TTA104 Structures and Materials

Dr Paul Cunningham, SM1.22

Dr Andrew Watson, SM3.11

© Loughborough University 2010. This work is licensed under a Creative Commons Attribution 2.0 Licence.

Summary & ContentsThe module aims and objectives will be covered, together with the module outline and the methods of teaching and assessment. The module will then be introduced, and the important physical assumptions that will be applied throughout this module will be highlighted.

– Module Aims and Objectives– Teaching and Assessment– Module Delivery and Study Guide– The Importance of Attending Lectures– Reading List– Lecture Etiquette– Introduction to Module– State of Structural Materials– Isotropy– Homogeneity– Equilibrium Conditions– Rate of Loading– Summary of Assumptions– Credits & Notices

Module Aims and Objectives• Aim of the Module:

– Introduce the basic concepts, materials, theories, methodologies and some important issues encountered in the analysis and design of simple structural components subjected to tension, compression and shear.

• Intended Learning Outcomes:– Draw free body diagram and establish equilibrium equations for

structural systems under tension or compression– Apply tensile/compressive, shear and thermal loading to simple

structures and calculate deformation– Manipulate one-dimensional stress-strain relationships– Explain microstructures of engineering materials and relate them to

mechanical properties– Explain plastic deformation by using dislocations theory– Apply concepts such as load, force, support, moment, stress, strain and

energy to simple structures– Become familiar with prominent mechanical properties and concepts

used in structural design

Module Outline

• Section 1 – Statics (AW)• Section 2 – Tension, Compression and Shear (PC)• Section 3 – Stress / Strain Relationships (PC)• Section 4 – Behaviour of Materials

(PC)• Section 5 – Major Structural Materials

(PC)• Section 6 – Axially Loaded Structural Members (AW)• Section 7 – Stress Concentrations

(AW)• Section 8 – Statically Indeterminate Structures (AW)

Teaching and Assessment

• Teaching:– Two lectures per week

• Introduction and detailed presentation of concepts, methods etc.

• Worked examples

– One tutorial per week• Remember to sign the attendance register

• Assessment:– Closed-book examination (70%)– Mid-Semester test (15%)– Laboratory exercise (15%)

Module Delivery and Study Guide

• Worked examples will be presented during the lectures to illustrate the theories being presented– Some of these examples will be past exam questions

• Tutorial sheets will be provided – please attempt as many questions as you can prior to the tutorial sessions– The best way to learn is to practice, practice, practice!– Try to understand the theories, rather than learning “parrot fashion”– The tutorial sheets are there to help you in learning the material of the

module and prepare for the exam – do your best to attempt them– If in doubt, ask!

The Importance of Attending Lectures

Number of Lectures Missed

Lear

ning

Diff

icul

ty

2 4 6

You can catch-up, but it will take effort

You will need serious help

Not even a superhero can save you from this one!

Reading List

• Recommended Reading– Mechanics of Engineering Materials by P.P.

Benham, R.J. Crawford and C.G. Armstrong (Prentice Hall)

– Mechanics of Materials by J.M. Gere and S. Timoshenko (Nelson Thornes Ltd.)

• Further Reading– Engineering Materials (Vol. 1) by M.F. Ashby

and D.R.H. Jones (Butterworth-Heinemann )

Lecture Etiquette

• Please do not use mobile phones– Switch off or activate silent mode

• Please turn up on time– A prompt start will mean a prompt

finish

• Please refrain from chatting during the lecture– If you have a question – ask

Introduction to Module

• All aircraft / vehicles are constructed using materials such as metals, composites, polymers and ceramics– Major load-bearing structures in

aircraft / vehicles are made of metals and fibre-reinforced composites

• Designed to possess sufficient strength, stiffness and toughness

– Strength and stiffness of a structure:

• Size• Shape• Mechanical properties of material

State of Structural Materials

• Fundamental bounding principles about the state of materials and structures:– Isotropy (related to the state of a material)– Homogeneity (related to the state of a

material)– Equilibrium Condition (related to the state of a

structure)– Rate of Loading (related to the material and

service condition)

Isotropy

• When materials are made to possess micro-structural characteristics such that their physical and mechanical properties are the same in all directions, they are said to be isotropic

• If this condition is not met, they are considered anisotropic

• Most metals, polymers and ceramics are considered isotropic

• Fibre-reinforced composites are generally considered as anisotropic

• Unless expressly stated, the existence of an isotropic state is assumed

Homogeneity

• If physical and mechanical properties at any point of a bulky material are the same as that at any other point within the material, this material is said to be homogeneous

• When this condition is not met, the material is inhomogeneous

• Most metals, polymers and ceramics are homogeneous• Fibre-reinforced composites are generally

inhomogeneous on a microscopic scale– Considered homogeneous on a macroscopic scale (i.e.

millimeters)

• Unless expressly stated, the existence of an homogeneous state is assumed

Equilibrium Conditions

• Describes the state of balance between external loads and internal resisting forces– Tendency of one load to

move a structure in one direction is balanced or cancelled by the tendencies of other internal forces to move a structure in other directions

• If unbalanced, an external load will cause rigid body motion

Rate of Loading

• Static or quasi-static load: mechanical load applied at constant speed usually between 0.1 and 10 mm/min– Structure is in equilibrium– Dynamic or impact load: no equilibrium conditions

during the load• Repeated loading: typical loading dealing with

fatigue– Consists of many identical loading cycles– Each cycle is quasi-dynamic and overall mean

loading of a static nature• Unless expressly stated, the existence of a

quasi-static load is assumed

Summary of Assumptions

1. Structural materials are isotropic, homogenous deformable solids

2. Structural members in most cases are one-dimensional

3. Structural members are subjected to a quasi-static loading

4. The loaded structural members are in equilibrium

This resource was created by Loughborough University and released as an open educational resource through the Open Engineering Resources project of the HE Academy Engineering Subject Centre. The Open Engineering Resources project was funded by HEFCE and part of the JISC/HE Academy UKOER programme.

© 2010 Loughborough University

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Credits