Survivability of Suddenly Loaded Arrays of Micropillars.

Tomasz Derda,Zbigniew Domanski

doi:10.3390/ma14237173

Abstract

When a multicomponent system is suddenly loaded, its capability of bearing the load depends not only on the strength of components but also on how a load released by a failed component is distributed among the remaining intact ones. Specifically, we consider an array of pillars which are located on a flat substrate and subjected to an impulsive and compressive load. Immediately after the loading, the pillars whose strengths are below the load magnitude crash. Then, loads released by these crashed pillars are transferred to and assimilated by the intact ones according to a load-sharing rule which reflects the mechanical properties of the pillars and the substrate. A sequence of bursts involving crashes and load transfers either destroys all the pillars or drives the array to a stable configuration when a smaller number of pillars sustain the applied load. By employing a fibre bundle model framework, we numerically study how the array integrity depends on sudden loading amplitudes, randomly distributed pillar strength thresholds and varying ranges of load transfer. Based on the simulation, we estimate the survivability of arrays of pillars defined as the probability of sustaining the applied load despite numerous damaged pillars. It is found that the resulting survival functions are accurately fitted by the family of complementary cumulative skew-normal distributions.

Highlights

Significant progress has been made in the creation and development of sub-micronscale devices, including nanopillars assembled in an ordered fashion on flat substrates [1,2]
The newest family of these energy-harvesting devices consists of NGs with vertical core–shell micropillars [7,8] stacked between flexible flat substrates that play the role of base and counter electrodes
We have carried out a substantial number of simulations of the model specified in Section 2 to collect data necessary to estimate the survival function correctly

Summary

Introduction

Significant progress has been made in the creation and development of sub-micronscale devices, including nanopillars assembled in an ordered fashion on flat substrates [1,2]. The newest family of these energy-harvesting devices consists of NGs with vertical core–shell micropillars [7,8] stacked between flexible flat substrates that play the role of base and counter electrodes. When an external load is applied axially in a form of loading-holdunloading pulses, the counter electrode moves correspondingly, and the alternating current is generated due to the piezoelectric effect. Flexible sensors that are capable of measuring multidirectional forces represent another group of devices involving arrays of micropillars. In this case, micropillars that are aligned vertically and sandwiched between electrodes form a piezoelectric sensing unit capable of detecting a normal compressive force [9]

Objectives

Results

Conclusion