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Strain Relations (strain + relation)

Distribution by Scientific Domains

Polymers and Materials Science	37%

Selected Abstracts

Mechanical Properties and Corrosion Resistance of a Novel Ni-Cr-Mo Alloy,

ADVANCED ENGINEERING MATERIALS, Issue 1-2 2007
P. Huang
A new Ni-23Cr-18Mo (wt.%) alloy, designated as Nistelle Super C, was developed recently at Deloro Stellite Inc. for high corrosion resistance applications. Microstructure and phase transformation behaviour of the alloy were studied using SEM and DSC techniques, respectively. Mechanical properties such as stress - strain relation of the alloy and load , depth relation of individual phases of the alloy were determined under uniaxial tension and under nano indentation, respectively. Corrosion resistance of the alloy in oxidizing and reducing acids was evaluated in accordance with ASTM standard test designation G31-72. [source]

Modelling elastic media with the wavelet transform

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2001
João Willy Corrêa Rosa
Summary We present a new method for modelling 2-D elastic media with the application of the wavelet transform, which is also extended to cases where discontinuities simulate geological faults between two different elastic media. The basic method consists of the discretization of the polynomial expansion for the boundary conditions of the 2-D problem involving the stress and strain relations for the media. This parametrization leads to a system of linear equations that should be solved for the determination of the expansion coefficients, which are the model parameters, and their determination leads to the solution of the problem. The wavelet transform is applied with two main objectives, namely to decrease the error related to the truncation of the polynomial expansion and to make the system of linear equations more compact for computation. This is possible due to the properties of this finite length transform. The method proposed here was tested for six different cases for which the analytical solutions are known. In all tests considered, we obtained very good matches with the corresponding known analytical solutions, which validate the theoretical and computational parts of the project. We hope that the new method is useful for modelling real media. [source]

Accurate eight-node hexahedral element

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2007
Magnus Fredriksson
Abstract Based on the assumed strain method, an eight-node hexahedral element is proposed. Consistent choice of the fundamental element stiffness guarantees convergence and fulfillment of the patch test a priori. In conjunction with a ,-projection operator, the higher order strain field becomes orthogonal to rigid body and linear displacement fields. The higher order strain field in question is carefully selected to preserve correct rank for the element stiffness matrix, also for distorted elements. Volumetric locking is also removed effectively. By considerations of the bending energy, improved accuracy is obtained even for coarse element meshes. The choice of local co-ordinate system aligned with the principal axes of inertia makes it possible to improve the performance even for distorted elements. The strain-driven format obtained is well suited for materials with non-linear stress,strain relations. Several numerical examples are presented where the excellent performance of the proposed eight-node hexahedral is verified. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Anelastic Behavior of Plasma-Sprayed Zirconia Coatings

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2008
Yajie Liu
Low-temperature thermal cycling of plasma-sprayed zirconia coatings reveals unique mechanical responses in their curvature measurements, namely nonlinear and cyclic hysteresis, collectively termed as anelastic. These features arise from the inherent layered, porous, and cracked morphology of thermal-sprayed ceramic materials. In this paper, the mechanisms of anelasticity are characterized by crack closure and frictional sliding models, and stress,strain relations of various thermal-sprayed zirconia coatings were determined via an inverse analysis procedure. These results demonstrate process conditions such as powder morphology and spray parameters significantly influence the mechanical behaviors of coatings. The unique anelastic responses can be used as valuable parameters in identifying coating quality as well as process reliability in manufacturing. [source]

Homogenizing the acoustic properties of a porous matrix containing an incompressible inviscid fluid

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 10 2003
J. L. Ferrin
We undertake a rigorous derivation of the Biot's law for a porous elastic solid containing an inviscid fluid. We consider small displacements of a linear elastic solid being itself a connected periodic skeleton containing a pore structure of the characteristic size ,. It is completely saturated by an incompressible inviscid fluid. The model is described by the equations of the linear elasticity coupled with the linearized incompressible Euler system. We study the homogenization limit when the pore size ,tends to zero. The main difficulty is obtaining an a priori estimate for the gradient of the fluid velocity in the pore structure. Under the assumption that the solid part is connected and using results on the first order elliptic systems, we obtain the required estimate. It allows us to apply appropriate results from the 2-scale convergence. Then it is proved that the microscopic displacements and the fluid pressure converge in 2-scales towards a linear hyperbolic system for an effective displacement and an effective pressure field. Using correctors, we also give a strong convergence result. The obtained system is then compared with the Biot's law. It is found that there is a constitutive relation linking the effective pressure with the divergences of the effective fluid and solid displacements. Then we prove that the homogenized model coincides with the Biot's equations but with the added mass ,a being a matrix, which is calculated through an auxiliary problem in the periodic cell for the tortuosity. Furthermore, we get formulas for the matricial coefficients in the Biot's effective stress,strain relations. Finally, we consider the degenerate case when the fluid part is not connected and obtain Biot's model with the relative fluid displacement equal to zero. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Structural relaxation and evolution of yield stress in epoxy glass aged under shear strain,

POLYMER ENGINEERING & SCIENCE, Issue 1 2005
Hiroshi Kawakami
Hollow cylindrical specimens of annealed epoxy glass were twisted and then aged for various periods of time under shear strain. At the end of the aging process, we twisted the specimens again to determine the stress,strain relations. For specimens aged under a shear strain of 0.005 or 0.01, the stress relaxation behavior was almost independent of the amount of strain imposed, and the value of stress at the upper yield point, regardless of aging time, was almost the same as that of the annealed specimen. On the other hand, for specimens aged under a strain of 0.02 or 0.04, the stress relaxation behavior depended on the value of the strain applied, and the value of stress at the upper yield point first decreased and subsequently increased with increasing aging time. These results led us to the following conclusions: If epoxy glass is strained largely, the originally stable structure becomes unstable. Also, when epoxy glass is aged under strain, the stability of the structure continues to decrease for a short period of time after deformation ceases, and then increases with increasing aging time. POLYM. ENG. SCI. 45:20,24, 2005. © 2004 Society of Plastics Engineers. [source]

A Cross-National Examination of Self-Efficacy as a Moderator of Autonomy/Job Strain Relationships

APPLIED PSYCHOLOGY, Issue 1 2010
Margaret M. Nauta
This study evaluated the cross-national validity of cognitive appraisal theories (e.g. Lazarus & Folkman, 1984) of stress by examining differences in the interaction of job autonomy and generalised self-efficacy in the prediction of psychological and physical strains among US and Chinese employees. As posited by cognitive appraisal theories, high self-efficacy served as a buffer against low job autonomy in the prediction of psychological and physical strains among US employees. However, the buffering effect of self-efficacy was unclear among Chinese employees. For Chinese employees with high self-efficacy, job autonomy was negatively related to job strains, but for Chinese employees with low self-efficacy, job autonomy was positively related to job strains. The results highlight the importance of attending to culture in examinations of stressor,strain relations. Cette étude porte sur la validité transnationale des théories de l'évaluation cognitive du stress (par exemple: Lazarus & Folkman, 1984) par l'analyse de différences dans l'interaction entre l'autonomie dans le travail et l'auto-efficience globale dans la prédiction des tensions physiques et psychologiques chez des salariés américains et chinois. Comme les théories de l'évaluation cognitive le prévoient, un niveau élevé d'auto-efficience compense le manque d'autonomie dans la prédiction de tensions physiques et psychologiques chez les salariés américains. Toutefois, l'effet compensatoire de l'auto-efficience n'apparaît pas clairement chez les salariés chinois. Pour les salariés chinois disposant d'une forte auto-efficience, l'autonomie dans le travail était négativement corrélée aux tensions professionnelles, mais chez ceux qui étaient dotés d'une auto-efficience faible, l'autonomie était positivement liée aux tensions professionnelles. Ces résultats mettent en évidence la nécessité de prendre la culture en considération dans l'étude de la relation entre les facteurs de stress et les tensions. [source]

Personal Goal Facilitation through Work: Implications for Employee Satisfaction and Well-Being

APPLIED PSYCHOLOGY, Issue 2 2006
Laura ter Doest
Que le travail facilite la réalisation des objectifs personnels dépend de la perception de l'impact du travail sur l'atteinte de ces objectifs personnels. En accord avec la littérature sur l'autorégulation et le modèle cybernétique du stress organisationnel proposé par Edwards (1992), la facilitation de l'accès à ses objectifs personnels par le travail fut supposée en relation positive avec les attitudes relatives à l'emploi et le bien-être de l'employé. En outre, on a prédit un rapport plus étroit entre la facilitation de l'accès à ses objectifs personnels par le travail et les performances du salarié quand les buts personnels étaient fortement valorisés. Ces hypothèses ont été mises à l'épreuve à travers un questionnaire rempli par 1036 employés du secteur de la santé. D'après l'analyse de régression, la facilitation de l'accès à ses objectifs personnels par le travail expliquait une part importante de la variance du bien-être et des attitudes relatives à l'emploi, même après avoir contrôlé les caractéristiques des postes en référence au modèle de Karasek concernant les relations agents stressants,tension au travail (1979; Karasek & Theorell, 1990). L'importance des objectifs n'avait qu'une influence des plus limitées. On en conclut que la facilitation de l'accès à ses objectifs personnels par le travail offre une voie prometteuse pour explorer les attitudes liées à l'emploi et le bien-être, en complément des modèles plus traditionnels des caractéristiques de l'emploi. Personal goal facilitation through work refers to perceptions of the extent to which one's job facilitates the attainment of one's personal goals. In line with the self-regulation literature and Edwards' (1992) cybernetic model of organisational stress, personal goal facilitation through work was predicted to show positive associations with job attitudes and employee well-being. Moreover, stronger relationships between personal goal facilitation through work and employee outcomes were predicted for highly valued personal goals. These predictions were investigated in a questionnaire study of 1,036 health care employees. In regression analyses, personal goal facilitation through work accounted for substantial variance in job attitudes and well-being, even after controlling for job characteristics from Karasek's (1979; Karasek & Theorell, 1990) model of occupational stressor,strain relations. There was only very limited evidence of moderating effects of goal importance. It is concluded that personal goal facilitation through work offers a promising source of insight into job attitudes and well-being, complementing more traditional job characteristics models. [source]