Flat-cladding fibre bragg grating sensors for large strain fatigue tests
thesisposted on 24.05.2021, 14:19 authored by Cheng Li
In the design of mechanical components, the fatigue of material are of particular importance as ~80% of metal failures in practice arise from fatigue. The fatigue life is generally determined from low cyclic fatigue tests at large strain. This thesis developed a novel flat-cladding Fiber Bragg Grating sensor array applied in the characterization of LCF properties of three different specimens. With a new bonding process, large strain amplitude measurement of up to [plus or minus] 8000 μ [epsilon] was achieved in the Aluminum base metal and asymmetric hysteresis loops at high strain amplitudes due to twinning in compression and subsequent detwinning in tension was observed in Magnesium alloy. Moreover, an abnormal softening and hardening variation in different zone of friction stir welded Aluminum alloy was discovered throught the FBG sensor distribution. The validity shows that the FBG sensor a vital tool in the LCF tests at large strain amplitudes. Furthermore, due to its small size, the multiplexed FBG sensor array could also be applied to the measurements of strain distribution.