MadSci Network: Engineering

Re: What is the difference between compression and tensil Streangth?

Date: Wed Apr 21 12:24:07 1999
Posted By: henryson omoregie, Faculty, engineering, boise state university
Area of science: Engineering
ID: 919616882.Eg

Question (a):	What is the difference between "Compression" and "Tensile 

Comment:	I have to limit my explanation to your level of 
understanding since you are a third grade student.

Answer (a):	When you throw a ball or land a punch on an opponent, you 
are applying or using force. Force is an interesting subject but we 
wouldn't get into this subject but the word 'force' will be used to explain 
some theories behind your questions. 
	COMPRESSION: When you push on both sides of a spring or sleep on a 
spring bed, you are applying a force that is due to compression.  On the 
other hand, if you pull on both sides of the spring you applying TENSION 

	TENSILE STRENGTH: If you pull on a spring up to the point that the 
spring breaks, then the force applied to the point of failure is called 
TENSILE STRENGTH. In order word, the force applied to the spring up to the 
point of failure (break point) is called TENSILE STRENGTH. 

Answer (b):	STRESS: Have you ever been under PRESSURE?. Engineers in 
the areas of Civil, Mechanical, Chemical, and Materials, often used the 
word "stress" instead of pressure. When you stand on your patio, your 
weight on a certain area of the patio contributes to the pressure your body 
is exerting on the area of the patio. Now, if you press hard on the round 
side of an egg and you press on the cone side of the egg using the same 
force, which side will break first?. Well, the STRESS (or PRESSURE) on cone 
side of the egg is going to be larger than the round (circular) side. DO 
YOU AGREE WITH THIS STATEMENT?. I HOPE SO. Let's discuss this a little bit 
further. Remember that STRESS is defined as FORCE DIVIDE BY AREA. Remember 
the area of the cone side of the egg is approximately half the area of the 
round side, therefore the STRESS required to break the cone side under 
compression is twice as large as the stress required of the round side. The 
round side, under compression and for the same force, will break first 
before the cone side. Likewise, if you have a boiled egg which usually have 
void (air space) on the round side of the egg, breaking the round side of 
this boiled egg is faster that the cone side.  Why? (1) Requires minimum 
stress on the round side compared to the cone side and (2) the contribution 
of the air space (void) inside the boiled egg. 

Answer (c):	EQUATION FOR STRESS: FORCE/AREA, that is, Force divide by 
area. Force is mass multiply by gravitational constant and Area is length 
multiply by width. The quantity scientists used to describe force is 
pound-force ( or KILOGRAM FORCE) and for area, square feet (square meter). 
Goodluck to you as a future Engineer and God Bless.

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