Search results for "plastic"
showing 10 items of 7296 documents
Experimental investigation on BFRCM confinement of masonry cylinders and comparison with BFRP system
2021
Abstract Fabric reinforced cementitious mortar (FRCM) materials have started to be employed during the last years with the aim of overcoming the drawbacks related to the use of fibre reinforced polymer (FRP) composites, proving to be potentially suitable for strengthening masonry structures. Moreover, the will to develop materials able to guarantee a certain degree of sustainability without renouncing to adequate mechanical properties has drawn the attention to the use of basalt fibres, which appear to be a valid alternative to carbon or glass fibres. This work presents an experimental investigation on a basalt FRCM (BFRCM) system to confine circular masonry columns, aimed at evaluating the…
Specific interaction of desthiobiotin lipids and water-soluble biotin compounds with streptavidin
1991
As shown for biotin lipids (Ref. 1), the formation of perfect 2-D crystalline streptavidin domains can also be observed in the plane of desthiobiotin lipid monolayers. The binding constant of streptavidin with desthiobiotin (Ka = 5·1013 mol−1) is lower than that with biotin (Ka = 1015 mol−1) (Ref. 2). By adding free biotin into the subphase a competitive replacement and a detaching of the streptavidin domains from the desthiobiotin lipid monolayer takes place. Streptavidin domains built at receptor lipid monolayers are still functional. As could be shown, there are two biotin binding sites at each protein molecule that are fully accessible to biotin (Ref. 1). This can be proven by the inter…
Surface functionalization and surface recognition: Plasmon optical detection of molecular recognition at self assembled monolayers
1991
The synthesis of biotin- functionalized organic mercaptans and their chemisorption on gold surfaces is described. Biotin bound covalently to self assembled monolayers is recognized by streptavidin from aqueous buffer solutions. Spacer length and packing density of the biotin labels on the organic surface determine the docking kinetics. With a flexible and hydrophilic spacer very fast -diffusion controlled-docking is observed. As an alternative method of self assembly the spreading of organic mercaptans on water surfaces is established. Pressure-area diagrams of different functionalized mercaptans and disulfides are shown and their monolayer properties are discussed.
Ligand-receptor interactions directly measured with the surface forces apparatus
1991
Ligand-receptor interactions give rise to very strong bonds due to perfect geometrical fit. Using the Surface Forces Apparatus we have studied the interactions between membrane-bound biotin ligands and streptavidin receptors. We find an unusually strong short-range binding force associated with equally specific molecular rearrangements-both qualitatively and quantitatively unlike anything previously measured.
Surface effects, boundary conditions and evolution laws within second strain gradient plasticity
2014
Abstract The principle of the virtual power (PVP) is used in conjunction with the concepts of “energy residual” and “insulation condition” to address second strain gradient plasticity. The energy residual with its typical divergence format is an extra stress power playing the role of basic state variable to describe the gradient effects, whereas the insulation condition constitutes a global energy characterization of the body as part of the body/environment system. The microstructure of a second strain gradient material (but not of a first strain gradient one) is shown to exhibit surface effects with the formation of a thin boundary layer. This boundary layer is in local (and global) equili…
INVESTIGATIONS OF STRAIN AND STRESS STATE AND CAPACITY IN SHORT CYLINDRICAL SHELLS UNDER INTERNAL PRESSURE
1989
In the paper it has been assumed that a triaxial stress and strain state occurs in a shell. The finite element method was used and owing to that digitization of the problem was possible. Such digitization was necessary for a numerical analysis of the moment stress state in the shell. On the ground of physical relations of the Prandtl-Reuss plastic flow theory an algorithm was formulated. The algorithm was a basis of calculating strains and stresses and determining capacity in a short cylindrical shell with rigid bottoms. The shell was subject to internal pressure. Experiments were carried out, as well. The results obtained with: equations of the membraneous shell theory, using plastic flow …
On the Conditions to Prevent Plastic Shakedown of Structures: Part I—Theory
1993
For a structure of elastic perfectly plastic material subjected to a given cyclic (mechanical and/or kinematical) load and to a steady (mechanical) load, the conditions are established in which plastic shakedown cannot occur whatever the steady load, and thus the structure is safe against the alternating plasticity collapse. Static and kinematic theorems, analogous to those of classical shakedown theory, are presented.
A Study on Plastic Shakedown of Structures: Part I—Basic Properties
1993
For a continuous elastic-perfectly plastic solid body subjected to a combination of cyclic (mechanical and/or kinematical) load and of a steady (mechanical) load such as to produce plastic shakedown (i.e., alternating plasticity), a number of characterizing properties are established and discussed. The conditions for the body’s transition from plastic shakedown to ratchetting are also addressed.
On the Conditions to Prevent Plastic Shakedown of Structures: Part II—The Plastic Shakedown Limit Load
1993
Following the results of a companion paper, the concept of plastic shakedown limit load is introduced for an elastic-perfectly plastic material structure subjected to combined cyclic (mechanical and/or kinematical) loads and steady (mechanical) load. Static and kinematic approaches are available for the computation of this load, in perfect analogy with the classic (elastic) shakedown limit load. The plastic shakedown limit state of the structure being in an impending alternating plasticity collapse is studied and a number of interesting features of it are pointed out.
A nonlocal strain gradient plasticity theory for finite deformations
2009
Abstract Strain gradient plasticity for finite deformations is addressed within the framework of nonlocal continuum thermodynamics, featured by the concepts of (nonlocality) energy residual and globally simple material. The plastic strain gradient is assumed to be physically meaningful in the domain of particle isoclinic configurations (with the director vector triad constant both in space and time), whereas the objective notion of corotational gradient makes it possible to compute the plastic strain gradient in any domain of particle intermediate configurations. A phenomenological elastic–plastic constitutive model is presented, with mixed kinematic/isotropic hardening laws in the form of …