Search

The forming defects of parts mainly include fracture, springback, thermal expansion, and rough surface during electric hot incremental forming, in which the springback and thermal expansion directly affects the dimensional accuracy of parts. In this paper, the combined optimization of process parameters and unsupported distances was proposed to control the dimensional accuracy of forming parts in the electric hot incremental sheet forming process. The predictive model of major errors was established through the response surface methodology, and then the multi-objective optimal model was obtained using Non-dominated Sorting Genetic Algorithms-II (NSGA-II). Meanwhile, a multi-objective optimal result was determined according to the error compensation feature of the forming process. On this basis, the effect of unsupported distances on dimensional errors was analyzed in detail, and a valid unsupported distance was proposed to further improve the forming accuracy of the whole forming region. Finally, the experimental result demonstrated that the combined optimal method proposed was accurate and feasible.

The void defect is one common problem in liquid composite molding (LCM), which seriously affects the quality of the polymer composites. The prediction of void content has become a focus of research. However, the existing studies are based on isothermal conditions and the effect of non-isothermal conditions on void formation has been rarely studied yet. In this paper, based on the analysis of the micro-flow and meso-flow in the plain-weave fabric, a mathematical model to predict the void formation has been proposed. The change of resin viscosity, curing reaction, energy transfer and surface tension under non-isothermal conditions are fully considered, so the effect of non-isothermal conditions on void formation has been obtained. The void content has been measured experimentally. The results of the prediction model are in good agreement with the experimental results. This study can provide reference for the prediction of void content and distribution of composites in polymer industry.

Plain-weave fabric is a kind of fiber preform which has been commonly used in resin transfer molding (RTM) to manufacture polymer composites. However, the edge area of plain-weave fabric is easy to shed yarns which will cause the uneven distribution of permeability between edge channel and center of mold in filling process of RTM. Meanwhile, the uneven distribution of permeability will cause the edge effect and seriously affect the final quality of composite materials. In this paper, a method to numerically calculate the permeability of edge channel which fully considers the edge area of plain-weave fabric is proposed. The experiment and simulation of edge effect in filling process are performed. The results show that the simulation of edge effect which applies the edge channel’s permeability calculated by this method are in good agreement with the experimental results. The research in this paper is meaningful to improve the accuracy of edge effect simulation so as to provide a reference for the design of mold structure.

To obtain flow behavior and workability of 7055 aluminium alloy during hot deformation, hot compression tests at different temperatures and strain rates are conducted. True stress-strain curves of 7055 aluminium alloy under different conditions are obtained and the flow stress increases with ascending strain rate and descending temperature. For Arrhenius constitutive equation, each material parameter is set as a constant, which will bring forth large error for predicting flow behavior. In this work, material parameters are fitted as a function of temperature or strain rate based on experimental results and a modified constitutive equation is established for more accurate prediction of flow behavior of 7055 aluminium alloy. The effects of temperature and strain rate on power dissipation and instability are analyzed to establish a processing map of 7055 aluminium alloy. The dominant deformation mechanism for microstructure evolution at different deformation conditions can be determined and high efficiency of power dissipation may be achieved from power dissipation map. Meanwhile, proper processing parameters to avoid flow instability can be easily acquired in instability map. According to the processing map, optimized processing parameters of 7055 aluminium alloy are temperature of 673–723 K and strain rate of 0.01–0.4 s−1, during which its efficiency of power dissipation is over 30%. Finite element method (FEM) is used to obtain optimized parameter in hot rolling process on the basis of processing map.

Two-axis roll-bending technology, with the advantages of small curvature radius, short straight section and high efficiency, is widely used in fields of aerospace and automobile. By adjusting indentation depth in two-axis roll-bending process, different curvature radius of circular and elliptic component can be formed. Roll-bending experiments and numerical simulations for component with circular and elliptic section are conducted. The results show that the forming curvature radius of circular component and its deviation both decrease with ascending indentation depth. The relationship between forming curvature radius and indentation depth is polynomial fitted. On this basis, ellipse parameter equation is established and different curvature radius at different position of the ellipse is achieved by adjustment of indentation depth. The relationship between indentation depth and forming time is obtained for elliptic component. Elliptic components with different sizes are formed. The stress distribution is uniform after roll-bending process and it increases with ascending indentation depth.

Since the deformation region involves the interaction of electric-thermal-force coupling in electric hot incremental sheet forming, the numerical simulation of the forming process is unusually difficult. Currently, the thermal-force coupling method is adopted to simulate approximately the whole forming process, and the Joule heating effect is often ignored. Therefore, the numerical simulation of Joule heating effect is especially significant for the prediction accuracy of forming process. In this paper, a novel numerical simulation method, considering electric-thermal-force parameters, was proposed to instantly update the thermal-force condition of forming region. Meanwhile, the model of contact thermal conductance was established combining geometrical and electric-thermal parameters, and then a high-precision finite element model was obtained to predict the Joule heating effect of forming region. In addition to this, the effect of thermal superposition on forming temperature was further analyzed and a modified model of contact thermal conductance was established in electric hot incremental sheet forming.

Hematopoietic differentiation is controlled by both genetic and epigenetic regulators. Long noncoding RNAs (lncRNAs) have been demonstrated to be important for normal hematopoiesis, but their function in erythropoiesis needs to be further explored. We profiled the transcriptomes of 16 murine hematopoietic cell populations by deep RNA sequencing and identified a novel lncRNA, Gm15915, that was highly expressed in erythroid-related progenitors and erythrocytes. For this reason, we named it lncEry. We also identified a novel lncEry isoform, which was the principal transcript that has not been reported before. lncEry depletion impaired erythropoiesis, indicating the important role of the lncRNA in regulating erythroid differentiation and maturation. Mechanistically, we found that lncEry interacted with WD repeat–containing protein 82 (WDR82) to promote the transcription of Klf1 and globin genes and thus control the early and late stages of erythropoiesis, respectively. These findings identified lncEry as an important player in the transcriptional regulation of erythropoiesis.

Hematopoietic differentiation is controlled by both genetic and epigenetic regulators. Long non-coding RNAs (lncRNAs) have been demonstrated to be important for normal hematopoiesis, but their function in erythropoiesis needs to be further explored. We profiled the transcriptomes of 16 murine hematopoietic cell populations by deep RNA-sequencing and identified a novel lncRNA, Gm15915, that was highly expressed in erythroid-related progenitors and erythrocytes. For this reason, we named it lncEry. We also identified a novel lncEry isoform, which was also the principal transcript that has not been reported before. LncEry depletion impaired erythropoiesis, indicating the important role of the lncRNA in regulating erythroid differentiation and maturation. Mechanistically, we found that lncEry interacted with WD repeat-containing protein 82 (WDR82) to promote the transcription of Klf1 and globin genes and thus control the early and late stages of erythropoiesis, respectively. These findings identified lncEry as an important player in the transcriptional regulation of erythropoiesis.

In recent years, some ductile fracture criteria, such as Cockcroft–Latham (C–L) criterion, Brozzo criterion, Oyane criterion, and Gurson–Tveergard–Needleman (GNT) criterion, have been proposed to analyze various material damage behaviors in the plastic deformation process. However, the first three criteria do not consider the effect of shear stress on ductile fracture, and the GNT criterion is a complex structure and a high computational cost due to the consideration of micromechanics. Therefore, Mohr–Coulomb criterion (M–C) has been proposed to describe material damage behaviors with the sample structure and the consideration of shear and principal stress. In this study, the effect of the thickness and the strain rate on the fracture strain is carefully analyzed based on uniaxial tensile tests of sheet metal, and the M–C model of coupled thickness factor is established to predict the ductile fracture of various thickness and strain conditions with 6061-T6 aluminum alloy sheet. Meanwhile, the fracture process of various strain conditions is predicted based on Abaqus/Vusdfld, and the relevant rule of ductile fracture is obtained using the numerical simulation analysis of coupled fracture criterion.

The ultrasonic peen forming simulations and experiments of stiffened plates are conducted and effects of forming parameters on bending deformation and surface properties are analyzed. The results s...

Electric hot incremental sheet forming, which is used to form hard-to-form sheet metal, is viewed as the one of rapid prototyping manufacturing technologies. However, the non-uniform stress distribution of forming regions would cause an initial contact loss phenomenon between the tool and the sheet, and an electric arc burn of the part surface is obtained due to the contact loss. In this work, a control method of axial pressure response was proposed to judge the stability of the initial contact between forming the tool and the sheet. A power supply on-off device was designed for electric hot incremental forming, and the calculation model of the initial axial force was established during deformation. Meanwhile, two response pressure values were proposed to control the power supply starting and the current intervention and to ensure the stability of the power supply during the forming process. In addition to this, the axial force and the surface of part were analyzed further in electric hot incremental sheet forming.

Stiffened plates are commonly adopted as key structure components in aerospace due to light weight structure with high strength and stiffness. Ultrasonic peening (UP) is the key process for manufacturing of wing panels with stiffened plates; however, large bending strain is difficult to be generated during free UP, which significantly affects its surface properties. Prestress UP is adopted through applying prebending moment to stiffened plates before peening process and its effects on bending curvature, surface hardness and roughness, residual stress distribution under different peening parameters are analyzed. The results show that larger chordwise bending strain can be obtained in prestress UP and it increases with decreasing prebending curvature radius and decreasing offset distance as well as increasing firing pinvelocity. Compared to free UP, smaller surface roughness, larger surface hardness, larger and deeper compressive residual stress can be acquired in prestress UP and their differences between two UP ways increase with decreasing prebending curvature radius. Meanwhile, increasing firing pin velocity and decreasing offset distance are beneficial to hardening extent of peening and generation of large and deep compressive residual stress. However, large firing pin velocity results in large surface roughness and appropriate value of firing pin velocity should be used. Small offset distance will decrease the peening efficiency; therefore, comprehensive consideration of large bending deformation and peening efficiency should be considered. Prestress UP is effective to increase bending strain and improve surface properties of stiffened plate and this study can provide guidance for parameters selection.

Shot peening (SP) is widely used in aerospace factories and automotive enterprise for large thin panel forming and strengthening, such as the wing skin panels, spars, and car bonnet. The large panels or sheets are subjected to SP processing, followed by the bending, spanning, and growth (elongation). Precise elongation calculation is a promising and challenging task. This work which includes the mathematical model finite element method (FEM) simulation for predicting the 7050-T7451 aluminum alloy strip elongation with respect to special SP parameters is presented to analyze the potential effects, which was also validated by experiments. As to the integral wing spars, the rolling direction orientations with regard to the rolled spar blank have different effect on elongation after the SP strengthening and shaping. The compressive stress induced by SP will break the original residual stress equilibrium state after rolling. Both experiments and explicit-implicit model predictions showed that the tensile residual stress induced by rolling contributes to the elongation. On the contrary, the compressive residual stress prevents the strip from elongation. Furthermore, the initial residual stress effect is negligible when the thickness is large (above 6-mm thickness). Considering the 7050-T7451 aluminum alloy coefficient of thermal expansion is high, therefore, the temperature is an important factor for the long length spar. In addition, we found the elongation was inversely proportional to thickness and independent of section dimension. The numerical results showed that the elongation was more sensitive to the shot number (coverage) than impact velocity, which was explained based on the newly proposed mathematical model.

The incremental sheet forming technology as a flexible forming process is often used to fabricate parts with small batches or individuation. However, the lubrication of this technology is usually difficult and complex due to the rigidity in the contact between tool and sheet. In this work, a novel lubrication method with graphite grease/oil is adopted to fabricate parts with aluminum in incremental sheet forming, which is simple and low-cost compared to previous methods. Meanwhile, other two lubrication methods, such as oil lubrication and graphite lubrication, are adopted as control groups. The surface roughness profile and the surface morphology obtained by the new method are both better than that obtained by control groups. Moreover, machining and step-down traces of the forming surface of specimens fabricated, thickness distribution, and forming force could be availably improved with the novel lubrication method.

The electric assistance incremental forming technology is usually adopted to form hard-to-form sheet metals. Recently, the local heating method by current is used to fabricate specimens with these materials due to low costs and simple setups. However, the heating method has four natural defects: inhomogeneous temperature distribution, arc burns for the sheet and the tool, unsuited for multistage forming, and complex lubrication processes. In this work, a novel heating design, directly making current flow from the one side of the sheet into the other side of the sheet, was proposed to form specimens with TC4 Ti alloy. Meanwhile, different current values were adopted in numerical simulation and experiments, which demonstrated that a current value of 500 (A) should be selected to fabricate the specimen with TC4 Ti alloy. In addition to this, some forming results, such as temperature variations, roughness, and tool damage, obtained respectively by local and integral electric heating incremental forming processes were analyzed further.

The surface coverage induced by shot peening (SP) has substantial influence on the fatigue durability of components. The underlying motivation for this work was to predict coverage, compressive residual stress (CRS), and roughness of the alloy, Al 2024-T351. These characteristics were assessed by computational modelling that is based on a combined finite element method (FEM) and discrete element method (DEM). The advantage of this combined method is that we only need to combine a representative dimple with the impact locations obtained from different SP parameters in DEM. Especially in the parametric analysis was carried out to evaluate coverage regarding to SP parameters. Furthermore, the DEM simulation generates an input file for the FEM simulation, which is then used to analyse the CRS and the resulting roughness that corresponds to SP parameters. The numerical coverage study (based on the combined DEM-FEM method) exhibited the same trend as the experimental data, with respect to the percentage of full coverage time, t, and is more reliable than theoretical calculations. In a practical sense, the developed model has the ability to accurately achieve the desired surface with the ability to adjust the SP parameters efficiently.

The sheet with 1060 Al often is used to fabricate aluminum parts at room temperature in the incremental sheet forming process due to the fact that the metal has a high ductility in the normal temperature. However, the material can cause a large quantity of springback for parts formed to influence dimensional accuracy. In this paper, the use of the electric hot incremental forming process (EHIF) can effectively improve the dimensional accuracy of parts compared to single-stage forming and double-stage forming at room temperature. The effect of main process parameters, such as tool diameter, feed rate, step size, and current, on temperature is studied in detail using the EHIF. Some target values, namely, the maximum temperature, the average temperature, and the maximum temperature difference, are measured with a cone using 1060 Al. Moreover, the response surface methodology and Box–Behnken design have been employed to analyze results in detail and to establish respectively corresponding models to predict target values. Finally, the evaluating model of temperature uniformity is proposed and verified according to the previous models.

Multistage forming is usually adopted to form those parts with steep angle or straight wall during single point incremental forming. In order to study multistage single point incremental forming further, based on an experiment method and a mathematic analysis method, straight wall cylinders are fabricated with different materials and different heights to investigate dimensional accuracy of specimens obtained. Three kinds of materials including 1060 aluminum, Q235 steel and DC04 steel are selected to deform specimens with four-stage single point incremental forming. The mathematic model of dimensional error is proposed to predict the sinking defect according to the law of energy conservation. In addition to this, the strain strength coefficient (K) and the axial feed rate (v 1) are studied in detail for the largest deviation of specimens. Experiment results demonstrate that the mathematic model is feasible and an optimal v 1 obtained effectively improves the dimensional accuracy of specimens.

Background Acquired aplastic anemia (AA) is characterized by deficiency or dysfunction of the bone marrow (BM) microenvironment. However, little is known about the impairment of BM-derived mesenchymal stem cells (MSCs) in AA patients. Methods We used Illumina HiSeqTM 2000 sequencing, quantitative real-time polymerase chain reaction (qRT-PCR), flow cytometry (FCM), and Western blotting to test the expression of CD106 gene (vascular cell adhesion molecule 1 (VCAM1)) and CD106 protein of BM-MSCs. Furthermore, we used hematoxylin and eosin (H&E) and histochemical staining analysis, immunofluorescence, and the formation of capillary-like structures to analyze capillary tube-like formation in vitro; we also used the Matrigel plug assay to test in vivo vasculogenesis, and an assay of colony forming units (CFUs) and colony-forming unit-megakaryocyte (CFU-MK) to detect the support function of MSCs in vitro. The in vivo engraftment of CD34+ cells and MSCs in NOD/SCID mice was tested by FACS and survival assay; the expression of NF-κB was tested by NanoPro analysis and immunofluorescence. NF-κB-regulated CD106 gene (VCAM1) was confirmed by tumor necrosis factor alpha (TNF-α)-stimulated and lipopolysaccharide (LPS)-stimulated MSCs, blockade assay, and immunofluorescence. Results Here, we report that BM-MSCs from AA patients exhibited downregulation of the CD06 gene (VCAM1) and low expression of CD106 in vitro. Further analysis revealed that CD106+ MSCs from both AA patients and healthy controls had increased potential for in vitro capillary tube-like formation and in vivo vasculogenesis compared with CD106– MSCs, and the results were similar when healthy MSCs were compared with AA MSCs. CD106+ MSCs from both AA patients and healthy controls more strongly supported in vitro growth and in vivo engraftment of CD34+ cells in NOD/SCID mice than CD106– MSCs, and similar results were obtained when healthy MSCs and AA MSCs were compared. The expression of NF-κB was decreased in AA MSCs, and NF-κB regulated the CD106 gene (VCAM1) which supported hematopoiesis. Conclusions These results revealed the effect of CD106 and NF-κB in BM failure of AA. Electronic supplementary material The online version of this article (doi:10.1186/s13287-017-0620-4) contains supplementary material, which is available to authorized users.

Acquired bone marrow failure syndromes (aBMFS) encompass a wide range of diseases. A study to investigate WT1 expression in BM was conducted in 387 patients with aBMFS in China. The WT1 level in patients with aplastic anemia (AA) was significantly lower than that in patients with paroxysmal nocturnal hemoglobinuria (PNH, p = .023) and myelodysplastic syndrome (MDS, p

Multistage forming is usually adopted to fabricate the part of steep angles during single point incremental forming (SPIF). However, the central sinking of specimens is usually a major defect during the multistage negative incremental forming process. In this study, three materials (1060 aluminum, Q235, and DC04 steel) were used separately to fabricate specimens with different heights and to study the effect of materials on dimensional accuracy of parts formed. Meanwhile, the effect of stepping rates on the largest error was investigated. In addition to this, a mathematic model was proposed to predict the central sinking value of specimens based on the law of energy conservation. The experimental result demonstrates that the stepping rate and the strain strength coefficient (K) are mainly influential factors on the dimensional accuracy and that the mathematic model is feasible.

The desired peening outcome of the peening process like curvature is based on the reasonable determination of shot peening (SP) parameters. In this work, an assessment about accuracy of randomly distributed shots model was performed by comparing the experimental test. And, the comprehensive nonlinear dynamic elastic-plastic finite element analysis was conducted to reveal the difference between the regularly ordered shots model and the randomly distributed shots model in terms of induced stress and residual stress. The comparison indicated a difference between those two kinds of models under high coverage. Based on the randomly distributed shots model, we also found curvature radius increased with increasing thickness but decreased with shot velocity and increasing coverage. At last, we analyzed the reason by associating the residual distributions. Contrary to the shot peening parameters, shot velocity and coverage, the thickness of the strip is the most influential factor which inhibits the decrease of curvature radius. It should be noted that the over-high impact velocity will lead to a buckling distortion on the strip. Furthermore, the relation between the impact velocity and coverage was developed.

Mesenchymal stem cells (MSCs) have shown promise for use in cell therapy, and due to their tumor tropism can serve as vehicles for delivering therapeutic agents to tumor sites. Because interleukin-8 (IL-8) is known to mediate the protumor effect of MSCs, elimination of IL-8 secretion by MSCs may enhance their safety for use in cancer gene therapy. However, little is known concerning the effect of endogenously secreted IL-8 on MSCs. We performed studies using placenta-derived MSCs (PMSCs) to determine whether knockdown of IL-8 would influence their biological activity. We first verified that IL-8 and its membrane receptor CXCR2, but not CXCR1, were highly expressed in PMSCs. We then employed lentivirus-mediated small hairpin RNA interference to generate stable IL-8-silenced PMSCs, which displayed a variety of characteristic senescent phenotypes. We observed that at day 9 post-transfection, IL-8-silenced PMSCs had become larger and displayed a more flattened appearance when compared with their controls. Moreover, their proliferation, colony forming unit-fibroblast formation, adipogenic and osteogenic differentiation, and immunosuppressive potentials were significantly impaired. Enhanced senescence-associated β-galactosidase (SA-β-gal) activity and specific global gene expression profiles confirmed that IL-8 silencing evoked the senescence process in PMSCs. Increased levels of p-Akt and decreased levels of FOXO3a protein expression suggested that reactive oxygen species played a role in the initiation and maintenance of senescence in IL-8-silenced PMSCs. Notably, the majority of CXCR2 ligands were downregulated in presenescent IL-8-silenced PMSCs but upregulated in senescent cells, indicating an antagonistic pleiotropy of the IL-8/CXCR2 signaling pathway in PMSCs. This effect may promote the proliferation of young cells and accelerate senescence of old cells.

CXCL10/IFN-γ-induced protein 10 (IP-10) and its corresponding receptor CXCR3 have long been considered to be involved in the pathophysiology of type 1 T (Th1) cell-orientated autoimmune diseases. However, the exact role of CXCL10 in the pathogenesis of aplastic anaemia (AA) has not been thoroughly studied. The aim of our study was to evaluate the plasma level of CXCL10 and its effects on CD4+ T cell differentiation in AA. In our study, we found that an elevated plasma level of CXCL10 was negatively correlated with platelet, absolute neutrophil and reticulocyte counts, while it was positively correlated with the proportion of lymphocytes in white blood cells in AA patients. To confirm the pro-inflammatory effects of CXCL10 in AA, we isolated CD4+ T cells and evaluated the function of CXCL10 in CD4+ T cell differentiation. In vitro stimulation experiments further revealed the pro-inflammatory role of CXCL10 in AA, partially by promoting the secretion of interferon (IFN)-γ and IL-17. In addition, CXCL10 significantly skewed CD4+ T cell differentiation to Th1 cells and T helper 17 (Th17) cells in AA patients, while it inhibited the differentiation of type 2 T (Th2) cells only in controls. The mRNA expression of transcription factors representative of T cell differentiation was detected by RT-PCR. Consistently, our results showed that after CXCL10 treatment, the expression of T-bet and RORγt was significantly enhanced, while the expression of GATA3 was inhibited. In conclusion, our results indicated that CXCL10, a pro-inflammatory chemokine, might be involved in the abnormal immune response in AA.

Hematopoietic differentiation is controlled by both genetic and epigenetic regulators. Long non-coding RNAs (lncRNAs) have been demonstrated to be important for normal hematopoiesis, but their function in erythropoiesis needs to be further explored. Here, we profiled the transcriptome of 17 murine hematopoietic cell populations by deep sequencing and identified a novel lncRNA, that was highly expressed in erythroid-related progenitors and erythrocytes. For this reason, we named it lncEry. We also identified a novel lncEry isoform, which was the principal transcript and has not been reported before. Furthermore, we found that nearly 90% of lncEry molecules localized to the nucleus. Next, we performed knockdown and knockout assays to study the function of lncEry, and found that lncEry depletion impaired erythroid differentiation. RNA sequencing analysis showed that lncEry depletion decreased the expression of erythrocyte homeostasis or differentiation related genes, including globin genes, thus indicating its important role in regulating erythroid differentiation. Mechanistically, we performed RNA-pulldown assays and found that lncEry could interact with Wdr82, a component of the Set1A histone H3-Lys4 methyltransferase complex. In addition, a series of molecular assays indicated that lncEry could stabilize the localization of Set1A/Wdr82 complex to facilitate H3K4me3 on the promoter region of globin genes and participate in regulating erythropoiesis. These findings identify lncEry as an important player in the transcriptional regulation of globin genes to coordinate erythropoiesis. Disclosures No relevant conflicts of interest to declare.

Targeting the issue that structure performance cannot be enhanced due to non-peened area being overlarge during shot peening forming of perforated plate, we proposed a peening forming technique of combining strengthening ring with strip peening path. The basic idea of the study is to conduct a ring strengthening around hole and carry out narrow strip peening on shot peening coverage. Then, we investigated the influence of the thickness and width of strengthening ring on the curvature radius difference. Moreover, the thickness and width curves of strengthening ring corresponding to shot peening under different peening parameters such as current intensity and firing pin diameter are discussed critically. The implementation shows that the specific dimension of strengthening ring and strip peening parameters can dramatically reduce the curvature radius difference between peened area around strengthening ring and non-peened area of the hole. With it, we can obtain a good peening forming effect on perforated plate and accordingly optimize the structure of the perforated plate.

Since the conventional simulation for multi-stage single point incremental forming cannot describe the phenomenon of ductile fracture of material, the suitability of a deformation strategy is not evaluated. Therefore, the numerical prediction of ductile fracture is especially significant for the application and development of MSSPIF. In this paper, the calculation of forming stages and the evaluation criteria of ductile fracture are separately established to design intermediate profiles and to estimate initial crack of material for MSSPIF of straight wall parts based on phenomenological modified Mohr–Coulomb. Moreover, the effect of some factors (stress triaxiality, normalized Lode angle, and forming stage) on ductile fracture is analyzed in detail, and then a high-precision finite element model coupled MMC3 is established to predict the ductile fracture of material during MSSPIF. Meanwhile, the fracture forming limit diagram for MSSPIF is also obtained and higher than that obtained by single-stage single point incremental forming.

In order to improve the formability of 5083 aluminum alloy in hot forming process. The effects of strain rate, temperature and elongation on microstructure evolution of 5083 aluminum alloy were analyzed by single tensile test at high temperature on RG2000-20 universal thermal tensile tester and numerical analysis. The results show that the smaller the strain rate, the larger the grain size and volume fraction of dynamic recrystallization, the lower the deformation temperature, the smaller the dynamic recrystallization degree and the larger the cavity size. Dynamic recrystallization occurs only when the deformation degree exceeds the corresponding boundary value. When deformation reaches a certain degree, the completely dynamic recrystallization can be obtained, and the volume fraction and void radius will increase rapidly. Furthermore, a dynamic recrystallization mathematical model of 5083 aluminum alloy for high temperature plastic deformation was established by linear regression method and proved to be reliable in numerical analysis.

Asymmetrical shear rolling with velocity asymmetry and geometry asymmetry is beneficial to enlarge deformation and refine grain size at the center of the thick plate compared to conventional symmetrical rolling. Dynamic recrystallization (DRX) plays a vital role in grain refinement during hot deformation. Finite element models (FEM) coupled with microstructure evolution models and cellular automata models (CA) are established to study the microstructure evolution of plate during asymmetrical shear rolling. The results show that a larger DRX fraction and a smaller average grain size can be obtained at the lower layer of the plate. The DRX fraction at the lower part increases with the ascending speed ratio, while that at upper part decreases. With the increase of the offset distance, the DRX fraction slightly decreases for the whole thickness of the plate. The differences in the DRX fraction and average grain size between the upper and lower surfaces increase with the ascending speed ratio; however, it varies little with the change of the speed ratio. Experiments are conducted and the CA models have a higher accuracy than FEM models as the grain morphology, DRX nuclei, and grain growth are taken into consideration in CA models, which are more similar to the actual DRX process during hot deformation.

Aluminium alloy thick plate is widely used in field of aerospace and automobile industry for its light weight, high strength, good corrosion resistance and formability. Hot rolling is the key process of preparation for thick plates, however, the conventional symmetrical rolling process causes large deformation on the surface and small deformation in the central portion of the thick plate, resulting in inhomogeneous deformation, microstructure and property distributions through the thickness direction of the plate. Asynchronous rolling is beneficial for deformation permeation into the central part of thick plate with introduction of strong shear strain due to velocity asymmetry of two work rolls. However, the plate will bend towards the slower roll due to deformation asymmetry at upper and lower surface of the plate and serious bending is bad for multi-pass rolling process. Asymmetrical shear rolling with velocity asymmetry and geometry asymmetry is adopted in this study. Compared to asynchronous rolling, there is a horizontal offset distance of upper roll in outlet direction. A moment will be applied to the plate in the opposite direction of bending towards the slower roll by an offset distance of the slower roll. The comparisons of distributions of equivalent strain, temperature, DRX fraction and average grain size between symmetrical rolling and asymmetrical shear rolling are studied. The effects of velocity asymmetry and offset distance on microstructure variation and microstructure distribution at different positions of the plate are studied. Due to larger velocity of lower work roll, larger equivalent strain and higher temperature appear at lower layer of the plate, which results in higher DRX fraction and finer grain size. The speed ratio contributes greatly to sufficient DRX process and finer grain size; while the ascending offset distance decreases the DRX fraction. Therefore, speed ratio plays significant role in deformation permeation and grain refinement in asymmetrical shear rolling and the offset distance is mainly used to decrease the bending behaviour of the plate. This study can provide guidance to thick plate preparation with good properties in asymmetrical rolling process.

Acquired aplastic anemia (AA), characterized by pancytopenia in peripheral blood (PB) and bone marrow (BM) hypoplasia, is a bone marrow failure syndrome. The late evolution to myelodysplastic syndromes (MDS)/acute myeloid leukemia (AML) is the most common clonal complication in refractory patients