11(40): 74-84.

[13] Wang Y, Wang N, Wang Z, et al. Experimental Study on AE Characteristics of Granite under Uniaxial Tension at Different Strain Rates[J]. J. Wuhan Univ. Technol.-Mater. Sci. Ed., 2020, 35(4): 691-698.

[14] Li B Q, Einstein H H. Correction to: Comparison of Visual and Acoustic Emission Observations in a Four Point Bending Experiment in Barre Granite[J]. Rock Mech. Rock Eng., 2018, 51: 2277-2294.

[15] Stergiopoulos C, Stavrakas I, Hloupis G, et al. Electrical and Acoustic Emissions in Cement Mortar Beams Subjected to Mechanical Loading up to Fracture[J]. Eng. Fail. Anal., 2013, 35: 54-461. Complete)

[16] Rouchier S, Woloszyn M, Foray G, et al. Characterisation of Concrete and Mortar Cracking by Digital Image Correlation and Acoustic Emission[J]. Eur. J. Environ. Civ. Eng., 2013, 17(6): 67-477.

[17] Wang Y, Chen S J, Xu Z Z, et al. Damage Processes of Polypropylene Fiber Reinforced Mortar in Different Fiber Content Revealed by Acoustic Emission Behavior[J]. J. Wuhan Univ. Technol.-Mater. Sci. Ed., 2018, 33(1): 155-163.

[18] Wang Y, Yan C, Wang N, et al. Experimental Study on Damage Mechanism of Basalt Fiber Reinforced Mortar Based on Acoustic Emission Wavelet Energy Spectrum Analysis[J]. Russ. J. Nondestr. Test., 2020, 56(4): 318-327.

[19] Colombo S, Main I G, Forde M C. Assessing Damage of Reinforced Concrete Beam Using “b-Value” Analysis of Acoustic Emission Signals[J]. J. Mater. Civ. Eng., 2003, 15(3): 280-286.

[20] Khazaei C, Hazzard J, Chalaturnyk R. Damage Quantification of Intact Rocks Using Acoustic Emission Energies Recorded During Uniaxial Compression Test and Discrete Element Modeling[J]. Comput. Geotech., 2015, 67: 94-102.

[21] Marinescu I, Axinte D. A Time-frequency Acoustic Emission-based Monitoring Technique to Identify Workpiece Surface Malfunctions in Milling with Multiple Teeth Cutting Simultaneously[J]. Int. J. Mach. Tool. Manu., 2009, 49(1): 53-65.

[22] Gutkin R, Green C J, Vangrattanachai S, et al. On Acoustic Emission for Failure Investigation in CFRP: Pattern Recognition and Peak Frequency Analyses[J]. Mech. Syst. Signal Pr., 2011, 25(4): 1393-1407.

[23] Qi G, Barhorst A, Hashemi J, et al. Discrete Wavelet Decomposition of Acoustic Emission Signals from Carbon-fiber-reinforced Composites[J]. Compos. Sci. Technol., 1997, 57(4): 389-403.

[24] Cao J, Chung D D L. Effect of Strain Rate on Cement Mortar under Compression, Studied by Electrical Resistivity Measurement[J]. Cem. Concr. Res., 2002, 32(5): 817-819.

[25] Hu S, Lu J, Xiao F. Evaluation of Concrete Fracture Procedure Based on Acoustic Emission Parameters[J]. Constr. Build. Mater., 2013, 47(47): 1249-1256.

[26] Li Z, Li F, Li X S, et al. P-wave Arrival Determination and AE Characterization of Concrete[J]. J. Eng. Mech., 2000, 126(2): 194-200.

[27] Su H Z, Hu J, Tong J J, et al. Rate Effect on Mechanical Properties of Hydraulic Concrete Flexural-tensile Specimens under Low Loading Rates Using Acoustic Emission Technique[J]. Ultrasonics, 2012, 52(7): 890-904.

[28] Filimonov Y, Lavrov A, Shkuratnik V. Acoustic Emission in Rock Salt: Effect of Loading Rate[J]. Strain., 2010, 38(4): 157-159.

[29] Wang Y, Wang N, Yan C, et al. Strain Rate Effect on the Acoustic Emission Characteristics of Concrete under Uniaxial Tension[J]. Mater. Test., 2020, 62(1): 5-11.

[30] Chen L, Xu X L, Xu Y H. Effect of Temperature and Loading Rate on Mechanical Properties of Rock[J]. J. Guangxi Univ. (Nat. Sci. Ed)., 2016, 41(01): 170-177.

[31] Kim J S, Lee K S, Cho W J, et al. A Comparative Evaluation of Stressstrain and Acoustic Emission Methods for Quantitative Damage Assessments of Brittle Rock[J]. Rock Mech. Rock Eng., 2015, 48(2): 495-508.

[32] Kong B, Wang E, Li Z, et al. Acoustic Emission Signals Frequency-amplitude Characteristics of Sandstone after Thermal Treated under Uniaxial Compression[J]. J. Appl.Geophys., 2017, 136: 190-197.

[33] Wang Y, Wu S X, Zhou J K. Experiment on Acoustic Emission Characteristics of Dam Concrete under Dynamic Bending Tension[J]. Nondestr. Test., 2009, 31(2): 115-119.