Crystal plasticity finite element method simulation of equal channel angular pressing

Severe plastic deformation (SPD) has been the subject of intensive investigations in recent years because of the unique physical and mechanical properties of ultrafine grained (UFG) materials fabricated by this technique. Equal channel angular pressing (ECAP) is the most frequently used SPD technique due to its efficiency in grain refinement. The deformation mechanism during the ECAP process is very complicated and it has always been assumed to be a simple shear along the intersecting plane of two ECAP channels in most published literatures. A number of experiments and numerical simulations have revealed that the simple shear based theory could not accurately predict the microstructure development, plastic strain (or strain rate) distributions and texture evolutions. Even though many studies have contributed to understanding of the deformation mechanism of the ECAP process, some research areas have still not been fully explored, such as texture modelling. Up to now, few texture simulations in the literatures have been carried out based on the real full-scale ECAP process and most of them were conducted using the simple shear theory. Therefore, a systematic study on modeling of texture evolution of the real ECAP process and investigation of the effects of the ECAP parameters on texture evolution are essential. In the present study, a crystal plasticity finite element method (CPFEM) model has been developed to offer a systematic understanding of the deformation behavior and texture evolutions of single crystals, bicrystals and a polycrystal during the full scale ECAP processes. The developed CPFEM model has been validated by comparing the simulation results with the experimental observations

Microstructure and mechanical properties of AA5005/AA6061 laminated composite processed by accumulative roll bonding

ULTRAFINE-GRAINED (UFG) materials have been gathering much interest for the last two decades as the materials have extraordinary mechanical properties such as high strength, low temperature superplastisity, and high corrosion resistance. Severe plastic deformation (SPD) is the most widely used method to produce UFG materials. Accumulative roll bonding (ARB) has become one of the most important SPD techniques since it was first introduced by Saito et al.[1] As the same equipment as in conventional rolling is used, ARB is considered to be one of the most promising methods for manufacturing UFG sheet materials

A Numerical Study On The Indoor Thermal Environment Served By A Novel Air Source Heat Pump Powered Bed-Based Space Heating (ASHP-BBSH) System

A numerical study on the indoor thermal environment served a novel air source heat pump powered bed-based space radiation heating (ASHP-BBSH) system is reported in this paper. This novel system combines the merits from a Chinese Kang, or a heated bed, widely used in northern rural China and a standard ASHP system, which can provide localized space heating via both convection and radiation to maintain a comfortable indoor thermal environment, at reduced energy use. In this novel bed-based system, a bed is heated and thus used as a radiator for providing space heating at both daytime and nighttime. In this paper, firstly, a numerical model for a bedroom with a heated bed was firstly built and a manikin with simplified dimensions and physiological shape sitting on the heated bed has been added to the numerical model. Secondly, using the model, the relationships between indoor thermal environment and a number of influencing factors, including the bed surface temperature and heating area were numerically studied. Thirdly, a comparison between the novel system and a standard ASHP system was numerically conducted to demonstrate the advantages of the novel bed-based space heating system. The numerical results show that compared with a standard ASHP system, a better thermal comfort level and higher energy saving potential can be achieved by applying the ASHP-BBSH system. Necessary parameters for the system design and operation in the follow-up experimental work were provided

Coupled effects of initial orientation scatter and grain-interaction to texture evolution: a crystal plasticity FE study

Grain orientation and neighbourhood are two main factors that determine the in-grain and global texture. The coupled effects of them to texture evolution has not been well understood. In this work, initial orientations scattered from exact Cube at four different levels (2 ° , 5 ° , 20 ° and 45 ° ) were developed, running from near single crystal to polycrystal, which yielded grain-interaction at various grades. A crystal plasticity finite element model was developed and the predicted texture after a 50% and 75% reduction has been validated by experimental observations of both single crystals and polycrystals. When the deviation angles are small, the global texture is similar to that in exact Cube, where crystal rotation about transverse direction is dominant. Initial orientations of large scatter and grains of strong interaction led to high crystal rotations and the formation of rolling texture. To study the grain-interaction to specific grains, the orientations of neighbouring grains were replaced. It was found that texture evolution in the region close to grain boundaries is sensitive to grain-interaction, while crystal rotations in the inner region are basically determined by the initial orientation

Insights into the behavior of polyphosphate lubricant in hot rolling of mild steel

Hot rolling with a large reduction is usually performed to produce the fine-grained strips, which leads to a severe wear of work roll and affect substantially the strip quality. As a result, lubricants are usually introduced to reduce these problems, with inorganic polyphosphate glass polymer showing the most promising prospective. This study aims to provide a new insight into the lubrication film at roll/strip interface in hot rolling. A series of lubricated hot rolling tests were performed by a 40wt% sodium metaphosphate aqueous solution under 20-60% reduction, at 950-1150 °C and 0.5 m/s. Thermal behaviors of sodium polyphosphate and the rolled strip samples were analyzed by high temperature laser confocal microscope, Secondary Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDX), Focused Ion Beam (FIB) and Transmission Electron Microscopy (TEM) etc. The results reveal that the lubrication film thickness at the roll/strip interface varied from 0.6 to 4.3 µm with the rolling load being reduced up to 6.1% and friction coefficient up to 16%. FIB and TEM analysis reveal that the polyphosphate film has an amorphous structure which was penetrated through by the oxide scale. It had been found that the polyphosphate lubrication performance was improved at a higher reduction and temperature, which contributes to the friction and oxidation-reduction

The Anti-Inflammatory Effects of a Yin Zhi Huang Soup in an Experimental Autoimmune Prostatitis Rat Model

The present study aimed to investigate the therapeutic effects of the Chinese herbal medicine Yin Zhi Huang soup (YZS) in an experimental autoimmune prostatitis (EAP) rat model. In total, 48 rats were randomly divided into the following four groups (n=12/group): saline group, pathological model group, Qianlietai group, and YZS group. We determined the average wet weight of the prostate tissue, the ratio of the wet weight of the prostate tissue to body weight, tumor necrosis factor-alpha (TNF-α) levels in the blood serum, the expression of inducible nitric oxide synthase (iNOS) in the rats’ prostate tissues, and the pathological changes in the prostate tissue using light microscopy. YZS reduced the rats’ prostate wet weight, the ratio of the prostate wet weight to body weight, and TNF-α levels in the blood serum and inhibited the expression of iNOS in the rats’ prostate tissues (P<0.05). Following YZS treatment, the pathological changes in the rats’ prostates were improved compared with those in the model group (P<0.05). Furthermore, YZS treatment reduced inflammatory changes in the prostate tissue. It also significantly suppressed proinflammatory cytokines, such as TNF-α, and chemokines, such as iNOS, in the rat model of EAP

A study of plastic deformation behavior during high pressure torsion process by crystal plasticity finite element simulation

High pressure torsion (HPT) is an efficient technique of producing ultrafine grained materials with exceptional small grain size. In this study, a crystal plasticity finite element method (CPFEM) model has been developed to investigate the plastic deformation behavior of pure aluminum single crystal during the HPT process. The simulation results show that, the distribution and evolution of the macroscopic plastic strain and the accumulative shear strain are similar. The value increases with the increase of the distance from the center as well as the number of revolution. The simulation is capable of reflecting the anisotropic characteristics of HPT deformation, a non-homogenous deformation along the circumference of the sample could be observed. At the early stage of HPT deformation, the critical resolved shear stress (CRSS) along the radial direction presents a rapid increase, followed by a moderate increase and then reaches the near-saturate state. As the HPT deformation proceeds, there is a relatively weak increase in the quasi-saturate value and the near-steady region expands gradually towards the sample center. The orientation changes during the HPT process with increasing applied strain predicted by the developed CPFEM model are also presented

Investigation of ultrafine grained AA1050 fabricated by accumulative roll bonding

Accumulative roll bonding (ARB) is an effective method to produce ultrafine-grained (UFG) sheet materials with high strength. In this work, fully annealed AA1050 sheet with an initial thickness of 1.5. mm was processed by ARB up to five cycles. The microstructure was examined by optical microscopy (OM) and transmission electron microscopy (TEM). The results revealed that ARB is a promising process for fabricating ultrafine grained structures in aluminium sheets and the average grain size after 5-cycle ARB reached approximately 300. nm. Meanwhile, a remarkable enhancement in the strength was achieved and the value was about three times the strength of starting material. The microstructure at the bond interface introduced during ARB was investigated and its influence was discussed in detail. In addition, the microstructure and mechanical properties after ARB were compared with that after deformation by equal channel angular pressing (ECAP) up to the same strain. It has been found that ARB is more efficient in grain refinement and strengthening, which can be attributed to the different deformation modes of the two techniques

Microstructure and mechanical properties of 1050/6061 laminated composite processed by accumulative roll bonding

1050/6061 laminated composite sheets have been fabricated by the accumulative roll bonding (ARB) using commercial 1050 and 6061 aluminium alloys. Through-thickness hardness and tensile testes have been conducted to examine the mechanical properties of the laminated composites. It has been found that the strength of the composite materials is between the strengths of 6061 and 1050 primary materials. The average hardness of the 6061 layer is almost twice of the average value of the 1050 layer for both one and two-cycle processed composites. Optical microscopy, scanning electron microscopy and transmission electron microscopy were used to evaluate the microstructure of the composites. Grain refinement has been observed for both the 1050 and 6061 layers. The 1050 layer showed coarser and more equiaxed microstructure than the 6061 layer after the second ARB cycle