Section 2 - Part 2 - Testing

Question 1

What is the tensile strength of a metal?

Answer 1

The ability to withstand the action of external forces without breaking.

Question 2

How is Tensile strength determined?

Answer 2

Also known as the ultimate strength, this is the maximum strength developed in a metal in a tension test.

Question 3

What is a tension test?

Answer 3

This is the most fundamental type of mechanical test. It provides information on elastic limit, elongation, Yield Point, yield strength, tensile strength and area reduction.

Question 4

What is the output of a tension test?

Answer 4

A Stress and Strain curve showing at what stages a material Elongates, Necks and Fractures.

Question 5

What observations can be made about most engineered materials in relation to the initial stress/strain performance?

Answer 5

It is typically in a straight, proportional line.

Question 6

What Law relates to engineered materials in relation to the initial stress/strain performance?

Answer 6

Hookes Law - E Stress (Theta) / Strain (E)

Question 7

What is the term for the Gradient of the Stree/Strain Curve conforming to Hookes Law?

Answer 7

Youngs Modules

Question 8

What is meant by Proportional Limit?

Answer 8

The limit up to which a material will maintain a perfectly uniform rate of strain to stress. This is usually equal to the elastic limit for many metals.

Question 9

What are the 3 phases of deformation in Tensile Strength of a metal?

Answer 9

Elastic Deformation, uniform Plastic Deformation, Non-Uniform Plastic Deformation.

Question 10

What are the 3 phases of deformation in Tensile Strength of a metal?

Answer 10

Elastic Deformation
Uniform Plastic Deformation
Non-Uniform Plastic Deformation.

Question 11

What is the Elastic Limit of a Material?

Answer 11

This is the greatest stress that can be applied to a material without causing permanent deformation.

Question 12

When is plastic deformation reached?

Answer 12

When the material is taken beyond its elastic limit. Its elastic limit is usually slightly beyond the proportional limit of the material.

Question 13

What is the yield point?

Answer 13

The yield point is the point where the material continues to deform without an increase in load. This deformation is of the permanent type and occurs when a material is taken beyond its elastic limit.

Question 14

What is the yield strength?

Answer 14

The maximum stress that can be developed in a material without causing plastic deformation.

Question 15

What is the ultimate strength or tensile strength?

Answer 15

The maximum stress developed by the material based on the original cross sectional area.

Question 16

What happens to ductile material when pulled beyond its ultimate strength?

Answer 16

Localised deformation, or necking, occurs. The load falls off as the area decreases. This non-uniform stretching happens rapidly at the points of failure/

Question 17

What is the difference in breaking strength between ductile and brittle materials?

Answer 17

Ductile materials have a breaking strength which is always less than ultimate strength. Brittle materials have ultimate and breaking strengths which coincide.

Question 18

How is ductility tested?

Answer 18

Ductility is indicated by the amount of deformation that is possible until fracture occurs.

Question 19

What comparisons are made to determine ductility following a test?

Answer 19

Lf = final gauge length
Lo = Original gauge length.
Ao = Original cross sectional area
Af = final cross sectional area.

Question 20

What is a proof test?

Answer 20

A proof test is the maximum stress a material can withstand without taking more than a small amount of set.

Question 21

What is the Charpy impact test?

Answer 21

A breaking test, where a test piece receives a single swinging blow on a pendulum, under conditions controlled by a standard.

Question 22

What are the measured variables in a Charpy impact test?

Answer 22

The absorbed energy in Joules. This absorbed energy is a measure of the impact strength of a material.

Question 23

What can a typical hydrostatic pressure test pressure be expected to reach?

Answer 23

80% of its rated burst pressure

Question 24

What is an impact test?

Answer 24

An impact test is a test for determining the energy absorbed in fracturing a test piece in high velocity.