Different Types Of Deformation Research Articles

Chemical etching of dislocations and grain boundaries in ordered Ni 3Al crystals

A new selective chemical etchant is developed and tested for its ability to reveal dislocations in Ni{sub 3}Al single crystals. The best results have been found for the mixed solution of HNO{sub 3}/HCl/H{sub 2}O (1:1:1 volume ratio) with the aqueous solution of FeCl{sub 3} {center_dot} 6H{sub 2}O (over a range of 0.01--0.002 M). The etchant forms etch pits with the properties typical of dislocation etch pits. The etchant reveals both individual dislocations and dislocations in grain boundaries before and after different types of deformation of Ni{sub 3}Al samples. The features of the etchant, such as retaining the desired high contrast, the increase of the etch pit size with etching time, repeatability and practical convenience, make the developed etchant a good candidate for various applications, such as revealing dislocation structures on {l_brace}001{r_brace} and close surfaces and measuring dislocation mobility in Ni{sub 3}Al crystals. When combined with chemical polishing, the etchant is of prime interest, among other things, for studying the dislocation structure and its modification in the bulk of plastically deformed samples. The etching patterns demonstrate that the macroscopic motion of dislocations in Ni{sub 3}Al under local or bending deformation takes place mainly in the {l_brace}111{r_brace} primary glide systems. Somemore » indication of dislocation cross slip and multiplication was also observed in the studied samples.« less

On network descriptions of mechanical and optical properties of rubbers

Abstract The non-Gaussian full network model for rubber elasticity is reformulated in a more efficient and more micromechanics-motived manner. Based on such a full network description, a so-called full network model for rubber photoelasticity is proposed, by introducing directional polarizabilities into the individual links of the idealized randomly jointed chain. This optical theory can be used to study the optical properties or birefringence-strain behaviour of rubbers in arbitrary three-dimensional deformation states. Detailed comparisons with two approximate models, namely the classical three-chain model and an eight-chain model for rubber photoelasticity, are provided for different types of deformation. The predicted numerical results are compared with experimental data found in the literature.

Computational investigation of the influence of the environment on mechanical properties of solids

Using modified MNDO and AM1 semiempirical self-consistent-field molecular orbital methods in the cluster approach, we investigated the environmental influence on the mechanical properties of solids. The computational approach of the chemical reaction coordinate was developed for the study of mechanical deformation. The modeling of different types of deformation was considered. To test the validity of the method, we investigated the mechanical properties of simple hydrocarbon chains and silica systems. Uniaxial deformation and bending were considered for the heptane molecule. Verification of the mechanochemical calculations for polypropylene was fulfilled by analyzing its vibrational spectra. It was found that the influence of active medium particles (water, hydroxonium ion, surfactant) may have caused a sharp decrease of the strength of silica and hydrocarbons. The atom-level mechanism and some qualitative characteristics of these processes were studied. © 1995 John Wiley & Sons, Inc.

Erratum: Theoretical analysis of R-line shifts of ruby subjected to different deformation conditions

A theoretical approach to analyzing ruby R-line wavelength shifts under different types of deformation (uniaxial-strain compression and tension under shock loading, hydrostatic compression, and uniaxial-stress compression) and for different crystallographic orientations is presented. A symmetry-adapted representation of the various loading conditions in conjunction with crystal-field theory, but no point-ion model, is used to relate the shift of the R lines to deformation. The parameters needed in the model are obtained from shock-wave-compression data along the c and a axes. Without further iteration, these parameters are used in a consistent manner to analyze all remaining data: shock-wave-tension results, hydrostatic results, and uniaxial-stress results for different crystal orientations. Very good agreement is obtained between theoretical predictions and measurements. Changes in local site symmetry have been related to macroscopic deformation. For nonhydrostatic loading, effects of crystal orientation are important in analyzing R-line wavelength shifts. Suggestions for using ruby calibration at high pressures in diamond-anvil-cell measurements are presented. Implications of the present work for understanding shock-wave deformation in crystalline solids are indicated.

On improved network models for rubber elasticity and their applications to orientation hardening in glassy polymers

T hree-dimensional molecular network theories are studied which use a non-Gaussian statistical mechanics model for the large strain extension of molecules. Invoking an affine deformation assumption, the evolution of the network — consisting of a large number of molecular chains per unit volume, which are initially randomly oriented in space — is shown to be governed by a balance equation in orientation space. Eulerian and Lagrangian type formulations of these balance equations are given, and the closed-form analytical solution for the so-called Chain Orientation Distribution Function is derived. This full network model is then used to describe the large strain inelastic behaviour of rubber-like materials. Detailed comparisons with experimental results and with two approximate models, namely the classical three-chain model and a very recently proposed eight-chain model, are provided for different types of deformation and rubbers. Finally, the network model is applied to describe the orientational hardening in amorphous glassy polymers, and confronted with experimental data for polycarbonate. The inherent physical limitations of the network theory for both applications are discussed.

Role of interfacial properties on the motion and deformation of capsules in shear flow

The influence of interfacial properties on the dynamics of a capsule freely suspended in viscous liquid subjected to flow is assessed. First, the case of a liquid-liquid interface considered: experimental evidence and theoretical models show that the drop deformat depends on the type of flow, the internal to external viscosity ratio and the capillary number which measures the ratio between surface tension and viscous forces. Burst of the drop predicted to occur when the normal stress equilibrium cannot be satisfied everywhere on interface. Next, we consider the case of capsules, which are liquid drops enclosed by a so depormable interface. From experiment and theoretical models, they are known to deform and to burst in some cases. Their motion depends on essentially the same parameters as liquid drops, but different interfacial constitutive laws lead to different types of deformation and motion.

Theoretical analysis of R-line shifts of ruby subjected to different deformation conditions.

A theoretical approach to analyzing ruby R-line wavelength shifts under different types of deformation (uniaxial-strain compression and tension under shock loading, hydrostatic compression, and uniaxial-stress compression) and for different crystallographic orientations is presented. A symmetry-adapted representation of the various loading conditions in conjunction with crystal-field theory, but no point-ion model, is used to relate the shift of the R lines to deformation. The parameters needed in the model are obtained from shock-wave-compression data along the c and a axes. Without further iteration, these parameters are used in a consistent manner to analyze all remaining data: shock-wave-tension results, hydrostatic results, and uniaxial-stress results for different crystal orientations. Very good agreement is obtained between theoretical predictions and measurements. Changes in local site symmetry have been related to macroscopic deformation. For nonhydrostatic loading, effects of crystal orientation are important in analyzing R-line wavelength shifts. Suggestions for using ruby calibration at high pressures in diamond-anvil-cell measurements are presented. Implications of the present work for understanding shock-wave deformation in crystalline solids are indicated.

Structural-statistical analysis of the strain properties of laminated reinforced plastics

The structural relations derived here make it possible to analytically predict the main statistical characteristics of the strain properties of an LRP with allowance for the mutual correlation of the random parameters of the structure. Use of the proposed relations is valid for studying combination loading (bending and a plane stress state), as well as when the structure of the composite is unbalanced. We evaluated the scale effect associated with the presence of multiple layers and determined the impact of this effect on the scatter of the strain properties of the LRP for different types of deformation. We also proposed a method of determining the actual statistical characteristics of layers indirectly — on the basis of experimental testing of multilayered unidirectional plastics. One promising prospect is the use of these results to formulate and solve problems involving optimization of the structure of LRP's on the basis of criteria ensuring the composite's reliability and dimensional stability. Finally, the results can also serve as a basis for establishing scientifically substantiated safety factors for stiffness.

Characterization of various types of deformation and their corresponding deviatoric stress tensors using microfault analysis

Considering an ideally prefractured material, based on Mohr's representation and Bott's model, we define the geometry and the peculiarities of the different theoretical fault domains which are likely to be reactivated under different tectonic regimes. The theoretical striations associated with the different types of deformation are also calculated. The compressive strike-slip, extensive strike-slip, radial extensive and constrictive types of deformation are specified. In the second part of this paper, using Etchecopar's computer-aided method, a quantitative structural analysis of various types of superficial deformation has been carried out in different study areas (southern France, Greece, Spain, Tunisia and Nigeria). The geometry of the microfault domains, as well as the nature of the associated tensors are determined for each type of regional deformation. The problem of the spatial homogeneity of the tensors deduced by the microtectonic analysis within the framework of a particular tectonic phase is also discussed.

The Queen Charlotte Islands refraction project. Part II. Structural model for transition from Pacific plate to North American plate

The oceanic-continental boundary west of the Queen Charlotte Islands is marked by the active Queen Charlotte Fault Zone. Motion along the fault is predominantly dextral strike slip, but relative plate motion and other studies indicate that a component of convergence between the oceanic Pacific plate and the continental North American plate presently exists. This convergence could be manifest through different types of deformation: oblique subduction, crustal thickening, or lateral distortion of the plates. In 1983, a 330 km offshore–onshore seismic refraction profile extending from the deep ocean across the islands to the mainland of British Columbia was recorded to investigate (i) structure of the fault zone and associated oceanic–continental boundary and (ii) lithospheric structure beneath the islands and Hecate Strait to define the regional transition from Pacific plate to North American plate and thus the nature of the convergence. Two-dimensional ray tracing and synthetic seismogram modelling of many record sections enabled the derivation of a composite velocity structural section along the profile. The structural section also was tested with two-dimensional gravity modelling. Part I of the study addressed the structure of the fault zone; part II addresses lithospheric structure extending eastward to the mainland.The derived velocity structure has some important and well-constrained features: (i) anomalously low crustal velocities (5.3 km/s with a 0.2 km/s per km gradient) underlain by a steep, 19 °eastward-dipping boundary above the mantle in the terrace region west of the main fault; (ii) a thin crust of 21–27 km beneath the Queen Charlotte Islands; and (iii) a gentle 4 °eastward dip of the Moho below Hecate Strait as crustal thickness increases from 27 km to 32 km. The gravity modelling requires that mantle material extend upwards to a depth of about 30 km below the mainland and indicates that an underlying subducted slab, if it exists, extends eastward no farther than the mainland.Unfortunately, the velocity structure delineated by this study could not unambiguously determine the mode of deformation, because the lowermost crustal block beneath Queen Charlotte Islands and Hecate Strait can be interpreted as subducted oceanic crust or middle to lower continental crust. Thus, two different tectonic models for the transition from Pacific plate to North American plate are discussed: in one, oblique subduction is the principal characteristic; in the other, oceanic lithosphere juxtaposed against continental lithosphere across a narrow boundary zone along which only transcurrent motion occurs is the dominant feature. Based on the thin crust beneath the Queen Charlotte Islands, the lack of a wide zone of deformation along the plate boundary region, and other geological and geophysical characteristics, oblique subduction is the more plausible model.

The dynamical response of dislocation structures introduced by twisting deformation of high purity aluminium single crystals

The dynamical response of dislocation structures introduced by various types of deformation was studied with low frequency internal friction measurements. A strong internal friction peak situated around 310°C was observed. It is shown that the peak is associated with the dynamical response of dislocation structures introduced by twisting deformation. Such dislocation structures are stable at high temperatures and therefore correspond to a minimum energy state. Tensile deformation reduces this peak which has an activation energy of about 2 eV. The non-elastic strain component during relaxation is produced by dislocation slip, but the relaxation rate is controlled by the non-conservative shift of the nodes of the dislocation networks. The dislocation configurations produced by different types of deformation were studied with the help of X-ray Laue spot analysis and transmission electron microscopy observations. A phenomenological theory based on elastoplasticity is proposed.

Effects of insect growth inhibitor Alsystin on Culex quinquefasciatus Say (Culicidae: Diptera)

The insect growth inhibitor Alsystin (SIR 8514) was tested for its effects against the immature and adult stages of Culex quinquefasciatus Say under laboratory conditions. A linear correlation was revealed between concentration and larval and pupal mortality. Larval mortality increased from 5% at 0.005 ppm to 74.4% at 0.1 ppm of Alsystin. Complete inhibition of adult emergence resulted after larval exposure to 0.05 ppm. Exposure of eggs (at 0 hr of age) to 0.1 ppm and 10.0 ppm of Alsystin, resulted in considerable decrease of hatching from 87.0% in the control to 61.0% at 1.0 ppm and to 48.0% at 10.0 ppm. The adults of C. quinquefasciatus were seen attracted to the bowls containing 50.0 ppm and 100.0 ppm of Alsystin. However, landing adults died within a short period of time. The different types of deformation in the larva, pupa and adult as a result of exposure to Alsystin are illustrated.

Rheological properties of mesomorphic polyester melts on shear and longitudinal deformation

The authors have studied the rheological properties of thermotropic polyester melts—polydecamethylene terephthaloyl-bis-4-oxybenzoate—on steady and periodic shear deformation and also on uniaxial stretching in the temperature interval of the existence of mesophases (230–290°C). The flow of the polyester melts follows a plastic mechanism passing in some cases at high deformation rates into a quasi-Newtonian regime. The result of the different relationship of the processes of orientation and fracture of the structure in LC systems for different types of deformation is that the longitudinal viscosity of the melts is higher than the shear by more than a decimal order.

A bounding technique for dynamic plastic deformations of damped structures

This paper presents a bounding principle for obtaining bounds on plastic deformations of discrete-type structures subjected to dynamic (mechanical and/or thermal) external actions. The principle holds true for fully specified loading histories, as well as for unknown sequences of short-duration excitations of a given set, independently of whether the structure shakes down or not. The perturbation method herein used enables the principle to generate bounds on different types of deformations, such as plastic strains, residual displacements and plastic work produced within any portion of the structure — just by suitably choosing the perturbation parameters. With the aid of a time discretization, suboptimal and optimal bounds can be computed by means of LP, QP and NLP numerical procedures. The dynamic characteristics of the structure, i.e. its natural frequency and vibration modes, are shown to play a crucial role. A simple numerical example is also presented.

Acoustic emission for physical examination of metals

AbstractAcoustic-emission techniques are beginning to be frequently used as a means of detecting and locating deformation and fracture processes in both metallic and non-metallic engineering structures. This has happened despite a relatively poor understanding of the basic physical processes involved in the generation, propagation, and detection of acoustic-emission signals, and of the influence in metals of factors such as composition and microstructure, upon the acoustic emission from different types of deformation and fracture processes. The measurement of acoustic emission, potentially, could yield much information about dynamic aspects of these processes. However, it is shown that the limitations of existing acoustic-emission recording instrumentation have enabled only qualitative information to be obtained to date. Even this data, however, has demonstrated that metallurgical variables greatly affect the acousticemission response of metals, and simple models to account for this are discussed.

Landslides along the Angara reservoirs

The present work characterizes the reactivation of existing landslides and formation of new ones on the shores of the Angara reservoir; it describes different types of deformations in the superficial deposits and bedrock; the role of erosion is estimated.

Stress distribution along the length of a fiber during different types of deformation of composites

Stress distribution along the length of a fiber during different types of deformation of composites

Tectonophysical characteristics of stresses, slow deformation in the Earth's crust, and the earthquake mechanism

This paper discusses certain basic problems of tectonophysics studied in our laboratory. Models of folding have been made that lead to methods of calculating the strain due to plastic flow in natural folds. A correlation between the viscosity of plastic flow of crustal rocks and the absorption of seismic waves was found and is used to estimate this viscosity in the crust. The orientation and magnitude of tectonic stress fields in the crust are determined from the polarities of seismic waves, the strain rate of the crust, the energy released by earthquakes, and the strength of materials studied in the laboratory. Different types of deformation observed in the field are discussed both in terms of results of laboratory models and from a theoretical point of view. The influence of pre-existing faults on the stress field is studied with laboratory modeling.

Microstructural interpretation of the stress-strain behaviour of the WCCo composite material

Of the two phases forming the WCCo structure the binder phase is strengthened in three ways: solution hardening, tri-axial stress state, and dislocation repulsion from the WC grains, Different types of deformation of the carbide network are discussed. Their contribution to the non-elastic behaviour of the composite is found to be negligeble, and so attention is dicreted to the deformation properties of a number of carbide-binder-carbide configurations. Two such configurations are analysed in detail, and one of them, which corresponds to a mechanical model earlier proposed by the author, is found to have non-elastic properties very similar to those observed for WC-Co alloys.

Effect of cycle asymmetry on the dynamic properties of rubbers in tension

The dynamic properties of rubbers have been investigated at large extensions in asymmetric cycles. Methods of calculating the characteristics of the elastic C∞ and hysteretic A properties of rubbers in two regimes are presented: 1) when the harmonic strain amplitude e0 and the mean strain ɛ are given; 2) when the harmonic displacement amplitude w0 of the rubber specimen and a spring dynamometer connected in series and the static load Qst are given. It is shown that in the case of vulcanizates based on crystallizing rubbers and active fillers in the region of strains e0, e and loads Qst causing crystallization during extension C∞ and A increase with increase in e0, e, and Qst. The variation of C∞ and A with e0, e, and Qst is qualitatively different for different types of deformation.