- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Effect of laser shock peening on high cycle fatigue characteristics of 316LN stainless steel
摘要： The influence of ‘laser shock peening’ (LSP) on fatigue behavior of 316LN stainless steel has been studied at 298 K by conducting fully reversed stress controlled fatigue tests in the range 200–300 MPa. A triangular wave form with a constant frequency of 5 Hz was employed for all the tests conducted below 107 cycles on the virgin and laser shock peened samples. The run out tests at 107 cycles were performed at a frequency of 60 Hz. The studies have clearly revealed that the fatigue life is dependent on surface condition of the material and stress amplitude employed. A comparison is made of cyclic stress-strain hysteresis loops and fatigue lives between virgin and peened material. The peened material showed better fatigue strength and life at low stress amplitudes pertaining to high cycle fatigue regime, and exhibited lower density of surface microcracks. The improved fatigue resistance of peened material is attributed to the presence of residual compressive stresses to a depth of ~100 μm from the surface. The beneficial effect of compressive stresses is perceived both in the reduction in number density of Stage-I microcracks and retarded stage-II crack growth in the initial stages (that revealed striations with lesser spacing compared to un-peened samples).
关键词： Laser shock peening,Stainless steel,High cycle fatigue,Compressive residual stresses
更新于2025-09-19 17:13:59
-
Comparison between Shot Peening, Cavitation Peening, and Laser Peening by Observation of Crack Initiation and Crack Growth in Stainless Steel
摘要： The traditional technique used to modify the surface of a metallic material is shot peening; however, cavitation peening, a more recent technique in which shot is not used, was developed, and improvements in the fatigue strength of metallic materials were demonstrated. In order to compare the fatigue properties introduced by shot peening with those introduced by cavitation peening, crack initiation and crack growth in specimens of austenitic stainless steel (Japanese Industrial Standards JIS SUS316L) treated using these techniques were investigated. With conventional cavitation peening, cavitation is produced by injecting a high speed water jet into water. In the case of submerged laser peening, bubbles are generated using a pulsed laser after laser ablation, and the impact produced when the bubbles collapse is larger than that due to laser ablation. Thus, in this study, cavitation peening using a water jet and submerged laser peening were investigated. To clarify the mechanisms whereby the fatigue strength is improved by these peening techniques, crack initiation and crack growth in specimens with and without treatment were examined by means of a K-decreasing test, where K is the stress intensity factor, and using a constant applied stress test using a load controlled plane bending fatigue tester. It was found that the improvement in crack initiation and the reduction in crack growth were roughly in a linear relationship, even though the specimens were treated using di?erent peening methods. The results presented here show that the fatigue strength of SUS316L treated by these peening techniques is closely related to the reduction in crack growth, rather than crack initiation.
关键词： crack,stainless steel,fatigue,shot peening,cavitation peening
更新于2025-09-19 17:13:59
-
[IEEE IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society - Lisbon, Portugal (2019.10.14-2019.10.17)] IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society - Techno-Economic Analysis of Building Integrated Photovoltaics Electrical Installations
摘要： Insulated-gate bipolar transistor (IGBT) power modules find widespread use in numerous power conversion applications where their reliability is of significant concern. Standard IGBT modules are fabricated for general-purpose applications while little has been designed for bespoke applications. However, conventional design of IGBTs can be improved by the multiobjective optimization technique. This paper proposes a novel design method to consider die-attachment solder failures induced by short power cycling and baseplate solder fatigue induced by the thermal cycling which are among major failure mechanisms of IGBTs. Thermal resistance is calculated analytically and the plastic work design is obtained with a high-fidelity finite-element model, which has been validated experimentally. The objective of minimizing the plastic work and constrain functions is formulated by the surrogate model. The nondominated sorting genetic algorithm-II is used to search for the Pareto-optimal solutions and the best design. The result of this combination generates an effective approach to optimize the physical structure of power electronic modules, taking account of historical environmental and operational conditions in the field.
关键词： power cycling (PC),Aging,fatigue,insulated-gate bipolar transistors (IGBTs),thermal cycling (TC),multiobjective,optimization methods,reliability,finite-element (FE) methods
更新于2025-09-19 17:13:59
-
[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - a-Si:H/c-Si interface hydrogenation for implied V <sub/>oc</sub> = 755 mV in Silicon heterojunction solar cell
摘要： Insulated-gate bipolar transistor (IGBT) power modules find widespread use in numerous power conversion applications where their reliability is of significant concern. Standard IGBT modules are fabricated for general-purpose applications while little has been designed for bespoke applications. However, conventional design of IGBTs can be improved by the multiobjective optimization technique. This paper proposes a novel design method to consider die-attachment solder failures induced by short power cycling and baseplate solder fatigue induced by the thermal cycling which are among major failure mechanisms of IGBTs. Thermal resistance is calculated analytically and the plastic work design is obtained with a high-fidelity finite-element model, which has been validated experimentally. The objective of minimizing the plastic work and constrain functions is formulated by the surrogate model. The nondominated sorting genetic algorithm-II is used to search for the Pareto-optimal solutions and the best design. The result of this combination generates an effective approach to optimize the physical structure of power electronic modules, taking account of historical environmental and operational conditions in the field.
关键词： fatigue,power cycling (PC),insulated-gate bipolar transistors (IGBTs),thermal cycling (TC),reliability,optimization methods,finite-element (FE) methods,Aging,multiobjective
更新于2025-09-19 17:13:59
-
Research on Post-processing Microstructure and Property of Titanium Components with Selective Laser Melting (SLM)
摘要： Additive manufacturing of titanium component holds promise to deliver benefit such as reduced cost, weight and carbon emissions during both manufacture and use. To capitalize on the benefits, it must be shown that the mechanical performance of parts produced by additive manufacturing can meet design requirement that are typically based on wrought material performance properties. Of particular concern for safety critical structures is the fatigue property of parts produced by additive manufacturing. Microstructure evolution, and its influence on mechanical properties of the alloy in the as-fabricated condition, has been documented by various researchers. However, fatigue crack propagation and the effects of the directional structure have not been sufficiently studied, imposing a barrier for this technology’s potential extension to high-integrity applications. In this study, fatigue life (S-N) and fatigue crack growth (FCG) both parallel and perpendicular to the build directions was studied. The interaction between the directional as-fabricated SLM microstructure and FCG was investigated and compared to that of the hot isostatic pressing (HIP) specimens with and without the stress relief after fabricating with SLM.
关键词： Titanium Components,Selective Laser Melting (SLM),Hot Isostatic Pressing (HIP),Fatigue Property,Microstructure
更新于2025-09-19 17:13:59
-
A new approach to correlate the defect population with the fatigue life of selective laser melted Ti-6Al-4V alloy
摘要： Microstructural features and defects arising from selective laser melting (SLM) determine the in-service performance of additively manufactured near-net-shape components. Here the grain type, shape, size and distribution were characterized using electron backscattered diffraction (EBSD). High-resolution synchrotron radiation X-ray computed tomography was used to quantify the population, morphology and dimensions of porosity and lack of fusion defects. For SLM Ti-6Al-4V alloy, the larger-sized defects in comparison with α′ grains are more important for crack initiation, typically leading to poor fatigue resistance and a pronounced variation in fatigue life. The fatigue strength was then evaluated in terms of the defect population using a combination of the statistics of extremes and the Murakami model. Finally, an extended Kitagawa-Takahashi fatigue diagram was established within the framework of defect-tolerant design, which includes a classical safe-life region and the defect-determined lifetime in the finite life region.
关键词： Defect tolerance assessment,Chapetti model,Fatigue crack initiation and propagation,Kitagawa-Takahashi diagram,Additive manufacturing
更新于2025-09-19 17:13:59
-
Predicting the fatigue life of an AlSi10Mg alloy manufactured via selective laser melting by using data from Computed Tomography
摘要： A modelling strategy is proposed to evaluate the influence of defect morphology on the fatigue limit of additively manufactured Al alloys by: (i) obtaining an x-ray micro-computed tomography (μ-CT) 3D image of the material, (ii) computing the Equivalent Inertia Ellipse of each individual pore, (iii) modelling the influence of the defect on the fatigue limit through the DSG approach and, (iv) 3D mapping the criticality of each individual defect. For this fatigue study, an AlSi10Mg alloy was manufactured by selective laser melting using sub-optimal deposition parameters in order to produce large lack-of-fusion defects. After a T6 heat treatment, tension-compression fatigue tests, with R = -1, were conducted on specimens oriented with their loading axis either parallel or normal to the Z-axis of the additive manufacturing equipment. Two samples were characterised before μ-CT testing in order to characterise the initial 3D defect population. Each sample was fatigued step by step in order to determine the fatigue limit. The fracture surface was then carefully observed using a scanning electron microscope (SEM) in order to identify the critical defect in the initial μ-CT image. A comparison with the fatigue results led to the following conclusions: (i) when the longest axis of the defect is perpendicular to the load axis, modelling the defect as an equivalent inertia prolate ellipse gives better results (5 % error on the fatigue limit) than modelling it as a simple equivalent sphere (22 % error on the fatigue limit), (ii) the prolate ellipse is not relevant when the longest axis of the defect is oriented along the loading axis; in this case an oblate equivalent ellipse should be used, (iii) the concept of ‘size’ for a complex 3D shaped defect should be linked to the inertia and the loading, (iv) with this approach, surface defects are shown to be more critical than internal ones for fatigue life and, (v) a 3D defect criticality map of the entire sample can be plotted to provide visual feedback on which defects are the most critical for fatigue life.
关键词： AlSi10Mg alloy,defect morphology,selective laser melting,fatigue life,Computed Tomography
更新于2025-09-19 17:13:59
-
Fatigue Life Behavior of Laser Shock Peened Duplex Stainless Steel with Different Samples Geometry
摘要： Two different stress raiser geometries (fillet and notched) were treated by laser shock peening (LSP) in order to analyze the effect of sample geometry on fatigue behavior of 2205 duplex stainless steel (DSS). The LSP treatment was carried through Nd:YAG pulsed laser with 1064 nm wavelength, 10 Hz frequency, and 0.85 J/pulse. Experimental and MEF simulation results of residual stress distribution after LSP were assessed by hole drilling method and ABAQUS/EXPLICIT software, respectively. The fatigue tests (tensile-tensile axial stress) were realized with stress ratio of R = 0.1 and 20 Hz. A good comparison of residual stress simulation and experimental data was observed. The results reveal that the fatigue life is increased by LSP treatment in the notched samples, while it decreases in the fillet samples. This is related to the residual stress distribution after LSP that is generated in each geometry type. In addition, the fatigue crack growth direction is changed according to geometry type. Both the propagation direction of fatigue crack and the anisotropy of this steel results detrimental in fillet samples, decreasing the number of cycles to the fatigue crack initiation. It is demonstrated that the LSP effect on fatigue performance is influenced by the specimen geometry.
关键词： laser shock peening,residual stress,duplex stainless steel,fatigue life,sample geometry
更新于2025-09-19 17:13:59
-
Microstructure and fatigue behavior of a laser additive manufactured 12CrNi2 low alloy steel
摘要： In this research, 12CrNi2 low alloy steel was successfully prepared by laser melting deposition (LMD). The mechanisms driving high cycle fatigue fracture of the as-built LMD 12CrNi2 low alloy steel were investigated and a concurrent process-microstructure-property relationship was established through microstructural analysis. The results showed that the crystal structures of the as-built LMD 12CrNi2 steel mainly consisted of the ferrite and a small amount of Cr23C6 carbides. No preferred texture was observed as a result of the complicated heat flux direction during fabrication. Based on the examination of the fracture surface, fatigue cracks of the as-built LMD 12CrNi2 steel initiated from subsurface defects for all the cases. Crack propagation zones showed a mixed mode of transgranular and intergranular fracture in a brittle manner, whereas the final fracture zones displayed dimples typical of ductile fracture. The kernel average misorientation (KAM) map indicated that the strain localization predominantly occurred at the grain boundaries and slightly appeared at the interior of the ferrite grains. Schmid factor distribution results implied that fatigue cracks originated from grains with {123}<111> slip system due to the prior activation of {123}<111> slip system.
关键词： Fractography,High cycle fatigue,Microstructure,12CrNi2 low alloy steel,Laser additive manufacturing
更新于2025-09-16 10:30:52
-
[IEEE 2019 IEEE 4th Optoelectronics Global Conference (OGC) - Shenzhen, China (2019.9.3-2019.9.6)] 2019 IEEE 4th Optoelectronics Global Conference (OGC) - Effect of Deposition Strategy on Fatigue Behavior of Laser Melting Deposition 12CrNi2 Alloy Steel
摘要： In this paper, the 12CrNi2 alloy steel parts were fabricated by laser melting deposition (LMD) using two kinds of deposition strategies, single direction scanning(SDS) and cross direction scanning(CDS). The microstructure and fatigue behavior of LMD 12CrNi2 alloy steel samples were investigated. Thy typical microstructure of both deposition strategy were ferrite and can be divided into two zones: remelted zone and non-remelted zone. The non-remelted zone showed typical columnar crystal morphology while the structure of remelted zone was homogenized. Compared with SDS deposition strategy, the microstructure of CDS deposition strategy had shorter columnar grains and finer grains. The relative densities of SDS and CDS deposition strategies were 98.1 and 97.3, respectively, indicating that SDS had lower porosity. The fatigue strength of SDS deposition strategy was higher than that of CDS deposition strategy, which were 320 MPa and 200 MPa. There were more defects in CDS deposition strategy, which accelerated the initiation and propagation of cracks. CDS deposition strategy had longer interlayer interval time, which will reduce the penetration depth of laser, affect the degree of previous layer remelting, and eventually lead to unmelted powder, porosity and other defects in the lap zone.
关键词： laser melting deposition,deposition strategy,fatigue,12CrNi2
更新于2025-09-16 10:30:52