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A study of fatigue notch sensibility on titanium alloy TiAl6V4 parts manufactured by selective laser melting
摘要： Titanium Ti6Al4V alloy is a light alloy characterized by having excellent mechanical properties and corrosion resistance combined with low specific weight, commonly used in biomedical applications, automotive and aerospace components. Current work analyses the fatigue behavior of titanium alloy TiAl6V4 parts, manufactured by selective laser melting (SLM), intending to characterize fatigue strength from low to high life range, under constant amplitude strain control. Fatigue tests were carried out at room temperature, using round dog bone specimens where laser powder deposition occurred in layers perpendicular to the sample axle. All specimens were subjected to stress release treatment. A second batch of specimens was tested in order to investigate the notch sensibility of the material. All tests were performed under displacement control. The material was characterized in terms of the tensile mechanical properties, cycle curve, Basquin and Coffin equations. The analysis of the results showed a strain-softening behavior that increased with applied strain, and non-linear response in and plastic regime. In addition, this alloy exhibited a low transition life, about 250 reversals, which can be attributed to the combination of high strength and relatively low ductility. The material revealed a notch sensibility factor, that was quantified for the round notch with a stress concentration factor Kt=1.7 (with respect to the effective cross section), increasing with fatigue life, from one for low cycle fatigue tending to 1.42 for high cycle fatigue (Nf of about one million cycles). SEM analysis showed that fatigue crack initiated from the surface and propagated through the cross section, occurring in many cases multi-nucleation.
关键词： Notch sensibility,TiAl6V4 alloy,Additive manufacturing,Fatigue
更新于2025-09-12 10:27:22
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Fatigue Behaviour of Additively Manufactured Inconel 718 Produced by Selective Laser Melting.
摘要： Selective Laser Melted (SLM) Inconel 718 has promising use in various applications, where complex design and excellent strength is required. Yet fatigue properties of respective components in critical load bearing applications are yet poorly understood. Here, we investigate the fatigue behaviour of different notch geometries of as-build specimens at room temperature. The fatigue strength of semi-circular and v-shaped notch geometries are evaluated and the results compared with those of smooth specimens. The stress fields of the different geometries are analysed by use of analytical models and numerically by use of finite element. The fatigue data shows a smaller scatter in the geometries with printed overhangs than the ones without. High values of notch sensitivity is obtained for both notch geometries. Fatigue properties of AM Inconel 718 are so far underexplored, this research therefore adds to the applicability of this material and manufacturing method for load bearing applications.
关键词： Elastic Stress Fields,Additive Manufacturing,Fatigue,Notch,Inconel 718
更新于2025-09-12 10:27:22
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Fatigue crack growth behavior of laser-shock processed aluminum alloy 2024-T3
摘要： Laser shock processing (LSP) is a surface modification technique aimed at enhancing the resistance to wear, corrosion and fatigue of structural alloys. Recently, LSP without coating (LSPwC) has been gaining ground, using lasers with lower energies, shorter pulse duration, smaller laser spots and higher surface coverage per shot. In the present work, LSPwC treatment was performed in both sides of pre-cracked compact tension specimens of aluminum alloy 2024-T3. A pulsed (9 ns) Nd:YAG laser system operating in the second harmonic (532 nm) at 10 Hz repetition rate and with pulse energy of about 270 mJ was positioned with a 500 mm focal distance lens in order to conduct LSPwC with an estimated power density of 5.2 GW/cm2 and two distinct overlapping rates: 50% and 75%. The objective of the work was to investigate the effect of the LSPwC and cyclic load condition on the crack closure and fatigue crack growth (FCG) behavior shown by the samples. Constant amplitude FCG tests were performed with two distinct load ratios: R = 0.2 and R = 0.5. A small increase in the crack closure loads (Pcl ? 1.1-1.2 Pmin) and in the number of cycles to crack propagation was evinced for the specimens tested at R = 0.2 compared to the untreated ones, whereas negligible effect was observed in the R = 0.5 tests. Besides, the obtained results indicate that the increase in overlapping rate is not effective for the adopted LSPwC conditions.
关键词： Laser shock processing,Fatigue crack growth,Aluminum alloy 2024
更新于2025-09-12 10:27:22
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Optimization of Laser Shock Peening For Titanium
摘要： Present competitive world is looking for Components with high strength and fatigue resistance finding their applications in aerospace, turbine parts and especially bio-medical devices with high bio-compatibility. Advanced engineering techniques are required to produce parts of higher complexities and desirable surface qualities. Laser peening stood first in a row of all various surface treatments of metallic component. A Fundamental purpose of nobility of the nearby variations in residual stress that happen inside the processed region, that are sensitive to processing variables and not effectively measured tentatively. The rule of residual .stress .is important .in guaranteeing .the nobility of engineering segments and Laser. Shock. Peening (LSP) process .can be utilized to great impact to present the gainful compressive residual . stress .levels as required. It is, nonetheless, hard to utilize ordinary laser . peening .rule .frameworks to set up the perfect peening .state that . will bring about the best .execution. This .paper.. results .from .a study .to optimize the .laser .peening .parameters . for a typical . titanium.. ND- YAG laser equipment was taken for the experimental work and statistical Taguchi technique was .used .to bound .the number .of experiments .necessary .for optimization .to be feasible.
关键词： Fatigue life,Taguchi Technique,Biomedical applications,Laser peening
更新于2025-09-12 10:27:22
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[IEEE 2019 3rd International Conference on Circuits, System and Simulation (ICCSS) - Nanjing, China (2019.6.13-2019.6.15)] 2019 3rd International Conference on Circuits, System and Simulation (ICCSS) - Long-Term Effect of Visual Fatigue Caused by LEDs with Modulated Light
摘要： The visual fatigue caused by long-term work under steady light generated by fluorescent luminaires and fluctuated light generated by LED luminaires with different modulation depth was investigated through subjective reports of symptoms and physiological signals. Both the subjective feelings and the physiological results show that visual fatigue becomes more serious with increasing time under all the test lighting conditions. Compared to fluorescent luminaires, the LED luminaires with full-modulated light produced significantly severer symptoms. However, the LEDs with 75% modulation depth was fully accepted.
关键词： physiological signal,LEDs,visual fatigue,modulation depth,subjective symptom
更新于2025-09-12 10:27:22
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Improvement of the Fatigue Life of Stainless Steel Specimens by Laser Shock Processing
摘要： An investigation concerning the influence of laser shock processing (LSP) of stainless steel specimens made of 03Kh22N6M2 steel for the fatigue life by finite element modeling was performed. The known experimental fatigue life parameters were compared with the data taken from the finite element modeling. A conforming comparison is observed between the numerical and experimental data. It was shown that the thickness of the specimen is an important parameter during application of the LSP technology. It was found that with the decrease in the specimen thickness the fatigue life, conditioned by the LSP application, improves significantly. It was shown that for thin specimens (about 2 mm) the application of the LSP technology improves the fatigue life to 300%.
关键词： residual stresses,finite element modeling,fatigue life,laser-shock-wave processing
更新于2025-09-11 14:15:04
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In situ tailoring microstructure in laser solid formed titanium alloy for superior fatigue crack growth resistance
摘要： For damage tolerance (DT) titanium alloy, the fatigue crack growth resistance (FCGR) is a critical properties requirement for engineering applications. However, the Ti-6Al-4V-DT parts fabricated by laser solid forming (LSF) suffer from low FCGR, because of predominant basket-wave microstructure. Here, we have explored a novel LSF fabrication design to produce full colony microstructure, via in-situ controlled growth. The creation of such microstructures leads to superior FCGR, which markedly exceed conventional additive manufactured and mill-annealed samples. The present works provide a significant guidance for LSF-fabricated titanium alloy with high DT properties.
关键词： Titanium alloy,Fatigue crack growth resistance,Laser solid forming,Colony microstructure
更新于2025-09-11 14:15:04
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Effect of Different Forms of Application of a Laser Surface Treatment on Fatigue Crack Growth of an AA6013-T4 Aluminum Alloy
摘要： This work analyzes the effect of surface-localized laser heating treatment on the fatigue crack growth (FCG) rate on region II of the sigmoidal da/dN 3 DK curve of an aerospace-grade AA6013-T4 aluminum alloy sheet with 1.3 mm thickness. The in?uence on microstructure changes is also evaluated. Aiming to improve the FCG resistance without changing the mechanical behavior of the alloy, a Yb:?ber laser beam is defocused to generate a laser spot diameter of 2 mm, using 200 W power and a laser speed of 2 mm/s. Two laser lines are applied over fatigue C(T) specimens in two different forms: on only one and on both lateral specimen surfaces. Guinier–Preston zones, dispersoids and coarse constituent particles are found on the base material. On the heat-treated material, the same precipitates and also b￠ and Q￠ precipitates are found. These microstructural variations due to the laser thermal cycle, together with the presence of induced compressive residual stresses, improved the fatigue behavior of the material. The FCG retardation is optimized when two laser lines were applied on both lateral surfaces of the specimen.
关键词： aluminum alloy,microstructure,fatigue crack growth,residual stresses,laser surface treatment
更新于2025-09-11 14:15:04
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Effect of Surface and Subsurface Defects on Fatigue Behavior of AlSi10Mg Alloy Processed by Laser Powder Bed Fusion (L-PBF)
摘要： The fatigue behaviour of an AlSi10Mg alloy processed by laser powder bed fusion (L-PBF) and subjected to different surface finishing processes was investigated paying special attention to the residual defects on the surface and the dominant fatigue failure mechanisms. Roughness measurements and qualitative surface morphology analysis showed smooth surfaces in the case of vibro-finishing and machining followed by polishing. The fatigue performance did not reveal to be directly related to surface roughness, but residual intrusions left on the finished surfaces. Post-mortem analysis showed single- or multiple-crack nucleation from pores opened on the surface, un-melted powders, or spatters considered as typical L-PBF defects. A fatigue limit of 195 MPa for machined and polished samples was obtained by substantial removal of surface and subsurface defects.
关键词： surface texture,laser powder bed fusion,AlSi10Mg alloy,surface finishing,fatigue strength
更新于2025-09-11 14:15:04
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Stresses and fatigue of laser welds
摘要： The paper deals with the specific properties of laser welds in fine-grained high-strength steels. The main topic, however, are residual stresses in laser welds, their impact on the mechanical properties and fatigue behaviour of such welds. As documented, fatigue cracks initiate mainly on micropores or other subsurface defects. From X-ray diffraction studies it follows that thermal expansion is primarily responsible for the longitudinal tensile stresses, whereas transverse compressive stresses are caused by phase transformations. The behaviour of transverse stresses also explains why fractures in laser welds occur completely outside the weld metal and the heat-affected zone.
关键词： welding,laser,residual stress,fatigue
更新于2025-09-11 14:15:04