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31.
Creep behavior of crack in dissimilar materials is studied using steady-state C* path independent integral and ABAQUS finite element code. The specific geometry involves an edge crack parallel to the interface of a bi-material tensile specimen at high temperature. Under extensive creep, the C* value for the bi-material specimen can be significantly higher than that for the homogeneous specimen. For small-scale creep material mismatch has little influence on the transient integral designated by Ct. The integral parameters C* or Ct are shown to depend on the inhomogeneity of the system and cannot characterize the creep behavior of cracks.The approach is extended to creep crack growth in a welded compact tension specimen. Modification factors are introduced for different crack and weld interface geometries. 相似文献
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33.
Evaluation of thermophysical characteristics on shape-stabilized paraffin as a solid-liquid phase change material 总被引:1,自引:0,他引:1
This report deals with thermophysical properties and measuring methods of shape-stabilized paraffin as a new type of latent heat storage material, which keeps the same shape in a solid state when the paraffin melts. Therefore, this type paraffin can be used in a latent heat storage system without encapsulation. A transient hot wire method, a differential scanning calorimeter (DSC), a water calorimeter and a volume expansion meter, which were developed in the present study, were used to measure effective thermal conductivity, latent heat, specific heat and density of the shape-stabilized paraffin, respectively. From the obtained data, useful correlation equations of the above-mentioned thermophysical properties of the shape-stabilized paraffin were expressed as functions of physical property and mass fraction of each constituent of the shape-stabilized paraffin. 相似文献
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35.
本文分析了象差函数对光学传递函数的性态影响,指出在用白光主观散斑法测量曲面变形时,由于成象系统不能对曲面上各点同时对焦,各物点有不同程度的离焦,而造成光学传递函数对频率响应的下降,有效截止频率的降低,从而影响其测量灵敏度的提高。 相似文献
36.
This paper investigates mixed free and forced convection of non-Newtonian fluids from a vertical isothermal plate embedded
in a homogenous porous medium. A mathematical model is developed based on the modified Darcy's law and boundary-layer approximations,
and the exact similarity solution is obtained as well as an integral solution. These two solutions agree within 3% for aiding
flows and 10% for opposing flows. It is found that, non-Newtonian characteristics of fluids have appreciable influences on
velocity profiles, temperature distributions and flow regimes. 相似文献
37.
本文对钢丝帘线/橡胶复合材料中的钢丝帘线泊松比的定义提出了新的见解,建议用钢丝帘线横截面变化率代替其横向应变,并提出了利用扫描电子显微镜测定截面变化率的实验方法 相似文献
38.
A method for characterizing texture from measurements of ultrasonic wave velocities is proposed. In polycrystalline aggregates, ultrasonic wave velocities are strongly affected by orientation distribution coefficients (ODCs), which are usually used to describe the degree of preferred grain orientation in textured materials. In this work, velocities of longitudinal and transverse waves propagating into aluminum alloy 6061 were measured under pure shear, simple shear and uniaxial tension. From the measured ultrasonic wave velocities, the ODCs W400 and W420 were calculated to infer the deformation-induced texture. The predicted pole figures, obtained using ultrasonic velocities, were in good qualitative agreement with the finite element polycrystal model analyzed pole figures. 相似文献
39.
超低间隙钛合金低温动态力学性能 总被引:1,自引:0,他引:1
本文利用实验应变模态分析方法,在低温条件下(液氦到室温)研究了航天材料超低间隙钛合金TA7-D试样的动态力学性能,使用时域系统识别技术分析了材料在不同温度点的模态参数,并根据基频给出了其动态模量随温度的变化。 相似文献
40.
A new star-shaped molecule StOF-Br_3 containing oligofluorenes and halogen atoms(Bromine) has been synthesized and studied by Scanning Tunneling Microscopy(STM) at the highly oriented pyrolytic graphite(HOPG) surface.We have obtained the high-resolution self-assembled STM images,from which the highly ordered and closely packed non-porous arrangements of the StOF-Br_3 molecular selfassemblies at the heptanoic acid/HOPG surface could be observed.The molecular models and selfassembled StOF-Br_3 architectures have been given in the following text.Besides,we have also figured out the surface free energy by the density functional theory(DFT) calculation,which proved that the halogen...halogen interaction was strong enough to stabilize the ordered molecular self-assemblies.This work verifies the existence of bromine...bromine interactions,and meanwhile provides a kind of effective approach for quickly building ordered molecular nanoarchitectures with large areas and different geometries. 相似文献