scholarly journals Flat-Cladding Fiber Bragg Grating Sensors for Large Strain Amplitude Fatigue Tests

2021 ◽  
Author(s):  
Aihen Feng ◽  
Daolun Chen ◽  
Cheng Li ◽  
Xijia Gu
Keyword(s):  
Fiber Bragg Grating ◽  
Strain Amplitude ◽  
Large Strain ◽  
Hysteresis Loops ◽  
Cyclic Strain ◽  
Fatigue Tests ◽  
Bragg Grating ◽  
Large Strain Amplitude ◽  
Bragg Grating Sensor ◽  
Cyclic Strain Amplitude

We have successfully developed a flat-cladding fiber Bragg grating sensor for large cyclic strain amplitude tests of up to ±8,000 με. The increased contact area between the flat-cladding fiber and substrate, together with the application of a new bonding process, has significantly increased the bonding strength. In the push-pull fatigue tests of an aluminum alloy, the plastic strain amplitudes measured by three optical fiber sensors differ only by 0.43% at a cyclic strain amplitude of ±7,000 με and 1.9% at a cyclic strain amplitude of ±8,000 με. We also applied the sensor on an extruded magnesium alloy for evaluating the peculiar asymmetric hysteresis loops. The results obtained were in good agreement with those measured from the extensometer, a further validation of the sensor.

scholarly journals Flat-Cladding Fiber Bragg Grating Sensors for Large Strain Amplitude Fatigue Tests

2021 ◽  
Author(s):  
Aihen Feng ◽  
Daolun Chen ◽  
Cheng Li ◽  
Xijia Gu
Keyword(s):  
Fiber Bragg Grating ◽  
Strain Amplitude ◽  
Large Strain ◽  
Hysteresis Loops ◽  
Cyclic Strain ◽  
Fatigue Tests ◽  
Bragg Grating ◽  
Large Strain Amplitude ◽  
Bragg Grating Sensor ◽  
Cyclic Strain Amplitude

We have successfully developed a flat-cladding fiber Bragg grating sensor for large cyclic strain amplitude tests of up to ±8,000 με. The increased contact area between the flat-cladding fiber and substrate, together with the application of a new bonding process, has significantly increased the bonding strength. In the push-pull fatigue tests of an aluminum alloy, the plastic strain amplitudes measured by three optical fiber sensors differ only by 0.43% at a cyclic strain amplitude of ±7,000 με and 1.9% at a cyclic strain amplitude of ±8,000 με. We also applied the sensor on an extruded magnesium alloy for evaluating the peculiar asymmetric hysteresis loops. The results obtained were in good agreement with those measured from the extensometer, a further validation of the sensor.

scholarly journals Flat-Cladding Fiber Bragg Grating Sensors for Large Strain Amplitude Fatigue Tests

Sensors ◽  
2010 ◽  
Vol 10 (8) ◽  
pp. 7674-7680 ◽  
Author(s):  
Aihen Feng ◽  
Daolun Chen ◽  
Cheng Li ◽  
Xijia Gu
Keyword(s):  
Fiber Bragg Grating ◽  
Strain Amplitude ◽  
Large Strain ◽  
Fatigue Tests ◽  
Bragg Grating ◽  
Fiber Bragg Grating Sensors ◽  
Large Strain Amplitude

scholarly journals Flat-cladding fibre bragg grating sensors for large strain fatigue tests

2021 ◽  
Author(s):  
Cheng Li
Keyword(s):  
Sensor Array ◽  
Large Strain ◽  
Hysteresis Loops ◽  
Cyclic Fatigue ◽  
Fatigue Tests ◽  
Bragg Grating ◽  
Fibre Bragg Grating ◽  
Friction Stir ◽  
Fbg Sensor ◽  
Large Strain Amplitude

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.

scholarly journals Flat-cladding fibre bragg grating sensors for large strain fatigue tests

2021 ◽  
Author(s):  
Cheng Li
Keyword(s):  
Sensor Array ◽  
Large Strain ◽  
Hysteresis Loops ◽  
Cyclic Fatigue ◽  
Fatigue Tests ◽  
Bragg Grating ◽  
Fibre Bragg Grating ◽  
Friction Stir ◽  
Fbg Sensor ◽  
Large Strain Amplitude

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.

Low-Cycled Fatigue Life of S30408 Stainless Steel at Liquid-Nitrogen Temperature

2018 ◽  
Author(s):  
Yingzhe Wu ◽  
Huaijian Xu ◽  
Qunjie Lu ◽  
Jinyang Zheng ◽  
Ping Xu
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Liquid Nitrogen ◽  
Strain Amplitude ◽  
Hysteresis Loops ◽  
Cyclic Strain ◽  
Liquid Nitrogen Temperature ◽  
Cyclic Stress ◽  
Cyclic Softening ◽  
Fatigue Tests

This paper is concerned with the low-cycled fatigue life of S30408 austenitic stainless steel at 77 K. Strain-controlled low-cycled fatigue tests were performed in a liquid-nitrogen bath covering a strain-amplitude range of 0.4%–1.0%. The role of the reduced temperature is examined during the low-cycled fatigue tests by comparing the fatigue performance to the one at ambient temperature that was obtained in our previous work. It is found that the cryogenic low-cycled fatigue life is significantly improved by a factor of 5–10 in the low strain-amplitude range of 0.4%–0.5%, resulting from the pronounced hardening effect due to the low temperature. However, the cryogenic improvement gradually reduces with the increasing strain-amplitude. At 77 K, the cyclic stress amplitude increases rapidly at the beginning of the fatigue test, and no cyclic softening is found due to the cryogenically constrained movement of the dislocations. The fatigue hysteresis loops and fatigue stress-strain curves shows that the cyclic plastic strain at cryogenic temperature accounts for a limited proportion in the total cyclic strain, and the damage may occurs explosively at the beginning of the cyclic load at 77 K.

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