Stress-strain carves for ductile materials, Mechanical Engineering

Stress-strain carves for ductile materials:

A material is said to be ductile in nature, if it elongates before fracture. One this type of material is mild steel. Shape of stress strain diagram for mild steel is shown in the figure given below.

A mild steel specimen of circular cross section or rectangular section is pulled until it breaks. The extensions of bar can be measured at every load increments. The stresses can be calculated based on the original cross sectional area and strains by dividing extensions by gauge length. When specimen of a mild steel is loaded in tension gradually, increasing tensile load, in the tension testing machine. The initial portion from O to A is linear where the strain linearly varies with stress. The line is called as line of proportionality and is known as proportionality limit. The stress corresponding to point is known as Limit of Proportionality. Hook's law obeys in this, slope of line gives, modulus of elasticity.

Further any increase in load increases extension rapidly and the stress strain diagram becomes curved. At the point B, material reaches elastic limit of it indicating end of elastic zone and entry into plastic zone. In most cases A and B coincide. If load is removed material returns to original dimensions of it.

Beyond elastic limit, the material enters into plastic zone and removal of load does not return specimen to its original dimensions, therefore subjecting the specimen to permanent deformation. On loading further the curve reaches the point 'C' called as upper yield point at which sudden extension occurs which is called as ductile extension where strain increases at constant stress. This can be identified by horizontal portion of the diagram. Point C gives yield stress beyond which load decreases with increase in strain up to C called as lower yield point.

After lower yield point has been crossed, stress again begins increasing, till stress reaches the maximum value at the point 'D'. The increase in load causes non linear extension up to point D. The point D called as ultimate point or maximum point. This point gives ultimate strength or maximum load of bar. The stress corresponding to highest point 'D' of stress strain diagram is called as ultimate stress.

 

2365_Stress-strain carves for ductile materials.png

Posted Date: 10/20/2012 8:09:46 AM | Location : United States







Related Discussions:- Stress-strain carves for ductile materials, Assignment Help, Ask Question on Stress-strain carves for ductile materials, Get Answer, Expert's Help, Stress-strain carves for ductile materials Discussions

Write discussion on Stress-strain carves for ductile materials
Your posts are moderated
Related Questions
what is the effect of tolerance in process planning?

An experiment to determine the convection coefficient associated with airflow over the surface of a thick stainless steel casting involves insertion of thermocouples in the casting

Distribution of shearing stresses on l--sections and miscellaneous sections

Ask question #Minimum 100 words awrite short note on the the hierarchical system structure involving various level


What are square footings? SQUARE FOOTINGS This type of footing, also termed an isolated spread footing is probably the most common, simplest and most economical of the vario

Prepare a design of close coiled helical compression spring for a service load ranging from 2250 N to 2750 N. The axial deflection of the spring for the load range is 6 mm. Conside

A combined cycle plant is designed to develop 200MW power. The air is obtained by the compressor at 300K and 1 bar pressure. The maximum temperature of the gas turbine cycle is lim

A uniform air stream with velocity U = 10m/s flows over a flat plate of length 10 meters in the first meter the boundary layer is laminar but beyond this point boundary layer is fu

(a) Show that two statements of Second Law of thermodynamics are similar to each other. (b) A house that was heated by electric resistance heater consumed 1200 KWh of electric e