Chapter 7 Fatigue Failure Resulting from Variable Loading

Slides:



Advertisements
Similar presentations
R1.3 RESP1.3 RESPONSE OF CIVIL ENGIONEEONSE OF CIVIL ENGINEERING PROJECT 1.3 RESPONSE OF CIVIL ENGINEERING PROJECT 1.3 RESPONSE OF CIVIL ENGINEERING PROJECT.
Advertisements

ME 240: Introduction to Engineering Materials Chapter 8. Failure 8.1 CHAPTER 8.
Lecture 9 - Flexure June 20, 2003 CVEN 444.
CREEP  It can be defined as the slow & progressive (increasingly continuing) deformation of a material with time under a constant stress.  It is both.
Manufacturing Technology
Design of Machine Elements
Chapter 3 – Stress and Deformation Analysis (ref MCHT 213!!)
CTU in Prague, Faculty of Mechanical Engineering DAF Page 1 Concentration factors Shape Factor or Stress Concentration Factor of an Elastic Stress Relative.
CHAPTER 7 Fatigue Failure Resulting from Variable Loading
Fatigue Failure Resulting from Variable Loading
Section VI Shaft Design.
Chapter Outline Shigley’s Mechanical Engineering Design.
ME 388 – Applied Instrumentation Laboratory Fatigue Lab.
Chapter 18 Shafts and Axles Dr. A. Aziz Bazoune
Chapter 18 Shafts and Axles Dr. A. Aziz Bazoune
Design of Machine Elements
Chapter 18 Shafts and Axles Dr. A. Aziz Bazoune
DESIGNING AGAINST FATIGUE
Screws, Fasteners, and the Design of Nonpermanent Joints
7. Fatigue Fracture Fracture surface of a bicycle spoke made of 7075-T6 aluminum alloy 25 × magnification 100 × magnification.
FATIGUE TEST EXPERIMENT # 5 Instructor: M.Yaqub. FATIGUE.
ME 307 Machine Design I Dr. A. Bazoune Chapter 7: Fatigue Failure Resulting from variable Loading Dr. A. Aziz Bazoune King Fahd University of Petroleum.
Chapter 5 – Design for Different Types of Loading
Section VI Shaft Design.
Chapter 6 Fatigue Failure Theories
© 2011 Autodesk Freely licensed for use by educational institutions. Reuse and changes require a note indicating that content has been modified from the.
Screws, Fasteners, and the Design of Nonpermanent Joints
ME 307 Machine Design I ME 307 Machine Design I Dr. A. Aziz BazouneChapter 8: Screws, Fasteners and the Design of Nonpermanent Joints CH-8 LEC 35 Slide.
© 2011 Autodesk Freely licensed for use by educational institutions. Reuse and changes require a note indicating that content has been modified from the.
Critical Plane Approach in Stage I and Stage II of Fatigue Under Multiaxial Loading A. KAROLCZUK E. MACHA Opole University of Technology, Department of.
Design Agains Fatigue - part Fatigue Endurance Prediction Design Agains Fatigue - part Fatigue Endurance Prediction Milan Růžička
Chapter 7 Fatigue Failure Resulting from Variable Loading
Chapter 7 Fatigue Failure Resulting from Variable Loading
9 Torsion.
Chapter 7 Fatigue Failure Resulting from Variable Loading
Screws, Fasteners, and the Design of Nonpermanent Joints
DESIGN FOR FATIGUE STRENGTH
1 Jiangyu Li, University of Washington Lecture 18 Fatigue Mechanical Behavior of Materials Sec Jiangyu Li University of Washington Mechanics of.
Chapter 7 Fatigue Failure Resulting from Variable Loading
FATIGUE Fatigue of Materials (Cambridge Solid State Science Series) S. Suresh Cambridge University Press, Cambridge (1998)
Fatigue Failure Due to Variable Loading
1 Design for Different Type of Loading Lecture Notes Dr. Rakhmad Arief Siregar Kolej Universiti Kejuruteraan Utara Malaysia Machine Element in Mechanical.
Failure Criteria and stress concentration
Chapter 9 Welding, Bonding, and the Design of Permanent Joints
FATIGUE Fatigue of Materials (Cambridge Solid State Science Series) S. Suresh Cambridge University Press, Cambridge (1998) MATERIALS SCIENCE &ENGINEERING.
MECH 401 Mechanical Design Applications Dr. M. O’Malley– Master Notes
Machine Design I (MCE-C 203) Mechatronics Dept., Faculty of Engineering, Fayoum University Dr. Ahmed Salah Abou Taleb Lecturer, Mechanical Engineering.
1 INTRODUCTION TO DESIGN SKMM 1512 Semester 2 Session 2014/2015.
Jiangyu Li, University of Washington Yielding and Failure Criteria Plasticity Fracture Fatigue Jiangyu Li University of Washington Mechanics of Materials.
Course No.: MEBF ZC342 MACHINE DESIGN
ENT 353 Advanced Mechanical Design Dr. Haftirman /Shah Fenner Khan/Ahmad Yusri 1 ENT 353 ADVANCED MECHANICAL DESIGN Lecture 2. Fatigue of Metals 16/07/2007.
D ESIGN C ONCEPTS & M/ C D RAWING ME-309 DME-I Prepared By: Prof. Ketul Brahmbhatt.
EGM 5653 Advanced Mechanics of Materials
153 書名: Essentials of Mechanical Engineering Design, 1/E 作者: Shigey Mischke Budynas 書號: MX0398.
The McGraw-Hill Companies © 2012
Engineering properties of rock Prepared by :- Kumari Pooja 3 rd sem civil department 13oo
Engg College Tuwa Mechanics of Solids.( ) Presented by: PARMAR CHETANKUMAR VIKRAMSINH PARMAR NILESHKUMAR NATVARLAL PARMAR.
ME 307 Machine Design I ME 307 Machine Design I. ME 307 Machine Design I ME 307 Machine Design I 8-1 Thread Standards and Definitions 8-2The Mechanics.
Hasmukh Goswami College Of Engineering
ATMIYA INSTITUTE OF TECHNOLOGY & SCIENCE MECHNICAL DEPARTMENT
UNIVERSITY OF NAIROBI DEPARTMENT OF MECHANICAL AND MANUFACTURING ENGINEERING ENGINEERING DESIGN II FME 461 PART 5 GO NYANGASI November 2008.
DEPARTMENT OF MECHANICAL AND MANUFACTURING ENGINEERING
FLUCTUATING STRESSES SUBJECT: Design of machine elements
MECH 401 Mechanical Design Applications Dr. M. O’Malley– Master Notes
Stress Concentration Effect
Methods to Maximize Design Life
Chapter 9 Welding, Bonding, and the Design of Permanent Joints
Mechanics of Materials Lab
Lab8: Fatigue Testing Machine
Lab8: Fatigue Testing Machine
Presentation transcript:

Chapter 7 Fatigue Failure Resulting from Variable Loading Dr. A. Aziz Bazoune King Fahd University of Petroleum & Minerals Mechanical Engineering Department

Chapter Outline 7-1 Introduction to Fatigue in Metals     306 7-2 Approach to Fatigue Failure in Analysis and Design    312 7-3 Fatigue-Life Methods    313 7-4 The Stress-Life Method    313 7-5 The Strain-Life Method    316 7-6 The Linear-Elastic Fracture Mechanics Method    319 7-7 The Endurance Limit    323 7-8 Fatigue Strength    325 7-9 Endurance Limit Modifying Factors    328 7-10 Stress Concentration and Notch Sensitivity    335 7-11 Characterizing Fluctuating Stresses    344 7-12 Fatigue Failure Criteria for Fluctuating Stress    346 7-13 Torsional Fatigue Strength under Fluctuating Stresses    360 7-14 Combinations of Loading Modes    361 7-15 Varying, Fluctuating Stresses; Cumulative Fatigue Damage    364 7-16 Surface Fatigue Strength    370 7-17 Stochastic Analysis    373

LECTURE-22 7-9 Endurance Limit Modifying Factors 7-10 Stress Concentration and Notch Sensitivity

7-9 Endurance Limit Modifying Factors The rotating-beam specimen used in the laboratory to determine endurance limits is prepared very carefully and tested under closely controlled conditions. It is unrealistic to expect the endurance limit of a mechanical or structural member to match the values obtained in the laboratory. Some differences include Material: composition, basis of failure, variability Manufacturing: method, heat treatment, fretting corrosion, surface condition, stress concentration Environment: corrosion, temperature, stress state, relaxation times Design: size, shape, life, stress state, stress concentration, speed, fretting, galling

Marin’s Equation    Marin identified factors that quantified the effects of surface condition size loading temperature miscellaneous items Marin’s Equations is therefore written as: (7-17)

Marin’s Equation rotary-beam test specimen endurance limit (7-17) Endurance limit at the critical location of a machine part in geometry and condition of use rotary-beam test specimen endurance limit

(7-18) where is the minimum tensile strength and and are to be found in Table 7-4. Notice that and are different from those given by Eqs. (7-13) and (7-14) respectively. Table 7-4 Parameters for Marin surface modification factor, Eq. (7-18)

The size factor for bending and torsion may be given by: (7-19) For axial loading there is no size effect, so (7-20)

Non-Rotating Parts If a round bar in bending is not rotating or when a non-circular cross-section is used what is kb ? Assume that fatigue damage occurs in material that is stressed above 95% of its maximum stress. Equate the portion of a non-round part stressed with the similarly stressed area of a rotating beam specimen and obtain the effective diameter where. (7-23) as the effective size of a round corresponding to a non-rotating solid or hollow round. Table 7-5 provides areas of common structural shapes undergoing non-rotating bending.

Table 7-5 Areas of common non-rotating structural shapes Use de Eq. (7-23) for round and Eq.(7-24) for rectangular cross-sections

General form of load factor (7-25) Average kpsi MPa Bending 1 Axial 1.23 1.43 -0.078 0.85 Torsion 0.328 0.258 0.125 0.59 Values given in Textbook

(7-26) where

(7-27) Table 7-6 Effect of operating temperature on the tensile strength of steel.

If Reliability is not mentioned Otherwise Use Table 7-7 Table 7-7 Reliability factor Ka corresponding to 8% standard deviation of the endurance limit. If Reliability is not mentioned Otherwise Use Table 7-7

Residual stresses Directional characteristics (e.g. rolling, drawing) Corrosion Plating Metal spraying Frequency of cycling Fretting corrosion

7-10 Stress Concentration Factor and Notch Sensitivity In Chapter 4, it was pointed out that: The existence of irregularities or discontinuities, such as holes, grooves or notches, in a part increases the theoretical stresses significantly in the immediate vicinity of discontinuity. (4-48)

7-10 Stress Concentration Factor and Notch Sensitivity    

7-10 Stress Concentration Factor and Notch Sensitivity In fatigue: Stress concentration should always be taken into account.

7-10 Stress Concentration Factor and Notch Sensitivity Some materials are not fully sensitive to notches and a reduced value of Kt is used and the maximum stress is calculated as follows: (7-29) Kf is the fatigue stress concentration factor, for simple loading: (Ex 7.7) or

Notch sensitivity q index is defined by (7-39) q for steel and Al alloys are given in Fig. 7-20 for reversed bending or reversed axial load for reversed torsion use Fig. 7.21. For cast iron use q = 0.20 to be conservative.

Figure 7-20 and Figure 7-21: Notch sensitivity curves.

References Design Theory http://deseng.ryerson.ca/DesignScience/ http://www-3.ibm.com/ibm/easy/eou_ext.nsf/Publish/6   Resources http://www.machinedesign.com/ASP/enggMechanical.asp?catId=373 http://www.engineersedge.com/ http://www.bearings.machinedesign.com/guiEdits/Content/BDE_6_4/bdemech_a02.aspx http://icrank.com/cgi-bin/pageman/pageout.cgi?path=/index_html.html Manufacturing http://www.efunda.com/processes/processes_home/process.cfm http://www.me.gatech.edu/jonathan.colton/me4210/mfgvideos.html