Failure Pattern Transition of Shape Memory NiTi Foam Subjected to Compression: From Quasi-Static to Dynamic

Xiaojuan Wang,Hongyuan Zhou

doi:10.3390/app8050741

Abstract

Shape memory alloy can recover its original configuration, while lightweight foam can absorb a considerable amount of energy. It is desirable to test whether shape memory foam has merits in terms of both shape memory effect and exceptional energy absorption capacity. In the present study, shape memory NiTi foam is compressed quasi-statically and dynamically in order to investigate its response and failure pattern transition with an increasing loading rate. A universal testing machine is used in a quasi-static test, while the split Hopkinson pressure bar is employed in the dynamic test. It is observed that the NiTi foam fails differently: under a quasi-static load, small foam parts of various sizes fall off from the specimen fringe; meanwhile, under dynamic load, the foam fractures in the specimen center to split it into multiple pieces. The underlying failure mechanisms accounting for the shape memory foam behavior under different loading rates are discussed.

Highlights

Shape memory alloy (SMA) is widely applied in various applications [1], especially in the form of wires and bars [2,3,4,5]
Foam and porous materials have exceptional properties in some aspects compared to their solid counterparts with the same mass, such as their strength-to-density ratio, fireproof nature, and thermal and sound isolation; they are a versatile material with multiple applications
It is natural to consider combining both merits of SMA and foam/porous structures to fabricate porous SMA or SMA foam

Summary

Introduction

Shape memory alloy (SMA) is widely applied in various applications [1], especially in the form of wires and bars [2,3,4,5]. Manufactured even from recycled beverage cans [6], its excellent energy absorption capacity [7,8] makes it a promising candidate for structure protection against highly dynamic loads such as blast and impact. It can be used as the core of sandwich sacrificial claddings for building protection [9,10], the inner layer of blast chambers [11], and as the crush mitigation layer for automobiles and water vehicles [7]. Among the various SMA foam manufacture methods, various sintering methods [13,14] are frequently applied, while three-dimensional (3D) interconnected microchannels with steel wire spaceholders [15] is an alternative approach to fabricate NiTi porous structures

Methods

Results

Conclusion