Failure cycle number

Some viscoelasticity results have been reported for bimodal PDMS [120], using a Rheovibron (an instrument for measuring the dynamic tensile moduli of polymers). Also, measurements have been made on permanent set for PDMS networks in compressive cyclic deformations [121]. There appeared to be less permanent set or "creep" in the case of the bimodal elastomers. This is consistent in a general way with some early results for polyurethane elastomers [122], Specifically, cyclic elongation measurements on unimodal and bimodal networks indicated that the bimodal ones survived many more cycles before the occurrence of fatigue failure. The number of cycles to failure was found to be approximately an order of magnitude higher for the bimodal networks, at the same modulus at 10% deformation [5] ... 

Power loss Number of cycles Number of alternating loads causing failure... 

Figure 14. Strain-to-failure versus number of cycles for two types of MEAs one with a reinforced composite membrane (Gore-5510) and the other with regular PFSA membrane (N- 111). The samples are cycled from 30 to 80% RH and from 80 to 120% RH.37...

Figure 15. The trend of average strain-to-failure versus number of cycles for two types of MEAs tested.37...

Cyclic loading of contractive specimens of both sand (a) and clay (b) leads to failure when pore pressures increase sufficiently. Numbers indicate cycle number. (After Sangrey, D.A. et al.. Cyclic loading of sands, silts and clays. Proceedings of the ASCE Special Conference on Earthquake Engineering and Soil Dynamics, Pasadena, CA, 2, pp. 836-851,1978. Reprinted with permission of ASCE.)... 

Figure 5.8 Variation of peak stress level for failure with number of cycles to failure for three laminates investigated...

Figure 5.15 Fatigue test of cross-ply laminates at high load levels. All specimens run to failure. Lay up [Oj, 9O2, O2, 9021s, resin LY 556, MY 720 (50 50), R = 0.1, f = 10Hz. (a) Temperature change versus number of load cycles, (b) development of transverse cracks versus number of load cycles. Number of transverse cracks taken from X-ray radiographs...

Flex life n. Informally, the number of bending-reversal cycles causing a part to fail in a particular service. Most specifically, the number of cycles to failure of a test specimen repeatedly bent in a prescribed manner. The ASTM test for plastics is D 671. The specimen, molded or cut from sheet, is subjected to load reversal at 30 Hz at a predetermined level of outer-fiber stress until it either fails or the test is discontinued. By setting up different stresses for successive specimens, one can develop a graph of stress at failure versus number of cycles to failure (usually plotted on semi-logarithmic coordinates), i.e., the flex-life curve of fatigue curve. 

S/N curve Abbreviation for stress at failure versus number of cycles (curve). 

Samples were subjected to dynamic linear testing to failure. The number of cycles to failure was plotted against the cable spacing (Fig. 21.17). 

Statement 5. The maximum and minimum problems, providing the maximum and minimum values of the variation of amount of material in the intermediate storage in any failure cycle, are reduced to finding maxima and minima of finite number of functions. 

Statement 7. Any process can be built up from a random sequence of functions related to the failure cycles of finite number. By means of simulation and statistical evaluation of the results of simulation runs the storage can be sized at a given significance level. 

Then, the number of the possible vectors of delay times is equal 12 that are given in Table 1. If the first failure of the unit I occurs in the V , 2" or period of operation, respectively, then 36 different sub-process variations of the changes of the amount of material in the storage during the first failure cycle are possible. Three such subprocesses, corresponding to the vector of delay times (2,0,1,1), are shown in Fig.2, the... 

Solution The process for solving this problem is as follows. The experimentally obtained qualification data (presented in Table 59.4) must be mapped into number of power cycles to failure and number of minicycles to failure. These estimates assume that only power cycles occur and that only minicycles occur (that is the underlying assumption when mapping the experimental data to the end-use power cycle and minicycle conditions). After mapping the experimental data into field conditions. Miner s rule is employed to assess the number of cycles to fail based on the simultaneous occurrence of both power cycles and minicycles throughout the package lifetime. 

Nminiactmi = uctual uumbcr of minicycles that occur before failure Nminioniy = number of minicycles to fail if only minicycles occur K = number of minicycles that occur per power cycle... 

FIG. 14 Peak tensile stress is plotted against cycle number for 96.5Pb-3.5Sn solder. Failure was defined as the cycle number that exhibited the maximum peak stress as indicated by the arrow. The total strain range was 0.75% and temperature was 25°C. To stabilize the microstrueture, the sample was heated to 150°C for 2 hrs and then aged at room temperature for 9 days. (From Ref. 16.)... 

FIG. 19 Cycle number to failure is plotted vs. frequency for Sn-Ag and Sn-Zn eutectic solders. Data for 62Sn-36Pb-2Ag solder is also shown. The temperature was 25 °C and total strain range was 1 %. 

N niunber of load reversals to failure (N = number of cycles to failure)... 

Fig. 16. Maximum shear stress at bore vs number of cycles to failure for specimens of EN25 T steel at various k values. +, / = 1.2 Q = 1-4 ...

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