Inclusion Intervention Mechanism And Its Effect On The Material Microstructure Injury

The meso-damage of materials can not only influence the local property of material, but also affect the macro-property of material. The principal of the derivation and evolution of the micro-damage, and the effect of micro-damage on the material behavior are the topics of micro-damage research, and are the physical connotation which should be considered in the construction of microscopic model of material at the present and in the future. It is obvious that the damage and failure of the material are closely related to the existence of inclusions by the equipment failure and scientific research. The heterogeneity induced by inclusions will bring the complex local damage and evolution of material. The interaction mechanisms among micro-structures, such as voids, micro-cracks, inclusions and interface, as well as between the micro-structures and the macro-defects are the very important aspects in the research of the law of micro-damage and in the determination of the local characteristics of materials. The relative research works are the pioneering topics in mechanics and materials.In order to enhance the relative research work, the interaction mechanism among inclusions and its effect on the meso-damage of materials are taking as the keystones of the research work in this dissertation based on the Equivalent Inclusion Method proposed by J. D. Eshelby. The following research results have been achieved for the derivation and evolution of the meso-damage of composite material with the help of numerical computation, digital real-time holography and the meso-observation:1. A numerical computation program, multi_inc, has been written which can be used to analyze the interaction mechanism among inclusions and to demonstrate the calculation results in three dimension figure. The numerical computation of the Equivalent Inclusion Method is also achieved. With the help of Moschovidis' method, the eigenstrain, applied load and the induced strain are represented in polynomial and the equivalent equation for more than two inclusions is established based on superposition principal. The equivalent equation is then transformed as a set of algebraic equations by expanding in Taylor's series around the origin 0 of the coordinate system. The potential functions and their derivations used to describe the displacement field are expressed in elliptic integrals (I-integrals), therefore, the numerical computation of the Equivalent Inclusion Method is realized. In order to let the program to be complete and implantable, all the formulae are written as the procedures or functions in Pascal language. The program includes one main routine and twelve subroutines which contain 168 procedures and functions.The validity and reasonability of this program are testified by comparing its results with those in the literatures, with those of digital real-time holography, and with those of meso-damage observed in particulate reinforced aluminum composite. The computer program supplies us a new means to directly analyze the multi_inclusion problems and the relative problems. At the same time, it is also a new means to testify and evaluate other theories and methods. Based on the literatures which we consulted, this computer program is a new program which can be used to calculate the stress and strain fields numerically by take the interaction among inclusions into consideration.2. The program, Multi-inc, is used to study the interaction mechanisms among inclusions and its effect on the derivation and evaluation of meso-damage of materials. The interaction mechanism for different inclusions is studied with the help of stress fields and their variations which have been calculated by the program for different inclusions, such as holes, cracks, spheroidal inhomogeneoties, and ellipsoidal inhomogeneities, from one inclusion to nine inclusions in different orientations and different configures. The derivation and evolution of micro-damage, such as cracking, debonding and its growth along the particles, the propagation of micro-crack in the matrix, are numerically simulated and analyzed especially. 3. A set of new digital real-time holographic measurement system is developed. In order to overcome the shortcoming of ordinary digital holography and meet the experimental requirement, a kind of equivalent 4f system is proposed, and the formulae used to calculate the transverse magnification and the formulae used to the CCD position in the light path of digital holography are derived in this dissertation. The disposal of the light path can then be adjusted according to the size of specimen. The digital real-time holography can be used to measure an area of 100 square centimetres. Besides, in order to advance the quality of digital hologram, the related data process method is also proposed and a method of eliminating the zero-order diffraction but remaining high frequency information of object light is derived theoretically. The corresponding digital image process program is also written and the satisfying digital interference patterns are obtained. The reliability of the digital holography measurement system is testified by comparing the digital real-time holograms with classical real-time holograms. Many strain fields of multi inclusions, such as circular holes, elliptic holes and cracks, are measured by digital holography. The interaction mechanism of multi inclusions and the reliability of the numerical computation program are studied by the experiment. One of the most important points is that this new digital real-time holographic system can be used to measure the physical parameter variation between any two statuses, but the classic holography can only be used to measure the physical parameter variation between the status to be measured and the initial status. With this kind of excellent characteristic, much more information can be obtained, and some special phenomenon can then be discovered with the help this system. Besides, the laws about the derivation and evolution of interference fringes discovered in the digital real-time holographic experiment supply the new means for us to count the interference fringes, and to determine the dangerous position in the simulation specimen of the equipment component especially.4. The derivation and evolution of micro-damage for particulate reinforced composite material is analyzed combined with the numerical computation results and the mesoscale experimental observation. The zirconium dioxide particulate reinforced 2124 aluminum composite is prepared. The tension fatigue, compression fatigue and tension fracture experiments have been done at different stress level for many specimens. The derivation and evaluation of the meso-damage have been studied by the mesoscale pictures taken at different fatigue cycles under the different stress level. It can be concluded that the main meso-damage types are the micro cracks, debonding and cracking of particulates in the material. The particulate conglomeration will not induce the meso-damage apparently. Besides, the derivation and evaluation of the main meso-damage types observed in the material are compared well with the distribution and variation of stress fields calculated by the numerical computation.