scholarly journals Understanding the Relations between Surface Stress State and Microstructure Feature for Enhancing the Fatigue Performance of TC6 Titanium Alloy

Coatings ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1261
Author(s):  
Song Shu ◽  
Xin Huang ◽  
Zonghui Cheng ◽  
Yizhou Shen ◽  
Zhaoru He ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Fatigue Life ◽  
Stress State ◽  
Surface Stress ◽  
Strengthening Mechanism ◽  
Fatigue Performance ◽  
Shock Peening ◽  
The Relationship ◽  
Change Of Microstructure ◽  
Improve Fatigue

Fatigue performance has always been an important factor affecting the application of titanium alloy. The service life of TC6 titanium alloy is easily reduced under a continuously alternating load. Therefore, there is an urgent need for a new method to improve fatigue performance. Laser shock peening (LSP) is a widely proposed method to enhance the fatigue performance. Here, through experiments and finite element simulations, it was found that LSP can prolong the fatigue life of TC6 by improving the surface stress state. In strengthening processes, the generation of residual stress was mainly attributed to the change of microstructure, which could be reflected by the statistical results of grain sizes. The content of grains with a size under 0.8 μm reached 78%, and the microhardness value of treated TC6 was 18.7% higher than that of an untreated sample. In addition, the surface residual compressive stress was increased to −600 MPa at the depth of 1500 μm from the surface. On this basis, the fatigue life was prolonged to 135%, and the ultimate fracture macroscopic was also changed. With the treatment of LSP, the fatigue performance of TC6 is highly promoted. The strengthening mechanism of LSP was established with the aim of revealing the relationship between microstructure and stress state for enhancing the fatigue performance in whatever shapes.

Characterization of TC17 Titanium Alloy Treated by Square-Spot Laser Shock Peening

2013 ◽  
Vol 652-654 ◽  
pp. 2378-2383 ◽  
Author(s):  
Zi Wen Cao ◽  
Shui Li Gong ◽  
Yu Gao
Keyword(s):  
Titanium Alloy ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Stress Gradient ◽  
Laser Shock Peening ◽  
Fatigue Performance ◽  
Specimen Thickness ◽  
Laser Shock ◽  
Shock Peening ◽  
Square Spot

Laser shock peening (LSP) is widely known as a cold-worked surface treatment, and this technology has been to greatly improve the fatigue life of many metallic components. Our works focused on laser shock peening with Nd: glass laser system (pulse duration 30ns) and square laser spot size of 4mm×4mm for TC17 titanium alloy. Surface morphology, residual stresses and fatigue performance had been studied for TC17 alloy specimens and blades processed by LSP treatment. The results show that plastic strains in shocked dents become more homogeneous than ones produced by original circle spot with gaussian energy distribution. Surface residual stresses which measured using x-ray diffraction method showed different characteristic as varying specimen thickness, and LSP with overlapping ratio of 8% provided uniform residual stresses on peened surface. Low fluence peening which was implemented at borderline of peened surface was effective to diminish the stress gradient. Compared with mechanical shot peening, LSP attained smoother surface, lower microhardness and better fatigue performance. In a word, Square-spot LSP is an excellent way to improve fatigue life of titanium blade.

Effects of countersunk hole geometry errors on the fatigue performance of CFRP bolted joints

2021 ◽  
pp. 095440542110285
Author(s):  
Xuda Qin ◽  
Xingfeng Cao ◽  
Hao Li ◽  
Meng Zhou ◽  
Ende Ge ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Bolted Joints ◽  
Fatigue Performance ◽  
Machining Process ◽  
Fe Model ◽  
Hole Making ◽  
Hole Geometry ◽  
Geometry Error ◽  
The Relationship ◽  
Hole Machining

Due to good aerodynamic performance and reliability, countersunk bolt joint is one of the most commonly used connection methods for carbon fiber reinforced polymer (CFRP) components in the aircraft. However, the countersunk hole machining process is inevitably accompanied by geometric errors, which will directly affect the mechanical properties of the joint structure. This paper presents a numerical and experimental investigation on the effect of countersunk hole geometry errors on the fatigue performance of CFRP bolted joints. FE model of CFRP countersunk bolted joints with designed geometry errors are established, and the rationality of the FE analysis was verified by fatigue life and failure forms. The CFRP bolted structure failure mechanism under fatigue load and influence of hole-making geometry error (including countersunk fillets radius, countersunk depth, and countersunk angle) on the fatigue life are investigated. Based on the relationship between fatigue life and the geometry error, the corresponding tolerances for CFRP bolt joint countersunk hole are determined as well. The research results can provide a reference for establishing reasonable geometric accuracy requirements for CFRP joint hole machining.

Effect of [Al]s, [Mg], [Ca] in Molten Steel on Inclusion Content for High Speed Wheel Steel during LF-VD Process

2014 ◽  
Vol 898 ◽  
pp. 60-63
Author(s):  
Yu Tang
Keyword(s):  
Fatigue Life ◽  
Molten Steel ◽  
High Speed ◽  
Refining Process ◽  
Fatigue Performance ◽  
Wheel Steel ◽  
Inclusion Content ◽  
High Basicity ◽  
Secondary Refining ◽  
Improve Fatigue

In order to improve fatigue life of wheel steel, LF-VD secondary-refining process is done with Al-deoxidation and slag of high basicity, high Al2O3 content and low oxidizing property. Inclusion content would be influenced by [Al]s, [Mg], [Ca] in molten steel. It is found that Al2O3 inclusions, which are the products of Al-deoxidation, would react with [Mg], [Ca] in molten steel to transform into CaO-MgO-Al2O3 complex inclusions, which is the key for the enhancement of fatigue performance for wheel steel.

scholarly journals Improvement of Fatigue Life of GH3039 Superalloy by Laser Shock Peening

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3849
Author(s):  
Yang Tang ◽  
MaoZhong Ge ◽  
Yongkang Zhang ◽  
Taiming Wang ◽  
Wen Zhou
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Surface Profile ◽  
Optical Microscope ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Transmission Electron ◽  
Before And After ◽  
Shock Peening ◽  
Improve Fatigue

In order to improve fatigue life of GH3039 superalloy, GH3039 superalloy sheets were treated by laser shock peening (LSP). The microstructure of GH3039 superalloy before and after LSP was characterized using an optical microscope, transmission electron microscope (TEM), and X-ray diffractometer. The fatigue life of the samples with and without LSP was investigated by fatigue experiments. Moreover, surface profile and residual stress were also examined. Experimental results indicated that the grains in the surface layer of the LSP sample were remarkably refined and reached the nanometer scale. The average surface roughness increased from 0.024 μm to 0.19 μm after LSP. The average fatigue life of the laser treated samples was 2.01 times larger than that of the untreated specimens. Additionally, mathematical statistical analysis confirms that LSP has a significant influence on the fatigue life of GH3039 superalloy. The improvement of fatigue life for the laser processed GH3039 superalloy was mainly attributed to compressive residual stress and grain refinement generated by LSP.

scholarly journals Effect of Laser Shock Peening on Fretting Fatigue Life of TC11 Titanium Alloy

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4711
Author(s):  
Xufeng Yang ◽  
Hongjian Zhang ◽  
Haitao Cui ◽  
Changlong Wen
Keyword(s):  
Titanium Alloy ◽  
Fatigue Life ◽  
Power Density ◽  
Laser Power ◽  
Fretting Fatigue ◽  
Laser Power Density ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Shock Peening ◽  
Tc11 Titanium Alloy

The purpose of this paper is to investigate the performance of laser shock peening (LSP) subjected to fretting fatigue with TC11 titanium alloy specimens and pads. Three laser power densities (3.2 GW/cm2, 4.8 GW/cm2 and 6.4 GW/cm2) of LSP were chosen and tested using manufactured fretting fatigue apparatus. The experimental results show that the LSP surface treatment significantly improves the fretting fatigue lives of the fretting specimens, and the fretting fatigue life increases most when the laser power density is 4.8 GW/cm2. It is also found that with the increase of the laser power density, the fatigue crack initiation location tends to move from the surface to the interior of the specimen.

Mechanical Behavior and Fatigue Performance of Carburized Steel Specimens

2016 ◽  
Vol 853 ◽  
pp. 72-76
Author(s):  
Ke Ji Pang ◽  
Huang Yuan
Keyword(s):  
Mechanical Property ◽  
Fatigue Life ◽  
Fracture Strain ◽  
Base Material ◽  
Fatigue Performance ◽  
Mechanical Parts ◽  
Carburized Steel ◽  
Carburized Layer ◽  
Compressive Residual Stresses ◽  
Improve Fatigue

Carburization is popular in design and fabrication of mechanical parts, such as gears, to improve fatigue performance. However, it is still open how to characterize the mechanical property of carburized steel and to quantify effects of the carburization to fatigue life of carburized parts. In the present paper four types of specimens differently treated and carburized are experimentally investigated. The experiments confirm significant increments in hardness and yield stress due to carburization. The fracture strain of the carburized steel is significantly smaller than that of the base material. Although the fatigue performance of the carburized steel is slightly worse than the base material, the solid carburized specimen shows significantly longer fatigue life. The fatigue limit increases from ca. 300 MPa for the base material to 550 MPa for the tensile carburized specimens. Detailed measurements display that the carburized layer in a carburized specimen possesses high compressive residual stresses, which arises the fatigue performance of the carburized steel.

Experimental Study on Improving High-Cycle Fatigue Performance of TC11 Titanium alloy by Laser Shock Peening

2013 ◽  
Vol 40 (8) ◽  
pp. 0803006 ◽  
Author(s):  
聂祥樊 Nie Xiangfan ◽  
何卫锋 He Weifeng ◽  
臧顺来 Zang Shunlai ◽  
王学德 Wang Xuede ◽  
李玉琴 Li Yuqin
Keyword(s):  
Experimental Study ◽  
Titanium Alloy ◽  
High Cycle Fatigue ◽  
Laser Shock Peening ◽  
Fatigue Performance ◽  
Cycle Fatigue ◽  
Laser Shock ◽  
Shock Peening ◽  
Tc11 Titanium Alloy

The Relationship Between Design, Processing and Shot Peening on Wheel Plate Failures

2014 ◽  
Author(s):  
Steven L. Dedmon
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
Cold Rolling ◽  
Shot Peening ◽  
Cyclic Stresses ◽  
Compressive Stresses ◽  
Freight Car ◽  
The Relationship ◽  
Fatigue Failures ◽  
Improve Fatigue

Wheel plate failures occur rarely in North American freight car service. When they do occur, derailments are a likely result. Shot peening has been used to improve fatigue life for more than 80 years and the efficacy of the process is now undisputed in reducing fatigue failures of parts subjected to high levels of cyclic stresses. The introduction of residual compressive stresses from shot peening is acknowledged as the reason for the improvement in fatigue life; comparable processes such as cold rolling, are successful for the same reason. Since residual stresses are so important to fatigue life, then design and processing prior to shot peening should have an equally important role. This investigation demonstrates some of the variables which are important to producing wheels resistant to plate fatigue failures.

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