On the origin of the first peak of acoustic emission in 7075 aluminium alloy (original) (raw)
Related papers
Acoustic Emission Signal Analysis to Study the Yield Behaviour of AA 2219 Aluminium Alloy Material
2015
AA2219 aluminum alloy is widely used for aerospace applications due to its good strength at high temperature as well as cryogenic temperatures. It is used for the fabrication of launch vehicle components such as propellant tanks, engine casings & structural components like heat shield and interstages. Acoustic emission (AE) is widely used in the aerospace industry for the real time structural integrity evaluation of pressure vessels and structures made of AA2219 alloys. Since AE is a material dependant phenomenon an acceptable criteria based on the characteristics of AE signals corresponding to various source mechanisms in parent metal and weldments of 2219 material is used for the assessment of the pressure vessels made of that material. The weld regions of metallic pressure vessels are more critical in view of the possible failure due to defect growth under loading. More than 80% of energy expended on fracture in 2219 alloy material goes to development of plastic deformation. Henc...
Quantification of damage evolution in a 7075 aluminum alloy using an acoustic emission technique
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011
The use of acoustic emission for quantifying the microstructural damage evolution under tensile loading is studied for a 7075 aluminum alloy. First, the cracking of intermetallic particles present in the material was evaluated using interrupted tensile tests combined with digital image analysis of large optical image montages. Subsequent acoustic emission tests under tensile monotonic loading produced an in situ signature that correlated with the quantitative stereology results obtained destructively. Acoustic emission is a viable option for quantifying the evolution of microstructure damage in terms of particle cracking for the 7075 alloy.
2017
The crack growth in the engineering materials usually precedes the occurrence of a significant amount of plasticity at the crack tip. The plastic deformation and crack opening of the metallic materials usually produce intense acoustic emission. The paper reports on an experimental study carried out to determine the characteristics of the acoustic emission signals emitted from AA2219 Aluminium material during crack opening. Unsupervised pattern recognition analysis of acoustic emission signals captured during the tensile loading of a compact tension specimen is carried out to segregate the genuine AE signals from all the data acquired during tension test. 3 classes of signals segregated through the K-means cluster algorithm has been analyzed in detail. The variation in the magnitude of AE parameters of different clusters is distinct. The signature of crack growth based on the AE parameters viz. amplitude, duration, energy and counts has been obtained through the study.
Knowledge of the relaxation properties of metal materials at high temperatures is necessary for the verification of susceptibility of castings to the creation of defects during the production process. Generated tensions in the castings are the cause of creation and development of defects. At the acoustic emission (next denoted the "AE") use, tensile tests at high temperatures may, among other things, be used for analysis of the AE signal sources and set, in more detail, the temperature limit of elastic-plastic deformations existence in the material under examination. The AE is, during tensile tests at high temperatures, based on the scanning of released elastic waves generated by sharp tension changes in the body as a result of the subsequent physical-metallurgical processes such as plastic deformation, tension redistributing, creation of microcracks and their spreading in macroscopic scale. The results of testing above mentioned magnesium alloys will serve for evaluation of possibility those magnesium alloys for application of SPD methods. The aim of the acoustic emission monitoring at tensile tests at higher temperatures is therefore the specification of the critical heat barrier of the elastic-plastic condition of materials and provision of information concerning the dynamics of deformation processes at tension including influences of surface layers for which acoustic emission, as confirmed by measurement results is a very suitable method. Presented work was further focused on determination of structure characteristics including investigation of fracture characteristics with use of light microscopy and SEM analysis.
Journal of Materials Research and Technology, 2015
In the present investigation, the effect of Al-5Ti-1B grain refiner on the microstructure, mechanical properties and acoustic emission characteristics of Al 5052 aluminium alloy have been studied. Microstructural analysis showed the presence of primary ␣ solid solution. No Al-Mg phase was found to be formed due to the presence of magnesium in the solid solution. The results indicated that the addition of Al-5Ti-1B grain refiner into the alloy caused a significant improvement in ultimate tensile strength (UTS) and elongation values from 114 MPa and 7.8% to 185 MPa and 18% respectively. The main mechanisms behind this improvement were found to be due to the grain refinement during solidification and segregation of Ti at primary ␣ grain boundaries. Acoustic emission (AE) results indicated that intensity of AE signals increased with increase in Al-5Ti-1B master alloy content, which had been attributed to the combined effect of dislocation motion and grain refinement. The field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) analysis were used to study the microstructure and fracture surfaces of the samples.
The Regularities of Acoustic Emission on Fatigue Destruction of an Aluminum Alloy
Journal of the mechanical behavior of materials, 2003
Some aspects of application of acoustic emission (AE) to the study of aluminum alloy fatigue fracture are considered in the present paper. The main purpose of the research was to determine the connection between the character of an A Ε change and the phases of fatigue fracture development and the creation of a model of the A Ε process. The main postulate, which forms the basis for the model of the AE process during fatigue fracture development, may be conditionally named the postulate of the discrete AE process self-similarity. The essence of this is as follows: The total discrete AE is proportional to the total area of recently derived surfaces of the material gap independent of the phase of the fatigue process development. The second postulate of the basis of the fatigue model process is called the postulate of stability: During the fatigue development, the system of microcracks sequentially passes a number of steady configurations determined by regularities of the interference of microcracks, and the final configuration is one active crack called the turnpike crack. The assumptions regarding AE conformity to phases of fatigue fracture development are made on the basis of the AE process formation self-similarity postulate and of the microcrack system configuration stability in the polycrystalline material. The calculations under the offered model do not contradict experimental data obtained for the aluminum alloy. 1. INTRODUCTION. The method of acoustic emission (AE) is in rather extensive use in the practice of airframe technical state control /1-6/. One of the major virtues of this method is the direct connection of fixed signals with irreversible processes of strain and fracture, taking place in the inspected material /1,2,7-9/. The AE method allows fixing in time of a dynamic phenomenon, occurring in the material, rather precisely. In many situations the modern systems of measurement allow also determination of coordinates of a stimulus source
Materials Science and Engineering: A, 1993
The Portevin-Le Chfitelier (PLC) effect (discontinuous plastic flow) in an A1-2.92%Mg-0.38%Mn alloy deformed at room temperature has been studied using linear location of acoustic emission (AE). Location distributions have been found to be essentially dependent on strain. At the initial stage of plastic deformation a significant AE activity was monitored along the entire gauge length, well tracing the propagation of deformation bands; subsequently, some AE activity remained in the vicinity of the sample heads only. The results are discussed in terms of the present knowledge of the PLC effect and AE and possible mechanisms responsible for the observed AE activity are suggested.
Nfluence of Nanostructuration on the Sound Velocity in Aluminum AL_99.50
European Journal of Materials Science and Engineering, 2017
The paper aims to determine the influence of nanostructure on sound velocity, to severe plastic deformation by cold multiaxial forging of aluminum. The deformation process is discontinuous and comprises deformation processes defining a severe plastic deformation cycle. Thus, a number of 7 determinations were performed for each sample, corresponding to the first 12 cycles of severe plastic deformation. As a result of the analysis of the results, it can be deduced that the area of passages 3, 4 and 5 represents, in fact, precisely the transition zone between micrometric granulation and mesoscopic (ultrafine) granulation, which is only
Acoustic Emission Analysis Of Aluminum Specimen Subjected To Laser Annealing
This paper deals with the study of acoustic emissions (AE) from aluminum Al5068 specimen during local annealing process by a laser diode source. The heating cycle, obtained by irradiating the surface of the specimen, causes a change in the local stress state which can be studied by X-Ray diffractometry; at the same time acoustic emissions can be recorded as a consequence of residual stress relieving. This hybrid approach provides evidence of the presence of a correlation between stress relieving and the number of signals of acoustic emissions recorded during the heating and the cooling stages. Annealing cycle was repeated several times and acoustic emissions were detected during each cycle; the amount of residual stresses along the longitudinal direction was measured at the end of each cycle as well. The number of acoustic signals exhibits the typical behavior due to the Kaiser effect while residual stresses show a quite regular decrease from cycle to cycle. Mechanical tensile tests have also been performed on the same specimen tested at four different loads. In this case too, experimental results show evidence of Kaiser effect, however a steeper reduction of the number of signals is observed with respect to the thermal tests.