Effect of a Non‐Continuous Composite Path with Zero Overlapping Rate on Cutoff Value of Detail Fatigue Rated Strength of Aerospace Titanium Alloy TC4 Under Laser Shock Peening

Chengrun Ye; Jianyu Sun; Yingbin Long; Xujie Zhao; Zenghuan Zhang; Zhengrong Yu; Yujie Peng; Yuxin Leng

doi:10.3788/CJL231427

Chinese Journal of Lasers, Volume. 51, Issue 20, 2002202(2024)

Effect of a Non‐Continuous Composite Path with Zero Overlapping Rate on Cutoff Value of Detail Fatigue Rated Strength of Aerospace Titanium Alloy TC4 Under Laser Shock Peening

Chengrun Ye¹, Jianyu Sun^1,2, Yingbin Long^1、*, Xujie Zhao³, Zenghuan Zhang³, Zhengrong Yu³, Yujie Peng¹, and Yuxin Leng^1、****

Author Affiliations

¹State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-Intense Laser Science,Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences (CAS), Shanghai 201800, China

²Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China

³Commercial Aircraft Corporation of China Ltd. (COMAC), Shanghai 200126, China

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Figures & Tables(17)

Fig. 1. Size of TC4 alloy sample

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Fig. 2. LSP device diagram

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Fig. 3. LSP path and LSPed sample surface. (a) LSP path; (b) actual surface of TC4 sample after LSP

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Fig. 4. TEM photographs of TC4 alloy before and after LSP. (a)(b) TC4 specimen before LSP; (c)(d) LSP12 specimen

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Fig. 5. LSP loading curve

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Fig. 6. Surface residual stress distributions after LSP on single side for TC4 titanium alloy. (a) Top view of stress distribution of the overall specimen; (b) partially enlarged view of arc inner wall

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Fig. 7. Residual stress distribution curves of TC4 alloy peened by single-sided laser shock. (a) Residual stress curve in the X-direction; (b) residual stress curve along thickness direction

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Fig. 8. Comparison of residual stresses in TC4 specimens after LSP with different parameters. (a) Overlapping rate 0; (b) overlapping rate 25%; (c) overlapping rate 50%; (d) location of residual stress testing points

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Fig. 9. Fatigue performance of TC4 specimens before and after LSP. (a) DFR_cutoff values ; (b) S-N fatigue life curves

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Table 1. Chemical composition of TC4 titanium alloy
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Table 1. Chemical composition of TC4 titanium alloy
Element Mass fraction /%
H 0.002
N 0.003
C 0.03
O 0.11
Fe 0.12
V 4
Al 6.1
Ti Bal.

Table 2. Mechanical properties of TC4 titanium alloy^[4,40,43]
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Table 2. Mechanical properties of TC4 titanium alloy^[4,40,43]
Mechanical property Value
Density ρ /（kg/m³） 4500
Elastic modulus E /GPa 110
Elongation δ /% 13
Poisson ratio ν 0.34
Tensile strength σ_b /MPa 975
Yield strength σ_0.2 /MPa 890

Table 3. Laser shock peening (LSP) parameters

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Table 3. Laser shock peening (LSP) parameters

LSP parameter	Value
Pulse energy /J	10
Central wavelength /nm	1064
Pulse width /ns	9.5
Repetition frequency /Hz	1
Pulse number /shock	1
Spot diameter /mm	2.5
Energy distribution	Flat-top
Laser power density /（GW/cm²）	6， 8， 10， 12

Table 4. Surface roughness of TC4 under different LSP conditions
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Table 4. Surface roughness of TC4 under different LSP conditions
Specimen No. Overlapping rate /% Average R_a /μm
LSP8 0 4.174
LSP8 25 2.709
LSP8 50 4.588
LSP10 0 3.812
LSP10 25 4.939
LSP10 50 4.219
LSP12 0 4.291
LSP12 25 4.186
LSP12 50 3.797

Table 5. Surface roughness comparison between LSP10 treatment area and untreated area
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Table 5. Surface roughness comparison between LSP10 treatment area and untreated area
Specimen No. Overlapping rate /% Average R_a /μm
LSP area Untreated area
LSP10 0 3.812 4.625
LSP10 25 4.939 3.896
LSP10 50 4.219 3.835

Table 6. Main parameters of TC4 titanium alloy in J‒C model^[38]
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Table 6. Main parameters of TC4 titanium alloy in J‒C model^[38]
Parameter Value
ρ /（kg·cm^-3） 4500
${\dot{ε}}_{0}$ 1
m 1.1
A /MPa 1098
B /MPa 1092
n 0.93
C 1.1

Table 7. Fatigue life test results of TC4 samples

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Table 7. Fatigue life test results of TC4 samples

Specimen No.	Maximum stress /MPa	Fatigue life /cycle	Specimen No.	Maximum stress /MPa	Fatigue life /cycle
Untreated-1	420	169912	LSP10-1	480	165656
Untreated-2	420	284761	LSP10-2	480	215752
Untreated-3	420	176616	LSP10-3	480	193742
Untreated-4	420	198024	LSP10-4	480	251232
Untreated-5	420	257204	LSP10-5	480	224612
Untreated-6	420	225718	LSP10-6	480	193624
Untreated-7	420	294875	LSP10-7	480	178533
Untreated-8	420	176584	LSP10-8	480	201648
LSP8-1	470	223615	LSP12-1	500	180315
LSP8-2	470	193784	LSP12-2	500	162697
LSP8-3	470	176193	LSP12-3	500	223375
LSP8-4	470	236419	LSP12-4	500	171641
LSP8-5	470	195049	LSP12-5	500	255214
LSP8-6	470	156193	LSP12-6	500	175556
LSP8-7	470	165483	LSP12-7	500	265974
LSP8-8	470	184623	LSP12-8	500	364632

Table 8. Confidence coefficient S_C for_{confidence of 95%^[44]}
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Table 8. Confidence coefficient S_C for_{confidence of 95%^[44]}
n S_C（for titanium alloy）
2 1.34
3 1.276
4 1.245
5 1.218
6 1.205
7 1.19
8 1.165
9 1.16

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Chengrun Ye, Jianyu Sun, Yingbin Long, Xujie Zhao, Zenghuan Zhang, Zhengrong Yu, Yujie Peng, Yuxin Leng. Effect of a Non‐Continuous Composite Path with Zero Overlapping Rate on Cutoff Value of Detail Fatigue Rated Strength of Aerospace Titanium Alloy TC4 Under Laser Shock Peening[J]. Chinese Journal of Lasers, 2024, 51(20): 2002202

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