Slip hardening

Lin and Li [14] modelled the pull-out resistance of a slip hardening fibre by assuming a linear relation between the interfacial shear stress x and the slip A ... 

Z. Lin and V.C. Li, Crack bridging in fiber reinforced cementitious composites with slip-hardening interfaces , J.Mech. Phys. SoUds S, 1997, 763-787. 

PVA fibres tend to rupture instead of pull-out of a cementitious matrix, due to the strong chemical bonding and the resulting slip-hardening response during pullout [133]. Li etal. [134] were able to produce composites with an ultimate tensile strain exceeding 4% and a tensile strength of 4.5 MPa, with a fibre volume of only... 

The different types of high performance systems will than be treated separately, based on classification in terms of the performance and the strategy to achieve it, to include the following topics monofibre systems with normal strength matrix, monofibre systems with high strength matrix, hybrid FRC, slip hardening fibres and FRC with polymer-cement matrices. 

An additional means for inducing slip hardening bond behaviour is based on densification in the matrix around the fibre, in combination with the presence of fine fillers, as has already been demonstrated in Section 12.2. A demonstration of the efficiency of this means was provided in Section 12.2.2 showing the marked influence of matrix modification in high strength cementitious systems, to obtain bond values with straight steel fibres exceeding 10 MPa. 

A.E. Naaman, Fiberwith slip hardening behavior , in H.W. Reinhardt artd A.E. Naaman (eds) Third International Workshop on High Performance Fiber Reinforced Cement Composites (HPFRCC 3), RILEM Publications, Bagneux, France, 1999, pp. 371-385. 

It was ironic that a few years later, Rosenhain began to insist that the material inside the slip bands (i.e., between the layers of unaffected crystal) had become amorphous and that this accounted for the progressive hardening of metals as they were increasingly deformed there was no instrument to test this hypothesis and so it was unfruitful, but none the less hotly defended ... 

Liquid resin-based systems which, like the chemical surface hardeners, penetrate into the surface of a concrete topping or directly finished slab and protect the acid-susceptible cement matrix from attack and, at the same time, strengthen the surface of the concrete are now being increasingly used. These in-surface seals leave the slip resistance of the concrete floor virtually unchanged but the treated floors are easier to clean and are more durable. 

It is partly because of the variable effect of hydrogen (giving both softening and hardening, according to the nature of the slip) that the extrapolation of model experiments on very pure iron to predict the behaviour of commercial materials is so difficult. It is further hindered by the ability of dissolved hydrogen to modify the dislocation structure of a straining material. 

If slip-line fields do not control plastic indentation, what does The answer is not the beginning of the plastic deformation, but the end of it. The end means after deformation hardening has occurred. That is, it is not the initial yield stress, Y0, that controls indentation, but the limiting yield stress, Y. This is... 

In textbooks, plastic deformation is often described as a two-dimensional process. However, it is intrinsically three-dimensional, and cannot be adequately described in terms of two-dimensions. Hardness indentation is a case in point. For many years this process was described in terms of two-dimensional slip-line fields (Tabor, 1951). This approach, developed by Hill (1950) and others, indicated that the hardness number should be about three times the yield stress. Various shortcomings of this theory were discussed by Shaw (1973). He showed that the experimental flow pattern under a spherical indenter bears little resemblance to the prediction of slip-line theory. He attributes this discrepancy to the neglect of elastic strains in slip-line theory. However, the cause of the discrepancy has a different source as will be discussed here. Slip-lines arise from deformation-softening which is related to the principal mechanism of dislocation multiplication a three-dimensional process. The plastic zone determined by Shaw, and his colleagues is determined by strain-hardening. This is a good example of the confusion that results from inadequate understanding of the physics of a process such as plasticity. 

The presence of grain boundaries also affect slip in the material even after plastic deformation has commenced. A phenomenon known as strain hardening, or work hardening or cold working, is the result of constrained dislocation mobility and increased... 

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