## Machine Design Theories of failure and Design for fatigue

### What you’ll learn

Principal stress and their importance

Maximum Shear stress theory of failure

Maximum distortion Energy theory

Mohr and Columb mohr theory

Designing for Fatigue and Basics of fracture mechanics

Definition of endurance limit and strength

Modifying factors for Endurance strength

Defining failure criteria in fatigue

### Requirements

Understanding of strength of materials or mechanics of materials is desirable to understand the concepts in the course

### Description

Machine design is the practice of designing structural elements of a product to meet functional and durability criteria .Failure prevention is a big part of study for Machine design . This course deals with the various theories of failure in Static and dynamic (cyclic) loading conditions.Basics of Principal stress from mechanics of materials Importance of principal stressWhat are Theories of failure? the most simplest formMaximum Shear stress Theory – How it is derived , the analysis and cases Maximum distortion Energy theory – the most widely used theory of failure for ductile materials The derivation from concept of strain energyDefinition of Von mises stressMohr theory – Theory for materials with different tensile and compressive strengthsCoulomb- Mohr theoryBrittle Failure theorySelection of Failure theory What is Fatigue loading? fatigue failure?Fracture mechanics basicsWhat is fracture toughness property Factors to be consideredThe S-N curve and RR Moore test to develop S-N curveEndurance strength and Endurance limitThe Endurance limit modifying factorsSurface, Size, temperature, loading Stress concentration factor Characterization of cyclical loadingDefinition of failure criteria in FatigueThe course is designed to be compact and to the point highlighting the most important concepts and the Why ? behind it. This is an advanced level course suitable if you are already familiar with strength of materials or mechanics of materials and basics of mechanical engineering .

### Overview

Section 1: Introduction

Lecture 1 Introduction

Lecture 2 What is Mechanical Failure ? What are theories of failure?

Lecture 3 Failure criteria and importance of Principal stresses

Lecture 4 Definition of Principal stresses

Lecture 5 Mohrs circle and formulae for principal stresses

Lecture 6 3D General State of Stress

Lecture 7 Principal stresses in 3D general state of stress

Section 2: Maximum Shear Stress theory

Lecture 8 Maximum Shear stress theory- introduction

Lecture 9 Criteria for Failure according to MSS

Lecture 10 Cases in Max shear stress theory

Section 3: Maximum Distortion Energy theory

Lecture 11 Strain energy

Lecture 12 Strain energy density

Lecture 13 Strain energy density in Shear

Lecture 14 Strain energy in general state of stress

Lecture 15 Maximum Distortion Energy theory

Lecture 16 Finding the Distortion Energy component

Lecture 17 Criteria for Max Distortion Energy theory

Lecture 18 Definition of Von Mises Stress and comparison with Maximum shear stress Theory

Section 4: Mohrs Criteria for Failure

Lecture 19 Mohrs criterion for ductile materials

Lecture 20 Mohrs criteria- envelope derivation

Lecture 21 Mohr coulumb theory of failure

Lecture 22 Cases in Mohr coulumb theory of failure

Lecture 23 Brittle Coulumb mohr theory

Lecture 24 Maximum principal stress theory for brittle materials and its drawback

Lecture 25 Selecting Failure theory in design practice

Section 5: Fatigue

Lecture 26 Limitations of traditional mechanics methods in design

Lecture 27 What is Fatigue failure?

Lecture 28 Types of loadings – static and dynamic

Lecture 29 Stages leading to fatigue failure

Lecture 30 Modes of Fracture

Lecture 31 Generic Factors which affect fatigue

Lecture 32 Important checkpoints in fracture mechanics study

Lecture 33 Fracture toughness material property

Section 6: Design for Fatigue

Lecture 34 Approach to fatigue problems

Lecture 35 Fatigue Life method, RR moore test , S-N diagram

Lecture 36 Plotting and Deciphering the S-N curve

Lecture 37 Typical values of Endurance and Fatigue strength

Lecture 38 Modifying factors for Endurance limit/strength

Lecture 39 Surface modification factor

Lecture 40 Size modification factor

Lecture 41 Loading factor

Lecture 42 Temperature factor

Lecture 43 Reliability factor

Lecture 44 Stress concentration Factor – for Statics study

Lecture 45 Fatigue stress concentration factor

Lecture 46 Some points on Designing with Fatigue

Section 7: Fatigue failure criteria

Lecture 47 Fluctuating stress types, mean and amplitude stress

Lecture 48 Goodman diagram and other criteria with factor of safety

Section 8: Bonus Section

Lecture 49 Bonus : More resources for learning Mechanical engineering and design

Mechanical Engineering students,Design engineers looking to refresh their basics in Machine design,Anyone interested in mechanical and machine design

#### Course Information:

Udemy | English | 2h 50m | 768.63 MB

Created by: Mufaddal Rasheed

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