The work aimed to improve the fundamental acoustic defectoscopy principles of green compacts and weakly sintered materials. A theoretical method for determining the elastic properties of powder porous materials with distributed microdefects has been proposed. The nonlinear elastic multimodulus (different stiffness in tension and compression) behavior of this material has been described by micromechanical averaging on a representative cell. According to the mechanics of composites, the cell geometry represents the structure of a heterogeneous material, and the boundary conditions on a representative cell enable relating the stress–strain state at the macro- and meso-level. The averaging was carried out by computer simulation using the finite element method with an adaptive mesh, which automatically condensed in the places of the large gradient stress–strain. The structure of the representative cell corresponds to a powder material with ‘imperfect’, i.e., partially stratified, interparticle contacts. In the proposed model, the rheological response of a porous, damaged material is specified by three elastic moduli. The structure of such a material is described by two internal state parameters, namely, the porosity and the degree of interparticle contacts delamination. That is, the elastic moduli are functions of porosity and damage. Accordingly, several values of elastic moduli were calculated for a discrete density and damage range. The advantage of this approach is focused precisely on the powder materials rather than on any damaged material, in general, which allows considering the real structure of the damaged material using the mechanics of microheterogeneous materials. The developed structure-sensitive elasticity model enabled establishing the relationship between the defectiveness of a porous sample and the resonant frequency of its free vibrations.

这项工作旨在改善生坯和弱烧结材料的基本声学缺陷检查原理。提出了一种确定具有分布微缺陷的粉末多孔材料弹性性能的理论方法。这种材料的非线性弹性多模量（拉伸和压缩强度不同）行为已通过在代表性单元上进行微机械平均来描述。根据复合材料的力学，单元的几何形状代表了异质材料的结构，并且具有代表性的单元上的边界条件使宏观和中观水平的应力-应变状态得以关联。使用带有自适应网格的有限元方法通过计算机模拟进行平均，它会自动在大的梯度应力-应变位置处凝结。代表性电池的结构对应于具有“不完美”（即部分分层的颗粒间接触）的粉末材料。在提出的模型中，多孔，受损材料的流变响应由三个弹性模量确定。这种材料的结构由两个内部状态参数描述，即孔隙率和颗粒间接触分层的程度。即，弹性模量是孔隙率和损伤的函数。因此，针对离散的密度和损伤范围计算了几个弹性模量值。通常，这种方法的优势在于粉末材料上，而不是任何损坏的材料上，这允许使用微非均质材料的力学来考虑损坏材料的真实结构。开发的结构敏感弹性模型能够建立多孔样品的缺陷与其自由振动的共振频率之间的关系。