Table of Contents
What is yield point phenomenon?
Yield point phenomenon is understood to occur when stress drops down drastically because the locked in dislocations are set free. The dislocations are locked in due to presence of carbon in case of low carbon steels or mild steels.
Why is there a dip in the stress strain curve for mild steel?
This happens because the stress value is calculated using original cross-sectional area. After Ultimate point, necking takes place i.e. there is a big reduction in cross-sectional area, but for stress calculation, original cross section is taken into account. That’s why there is a dip in the curve, which is wrong.
Which type of steel does not show yield point phenomenon?
High strength steel and aluminum alloys do not exhibit a yield point, so this offset yield point is used on these materials. Upper and lower yield points. Some metals, such as mild steel, reach an upper yield point before dropping rapidly to a lower yield point.
Why there is a dip after upper yield point?
Upper yield point is the point after which the plastic deformation starts. This is due to the fact that the dislocations in the crystalline structure start moving. But after a while, the dislocations become too much in number and they restrict each others movement.
What is difference between cast iron and mild steel?
The most notable thing about its structure is that cast iron has graphite inclusions at the micro level. Mild steel is an Iron-carbon alloy containing less than 0.25 percent carbon which makes it more ductile and less hard thus rendering it unsuitable for structural work.
Why does mild steel material have an upper yield point and lower yield point?
The solutes (i.e., say carbon in mild steel) migrate to dislocations. Once the dislactions are free, i.e., are unlocked (by the solutes), the stress required to move dislocation is lower and you get the lower Yield stress, i.e., Yield Drop.
What is the difference between yield point and yield stress?
Yield strength or yield stress is the material property defined as the stress at which a material begins to deform plastically whereas yield point is the point where nonlinear (elastic + plastic) deformation begins.