Experimental Analysis on the Fatigue Threshold Behaviour of a Nitrided and Shot Peened Steel

2007 ◽  
Vol 348-349 ◽  
pp. 865-868 ◽  
Author(s):  
Mario Guagliano
Keyword(s):  
Shot Peening ◽  
High Performance ◽  
Fatigue Threshold ◽  
Threshold Values ◽  
Micro Hardness ◽  
Threshold Behaviour ◽  
Intensity Factors ◽  
Micro Hole ◽  
Mechanical Performances ◽  
Mechanics Concepts

The effectiveness of the application of shot peening after nitirding for improving the fatigue strength of high-performance steel components has not been adequately treated in literature, and it is not clear if shot peening can really and drastically increase mechanical performances of nitirded elements. In this paper an approach to assess the influence of shot peening on nitrided components is presented. It is based on fracture mechanics concepts. Smooth specimens with a micro-hole acting as a pre-crack were fatigue tested. The values of micro-hardness and of the residual stresses were measured and related to the experimental results. By elaborating the results it was possible to determine the threshold values of the stress intensity factors of the nitrided and shot peened material. A formula to predict the value of Kth of shot peened and nitrided steels is proposed.

Bio-Crude by Acidic Phenolation and Carbamation for the Preparation of Phenolic Thermosetting Resin and Its Application in Thermoresistant Laminates

2019 ◽  
Vol 17 (4) ◽  
Author(s):  
Huan Wang ◽  
Zhuo Wang ◽  
Penggang Ren ◽  
Mingcun Wang
Keyword(s):  
High Performance ◽  
Phenolic Resin ◽  
Mechanical Test ◽  
Chemical Reactivity ◽  
Cost Effective ◽  
Mechanical Analysis ◽  
Thermosetting Resin ◽  
Scanning Calorimetry ◽  
Three Point Bending ◽  
Mechanical Performances

Abstract Fir sawdust was liquefied in phenol solvent under acidic catalyst at 135, 150 and 165 °C, respectively; after neutralization, bio-crude was obtained where contained oil-like liquid and tiny powder-like residue. The bio-crude was chemically modified with urea at high temperature (e. g. > 130 °C) to form carbamate so as to improve chemical reactivity of bio-crude in phenolic resin synthesis. The carbamate-containing bio-crude was condensed with paraformaldehyde into thermosetting phenolic resin. Finally, this biomass-derived phenolic resin matrixed silica fabric laminates were processed. The uncured and thermally cured bio-based resins were characterized by the techniques of Differential Scanning Calorimetry (DSC), Fourier Transform Infrared spectrum (FT-IR), rheology and Thermogravimetric Analysis (TGA), and the laminates’ structure and mechanical performances were studied using the methods of Scanning Electron Microscopy (SEM), three point bending mechanical test and Dynamic Mechanical Analysis (DMA). The results showed: (1) the chemical reactivity of bio-crude was highly improved by carbamation; (2) biomass-derived thermosetting phenolic resin was thermally curable at 150–250 °C (with two exothermic peaks at 185 °C and 220 °C); (3) the char yield was about 47 %, which was not in apparent relationship with sawdust liquefaction temperatures; (4) flexural strength of silica fabric laminates at room temperature was around 357 MPa (similar with that of conventional phenolic laminate); (5) glass transition temperature of silica fabric laminate was above 270 °C (much higher than Tg of conventional phenolic resin laminate, which is normally at 215 °C). The biomass-derived phenolic resin is expected to be widely used as cost-effective and environment-friendly thermosetting resin in the application of high-performance composites.

Microstructure-Aided Analysis of Fatigue Thresholds in Duplex Stainless Steel

2007 ◽  
Vol 567-568 ◽  
pp. 101-104 ◽  
Author(s):  
Jaroslav Pokluda ◽  
Tomáš Podrábský ◽  
Karel Slámečka ◽  
Simona Hutařová ◽  
Guo Cai Chai
Keyword(s):  
Fatigue Cracks ◽  
Fatigue Threshold ◽  
Threshold Region ◽  
Threshold Values ◽  
Duplex Microstructure ◽  
Martensitic Steels ◽  
High Fatigue ◽  
Crack Paths ◽  
Plasticity Induced Crack Closure ◽  
Good Agreement

High fatigue threshold values of duplex ferritic-martensitic steels are interpreted by using a unified model of roughness- and plasticity induced crack closure. Complex metallographical and fractographical analysis was performed in order to obtain characteristics of tortuous crack paths produced by crack deflection and branching mainly at austenite/ferrite interfaces. Calculated values of effective thresholds are in a good agreement with experimental data. The total level of extrinsic toughening (closure + shielding) induced by the duplex microstructure was determined to be as much as 70% of measured fatigue threshold values. This is the main reason for the high resistance to propagation of long fatigue cracks in the near-threshold region.

scholarly journals Silica Modified by Using Alcohol Polyoxyethylene Ether and Silane Coupling Agent together to Achieve High Performance Rubber Composites Using Latex Compounding Method

2017 ◽  
Author(s):  
Junchi Zheng ◽  
Xin Ye ◽  
Dongli Han ◽  
Suhe Zhao ◽  
Xiaohui Wu ◽  
...  
Keyword(s):  
High Performance ◽  
Silica Surface ◽  
Thermal Gravimetric ◽  
Rubber Composites ◽  
Polyoxyethylene Ether ◽  
Thermal Gravimetric Analyzer ◽  
Silane Coupling ◽  
Mechanical Performances ◽  
Physical And Chemical ◽  
Latex Compounding

Nowadays, the study of preparing silica/rubber composites, which can be used in “green tire”, in energy saving method is fast-growing. In our work, silica modified by using alcohol polyoxyethylene ether (AEO) and 3-Mercaptopropyltriethoxysilane (K-MEPTS) together were investigated. Thermal gravimetric analyzer (TGA) result indicated that both AEO and K-MEPTS could be grafted on the silica surface. Raman spectroscopy confirmed that the AEO could generate a certain steric hindrance for the mercaptopropyl group on K-MEPTS. Silica modified by using AEO and K-MEPTS together can be completely co-coagulated with the rubber in preparing silica/natural rubber (NR) composites by latex compounding method. AEO can form a physical interface between silica and rubber; meanwhile, K-MEPTS can form a chemical interface between silica and rubber. The effects of chemical and physical interface between silica and rubber on dynamic and mechanical performances of silica/NR composites were also given in this research. A proper combination of physical and chemical interface between silica and NR can improve performances of silica/NR composites.

scholarly journals Experimental Study on Ultrasonic Shot Peening Forming and Surface Properties of AALY12

2015 ◽  
Vol 1094 ◽  
pp. 339-342
Author(s):  
Chao Xun Liu ◽  
Shi Hong Lu ◽  
Wei Miao ◽  
Pan Feng Song ◽  
Tian Rui Wu
Keyword(s):  
Experimental Study ◽  
Surface Roughness ◽  
Electric Current ◽  
Shot Peening ◽  
Processing Time ◽  
Radius Of Curvature ◽  
Micro Hardness ◽  
Current Time ◽  
Ultrasonic Shot Peening ◽  
The Relationship

Ultrasonic shot peening (USP) on AALY12 sheet was studied. Several parameters (arc heights, surface roughness, surface topography and micro hardness) with different USP process parameters were measured. The research proposes that radius of curvature of shot peened sheet increases with time and electric current decreasing, while increases with pin diameter increasing, and radius of curvature reaches a saturation level after a specific processing time and electric current. An empirical model of the relationship between radius of curvature and pin diameter, electric current, time was also obtained. The research shows that the increment of surface and vertical micro hardness of material is more obvious with longer time and higher value of electric current, which can be up to 20% and 28% respectively.

Microstructures and Properties of Cu–AISI304 Parts Fabricated by Improved Selective Laser Sintering

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Z. L. Lu ◽  
J. H. Liu ◽  
Y. S. Shi
Keyword(s):  
High Performance ◽  
Selective Laser Sintering ◽  
Hot Isostatic Pressing ◽  
Processing Parameters ◽  
Laser Sintering ◽  
Cold Isostatic Pressing ◽  
Isostatic Pressing ◽  
Cu Content ◽  
Mechanical Performances ◽  
Liquid Sintering

For fabricating complex AISI304 parts with high performance by advanced powder/metallurgy technologies, cold isostatic pressing (CIP) is introduced into selective laser sintering (SLS) combined with hot isostatic pressing (HIP), which is abbreviated to selective laser sintering/isostatic pressed (SLS/IP). The effect of processing parameters on the densification of Cu–AISI304 parts is analyzed and then the influence of Cu on their relative densities, metallurgical structures, and mechanical performances are investigated. The results show that relative densities of Cu–AISI304 parts fabricated by SLS/IP are mainly influenced by CIP pressure and sintering temperature, and it is interesting to find that the formula 1−D=(1−D0)e−kP is testified by the CIP of SLS/IP. There is an antidensification phenomenon resulting from Cu and AISI304 in liquid sintering, but the relative densities of Cu–AISI304 parts can be gradually improved in HIP with Cu content increasing from 1 wt % to 3 wt %. After the above-mentioned Cu–AIS304 parts are finally hot isostatic pressed, their metallurgical structures consist of sosoloid (Cu,Ni) and (Fe,Ni) besides austenite (Fe,Cr,Ni,C), their best mechanical performances are close to those of solution treated compact AISI304 when Cu content is 3 wt %.

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