Modeling the Compressive Behavior of Anisotropic, Nanometer‐Scale Structured Silica

Abstract

Recently, large plastic deformations were observed during compression testing of biotemplated, anisotropic, and hierarchically structured silica monoliths. Based on the material's nanometer-scale structuring, a dynamic model is devised in which parallel silica struts are compressed, and sheared in longitudinal direction. The resulting interfacial shear forces lead to successive plastic deformations during cyclic loading with incrementally increasing forces, matching observations by mechanical testing. The authors report on the physical parameter values obtained from fitting model curves to measured ones, their relation to prior structural observations, and their utility to tailor the intricate mechanical behavior of this novel material.

Stresses State and Mechanical Behaviors of the Green Body During Die Compaction and Ejection Process

“…The friction coefficient between die wall and powder will affect the density distribution and stress distribution, and here the value of friction coefficient is experimentally obtained by using instrumental cubic die compaction test [16,17] and it was set to 0.2.…”

“…Here, phenomenological physical scale compaction model of modified density-dependent DPC in which treats the powder mass as a continuum was used to simulate the die compaction process. Figure 1a shows the yield surface of DPC model with constant material parameter described in the p − q (hydrostatic pressure p − deviatoric stress q) plane [17][18][19]. Figure 1b shows the modified density-dependent DPC model, where the yield surfaces are not only the function of hydrostatic pressure p and devistoric stress q but also the function of green density used in this study.…”

“…where and dare functions of green density same as shown in Eq. (2), and the flow potential equation is non-associated F s and F t , which are defined by [17]:…”

“…Therefore, numerical simulation of stresses development during pressing by finite element analysis can be aid to understanding of inside stresses picture of the green body without pay the extremely cost [15,16]. The potential for cracks has been recognized as a significant concern and often limits its application of powder metallurgy technology for the product of complex part geometries [17]. Following investigations are carried out: What is driving force for crack initiation, primarily axial, radial or hoop tensile stress components in the green body or maximum principal stress?…”

“…The aim of this work is to explore all stresses state in the green body of clutch plate during die compaction process by finite element simulation during entire die compaction process including loading and unloading and ejection stages, to analysis the effect of each kind of stress on compaction process, and to establish a knowledge of relationship among stresses, green density, and kinematic of the tooling. To do this, a modified density-dependent Drucker-Prager/ Cap (DPC) model was employed to simulate the entire die compaction process [15][16][17][18]. Because the development of stresses was highly related to material properties, such as elastic and plastic properties, material model parameters involved in the simulation were experimentally calibrated using instrumental rigid cubic die tooling sets to ensure accurately reflecting the stresses level.…”