Axial strain

Fig. 5.2 Comparison of creep behavior and time-dependent change in fiber and matrix stress predicted using a 1-D concentric cylinder model (ROM model) (solid lines) and a 2-D finite element analysis (dashed lines). In both approaches it was assumed that a unidirectional creep specimen was instantaneously loaded parallel to the fibers to a constant creep stress. The analyses, which assumed a creep temperature of 1200°C, were conducted assuming 40 vol.% SCS-6 SiC fibers in a hot-pressed SijN4 matrix. The constituents were assumed to undergo steady-state creep only, with perfect interfacial bonding. For the FEM analysis, Poisson s ratio was 0.17 for the fibers and 0.27 for the matrix, (a) Total composite strain (axial), (b) composite creep rate, and (c) transient redistribution in axial stress in the fibers and matrix (the initial loading transient has been ignored). Although the fibers and matrix were assumed to exhibit only steady-state creep behavior, the transient redistribution in stress gives rise to the transient creep response shown in parts (a) and (b). After Wu et al 1...

Fibre type Failure strength (GPa) Failure strain Axial modulus (GPa) Density (kg/ m3)... [Pg.118]

The photo-dehydro-Diels-Alder reaction provides an access to 1-phenylnaphthale-nes, 1,1-binaphthyls, A-heterocyclic biaryls, and naphthalenophanes. The PDDA reaction proceeds through a multistage mechanism with biradicals and cycloallenes as intermediates. Again, the intramolecular photo-dehydro-Diels-Alder reaction of diyne (65) produced strained axially chiral (l,5)naphthalenophanes (66) in moderate yields (Scheme 20). " ... [Pg.462]

The slope s absolute value of linear section on the radial strain—axial strain curve is defined as Poisson s ratio. The data of confining pressure and Poisson s ratio from Table 1 are also plotted in Figure 6. Fitting analysis is conducted as following ... [Pg.423]

The specimens may then be tested by methods outlined in ASTM G 36, ASTM G 41, ASTM G 44, or ASTM G 50. A constant strain condition is maintained in the U-bend geometry specified in ASTM G 30 varying the bend radius controls the strain level. ASTM G 39 describes the bent beam SGG test specimen, which is similar in concept to the U-bend specimen, but is subject only to elastic strain. Axial loaded SGG test specimens are covered in ASTM G 49 and can be tested under constant strain, constant load, or varying strain rates. All of the SGG specimen preparation procedures for sheet and strip reqiiire careful sampling, due to the anisotropy introduced by rofllng specification of rolling direction on each specimen is mandatory. [Pg.562]

Let us assume that stress gradient in axial direction is present but smooth. Then we can use a perturbation method and expand the solution of equation (30) in a series. The first term of this expansion will be a solution of the plane strain problem and potential N will be equal to zero. The next terms of the stress components will contain potential N also. [Pg.138]

Van der Waals strain between hydrogen of axial CH3 and axial hydrogens at C 3 and C 5... [Pg.121]

As m the 1 4 dimethylcyclohexanes the 6 kJ/mol (1 5 kcal/mol) energy difference between the more stable (trans) and the less stable (cis) stereoisomer is attributed to the strain associated with the presence of an axial methyl group m the cis isomer... [Pg.127]

Partially Plastic Thick-Walled Cylinders. As the internal pressure is increased above the yield pressure, P, plastic deformation penetrates the wad of the cylinder so that the inner layers are stressed plasticady while the outer ones remain elastic. A rigorous analysis of the stresses and strains in a partiady plastic thick-waded cylinder made of a material which work hardens is very compHcated. However, if it is assumed that the material yields at a constant value of the yield shear stress (Fig. 4a), that the elastic—plastic boundary is cylindrical and concentric with the bore of the cylinder (Fig. 4b), and that the axial stress is the mean of the tangential and radial stresses, then it may be shown (10) that the internal pressure, needed to take the boundary to any radius r such that is given by... [Pg.79]

Resistance to axial compressive deformation is another interesting property of the silk fibers. Based on microscopic evaluations of knotted single fibers, no evidence of kink-band failure on the compressive side of a knot curve has been observed (33,35). Synthetic high performance fibers fail by this mode even at relatively low strain levels. This is a principal limitation of synthetic fibers in some stmctural appHcations. [Pg.78]

Expansion strains may be taken up in three ways by bending, by torsion, or by axial compression. In the first two cases maximum stress occurs at the extreme fibers of the cross section at the critical location. In the third case the entire cross-sectional area over the entire length is for practical purposes equally stressed. [Pg.987]

The axial tensile strength of many woods is around 100 MPa - about the same as that of strong polymers like the epoxies. The ductility is low - typically 1% strain to failure. [Pg.283]

Example 23 A cylindrical polypropylene tank with a mean diameter of 1 m is to be subjected to an internal pressure of 0.2 MN/m. If the maximum strain in the tank is not to exceed 2% in a period of 1 year, estimate a suitable value for its wall thickness. AVhat is the ratio of the hoop strain to the axial strain in the tank. The creep curves in Fig. 2.5 may be used. [Pg.58]

The modulus term in this equation can be obtained in the same way as in the previous example. However, the difference in this case is the term V. For elastic materials this is called Poissons Ratio and is the ratio of the transverse strain to the axial strain (See Appendix C). For any particular metal this is a constant, generally in the range 0.28 to 0.35. For plastics V is not a constant. It is dependent on time, temperature, stress, etc and so it is often given the alternative names of Creep Contraction Ratio or Lateral Strain Ratio. There is very little published information on the creep contraction ratio for plastics but generally it varies from about 0.33 for hard plastics (such as acrylic) to almost 0.5 for elastomers. Some typical values are given in Table 2.1 but do remember that these may change in specific loading situations. [Pg.58]

Note that the ratio of the ratio of the hoop stress (pR/h) to the axial stress (pR/lh) is only 2. From the data in this question the hoop stress will be 8.12 MN/m. A plastic cylinder or pipe is an interesting situation in that it is an example of creep under biaxial stresses. The material is being stretched in the hoop direction by a stress of 8.12 MN/m but the strain in this direction is restricted by the perpendicular axial stress of 0.5(8.12) MN/m. Reference to any solid mechanics text will show that this situation is normally dealt with by calculating an equivalent stress, Og. For a cylinder under pressure Og is given by 0.5hoop stress. This would permit the above question to be solved using the method outlined earlier. [Pg.59]

Fig. 3.13 Variation in direct and shear strains for unidirectional composite loaded axially...

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