Fatigue minimum stress

Stress ratio. Rates of corrosion fatigue crack propagation generally are enhanced by increased stress ratio R, which is the ratio of the minimum stress to the maximum stress. 

Figure 6.69 Venn diagram illustrating the interrelationship among stress corrosion, corrosion fatigue, and hydrogen embrittlement R — ratio of minimum stress to maximum stress (Phull)5...

Fig. 14a and b. Fatigue fracture surfaces of HIPS tested at 21 Hz in a tensile mode. The maximum stress was 17.2 MPa and the minimum stress was 3.4 MPa a Low magnification scan b High magnification scan... 

Fig. 44a ami b. Fatigue fracture surface of an ABS sample tested at 21 Hz in an alternating tensile mode at a maximum stress of 27,5 MPa and a minimum stress of zero a Low magnification scan b Higher magnification of region near source... 

R Ratio of minimum stress to maximum stress during fatigue loading S/N Stress/number of cycles (fatigue lifetime plot)... 

Layout of pipelines for ease of accessibility, proper drainage, anc minimum stress and fatigue... 

Minimum stress and fatigue from thermal or vibrational environment by providing well-designed flexibility... 

Since a frequently repeated minimum stress amplitude is needed to initiate corrosion fatigue in stainless steels in passivating solutions, it must be assumed that this load limit is connected with the mechanical stress capacity of passive layers. Only when particularly marked slip starts at one point on the surface will the layer be (racked. At that point, a constantly repetitive process begins, in which a new activation process at the same spot always follows repassivation. Each new passivation process consumes metal, deepens the corrosion, and increases the stress peak until, because of the constantly rising stress, repassivation is no longer possible. The resistance of passive metallic materials under fatigue conditions in electrolytes is therefore largely dependent on three factors ... 

Dynamic fatigue b more widefy recognized as a cause of firacture, and most handbools provide fritigue data in the form of S-N curves, as iUustrated in Figure 8.20. These curves usualfy flatten b ond 10 les, in which case it b possible to define a fatigue endurance limit, le. the minimum stress required to cause failure within 10 cycles. Both the static... 

Plot of stress, S, vs. number of cycles, N, required to cause failure of similar specimens in fatigue test. Data for each curve on the S-N diagram are obtained by determining fatigue life of a number of specimens subjected to various amounts of fluctuating stress. The stress axis may represent stress amplitude, maximum stress, or minimum stress. A log scale is usually used, especially for the N-axis. 

In mechanically induced fatigue tests, the stress or strain is oscillated about some mean stress (strain). If the peak or maximum stress is defined by no and the minimum stress by CTu, then the stress ratio is often defined hyR where... 

Maximum and minimum stress values obtained at the first cycle of the CLS are 222 MPa and 133 MPa respectively. As the cycles go on increasing, stress convergence is happening only after 25000 cycles, lliese maximum and minimum operating stress values are 240 MPa and 140 MPa respectively. Because of very low stress level, fatigue life of CLS is very high under simulated conditions. 

The stress intensity factor forms the central part of a great deal of the fracture and fatigue literature. Once the stress intensity factor is known, it is possible to determine the minimum stress value that would cause failure. This... 

Stress amplitude, alternating A test parameter of a dynamic fatigue test. One half the algebraic difference between the maximum and minimum stress in one cycle. 

Stress ratio is defined as the ratio of minimum stress to maximum stress. The rate of corrosion fatigue crack propagation is increased by an... 

The creep tests were conducted at three constant temperatures using a creep testing machine with a constant temperature chamber. The fatigue tests were conducted using an electro-hydraulic servo testing machine with a constant temperature chamber at five constant temperatures and two loading frequencies f=2 and 0.02 Hz) and a stress ratio (minimum stress/maximum stress), R = 0.05. Additionally, the fatigue tests were also conducted at R = 0.5 and three different temperatures. 

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