Loading-unloading cycle

Fig. 40—Typical load-displacement curves during a loading/ unloading cycle. Applied load 1250 /liN, 1-Fe-N(5 nm)/Ti-N(2 nm), 2-Fe-N(20 nm)/Ti-N(2 nm).

Fig. 8. Dependence of the mechanical hysteresis AW (1, 2) of loading-unloading cycle and the change of internal energy AU (1, 2 ) on deformation1191. 1, 1 — filled PDMS rubber1221 2, 2 — star-SBS thermoelastoplastic1231...

Fig. 1.11 A typical load-unload cycle showing the parameters that can be measured which relate to the interface properties.

Instrumented nano-indentation (Nano Indenter II) under low applied loads (10 to 100 mN) for all the samples. The announced values are the average of the results of 6 indentations, each resulting from two consecutive load/unload cycles. Young s modulus is calculated by the software supplied with the indenter using data from the second unloading with the Berkovich pyramid indenter of known shape function. 

Figure 2.14. Loading-unloading cycle (force P vs penetration depth h) for amorphous PET (loading rate in 0.28 mN holding time at peak load is 6 s) (After Rores Balta Calleja, 1998.)...

After the initial H increase, as a result of the first loading-unloading cycle s — 5%), a drastic decrease of hardness (by 50%) is observed (Fig. 6.11 (a)). With further increasing deformation under stress (in the range s = 20-70%) H shows a very... 

Fatigue Life - Number of loading-unloading cycles of a specified type of material that can endure before failing in a fatigue test. 

Fig. 7.27 Optical transmission of a 40 nm thick Mg-Ni-Hx film evaporated on ITO/glass and capped with 5nm Pd during electrochemical loading/unloading cycles in...

Fig. 21 (a) Eight successive loading-unloading cycles for different maximum strains (2niax) as indicated on the curves. The dotted red curve represents the cycle conducted on a virgin gel sample Wmax = 5). The tests were conducted using HM PAAm hydrogel samples without SDS C17.3M = 2 mol%. (b) Idealized view of two successive cycles. From [34] with permission from Elsevier... 

Epoxy resin films were subject to various successive loading-unloading cycles including elongation, recovery, annealing and stress relaxation to study the reversibility of the orientation during relaxation processes (197). 

The maximum hysteresis behavior was relatively similar across the materials with the exception of that exhibited by the XLPE annealed material, which appeared to require lower loads to generate the same amount of stored energy in the specimen. The cumulative hysteresis plot for each material is shown in Figure 13.18. How the ability of a candidate bearing material to dissipate energy during a load-unload cycle relates to its suitability as a bearing component material will require furtiier study in conjimction with carefully monitored clinical application. 

The instantaneous resilient modulus is calculated using the instantaneous recoverable deformation that occurs during the unloading portion of one load-unload cycle. 

The cumulative strain ejooo.caic cent (%), is calculated after 1000 loading/unloading cycles using the following equation ... 

M. de Rosa, C. Santulli, F. Sarasini and M. Valente, Effect of loading-unloading cycles on impact-damaged jute/glass hybrid laminates. Po/ym. Compos. 30,1879-1887 (2009). 

Pig. 4.4 Residual elongation from one load-unload cycle at nominal strain-rate 0.0042 s from the data in Fig. 4.2. 3 comparison of polymers of types A, B and C. Material C is polymer PUci PTHF achieved by using a single step prepolymer synthesis using a melt mixture of the two isocyanates (MDI+DBDI) [61]. 

The range of polymers was designed to reveal the roles of choice of macrodiol and of chain extender in determining the performance as an elastomer. The SS were the polyether PTHF and polyester PEA or PBA, of molar mass 2 000 g/mol. The chain extenders used in the synthesis were EG, BG or DEG. Mechanical tests included load-unload cycles at constant rate of extension, with measurement of hysteresis and strain recovery, and stress relaxation tests. 

Example curves of nominal stress versus nominal strain for three load/unload cycles between zero stress and a nominal strain of 3 are given in Fig. 4.9 and 4.10 below for two polymers based on DBDI and MDI. As seen, notable features were the pronounced hysteresis, and unrecovered strain. 

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