What causes fatigue crack?
Fatigue crack in ductile metals is caused by cyclic plastic deformation at the crack tip, which is governed by the plastic properties of the material and the crack driving force, the stress intensity range ΔK, or the cyclic J-integral.
What causes fatigue cracking in metal?
The crack initiation point can be stress concentration caused by an embedded particle, a high-stress region due to shaft misalignment, high temperature, and so forth. The fatigue crack may seem to open in the direction of rotation. Pieces of metal may be carried in the direction of the shaft rotation.
What is the relation between fatigue life and crack size?
Fatigue life can be divided into an initiation period and a crack growth period. Crack growth equations are used to predict the crack size starting from a given initial flaw and are typically based on experimental data obtained from constant amplitude fatigue tests. .
What is crack propagation?
Crack growth is defined as the widening, lengthening or increase in the number of cracks on a particular surface. Crack growth is also known as crack propagation.
What is fatigue mechanism?
Fatigue is a failure mechanism that involves the cracking of materials and structural components due to cyclic (or fluctuating) stress. While applied stresses may be tensile, compressive or torsional, crack initiation and propagation are due to the tensile component.
What type of stresses cause fatigue failure?
What term is used for crack growth during fatigue?
Fatigue crack growth testing may also be known as crack propagation testing or da/dN testing.
What is fatigue crack growth rate?
Fatigue Crack Growth Rate (da/dN) Testing is designed to determine the rate of cracking under specified loading conditions once a flaw has been initiated in the specimen. The graph of Cyclic Stress is plotted against the Crack Growth Rate, with stress intensity being the controlling variable.
What are 3 types of fatigue?
There are three types of fatigue: transient, cumulative, and circadian: Transient fatigue is acute fatigue brought on by extreme sleep restriction or extended hours awake within 1 or 2 days.
What is the mechanics of fatigue crack propagation?
The main subject of mechanics of fatigue crack propagation is to establish the equation of crack propagation as a function of a loading parameter under complex service conditions. Factors that influence the crack propagation rate are microstructures of materials, components size and geometry, loading conditions, environments, and temperatures.
Why is similitude important for fatigue crack growth?
The concept of similitude is important for fatigue crack growth, as it provides the basis for applying fracture mechanics to fatigue crack growth. Similitude implies that the crack tip conditions are uniquely defined by a single loading parameter such as the stress intensity factor.
Is fatigue crack growth rate dependent on the applied stress ratio?
When the crack growth rates observed under different applied stress ratio R are compared, it is noted that fatigue crack growth rate exhibits a dependence on the R ratio, particularly at both extremes of the crack growth curve.
What is the dominant crack in fatigue loading?
When a structural component is subjected to fatigue loading, a dominant crack reaches a critical size under the peak load during the last cycle leading to a catastrophic failure. As an example, consider a plate with a crack of 2 a 0 subjected to a uniform stress σ perpendicular to the plane of the crack.