Low cycle fatigue behavior of zirconium−titanium−steel composite plate

The low cycle fatigue behavior of zirconium−titanium−steel composite plate under symmetrical and asymmetric stress control was studied.The effects of mean stress and stress amplitude on cyclic deformation,ratcheting effect and damage mechanism were discussed in detail.The results show that under symmetric stress control,the forward ratcheting deformation is observed.Under asymmetric stress control,the ratcheting strain increases rapidly with mean stress and stress amplitude increasing.Under high stress amplitude,the influence of mean stress is more significant.In addition,by studying the variation of strain energy density,it is found that the stress amplitude mainly promotes the fatigue damage,while the mean stress leads to the ratcheting damage.In addition,fractographic observation shows that the crack initiates in the brittle metal compound at the interface,and the steel has higher resistance to crack propagation.Finally,the accuracy of life prediction model considering ratcheting effect is discussed in detail,and a high-precision life prediction model directly based on mean stress and stress amplitude is proposed.

Spontaneous pneumomediastinum in an elderly COVID-19 patient:A case report

BACKGROUND Spontaneous pneumomediastinum(SPM)is more common in young adults,usually caused by external factors like trauma.It causes symptoms such as chest pain or dyspnea,but it is rare to see elderly patients who develop SPM.Here we report the case of an elderly patient diagnosed with coronavirus disease 2019(COVID-19)who neither got mechanical ventilation nor had chest trauma but were found to develop SPM for unknown reason.CASE SUMMARY A 62-year-old man complained of a 14-d history of fever accompanied by dry cough,shortness of breath,wheezing,myalgia,nausea,and vomiting.Real-time fluorescence polymerase chain reaction confirmed the diagnosis of COVID-19.The patient was treated with supplementary oxygen by nasal cannula and gamma globulin.Other symptomatic treatments included antibacterial and antiviral treatments.On day 4 of hospitalization,he reported sudden onset of dyspnea.On day 6,he was somnolent.On day 12,the patient reported worsening right-sided chest pain which eventually progressed to bilateral chest pain.He was diagnosed with SPM,with no clear trigger found.Conservative treatment was administrated.During follow-up,the pneumomediastinum had resolved and the patient recovered without other complications.CONCLUSION We presume that aging lung changes and bronchopulmonary infection play an important part in the onset of SPM in COVID-19,but severe acute respiratory syndrome may represent a separate pathophysiologic mechanism forpneumomediastinum.Although the incidence of SPM in elderly patients is low,clinicians should be alert to the possibility of SPM in those infected with severe acute respiratory syndrome coronavirus 2 for life-threatening complications such as cardiorespiratory arrest may occur.

Regulatory polymorphism of CXCL10 rs1439490 in seronegative occult hepatitis C virus infection

AIM To examine the relationship between the single nucleotide polymorphism CXCL10 rs1439490 and seronegative occult hepatitis C virus(HCV) infection(OCI).METHODS One hundred and three cases of seronegative OCI and 155 cases of seropositive chronic HCV infection(CHC) were diagnosed at five Liver Centers in Northeastern China, from 2012 to 2016. CXCL10 rs1439490, rs1440802, and IL-28 B rs12979860 were analyzed by sequencing. Serum CXCL10 was measured by ELISA. Intrahepatic CXCL10 was determined by quantitative PCR and immunohistochemical semi-quantitative scoring. Liver necroinflammation and fibrosis were scored according to the METAVIR system.RESULTS CXCL10 rs1439490 G/G was more prevalent in OCI patients(n = 93/103; 90.3%) than in CHC patients(n = 116/155; 74.8%; P = 0.008). OCI patients had lower serum CXCL10 levels than CHC patients(192.91 ± 46.50 pg/mL vs 354.78 ± 102.91 pg/mL, P < 0.0001). Of IL-28 B rs12979860 C/C patients, OCI patients with rs1439490 G/G had lower serum and liver levels of CXCL10 and lower levels of liver necroinflammation and fibrosis than non-G/G patients. OCI patients had higher alanine aminotransferase normalization rates after Peginterferon treatment than CHC patients(P < 0.05) and serum CXCL10 decreased significantly(P < 0.0001). Liver necroinflammation and fibrosis were alleviated in 8 OCI patients after treatment. Multivariate analysis indicated that rs1439490 G/G significantly influenced the occurrence of OCI in HCV infection(OR = 0.31, 95%CI: 0.15-0.66, P = 0.002).CONCLUSION CXCL10 rs1439490 G/G is positively associated with OCI in HCV infection and antiviral outcome.

Atypical adult-onset Still’s disease with an initial and sole manifestation of liver injury: A case report and review of literature

BACKGROUND Adult-onset Still's disease(AOSD)typically presents with a high spiking fever,polyarthritis,transient maculopapular rash,neutrophilic leukocytosis,and hepatosplenomegaly.It has a wide spectrum of clinical symptoms ranging from mild to severe,with extensive involvement of almost every organ.Although liver involvement in the form of increased hepatic enzymes and bilirubin is common,no AOSD case with liver involvement as the initial manifestation of AOSD has been reported.CASE SUMMARY A 35-year-old woman presented to the hepatology department with progressively worsening jaundice for one week.Liver chemistry tests revealed a significantly increased liver enzymes and bilirubin level.Given that the clinical examination was unremarkable,liver biopsy was considered because the patient had a history of AOSD 6 years ago.Liver histopathology revealed that most hepatic lobules were still recognizable.Fusional necrosis was observed around most central veins.A few bridging necrotic zones were also found.Infiltration of multiple plasma cells were observed in the necrotic zone,and the reticular scaffold was still expanded.Additionally,no obvious fibrosis was observed in the portal area.Mild mixed inflammatory cell infiltration was noted in the interstitium of the portal area.Further examination was unremarkable except for a remarkably high level of ferritin.Collectively,a presumptive diagnosis of liver injury secondary to AOSD was made.The hepatic involvement responded well to glucocorticoid treatment.CONCLUSION This case highlights that hepatic involvement as an initial and sole manifestation could be a pattern of relapsed AOSD.The diagnosis of AOSD should be considered in the case of nonresolving liver injury after the exclusion of common etiologies for liver diseases.A liver biopsy can be useful for the differential diagnosis of liver injury associated with AOSD.

Orientation and strain rate dependent tensile behavior of single crystal titanium nanowires by molecular dynamics simulations

Molecular dynamics simulation was employed to study the tensile behavior of single crystal titanium nanowires（NWs）with[112^-0],[1^-100] and[0001]orientations at different strain rates from 10^8s^-1 to 10^11s^-1.When strain rates are above 10^10s^-1,the state transformation from HCP structure to amorphous state leads to super plasticity of Ti NWs,which is similar to FCC NWs.When strain rates are below 10^10s^-1,deformation mechanisms of Ti NWs show strong dependence on orientation.For [112^-0] orientated NW.{101^-1} compression twins（CTs）and the frequently activated transformation between CTs and deformation faults lead to higher plasticity than the other two orientated NWs.Besides,tensile deformation process along [112^-0] orientation is insensitive to strain rate.For [1^-100] orientated NW,prismaticslip is the main deformation mode at 10^8s^-1.As the strain rate increases,more types of dislocations are activated during plastic deformation process.For[0001]orientated NW,{101^-2} extension twinning is the main deformation mechanism,inducing the yield stress of [0001] orientated NW,which has the highest strain rate sensitivity.The number of initial nucleated twins increases while the saturation twin volume fraction decreases nonlinearly with increasing strain rate.

Temperature-Dependent SRS Behavior of 316L and Its Constitutive Model

The strain rate sensitivity（SRS）and temperature sensitivity（TS）of 316L austenitic stainless steel were investigated by constant strain rate test（CSRT）and strain rate jump test（SRJT）under four temperatures（293,373,473 and 573 K）and four strain rates（5 ×10^-4/s,1 × 10^-3/s,5 × 10^-3/s and 1 × 10^-2/s）.The results show that temperature sensitivity（TS）indexes at different strain rates are coincidence to be negative,related to temperature softening.On the contrary,SRS indexes change from positive to negative with the increase in temperature associated with dynamic strain aging（DSA）.Moreover,based on the comparison between CSRT and SRJT,SRS and TS indexes obtained by two methods agree well.It proves that the SRJT can describe the SRS and TS phenomenon of 316L efficiently.Furthermore,the effects of tem-perature and strain rate on fracture mechanism were discussed.At last,an improved Johnson-Cook model was proposed to consider the temperature-dependent SRS behavior of 316L.

Experimental characterization of anisotropic tensile mechanical behavior of pure titanium tube

The anisotropic tensile mechanical properties of pure titanium(TA2)tubes were studied by means of theoretical analysis,finite element simulation and tensile tests.Based on the stress analysis of circumferential tensile of TA2 tube,an equation for calculating the tangential force of circumferential tensile specimen was established,and the relationship among tangential force,friction and position of ring specimen was analyzed.The finite element simulation analysis of circumferential tensile process of TA2 ring specimen was carried out,which verified the tangential force equation derived from theoretical analysis.The effect of gauge length and friction on necking and tensile load was analyzed,and the optimal gauge length was selected for the ring hoop tensile test.Finally,the axial and circumferential tensile digital image correlation experiments were carried out to verify the theoretical and finite element simulation results.The friction coefficient between TA2 tube and D-blocks(using Teflon lubricant)was determined by the inverse finite element method and the friction experiment,and the true stress-strain curve of TA2 tube was obtained.The results show that the axial and circumfere ntial mechanical behaviors of TA2 tubes are significantly different and an isotropic.

Effect of isothermal temper embrittlement and subsequent hydrogen embrittlement on tensile properties of 2.25Cr-1Mo-0.25V base metal and welded metal

2.25Cr–1Mo–0.25V base metal(BM)and welded metal(WM)with different temper embrittlement states were obtained by isothermal temper embrittlement test.The ductile–brittle transition temperature and the carbide size of temper embrittled 2.25Cr–1Mo–0.25V BM and WM increased with the isothermal tempering time.The increase in temper embrittlement time leads to a decrease in yield strength(YS)and ultimate tensile strength(UTS).Hydrogen embrittlement(HE)can decrease the ductility and increase YS and UTS of the material.The hydrogen embrittlement sensitivity and microstructure analysis both show a combined effect of HE and temper embrittlement.The deeper the temper embrittlement,the more sensitive the material to HE.When the hydrogen content in the material is low,the WM is less susceptible to HE due to its welding defects.