Fatigue humidity effects

T. Ogasawara and Y. Mabuchi, Effect of Humidity and Cyclic Loading Condition on Fatigue behavior of Silicon Nitride , J. Ceram. Soc. Jap., Int. Edition, 101, 1993, 1122-1127. 

The first effect is caused by the modification in time of utilisation properties of material from which the object was made, under the action of the external medium factors (light, heat, oxygen, humidity, etc) that constitute component parts of the ageing process. The second factor is based on the appearance and accumulation of the material fatigue, under the action of mechanical energy. 

Figure 10.24 Effect of pre-conditioning on coupons undergoing tensile fatigue (a) carbon/epoxy (b) glass/epoxy (c) aramid/epoxy 65% rel. humidity for three months at 20°C (Jones et al.).

Dynamic mechanical thermal analysis (DMTA) has also been used by Brinson, et al.,t l to determine the suitability of the technique for evaluating damage in the adhesive bond from the viscoelastic properties of bonded beams and for evaluating the effects of various environmental conditions and various surface treatments. The authors considered that if the bond becomes damaged (either adhesive and/or interphase) due to excessive load, fatigue, moisture, or corrosion, it would seem likely that dissipation mechanisms or loss modulus and tan 5 would change. Therefore, they used DMTA to measure the viscoelastic properties of beams with simulated flaws and beams taken from lap specimens, which had been exposed to humidity and/or corrosion for extended periods. 

Finally, the main components in the thermal environment are air temperature, humidity and air movement. Considering temperature, it can, of course, cause problems when either too high or too low. Moderately high temperatures can cause effects such as irritability, loss of concentration, increased errors, loss of performance in heavy work and intense fatigue, whereas moderately too low temperatures can cause less mobiUty in the hands/feet, slowing down of manrral skills, increased clumsiness and a decreased sense of touch. 

Orlando, FI., 21st-23rd Sept. 1999, paper 183 PRACTICAL METHOD TO ELIMINATE FLAWS CAUSED BY CARBON BLACK SURFACE HUMIDITY - ITS EFFECTS ON IMPROVING MIXING PROCESS AND RUBBER COMPOUND FATIGUE PROPERTIES... 

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