Papers by Keyword: TRIP

Abstract: With the improvement of people's living standards, a wide variety of home appliances gradually into the ordinary family. In these appliances, there are many various nonlinear loads, nonlinear loads generated in the process of using a large number of high harmonics, and sold on the market are mostly air switch 50Hz power under conditions of use in accordance with the design, which kinds of air switch is suitable for applications in which high harmonic supply. This article will explore this issue through theoretical research and testing methods.

Abstract: In recent years, Quenching and Partitioning (Q&P) became an interesting thermal process route for semi-finished high strength low alloyed steel components. Recent publications demonstrate promising mechanical properties with considerable ductility enhancement. To assess the potential of the two-step Q&P heat treatment in seamless tube production, corresponding tests are carried out on 42SiCrB steel (0.42wt% C, 2.0wt% Si, 1.3wt.% Cr, 0.6wt.% Mn, 0.002wt.% B). Feasible Q&P heat treatment process parameters are identified using the Constrained-Carbon-Equilibrium (CCE) model, carbon diffusion calculations and isothermal TTT curves with previous quenching. Furthermore achieved volume fraction of retained austenite is analyzed by XRD experiments.

Abstract: The present work evaluates hydrogen induced cracking in a high strength TRIP steel with a complex multiphase microstructure, containing ferrite, bainite, retained austenite, and some martensite. Each structural constituent demonstrates a different behavior in the presence of hydrogen and when deformed, the retained austenite transforms to martensite. The goal of this work is to understand the response of the hydrogen saturated multiphase structure to a mechanical load. A tensile test on notched samples combined with in-situ electrochemical hydrogen charging was carried out. The test was interrupted at certain specific points, before the macroscopic failure of the material. Hydrogen induced crack initiation and propagation were examined by studying several intermediate elongations. The microstructure of the samples was characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The EBSD measurements allowed both microstructural and crystallographic characterization of the hydrogen induced crack surroundings. A correlation was found between the occurrence of martensite, which is known to be very susceptible to hydrogen embrittlement, and the initiation of hydrogen induced cracks. These cracks were located at the surface in specific high stressed regions. Finite element simulations indicated that these regions were induced due to the presence of the notch.

Abstract: Mounting energy crisis, stringent emission law and strict safety rules have guided car manufacturers to improve strength/weight ratio of the vehicle, thereby promoting several applications of stainless steels in the car body. Moreover, use of stainless steels also improves aesthetics and minimizes life cycle cost. In automobiles, presently 45-50% of stainless steels are used in exhaust systems. To improve efficiency, complex designs are being used and performance criteria of the material are getting tougher. New techniques such as tube hydroforming are also being explored using austenitic stainless steel for the complicated designs utilizing the benefits of high ductility of these grades. Since corrosion resistance remains fundamental requirement for these applications, selection of grades and stabilizing elements are critical for such applications and depend primarily on operating conditions. Different grades and effect of their composition on elevated temperature strength, creep strength, endurance limit and corrosion resistance are presented. Stainless steels are also being used in other applications such as fuel tank, bumper, chassis for buses and trucks. With the development of new varieties of austenitic, ferritic and martensitic stainless steels, automotive industry is intensively exploring their potential.

Abstract: The effect of heat input on the transformation of retained austenite steels transformation induced plasticity (TRIP) was investigated in the heat affected zone (HAZ) of the Gas Metal Arc Welding GMAW process. The determination of retained austenite of the HAZ is important in optimizing the welding parameters when welding TRIP steels, because this will greatly influence the mechanical properties of the welding joint due to the transformation of residual austenite into martensite due to work hardening. Coupons were welded with high and low heat input for investigating the austenite transformation of the base metal due to heat applied by the welding process and was evaluated by optical microscopy and the method of X-Ray Diffraction (XRD). Data analyzed shows that the volume fraction of retained austenite in the HAZ increases with the heat input applied by the welding process, being greater as the heat input increase and decrease the cooling rate, this due to variation in the travel speed of the weld path.

Abstract: Adiabatic shear bands (ASBs) develop generally during high strain rates. This paper investigates the transformation induced plasticity (TRIP) effect during ASBs formation at high strain rates in high manganese TRIP steels containing initial austenite and ferrite by EBSD technique. Results show that TRIP effect takes place mainly before the formation of ASBs. After ASBs formation, TRIP effect is strongly restricted by the size effect, the increase of stacking fault energy (SFE) and even inverse martensitic transformation due to the rise of temperature. The TRIP effect before ASBs formation contributes to the resistance of adiabatic shear failure. Dynamic recrystallization driven by subgrains rotation occurs within ASBs, and ultrafine grains often show strong shear textures with twin relationship owing to slip mechanism.

Abstract: After an analysis on the shielding failure trip of accidents of two kinds of tower type for JG and ZGUT in 220kA transmission line in Jiujiang,the main causes of shielding failure trip on the JG and ZGUT type tower which the protection angle of middle phase jumper of JG type tower and middle phase wire of ZGUT type tower are too large were summarized.The measures to prevent the JG and ZGUT type tower from shielding failure were proposed in which TH-lightning rod above cross arm of suspension point of the Jumper string of JG ype tower and the middle phase conductor of ZGUT type tower were reasonably installed.The measures prove to be an effective way.

Abstract: Four continuous annealing cycles were adopted to get four kinds of multi-phase steels using 0.2C-1.5Si-1.8Mn [wt%] alloyed raw steel and the microstructures and mechanical properties were investigated. The results show that traditional ferrite-martensite dual phase steel has a tensile strength of more than 1000MPa, but has the lowest strength-plastic product of only 18GPa%. The traditional ferrite, bainite and residual austenite TRIP steel has the highest elongation of 31% and hardening exponent of 0.24, but its tensile strength is just over 800MPa. Introducing hard matrix such as acicular bainitc ferrite or martensite to replace the polygonal ferrite matrix, meanwhile introducing metastable austenite, is conducive to obtain high strength and good ductility. Those kinds of modified TRIP steel with hard matrix can reach above 20GPa% of the strength-plastic product on the 1000MPa grade.

Abstract: TRIP steels, or Transformed Induced Plasticity steels, have excellent mechanical properties if compared with conventional steels. The highlighted characteristic of these steels is that they modify the microstructure with the deformation process as part of the austenite transforms to martensite, with the consequent change of the material properties. One of the main problems of TRIP steels is strong elastic recovery, or springback, after forming. In this work, the springback phenomenon is evaluated by bending tests and the influence of the variables involved in it is determined. Experimental bending forces do not agree with theoretical predictions that are proposed in the literature. In spite of the bending radius having been considered an influence factor in the process, this work demonstrates that the aforementioned factor has a minor influence, at least for TRIP 800. The factor found to affect material recovery the most was the bending angle.

Abstract: The calculation of fluctuating pressure is necessary during the progress of trip in the managed pressure drilling, because the bottomhole pressure should be constant during the progress of trip. The prediction model of the fluctuating pressure during the progress of trip was established based on the unsteady flowing theory. The actual application state of the prediction model was presented through a computational example. By the comparison between the computational result and the field test result, the computational result matches the field test result very well, which indicates the rationality and the accuracy of the model.