strength of material 1 - forces on material

7/31/2019 Strength of Material 1 - Forces on Material

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Strength of Material 1FORCES ON MATERIALS

Created By:

Mohamad Fikree bin Alias

Lecturer

Politeknik Tuanku Sultanah Bahiyah


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What is Strength of Material

Usual symbols

Types of loads

Types of forces

Force effects Stress & types of stress

Normal strain

OUTLINE


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WHAT is Strength of Material?

Material ability to withstand an applied stress withoutfailure.

DEFINITION


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SYMBOL EXPLAINATION

A Area of effect

D Diameter

D Diameter Difference

E Young Modulus @ Elasticity Modulus

F@P Force

G Modulus of RigidityL Length

L Length Difference

U Strain Energy

(epsilon) Normal strain @ Direct strain

(phi) Shear strain

(rho) Density

(sigma) Normal stress @ Direct stress

(tau) Shear stress

(nu) Poisson rate

Usual Symbols


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Static

An external force

that is applied andheld in a fixedposition for a specificamount of time.

e.g. a parking car

Dynamic

A type of load thatchanges in thedirection or degree of

force during operation.e.g. walking tourist on

a bridge

Shock

A force delivered by ablow (sudden)

e.g. hammering

Fatigue &Alternating

Act on certain timeonly

e.g. water loadfountain (sluggish)

e.g. load on a spring(alternating)

TYPESOF

LOAD


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Elevator situation

Example


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Example


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Example

Load

Spring

Alternate

Fatigue


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TYPES OF FORCE


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Force applied to the material overtheArea ofcontact.

STRESS

= PAStress

Force Applied

Area of Contact

Unit:

Material


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TYPES OF STRESS


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#1

A 3000N of compressive load act on the bar as below.Calculate the value of stress.

Yawning already eh?

3000 N 3000 N

0.08 m

0.3 m

0.03 m

Ans: 1.25 MN


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#2

A 50kN of extensive load act on the bar as below. Calculatethe value of stress.

Yawning already eh?

50

kN

50

kN

0.07 m

200 mm

0.02 m

Ans: 35.714 MN


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#3

A 45kN of compressive load act on the bar as below. Calculatethe value of stress.

Yawning already eh?

45

kN

45

kN

50mm

200 mm

20 mm

Ans: 45 MN


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The increase or decrease of length occurred for a unitlength of bar.

Normal Strain

LLStrain

Lf - Li

Li

Unit:


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#1

Calculate the strain value of the bar.

Lets start working the brain

50 kN 50 kN

200 mm

0.02 m

210 mmAns: 0.05


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#2

Calculate the strain value of the bar.

Lets try it again

50 kN 50 kN

200 mm

0.02 m

2mm

Ans: - 0.02


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#3

A bar with 0.065m of length been given force resulting the barto increase its length by 0.04mm. Calculate the strain value ofthe bar.

Another exercise perhaps?

Ans: 6.15x10-4


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Force will result the material to:

1. Increase length

2. Decrease length

3. Elastic

4. Twisted

*use your clay to experiment with the effects. (optional)

FORCE EFFECTS


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Pick your lucky one!!

CHALLENGE PINS


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# (CLO1)

A steel rod with a diameter of 32mm been given a 3kN of forceon its axis as figure. Calculate the stress and strain value of therod. Given the initial length of the rod is 0.15m

QUIZ 1

3 kN 3 kN

2mm

= 3.73 N/m2

= 0.027

Ans:

strength of material 1 - forces on material

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