# Mechanics and Strengths

MECHANICS/STRENGTHS

SMS Code EE401001

Level 4 Credits 14

Total Hours 140 Contact Hours 92

Work Experience Hours Nil Self Directed Hours 48

NQF Units/Other Components contained are:

Aims The general aim of this paper is to relate topics of Mechanical Engineering to the field of physics and to provide students with the basic fundamental principles of mechanics of machines. This course will also introduce the students to the basic fundamental principles of strengths of materials.

Learning Outcomes At the successful completion of this course, students will be able to: • derive the basic SI units of mass, force, density, relative density and moments • analyse and solve basic static force systems • understand the concept of and calculate the centre of gravity • demonstrate an understanding of the concept of friction and its effects on mechanical systems • demonstrate an understanding of the concept and practical applications of the laws of the machine • use their basic knowledge of dynamics, momentum, impulse, work, power and energy to solve problems in linear and rotary systems • define and specify the basic units of stress, strain and shear. • calculate second moment of area for various shapes. • specify and calculate the basic properties of engineering materials. • calculate basic stresses and strains. • calculate basic beam loads, reactions, shear forces and bending moments. draw basic shear force and bending moment diagrams. • prove the beam bending stress formula and calculate bending stresses, section modulus and plot the bending stress distribution across the beam. • prove the torsional shafting stress formula and calculate torsional stress, torsional rigidity and plot the torsional stress distribution across the shaft.

Content Mechanics  basic mechanics (SI units - fundamental, supplementary and derived units, mass, force, density, relative density, moments  static’s (vector analysis, parallel forces, equilibrium)  static force systems (free body diagrams, Bows notation, polygon of forces)  Moments of forces  pin jointed frameworks (graphical solutions method of joints, method of sections)  centre of gravity, centre of area Friction  coefficient of friction  friction on inclined plane  friction in screws and wedges Machines  load effort  mechanical advantage, velocity ratio  machines like levers, blocks, screws, gears, differential pulleys Dynamics (basic)  linear motion - displacement, velocity, acceleration  vertical motion under gravity  rotary motion - displacement, velocity, acceleration  relation between linear and angular motion

Momentum and Impulse  Newton’s laws  relation between force, mass and acceleration Work, Power and Energy  linear and rotational  energy forms and conservation  power, work done and diagrams Dynamics (intermediate)  moment of inertia, radius of gyration  centrifugal and centripetal forces and acceleration  torque, power, angular momentum  vehicle dynamics, hoists, flywheels Principles of Strengths of Materials  definitions/units of stress, strain, shear  basic stress strain calculations 2nd Moment of Area  parallel axis theorem  neutral axis  polar moment of area Mechanical Properties of Materials  tension compression test, yield/ultimate stress  stress- strain diagram  stress-strain behaviour of ductile and brittle materials  Hooks law, Poison's ratio, Young's modulus Simple Stress and Strain  tensile, compressive, shear stress and strain  factor of safety  stresses in thin cylinders  stresses in composite bars  strain and shear strain energy Beams (basic)  reactions, equilibrium  shear force and bending moment diagrams (point and udl loads) simply supported, cantilever Bending Stresses  proof of bending equation  bending stress distribution  section modulus, selection of sections from tables Torsional stress  proof of shafting formula  torsion in solid and hollow shafts  torsional stress distribution on a circular shaft  torsional rigidity  combined bending and torsion in shafts  Learning/Teaching Methods Lecturers will use a range of teaching and learning methods with a strong focus on activities. See section 5.8.2 for further details.

Assessment Assessment is the general term used for activities, which provide feedback on Student performance and is the measure by which a student’s performance is determined. The types of assessment used in papers are: • Practical assignments and exercises • Practical and laboratory work evaluations as individual or group project • Tests • Examinations

Final examinations may include any material studied throughout the course. 2 Examinations 50% Tests 10% Assignments 10% Laboratories 30%

Attendance Requirements 90%

Completion requirements To complete this course, students must meet the attendance requirement and pass all summative assessments.

Literature References for Curriculum Development Bolton, W. (1994). Engineering Science (2nd Ed). Oxford Boston: Newnes.