Effect of wire diameter compression ratio on drawing deformation of micro copper wire

A crystal plasticity finite element model was developed for the drawing deformation of pure copper micro wire,based on rate-dependent crystal plasticity theory.The impact of wire diameter compression ratio on the micro-mechanical deformation behavior during the wire drawing process was investigated.Results indicate that the internal deformation and slip of the drawn wire are unevenly distributed,forming distinct slip and non-slip zones.Additionally,horizontal strain concentration bands develop within the drawn wire.As the wire diameter compression ratio increases,the strength of the slip systems and the extent of slip zones inside the deformation zone also increase.However,the fluctuating stress state,induced by contact pressure and frictional stress,results in a rough and uneven wire surface and diminishes the stability of the drawing process.

Effect of Tegafur Gimeracil Oteracil Potassium Capsule + Kangai injection + intensity-modulated radiation therapy on the cellular malignant biological processes in advanced cervical cancer lesion

Objective:To study the effect of Tegafur Gimeracil Oteracil Potassium Capsule + Kangai injection + intensity-modulated radiation therapy on the cellular malignant biological processes in advanced cervical cancer lesion.Methods: Patients who were diagnosed with advanced cervical cancer in the Second People Hospital of Banan District Chongqing between April 2015 and March 2017 were selected and divided into two groups, group A received Tegafur Gimeracil Oteracil Potassium Capsule + Kangai injection + intensity-modulated radiation therapy, and group B received cisplatin + intensity-modulated radiation therapy. Serum contents of tumor markers, tumor invasion molecules and tumor proliferation molecules of two groups of patients were detected before treatment as well as 2 weeks and 4 weeks after treatment.Results: Serum E-cad, STMN1, Fas and p53 levels of both groups of patients 2 weeks and 4 weeks after treatment were significantly higher than those before treatment while TSGF, TK1, SCC-Ag, CA125, OPN, MMP9, NGAL, CyclinE, CyclinD1 and PCNA levels were significantly lower than those before treatment, and serum E-cad, STMN1, Fas and p53 levels of group A 2 weeks and 4 weeks after treatment were significantly higher than those of group B while TSGF, TK1, SCC-Ag, CA125, OPN, MMP9, NGAL, CyclinE, CyclinD1 and PCNA levels were significantly lower than those of group B.Conclusion: Tegafur Gimeracil Oteracil Potassium Capsule + Kangai injection + intensity-modulated radiation therapy for advanced cervical cancer can induce cancer cell apoptosis and inhibit cancer cell proliferation and invasion.

Evaluation of service-induced microstructural damage for directionally solidified turbine blade of aircraft engine

Turbine blades of gas turbine engines usually suffer from severe operational conditions characterized by high temperature and stress. Severe operational conditions during service cause microstructural changes in turbine blades and degrade their mechanical properties. In this study, service-induced microstructural damages in serviced turbine blades manufactured from a directionally solidified superalloy were evaluated. The observed microstructural damage of the turbine blade mainly involves the coarsening and rafting of γ' precipitates. The leading edge of 60% height of the turbine blades undergone most severe microstructural damage with significant microstructural evolution at this area. Microstructural damage affects the mechanical properties such as Vickers hardness, that is,Vickers hardness decreases as the equivalent diameter decreases. Microstructural damage shows great positiondependent feature as service temperature and radial stress on blade changes. With the aid of energy-dispersive spectrometer(EDS) analysis on carbide, the transformation of carbide does not exist. In addition, no topological closed-packed phase exists in the turbine blade.

Low-cycle fatigue behavior of a directionally solidified Ni-based superalloy subjected to gas hot corrosion pre-exposure

The influence of gas high-temperature hot corrosion(HTHC) pre-exposure on low-cycle fatigue(LCF)behavior was characterized for the directionally solidified(DS) Ni-based superalloy DZ125. Fatigue tests were carried out at 850 ℃ in the pre-exposed and unexposed specimens for 2, 15 and 25 h. Experimental results show that the porous corrosion scale and γ′-depleted layer formed in gas hot corrosion condition alter the crack initiation mechanisms of the superalloy. Fatigue cracks of the pre-exposed specimens originate from multiple surface locations where spalling of the corrosion products occur,while nucleation of unexposed specimen begins in the defects close to the surface. There is a significant reduction in LCF behavior for pre-exposed specimens in comparison with unexposed specimens.

Role of Diffusion-weighted and Contrast-enhanced Magnetic Resonance Imaging in Differentiating Activity of Ankylosing Spondylitis

Background： Previous studies showed that combining apparent diffusion coefficient （ADC） value with the Spondyloarthritis Research Consortium of Canada （SPARCC） index value might provide a reliable evaluation of the activity of ankylosing spondylitis （AS）, and that contrast-enhanced （CE） magnetic resonance imaging （MRI） is unnecessary. However, the results were based on confirming only a small random sample. This study aimed to assess the role of CE-MRI in differentiating the disease activity of AS by comparingADC value with a large sample. Methods： A total of l 15 patients with AS were enrolled in accordance with Bath AS Disease Activity Index and laboratory indices, and 115 patients were divided into two groups, including active group （n = 69） and inactive group （n 46）. SPARCC, ASI, and ADC values were obtained from the short tau inversion recovery （STIR）, diffusion-weighted imaging （DWI）, and CE-MRI, respectively. One-way analysis of variance and receiver operating characteristic analysis were performed for all parameters. Results： The optimal cutoff values （with sensitivity, specificity, respective area under the curve, positive likelihood ratio, and negative likelihood ratio） for the differentiation between active and inactive groups are as follows： SPARCC = 6 （72.06%, 82.61%, 0.836, 4.14, 0.34）; ASI （%） 153 （80.6%, 84.78%, 0.819, 5.3, 0.23）; ADC value - 1.15 × 10 3 mm2/s （72.73% 81.82%, 0.786, 4, 0.33）. No statistical differences were found among the predictive values of SPARCC, △SI, and ADC. Multivariate analysis showed no significant difference between the combination of SPARCC and ADC values with and without ASI. Conclusions： Using large sample, we concluded that the combination of STIR and DWI would play significant roles in assessing the disease activity, and CE-MRI sequence is not routinely used in imaging of AS to avoid renal fibrosis and aggravation of kidney disease.

Homoclinic and Heteroclinic Flows in Global Attractor for Davey-stewartson Ⅱ Equation

By the variable transformation and generalized Hirota method, exact homoclinic and heteroclinic solutions for Davey-Stewartson II （DSII） equation are obtained. For perturbed DSII equation, the existence of a global attractor is proved. The persistence of homoclinic and heteroclinic flows is investigated, and the special homoclinic and heteroclinic structure in attractors is shown.

Low cyclic fatigue behavior of electron-beam-welded Ti–6Al–4V titanium joint

The low cycle fatigue（LCF） tests were carried out using symmetrical cyclic loading under total strain amplitude control conditions.The present paper is devoted to investigating the cyclic deformation response of Ti–6Al–4V titanium and the electron-beam-welded（EBW） joint in the following aspects,i.e.,cyclic deformation behavior,fatigue life and fatigue fracture behavior.The results show that the softening of the joint is significant at larger strain ranges,while not obvious at smaller strain ranges.The joint shows shorter fatigue life at larger strain ranges and equivalent fatigue life at smaller strain ranges compared with Ti–6Al–4V base metal.A fatigue crack of the joint not only originates at the surface or subsurface,but also at defects in the fusion zone（FZ）.The crack propagation zone of Ti–6Al–4V base metal shows ductile fracture mechanism,while the joint shows brittle fracture mechanism.In all the fatigue fracture zones many dimples appear,showing the typical ductile fracture.

Low-cycle fatigue behavior of DZ125 superalloy under prior exposure conditions

Low-cycle fatigue(LCF) behavior of the directionally solidified(DS) nickel-based DZ125 superalloy was studied at elevated temperature(980 ℃).Specimens were,respectively,exposed for 0,2,25,50,and 100 h in air.The fatigue life of pre-exposed specimens is lower than that of unexposed specimens.The result is closely associated with fatigue crack initiation and propagation due to oxygen embrittlement and cycle loading.Detailed fractographic evaluations indicate the fatigue life is closely related to the surface microstructural modification.The resulting changes in microstructure cause the decrease in the effective area and the increase in actual stress.A methodology based on the continuum damage mechanics is developed to describe the correlation between the residual LCF life and pre-exposed time.

Detection of Repair of the Zone of Calcified Cartilage with Osteoarthritis through Mesenchymal Stem Cells by Ultrashort Echo Time Magnetic Resonance Imaging

Objective：Currently,magnetic resonance imaging （MRI） is the most commonly used imaging modality for observing the growth and development of mesenchymal stem cells （MSCs） after in vivo transplantation to treat osteoarthritis （OA）.However,it is a challenge to accurately monitor the treatment effects of MSCs in the zone of calcified cartilage （ZCC） with OA.This is especially true in the physiological and biochemical views that are not accurately detected by MRI contrast agents.In contrast,ultrashort time echo （UTE） MRI has been shown to be sensitive to the presence of the ZCC,creating the potential for more effectively observing the repair of the ZCC in OA by MSCs.A special focus is given to the outlook of the use ofUTE MRI to detect repair of the ZCC with OA through MSCs.The limitations of the current techniques for clinical applications and future directions are also discussed.Data Sources：Using the combined keywords：＂osteoarthritis＂,＂mesenchymal stem cells＂,＂calcified cartilage＂,and ＂magnetic resonance imaging＂,the PubMed/MEDLINE literature search was conducted up to June 1,2017.Study Selection：A total of 132 published articles were initially identified citations.Of the 132 articles,48 articles were selected after further detailed review.This study referred to all the important English literature in full.Results：In contrast,UTE MRI has been shown to be sensitive to the presence of the ZCC,creating the potential for more effectively observing the repair of the ZCC in OA by MSCs.Conclusions：The current studies showed that the ZCC could be described in terms of its histomorphology and biochemistry by UTE MRI.We prospected that UTE MRI has been shown the potential for more effectively observing the repair of the ZCC in OA by MSCs in vivo.

Fatigue behavior of uncoated and MCrAlY-coated DS nickelbased superalloys pre-exposed in hot corrosion condition

The effects of a MCrAlY coating on low-cycle fatigue(LCF) behavior of directionally solidified(DS)nickle-based superalloy DZ125 were investigated. Before the fatigue testings, the specimens were pre-exposed in high-temperature hot corrosion(HTHC) environment generating by a burner rig at 850 ℃. The results show that the coating in hot corrosion condition has beneficial effects on the fatigue resistance of superalloy. Under corrosion condition, the MCrAlY-coated specimens tested have higher fatigue lives than the uncoated specimens at the same stress level. The coating failure results from fatigue process and numerous fatigue cracks were nucleated at the specimen surface, only one main crack propagates inward and the secondary cracks away from the fracture surface are perpendicular to the loading orientation.

High-temperature oxidation behavior of DZ125 Ni-based superalloy under tensile stress

The key in antioxidant capacity of aero-engine hot components is the protective oxide scales.Many factors can affect the performance of oxide scales.The effect of tensile stress on high-temperature oxidation behavior of directionally solidified DZ125 Ni-based superalloy was investigated by thermogravimetric analysis(TGA).Tensile samples were subjected to stress of 100 MPa,and the oxidation behavior was studied at 980℃in air.The surface and cross-sectional morphologies of the oxidized coating were analyzed by scanning electron microscope(SEM).The influence of tensile stress on the oxidation behavior of directionally solidified DZ125 Ni-based superalloy at high temperature was discussed.Results show that an applied tensile stress generally leads to larger Cr/Ni mass ratio in the oxide scales,greater overall chromium depletion values directly under the oxide scales,lower specific weight gain values and thinner oxide scales.These factors are attributed to the formation of fast diffusion paths for Cr atoms to diffuse to the surface under tensile stress,thus causing a reduction in the duration of the less protective transient oxidation period and promoting a faster formation of the protective Cr_(2)O_(3)layer.

Oxidation-induced damage of an uncoated and coated nickel-based superalloy under simulated gas environment

Turbine blades and vans operated in an aggressive gas environment usually suffer from combined oxidation and cycle loading effects. The surface oxide layer will result in premature failure and lead to a significant reduction in the service lifetime. The effects of prior oxidation-induced damage under a simulated combustion-gas environment on the fatigue lifetime of the directionally solidified（DS） nickel-based superalloy DZ125 with and without an oxidation-resistant coating were presented. The fatigue lifetime of uncoated samples is adversely affected by prior oxidation exposure. The deterioration of fatigue lifetime in uncoated samples is associated with surface microstructural degradation, which occurs during prior exposure. However,the presence of MCrAlY coating is beneficial for the sample＇s lifetime under high stress. Further scanning electron microscopy（SEM） analysis demonstrates that the coating does not contribute to the initiation mode of fatigue cracks.

Tensile properties and failure analysis of Ti–6Al–4V joints by electron beam welding

The microstructural and mechanical characterization of electron beam welded joints of forged Ti-6Al- 4V were investigated. Microhardness tests indicate that the hardness of the fusion zone （FZ） is higher than that of the heat-affected zone （HAZ） and base metal. The tensile results show that the mechanical properties of the welded joints are comparable with those of the base metal in terms of static strength and are in accordance with the relationship between microstructure and mechanical properties of welded joints. The ultimate tensile strength of the weld is equal to that of the hourglass joint, which indicates that the mechanical properties of the longitudinal FZ and those of the transverse FZ are the same. Macromechanical behavior and macrofracture and microfracture of the base material, joint, and weld specimens are observed. A comparison among the three types of specimen fracture phenomena reveals the following distinctive differences： （1） the fracture mode, （2） the micrograph of the dimple pattern at the central region, and （3） the size of the dimple at the central region and the transition region.

Microstructural evolution and restoration of creep property for a damaged K403 alloy after rejuvenation heat treatments

Rejuvenation heat treatments can restore the microstructures and mechanical properties of the degraded turbine blades in gas turbine engines.Herein we analyze the effects of rejuvenation heat treatments on the microstructural characteristics and mechanical properties of damaged and undamaged specimens of a Ni-based superalloy,K403.The damaged specimens were found to have degraded microstructures and shorter creep lifetime than the undamaged specimen.The rejuvenation heat treatment proved beneficial,especially for specimens exposed to damage for 50 h.In addition,the microstructure recovery and creep life were found to depend on the predamage durations of the specimens.A y’-precipitate-based creep lifetime model was established to predict the residual lifetime based on the microstructural information.

Fatigue crack growth of titanium alloy joints by electron beam welding

Electron beam welding（EBW） has been widely used in the manufacture of titanium alloy welded blisk for aircraft engines. Based on fatigue crack growth tests on titanium alloy electron beam welding（EBW） joints, mechanism of fracture was investigated under scanning electron microscope（SEM）. The results show that fatigue crack growth rate increases as the experimental load increases under the same stress ratio and stress intensity factor range. At the beginning of crack growth, the extension mechanism of fatigue crack is the typical mechanism of cleavage fracture. In the steady extention stage, crack extends along the weld seam firstly.Then, crack growth direction changes to extend along the base metal. The extension mechanism of fatigue crack in the weld seam is the main mechanism of cleavage fracture and the extension mechanism of fatigue crack in the base metal is the main extension mechanism of fatigue band. In the instantaneous fracture stage, the extension mechanism of fatigue crack is the typical dimple-type static fracture mechanism.Crack growth was simulated by conventional finite element method and extended finite element method.