上海交通大学：《工程学导论》课程教学资源（讲义）Technical knowledge_1Solid Mechanics

Introduction to Engineering-Solid Mechanics Solid Mechanics Introduction to Engineering 1 H.Shao

Introduction to Engineering Introduction to Engineering —— Solid Mechanics Solid Mechanics Introduction to Engineering Introduction to Engineering H. Shao 1 Solid Mechanics Solid Mechanics

Introduction to Engineering-Solid Mechanics Objectives After this chapter,you should be able to ldentify different types of basic loading conditions Understand the basic approach of the Finite Element Method Introduction to Engineering 2 H.Shao

Introduction to Engineering Introduction to Engineering —— Solid Mechanics Solid Mechanics Introduction to Engineering Introduction to Engineering H. Shao 2 Objectives After this chapter, you should be able to :  Identify different types of basic loading conditions  Understand the basic approach of the Finite Element Method

Introduction to Engineering-Solid Mechanics Contents 1.Introduction 2.Stress and Strain 3.Shear 4.Torsion 5.Response of Engineering Material 6.Stress Concentration 7.Fatigue 8.Finite Element Method (FEM) Introduction to Engineering 3 H.Shao

Introduction to Engineering Introduction to Engineering —— Solid Mechanics Solid Mechanics Introduction to Engineering Introduction to Engineering H. Shao 3 Contents 1. Introduction 2. Stress and Strain 3. Shear 4. Torsion 5. Response of Engineering Material 6. Stress Concentration 7. Fatigue 8. Finite Element Method (FEM)

Introduction to Engineering-Solid Mechanics 1.Introduction Predicting the deformation of a body is very important in engineering design and analysis The inverse problem is also important: -Given the amount of desired deformation,find the corresponding load Structural Mechanics Solid Mechanics: Mechanics of Materials Elastic Mechanics Plastic Mechanics Introduction to Engineering 4 H.Shao

Introduction to Engineering Introduction to Engineering —— Solid Mechanics Solid Mechanics Introduction to Engineering Introduction to Engineering H. Shao 4 1. Introduction Structural Mechanics Mechanics of Materials Elastic Mechanics. Plastic Mechanics Solid Mechanics :  Predicting the deformation of a body is very important in engineering design and analysis  The inverse problem is also important: –Given the amount of desired deformation, find the corresponding load

Introduction to Engineering-Solid Mechanics 1.Introduction Failure of a hardware: ■Break Excessive deformation (e.g.stretch,or bend too much) Designed component should never fail Introduction to Engineering 5 H.Shao

Introduction to Engineering Introduction to Engineering —— Solid Mechanics Solid Mechanics Introduction to Engineering Introduction to Engineering H. Shao 5 1. Introduction  Failure of a hardware:  Break  Excessive deformation (e.g. stretch, or bend too much)  Designed component should never fail

Introduction to Engineering-Solid Mechanics 1.Introduction The failure of a machine component depends on Forces that are applied to it ■Its dimensions Properties of the material ■Shapes We will discuss various types of stresses that can develop within machine components Introduction to Engineering 6 H.Shao

Introduction to Engineering Introduction to Engineering —— Solid Mechanics Solid Mechanics Introduction to Engineering Introduction to Engineering H. Shao 6 1. Introduction The failure of a machine component depends on  Forces that are applied to it  Its dimensions  Properties of the material  Shapes We will discuss various types of stresses that can develop within machine components

Introduction to Engineering-Solid Mechanics 2.Stress and Strain Tension and Compression unstretched (a)Unstretched length and diameter (b)As the force is gradually applied, the rod stretches along its length by the amount 4L.Ad is (a) A=πdP14 the change in diameter AL< (b) Note:Engineers usually calculate the cross-sectional area of round rods,bolts,and shafts in terms of their diameter,rather than radius,because the diameter can be directly measured with a caliper gauge. Introduction to Engineering 7 H.Shao

Introduction to Engineering Introduction to Engineering —— Solid Mechanics Solid Mechanics Introduction to Engineering Introduction to Engineering H. Shao 7 2. Stress and Strain Tension and Compression (a) Unstretched length and diameter (b) As the force is gradually applied, the rod stretches along its length by the amount ΔL. Δd is the change in diameter Note: Engineers usually calculate the cross-sectional area of round rods, bolts, and shafts in terms of their diameter, rather than radius, because the diameter can be directly measured with a caliper gauge. L Δd ΔL d (a) (b) unstretched A=πd2/4

Introduction to Engineering-Solid Mechanics 2.Stress and Strain When the force is removed: 。Elastic Behavior The rod will spring back to its original diameter and length, the stretching is said to occur elastically. ·Plastic Behavior The rod would end up being longer than it was initially,the rod have been plastically deformed. Introduction to Engineering 8 H.Shao

Introduction to Engineering Introduction to Engineering —— Solid Mechanics Solid Mechanics Introduction to Engineering Introduction to Engineering H. Shao 8 2. Stress and Strain When the force is removed: • Elastic Behavior – The rod will spring back to its original diameter and length, the stretching is said to occur elastically. • Plastic Behavior – The rod would end up being longer than it was initially, the rod have been plastically deformed

Introduction to Engineering-Solid Mechanics 2.Stress and Strain Internal Force The force applied at one end of the rod influences each cross section along the rod's length Slicing the bar at some point: The segment of rod in the free body diagram F acting at its right-hand end An interna/force at the segment's left-hand end that balances F. (a) (b) Introduction to Engineering 9 H.Shao

Introduction to Engineering Introduction to Engineering —— Solid Mechanics Solid Mechanics Introduction to Engineering Introduction to Engineering H. Shao 9 2. Stress and Strain Internal Force – The force applied at one end of the rod influences each cross section along the rod’s length – Slicing the bar at some point: • The segment of rod in the free body diagram • F acting at its right-hand end • An internal force at the segment’s left-hand end that balances F. (a) (b) F F F

Introduction to Engineering-Solid Mechanics 2.Stress and Strain Stress -The rod is formed of a solid continuous material Instead of concentrated at a point,the internal force spreads out over the cross section - Tensile stress,is the applied force per unit of original cross- sectional area F A (c) When the stress tends to lengthen the rod,it is called tension, and o >0. When the rod tends to be shortened,the stress is called compression.and o 0. Introduction to Engineering 10 H.Shao

Introduction to Engineering Introduction to Engineering —— Solid Mechanics Solid Mechanics Introduction to Engineering Introduction to Engineering H. Shao 10 2. Stress and Strain Stress – The rod is formed of a solid continuous material – Instead of concentrated at a point, the internal force spreads out over the cross section – Tensile stress, is the applied force per unit of original cross￾sectional area  When the stress tends to lengthen the rod, it is called tension, and σ >0.  When the rod tends to be shortened, the stress is called compression. and σ < 0. σ (c) F A F  