دانلود کتاب ابعاد مهندسی، واحدها و تبدیل ها

This book delves into the description, analysis, and application of the engineering dimensions, units, and unit conversions. Dimensions represent measurement types of physical quantities, while units denote the magnitudes assigned to the correlated measurements of these quantities. Both dimensions and units play a pivotal role in engineering practice. Failing to correctly apply them leads to confusion in calculations and drawings for engineering design and research and design (R&D). Dimensions and units are categorized into the fundamental, also known as the primary, dimensions and units and the derived, also known as the secondary, dimensions and units. The fundamental dimensions and units are basics, while the derived dimensions and units are derived from the fundamental and can be expressed in terms of the fundamental ones. Proper unit expression in calculations and drawings follows conventional formats and rules, such as dimensioning methods, significant figures, and rounding off numbers. In engineering practice, the consistency of dimensions and units of quantities is crucial in physical expressions and equation calculations. Inconsistent dimensions and units should not be manipulated in equations, such as addition, subtraction, multiplication, and division. In the United States, two unit systems are used in engineering practice. One is the English system also called the United States Customary System (USCS), and another is the International System (SI) also called the metric system. Unit conversions in the system and between the systems are essential to maintain unit consistency. Dimensional analysis is useful to help check the unit consistency in physical expressions and equation calculations and determine the relationship of dimensions between physical quantities. The dimensionless numbers resulting from dimensional analysis are extremely valuable to reveal the characteristics and behaviors of the complex phenomena in R&D. This book is composed of eight chapters to cover the previously mentioned delineations: Chapter 1 lays the groundwork by emphasizing the necessary application of dimensions and units in engineering and elucidating their indispensable role in engineering practice. It is so important for students majoring in engineering, engineers engaging in engineering practice, and those preparing for the FE/PE exams to thoroughly understand and correctly apply the dimensions units, and unit conversions. Chapter 2 delves into the intricacies of dimensions in engineering, comprehensively describes the fundamental and derived dimensions, and illustrates the principle of dimensional homogeneity as a key factor in maintaining dimensional consistency. The principle of dimensional homogeneity is a basic axiom in dimensional analysis. Chapter 3 ventures into the expansive landscape of units in engineering, offers a complete exploration of both fundamental and derived units, and portrays in detail various unit systems in both the English system and the SI. In the chapter, the guidelines of applying units in the SI, including common rules, decimal separators, and unit prefixes, are presented. Chapter 4 is dedicated to the intricate process of the unit conversions, providing insights into the unit conversion factor and the unity conversion ratio and fully illustrating the unit conversions in the English system, the SI, and between the two systems. In the chapter, the unit conversion using computer software is also introduced. Chapter 5 unveils the world of dimensional analysis, describes the methods of nondimensionalized equations and Pi theorem to obtain dimensionless numbers, and detailly presents the procedures to generate the dimensionless numbers, which help with understanding complex physical phenomena. In the chapter, commonly used dimensionless numbers are presented. Chapter 6 takes a closer look at the role of units and unit conversions in equation calculations and underscores the importance of unit consistency. The chapter also delves into conventional rules for how to formulate numerical values in equation calculations, such as significant figures and rounding off numbers. Chapter 7 provides an extensive discussion of basics of dimensioning objects in engineering drawings. Numerous illustrations of dimensioning objects on drawings are presented. Chapter 8 offers basic and practical knowledge of pipes, ducts, and dimensioning pipes and ducts of pipe and duct systems. Typical drawings of dimensioning the pipe and duct systems are presented. The book, enriched with numerous examples, exercises including some in the style found on the FE exam style, and drawings, serves as a comprehensive resource for students majoring in engineering, engineers engaging in engineering practice, and those preparing for the FE/PE exams to thoroughly understand and correctly apply the dimensions, units, and unit conversions. The book can also be used as a textbook in engineering colleges and a reference for engineers and researchers in engineering design and R&D.