Hysteresis heating

AH three systems give similar tensile strength, elongation, and hardness properties. Hysteresis (heat buildup) measured by tan 5 shows an advantage for conventional and semi-EV systems and unaged fatigue follows the expected pattern. 

An example will be given to show how dynamic loading can lead to product failure by hysteresis heating. When this condition exists the failure will be catastrophic rather than... 

S.P. Street, R. (1992) Evaluation of ferromagnetic materials for low frequency hysteresis heating of tumours. Phys. Med. Biol. 37 293-299... 

Plateau Pressure/Temperature Plateau Slope Hysteresis Heat of Reaction Hydrogen Capacity Volume Change Rate of Decrepitation Ease of Activation Kinetics of Reaction Tolerance to Gaseous Impurities Chemical Stability (Disproportionation)... 

The hysteresis heating failure occurs more commonly in TP type members subject to dynamic loads. An example is a plastic gear. With the gear teeth under load once per revolution, it is subjected to a bending load that transmits the power from one gear to another. Another example is a link that is used to move a paper sheet in a copier or in an accounting machine from one operation to the next. The load may be simple tensile or compressive stresses, but more commonly it is a bending load. 

Gunmathan et at studied the wear performance of the clay-polyamide hybrid gears produced by melt intercalation and reported that the wear resistance of the nanocomposite gears is excellent and hysteresis heat generation is also low, which may lead to enhanced gear life [110]. 

Suwanwatana W, Yarlagadda S and Gillespie J W Jr. (2006) Influence of particle size on hysteresis heating of nickel particulate polymer films. Compos Sci Technol 66 2825-2836. 

Materials used such as stifFer plastics can reduce hysteresis heating. Crystalline TPs for example (the popularly used acetal and nylon) can be stiffened by 25 to 50% with the addition of fillers and reinforcements. Others used include ABS, polycarbonates, polysulfones, phenylene oxides, polyurethanes, and thermoplastic polyesters. Additives, fillers, and reinforcements are used in plastics gears to meet different performance requirements (Chapter 1), Examples include glass fiber for added strength, and fibers, beads, and powders for reduced thermal expansion and improved dimensional stability. Other materials, such as molybdenum disulfide, polytetrafluoroethylene (PTFE), and silicones, may be added as lubricants to improve wear resistance. 

Note Optimization = 3 factor, 2,2 and 2-level full factmial design—8 compounds and experiments. Responses (properties) to be measured Dynamic hysteresis heat resistance, 1008 hat 120°C resistance to application fluids, 70 h at 120 C extrusion processing. 

Elastomers are often compounded with finely divided solids to reinforce the rubber and to reduce costs. The most important fillers are carbon blacks, silica and silicates, clays and whiting (calcium carbonate). " The particles are the source of reinforcement through their interactions with the rubber, among themselves and with the chemistry of the cross-linking process. Abrasion resistance, tear strength and tensile strength are simultaneously improved. However, hysteresis, heat build-up and compression set (permanent deformation) are also known to increase as the reinforcing ability of the filler becomes more pronounced. 

Summarizing the above observations one has to conclude that no distinctive fatigue mechanism - other than hysteresis heating - is operating when highly ori-... 

This hysteresis heating leads to a noticeable temperature rise. At low test frequencies and low stress levels the temperature increase of the test specimen generally approaches a finite value.. A PA 6 sample for instance fatigued at 50 Hz, at a constant stress amplitude of 8 MN m , and at an ambient temperature of 21 °C, assumed a stable temperature of 27 °C after some 10 cycles [139—140]. At this temperature mechanical energy input and thermal energy loss were in equilibrium. 

In addition hysteresis heating occurs in the strained craze material. Both effects combine to give rise to a distinct frequency sensitivity of A for a variety of materials such as PC and PMMA [219, 220], and PPO, PVC, PA 66, PC, PVDF, and PSU [220]. As has been noted by Skibo et al. [220] the frequency sensitivity varies with temperature. It reaches a maximum at that temperature where the external (fatigue) frequency corresponds to the internal segmental jump frequency (of the jS-relaxation process). 

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