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SUMMARY:Finite element modeling of a bidirectional origami microactuat
 or system - Ning Zhang
UID:2f5656cc-e55b-43fa-a050-b950ec989321
DESCRIPTION:Ning Zhang WW8\, FAU 05. November 2025\, 17:00 WW8\, Fürt
 h Over the past several decades\, functional materials have attracted 
 extensive research interest. Among them\, shape memory alloys (SMAs) h
 ave shown tremendous potential for a wide range of applications\, owin
 g to their relatively high specific actuation energy\, biocompatibilit
 y\, and distinctive shape memory and pseudoelastic behaviors. However\
 , the practical application of such materials\, especially thermal SMA
 s\, is often limited by low actuation frequencies. To investigate and 
 evaluate the performance and complex behavior of an origami inspired b
 i-directional microactuator\, this thesis implements a fully coupled t
 hermal-electrical-structural phenomenological constitutive model for S
 MAs through a user-defined subroutine (UMAT) in Abaqus. The model is f
 irst validated against experimental data via simulated tensile tests c
 onducted below the martensite finish temperature to capture the shape 
 memory effect\, and above the austenite finish temperature to characte
 rize pseudoelasticity. Key parameters\, including transformation strai
 ns\, critical transformation stresses\, and Clausius-Clapeyron coeffic
 ients\, are extracted\, showing excellent agreement with reference dat
 a\, with a mean absolute percentage error of 0.04%. Subsequently\, the
  validated model is applied to a bi-directional microactuator. The sim
 ulation in this work encompasses the entire actuation cycle\, includin
 g shape-setting\, mechanical loading\, thermal activation via Joule he
 ating and convective cooling. The results successfully demonstrate the
  reversible and bi-directional motion of the actuator\, achieving angu
 lar displacements of approximately ±124°. Analysis of the underlying
  martensitic volume fraction reveals its direct correlation with the m
 acroscopic actuation. Furthermore\, the study identifies the heating a
 nd convective cooling processes as the primary factor limiting the act
 uation frequency\, which is calculated to be 0.027 Hz f
DTSTART:20251112T160000Z
DTEND:20251112T170000Z
LOCATION:WW8\, Room 2.018-2\, Dr.-Mack-Str. 77\, Fürth
DTSTAMP:20260528T054743Z
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