Effects of misalignment on mechanical behavior of metals in creep

Creep tests were conducted by means of a closed loop servocontrolled materials test system. The strain history prior to creep is carefully monitored. Tests were performed for aluminum alloy 6061-O at 150 C and were monitored by a PDP 11/04 minicomputer at a preset constant plastic strain rate prehistory. The results show that the plastic strain rate prior to creep plays a significant role in creep behavior. The endochronic theory of viscoplasticity was applied to describe the observed creep curves. Intrinsic time and strain rate sensitivity function concepts are employed and modified according to the present observation

Railway Reform in China.

The purpose of this working paper is to consider the current situation of Chinese Railways, the progress of reforms to date, and possible future developments. The first section describes the current problems of Chinese Railways, as a vast organisation subject to strong central control, facing enormous and rapidly growing demands which it is unable to satisfy. The progress of reform in Chinese Railways to date, and in particular the Economic Contract Responsibility System instituted in the late 1980's and the development of joint venture companies to build new lines, are then described. In the following section the key reform models found in other countries - deregulation and privatisation of vertically integrated regional companies; separation of infrastructure from operations with open access andlor franchising competitors; or reorganisation on the basis of business sectors - are then described. None is fully suitable for China, but it is suggested that a combination of sectorisation, more commercial independence, further development of joint public/private partnerships and more contracting out, is the most likely way forward

Optimal boundary control of a simplified Ericksen--Leslie system for nematic liquid crystal flows in 2D2D

In this paper, we investigate an optimal boundary control problem for a two dimensional simplified Ericksen--Leslie system modelling the incompressible nematic liquid crystal flows. The hydrodynamic system consists of the Navier--Stokes equations for the fluid velocity coupled with a convective Ginzburg--Landau type equation for the averaged molecular orientation. The fluid velocity is assumed to satisfy a no-slip boundary condition, while the molecular orientation is subject to a time-dependent Dirichlet boundary condition that corresponds to the strong anchoring condition for liquid crystals. We first establish the existence of optimal boundary controls. Then we show that the control-to-state operator is Fr\'echet differentiable between appropriate Banach spaces and derive first-order necessary optimality conditions in terms of a variational inequality involving the adjoint state variables

Creep recovery and stress relaxation tests of 6061-0 aluminum

The investigation of creep recovery and stress relaxation in aluminum using a closed loop servo-hydraulic test system is described. The practicality of a computer controlled test system for constant plastic strain rate tension tests is demonstrated. The plastic strain rate and the magnitude of the initial strain are shown to have a noticeable effect on subsequent creep behavior of aluminum

Application of Cryogenic Treatment to Extend the Life of the TiAlN-Coated Tungsten Carbide Milling Cutter

Cutting tools are important to the manufacturing industry since they will affect production efficiency and product quality. Cryogenic treatment can improve the material properties by decreasing residual stress, stabilizing dimensional accuracy, and increasing wear resistance. The purpose of this study is to investigate the feasibility and effect of cryogenic treatment on the performance of TiAlN-coated tungsten carbide milling cutters for machining the Inconel alloy 625 in terms of different testing methods (e.g., hardness, wear resistance, residual stress, microstructure, and tool life test). Experimental results indicate that after cryogenic treatment there is less wear, the microstructure is denser, residual stress is decreased, the adhesion of coating and tungsten carbide is improved, and the tool life is effectively improved