2. Testing of Materials

What methods are used to test for compression / tensile

1. Using a hardness tester to test hardness and comparing it against charts for hards vs tensile 2. A special device that pulls and object apart and measures it tensile strength

How is fatigue strength tested?

A machine that continuously loads and unloads and object until it breaks

What type of tester would you use aluminum?

Barcol

How is tensile strength tested in a nonferrous metal?

By pulling the material apart until it breaks.

What is used to test impact resistance properties of a non ferrous metal? and whats it measure in?

Charpy impact test. Energy (joules)

Describe how a Brinell hardness number is derived and give typical notations for hard and soft materials.

Derived using an equation that compares: P = applied load in kilogram-force (kgf) D = diameter of indenter (mm) d = diameter of indentation (mm

What is the formula for youngs modulus?

E=f/e

What does E represent and what is its units?

E=modulus of elasticity, psi or in-lb/in3

Which is harder? HRC 55-62 or HRC 40-4

HRC 55-62

Which test is more quick and easy to do?

Hardness

_________________ refers to the ability of a material to resist abrasion, penetration, cutting action or permanent distortion.

Hardness

What is the difficulties with precision alignment?

It is difficult and expensive.

Explain tensile and compression testing of metals with particular regard to determining by calculation: a. ultimate tensile stress

It is the maximum stress that a material can withstand while being stretched or pulled before NECKING

What does large values of E mean?

Large values of E show that the material is stiff and will have little strain for a given value of stress

State the shape of the point used to contact the test specimen in each tester.

Rockewell: Either Diamond or Ball Brinell: Ball

HRC 55-62 is an example of what?

Rockwell hardness value

Why is this?

Strength testing requires: - You pull from both ends of an object until it breaks which makes the object useless - Requires precise alignment. - Some things can be extremely strong requiring a lot of force

how does a charpy impact test work?

Swings a weight on a pendulum and smacks into the test pice which measures resistance.

Explain tensile and compression testing of metals with particular regard to determining by calculation: b. yield point

The first point at which permanent deformation of a stressed materal begins to take place.

Explain tensile and compression testing of metals with particular regard to determining by calculation: c. percentage elongation

The percent elongation reported in a tensile test is defined as the MAXIMUM ELONGATION of the material length DIVIDED by the ORIGINAL MATERIAL LENGTH

Hardness testing is carried out using......

Vickers or Rockwell tester. and brinell

The point on the stress-strain curve at which the increase in strain is no longer proportional to the increase in stressage elongation is called?

Yield Point

Explain tensile and compression testing of metals with particular regard to determining by calculation: d. Young's modulus of elasticity

Youngs modulus measures the stiffness of the material.

The indentation diameter should be......

clearly outlined.

The _______________ strength of a material is the maximum ___________________ stress that it can withstand without being crushed or fail due to internal shear failure

compressive. compressive

Do not make indentations on a ___________ surface having a radius of less than...

curved. 1 inch

Fatigue is the progressive and localized structural damage that occurs when a material is subjected to _________ loading.

cyclic

Both strength and hardness are measures of a materials resistance to ________________.

deformation

The Rockwell test determines the hardness by measuring the _______ of penetration of an indenter under a ______ load compared to the penetration made by a ____________.

depth. large. preload

If a test specimen of a material is subjected to a tension or compression load and the stress and strain are measured and are proportional to each other, the material is said to be ____________.

elastic

As the strength of a particular material increases, its ______________ also increases.

hardness

The most common method of checking the effect of a heat treatment is by measuring ____________ because the relationship between strength and hardness for a particular metal is well known.

hardness

Note that the harder the material is, the __________ the Barcol number will be.

higher

The Rockwell scale is a hardness scale based on the ____________ _______________ of a material.

indentation hardness

Fatigue occurs when a material is subjected to repeated ____________ and _____________.

loading. unloading

Measuring the Rockwell hardness of a material involves the application of a __________ load followed by a _________ load, and then noting the depth of penetration.

minor. major

Can you use a piece after you have brinell tested it?

no

The thickness of the work piece being tested should be such that no bulge or mark showing the effect of the load appears on the side of the work piece _____________ the indentation.

opposite

When performing hardness testing, you are measuring how far a fixed object will _______________ into the material under a fixed load.

penetrate

Apply the load so the direction of loading and the test surface are _____________ to each other within 2 degrees.

perpendicular

What is tensile strength?

resistance to a force which tends to pull it apart.

The Brinell scale characterizes the indentation hardness of materials through the _________ of penetration of an indenter, loaded on a material test-piece.

scale.

What are the three measurements of hardness?

scratch hardness, indentation hardness, and rebound hardness.

Do make the indentations with the correct ________ Indentations should not be made too close to the ________ of the work piece being tested.

spacing. edge.

Apply the load ___________ to avoid overloading caused by inertia of the weights.

steadily

What does e represent and what is its units?

strain in/in

What does f represent and what is its units?

stress, psi

When performing strength testing you are measuring the distance a material ______________ under a known load.

stretches.

Are strength and hardness interrelated?

yes