Showing papers by "Yanshan University published in 1997"

Quantitative phase analysis of Inconel 718 by X-ray diffraction

Abstract: This revised version was published online in November 2006 with corrections to the Cover Date.

Simulation of the Hot Ring Rolling Process by Using a Thermo-Coupled Three-Dimensional Rigid-Viscoplastic Finite Element Method

Abstract: During hot metal forming, the temperature variation and plastic deformation affect each other considerably. In the present investigation, ring rolling of hot steel is simulated by using a three-dimensional thermo-coupled rigid-viscoplastic finite element method. A new term is added to the functional in the variational approach to consider the influence of the frictional torque of the mandrel bearing, and the coupled thermal-mechanical simulation is performed by the iteration between the rigid-viscoplastic finite element analysis and the thermal finite element analysis. Since the deformation region and the severe temperature changes are restricted to the vicinity of the roll gap, only a ring segment and parts of the rolls are analyzed using a steady-state treatment to save computation time. Roll force and torque, width spread, temperature distributions, the distributions of strain and strain rate and the distributions of relative velocity and stress at the roll surfaces are obtained. The results show that the angular velocity of the driven roll has a significant influence on the temperature variations in the ring and the rolls, to which attention should be paid in the design of the process. The method presented can also be used to analyze other forming processes such as unsymmetrical plate rolling, symmetric rolling, and extrusion.

High performance steel plates with micro-laminated layer structure produced by plastic deformation

Abstract: Abstracts are not published in this journal

Solidification characteristics of Pd40Ni40P20 alloy under microgravity condition

Abstract: The microstructure and solute distribution of Pd40Ni40P20 alloy solidified both on board a Chinese retrievable satellite (μg) and on the earth (1g) were studied. It was found that the dendritic primary phase formed under microgravity condition was finer and shorter. In the central area of the sample some asteroidal patterns of the primary phase were present in the microstructure. The primary spacing of the dendrites at the cooling rate of 0. 056 K/s was smaller than that measured in the ground-based experiments at the same cooling rate, but almost the same as that cooled at 0.67 K/s on the ground. With these experimental results, mass transport coefficients both in space and on the earth were evaluated.

Fine structure in Fresnel diffraction patterns and its application in optical measurement

Abstract: The function of light intensity distribution of Fresnel diffraction from an opaque fibre is derived, and the fine structure in the diffraction pattern is theoretically described. In this paper, the relationship between fibre diameter and fine structure in the diffraction pattern is given. The fine structure can be used to measure the diameter of fibres, and measuring subscript limits may be greatly squeezed. Several fibres of different diameters are measured by means of the fine interference fringe in the diffraction pattern, and experimental results show the improved diffraction technique is highly reliable with higher precision compared with the original technique.

Composition and microstructure of brazing joint of triple wall brazed tube

Abstract: With the help of scanning electron microscope(SEM)and electron probe (EPMA),the chemical composition and microstructure of brazing joint of triple wall brazed tube have been investigated and analyzed.It is shown that ①the brazing joint consists of upper and lower diffusion area as well as the interracial area;②in the ferrite grain boundaries in diffusion area,Cu concentration in weight can be up to 10%,while Fe concentration in weight in the interracial area is about 6 %;③α and e solid solution are formed in the diffusion and interracial area;④the brazing joint is of good properties.

Relationship between cooling intensity and thickness of strand shell im mould

Abstract: Based on the Stiffen solidification law . the relationship between the thickness of strand shell and the cooling intensity and casting speed are formulated in this paper. Therefore , the cooling intensity and the casting speed can be rationally determined by the thickness of strand shell . The results calculated with the given formula are almost the same as that calculated with the solidification square root law , so that the solidification coefficient can be determined.

Co-deposition of Co-Ni alloys and their microstructure analysis by PoSAP

Abstract: ion concentration in the depositing baths on the Co content and the microstruc-ture in the corresponding deposit was studied by the position sensitive atom probe （PoSAP）,TEM and X-ray diffraction. The Co-Ni phase diagram shows that, at room temperature,there are two phases in Co-Ni alloys, one is eCo with hcp lattice, the other is αCo of fcc lat-tice. A Co-Ni alloy with a Ni content below 27% consists of single eCo, beyond 36% consistsof single αCo, in between consists of eCo + αCo. The examination results of TEM, SEM andX-ray diffraction indicated that the Co-Ni deposits with average grain size of 70 nm and thick-

Study on pneumatic roll-cutting shearerfor small tubes

Abstract: In this article, the roll-cutting and grip forces are investigated by the cutting theory and the slip line theory. A new pneumatic roll-cutting shearer has been designed for small tubes.

In Situ Investigation of the Effect of Hydrogen on the Plastic Deformation Ahead of the Crack Tip and the Crack Propagation for 0.15C-1.5Mn-0.17V-0.012N Steel

Abstract: The influence of hydrogen on the deformation ahead of the crack tip and the crack propagation were observed and studied in situ under transmission electron microscopy with dynamic tensile deformation for bridge steel The results show that hydrogen can promote local plastic deformation ahead of the crack tip and change the mode of crack propagation so that the crack will propagate in a zigzag path

Design of the pipe of laying head and its load analysis

Abstract: With a dual function in r, z direction, the pipe shape of laying head has been composed, and a method to calculate the stress in wire, the load moment and energy consumption of laying head is obtained. The effect of pipe shape on stress in wire and load of laying head has been analysed, thus the basis for designing laying head is provided.

Meso-scopical effects during fatigue crack initiation

Abstract: Evident changes in X-ray diffraction patterns are observed in surface or sub-surface layers of 16Mn and 300M steel specimens which have been tested under cyclic stress with stress levels equal to fatigue limits of correspondent steels and did not broken until 107cycles. Such layers are located at the surface for surface-unhardened 16Mn and 300M specimens and their thickness are about 3 diameters of ferrite grain and 15 diameters of original austenite grain, respectively; but for shot peened 300M specimen, such layer is located beneath the hardened surface layer, in the region with tensile residual stress, and its thickness is about 12 diameters of original austenite grain. These facts show that, even under the critical conditions for fatigue crack initiation, there always exist meso-scopical pre-yielding regions which consist of rather many grains and sustain back and forth sliding during fatigue test.

Oscillation for systems of nonlinear neutral type parabolic partial functional differential equations

Abstract: This paper discusses the oscillation of solutions for systems of nonlinear neutral type parabolic partial functional differential equations of the form 1 $$\frac{\partial }{{\partial t}}[u_i (x,t) - \sum\limits_{k = 1}^n {p_k (t)u_i (x,t - \sigma _k (t))] + A_i (x,t)u_i (x,t) + \sum\limits_{j = 1}^m {B_{ij} (x,t)f_{ij} (u_j (x,t - \tau )) = C_i (t)\Delta u_i (x,t) + \sum\limits_{j = 1}^m {D_{ij} (t)\Delta u_i (x,t - r_j ),i = 1,2,,m,(x,t) \in \Omega {\text{ x }}(0,\infty ) \equiv G} } } $$ where Ω is a bounded domain in Rn with piecewise smooth boundary 1 $$\Delta u_1 (x,t) = \sum\limits_{j = 1}^n {\left( {\frac{\partial }{{\partial x_j^2 }}^2 } \right)u_1 (x,t),\tau ,r_j = {\text{ const}}{\text{}} > 0} $$ Sufficient conditions are obtained for oscillation of solutions of the systems, these results are illustrated by some examples

The bending of set squares with one free oblique edge under a concentrated load

Abstract: In the paper, the reciprocal theorem is applied to research on the bending of set square with one free oblique edge and two clamped edges under a concentrated load acting at any point. This method is simpler and general.