Creep effects

The example of the roof structure represents the simplest type of problem in static loading in that the loads are clearly long term and well defined. Creep effects can be easily predicted and the structure can be designed with a sufficiently large safety factor to avoid the probability of failure. 

As a melt is subjected to a fixed stress or strain, the deformation versus time curve will show an initial rapid deformation followed by a continuous flow. Elasticity and strain are compared in Fig. 8-9 that provides (a) basic deformation vs. time curve, (b) stress-strain deformation vs. time with the creep effect, (c) stress-strain deformation vs. time with the stress-relaxation effect, (d) material exhibiting elasticity, and (e) material exhibiting... 

An important aspect concerning the surface indentation mechanism is the creep effect shown by polymeric materials i.e. the time dependent part of the plastic deformation of the polymer surface under the stress of the indenter14-16. The creep curves are characterized by a decreasing strain rate, which can be described by a time law of the form... 

The radiation effect must disappear as the beam current goes to zero, as shown in Figure 5. The minimum beam current at which the effect could be observed was not determined in this study. The Soviet workers (II) found accelerated creep effects at absorbed dose rates as low as 16,000 rads per second. 

As for PMMA and CMIMx copolymers, the measurements have been performed to (Ta - 20 K) to avoid any creep effect. 

Beskok, A. and Karniadakis, G.E., Simulation of Heat and Momentum Transfer in Complex Micro Geometries, J. Thermophysics and Heat Transfer, 1994, 8(4), 647-655. Beskok, A., Karniadakis, G.E. and Trimmer, W., Rarefaction, Compressibility and Thermal Creep Effects in Micro-Elows, Proceedings of the ASME Dynamic Systems and Control Division, 1995, DSC-57-2, 877-892. 

The laminar gaseous flow heat convection problem in the slip flow region was solved both analytically and numerically for various geometries [3-6], The compressibility effects were included in [7],[8-11] and the results were compared with the experimental results of [12], Thermal creep effects were studied by [13], Exact solutions for flows in circular, rectangular, and parallel plate microchannels were given in [14-17],... 

Figure 5.27 Creep effects of a piezoelectric scanner on image topography. In slow scanning, the overshoot of the scanner occurs at two edges of a surface feature. (Reproduced with permission from PC. Braga and D. Ricci (eds), Atomic Force Microscopy, Humana Press. 2004 Humana Press.)...

Williamson R.L., Rabin B.H. and Byerly G., "Residual Stresses in Joined Ceramic-Metal Structures FEM Studies on Interlayer and Creep Effects", in 3rd International Symposium on Structural and Functional Gradient Materials, ed. Ilschner, B. and Cherradi, N., PPUR, Lausanne, (1994), 215-221. 

Lubricating oils for precision instruments and large clocks must have excellent oxidation stability, good anti-wear and anti-corrosion properties and retain their viscosity over a long period of time. Sometimes small amounts of gel-forming soaps, e.g. an aluminium soap, are added in order to reduce the creeping effect. 

Single Lap-Joint Specimen Test Results, is intended to give insight into the interpretation of the results from all the lap shear tests. At other points in ASTM Vol. 15.06 and in this chapter, reference is made to other standard tests that use shear-type specimens to explore moisture, and other environmental, fatigue, and creep effects in adhesive joints. 

Differences in design practices have in the past handicapped developments that could have reduced costs. For example, some difficulties with past design practices are evident in examining application of the ASME Code and Code Case N-47 to pool type LMFRs, such as Super Phenix. The design of Super Phenix resulted in considerably thinner components. This required different buckling rules. Super Phenix design creep effects were negligible... 

Covering of reinforcing bars with resin, apphed as an anti-corrosion protection, can lower their adhesion to cement paste. Worsening of adhesion occurs in the case of vinyl polychloride, but it does not occirr if the epoxy resins are used. However, some epoxy resins reveal the creep effect [56]. 

The variation oftensile strength with temperature in airfor a 1-D SiC/RBSN composite is shown in Fig. 4 [16]. The elastic modulus and matrix cracking strength decreases slowly with increase in temperature, but the ultimate tensile strength remains relatively constant from 25 to 600°C. Beyond this temperature it decreases due to oxidation of the carbon coating on the SiC fibers and creep effects. 

The specimens were installed in the testing machine by a hinge joint at each end as shown in Figure 8.10b (visible at bottom support). First, a load of 50 kN was applied to check the load distribution at the two ends. Subsequently, the specimens were loaded up to failure under displacement-control at a rate of l.Smmmin h The loading rate was selected to obtain an experimental duration of less than 15 min in order to minimize creep effects. All measurements were recorded at 5 s intervals [14]. 

In fact, concrete is not an ideal elastic material. Under constant stress, strain will increase as the time increases, which is known as creep effect. Creep is not only connected with load time T, but also connected with concrete s age t. The creep degree is usually be expressed as a variable by the formula as follow (Bofang Zhu. 1999) ... 

If the elasticity modulus and creep degree are given, and the creep effect of the aggregate is neglected, equivalent creep of concrete can be calculated from Eq. 13 ... 

Fig. 1-6. (a) Basic deformation vs. time curve, (b) Stress-strain deformation vs. time (creep effect), (c) Strain-stress deformation vs. time (stress-relaxation effect). 

Figure 3.17 Strain versus time representation of the stress-controlled programming performed at 263 kPa followed by free recovery. The creep effect in the foam during step 1 is shown in the subplot. Source [41] Reproduced with permission from Elsevier...

The unstretched film and the stretched film perpendicular to the stretched direction show monotonous expansion during the oxidation LS ES Pas and vice versa [14]. The result possibly indicates that the dopant ions settle between the polymer chains. In the expansion of the film perpendicular to the stretched direction, irreversible expansion, namely, a creeping effect, was observed even under light load during the redox cycles [14]. 

The coiq)lexity of such equations follows the attempts to describe the primary consolidation where the total voidage e dependmt on local con res e pressure and a secondary consolidation, the so-called creep effect. 

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