An Experimental Study of Fracture of LIGA Ni Micro-Electro-Mechanical Systems Thin Films

Abstract

This article presents the results of an experimental study of fracture in LIGA Ni micro-electromechanical systems (MEMS) thin films. Microtesting techniques are developed for the study of the J-resistance curve (J-Da) behavior in compact tension (CT) thin film specimens. In-situ measurements of crack-tip strain are presented together with in-situ and ex-situ microscopic images of crack-tip deformation and fracture mechanisms. Fractographic observation showed a mixture of inclined fracture planes (slant fracture) that are relatively featureless and normal fracture planes that exhibit dimples and microholes resulting from plastic deformation.

Fracture toughness testing of nanocrystalline alumina and fused quartz using chevron-notched microbeams

“…Once the method was perfected, these often gave data consistent with data from macroscopic tests of the same material (Si notably) [2,13,19,[37][38][39][40]. Finally, some authors have used fatigue of notched microspecimens to create precracks in metallic specimens (prone to largescale yielding, however) [41][42][43], and also in silicon [44].…”

Small-Scale Multiaxial Setup for Damage Detection Into the Very High Cycle Fatigue Regime

“…This softening leads to a decrease in the stress amplitude and hence the slope of the stress-strain hysteresis is reduced. This decrease could be compensated, as it is in the work of Yang et al, by changing the position of the piezo actuator to maintain mean load [25,26]. Nevertheless this is not the case in this manuscript.…”

Role of oxide thickening in fatigue crack initiation in LIGA nickel MEMS thin films

“…1). The material had Young's modulus of $ 170 GPa (Table 1), a 0.2% offset yield stress of $ 310 MPa and an ultimate tensile strength (UTS) of $ 510 MPa [13][14][15][16]. The microstructure of the sample was revealed to have gradation across the deposition direction and a predominant {001} microtexture (Fig.…”

“…Since such devices are likely to undergo monotonic and cyclic loads that can induce sub-critical crack growth, there have been a number of studies of the tensile properties [6][7][8][9] and fatigue and fracture behavior [10][11][12][13][14][15][16] of LIGA Ni MEMS thin films. However, there have been relatively few studies of the mechanisms of fatigue crack nucleation in LIGA Ni MEMS thin films [12][13][14][15].…”

“…Brown et al [10] also used comb-drive MEMS structures to show the susceptibility of Ni MEMS structures to fatigue. Subsequent work by Allameh et al [11], Boyce et al [12] and Yang et al [13][14][15][16] provided new insights into fatigue and fracture modes under monotonic and cyclic loading, while Lou et al [17] provided some measurements of plasticity length scales.…”