Mechanical Engineering (1)

A Course

For

1st Year Bio-Medical Engineering

By

Dr. Sief A.Y. Khorshid

Mechanical Design and Production Dept.

Cairo University – Faculty of Engineering

January 2001

Contents

Preface

Nomenclature

References

Preface

This course is intended to help bio-medical engineering students to have a better understanding and complete grasp of the methods and tools used in the analysis and design of structural systems.

A mechanized structural system is an assembly of bars, beams and frames that contains rotating shafts, gears, moving arms and pistons to do certain functions successfully. This concept is also applied on the a human body, where the skeleton is viewed as the main structure that assemble all body systems in a way that guarantees proper life functions.

For both structures, analysis can be applied through mechanical engineering methods. These methods are based on two principles; equilibrium and continuity.

The analysis methods are basically relaying on two principles namely the equilibrium principle and continuity principle. Equilibrium principle dictates that a system in equilibrium is composed of elements in equilibrium. Continuity principle requires that the deformations of a system should be in a complete compatibility of the deformations resulting from its elements.

Analysis usually starts by defining external applied loads and ends by determination of stresses resulting in each structural element. The values of these stresses decide the proper functioning of each element i.e. its continuous successful functioning throughout the system service life. Geometrical, and material properties of each element are selected in order to ensure its well being under the action of the expected body and boundary loads.

Determination of applied loads and reactions are obtained through mechanics of rigid bodies. Deformation of bars, beams, shafts and pressure cylinders are related to the elastic properties of mater and the geometrical properties of these elements.

In order to serve the objectives of the course, the course layout is divided into two main parts. The first part is dealing with analysis of loaded structural elements where one element or a system of elements are investigated for internal loads, deformations, stresses and strains. In the second part, machine elements, which are used to compile a machine, are subjected to analysis in order to obtain the acting stresses and resulting deformations and strains.

A set of problems are selected to be solved by the students during the exercise times in order to complete the full command of the presented methods of analysis. These problems are designed in away to cover the different aspects of the presented methods of analysis and the practical applications to some medical equipments.

The full understanding of the course items needs the support of the following pre-studied subjects:

Mechanics of rigid bodies

Elasticity.

Solution of linear equations.

Nomenclature

Force Vector in Direction i.

Moment Vector in Direction i.

: Body mass (Scalar).

Body Moment of inertia (Scalar).

Linear Acceleration Vector in Direction i.

Rotational Acceleration Vector in Direction i.

Body displacement Vector in Direction i.

Rotation angle Vector around Direction i.

Time in seconds.

Work in Joules.

Power in watts.

Linear speed in direction i.

Rotational speed around direction i.

Frictional coefficient of friction.

Distance .

Weight .

Gravitational Acceleration = 9.81 m/sec2.

References

  1. S.E.A. Bayoumi; “ Mechanics of Deformable Solids”, Part 1,1971, Lecture Notes.
  2. S.H. Crandall, N.C. Dahl,”An Intriduction to The Mechanics of Solids”,1978, Mc-Graw-Hill Kogakusha ltd.
  3. J.L.Meriam, L.G. Kraige,” Engineering Mechanics”, Vol. I,1987, John Wiley.
  4. G.D.Jones,” Mechanical Engineering Science”,1989, ELBS.
  5. N.H.Cook,” Mechanics and Materials for Design”, 1985, MacGraw-Hill International.
  6. J.E.Shigley, C.R. Mishke,”Mechanical Engineeing Design”,1989, MacGraw-Hill International.

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