Define fatigue - materials, Civil Engineering

Assignment Help:

Define Fatigue - Materials

The normative view of the stress/strain is found in the example of the paper clip wire experiment. Take a paper clip wire and try to break it by pulling on it by hand. You are unable to break it because you need to exceed the ultimate stress of the material. Bend a paper clip between your fingers and the following is observed: when the wire rebounds to its original shape the proportional/elastic limit is observed; bend it farther to a point where the wire is permanently deformed, the yield point is observed; and, when the wire is bent one way then the other a few times, the wire breaks easily. The phenomenon is known as fatigue.

1968_Define fatigue - materials.png

All materials have microcracks. The cracks are not critical and are averaged as ultimate strength for the bulk material in a tension test. However, when the material is subjected to cyclic loading, the microcracks can grow until some of the cracks reach critical length, at which time the material breaks. The stress value at cyclic loading is significantly lower than ultimate stress of the material. Failure due to cyclic loading at stress levels significantly lower than the static ultimate stress is called fatigue. All engineered systems account for fatigue failure. At low levels of stress the failure may occur at millions or billions of cycles. Endurance tests determine the cyclic loadings and fatigue strength.

 


Related Discussions:- Define fatigue - materials

Force system, show the diagram for non coplanar non concurrent force system...

show the diagram for non coplanar non concurrent force system

What is codal provisions, According to National Building Code (Sp:7 1970), ...

According to National Building Code (Sp:7 1970), the differential settlement shall be kept within the limits to which the superstructure can accommodate itself without harmful dist

Orientation of wing walls in designing of bridge abutments, Question Wha...

Question What is consideration in selecting an orientation of wing walls in designing of bridge abutments ? Answer There are three familiar arrangements of wing walls in

Structural connection loosening - deterioration in steel, Define Structural...

Define Structural connection loosening - Deterioration in Steel? Structural connections joined together by rivets or bolts have a tendency to work loose over an extended period

Characteristic strength of concrete, In addition to its own weight, the bea...

In addition to its own weight, the beam in Figure is to carry a uniformly distributed live load of 12 kN/m. Figure 1 also shows the cross-sectional details of the beam. Design a

Hydrographic data for design of bridge, Q.What Hydrographic data required f...

Q.What Hydrographic data required for Design of bridge? (i) Design discharge for bridge waterway and foundation with corresponding high flood levels. Frequency curve for annual

What are service reservoirs, Q. What are Service reservoirs? Service re...

Q. What are Service reservoirs? Service reservoirs, other than normal reservoirs are provided due to the subsequent reasons:  (i)  In case of breakdown of pumping stations a

Explain the term - prestressing force, Explain the term - Prestressing Forc...

Explain the term - Prestressing Force Due to the stretching of  tendons, tensile stresses develop inside tendons. Resultant prestressing force in tendons may be calculated by m

Categories of losses of prestress, Categories of losses of prestress We...

Categories of losses of prestress We may put various losses in either of two categories : Losses which take place during transfer of  prestress and those which take place after

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd