Deformation Of Metallic Materials Research Articles

Activation volume and activation energy for deformation of Nb HSLA steels

It is well established that the deformation of metallic materials is a thermally activated process which depends on temperature, time and strain rate. The major activation parameters are the activation volume, [Delta]V, the activation enthalpy, [Delta]H, and the Gibbs activation free energy, [Delta]G. All these parameters are used to characterize the dislocation mechanisms controlling the deformation processes. Because of the experimental difficulties, except for the study of Gibbs, very few other investigators have attempted to determine the activation volume for deformation at elevated temperatures even though this is of fundamental interest for many applications in engineering such as, in the hot working of metals and alloys. For instance, one class of metallic material, which is used in abundance for many applications, is Nb High Strength Low Alloy (HSLA) steel produced by controlled rolling. Nevertheless, no activation volume data for deformation have so far been available for these materials. In this study a stress relaxation technique has been used to determine the activation volume and the activation energy terms for plane strain hot compression testing for Nb HSLA steels for a range of deformation conditions.

Plastic strain determination using peak speckle pattern intensity

AbstractThis paper presents an integrated peak spectral intensity method for the measurement of plastic deformation in metallic materials. The method employs a laser speckle technique and a computer based image processing system. Test results on aluminium, brass and copper sheets subjected to bi‐axial stretching using the hydroforming process shows a correlation between the integrated peak spectral intensity coefficient Hi and the equivalent strain. In addition, the use of the parameter Hi requires less computation and enables measurement of plastic strains of up to 30%.

Large strain plastic deformation by crystallographic slio in metals

Abstract Large strain plastic deformation of metallic materials is investigated. The rate of change of the resolved shear stress applied to a slip system in a grain is expressed as a linear function of the slip rates. For this purpose, using an elastic-plastic analysis of the inclusion problem, the Jaumann rate of change of the stress state applied to the grain, together with its total spin, are obtained as a function of its deformation rate in the rigid-plastic case. It is shown that the existing stress has a significant influence on the accommodation tensors involved in the solution.

Inegrated autocorrelation method for plastic strain determination

This paper presents an integrated autocorrelation method for the measurement of plastic deformation in metallic materials. The method employs a laser beam to illuminate the test objects. The diffracted images are digitised, recorded and processed on a computer based image processing system. The subsequent speckle pattern correlation analysis yields information on the surface deformation of the test objects. The technique is applied to brass tensile specimens and it is found that the integrated autocorrelation coefficient is linearly proportional to the plastic shear strain. For the range of plastic strain measured the error involved would be less than 10%.

Regularities of the deformation of metallic materials under various conditions of static loading

The article analyzes the results of the application of the equation for describing creep of metals in various temperature and force ranges with the aid of the same numerically specified constants. An experimental evaluation is made of the possibility of describing from the same positions the regularities of instantaneous and short-term deformation, creep, stress relaxation, and creep limit.

金属材料の極低温セレーション変形とそのシミュレーション

金属材料の極低温セレーション変形とそのシミュレーション

A model of the high-temperature deformation of metallic materials with ellipsoidal second-phase particles

A micromechanics model developed in the previous work which incorporated the effect of dynamic recovery by diffusion of atoms was applied to the interpretation of the high-temperature deformation of metallic materials with ellipsoidal second-phase particles. A theoretical discussion based on this model was made on the effect of several factors including shape, particle size, orientation and elastic modulus of second phase on the work-hardening behaviour of the materials at high temperature. A good correlation was found between the result of the calculations and those of the experiments obtained by the present authors or other investigators of several kinds of metallic materials with ellipsoidal second-phase particles. The dynamic recovery model used in this study can be applied to the understanding of high-temperature deformation behaviour or to the prediction of the possible recovery mechanism of the materials.

The High-temperature Deformation of Metallic Materials with Ellipsoidal Second-phase Particles

Etude par un modele incorporant la restauration dynamique du comportement du durcissement par deformation. Analyse basee sur ce modele de l'influence de differents facteurs: forme, taille, orientation et module d'elasticite des particules de seconde phase. Le processus de restauration est controle dans ce modele par la diffusion en volume ou aux joints de grains des atomes. Application de ce modele a un acier austenitique contenant des carbures a du cuivre contenant SiO 2 . Bon accord entre la theorie et l'experience. Ce modele est donc applicable a la prevision du durcissement par deformation, et a la comprehension de la restauration des materiaux metalliques avec des particules de seconde phase non deformantes

Effect of strain rate on the characteristics of elastoplastic deformation of metallic materials

Effect of strain rate on the characteristics of elastoplastic deformation of metallic materials

Physical nature of acoustic emission in the deformation of metallic materials

Physical nature of acoustic emission in the deformation of metallic materials

Fundamental Study on Electrohydraulic Forming : III. The Effect of Dimension of Fuse Wire and Circuit Inductance on Pressure Pulse

There were many studies on electrohydraulic forming in which the deformation of metallic material was investigated. In most of the studies the wire used as pressure source is very fine. A clear account has not been given of the relationship between the dimension of wires and initial discharged circuit conditions such as initial capacitor voltage and circuit inductance, and then at a given stored electrical energy there is little reason to use what kind and dimension of wires as effective pressure source. For the reason of F.H. Webb's experimental fact that, if sufficient energy is accumlated into wire to vaporize it, the delaying time of boiling lasts for a time comparable with the time required for a sonic wave in the wire to propagate to the center and return, the longer the time just described is, the higher superheating is. This paper presents the results of experiments in which the characteristic of capacitor discharge circuit as electrohydraulic forming machine was used to explode fine copper wire of which diameter is 0.14 to 0.4mm. The best condition for creation of pressure pulse is investigated and discussed.

金属材料の塑性変形のレオロジー

金属材料の塑性変形のレオロジー