Three-dimensional thermomechanical coupled FEM analysis of static recrystallisation during two-pass tube tension reducing process

Abstract

In this paper, a thermal dynamic numerical method was carried out to model the austenite static recrystallisation behaviour of steel 33Mn2V used in new non-quenched/tempered oil well tubes at different deformation temperatures, strain rates, deformation amounts and initial microstructures. Based on the MARC/AutoForge software, a three-dimensional thermomechanical coupled elastoplastic finite element model (FEM) was applied to simulate static recrystallisation amount of the two-pass tube tension reducing process of steel 33Mn2V for oil well. The distribution law of static recrystallisation inside the workpiece is analysed. It is indicated that the simulation results are much reliable through comparison with experimental data.     

Deformation twinning in AISI 316L austenitic stainless steel: role of strain and strain path

Abstract

AISI 316L austenitic stainless steel was deformed at different strain and strain paths. The twin boundaries in the deformed microstructure had two possible origins: decay of original annealing twins and generation of deformation twins. Assuming that rotations of grains, specifically grains on both sides of a twin boundary, are responsible for the twin decay, a simple model was proposed to bring out the domain of relative twin generation. A biaxial strain path, in general, was associated with strong twin generation – an association or dependency linked to the texture estimated values of Taylor factor. Formation of strain induced martensite was also observed to be strain and strain path dependent and was more in biaxial strain path.     

Spherical Nanoparticle–Substrate Adhesion Interaction Simulations Utilizing Molecular Dynamics

From a molecular perspective, the fundamental rolling and sliding elasto-adhesion interactions between a spherical nano-particle and an elastic substrate is studied using a computational technique based on the Molecular Dynamics (MD) approach. Initially, the particle and the substrate were equilibrated individually at 300 K. The covalent bonds interactions between the atoms of the nanoparticle are modeled by constraining the atoms to stay together throughout the simulation. The temperature of the substrate atoms is regulated by periodically scaling to mimic the bulk substrate effect to minimize the effects of the finite substrate size. The intermolecular interaction between the particle and the substrate is defined by the Lennard–Jones (LJ) 12-6 potential. The total force–displacement curves of the 4.2 and 7.89 nm particles in the cases of particle being pushed normally towards the substrate and the particle pushed tangentially, while in adhesion with substrate, are obtained. The rolling resistance moment exhibited by the smaller nanoparticle (4.2 nm) is calculated from the force–displacement curve obtained from simulations and compared to the theoretical predictions based on a two-dimensional adhesion model. It is found that the moments as a function of the rotation angle are of the same order (3.64 nN nm). The rolling and sliding force–displacement profiles when the nanoparticle is subjected to tangential load are also presented.     

Adhesion between rubber compounds and ternary-alloy-coated steel cords,Part I: effect of cobalt plating amount in ternary-alloy-coated steel cords

The adhesion between a rubber compound and ternary-alloy-coated steel cords with different cobalt plating amounts (0, 2 and 4 wt%) was investigated to understand the role of cobalt in stabilizing adhesion to the rubber compound. The adhesion property of ternary alloy coated steel cords to the rubber compound did show significant enhancement after cure for the ternary alloy coated steel cord with 2 wt% cobalt plating. Further increase of cobalt plating in ternary-alloy-coated steel cord was responsible for the poor adhesion to the rubber compound. An improvement in adhesion durability after aging in various hostile environments was shown for the ternary-alloy-coated steel cord with 2 wt% cobalt plating. The interphase between the ternary-alloy-coated steel cords and the rubber compound studied using AES showed a stable adhesion interphase by optimum cobalt plating, resulting in enhancement of adhesion retention.     

Laboratory evaluation of corrosion resistance at metallic substrates by an organic coating: delamination effects

The corrosion behaviour of an epoxy-polyamide primer applied on galvanized steel specimens during immersion in 3% NaCl aqueous solution was examined by electrochemical impedance spectroscopy (EIS). The investigation of both intact and defective coatings allowed for the comparison of their electrochemical behaviours in order to assess the anticorrosive characteristics of the system. The impedance response of the intact coating was found to correspond to a porous film presenting localised electrochemically active areas, in which the precipitation of zinc-containing corrosion products contributes to the sealing of the coating. Conversely, scribed defects cannot be spontaneously sealed and no effective protection of the metal can be achieved.     

The Effect of Different Surface Pretreatment Methods on Nano-adhesive Application in High Strength Steel and Aluminum Bonding

Epoxy adhesives (single and two components) modified with SiO₂ nano-particles were used in this investigation to glue aluminum alloy and also two types of high strength steel (dip-galvanized steel DP 600 and micro-alloyed steel ZStE340). To improve the adhesion between metal surfaces and adhesives, the metal surfaces were pretreated with: a self-indicating pretreatment (SIP^*); corundum blasting; corundum blasting + a SIP coating; and a Pyrosil^® treatment + SurALink^® primer (PG 15 for epoxy adhesive). A single-lap shear tension test, done in accordance to DIN EN 1465, was used to determine the adhesive strength. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX) analysis were used to analyze fractures that took place in the samples. The results showed that the adhesion strength of glued samples, containing the nano-particles modified adhesive, had significantly higher strength than unmodified ones. Pretreatment of the metal surfaces affected the adhesion, using nano-adhesives, only slightly. The adhesive strength values for single component epoxy resins were higher than those for two component epoxy resins. It was found that steel samples fractured adhesively at the steel surfaces. Aluminum treated samples indicated after pretreatment an increase in adhesive strength and the fracture occurred adhesively at the aluminum surfaces. Aluminum glued with two-component adhesives and pretreated with corundum blasting plus a SIP coating showed a mixed fracture mode; adhesively at the aluminum surface and cohesively in the adhesive layer.     

PRESSURE FORCE CONTROL FOR FABRICATION OF PLASTIC MICROFLUIDIC CHIPS WITH HOT EMBOSSING METHOD

A pressure force control system for hot embossing of microfluidic chips is designed with a moment motor and a ball bearing lead screw. Based on the numeric PID technique, the algorithm of pulsant integral accelerated PID control is presented and the negative effects of nonlinearity from friction, clearance and saturation are eliminated. In order to improve the quick-response characteristic, independent thread technique is adopted. The method of pressure force control based on pulsant integral accelerated PID control and independent thread technique is applied with satisfactory control performance.     

Sb基nBn型红外探测器发展现状

nBn结构红外探测器具有可消除SRH产生-复合电流和表面复合电流,实现高温工作等优点,从提出就备受全球多个研究机构青睐,并已经得到组件验证。锑基nBn结构红外探测器发展尤其迅速,已经在技术上得到突破,部分产品已经获得应用,红外探测器组件最高工作温度达150 K以上。本文从nBn结构锑基红外探测器工作原理、结构优势和国外发展现状等方面对该研究方向进行了综述报道,为高工作温度、高性能红外焦平面探测器发展提供了较好方向。     

碲镉汞高温中波红外探测器的制备研究

采用CdTe/ZnS双层钝化工艺制备了640×512@15 μm碲镉汞中波探测器。研究了退火温度对CdTe/MCT界面及CdTe钝化膜质量的影响。经测试表明:本公司制备的碲镉汞HOT中波探测器可以在125 K稳定工作,但与国外的先进技术相比仍存在差距,需要在MCT材料改进和器件加工工艺上继续深入研究,才能提高探测器的工作温度和稳定性。     

加拿大卡尔加里市Okotoks小镇太阳能小区建设

简要介绍了北美目前最大的跨季太阳能储存项目——加拿大0kotoks小镇的太阳能小区建设，对其太阳能供热系统的工作原理及利用土壤床作为储能体进行大规模跨季节太阳能储存的方法进行了分析。该项目根据不同季节可利用太阳能数量的不同，分别设置了短期（临时）太阳能储箱（STTS）及跨季节太阳能储存箱（BTES），以提高太阳能的利用率。其中，BTES的效率可达50％以上。小区太阳能家用热水系统（DWH）可满足住户60％的热水需求，而太阳能采暖系统则可满足90％采暖要求；建成后每幢住宅每年可减排5t温室气体，整个小区可减排260t／年。