Mechanical bending

Both time-related failure rates and demand-related failure rates can apply to and be reported for many pieces of equipment. Both types of rates are included in some of the data tables in Chapter 5. If a piece of equipment is in continuous service, such as a transformer, the failure rate is dominated by time-related stresses compared to demand-related stresses. Other failure rates may be dominated by demands. Take a piece of wire and repeatedly bend it. With each bend its probability of catastrophic failure increases. In a relatively short time, if the bending is continued, the wire will fail. On the other hand, the same wire could be installed in a manner that would prevent mechanical bending demands. In this case, the occurrence of catastrophic wire breakage would be remote. In the first instance, the failure rate is dominated by demand stresses and in the second by time-related stresses, such as corrosion. 

Equation 28 states, that co is proportional to t. The effect of the thickness of the gel film on the frequency of the first resonance mode has been investigated. When the buoyancy is taken into account, the experimental results have quantitatively followed Eq. 28. It has been found that the buoyancy plays an important role in the occurrence of the electric field-associated vibration of gel film. The vibration of the gel film in an electric field has thus roughly analyzed as a mechanical bending vibration of a uniform cantilever beam. 

Neural implants need also to be biostable in a wet environment. Therefore, mechanical bending tests were performed in physiologic saline solution at room temperature to simulate loading stresses of movements. In dynamic tests the electrodes were fixed at the ends and bent for 130,000 times at an angle of 120° with a repetition frequency of /3 Hz. The devices remained stable. No cracks or... 

SiC-coated vessel with potential use for thermal chemical reactions for hydrogen processes. Other tests conducted at JAERI examine the corrosion exposure in boiling sulfuric acid. Mechanical bending tests are planned at the Research Center Jiilich. 

Another type of behavior is obtained with thermoreversible gels like agarose. Electron microscopy has shown that the network structure of these gels consists of fibers made from many polymer chains. In such gels, elasticity doesn t come from the entropy of the chains, as in the case of covalently cross-linked polymers, but from the mechanical bending elasticity of the fibers. The elastic moduli are about 10 times larger than those of entropic... 

Figure 3. Time dependence of the electric potential change at the applying ("+ ") and removing of mechanical bending stress...

Figure 17. Response of the catheter-protected porphyrinic sensor to changing fluid pressure (a), to mechanically bending the active tip of the sensor at a frequency of 3Hz (b), and to the ECG signal (c). The vertical bars represent the equivalent current that would be generated by the porphyrinic sensor in the 100 nM NO ((a), lower tracing) or 50 nM NO (b).

Cracks or other such flaws present in the adherend surface may also serve as foci for crack propagation under stress leading to apparent adhesive failure. In joints or welds that undergo cyclic mechanical (bending) or thermal (hot-cold-hot cychng) stress may also develop stress cracks at or near a joint or... 

IPMCs that are subjected to a mechanical bending produce voltage difference on the electrodes. The bending causes anion density to increase on the compressed side, and to decrease on the stretched side. Also, cation recombination occurs. This causes the electric field and upon shorting, an electric current. 

Now, given the properties and the various ways for manipulating the way of actuation, a physics-based control model was developed and implemented. The model is capable of predicting both actuation output in response to an electrical stimulus and also sensing output in response to a mechanical bending. The model was validated experimentally and can be used for control purposes. 

Almost flat primary mirrors are tracking the sun such that they reflect the direct sun rays to a stationary receiver. The primary mirrors can be made of flat glass because the slight curvature, which is needed for a focal length of several meters, can be applied by mechanical bending. 

Use upright neutral working postures and proper body mechanics. Bend your legs, not your back. 

Kozo Harada, Shinji Baba, Qiang Wu, Hironori Matsushima, Toshihiro Matsunaga, Yasumi Uegai, Michitaka Kimura, Analysis of Solder Joint Fracture under Mechanical Bending Test, Electronic Components and Technology Conference, 2903 pp. 1731-1737. 

Thns, mechanical bend strength is a fnnction of the solder metallnrgy and the snrface finish nsed. These resnlts indicate that SnAgCn solder joints are stiffer and have a higher average... 

Thus, mechanical bend strength is a function of the time after reflow along with solder metallurgy and surface finish. The underlying failure mechanisms have not been understood clearly enough to explain the dependence on time after reflow. 

The mechanical bending energy is associated with the rigidity of the polyelectrolyte I = 2lp and is therefore given by the Kratky-Porod energy [180] ... 

The mechanical bending energy follows from (58) by parametrization in terms of spherical coordinates. The contour s of a circle is related to its angle via s = ad. Hence, we obtain for semicircles ... 

Cai, J., Cizek, K., Long, B. et al. (2009) Flexible thick-film electrochemical sensors impact of mechanical bending and stress on the electrochemical behavior. Sens. Actuators, B, 137, 379. 

Figure 11.5 Comparison of elasticity and capillarity. The figure on the left shows a thin plate that is bent into a curved shape of radius R the right figure shows two plates covered by a thin liquid layer, represented by the solid lines. Balancing mechanical bending energy (left) and interfacial energy [right] leads to the elastocapillary length Lee = /Eh /y.

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