Relaxation load

Fig. 8.90 Load relaxation curves for a maraging steel stress corroded in 0.6 m NaCl at pH 2...

The load-relaxation method of Double-Torsion (DT) test is adopted in this study (Evans, 1972). A schematic illustration of a DT specimen is shown in Figure /, where the notations of the specimen are noted. In this study, the guide groove was set upward. 

This method gives a wide range of the data in the Krv diagram, generally lO -lO " m/s of the crack velocity, from only a single experimental run. Therefore, the load-relaxation method has been used in many studies on subcritical crack growth. 

In the load-relaxation method, AT/ and v are expressed as follows (Williams and Evans, 1973) ... 

After precracking, specimens were kept in environment of DT tests for about 20 hours, and then DT tests were carried out. In this study, in order to avoid hysteresis of the load-relaxation method (Sano, 1988), all of... 

Soft tissues subjected to repetitive loading, due to their viscoelastic properties, demonstrate creep and load relaxation. The loss of precision, speed, and control of the neuromuscular system induced by fatigue reduces the abihty of muscles to protect the weakened passive structure, which may explaiu many industrial, cHnical, and recreational injury mechanisms. These results further indicate the necessity of relating clinical protocols to the job and show how short-duration maximal isometric testing alone cannot provide the complex functional interaction of strength, endurance, control, and coordination. 

Firstly, on the tibial side, the fixation is performed in the metaphysis using an EndoButton , away from the proximal physis. Then, on the femoral side, after load relaxation is achieved by repeating the manual traction (manual max) of the tendon graft approximately ten times, fixation is performed in the epiphysis using a SutureButton set at 30 N of tension with 20° of knee flexion (Fig. 34.7). 

Determinations of wall rheological properties have shown marked differences between mutant and wild type. Extensibility (mm/g applied load) was measured as 0.11 for normals and 0.33 for slender seedlings whilst load/relaxation hysteresis values (under 10 g applied load) were respectively 3.3 X 10 and 8.4 X 10 J. Thus, there are marked differences in the apparent plasticity of the mutant cell wall, but these were abolished when measurements were made with killed tissue, suggesting that the differences were mediated by dynamic wall-based processes. 

Crack velocity versus stress intensity factor (V-Kf) curves were obtained by two general tests, so called constant loading and relaxation tests [4. In the load relaxation method, the pre-cracked specimen was subjected to fast loading, followed by subsequent stopping of the crosshead at a certain displacement. Hence, the crack propagation resulted in a load relaxation and the load versus time curve allows the determination of the V-Kj curve with a single experiment, for crack rates down to 10 m/s [4]. The stress intensity factor can be calculated from expression (2) pro-... 

When stress is not pure shear or pure hydrostatic pressure, one can always consider any stress state to be the sum of both former components. Under uniaxial loading, relaxation times should be multiplied by (Gy, Duffrene, Labrot, 1994 Guillemet and Gy, 1996)... 

Spring load relaxes quickly/Remaining load may be acceptable with fuel pellet-to-clad clearance (design case)... 

The small relaxations of the pull-out force during interruptions between successive steps of loading were taken into account and considered as the decrement of the slip proportional to the load relaxation. The interruptions were caused by the requirements of the speckle photography method itself and lasted several minutes each. The degree of load relaxation was relatively low (as average 4% of the global pull-out force... 

Figure 10.13 Schematic of a thermomechanical analysis (TMA) thermal expansion curve of an inorganic compound glass (solid curve). The geometrical construction to obtain the dilatometric softening point, A4g, at 10 i =Pas is given. The analogous TMA thermal expansion curve is shown (dotted curve) when a high-fictive-temperature glass sample is heated under load relaxation to a lower-fictive-temperature configurational arrangement can produce an observable contraction as illustrated.

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