A Comparison of the High-Temperature Oxidation of 17Cr-2Ni and 18Cr-8Ni Austenitic Stainless Steels at 973 K

The oxidation behavior in air at 973 K of theaustenitic stainless steels 18Cr8Ni and17Cr-2.5Ni-10.5Mn-2Cu-0.17N (low-nickel content), wasstudied in a thermobalance. The steels were heated fromroom temperature up to 973K at 10 K min^-1, oxidizedfor 80 hr and then cooled to room temperature at 80 Kmin^-1. The two steels had the same weightgains, 0.18 mg cm^-2, which is equivalent tooxidation layers about 1.15 m theoretical thickness. In both cases, thegeneral shapes of the WS^-1 (mgcm^-2) curves vs. t (hours) were parabolic,but X-ray diffraction of the oxidized surfaces, surfaceand crosssection optical microscopy and SEM observations and EDSmicroanalysis show important differences betweenthem.     

Generation of efficient and user-friendly queries for helper robots to detect target objects

We are developing a helper robot that carries out tasks ordered by users through speech. The robot needs a vision system to recognize the objects appearing in the orders. However, conventional vision systems cannot recognize objects in complex scenes. They may find many objects and cannot determine which is the target. This paper proposes a method of using a conversation with the user to solve this problem. The robot asks a question to which the user can easily answer and whose answer can efficiently reduce the number of candidate objects. It considers the characteristics of features used for object identification such as the ease for humans to specify them by word, generating a user-friendly and efficient sequence of questions. Experimental results show that the robot can detect target objects by asking the questions generated by the method.     

Multipass rolling of aluminium alloys: finite element simulations and microstructural evolution

Abstract

Use of numerical predictive methods such as finite element analysis is becoming progressively more common for modelling industrial hot metal working and forming processes. These tools are used not only to predict the thermomechanical behaviour of metals but increasingly to predict microstructural changes by linking them to physical models of recrystallisation and textural evolution. This paper describes the development and application of a fully integrated model for the prediction of thermomechanical and microstructural behaviour during multipass hot rolling of aluminium alloy AA 3104. Finite element code ABAQUS/standard has been used in the work and the process is modelled assuming plane strain conditions. It is shown that for this alloy the static recrystallisation which occurs during interpass cooling does not significantly influence the thermomechanical response during subsequent rolling passes.     

Dynamic Young's modulus and glass transition temperature of selected tropical wood species

Abstract

Dynamic Young's modulus (E _d) of selected tropical wood species, namely Dyera polyphylla, Endospermum diadenum, Cratoxylum arborecens, Alstonia pneumatophora, Macaranga gigantea and Commersonia bartramia, used for the study was measured using the free–free flexural vibration method. Young's modulus from three point bending (E _3pb) and compression parallel to grain (E _cp) was also studied. The results show that the relationship between E _d and E _3pb for all wood species is very significant with the mean value of E _d consistently larger than or sometime equal to E _3pb. Surprisingly, the relationship between E _d and E _cp is not significant except for Alstonia pneumatophora. The dynamic mechanical thermal properties were also investigated using the dynamic mechanical thermal analyser (DMTA). The results showed that the storage modulus of the wood species at –90°C is in the range of 1·48–4·09 GPa with a glass transition temperature ranging from 50 to 70°C.     

Characterisation of severely deformed austenitic stainless steel wire

Abstract

The microstructure of 8 μm diameter wire produced by the severe deformation of 316L austenitic stainless steel has been examined using TEM and X-ray diffraction. The deformation imparted amounts to a true strain of 6·3. Data from previous studies on strain induced transformation of this steel have been combined with new results to show that true strains >2 are required in order to observe mechanical stabilisation, i.e. the cessation of martensitic transformation when the martensite/austenite interfaces are unable to propagate through the dislocation debris created in the austenite.     

Applicable conditions of instantaneous source used for welding heat conduction

Abstract

This paper deals with the sufficient conditions under which instantaneous heat source can be considered as welding heat source instead of moving source. Temperature rises calculated by instantaneous source and moving one were compared. The applicable conditions of the instantaneous heat source with errors of 1% and 5% were found. This enables us to select either moving or instantaneous source with information of welding speed, thermal diffusivity and the distance from the weld centre line to the interested location. Approximate equations to determine the maximum temperature rise using a moving source were proposed and the accuracy of their calculation was proved to be ～99%.     

Low temperature chemical synthesis of nanosized ceramic powders

Abstract

A variety of nanosized (particle dia. <100 nm) ceramic powders have been prepared from metal ion complex based precursor solutions. The precursor solution was prepared at room temperature from metal hydroxides, nitrates, or acetates mixed with suitable complexing agents such as amines, carboxylic acids, hydroxy carboxylic acids, or poly-hydroxy compounds. Calcination of the precursor mass at low external temperatures produces the nanosized ceramic powders. The examples discussed include perovskites, i.e. lead zirconate titanate PbZr_0·6 Ti_0·4O₃(PZT) and lead magnesium niobate PbMg_1/3 Nb_2/3 O₃ (PMN).     

Distribution Around the Oxide-Substrate Interface of Alloying Elements in Low-Carbon Steel

In order to study the physicochemical evolutionduring oxidation of Fe-C-X_i alloyssurfaces (X_i = Cu, Ni, Al, Si, S, withX_i% < 0.5 wt.%, C% < 0.1 wt.%), anoriginal analysis method has been used. After separating the oxide from the metalsubstrate, the first atomic layers of both innersurfaces have been observed by Auger ElectronSpectroscopy (AES). The depth profiles obtained, around0.4 m thick on both sides of the oxide-metal interface,have been compared for four steels of differentcomposition. Significant differences have been observedand described in this paper. A qualitativeinterpretation of diffusion processes has been proposed. Ametallographic study illustrates some physicalconsequences of alloying elements, especially on thescale thickness.     

Multi-Fingered Bimanual Haptic Interface Robot with Three-Directional Force Display

This paper introduces a bimanual haptic interface robot and presents results from its trial operation. Our aim in developing a bimanual haptic interface is to display high-precision three-directional forces at all 10 fingertips of both hands of the operator. By installing two five-fingered robot hands and two robot arms, we construct a bimanual haptic interface. A haptic interface that consists of robot hands and robot arms can provide multi-point contact between the operator and a virtual environment. However, there is the risk that robot hands and robot arms will collide while an operator is manipulating the haptic interface. To solve this problem, we also propose a collision avoidance control law for the multi-fingered bimanual haptic interface. Finally, to determine the validity of the proposed interface, we carry out several experiments. These results show the validity and great potential of the proposed bimanual haptic interface.