High strength,high elongation steels obtained by hot deformation and quenching and partitioning

Abstract

An effective means to achieve energy savings, environmental protection and improved safety in automobiles is to explore higher strength steels having low cost and better processability and service performance. Two routes to develop advanced high strength steels combining ultrahigh strength with appropriate plasticity and characterised by low cost and good quality are proposed: hot stamping followed by quenching and partitioning (HS-Q&P) and deformation induced ferrite transformation followed by Q&P (DIFT-Q&P).     

900 MW PWR containment mechanical behavior characteristics during containment test

Containment mechanical behavior characteristics are one of the important checking items during 900 MW PWR containment test. This article describes these characteristics (including strain, displacement and temperature influence) systematically. Especially some intrinsic characteristics are discussed and some new viewpoints are provided. We believe that it has some reference value to other containment test.     

Boundary characteristics in Heavily Deformed Metals

The potential of creating nanostructured metals by plastic deformation to very high strains is currently the subject of intensive research. An important part of this research concerns evolution of the characteristics of deformation induced boundaries, in particular boundary spacing and boundary misorientation. The aim of this paper is to give an overview of the present understanding of the relations between these characteristics, the microscopic deformation mechanisms and the macroscopic deformation mode.     

Modelling of the deformation behaviour of FGM by fuzzy-logic

A lot of processes for the manufacture of functionally gradient materials (FGM) have their limitations (simple geometry of components, gradient limited in one dimension). A further treatment by forming processes would extend the field of applications of FGM because it would make it possible to manufacture shaped pieces and to influence the properties of the material.

For this it is necessary to predetermine the deformation behaviour by mathematical models. Conventional equations have only limited applications because many other influences have to be considered.

Therefore a new model based on mathematical methods of fuzzy-logic has been developed which can describe the plasto-mechanical behaviour of FGM during the deformation process. The main advantages are:

• no necessity to represent the mathematical equation between in- and output variables by functions;

• adaptable algorithms;

• almost no restriction of the number of influencing variables;

• simple solution of multi-dimensional approximation problems.

Experiments to determine the deformation behaviour have been carried out on different material systems (Al–Cu, 316L–430L, Al–SiC) by using the hot upsetting test. First results show that this kind of modelling is suitable to describe the deformation behaviour very accurately.     

Free vibrations of laminated composite plates using second-order shear deformation theory

A complete set of linear equations of the second-order theory of laminated composite plates are obtained. A generalized Levy type solution in conjunction with the state space concept is used to analyze the free vibration behavior of cross-ply and antisymmetric angle-ply laminated plates. Exact fundamental frequencies of cross-ply plate strips are obtained for arbitrary boundary conditions. The exact analytical solutions are obtained for thick and moderately thick plates as well as for thin plates and plate strips. It is shown that the results of the second-order theory are very close to the results of the first-order and third-order theories reported in the literature, and different from those of the classical Kirchhoff’s theory for thick laminates.     

Numerical simulation of plastic deformation and fracture in polysynthetically twinned (PST) crystals of TiAl

Plastic deformation and fracture in polysynthetically twinned (PST) crystals of TiAl have been simulated by using periodic unit cells representing the relaxed-constraint model recently proposed by Lebensohn et al. [Acta Mater. 46 (1998) 4701–4709] for the co-deformation of the lamellar compound of PST-TiAl. The unit cells contain both intermetallic phases, ₂-(Ti₃Al) and γ-(TiAl). Furthermore, the six orientation variants of the γ-phase are also considered. The constitutive behaviour of both phases is described by crystal plasticity, and the damage behaviour has been implemented by means of cohesive elements. The unit cells have been used as submodels for multi-scale finite element simulations of compression tests and fracture mechanics tests of notched micro-bend specimens. It is shown that the anisotropy of plastic deformation and damage in PST-TiAl can be well represented.     

Off-line modelling and planning of optimal clamping forces for an intelligent fixturing system

An intelligent fixturing system (IFS) for machining aims to adaptively adjust the clamping forces to achieve minimum deformation of the workpiece according to the cutter position and the cutting forces. This paper presents the concept, architecture, control scheme, models and methodologies for an IFS. Using off-line simulations and on-line experimental verifications, the performance of the proposed IFS is evaluated and verified. As adaptive clamping forces appropriate to the dynamic machining environment are employed, the IFS offers higher quality of machined parts and greater robustness to disturbances. This system is suitable for application in high-precision machining environment as well as flexible manufacturing systems (FMS).     

垂直提升货柜托盘的弹性变形及解决办法

垂直提升货柜是物流仓储设备之一,托盘重载弹性变形问题是垂直提升货柜的关键问题。文章描述了托盘弹性变形的不良结果,对托盘进行了静态有限元分析,并且提出了解决办法。这可降低垂直提升货柜的故障率,提高产品质量,很有实用价值。     

Acceleration of regeneration treatment for nanostructured bainitic steel by rotary impacting trailed welding

The method called rotary impacting trailed welding (RITW) was proposed to accelerate the regeneration treatment of nanostructured bainitic steel welded joint. Stress and strain behaviors of welding metal under this mechanical process were analyzed using finite element software. Rotary and impacting could simultaneously take effect to generate large plastic deformation in the welded joint. Detailed changes of microstructures in the welded joints were characterized by optical microscopy and scanning electron microscopy. Results show that the large deformation of austenite in the welded joint can accelerate the bainite transformation and reduce the regeneration time. Meanwhile, large shear deformation in the austenite generated during welding has a strong effect on the bainite growth, which results in curved bainite plates.     

基于BP神经网络的汽车起重机工作幅度计算

汽车起重机由于其结构的特殊性和工作环境的复杂性,对工作幅度有比较精确的要求。在工作时,吊臂往往会发生形变。为了得出精确的工作幅度,计算相应的形变量是很有必要的。本文通过建立BP神经网络,利用实测数据,得出了较精确的形变量。为工作幅度的精确计算提供了保障。