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Unit No.I :- Design of Simple Machine Elements

Unit No.I :- Design of Simple Machine Elements.

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Unit No.I :- Design of Simple Machine Elements

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  1. Unit No.I:- Design of Simple Machine Elements Machine Design, Design cycle, Design considerations - Strength, Rigidity, Manufacture, Assembly and Cost, Standards and codes, Use of preferred series, Factor of safety, Service factor. Design of Cotter joint, Knuckle joint, Levers - hand / foot lever, lever for safety valve, bell crank lever, and components subjected to eccentric loading.

  2. Machine Design: • Machine design is defined as the use of scientific principles, technical information and imagination in the description of a machine or a mechanical system to perform specific functions with maximum economy and efficiency.

  3. Basic Procedure of Machine Design:

  4. Basic Requirements/Consideration of Machine Elements: • Strength • Rigidity • Manufacturing Considerations • Assembly Considerations • Cost

  5. Standards and Codes • Standardization is defined as mandatory norms, to which various characteristics of a product should conform. The characteristics include materials, dimensions and shape of the component, method of testing and method of marking, packing and storing of the product.

  6. The following standards are used in mechanical engineering design: • Standards for Materials, their Chemical Compositions, Mechanical Properties and Heat Treatment: • Standards for Shapes and Dimensions of Commonly used Machine Elements: • Standards for Fits, Tolerances and Surface Finish of Component: • Standards for Testing of Products: • Standards for Engineering Drawing of Components

  7. A standard is defined as a set of specifications for parts, materials or processes. • There are three types of standards used in design office. They are as follows: • (i) Company standards They are used in a particular company or a group of sister concerns. • (ii) National standards These are the IS (Bureau of Indian Standards), DIN (German), AISI or SAE (USA) or BS (UK) standards. • (iii) International standards These are prepared by the International Standards Organization (ISO).

  8. Codes: It is defined as a set of specifications for the analysis, design, manufacture, testing and erection of the product. The purpose of a code is to achieve a specified level of safety. Factor of Safety It is defined, in general, as the ratio of the maximum stress to the working stress.

  9. Selection of Factor of Safety • The reliability of the properties of the material and change of these properties during service ; • 2. The reliability of test results and accuracy of application of these results to actual machine parts ; • 3. The reliability of applied load ; • 4. The certainty as to exact mode of failure ; • 5. The extent of simplifying assumptions ; • 6. The extent of localized stresses ; • 7. The extent of initial stresses set up during manufacture • 8. The extent of loss of life if failure occurs ; and • 9. The extent of loss of property if failure occurs.

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