Fatigue Failure Resulting from Variable Loading

What are the three stages that characterize a fatigue failure?

Which fatigue-life method is most traditional, easiest to implement for a wide range of applications, and based on nominal stress levels and empirical data?

What is the estimated rotating-beam endurance limit, S'e, for a steel with an ultimate tensile strength (Sut) of 180 kpsi?

In the Marin equation for the endurance limit, Se = ka*kb*kc*kd*ke*S'e, what does the factor 'ka' represent?

A steel component has a machined surface and an ultimate tensile strength of 100 kpsi. Using the curve-fit parameters from the text, what is the estimated surface factor, ka?

What is the relationship between the fatigue stress-concentration factor (Kf), the theoretical stress-concentration factor (Kt), and the notch sensitivity (q)?

A steel shaft has an ultimate strength of 690 MPa and a shoulder fillet radius of 3 mm. A theoretical stress concentration factor Kt of 1.65 is determined. Using the Neuber constant method from the text, what is the estimated fatigue stress concentration factor Kf?

For a component under fluctuating stress, if the mean stress (σm) is positive, which infinite-life fatigue criterion is generally considered simple and conservative for design purposes?

A steel bar has a fully corrected endurance limit Se of 40 kpsi and an ultimate strength Sut of 100 kpsi. It is subjected to an alternating stress σa of 12 kpsi and a mean stress σm of 36 kpsi. What is the factor of safety for infinite life according to the Goodman criterion?

The Palmgren-Miner rule is used to assess what aspect of fatigue?

According to the linear damage rule (Miner's rule), if a part is subjected to n1 cycles at stress level σ1 where the life to failure is N1, and n2 cycles at stress level σ2 where the life to failure is N2, when is failure predicted to occur?

What is the primary physical mechanism that leads to the initiation of a fatigue crack?

What are the characteristic visual features on a Stage II fatigue fracture surface that indicate the progression of the crack?

For a non-rotating round bar in bending, the size factor kb is determined using an effective diameter, de. What is the relationship between de and the actual diameter d?

What is the recommended Marin load factor, kc, for a part subjected to pure axial loading?

In the Paris equation for crack growth, da/dN = C*(ΔKI)^m, what does Region II on the crack growth rate curve represent?

Using the conservative values for ferritic-pearlitic steels from the text, what are the material constants C and m for the Paris equation when using units of in/cycle and kpsi*sqrt(in)?

What is the primary characteristic of a 'repeated stress' condition in constant amplitude loading?

What is the defining characteristic of low-cycle fatigue?

For a steel with an ultimate strength (Sut) of 90 kpsi, what is the estimated fatigue strength fraction, f, used to find the fatigue strength at 1000 cycles?

What is the primary reason that aluminum alloys typically do not exhibit an endurance limit?

When checking for first-cycle yielding in a fluctuating stress scenario (σa + |σm|), which strength property should be used for comparison?

The Morrow fatigue criterion is similar to the Goodman criterion but replaces the ultimate strength (Sut) with what material property?

What is a major advantage of the Smith-Watson-Topper (SWT) criterion compared to criteria like Goodman or Gerber?

For a component made of a brittle material like cast iron, how does the first-quadrant fatigue failure locus typically appear on a fluctuating-stress diagram?

When analyzing a combination of fluctuating bending and torsional loads on a shaft, how are the alternating and mean stresses combined to find an equivalent stress?

According to Manson's method for cumulative damage, what is the key difference from the Palmgren-Miner method regarding the S-N diagram?

What is the reliability factor (ke) for a desired reliability of 99.9 percent, assuming an 8 percent standard deviation of the endurance limit?

Why must a hardened steel washer be used under a bolt head in a fatigue-loaded joint?

What is the effect of a compressive mean stress on the fatigue life of a ductile component, according to the experimental data shown in the text?

A steel has a tensile strength of 80 kpsi and is used at a steady temperature of 750 degrees F. If only the room temperature strength is known, what is the estimated tensile strength at the operating temperature?

For a steel with Sut > 200 kpsi (or 1400 MPa), what is the estimated rotating-beam endurance limit, S'e?

If a fatigue analysis using the Goodman criterion results in a factor of safety (nf) of 0.69, what does this predict about the component's life?

To estimate the finite life of a component with a fluctuating stress, an equivalent completely reversed stress (σar) is calculated. Using the Morrow criterion, what is the formula for σar?

The Walker fatigue criterion, Se = (σm + σa)^(1-γ) * σa^γ, is a more generalized version of which other criterion?

When adapting fatigue failure criteria for a pure shear stress case, the ultimate tensile strength (Sut) is replaced with the ultimate shear strength (Ssu). What is the recommended conservative estimate for Ssu?

What is the primary distinguishing characteristic of a 'fail-safe' design philosophy?

A 1050 HR steel with Sut = 90 kpsi has a polished rotating-beam specimen endurance limit S'e of 45 kpsi and a fatigue strength fraction f of 0.86. What is the expected life in cycles for a completely reversed stress of 55 kpsi?

What is the primary reason for the reduction in fatigue strength due to electrolytic plating like chromium or nickel plating?

What phenomenon, resulting from microscopic motions of tightly fitting parts, involves surface discoloration, pitting, and can lead to eventual fatigue failure?

What is the notch sensitivity, q, for all grades of cast iron recommended in the text?

What is the primary trade-off when choosing between the stress-life and strain-life fatigue methods for high-cycle fatigue applications?

In the context of the strain-life method, what is the Basquin equation?

If a fatigue analysis of a rotating shaft subjected to a bending moment of 150 N-m and a torque of 120 N-m results in an alternating von Mises stress of 104 MPa, and the material's fully corrected endurance limit is 148 MPa, what is the fatigue factor of safety for infinite life?

In a fluctuating-stress diagram, what do the Langer lines represent?

Which infinite-life fatigue criterion is specified in the ANSI/ASME Standard B106.1M-1985 for the design of transmission shafting?

What is the primary deficiency of the Goodman criterion when used to estimate an equivalent completely reversed stress for finite-life calculations?

In Basquin's equation, Sf = a * N^b, what do the constants 'a' and 'b' represent on a log-log plot of the S-N curve?

If a steel has an ultimate strength of 70 kpsi, the estimated endurance limit S'e is 35 kpsi. The fatigue strength at 1000 cycles is found to be 0.9 * 70 = 63 kpsi. What is the value of the constant 'b' in the Basquin equation for this steel?

What is the primary reason to use a damage-tolerant design approach instead of a fail-safe approach?