Technology & Engineering
Internal Forces
Internal forces refer to the forces that act within a structure or object. These forces include tension, compression, and shear, and they are essential for understanding how materials and structures behave under different conditions. By analyzing internal forces, engineers can design and construct buildings, bridges, and other structures to ensure they can withstand the forces they will encounter.
Written by Perlego with AI-assistance
Related key terms
1 of 5
5 Key excerpts on "Internal Forces"
eBook - PDFEngineering Mechanics: Statics
Modeling and Analyzing Systems in Equilibrium
- Sheri D. Sheppard, Thalia Anagnos, Sarah L. Billington(Authors)
- 2017(Publication Date)
- Wiley(Publisher)
External forces may be any of the types we have discussed previously—gravitational, normal contact, friction, fluid contact, tension, compressive, or shear. Internal Forces are those that exist INSIDE the system in equal and opposite pairs (Newton’s third law). Whether a particular force we are looking at in a problem is external or internal depends on how the system is defined. For example, if we define our system as being two stacked books resting on a table (Figure 2.4.1a), the external forces acting on the system are the weights of the two books and the normal contact force exerted by the table on the lower book. The normal contact forces between the two books (the push exerted by the lower book on the upper book and the equal and opposite push exerted by the upper book on the lower book) are Internal Forces (Figure 2.4.1b). Because they are equal in magnitude and opposite in direction, the two members of any pair of Internal Forces sum to zero and therefore cancel each other. Figure 2.4.1 (a) External forces acting on a system of two books; (b) Internal Forces between the two books; (c) external forces acting on a system defined as the upper book; (d) external forces acting on the lower book system. F table on lower book F table on lower book F upper book on lower book F lower book on upper book F upper book on lower book F lower book on upper book W upper W upper W lower W lower (a) (b) (c) (d) If we define our system to be only the upper book, the external forces acting on the system are the weight of the upper book and the normal con- tact force exerted by the lower book on the upper book (Figure 2.4.1c). 2.4 IDENTIFYING FORCES FOR ANALYSIS 41 Finally, if we define our system to be only the lower book, the external forces acting on this system are the weight of the lower book and the nor- mal contact forces exerted by the upper book and by the table on the lower book (Figure 2.4.1d).
eBook - PDFStructures
From Theory to Practice
- Alan Jennings(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
Chapter 3 Internal Forces The discussion of equilibrium is extended to discover what can be found out about the forces and load paths within bodies. Knowledge of the Internal Forces is required whenever strength requirements are under consideration, and also when predicting deflections and their influence on performance. On completion of this chapter you should be able to do the following: • Use the method of sections to determine Internal Forces of statically determinate systems both in 2D and 3D. • Appreciate the significance of principal stresses and how load paths may form within a structure. • Determine bending moment diagrams for three-pinned arches and portal frames. • Determine stresses in cylindrical pressure vessels. • Appreciate the importance of cross-sectional shape on torsional character-istics of members, being able to estimate stresses in some cases. 3.1 T h e m e t h o d of sections Existence of Internal Forces In order to investigate what is happening inside a body in equilibrium, con-sider a part of the body separated from the rest by a cutting line known as a 'section'. It is evident that the body part is not accelerating and so, like the complete body, must be in equilibrium. To achieve this equilibrium, it is normally necessary for additional forces to act on the body part from the adjoining part(s) across the section. When distributed across the interface, the Internal Forces are called 'stresses'. They consist of normal components, 'direct stresses' and tangential components, 'shear stresses'. Whereas equilib-rium conditions alone will not enable stress distributions to be determined, they can be used to determine or provide information on stress resultants, otherwise known as Internal Forces. Internal Forces 121 Ex. 3.1 For the bracket shown in Fig. 3.1, determine the Internal Forces acting across the section AB having a thickness 20 mm, and show that these forces maintain equilibrium of both left-hand and right-hand parts of the bracket.
- Jonathan Wickert, Kemper Lewis, Jonathan Wickert(Authors)
- 2020(Publication Date)
- Cengage Learning EMEA(Publisher)
This relationship can be expressed as F = ma. 3. The forces of action and reaction between two objectives are equal, opposite, and collinear. Element 3: Forces in structures and machines Copyright 2021 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 4.1 Overview 113 In this and the following chapters, we will explore these principles of forces and the problem-solving skills that are needed to understand their effects on engineering hardware. After developing the concepts of force systems, moments, and static equilibrium, you will see how to calculate the magnitudes and directions of forces acting on and within simple structures and machines. In short, the process of analyzing forces is a first step taken by engineers to see whether a certain piece of hardware will operate reliably (Figure 4.1). A second objective of this chapter is for you to start understanding the inner workings of mechanical hardware, beginning with rolling element bearings. Just as an electrical engineer might select off-the-shelf resistors, capacitors, and transistors as the elements of a circuit, mechanical engineers have good intuition for specifying bearings, shafts, gears, belts, and other machine components. A working knowledge of hardware and machine components is important for you to develop a technical vocabulary. Mechanical engineering has its own precise language, and, to communicate effectively with other engineers, you will need to learn, adopt, and share that language.
eBook - PDF- Frank R. Spellman(Author)
- 2015(Publication Date)
- CRC Press(Publisher)
Many accidents and resulting injuries are caused by forces of too great a magnitude for a machine, material, or structure to withstand. To design and inspect systems, devices, or products 190 Handbook of Environmental Engineering to ensure their safety, environmental engineers must account for the forces that act or might act on them. Environmental engineers must also account for forces from objects that may act on the human body (an area of focus that is often overlooked). Important subject areas that are part of or that interface with applied mechanics are the properties of materials, electrical circuits and machines, and engineering design considerations. We cannot discuss all engineering aspects related to these areas in this text; instead, our goal is to look at some fundamental concepts and their relationships to environmental engineering. RESOLUTION OF FORCES With regard to the environmental and occupational health aspects of environmental engineering, we tend to focus our attention on those forces that are likely to cause failure or damage to some device or system, resulting in an occurrence that is likely to produce secondary and tertiary damage to other devices or systems and harm to individuals. Typically, large forces are more likely to cause failure or damage than small ones. Environmental engineers must understand force and how a force acts on a body, particularly (1) the direction of force, (2) point of application (location) of force, (3) the area over which force acts, (4) the distribution or concentration of forces that act on bodies, and (5) how essential these elements are in evaluating the strength of materials. For example, a 40-lb force applied to the edge of a sheet of plastic and parallel to it probably will not break it. If a sledge-hammer strikes the center of the sheet with the same force, the plastic will probably break. A sheet metal panel of the same size undergoing the same force will not break.
eBook - PDF- James L. Meriam, L. G. Kraige, J. N. Bolton(Authors)
- 2020(Publication Date)
- Wiley(Publisher)
CHAPTER 2 Force Systems 2/1 Introduction In this and the following chapters, we study the effects of forces which act on engi- neering structures and mechanisms. The experience gained here will help you in the study of mechanics and in other subjects such as stress analysis, design of structures and machines, and fluid flow. This chapter lays the foundation for a basic understanding not only of statics but also of the entire subject of mechanics, and you should master this material thoroughly. 2/2 Force Before dealing with a group or system of forces, it is necessary to examine the properties of a single force in some detail. A force has been defined in Chapter 1 as an action of one body on another. In dynamics we will see that a force is de- fined as an action which tends to cause acceleration of a body. A force is a vector quantity, because its effect depends on the direction as well as on the magnitude of the action. Thus, forces may be combined according to the parallelogram law of vector addition. CHAPTER OUTLINE 2/1 Introduction 2/2 Force SECTION A Two-Dimensional Force Systems 2/3 Rectangular Components 2/4 Moment 2/5 Couple 2/6 Resultants SECTION B Three-Dimensional Force Systems 2/7 Rectangular Components 2/8 Moment and Couple 2/9 Resultants 2/10 Chapter Review The properties of force systems must be thor- oughly understood by the engineers who design structures such as these overhead cranes. Anze Bizjan/Shutterstock 17 18 CHAPTER 2 Force Systems The action of the cable tension on the bracket in Fig. 2/1a is represented in the side view, Fig. 2/1b, by the force vector P of magnitude P. The effect of this action on the bracket depends on P, the angle , and the location of the point of application A. Changing any one of these three specifications will alter the ef- fect on the bracket, such as the force in one of the bolts which secure the bracket to the base, or the internal force and deforma- tion in the material of the bracket at any point.
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
