Mechanical Testing (7)

Question 1

Elastic Stress

Answer 1

The presence of strain. Can cause the material to deform but react elastically or return to the original shape when the strain is removed.

Question 2

Ultimate Tensile Strength

Answer 2

Maximum unit stress that a material can resist before failure.

Question 3

Tension stress

Answer 3

Pushing

Question 4

Compression Stress

Answer 4

Pulling

Question 5

Bending Stress

Answer 5

Similar to stretching in Yoga.

Question 6

Sheer Stress

Answer 6

Scissor action stress. Cutting pressure applied in two separate directions.

Question 7

Torsion Stress

Answer 7

Twisting, ex. wringing a towel.

Question 8

Fatigue

Answer 8

Progressive stress caused by cyclic loading. Repetitive stress below the rated capacity.

Question 9

Elastic Deformation

Answer 9

As a load is applied the bonds between atoms stretch and will deform in the direction the force is applied. The load is removed and cannot return to it original position.

Question 10

Elastic Limit/Yield Point

Answer 10

Maximum point of deformation before failure.

Question 11

Plastic Deformation

Answer 11

When the load exceeds the Elastic Limit/Yield Point and the part becomes permanently deformed and snaps/fails/breaks.

Question 12

Stress

Answer 12

Area

Question 13

Factor of Safety

Answer 13

Reaction between the actual stress and ultimate strength.

i.e. If Strength = 50,000lbs and Lift = 10,000lbs, then the Safety factor = 5

Question 14

Yield Point Calculation

Tensile Test

Answer 14

Cross-sectional area

Question 15

Strain Calculation

Tensile Test

Answer 15

Original Length

Question 16

Tensile Test

Answer 16

To put a specimen of known size and tension, measure and record the load as it is increased and the specimen deforms over a specific length (Gauge).

Question 17

Hardness Test

Answer 17

To determine a material resistance ti Plastic Deformation.
- Dependant on Ductility, Elasticity, Plasticity, Strain and Strength.

Tests:

1. Resistance to Penetration
2. Elastic Hardness
3. Resistance to Cutting and Abrasion

Question 18

Vickers Test

Answer 18

Measures the hardness of heat-affected zones (HAZ) of welds. Measures using a square-shaped pyramid diamond indenter.
(Micro-Hardness Test)

Question 19

Turkon-Knoop Test

Answer 19

Automatic and diamond shaped equipment Can be combined with a Vickers unit with results viewed under a microscope.
(Micro-Hardness Test)

Question 20

Barcol Tester

Answer 20

Used for Composite materials, to determine how much it has cured.
(Micro-Hardness Test)

Question 21

Scleroscope

Answer 21

Measures the rebound of a falling hammer with a diamond tip.

Question 22

Leap-rebound Principle

Answer 22

Compares impact and rebound signals from a magnet in an encircling coil.
- Krautkramer Dynamic or Equotip

Question 23

Mohs

Answer 23

Simple scratch test from 1812, measured on a scale of 1-10 to test resistance to abrasion hardness.

Question 24

Charpy and Izod

Answer 24

Notch bar impact test used to determine the decrease in fracture resistance caused by a sudden impact loading of a notch cut into the specimen.

• Specified load is positioned on a pendulum and swung down to strike the notch.
• About of energy absorbed is measured by how far back the Pendulum swings.
• Joules and Foot-Pounds

Question 25

Endurance Limit/Fatigue Limit

Answer 25

Maximum alternating stress below that of which the material can theoretically endure before failure.

Question 26

Fatigue Strength

Answer 26

Maximum stress that can be sustained for a specific number of cycles without failure.