1. Introduction
Besides the material properties and structures of specimens, machined surface integrity has a great effect on the fatigue performance. Surface micro-topography, one of the most basic indicators of surface integrity, can form the stress concentration phenomenon on a machined surface, thus influencing the fatigue performance of specimens [1]. Generally, the degree of stress concentration on a machined surface can be expressed by stress concentration factor Kt, as follows [2].
(1)
where λ refers to the ratio between the spacing and depth of asperities, Rz is the 10-point surface roughness, and ρ is the effective profile valley radius of surface texture.According to the basic definition of Kt, many scholars have studied the effect mechanism of Kt on the fatigue behavior of specimens. The research results of Arola and Williams [3] showed that the high-cycle fatigue life of specimens decreased with the increase of surface roughness. Ås et al. [4] studied the relationship between the surface crack initiation location and the surface stress concentration by combining with specific test methods. These results show that the machined surface stress concentration formed by surface micro-topography has a great effect on the fatigue performance of specimens, and the more severe surface microscopic stress concentration, the greater the stress concentration factor Kt, and the worse the fatigue performance of specimens.
Nevertheless, some studies show that when the microscopic stress concentration phenomenon formed by surface micro-topography is controlled within a certain range, surface hardening, surface residual compressive stress and surface material structure refinement formed by plastic deformation on the machined surface can effectively inhibit the initiation of surface cracks, thus positively influencing the fatigue performance of specimens. Li [5] studied the comparison between conventional cutting and ultrasonic vibration cutting for Ti-6Al-4V, and the fatigue life of specimens machined by ultrasonic vibration cutting is 11.4 times of that by conventional cutting. Pramanik et al. [6] further found that even if the surface roughness of specimens is high, the fatigue performance can still be enhanced by the residual compressive stress caused by machined surface plastic deformation. Therefore, in order to pursue better fatigue performance, the surface strengthening methods, such as shot peening, rolling or optimization of the machining parameters, are often utilized, so that a plastic deformation layer is formed on the machined surface of parts.
On the other hand, the experimental results of some studies show that plastic deformation has different effects on the high- and low-cycle fatigue of specimens. Villegas [7] and Shaw [8] studied the effect of shot peening on the fatigue performance of specimens. The results showed that severe plastic deformation can significantly improve the high-cycle fatigue performance and reduce the low-cycle fatigue performance of specimens. Ding [9] and Kim [10] obtained approximate results that the fatigue load exceeds the threshold stress of specimens, the surface residual compressive stress is released, accelerating the crack initiation and propagation process and decreasing the fatigue performance of specimens. Klotz [11] concluded that using a large shot peening strength to obtain large surface plastic deformation will lead to an increase in surface roughness, resulting in a decrease in the low-cycle fatigue performance of specimens.
As can be seen from the above achievements, most of these studies attribute the decreased low-cycle fatigue performance of specimens to the redistribution of surface residual stress and large surface roughness. However, these studies are not comprehensive and complete enough. The effect mechanism of surface plastic deformation on the fatigue performance of specimens with controlled surface micro-topography and cutting temperature is not clear.
In this study, a typical elastic-plastic metal material 20Cr and a typical material TC17 for aerospace manufacturing were used. Based on the above previous research results, this paper referred to relevant studies on the optimization of milling parameters [12,13], and the effect of milling parameters on the degree of machined surface plastic deformation [14,15], different milling machining conditions were used to form different surface plastic deformation of 20Cr and TC17 specimens. The high- and low-cycle fatigue performances were tested on the premise that the surface micro-topography and surface residual stress were basically the same. Moreover, the experimental results were analyzed in-depth to study the effect and mechanism of machined surface plastic deformation on the high- and low-cycle fatigue performances of specimens, which provides an important reference for the optimization of the machined surface plastic deformation in practical engineering.
This paper is organized as follows: Section 2 describes the materials, specimens, measurement methods and equipment for surface integrity used in the study. Section 3 presents the measurement results of surface integrity, the test methods and results of fatigue performance, and fracture morphology. The test results are discussed in Section 4 and are summarized in Section 5.
2. Experiments
2.1. Materials and Specimens
The experimental materials were 20Cr and TC17. As per GB/T 228.1–2010, the main mechanical properties at room temperature were tested on standard specimens by a material tensile testing machine (Instron 8801, Boston, MA, USA) at a tensile rate of 2 mm/min, as shown in Table 1. Table 2 and Table 3 list the materials’ chemical composition.
TiAlN coated carbide end milling cutters were used for side and down milling of specimens. Water-based cutting fluid was used for cooling and lubrication. The typical dimensions and mounting of specimens are shown in Figure 1. The length of the gauge section was 6 mm, the diameter after milling was 5 mm, and the specimens had a 60-sided regular polygon cross-section [16]. Characteristics of cutters are listed in Table 4 and the specific experimental parameters are shown in Table 5.
2.2. Surface Integrity Measurement
Measurements of surface integrity indexes were performed on milled specimens, and each value was tested five times and averaged. Surface roughnesses were measured by a stylus-type surface roughness measuring instrument (TIME 3220, Time Group Inc., Beijing, China). The sampling length was set to 0.8 mm, the evaluation length was set to 4 mm, and the measurement direction was parallel to the feed direction. Ra and Rz were used to evaluate the microscopic topography of the machined surface. Surface residual stresses along the axial direction were measured using X-ray diffraction, which is a simple and efficient method, and an X-ray diffractometer (AutoMATE II, Nippon Rigaku Co., Tokyo, Japan) was used. For 20Cr specimens, the diffraction angle was 156.4°, the exposure time was 20 s, and the aperture diameter was 2 mm. For TC17 specimens, the diffraction angle was 140°, the exposure time was 80 s, and the aperture diameter was 1 mm. Surface hardness measurements were performed on a nano-indentation tester (TTX-NHT3, Anton Paar, Graz, Austria). The maximum load used was 100 mN, corresponding to a retention time of 30 s for the maximum load and the loading and unloading rates were both 10 mN/s. Cut sections were tested in the same way to obtain the hardness of substrate materials, and cut sections were ground and polished. Micro-hardness HVIT of 20Cr and TC17 substrate materials is about 273 and 513 HV, separately. Microstructures of cut sections were observed with a Cam-Scan CS3400 (Cambridge shire, UK) scanning electron microscope (SEM).
3. Results
3.1. Surface Integrity Test Results
The measurement results of surface roughness, surface hardness and surface residual stress of 20Cr and TC17 specimens are shown in Table 6.
As shown in Table 6, for 20Cr specimens under two milling conditions (Exp. 1 and Exp. 2), the surface roughness and surface residual stress are almost the same when the milling depth ae is changed. In contrast, the surface nano-hardnesses and surface micro-hardnesses of Exp. 2 specimens are significantly greater than those of Exp. 1 specimens, which is because the larger depth of cut (ae = 0.7 mm) of Exp. 2 specimens compared to the 0.1 mm depth of cut of Exp. 1 specimens causes a significant extrusion effect on the surface, making cutting force increases, thus intensifying the hardening of the surface layer material.
A comparative analysis of Exp. 3 and Exp. 4 shows that the degree of surface plastic deformation of specimens increases with the decrease of milling speed and the increase of milling depth, which is manifested by the increase of surface hardness and surface residual compressive stress, as shown in Table 3. For TC17 specimens, the milling parameters of Exp. 3 and Exp. 4 do not significantly affect the surface roughness of specimens.
In terms of the machining mechanism, the surface layer material will inevitably generate plastic deformation during the milling process, which directly impacts its mechanical properties. Therefore, compared to the substrate material, the material properties of the machined surface layer will have a significantly higher yield strength and a significantly reduced range of plastic deformation available [17], as shown in Figure 2. Fatigue cracks generally occur on machined surfaces or subsurfaces, and high yield strength and plastic deformation on the surface can effectively inhibit fatigue fracture initiation and improve the fatigue performance of specimens [18].
Meanwhile, the surface microstructure of 20Cr and TC17 specimens with different machining parameters were examined by SEM, as shown in Figure 3. Due to the shear strain caused by the mutual extrusion between the tool and the specimen surface, fibrous deformation of microstructures along the tool feed direction can be observed of all Exp. 1–4 specimens. Additionally, the type of structure of the machined surface does not change due to the reasonable choice of milling parameters [19]. Exp. 2 or Exp. 4 specimens have more severe surface plastic deformation than Exp. 1 or Exp. 3 specimens, respectively, which is consistent with the above analysis of the surface integrity.
In order to obtain the yield strength of the surface material, a nano-indentation tester (TTX-NHT3, Anton Paar, Graz, Austria) was used to examine the nano-indentation hardness HIT, and the yield strength σs can be obtained from the empirical formula HIT = aσs + b [20]. Yield strength of the substrate material in Table 1 was used for the base validation calculation, where a = 5.23 and b = 5.63 GPa for 20Cr specimens and a = 4.46 and b = 4.24 GPa for TC17 specimens. The calculated results are shown in Table 7, corresponding to the actual properties. It can be seen that, as the degree of machined surface plastic deformation of specimens increases, so does the yield strength of the surface material.
3.2. Fatigue Performance Test and Fracture Analysis of Specimens
The fatigue performance of 20Cr and TC17 specimens was tested on a high-frequency digital fatigue testing machine (GPS-100, Sino test Equipment Co., Ltd., Changchun, China). In order to study the effect of milling surface plastic deformation on the high- and low-cycle fatigue performance of specimens, respectively, the maximum stresses were 600 MPa, 640 MPa, 660 MPa and 680 MPa for 20Cr specimens and 1060 MPa, 1080 MPa, 1090 MPa, 1100 MPa, 1120 MPa and 1140 MPa for TC17 specimens. The cyclic stress ratio R is 0.1 and the test frequency is about 110 Hz.
3.2.1. 20Cr Specimens
From the number of cycles to failure Nf of 20Cr specimens, as shown in Figure 4, the effect of surface plastic deformation on the fatigue performance under different load conditions is entirely different. Nf of Exp. 2 specimens is greater than that of Exp. 1 specimens when σmax is less than 630 MPa; when σmax is greater than 630 MPa, the results are just the opposite. So, there is a crossover point at the threshold stress σmax = 630 MPa in σmax—Nf curves of 20Cr specimens.
The fatigue fracture surface of 20Cr specimens was observed by SEM, as shown in Table 8. When σmax is less than the threshold stress (630 MPa), i.e., when specimens are subjected to small alternating loads, there is no microcrack on the surfaces of specimens under two milling conditions and the fatigue source of the fracture surface is obvious and clear. Besides, the fatigue source initiation of the Exp. 2 specimen occurs on the subsurface. Combined with the surface integrity of Exp. 1 and Exp. 2 specimens, the surface plastic deformation of Exp. 2 specimens is more severe than that of Exp. 1 specimens, and the surface roughness and surface residual stress are almost same. Therefore, the relatively severe surface plastic deformation is the main reason for the increase of Nf.
When σmax is greater than the threshold stress (630 MPa), microcracks appear on the surface of both specimens, and the fatigue sources are not obvious. Moreover, with the increase of alternating load, the surface of Exp. 2 specimens with severe plastic deformation is more prone to microcracks, indicating that plastic deformation has a negative effect on the fatigue performance of specimens.
3.2.2. TC17 Specimens
The fatigue life of TC17 specimens is shown in Figure 5, the variation trend of Nf with the plastic deformation of the machined surface is consistent with that of Figure 4. There is also a crossover point σmax =1120 MPa in σmax—Nf curves. When σmax is less than 1120 MPa, Nf of Exp. 4 specimens is greater than that of Exp. 3 specimens, and when σmax is greater than 1120 MPa, the result is the opposite.
The fatigue fracture topography and the microscopic surface of TC17 specimens are shown in Table 9. When specimens are subjected to small alternating load (1060 MPa), the fatigue source of the Exp. 4 specimen with severe plastic deformation occurs at a deeper subsurface layer than the Exp. 3 specimen, indicating that plastic deformation has a positive effect on fatigue performance. However, microcracks already appear on the surface of TC17 specimens at σmax = 1090 MPa.
4. Discussion
From the above fatigue performance of 20Cr and TC17 specimens, it can be seen that, regardless of the mechanical properties of materials, when the specimen is subjected to a small alternating load, the machined surface plastic deformation has a positive effect on the fatigue performance, and the greater the degree of machined surface plastic deformation, the higher the fatigue life of the specimen; when the specimen is subjected to an alternating load greater than the threshold stress, the greater the degree of machined surface plastic deformation, the lower the fatigue life of the specimen. The experimental phenomenon is also prevalent in the results of other researchers [7,8,9,10,21]. Combining the above experimental results, Nf corresponding to the threshold stress is generally between 3 × 104 and 5 × 105, regardless of the material used and the processing method. Therefore, it can also be concluded that the machined surface plastic deformation of specimens has a positive effect on the high-cycle fatigue performance, while on the contrary, it has a negative effect on the low-cycle fatigue performance of specimens.
Stress concentration caused by the surface topography inevitably appears on the machined surface when the specimen is subjected to axial loads, as shown in Figure 6a. This stress concentration due to the deformation at the bottom of the circular notch of the surface cutting topography is a strain concentration essentially. As shown in Figure 6b, the actual strain εa at the bottom of the circular notch is larger than the nominal strain εn of the specimen under the effect of strain concentration. Especially when the specimen is subjected to a large applied load, the actual strain εa at the strain concentration on the surface will exceed the ultimate tensile strain εb of the specimen material, resulting in microcracks on the surface and a sharp decrease in the fatigue performance. However, the surface micro-topography of 20Cr specimens in both Exp. 1 and Exp. 2 is basically the same at the macroscopic scale. Therefore, the degree of stress (strain) concentration on both surfaces does not differ significantly under the same load. Meanwhile, although there is a redistribution of surface residual stress under large loads, the values of surface residual stress for Exp. 1 and Exp. 2 specimens are also essentially the same.
Actually, due to the presence of the machined surface plastic deformation, the stress (strain) concentration is generated as shown in Figure 6c,d. The Exp. 2 specimens with a more severe degree of plastic deformation have the surface material with a higher yield strength and a smaller range of plastic deformation available. Therefore, only smaller applied loads are required to cause microcracks on the surface of Exp. 2 specimens compared to Exp. 1 specimens, as shown by the difference between the two groups of fatigue fractures in Table 5 when σmax is 660 MPa.
For the test results of TC17 specimens, the change law is also basically the same as that of 20Cr specimens. However, the maximum stress σmax (1060–1140 MPa) used in the fatigue tests of TC17 specimens did not reach their yield strength (1158 MPa), and microcracks already appear on the surface at a maximum stress σmax of 1090 MPa. Combining the strength data of TC17 specimen surface material in Table 7 and Figure 6d, it can be concluded that when σmax is 1090 MPa, the actual strain εa at the strain concentration on the surface of the specimens has already exceeded the ultimate tensile strain εb′ of the surface material, thus causing microcracks to be generated on the surface.
For Exp. 1–2 or Exp. 3–4, the machined surface plastic deformation has a positive effect on the fatigue performance of specimens under small loads, and the greater the degree of machined surface plastic deformation under the same load, the better the high-cycle fatigue performance. However, the greater the degree of machined surface plastic deformation under large loads, the easier it is to generate microcracks on the surface of specimens, resulting in a sharp decrease in fatigue performance. Specifically, when εn increases or the degree of machined surface plastic deformation increases, it is possible that εa exceeds εb′, resulting in microcracks forming on the machined surface. This phenomenon, called the “over-plastic deformation” phenomenon of the machined surface, needs to be avoided.
5. Conclusions
Under the condition that surface micro-topography and surface temperature were controlled, the law and mechanism of the effect of milling surface plastic deformation on the high- and low-cycle fatigue life of 20Cr and TC17 specimens were studied, and the following conclusions were obtained:
(1) The plastic deformation on a machined surface has different effects on the high- and low-cycle fatigue performances of specimens. When the specimen is subjected to a small alternating load, severe surface plastic deformation can improve the high-cycle fatigue performance; when the specimen is subjected to a large alternating load, severe surface plastic deformation has a negative effect on the low-cycle fatigue performance. Within the experimental conditions and parameters, for TC17, the increase in the degree of surface plastic deformation can improve the high-cycle average fatigue life of specimens by up to 2.43 times; for 20Cr, the increase in the degree of surface plastic deformation reduces the low-cycle average fatigue life of specimens by up to 63.63% of the previous one;
(2) Cutting results in severed deformation on the surface of the specimen, which reduces the plasticity of the surface layer material and enhances the surface stress concentration phenomenon induced by surface micro-topography. So when the specimen is subjected to a large load, microcracks easily appear on the machined surface, and the “over-plastic deformation” phenomenon is formed, which leads to a sharp decrease in the low-cycle fatigue performance of specimens;
(3) For improving the fatigue of specimens, the plastic deformation on machined surface needs to be optimized. As the load and surface roughness rises, the degree of machined surface plastic deformation should be appropriately decreased; conversely, the degree of machined surface plastic deformation should be increased.
Conceptualization, X.L.; methodology, X.L. and Z.G.; Investigation, Z.G., S.Y. and Hongbin Zhang; writing—original draft preparation, Z.G. and S.Y.; writing—review and editing, Z.G., H.Z. and Z.W.; supervision, X.L. All authors have read and agreed to the published version of the manuscript.
This research was funded by “National Natural Science Foundation of China, grant number 51875028”.
Not applicable.
Not applicable.
Not applicable.
The authors declare no conflict of interest.
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Enlarge this image.Figure 2. Schematic diagram of the mechanical properties of materials with plastic deformed surfaces.
Enlarge this image.Figure 3. Surface microstructures of 20Cr and TC17: (a) Exp. 1, ae = 0.1 mm; (b) Exp. 2, ae = 0.7 mm; (c) Exp. 3, vs = 80 m/min, ae = 0.2 mm and (d) Exp. 4, vs = 30 m/min, ae = 0.7 mm.
Enlarge this image.Figure 6. Schematic diagram of surface stress (strain) concentration and microcrack initiation process: (a,b) for as received; (c,d) for plastic deformation surface.
Mechanical properties of experimental materials.
| Material | Young’s Modulus |
Yield Strength |
Tensile Strength |
|---|---|---|---|
| 20Cr | 192 | 473 | 897 |
| TC17 | 110 | 1158 | 1324 |
Chemical composition of 20Cr (wt.%).
| C | Cr | Mn | Fe |
|---|---|---|---|
| 0.2 | 1.21 | 1.01 | Bal. |
Chemical composition of TC17 (wt.%).
| Al | Cr | Zr | Mo | Sn | Fe | C |
|---|---|---|---|---|---|---|
| 4.9 | 4 | 1.93 | 4.18 | 2.16 | 0.03 | 0.01 |
Cutter conditions.
| Substrate Material | Cemented Carbide |
|---|---|
| Coating | TiAlN |
| Number of flutes | 4 |
| Diameter (mm) | 10 |
| Helix angle (°) | 45 |
| Photograph | [Image omitted. Please see PDF.] |
Experimental parameters.
| Experiment |
Material | Cutting Speed |
Feed per Tooth |
Depth of Cut |
|---|---|---|---|---|
| Exp. 1 | 20Cr | 20 | 0.06 | 0.1 |
| Exp. 2 | 20 | 0.06 | 0.7 | |
| Exp. 3 | TC17 | 80 | 0.18 | 0.2 |
| Exp. 4 | 30 | 0.18 | 0.7 |
Results of surface integrity measurements.
| Experiment |
Material | Roughness |
Roughness |
Nano-Hardness |
Micro-Hardness |
Residual Stress |
|---|---|---|---|---|---|---|
| Exp. 1 | 20Cr | 0.32 | 1.59 | 4.06 | 375.54 | −157.1 |
| Exp. 2 | 0.34 | 1.74 | 4.79 | 443.48 | −159.0 | |
| Exp. 3 | TC17 | 0.22 | 0.94 | 5.71 | 529.19 | −96.9 |
| Exp. 4 | 0.22 | 0.98 | 6.21 | 574.71 | −125.0 |
Calculated yield strength of 20Cr and TC17 specimens.
| Materials | Test Location | Nano-Hardness |
Yield Strength |
|---|---|---|---|
| 20Cr | Substrate material | 2.95 | 456 |
| Surface material of Exp. 1 | 4.06 | 669 | |
| Surface material of Exp. 2 | 4.79 | 808 | |
| TC17 | Substrate material | 5.54 | 1147 |
| Surface material of Exp. 3 | 5.71 | 1186 | |
| Surface material of Exp. 4 | 6.21 | 1296 |
Fracture topography and microscopic surface of 20Cr specimens.
| Load Conditions |
Exp. No. | Cutting Conditions | Fracture Topography and Surface Microcrack |
|---|---|---|---|
| 600 | Exp. 1 | vs = 20 m/min |
[Image omitted. Please see PDF.] |
| Exp. 2 | vs = 20 m/min |
[Image omitted. Please see PDF.] | |
| 660 | Exp. 1 | vs = 20 m/min |
[Image omitted. Please see PDF.] |
| Exp. 2 | vs = 20 m/min |
[Image omitted. Please see PDF.] | |
| 680 | Exp. 1 | vs = 20 m/min |
[Image omitted. Please see PDF.] |
| Exp. 2 | vs = 20 m/min |
[Image omitted. Please see PDF.] |
Fracture topography and microscopic surface of TC17 specimens.
| Load Conditions |
Exp. No. | Cutting Conditions | Fracture Topography and Surface Microcrack |
|---|---|---|---|
| 1060 | Exp. 3 | vs = 80 m/min |
[Image omitted. Please see PDF.] |
| Exp. 4 | vs = 30 m/min |
[Image omitted. Please see PDF.] | |
| 1090 | Exp. 3 | vs = 80 m/min |
[Image omitted. Please see PDF.] |
| Exp. 4 | vs = 30 m/min |
[Image omitted. Please see PDF.] | |
| 1140 | Exp. 3 | vs = 80 m/min |
[Image omitted. Please see PDF.] |
| Exp. 4 | vs = 30 m/min |
[Image omitted. Please see PDF.] |
References
1. Wang, J.J.; Wen, Z.X.; Zhang, X.H.; Zhao, Y.C.; Yue, Z.F. Effect Mechanism and Equivalent Model of Surface Roughness on Fatigue Behavior of Nickel-based Single Crystal Superalloy. Int. J. Fatigue; 2019; 125, pp. 101-111. [DOI: https://dx.doi.org/10.1016/j.ijfatigue.2019.03.041]
2. Neuber, H. Theory of Notch Stresses: Principles for Exact Calculation of Strength with Reference to Structural Form and Material; 2nd ed. Springer: Berlin, Germany, 1958.
3. Arola, D.; Williams, C.L. Estimating the fatigue stress concentration factor of machined surfaces. Int. J. Fatigue; 2002; 24, pp. 923-930. [DOI: https://dx.doi.org/10.1016/S0142-1123(02)00012-9]
4. Ås, S.K.; Skallerud, B.; Tveiten, B.W. Surface roughness characterization for fatigue life predictions using finite element analysis. Int. J. Fatigue; 2008; 30, pp. 2200-2209. [DOI: https://dx.doi.org/10.1016/j.ijfatigue.2008.05.020]
5. Li, X.; Yang, S.; Lu, Z.; Zhang, D.; Zhang, X.; Jiang, X. Influence of ultrasonic peening cutting on surface integrity and fatigue behavior of Ti-6Al-4V specimens. J. Mater. Process. Technol.; 2020; 275, 116386. [DOI: https://dx.doi.org/10.1016/j.jmatprotec.2019.116386]
6. Pramanik, A.; Dixit, A.R.; Chattopadhyaya, S.; Uddin, M.S.; Dong, Y.; Basak, A.K.; Littlefair, G. Fatigue life of machined components. Adv. Manuf.; 2017; 5, pp. 59-76. [DOI: https://dx.doi.org/10.1007/s40436-016-0168-z]
7. Villegas, J.C.; Shaw, L.L.; Dai, K.; Yuan, W.; Tian, J.; Liaw, P.K.; Klarstrom, D.L. Enhanced fatigue resistance of a nickel-based hastelloy induced by a surface nanocrystallization and hardening process. Philos. Mag. Lett.; 2005; 85, pp. 427-438. [DOI: https://dx.doi.org/10.1080/09500830500311705]
8. Shaw, L.L.; Tian, J.W.; Ortiz, A.L.; Dai, K.; Villegas, J.C.; Liaw, P.K.; Ren, R.; Klarstrom, D.L. A direct comparison in the fatigue resistance enhanced by surface severe plastic deformation and shot peening in a C-2000 superalloy. Mater. Sci. Eng. A; 2010; 527, pp. 986-994. [DOI: https://dx.doi.org/10.1016/j.msea.2009.10.028]
9. Ding, X.; Huang, D.; Yan, X.; Fan, J.; Qi, M.; Liu, Z. Effect of pneumatic shot peening on the high and low cycle combined fatigue life of K403 turbine blades. Fatigue Fract. Eng. Mater. Struct.; 2021; 44, pp. 1439-1454. [DOI: https://dx.doi.org/10.1111/ffe.13440]
10. Kim, J.C.; Cheong, S.K.; Noguchi, H. Residual stress relaxation and low- and high-cycle fatigue behavior of shot-peened medium-carbon steel. Int. J. Fatigue; 2013; 56, pp. 114-122. [DOI: https://dx.doi.org/10.1016/j.ijfatigue.2013.07.001]
11. Klotz, T.; Delbergue, D.; Bocher, P.; Lévesque, M.; Brochu, M. Surface characteristics and fatigue behavior of shot peened Inconel 718. Int. J. Fatigue; 2018; 110, pp. 10-21. [DOI: https://dx.doi.org/10.1016/j.ijfatigue.2018.01.005]
12. Pimenov, D.Y.; Abbas, A.T.; Gupta, M.K.; Erdakov, I.N.; Soliman, M.S.; El Rayes, M.M. Investigations of surface quality and energy consumption associated with costs and material removal rate during face milling of AISI 1045 steel. Int. J. Adv. Manuf. Technol.; 2020; 107, pp. 3511-3525. [DOI: https://dx.doi.org/10.1007/s00170-020-05236-7]
13. Abbas, A.T.; Pimenov, D.Y.; Erdakov, I.N.; Mikolajczyk, T.; Soliman, M.S.; El Rayes, M.M. Optimization of cutting conditions using artificial neural networks and the Edgeworth-Pareto method for CNC face-milling operations on high-strength grade-H steel. Int. J. Adv. Manuf. Technol.; 2019; 105, pp. 2151-2165. [DOI: https://dx.doi.org/10.1007/s00170-019-04327-4]
14. dos Santos, C.E.; Carneiro, J.R.G.; da Silva, G.C.; Brito, P.P.; dos Santos, Í.B.; Campos, T.R. Residual stress and surface microhardness post-milling in 2205 duplex steel. Int. J. Adv. Manuf. Technol.; 2021; 113, pp. 3445-3455. [DOI: https://dx.doi.org/10.1007/s00170-021-06829-6]
15. Sun, J.; Guo, Y.B. A comprehensive experimental study on surface integrity by end milling Ti–6Al–4V. J. Mater. Process. Technol.; 2009; 209, pp. 4036-4042. [DOI: https://dx.doi.org/10.1016/j.jmatprotec.2008.09.022]
16. Li, X.; Wang, Y.; Xu, R.; Yang, S.; Guan, C.; Zhou, Y. Influence of surface integrity on fatigue behavior of Inconel 718 and Ti6Al4V workpieces with CBN electroplated wheel. Int. J. Adv. Manuf. Technol.; 2019; 102, pp. 2345-2356. [DOI: https://dx.doi.org/10.1007/s00170-019-03345-6]
17. Meng, L.; Zhang, Z.; Zhang, Y.; Zhang, J.; Yang, X.; Gao, H.; Shu, B.; Zhu, X. The influence of stacking fault energy on mech anical properties of Cu-Al-Zn alloys processed by surface mechanical attrition treatment, Mater. Sci. Eng. A; 2019; 744, pp. 235-240. [DOI: https://dx.doi.org/10.1016/j.msea.2018.12.021]
18. Xu, X.; Liu, D.; Zhang, X.; Liu, C.; Liu, D.; Zhang, W. Influence of ultrasonic rolling on surface integrity and corrosion fatigue behavior of 7B50-T7751 aluminum alloy. Int. J. Fatigue; 2019; 125, pp. 237-248. [DOI: https://dx.doi.org/10.1016/j.ijfatigue.2019.04.005]
19. Yue, C.; Gao, H.; Liu, X.; Liang, S.Y. Part Functionality Alterations Induced By Changes of Surface Integrity in Metal Milling Process: A Review. Appl. Sci.; 2018; 8, 2550. [DOI: https://dx.doi.org/10.3390/app8122550]
20. Rodrıguez, R.; Gutierrez, I. Correlation between nanoindentation and tensile properties: Influence of the indentation size effect. Mater. Sci. Eng. A; 2003; 361, pp. 377-384. [DOI: https://dx.doi.org/10.1016/S0921-5093(03)00563-X]
21. Tian, J.W.; Villegas, J.C.; Yuan, W.; Fielden, D.; Shaw, L.; Liaw, P.K.; Klarstrom, D.L. A study of the effect of nanostructured surface layers on the fatigue behaviors of a C-2000 superalloy. Mater. Sci. Eng. A; 2007; 468, pp. 164-170. [DOI: https://dx.doi.org/10.1016/j.msea.2006.10.150]
© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.