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Traian CICONE 1/31ME&M-I- Introduction

Machine Elements & Mechanisms

• An “applications” course

• Uses a wide range of your background courses:

• Statics & Dynamics

• Strength of Materials

• Materials and Processes

• Manufacturing Processes

• Fluid Mechanics

• Technical Drawing

• Introduction to Design

• Elasticity & Plasticity

• Heat Transfer • Mechanical Vibrations

Traian CICONE 2/31ME&M-I- Introduction

• Ability to apply knowledge of mathematics, science, and engineering in the field of mechanical engineering

• Ability to design a system, component, or process to meet desired needs in the field of mechanical engineering

• Ability to identify, formulate and solve mechanical engineering problems

• Understanding of professional and ethical responsibility in the field of mechanical engineering

• Ability to communicate effectively

• Ability to use the techniques, skills, and modern tools necessary for the practice of mechanical engineering

Course Outcomes

Traian CICONE 3/31ME&M-I- Introduction

Course DescriptionMachine Elements & Mechanisms – 5 Credits

3 hours Lecture1 hour Laboratory1 hour Tutorial

Machine Design – 2 hours Project – 2 Credits

PART 1

• Introduction in Mechanical Engineering DesignThreaded Fasteners & Power ScrewsHub-on-shaft Assemblies (Dismountable)Permanent Assemblies/Joints (Welds, Bonds)SpringsShaftsIntroduction in Tribology (Friction-Wear-Lubrication)

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Traian CICONE 4/31ME&M-I- Introduction

References

Course WEB Pagehttp://www.omtr.pub.ro/Colectivul_catedrei/PaginiPersonale/t_cicone/me&m/me&m.htm

Traian CICONE 5/31ME&M-I- Introduction

Engineering Design

Design - All activities preceding the transformation into realityby execution, with correlated material, and financial resources of an idea or a given subject.

Engineering - Applied science concerned with the understanding of scientific principles and applying them to achieve an imposed goal

Mechanical Engineering Design (Machine Design) -

A major component of Engineering that deals with the conception, design, development, refinement and application of machines and mechanical apparatus of all kinds.

The process of selecting mechanical components and putting them together to accomplish a desired function.

Traian CICONE 6/31ME&M-I- Introduction

Definitions: MACHINE

Machine An assemblage of parts that transmit forces, motion, or energy in a predetermined manner.

•Working machines - FORCES•Transport machines – MATERIALS•Power machines – ENERGY•Apparatus/Instruments – INFORMATION (Motion)

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Traian CICONE 7/31ME&M-I- Introduction

Working Machines (Technological Machines)

Excavator

Wheel loader

Perform useful work: machine-tools .

Corded drill

Traian CICONE 8/31ME&M-I- Introduction

Transport Machines

Turbo-pump(Ariane)

Transfer/Transport of materials: pumps, compressors, fans

Centrifugal-pump

Traian CICONE 9/31ME&M-I- Introduction

Power Machines (Engines)Transfer/Transport of energy: turbines, internal combustion engines, etc.

Turbine in Nuclear Power Plant (EDF )

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Traian CICONE 10/31ME&M-I- Introduction

Internal Combustion Engine

Power Machines (Engines)

Traian CICONE 11/31ME&M-I- Introduction

Apparatus/Instruments

Pressure indicatorManometer

Micrometer

Transfer/Transport of information: typewriter, pressure indicator, etc.

Traian CICONE 12/31ME&M-I- Introduction

Definitions: MECHANISM

Mechanism

Part of a machine that provides the transmission and transformation of a definite mechanical motion.

System of rigid bodies that provides the transformation of mechanical motion, and forces of a part into a definite motion and forces of another part.

Physical arrangement that provides for the definite motion of the parts of a machine.

•Linkages•Cams•Gears•Screws

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Traian CICONE 13/31ME&M-I- Introduction

Scissors screw jack

Linkage MechanismsSlider-crank mechanism

Screw mechanism

Traian CICONE 14/31ME&M-I- Introduction

Linkage Mechanisms

windshield wiper mechanism

Traian CICONE 15/31ME&M-I- Introduction

Gear Mechanisms

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Traian CICONE 16/31ME&M-I- Introduction

Cam Mechanisms

Camshaft with Plate Cam imparting on a Flat Follower, a Push Rod, a Rocker arm and the Valve.

Pumping mechanism

Traian CICONE 17/31ME&M-I- Introduction

Complex MechanismsLinkage + Gear + Cam.

Traian CICONE 18/31ME&M-I- Introduction

MACHINE

MECHANISM

Machine Element

Internal combustion engine

Slider-crankmechanism Crankcase Distribution

mechanism Etc.

Bolt Crankshaft Connecting rodPiston ….

The structure of a machine

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Traian CICONE 19/31ME&M-I- Introduction

Machine element/component/part

Classification

Part of a machine or mechanism with a definite functionality, which can be designed independently, and provides the transmission and transformation of a definite mechanical motion.

Complexity• Simple (screws, nuts, shafts, wheels, gears, etc.)

• Compound (bearings, disk friction clutches, V-belt transmissions, etc.)

• Complex (planetary gear boxes, etc)

Destination• General purpose

• Special purpose

Traian CICONE 20/31ME&M-I- Introduction

– sometimes is the creation of an original product– typically is the refinement or modification of an existing product

Engineering Activities

Design 25%Development 10%Research 10%Management 8%Sales 10%Technical Service 12%Construction 10%Manufacturing 15%

Engineering Design

“Design is the most creative part of the total engineering process.”

Traian CICONE 21/31ME&M-I- Introduction

Products’ life-cycle costs

Productdevelopment

Manufacturing Design

Construction (Manufacturing)

Materials Promotion, Distribution, Advertising

Real cost

Influence on the final value by

specific decisionsLife-cycle cost

70%

18%

10%

7%5%

Cost of a new product 100%

0%

50%

5%

40%

25%

20%

over 70% of a products’ life-cycle costs are committed at the design time, particularly the conceptual design phase

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Traian CICONE 22/31ME&M-I- Introduction

Mechanical (Machine) Design

The process of selecting mechanical components and putting them together to accomplish a

desired function.Integration requires• Imagination• Component familiarity

Traian CICONE 23/31ME&M-I- Introduction

Engineering Design

Identify a Need

Preliminary Design

Conceptual Design

Final Design

Manufacture

Sales & Delivery

Design of Machine Elements

Background research

Goal statement

Task specifications

Synthesis

Analysis

Selection

Detailed design

Prototyping & testing

Documentation

Traian CICONE 24/31ME&M-I- Introduction

• Starts with recognition of the need for the product.• Both design and redesign require knowledge of the

intended use of the product, plus information on the– Market– Technical data– Materials and production

• For any product design you are part of a team!!!Teamwork is paramount in the modern workplace.

The Design Process

Computer applications for analysis of a design are essential.

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Traian CICONE 25/31ME&M-I- Introduction

• Determine the need– Starts with recognition of a need– Sketching of the solution (product) is very useful during this step.

• Establish Known Information– Includes gathering information on aspects of the products such as possible

materials, market analysis, ability to manufacture, cost to manufacture, etc.• Stimulate Design Concepts

– Consider the various aspects in the manufacture of the product such as material, shape, etc.

• Investigate Design Concepts with Analytical Tools– Use modern methods and tools to analyze design alternatives.

• Gather all information and review– Gather together all information and design alternatives and review so that

decisions can be made.• Test the design that appears best.• Accept, Modify, or Reject• Optimize the design by iteration

Design Steps

Traian CICONE 26/31ME&M-I- Introduction

Define the problem

State the givens

Make appropriate assumptions

Preliminary design decisions

Design sketches

Mathematical models

Analysis of the design

Evaluation

Document results

Definition stage

Preliminary design stage

Detailed design stage

Documentation stage

A suggested procedure for the designer

Traian CICONE 27/31ME&M-I- Introduction

Traditional Design Process

Design is ITERATIVE

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Traian CICONE 28/31ME&M-I- Introduction

The design of a component or system may be influenced by a number of requirements. If a requirement affects design, it is called a design consideration. For example, if the ability to carry large loads without failure is important, we say that strength is a design consideration. Most product development projects involve a number of design considerations:

- Strength/stress - Cost - Thermal properties- Distortion/stiffness - Processing requirements - Surface finish- Wear - Weight - Lubrication- Corrosion - Life - Marketability- Safety - Noise - Maintenance- Reliability - Aesthetic considerations - Volume- Friction - Shape - Recyclability- Usability/utility - Environmental protection - Size

Design Considerations

Engineering Ethics - Ex. ASME Principles & Canons

Traian CICONE 29/31ME&M-I- Introduction

Standards and codes represent a prescriptive approach to design that may be incorporated into a design process.

StandardsA set of technical definitions and guidelines for designers and manufacturers.

Written by “experts”, they are considered voluntary.

ASME – AGMA – AISI - ANSIISO - BS, DIN, NF, ISO-SRISO or ASME groups develops and maintains standards using committees.

CodeA set of standards that has been adopted by one or more governmental bodies or incorporated into a contract. Essentially, it has the force of law behind it.

Standard & Codes

Traian CICONE 30/31ME&M-I- Introduction

Strength, safety, reliability, and cost are perhaps the most important design considerations. In general the design alternative that satisfies other design considerations at the lowest costs is to be preferred. Issues affecting the “cost” of a design include:

• Product development costs• Material choice• Manufacturing processes

involved• Economies of scale• Tolerances specified• Use of standard sizes and

components

Economics

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Traian CICONE 31/31ME&M-I- Introduction

Design Characteristics

Detail & Assembly DrawingsDesign Results

Design Methods CAD – Computer Aided Design CAE – Computer Aided Engineering

Team WorkingGood communication skills

(both oral and written)

Writing, sketching, using CAD tools, etc.Giving presentations