H.-M. Huang
,
J. Pan and S. C. Tang 1) Mechanical Engineering and Applied Mechanics
,
The University of Michigan Ann Arbor
,
MI 48109
,
USA 2) Ford Research Laboratory
,
Ford Motor Company Dearborn
,
MI 48121
,
USA
金属学报(英文版)
An approximate macroscopic yield criterion for anisotropic porous sheet metals is adopted in a failure prediction methodology that can be used to investigate the failure of sheet metals under forming operations. This failure prediction methodology is developed based on the Marciniak-Kuczynski approach by assuming a slightly higher void volume fraction inside randomly oriented imperfecte analysis. Here, a nonproportional deformation history including relative rotation of principal stretch directions is identified in a selected critical element of an aluminum sheet from a FEM fender forming simulation. Based on the failure prediction methodology, the failure of the critical sheet element is investigated under the non-proportional deformation history. The results show that thiven non-proportional deformation history.
关键词:
sheet metal forming
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null
,
null
,
null
Journal of Physics D-Applied Physics
The dynamic aspects of linear elastic fracture mechanics applied to dielectric breakdown are studied. In the same direction as the fracture mechanics analogue for dielectric breakdown described previously by some researchers, this paper develops the intrinsic, rate-dependent bond breakdown micromechanism to account for the dynamic process of dielectric breakdown. The formulae of conducting microcrack growth rate and lifetime prediction are derived and applied to the experimental data of SiO2 films.
关键词:
sio2-films;oxides
GUO Chengbi ZHOU Weisheng Dalian Institute of Technology
,
Dalian
,
Liaoning
,
China Professor
,
Dept.of Shipbuilding
,
Dalian Institute of Technology
,
Dalian
,
Liaoning
,
China
金属学报(英文版)
The in-phase and out-of-phase thermal fatigue,the C-P type and P-C type isothermal fa- tigue of grey cast iron were experimentally studied.The fatigue life was evaluated analytically by using the elastic-plastic fracture mechanics method(mainly J integral).The results of ex- periments and calculations showed that the lifes of in-phase and C-P type fatigue are longer than that of out-of-phase and P-C type fatigue respectively within the same strain range. This is in contrast to the results of other materials such as low carbon steel.On the other hand, the predicted lifes are consistent with experimental results.This suggests that J integral as a mechanics parameter for characterizing the thermal fatigue strength of grey cast iron and the mechanics model and the calculation method developed here are efficient.A parameter ΔW_1 was proposed from energy aspect to characterize the capacity of crack propagation. The isothermal fatigue life is the same as the thermal fatigue life for identical ΔW_1 values.
关键词:
grey cast iron
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null
,
null
F.Q.Tian
金属学报(英文版)
Welded joint is a mechanical heterogeneous body, and mechanical heterogeneity has great effect on dynamic fracture behaviour of welded joints. In the present investigation, dynamic response curve and dynamic J-integral of practical undermatched welded joint and whole base and whole weld three-point-bend (TPB) models containing longitudinal crack are computed. Dynamic J-integral is evaluated using virtual crack extension (VCE) method and the computation is performed using MARC finite element code. Because of the effect of inertia,dynamic load response curve of computed model waves periodically. Dynamic J-integral evaluated by VCE method is path independent. The effect of inertia has little influence on dynamic J-integral curve. The value of dynamic J-integral of undermatched welded joint is lower than that of whole base metal and higher than that of whole weld metal. The results establish the foundation of safety evaluation for dynamic loaded welded structures.
关键词:
virtual crack extension
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null
,
null
Mehdi Ebrahimian-Hosseinabadi Fakhredin Ashrafizadeh Mohammadreza Etemadifar Subbu S. Venkatraman
材料科学技术（英文）
In this paper, preparation of nano-biphasic calcium phosphate (nBCP), mechanical behavior and load-bearing of poly (lactide-co-glycolide) (PLGA) and PLGA/nBCP are presented. The nBCP with composition of 63/37 (w/w) HA/β-TCP (hydroxyapatite/β-tricalcium phosphate) was produced by heating of bovine bone at 700°C. Composite scaffolds were made by using PLGA matrix and 10-50 wt% nBCP powders as reinforcement material. All scaffolds were prepared by thermally induced solid-liquid phase separation (TIPS) at -60°C under 4 Pa (0.04 mbar) vacuum. The results of elastic modulus testing were adjusted with Ishai-Cohen and Narkis models for rigid polymeric matrix and compared to each other. PLGA/nBCP scaffolds with 30 wt% nBCP showed the highest value of yield strength among the scaffolds. In addition, it was found that by increasing the nBCP in scaffolds to 50 wt%, the modulus of elasticity was highly enhanced. However, the optimum value of yield strength was obtained at 30 wt% nBCP, and the agglomeration of reinforcing particles at higher percentages caused a reduction in yield strength. It is clear that the elastic modulus of matrix has the significant role in elastic modulus of scaffolds, as also the size of the filler particles in the matrix.
关键词:
Scaffold
Journal of Physics D-Applied Physics
Magnetic properties of Sm-Fe(Ti)-C(N)/alpha-Fe nanocomposite alloys prepared by mechanical alloying (MA) have been studied. The hysteresis loops of MA Sm12Fe74Ti7C7Ndelta, Sm10Fe76Ti7C7Ndelta and Sm19.0Fe66.7C14.3 (i.e. Sm20Fe70C15) made by different processes (annealing, nitriding and re-milling) were measured at the applied magnetic fields with different dH/dt at 400, 350 and 295 K. The main phase with hard magnetic properties is of TbCu7-type. These three alloys have different behaviours of magnetization processes when the magnetic fields with dH/dt = 31.6 and 94.7 MA ms(-1) are applied. The magnetic viscosity S-v of Sm12Fe74Ti7C7Ndelta, Sm10Fe76Ti7C7Ndelta and Sm20Fe70C15 is determined from hysteresis loops measured for different dHIdt at various temperatures. The magnetic viscosity S-v in the Sm-Fe(Ti)-C(N)/alpha-Fe alloys is approximately proportional to the coercive field iH(c) at the measuring temperature.
关键词:
sm-fe;permanent-magnet;viscosity;powders
Materials Science & Engineering C-Biomimetic Materials Sensors and Systems
Bamboo, one of the strongest natural structural composite materials, has many distinguishing features. It has been found that its reinforcement unit, hollow, multilayered and spirally-wound bast fiber, plays an extremely important role in its mechanical behavior. In the present work, on the basis of the study on bamboo bast fiber and wood tracheid, a biomimetic model of the reinforcing element, composed of two layers of helically wound fiber, was suggested. To detect the structural characteristics of such a microstructure, four types of macro fiber specimens made of engineering composites were employed: axially aligned solid and hollow cylinders, and single- and double-helical hollow cylinders. These specimens were subjected to several possible loadings, and the experimental results reveal that only the double-helical structural unit possesses the optimum comprehensive mechanical properties. An interlaminar transition zone model imitating bamboo bast fiber was proposed and was verified by engineering composite materials. In our work, the transition zone can increase the interlaminar shear strength of the composite materials by about 15%. These biomimetic structural models can be applied in the design and manufacture of engineering composite materials.
关键词:
bamboo;bast fiber;biomimetics;engineering composites
Physics Letters A
We study the properties of the proton transfer in hydrogen-bonded molecule systems exposed in an externally applied fields in our model and give also the equations of motion of the protons and its corresponding soliton-solutions in such a case. Based on these results we calculate further the mobility and electric-conductivity of the proton transfer driven by an externally applied electric-field in the systems, which are about (9.2-9.7) x 10(-6) m(2)/V s and (1.47-1.55) x 10(-2) (Omegam)(-1) for the ice, respectively. This value for the mobility coincides quite with experimental result of (1-10) x 10(-2) cm(2)/V S. (C) 2004 Elsevier B.V. All rights reserved.
关键词:
molecular-systems;thermodynamic properties;dynamic properties;protein;molecules;soliton dynamics;chains;transport;model;scattering;quantum
Physica B-Condensed Matter
The structural, mechanical, thermodynamics properties and phase transition of FeVSb are investigated extensively using the first principle calculations and the quasi-harmonic Debye model. From the calculated elastic constants of cubic FeVSb, some other mechanical quantities, such as bulk modulus and Poisson's ratio, are drawn. Surprisingly, it is found that almost all these mechanical quantities are larger than those of CoVSb (Bo Kong et al., J. Alloys Compd. 509 (2011) 2611); the obtained corresponding transition pressure from fcc to hcp is also larger than that of CoVSb. For these distinctions, their complete different electronic and magnetic behaviors in their cubic structures may be responsible. However, in their hexagonal structures, atomic configurations are similar in terms of the analysis of both the ground-state structure and enthalpy-pressure curves. It is also shown that the elastic instability of cubic FeVSb does not appear with pressure upto 120 GPa and should not be a reason for the pressure-induced phase transition. In addition, heat capacity, Debye temperatures, and so on are obtained successfully for cubic FeVSb under the quasi-harmonic Debye model. Furthermore, we attempt to explore the phase diagram of FeVSb with the model. (C) 2011 Elsevier B.V. All rights reserved.
关键词:
FeVSb;Mechanical properties;Thermodynamics properties;Phase;transition;Generalized gradient approximation;semi-heusler compounds;ab-initio calculations;electronic-structure;elastic-constants;thermoelectric-materials;transport-properties;crystals;pressure;gap;instabilities
