Evaluation of Through-Thickness Residual Stresses by Neutron Diffraction and Finite-Element Method in Thick Weld Plates

Jiang, Wenchun,Woo, Wanchuck,Wan, Yu,Luo, Yun,Xie, Xuefang,Tu, S. T. ASME International 2017 Journal of Pressure Vessel Technology Vol.139 No.3

Effect of Temperature Fluctuation on Creep and Failure Probability for Planar Solid Oxide Fuel Cell

Jiang, Wenchun,Luo, Yun,Zhang, Weiya,Woo, Wanchuck,Tu, S. T. ASME 2015 Journal of fuel cell science and technology Vol.12 No.5

Using heat sink technology to decrease residual stress in 316L stainless steel welding joint: Finite element simulation

Jiang, Wenchun,Zhang, Yucai,Woo, Wanchuck Elsevier 2012 The International journal of pressure vessels and Vol.92 No.-

<P><B>Abstract</B></P><P>316L type stainless steel is widely used in chemical industries due to its excellent resistance to corrosion. But the welding residual stresses have a great effect on stress corrosion cracking. This paper used finite element method to study the effect of heat sink on residual stress. The effects of contact length and the average heat transfer coefficient on residual stress have been investigated. It is found that the heat sink technology can decrease the residual stress greatly. Compared to the model without heat sink, 20% of the peak longitudinal stress has been reduced. The heat sink decreases the dwell time during cooling from 850 °C to 400 °C, which is helpful to decrease the risk of sensitization of 316L stainless steel. With the contact length increase, the transverse stress is decreased. Further increase of the contact length has no positive effect on reducing the longitudinal stress. With the average heat transfer coefficient increase, the transverse stress is decreased greatly while the longitudinal stress decreases slightly, and some tensile residual stresses have been changed to compressive in some zone.</P> <P><B>Highlights</B></P><P>► Heat sink decreases the residual stress and increases the cooling rate. ► The heat sink decreases the dwell time during the cooling from 850 to 400 °C. ► With the contact length increases, residual stresses are decreased. ► With the heat transfer coefficient increases, residual stresses are decreased.</P>

Comparison of Brazed Residual Stress and Thermal Deformation between X-Type and Pyramidal Lattice Truss Sandwich Structure: Neutron Diffraction Measurement and Simulation Study

Jiang, Wenchun,Wei, Zhiquan,Luo, Yun,Zhang, Weiya,Woo, Wanchuck De Gruyter 2016 High temperature materials and processes Vol.35 No.6

<P><B>Abstract</B></P><P>This paper uses finite element method and neutron diffraction measurement to study the residual stress in lattice truss sandwich structure. A comparison of residual stress and thermal deformation between X-type and pyramidal lattice truss sandwich structure has been carried out. The residual stresses are concentrated in the middle joint and then decreases gradually to both the ends. The residual stresses in the X-type lattice truss sandwich structure are smaller than those in pyramidal structure. The maximum longitudinal and transverse stresses of pyramidal structure are 220 and 202 MPa, respectively, but they decrease to 190 and 145 MPa for X-type lattice truss sandwich structure, respectively. The thermal deformation for lattice truss sandwich panel structure is of wave shape. The X-type has a better resistance to thermal deformation than pyramidal lattice truss sandwich structure. The maximum wave deformation of pyramidal structure (0.02 mm) is about twice as that of X-type (0.01 mm) at the same brazing condition.</P>

Compression, Shear and Bending Performance of X-type Lattice Truss Panel Structure by Theoretical Method and Simulation

Qian Zhang,Wenchun Jiang,Yanting Zhang,Shan-Tung Tu 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.1

X-type lattice truss panel structure (LTPS) with high strength-weight ratio has anisotropic mechanical properties. This paper proposes a theoretical mechanical model to give predictions of the compression, shear and bending performance of LTPS including the eff ective compressive/shearing modulus, eff ective compressive/shearing strength and failure loads under threepoint bending. These properties are expressed as analytical expressions involving all of the geometrical parameters. The numerical simulation is also performed, and the eff ects of the geometrical parameters are discussed. The results show that the predicted eff ective modulus and strength by the theoretical method agree well with the simulated results. The eff ective shear modulus in 23-direction is obviously higher than that in other directions. The geometrical parameters have signifi cant eff ects on the mechanical properties. The shear yielding strength increases with the increase of truss width and thickness, while it decreases with the increase of truss length and platform length. The truss thickness has the greatest eff ect on yielding strength, followed by the truss width and the truss length. The changes of the yielding strength with the increase of the angle from horizontal and defl ected angle are not monotonic. The failure loads of three-point bending by face sheets yielding and shear induced core collapse decrease, when the span increases. The proposed analytical expressions are available to the engineering application and more complicated calculations of structures made of X-type cores.

Effect of notch position on creep damage for brazed joint

Luo, Yun,Jiang, Wenchun,Zhang, Qian,Zhang, Weiya,Woo, Wanchuck,Tu, Shan-Tung,Hao, Muming Elsevier Applied Science 2016 Advances in engineering software Vol.100 No.-

<P><B>Abstract</B></P> <P>In this paper, we investigated the effect of notch position on creep damage for Hastelloy C276-BNi2 brazed joint. Three different types of notches locate in edge of base metal (base notch), edge of filler metal (surface notch) and center of filler metal (inside notch) were compared, and the influence of notch geometric parameters on creep damage was also investigated. The results show that the different notch position and dimension generate different creep damage distributions and have a great influence on creep life. The creep failure is the easiest to occur in surface notch, then the base notch, and the last is inside notch. The brazed joint with higher maximum principal stress and von Mises stress generates creep failure easier. For the base notch, the failure time increases with the increase of base notch distance and the creep failure location moves gradually from the center of filler metal to notch tip. The notch locating away from filler metal is beneficial to reduce the creep damage in filler metal and enhance the creep life. For the inside notch, the failure time decreases with notch length increases and the maximum creep damage locates at notch tip. With the increase of inside notch width, the failure time increases first and then keep steadiness, and the failure location moves away from notch tip. The effects of notch position and dimension should be fully considered in creep failure analyses and life assessments of brazed joints.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The creep failure is easy generate in surface notch. </LI> <LI> The far away notch is helpful to reduce the creep damage of filler metal. </LI> <LI> As H increases, the failure location moves from filler metal to base metal. </LI> <LI> As H increases, the failure time increases first then keeps stable. </LI> <LI> The failure time decreases with L increases while it increases with W increases. </LI> </UL> </P>

SP0454, A Putative Threonine Dehydratase, Is Required For Pneumococcal Virulence In Mice

WenJuan Yan,Hong Wang,WenChun Xu,KaiFeng Wu,Run Yao,XiuYu Xu,Jie Dong,YanQing Zhang,Wen Zhong,XueMei Zhang 한국미생물학회 2012 The journal of microbiology Vol.50 No.3

Increasing pressure in antibiotic resistance and the requirement for the design of new vaccines are the objectives of clarifying the putative virulence factors in pneumococcal infection. In this study, the putative threonine dehydratase sp0454 was inactivated by erythromycin-resistance cassette replacement in Streptococcus pneumoniae CMCC 31203 strain. The sp0454 mutant was tested for cell growth, adherence, colonization, and virulence in a murine model. The Δsp0454 mutant showed decreased ability for colonization and impaired ability to adhere to A549 cells. However, the SP0454 polypeptide or its antiserum did not affect pneumococcal CMCC 31203 adhesion to A549 cells. The sp0454 deletion mutant was less virulent in a murine intranasal infection model. Real-time RT-PCR analysis revealed significant decrease of the pneumococcal surface antigen A expression in the sp0454 mutant. These results suggest that SP0454 contributes to virulence and colonization, which could be explained in part by modulating the expression of other virulence factors, such as psaA in pneumococcal infection.

Diagnostics of ablation plasma induced by high intensity pulsed ion beam using temporally resolved emission spectroscopy

jialiang Zhang,Wang Wenchun,Ma Tengcai,chang Tan,younian Wang 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III

This paper presents the research on the optical emission spectra (OES) of the secondary plasma formed on the surface of a polyethylene target by high intensity pulsed ion beams (HIPIB) produced in the TEMP-II accelerator of our laboratory. It can be veried from the OES that the secondary plasma is mainly composed of H, C, C2and CH species. The temporal proles of some spectral lines of the species, recorded by a SP305 spectrometer with a TEKTRONIX TDS3052 500 MHz storage oscilloscope, are investigated under the typical running conditions of the TEMP-II. The average standing time of the secondary plasma is evaluated from the 30 s temporal proles when the HIPIB has a energy density of 4 J/cm2 and a duration of 75 ns. The forming time of the secondary plasma is also about 30 s, which equals to the average delay of the spectral emission pulses relative to the trigger pulse of the HIPIBs.

Residual Stress Distribution in Hard-Facing of Pressure Relief Valve Seat

Ai, Li,Yu, Xinhai,Jiang, Wenchun,Woo, Wanchuck,Ze, Xiaofeng,Tu, Shan-Tung AMERICAN SOCIETY MECHANICAL ENGINEERS 2014 Journal of Pressure Vessel Technology Vol.136 No.6

<P>In this study, for the hard-facing of spring-loaded pressure relief valve seats, the residual stress distributions after the tungsten inert gas welding, (TIG) postwelded heat treatment and subsequent surface turning were investigated. The heat input parameters of welding were calibrated using an infrared imaging and thermocouples. The residual stress distributions were computed using three-dimensional finite element model. The neutron diffraction approach was employed to verify the finite element calculation. It is found that, the surface temperature during hard-facing welding shows a double ellipsoidal shape with the highest value of around 1570 degrees C. The high residual stress zones are located exactly under the welded joint except a slight deviation in the hoop direction. The magnitudes of tensile residual stresses in the three directions increase with their corresponding locations from the root of the joint into the base metal. The residual stresses in all of the three directions decrease significantly after the heat treatment. After surface turning, the residual stresses are tensile except for those close to the inner surface that are compressive in axial and radial directions.</P>

Pneumococcal wall teichoic acid is required for the pathogenesis of Streptococcus pneumoniae in murine models

Hongmei Xu,Libin Wang,Jian Huang,YanQing Zhang,Feng Ma,Jianmin Wang,WenChun Xu,XueMei Zhang,YiBing Yin,KaiFeng Wu 한국미생물학회 2015 The journal of microbiology Vol.53 No.2

Pneumococcal asymptomatic colonization of the respiratory tracts is a major risk for invasive pneumococcal disease. We have previously shown that pneumococcal wall teichoic acid (WTA) was involved in pneumococcal infection of sepsis and adherence to epithelial and endothelial cells. In this study, we investigated the contribution of pneumococcal WTA to bacterial colonization and dissemination in murine models. The result showed that nasopharynx colonizing D39 bacterial cells have a distinct phenotype showing an increased exposure of teichoic acids relative to medium-grown bacteria. The WTA-deficient mutants were impaired in their colonization to the nasopharynx and lungs, and led to a mild inflammation in the lungs at 36 h post-inoculation. Pretreatment of the murine nares with WTA reduced the ability of wild type D39 bacteria to colonize the nasopharynx. In addition, the WTA-deficient strain was impaired in its ability to invade the blood and brain following intranasal administration. WTA-deficient D39 strain was reduced in C3 deposition but was more susceptible to the killing by the neutrophils as compared with its parent strain. Our results also demonstrated that the WTA enhanced pneumococcal colonization and dissemination independently of the host strains. These results indicate that WTA plays an important role in pneumococcal pathogenesis, both in colonization and dissemination processes.