Ship Stresses

Question 1

Define Stress

Answer 1

The load or force per unit area

Question 2

Explain Strain

Answer 2

The distortion due to stress

Question 3

Explain Tensile

Answer 3

Tending to increase the objects length

Question 4

Explain Compression

Answer 4

Tending to decrease the objects length

Question 5

Explain Shearing

Answer 5

Two forces acting in the opposite direction

Question 6

Explain Static Force

Answer 6

Due to the difference in weight and support which occur throughout the ship

Question 7

Explain Dynamic Forces

Answer 7

Created by the hammering of the water on the ship, the passage of waves along the ship and by moving machinery parts

Question 8

Name The Types Of Longotiudinal Stresses

Answer 8

Sagging, hogging, alternate hatch loading

Question 9

Name The Types Of Transverse Stresses

Answer 9

Wing loading

Question 10

Which Stresses are Neither Longitudinal Or Transverse

Answer 10

Static water pressure, Drydock

Question 11

Brittleness

Answer 11

When a material fractures under stress

Question 12

Ductility

Answer 12

The ability of a material to be drawn or plastically deformed without fracture

Question 13

Elasticity

Answer 13

A material that is able to regain its original size and shape after a deforming forces has been removed

Question 14

Plasticity

Answer 14

The ability of a solid material to undergo permanent deformation, a non-reversable change of shape in response to an applied force

Question 15

Strength

Answer 15

AKA mechanics of materials, is focused on analysing stresses and deflections in materials under load

Question 16

Malleability

Answer 16

A physical property of metals that defines their ability to be hammered, pressed or rolled into thin sheets without breaking

Question 17

Steel

Answer 17

Can be considered an a;;oy of iron and carbon

Question 18

High Tensile Steel (HTS)

Answer 18

Use of higher strength steels allows reduction in thickness of deck, bottom shell and framing where it is fitted; the mid-ship section of larger vessels

Question 19

List the Properties of Steel

Answer 19

• Reasonable cost
• Easily welded
• Ductility
• Homogeneity
• Yield point to be a higher proportion of ultimate tensile strength
• Chemical composition suitable for flame cutting without hardening
• Reasonable resistance to corrosion

Question 20

Advantages of Aluminium and Alloy Aluminium

Answer 20

Lighter
Higher resistance to erosion
Not magnetic

Question 21

Disadvantages of Aluminium and Alloy Aluminium

Answer 21

Expensive
Weak
Difficult to work
Poor fire resistance
Reacts badly with steel

Question 22

Sandwich Plate System (SPS)

Answer 22

• A composite material comprised of two pieces of metal plates bonded with a polyurethane elastomer core, which transfers shear between each plate, and eliminating the need for stiffeners and precluding local faceplate buckling
• They are light, flat and stiff, with superior resistance to fatigue crack propagation, impact damage and local buckling
• They also provide built in fire insulation to international standards and very effective damping of ship borne noise and vibration

Question 23

Glass Reinforced Plastic (GRP)

Answer 23

A composite material consisting of high strength glass fibres bonded together by a resin of a lower strength and as a result it exhibits the best characteristics of both materials

Question 24

Properties of GRP

Answer 24

-Ease with which it can be moulded into complex shapes
-Strength
- Resistance to water
- Resistance to weathering
- High resistance to impact
- Doesn’t shatter

Question 25

Timber

Answer 25

Used as a shock absorber on modern ships to protect steel decks as well as make them less slippy

Question 26

Explain Safe Working Load (SWL)

Answer 26

Sometimes stated as the Normal Working Load (NWL), it is the maximum safe force a piece of lifting equipment can operate with, without fear of breaking. Usually marked on the equipment by the manufacturer

Question 27

Explain Still water Sagging

Answer 27

If a vessel is supported at each end, then the middle will tend to sag. Cargo loaded midships will cause the vessel to sag

Question 28

Explain Still Water Hogging

Answer 28

If the vessel is supported in the middle then the ends will sag (hogging). Cargo loaded in the for and aft of the hold caused the vessel to hog

Question 29

Explain Alternate Hatch Loading

Answer 29

Maximum values of sheer forces occur where there are abrupt changes of weight - e.g. bulkhead between an empty and full compartment

Question 30

Explain Wing Loading

Answer 30

When a ship is subject to a twisting moment

Question 31

Explain Static Water Pressure

Answer 31

Pressure increases with depth so, the greater the pressure on the ship's side and bottom plating. The tendency is for the sides to be pushed inwards, and the bottom to be pushed upwards

Question 32

Explain Dry Docking

Answer 32

A ship is designed to withstand pressure from the outside. When the ship is in the dry dock this pressure is removed. The only things holding the ship are keel blocks, the billage blocks and the side shores

Question 33

Explain Seaway Sagging

Answer 33

Due to the wave crest being at the for and aft of the vessel, the midship is un supported and tends to sag

Question 34

Explain Seaway Hogging

Answer 34

Due to the wave crest raising the midship, the for and aft of the ship is unsupported and tends to sag

Question 35

Explain Racking

Answer 35

Due to the rolling of the vessel, the waterline is not always horizontal. This means that the centre of buoyancy and centre of gravity are often not on the same line and push the transverse section into a diamond shape

Question 36

Explain Panting

Answer 36

This is the "in and out" movement of the ship's plating at the bow and stern areas due to the changing water pressures as the ship is sailing

Question 37

Explain Pounding

Answer 37

This is the slamming down of the ship's bottom plating near the bow during excessive pitching (falling heavily) in heavy weather

Question 38

Main Materials used for Ship Building

Answer 38

Steel Aluminium and Titanium alloy Copper alloys Glass Cements Foam Brass Wood

Question 39

Name the Three Types of Welding

Answer 39

Fusion Welding Gas Welding Electric Arc Welding

Question 40

What Type of Welding is This

Answer 40

Submerged arc welding

Question 41

What Type of Welding is This

Answer 41

Tungsten Inert Gas Welding (TIG)

Question 42

What Type of Welding is This

Answer 42

Metal Inert Gas Welding (MIG)