Elasto plastic

Modelling for Fatigue and Fracture Prediction of Brittle and Elasto-Plastic Materials Using Acoustic Emission Technics. 

It is very important, from one hand, to accept a hypothesis about the material fracture properties before physical model building because general view of TF is going to change depending on mechanical model (brittle, elasto-plastic, visco-elasto-plastic, ete.) of the material. From the other hand, it is necessary to keep in mind that the material response to loads or actions is different depending on the accepted mechanical model because rheological properties of the material determine type of response in time. The most remarkable difference can be observed between brittle materials and materials with explicit plastic properties. 

Figure 5. Amplitude-phase characteristics of the model for visco-elasto-plastic (left column) and brittle (right column) materials 1- spectrum responses 2- TF models.

Figure 6. Location of poles and zeros for visco-elasto-plastic material (left) and brittle material (right) under loading close to fiacture.

Annin B.D., Cherepanov G.P. (1983) Elasto-plastic problem. Nauka, Novosibirsk (in Russian). 

Arutunyan N.H., Drozdov A.D., Naumov V.E. (1987) Mechanics of growing visco-elasto-plastic bodies. Nauka, Moscow (in Russian). 

Kovtunenko V.A. (1994c) Iteration penalty method for the contact elasto-plastic problem. Control and Cybernetics 23 (4), 803-808. 

Atluri, S.N., On Constitutive Relations at Finite Strain Hypo-Elasticity and Elasto-Plasticity with Isotropic or Kinematic Hardening, Comput. Methods Appl. Mech. Engrg. 43, 137-171 (1984). 

Fig. 2. Schematic of energy dissipation in a commonly used peel test. The energy dissipation can occur in the adhesive and/or the adherends. The extent of energy dissipation depends on the elasto-plastic properties of the adhesive and the adherends under the test conditions as well as the local stresses and strains near the crack tip.

Fig. 10. Typical load-displacement graph for elasto-plastic indentation.

Another area of recent interest is covulcanization in block copolymers, thermoplastic rubbers, and elasto-plastic blends by developing an interpenetrating network (IPN). A classical example for IPN formation is in polyurethane elastomer blended acrylic copolymers [7]. 

If the collision is purely elastic or elasto-plastic, then the two bodies will depart the colli-sion with different velocities. 

For purely elastic impacts, e = 1, and for purely plastic impacts, e = 0. For elasto-plastic impacts, e lies between zero and one and is a function of both the material properties and the velocity of impact. 

A 2D soft-sphere approach was first applied to gas-fluidized beds by Tsuji et al. (1993), where the linear spring-dashpot model—similar to the one presented by Cundall and Strack (1979) was employed. Xu and Yu (1997) independently developed a 2D model of a gas-fluidized bed. However in their simulations, a collision detection algorithm that is normally found in hard-sphere simulations was used to determine the first instant of contact precisely. Based on the model developed by Tsuji et al. (1993), Iwadate and Horio (1998) incorporated van der Waals forces to simulate fluidization of cohesive particles. Kafui et al. (2002) developed a DPM based on the theory of contact mechanics, thereby enabling the collision of the particles to be directly specified in terms of material properties such as friction, elasticity, elasto-plasticity, and auto-adhesion. 

The load-mass factor, K, transforms the actual dynamic system to the equivalent SDOF system. The value is usually between 2/3 and 3/4 and depends on the geometry, end conditions, support conditions, and range of behavior (i.e. elastic, elasto-plastic, or plastic). The maximum deflection, X, is then compared to the allowable ultimate deflection to determine the adequacy of the trial section. 

FIGURE 6.6 Typical Graphical Solution Chart For Elasto-Plastic SDOF System (from Biggs 1964)... 

Elasto-Plastic Region - The deformation range from formation of the first plastic hinge up to formation of the final plastic hinge (i.e. ultimate capacity). 

Sandorf, 1980 Whitney, 1985 Whitney and Browning, 1985). According to the classical beam theory, the shear stress distribution along the thickness of the specimen is a parabolic function that is symmetrical about the neutral axis where it is at its maximum and decreases toward zero at the compressive and tensile faces. In reality, however, the stress field is dominated by the stress concentration near the loading nose, which completely destroys the parabolic shear distribution used to calculate the apparent ILSS, as illustrated in Fig 3.18. The stress concentration is even more pronounced with a smaller radius of the loading nose (Cui and Wisnom, 1992) and for non-linear materials displaying substantial plastic deformation, such as Kevlar fiber-epoxy matrix composites (Davidovitz et al., 1984 Fisher et al., 1986), which require an elasto-plastic analysis (Fisher and Marom, 1984) to interpret the experimental results properly. 

Lhotellier, F.C. and Brinson, H.F. (1988). Matrix fiber stress transfer in composite materials Elasto-plastic model with an interphase layer. Composite Structures 10, 281-301. 

Elhers, W. (1991) Toward finite theories of liquid-saturated elasto-plastic porous media, Int. J. of Plasticity 7, 433-475... 

Dieses Verhalten hat zur Bezeichnung thermoplastics" bzw. elasto-plastics gefiihrt 49. 

For VVVr<10 no modification is obtained. For VJV,=25, Vneg is approximately equal to Vpos. For higher modulation amplitudes Vpos is very much larger than Vneg. The elasto-plastic response of the sample can be described by means of the parameter... 

Only in the last three years have some researchers begun to pay their attention to the structured surface and to parameters influencing the lithography with force-displacement curves (FDI) [266-268]. The big advantage of FDI is the possibility of gaining knowledge about the whole indentation process during FDI, the force and the indentation are known at every point, and not only stiffness and hardness, but also other important properties such as density, elasto-plastic behaviour, adhesion, time behaviour, etc. can be measured and calculated. 

The competition between the interfacial reactivities, the residual stresses and the elasto-plastic behavior of the components will be strongly dependent on the mechanical stability of the coating-substrate combination. Mechanical stability control has been assessed when making ceramic/metal junctions at high temperature (700°C - 1000°C) during which thick reaction zones tend to form by reactive diffusion in volume intermediate layers. ... 

Singamaneni S, Bertoldi K, Chang S, Jang J-H, Thomas EL, Boyce M, Tsukruk VV (2009) Instabilities and pattern transformation in periodic, microporous, elasto-plastic solids. ACS Appl Mater Interfaces 1 42-47... 

The elasto-plastic phase constitutes the transition to the seismic propagation mode. During this phase, the shock wave is gradually replaced by a wave with a more... 

Completely cured one-component polysulphide sealants are elasto-plastic and elastic in character. They have a movement accommodation factor of 20%-25%. These types of sealants are particularly suited for the perimeter sealing of window joints [Figure 7.2(a)], joints between precast concrete panels [Figure 7.2(b)], movement joints in brickwork where the movement is likely to be relatively slow, stone claddings, etc. The life expectancy for one-component sealants is, like that of two-component sealants, 20-25 years. 

The percent elongation at fracture varies with the grade, bar diameter and manufacturing source, ranging from 4.5 to 12 percent over an 8 in. gauge length. For most steels, the behavior is assumed to be elasto-plastic and the Young s modulus is taken as 29 x 10 psi. 

Simulation of the Elasto-Plastic Deformations in Compositionally Graded Metal-Ceramic Structures Mean-Field and Unit Cell Approaches ... 

The elasto plastic behavior of a compositionally graded metal-ceramic structure is investigated. The deformation under uniaxial loading is predicted using both an incremental Mori-Tanaka method and periodic as well as random microstructure extended unit cell approaches. The latter are able to give an accurate description of the local microfields within the phases. Furthermore, the random microstructure unit cell model can represent the interwoven structure at volume fractions close to 50%. Due to the high computational costs, such unit cell analyses are restricted to two-dimensional considerations. 

---