Experimental Study On Acoustical Characteristics Of Concrete Under Uniaxial Compressive Cycle Load And Damage Evolution Analysis

Concrete is widely used as a durable material,but after long-term use,the degree of damage is not detected,and the mechanical properties of concrete under cyclic loading will deteriorate to varying degrees,which in turn will cause fatigue damage,which ultimately leads to the overall bearing capacity of the building It drops and breaks down,so it is particularly important to strengthen the non-destructive testing of concrete and grasp the evolution law of the concrete damage process.At present,the research ideas for exploring the evolution law of the damage process for concrete under the uniaxial cyclic load combined with ultrasonic and acoustic emission detection techniques are relatively new.Therefore,this paper explores the acoustic characteristics and damage evolution law of concrete under uniaxial cyclic loading by using ultrasonic and acoustic emission technology,supplemented by mechanical characteristics,in order to make the dynamic damage characteristics of concrete correspondingly supplemented and improved.The main work and research results of this article are as follows:(1)Conducted laboratory tests,using the three variables of stress level,water content and water-cement ratio to carry out research on concrete in two levels of cyclic loading and unloading,and found that the stress-strain,elastoplastic strain,wave velocity and cumulative vibration of concrete The bell count curves all reflect that the concrete is less affected by the low stress,and the concrete damage will change significantly as the stress increases;the specimen with the larger water-cement ratio will have greater damage under the same water content.When the water-cement ratio is the same,the damage of the test piece increases with the increase of the water content.In all the curves,the test pieces with different water content and water-cement ratio show different degrees of degradation.The higher the water content,the more obvious the deterioration of the test piece;the water content will affect the distribution characteristics of the acoustic emission,and the Kaiser effect is found in the concrete from the step-by-step loading and unloading method.(2)Perform damage variable transformation,use the test data to establish a concrete damage variable curve with plastic strain,wave speed and cumulative ring count as parameters,analyze the damage evolution law of concrete under uniaxial cyclic load,and find that the above parameters are used to evaluate uniaxial cyclic load The concrete damage process under action is feasible,and the conclusions obtained are the same as the curve analysis of the test data.(3)Carrying out numerical simulation,using RFPA 2D to simulate the step-by-step loading and unloading process of concrete,analyzing the mechanical and acoustic characteristics of the concrete cracking process under loading and unloading conditions,and found that the shear stress damage simulated by the software and the distribution of acoustic emission activity characteristics can be dynamically demonstrated The crack propagation process of the specimen;the specimen exhibits compression-shear acoustic emission before the final fracture,which has obvious cone damage characteristics;RFPA 2D can better reproduce the Kaiser effect and damage characteristics of concrete in indoor tests.