Preliminary Study And Application Of Acoustic Parameters Of Metallic Materials

Diminishing global resources, raw material prices soaring in recent years, and some metal manufacturers or raw material suppliers use cheaper metal substitutes to replace higher raw material prices to reap huge profits, or to reduce costs by cutting corners to get high yields, manufacture do not comply with international standards or buyers specification metal products, resulting in significant loss or accidents. This not only greatly impacts the materials market, endanger the safety of the people but also seriously affect the establishment of China’s socialist market economic system, it become a great obstacle to the healthy development of China’s economy. Therefore, metallic material security identification analysis becomes more and more important. The traditional identification methods of metal material have physical and chemical identification. Among them, the physical identification of metal aim at the macroscopic physical characteristics and the microscopic characteristics in the physical processes.The common methods include sensory recognition, fracture identification and spark recognition, etc.Since the physical identification method is simple, good scene, and the accuracy of analysis can from qualitative to semi-quantitative for commonly used metallic materials, these methods seem to have been able to meet the requirements, but there are some limitations, for example, some physical identification methods are damaged, large errors, sometimes not very accurate. Chemical identification is based on the chemical reaction to analysis the metal composition and identifies what kind of metal. The common Chemical composition analysis methods include titration analysis, gravimetric analysis and volumetric analysis, etc. Chemical identification methods do not online analysis, more complex and lossy.These methods obviously not very scientific for the identification of precious metal materials or precious metal collections. How can we do to accurately identify these materials without any damage, and achieve the security purposes? Aiming at this problem, this paper discussed and studied the nondestructive identification method of metal material with three different kinds of metal materials (the same material with different heat treatment conditions), Specific basis and work as follows:The response of a metallic material is closely related to the micro structure under ultrasonic, When ultrasonic spreads in different metal materials(different microstructures) and same material(different grain size inside the material, not the same microstructure) of different heat treatment conditions, the acoustic energy loss and the variation of the propagation velocity(Sound attenuation coefficient and the velocity) is different, While narrow pulse encounter back reflection when it spreads in material of the different internal microstructure, in which various changes of different frequency harmonics are different, thereby the changes(the peak frequency and bandwidth will be different) of narrow pulse spectrum after Superposition will be different, these are related with the characteristics of the material, therefore it provide the information to determine the internal characteristics of the material. In other words, these acoustic parameters of different metal materials and the same material under different heat treatments are different. Therefore, According to measuring the different ultrasonic acoustic parameters in materials with different internal microstructure, we can identify (authentication or security) the metal material.In this paper, according to the propagation characteristics of ultrasonic of metal ma terials, the material’s sound velocity, sound attenuation coefficient, the amplitude spectr um of primary bottom echo and the peak frequency and bandwidth in power spectrum is calculated by using the test of primary and secondary bottom echo. The method of iden tify different metal material, different heat treatment state of the same material and the mixed material (including different metal materials and each of the material have differe nt heat treatment states) are studied. The results show that metal materials can be identif ied by measuring the acoustic parameters of materials using ultrasonic nondestructive te sting. And the advantages of the method is nondestructive, simple, high accuracy, fast, suitable for online detection and wide range of application, and it also can be well used f or the nondestructive anti-fake identification of precious metal material or precious met al collection.