EFFECT OF THE POISSON RATIO ON THE PERFECTLY PLASTIC STRESS FIELD AT A STATIONARY PLANE-STRAIN CRACK TIP

Under the condition that all the perfectly plastic stress components at a crack tip are the functions of ? only, making use of equilibrium equations and Von-Mises yield condition containing Poisson ratio, in this paper, we derive the generally analytical expressions of perfectly plastic stress field at a stationary plane-strain crack tip. Applying these generally analytical expressions to the concrete cracks, the analytical expressions of perfectly plastic stress fields at the stationary tips of Mode I, Mode II and Mixed-Mode I-II plane-strain cracks are obtained. These analytical expressions contain Poisson ratio.

PHYSICAL METALLURGY OF MULTISTAGE RSP Al-Li BASED ALLOYS

Bascd on serires authors study ofAl—Li alloys in recent years,the formation theory of powders,characteristics,powder compaction,the microstructures and the mechanical behaviors of RSP Al-Li based alloys analyzed and discussed in this paper.

HYDROSTATIC STRESS-DEPENDENT PERFECTLY-PLASTIC STRESS FIELDS AT A STATIONARY PLANE-STRESS CRACK-TIP

Under the condition that all the stress components at a crack-tip are the functions ofθonly,making use of equilibrium equations and hydrostatic stress-dependent yield condition,in this paper,we derive the generally analytical expressions of the hydrostatic stress-dependent perfectly-plastic stress fields at a stationary plane-stress crack-tip.Applying these generally analytical expressions to the concrete cracks,the analytical expressions of hydrostatic stress-dependent perfectly-plastic stress fields at the tips of mode I and mode II cracks are obtained.

SUPPLEMENTARY STUDY ON ANISOTROPIC PLASTIC STRESS FIELDS AT A STATIONARY PLANE-STRESS CRACK-TIP

Under the hypothesis that all the perfectly plastic stress components at a orach tip are the functions of θ only, making use of yield conditions and equilibrium equations. we derive the generally analytical expressions of the perfectly plastic stress field at a crack tip. Applying these generally analytical expressions to the concrete cracks, the analytical expressions of perfectly plastic stress fields at the tips of Mode Ⅰ Mode Ⅱ, Mode Ⅲ and Mixed Mode Ⅰ-Ⅱ cracks are obtained.

MASS TRANSFER AT GAS EVOLVING MERCURY ELECTRODE

Mass transfer at hydrogen evolving mercury electrode has been studied by determining mass transfer coefficients of indicator ions as the function of current density of hydrogen evolution for various kinds of indica tor ions in sulphuric acid solution.Mercury adhering to metal substrates of Ni,Cu or Ag is used as mercury electrode to overcome its trembling during the electrolysis.The effect of difTerent indicator ions,electrode character istic,substrate material,diameter of electrode and temperature is examined.It is found that the transfer coefficient is proportional to the mass square root of current density of hydrogen evolution.

Optimization and Calculation of the Al-Be-Si System

Lattice stability of Be is estimated,and interaction parameters for the liquids in the Al-Be and Be-Si systems are obtained using phase dia- gram data from literatures.Using the obtained parameters and the lattice stabilities of Al and Si given in the literatures,the Al-Be and Be-Si phase diagrams are calculated.By means of Kohler's for- mula the Gibbs energy for the liquid phase in the Al-Be-Si ternary system is extrapolated.The calcu- lation shows that no excess ternary term is necessa- ry for the thermodynamic description of the system. The liquidus projection,isothermal section at 1273 K,as well as vertical sections at 94 and 88 wt-% Al and 2 wt-% Be are calculated.The calcu- lated results are in reasonable agreement with the experimental data available.

A Study on Synthesis Kinetics of YBa_2Cu_3O_x High Tc Superconductor Powder

The synthesis kinetics of YBa_2Cu_30_x supercon- ductor was studied through comparing the calcina- tion (sintering) processes of different kinds of powders. It was shown that the temperature of synthesis of YBa_2Cu_30_x phase can be lowered from 950℃ to 800℃ through direct calcination of multiphase powder with uniform chemical com- position. The stress which is caused by the volume change during synthetic reaction breaks the particles. It facilitates the formation of highly active superfines of superconductor.

X-ray Diffraction Study of a Quasicrystalline Alloy Stable at High Temperature

Crystalline A1-Cu-Fe-Mg alloy powders were produced by means of rapid solidification.During annealing process,the quasicrystalline icosahedral phase formed at about 625°C and was stable until 900°C.This quasicrystalline phase is considered to be a stable one.The forming process of this phase was studied in detail.

Oxygen Potentials and Oxygen-potential Diagrams for Buffer Gas System at Normal Pressure

The principles of chemical equilibrium were used to derive a new set of formulae representing the oxygen potentials for five buffer gas mixtures at normal pressure.Various sorts of classical formulae for them are on- ly a particular representation under ignoring the effects of oxygen,thereby being unavailable for accurate cal- culation of oxygen potentials.In this paper,the oxygen potentials set by CO_2-H_2 gas mixtures and the mis- takes and errors of the classical expressions for them were discussed emphatically.The deviation in partial pressures of oxygen in some of previous experiments under the oxygen potentials controlled by CO_2-H_2 gas mixtures was explained quantitatively.The oxygen-potential diagrams predicting the equilibrated gas com- positions from the initial conditions have been also given.

Miscibility Gap in the Fe-Cu-Ni System at 1173 K

The isothermal section of the Fe-Cu-Ni ternary system at 1173 K was determined by microprobe analysis and diffusion triple technique. The experimental results show that this isothermal section only contains a miscibility gap region,and the maximal Ni content in the miscibility gap is 44.7 at.-%Ni.

ANISOTROPIC PLASTIC STRESS FIELD AT A MIXED-MODE CRACK TIP UNDER PLANE AND ANTI-PLANE STRAIN

On condition that the perfectly plastic stress component at a crack tip was a function of plane polar angle only, and made use of equilibrium equations, anisotropic plastic stress-strain-rate relations, compatibility equations and Hill anisotropic plastic yield condition, the generally analytical expressions of the anisotropic plastic stress field at a mixed-mode crack tip under plane and anti-plane strain were obtained. Applying these expressions to the mixed-mode cracks, the analytical expressions of anisotropic plastic stress fields at the tips of mixed-mode I-III, II-III and I-II-III cracks were derived.

AN APPROXIMATE ANALYTICAL SOLUTION OF THE LAMINAR BOUNDARY LAYER EQUATIONS

Using the pressure gradient as the new variable instead of. the ordinary longitudinal coordinate x, Liu transformed the ordinary laminar boundary equations into a new form. On this base Liu obtained the frictional stress factor by using the graphical method.In this paper the same variable replacement as in [1] is used and an approximate analytical solution of the laminar boundary layer equations by the series method is obtained. The author also obtains a formula of frictional stress factor. For the case of the main function without the term of constant, the author makes a further simplification. The error of the frictional stress factor obtained by the author is still less than 10%, compared with that of [1].

ANISOTROPIC PLASTIC FIELDS AT A RAPIDLY PROPAGATING PLANE-STRESS CRACK-TIP

Under the condition that all the stress components at a crack-tip are the functions of 0 only, making use of the equations of steady-state motion. Hill anisotropic yield condition and stress-strain relations, we obtain the general solution of anisotropic plastic field at a rapidly propagating plane-stress crack-tip. Applying this general solution to four particular cases of anisotropy, the general solutions of these four particular cases are derived. Finally, we give the anisotropic plastic field at the rapidly propagating plane-stress mode I crack-tip in the case of X=Y=Z

FORMATION CHARACTERISTICS OF Al-Cu-Fe-Mg QUASICRYSTALS

Several Al-Cu-Fe-Mg powders were produced by rapid solidification.The powders are crystalline at room temperature,but start to be transformed into quasicrystals when being heated to 600℃ and almost transformed to single icosahedral phase quasicrystals at about 800℃,and then,transformed into crystalline materials again at about 900℃.In this paper,the phase structural changes during heating,the composition range and formation characteristic of the Al-Cu-Fe-Mg quasicrystals are reported.

PRODUCTION OF ULTRAFINE PARTICLES OF OXIDES AND NITRIDES BY LASER BEAMS

Ultrafine particles of Al_(2)O_(3),MoO_(3),TiO_(2)and SiO_(2)were prepared by irradiate high power laser beams on material surface in O_(2)atmosphere as well as TiN in N_(2) atmosphere.X-ray diffractometer analysis identified that all oxides and nitrides powder obtained are crystalline except SiO_(2) particles which have amorphous struc-ture.

Effect of Substrate Temperature on Carbon Nitride Thin Films Prepared by Radio Frequency Sputtering

Carbon nitride thin films have been deposited by radio frequency sputtering at different substrate temperatures. The electronic structure and optical properties of the films have been systematically studied for the different substrate temperatures. The maximum N concentration in the films arrived at 41 at.%. The binding energy of core levels C 1s and N 1s produces a large shift in the range of 3.5-0.3eV depending on substrate temperature Ts. The band gap is at about 0.61-1.22eV. N atom concentration and shift of core level as well as electron band gap decrease with increasing Ts, which illustrates that raising Ts is not a good way to form carbon nitride films. Ultraviolet-visible near infrared spectra show that the films have a good transparency in near infrared region, but there is a sharp absorption peak around 2720 nm. The peak disappears when Ts is higher than 400℃.

A Study of the Isothermal Section in the W-Fe-Co Ternary System at 1380K

The purpose of the present paper isto determine the composition range ofthe θ intermediate phase and establishthe phase equilibria relation in theW-Fe-Co ternary system.The experimentalresult was compared with the calculationof phase diagrams in Guillermet’s work.1.Experimental ProcedureThe diffusion couple specimen usedin this investigation was prepared fromthe tungsten bar (99.96 wt-%),electro-

THE CONTINUAL DIFFERENTIABLE PEAK-UNIMODAL SOLUTIONS OF FEIGENBAUM’S FUNCTIONAL EQUATIONS

For the famous Feigenbaum's equations, in this paper, we established its constructive theorem of the peak-unimodal, then we found out other paths to explore the peak-unimodal solutions. For example, we proceed on the direction to try the non-symmetrical continuous peak-unimodal solutions and C1 solutions.

EFFECT OF POISSON RATIO ON THE PERFECTLY PLASTIC FIELD AT A RAPIDLY PROPAGATING PLANE-STRAIN CRACK-TIP

All the stress components at a rapidly propagating crack-tip in elastic perfectly-plastic material are the functions of θ only. Making use of this condition and the equations of steady-state motion, plastic stress-strain relations, and Mises yield condition with Poisson ratio, in this paper, we derive the general expression of perfectly plastic field at a rapidly propagating plane-strain crack-tip. Applying this general expression with Poisson ratio to Mode I crack, the perfectly plastic field at the rapidly propagating tip of mode I plane-strain crack is obtained. This perfectly plastic field contains a Poisson ratio, and thus, we can obtain the effect of Poisson ratio on the perfectly plastic field at the rapidly propagating tip of Mode I plane-strain crack.

ANISOTROPIC PLASTIC FIELDS AT A RAPIDLY PROPAGATING CRACK-TIP

Under the condition that all the stress components at a crack-tip are the functions of only, making use of the equations of steady-slate motion, stress-strain relations and Hill anisotropic yield conditions, we obtain the general solutions at a crack-tip in both the cases of anti-plane and in-plane strains. Applying these general solutions to the concrete cracks, the anisotropic plastic fields at the rapidly propagating tips of mode III and mode I cracks are derived.