What are beach marks?

Beach marks are concentric rings in a fatigue region which resemble tide marks on a beach. Crack advancements are caused by changes in environment and load. Whenever there is an interruption in the propagation of a fatigue fracture, a unique feature of macroscopically visible marks or ridges may be found.

What do beach marks show?

What is the difference between fatigue striations and beach marks?

What are ratchet marks?

How can you tell fatigue crack?

What causes shaft failure?

The majority of shaft failures are fatigue related, due to excessive rotary bending. Almost all shaft failures occur at the point of a stress raiser, typically at the bearing shoulder or the keyway.

What are the factors affecting fatigue failure?

Fatigue life is affected by cyclic stresses, residual stresses, material properties, internal defects, grain size, temperature, design geometry, surface quality, oxidation, corrosion, etc.

What is a ratchet mark?

Ratchet marks are macroscopically visible lines running parallel to the overall direction of crack propagation. They are formed by the intersection of fatigue cracks propagating from multiple ori- gins.

What measures may be taken to increase the resistance to fatigue of a metal alloy?

What is shear lip?

[′shir ‚lip] (metallurgy) An area or ridge at the edge of a shear fracture surface.

What is fatigue lifetime?

Thus fatigue lifetime is a statistical event: the probability of having a critical inclusion depends upon the inclusion size distribution overlaid on a map of the principle stresses.

What is creep cracking?

Creep damage occurs in metals and alloys after prolonged exposure to stress at elevated temperatures. It is usually associated with the tertiary stage of creep, and brings about the onset of creep failure. It can, however, initiate at the relatively early stages of creep, and develop gradually throughout creep life.

Why do pump shafts break?

The main reason that shafts break can often be traced to operational and system reasons. Fatigue failure (also known as failure due to reversed bending fatigue with rotation) is the most common cause of pump shaft fractures/failures.

What is pump shaft?

The pump shaft is the central component of a centrifugal pump rotor and carries the impellers, the shaft sleeves (e. g. spacer sleeves between the impellers or shaft protecting sleeves in the shaft seal area), the bearings (rolling element bearings or plain bearing sleeves and thrust collars), in some cases balance …

How does surface finish affect endurance limit?

The effect of surface roughness can reduce the fatigue strength of components and can even cause disastrous consequences when the applied load level is below the fatigue limit of the material.

Which method is widely used in stress life module?

The stress–life method, based on Wohler’s S–N diagram, was the first quantitative approach. The stress–life approach is used in applications where the applied stress is essentially within the elastic range, and the material has a long cyclic life.

How can the fatigue life of a material be improved?

Fatigue life is improved by reducing the stress concentration on the weld joint, softening the weld toe shape, improving the metal structure of the weld zone, and adequately changing the pin shape and treatment conditions of friction stir welding as shown in Figure 2.

How does the fatigue life of a part can be improved?

Explanation: Shot peening: Shot peening is a cold work process used to finish metal parts to prevent fatigue and stress corrosion failures and prolong product life for the part.

What causes shear lips?

At this moment a corrosion mechanism is held responsible for the shear lip phenomenon and the associated crack growth rate behaviour. It is thought that the corrosion mechanism gradually loses its influence by increasing da/dN from T3 to T4. This causes the slope change and shear lip growth.

What is creep failure?

Creep failure is the time-dependent and permanent deformation of a material when subjected to a constant load or stress. This deformation typically occurs at elevated temperatures, although it may occur under ambient temperatures as well.

What is mental fatigue?

During or after your medical treatment, you may sometimes feel mentally tired. This is called mental fatigue. Mental fatigue can come and go. Mental fatigue will make it hard to pay attention or focus on a task for long periods of time. You may feel mental fatigue after doing work that takes a lot of mental energy.