Report

ME 418 LAB D1 FATIGUE TESTING Unyime (Uy) Bassey Umoh Email address – [email protected] Office # - 1B70 September 2013 OBJECTIVES 1. 2. 4. ME 418 Lab D1 - 2013 3. To understand the fatigue behaviour of 1018 steel To understand treatments to improve the fatigue strength of 1018 steel To understand the operation of 4 fatigue machines Krouse RR. Moore Budd Warner-Swasey To complete 2 fatigue tests on a standard specimen using a Krouse rotating beam machine Without treatment With treatment 2 LABORATORY TIMELINE Go through concepts of fatigue and equations Carry out calculations relevant towards the Krouse test Observe operation of Krouse machine and carry out test Observe operation of 4 fatigue testing machines Carry out research challenge Record information from Krouse test and sketch sample identifying crack initiation ME 418 Lab D1 - 2013 3 LOGBOOK CHECKLIST ME 418 Lab D1 - 2013 Objectives Background information Lab calculations Information for 4 machines Sketch of Diagrams Method of loading Types of stresses produced Brief description of operation Experiment Number of cycles at failure Sketch of failed specimen Treatment Procedure Justification, and References Future discussion points 4 THEORY – CONCEPTS ME 418 Lab D1 - 2013 Fatigue Failure: Progressive Failure process of a material due to repeated cyclic loading. Loading induces cyclic stresses, which initiates cracks and cause them to be propagated until failure occurs (Collins 43) Stress-time patterns Completely reversed (Zero-mean) cyclic stresses* Nonzero-mean cyclic stresses Random stresses 5 THEORY – CONCEPTS ME 418 Lab D1 - 2013 Fatigue (endurance) Limit: The stress level under which an infinite number of cycles can be sustained without failure of the material. Response of Ferrous materials and Titanium Denoted as Sf for actual machine part and Sf’ for small polished specimen. 6 THEORY – CONCEPTS ME 418 Lab D1 - 2013 Sf Figure 1: S-N curves showing response to cyclic loading http://www.efunda.com/formulae/solid_mechanics/fatigue/images/fatigue_SN_01.gif 7 THEORY – CONCEPTS ME 418 Lab D1 - 2013 Fatigue strength: The stress level at which a material will fail when loaded by N number of cycles. Response of Non-ferrous materials Denoted as SN for actual machine part and SN’ for small polished specimen 8 THEORY – CONCEPTS ME 418 Lab D1 - 2013 N Figure 1: S-N curves showing response to cyclic loading http://www.efunda.com/formulae/solid_mechanics/fatigue/images/fatigue_SN_01.gif 9 THEORY – CONCEPTS ME 418 Lab D1 - 2013 Figure 1: S-N curves for Ferrous and non-ferrous materials (Taken without permission from Collins, J. A. Mechanical Design of Machine Elements and Machines: a Failure Prevention Perspective. New York, NY: Wiley, 2003. Print) 10 THEORY – EQUATIONS SN = 1/6 (S106 - S1).log(N/106) + S106 ME 418 Lab D1 - 2013 *Logarithmic relationship - A straight line between S1 and S106 on a semi-log plot (i.e. SN vs. log[N]): 11 THEORY – EQUATIONS 6 (-1/3log[S SN = S106 . (N/10 ) /S 103 ]) 106 ME 418 Lab D1 - 2013 *Power relationship – A straight line between S103 and S106 on a log-log plot (i.e. log[SN] vs Log[N]): 12 THEORY – EQUATIONS Where: and, CL = Load factor CS = Surface factor CG = Gradient factor CT = Temperature factor CR = Reliability factor SN’ = Endurance limit for a mirror polished specimen Z = Endurance ratio (Estimated as 0.5)* ME 418 Lab D1 - 2013 S1 = SUT SN’ = ZSUT *S103 = 0.9SUT S106 = SN’CLCSCGCT CR 13 LOGBOOK CHECKLIST Sketch of Diagrams Method of loading Types of stresses produced Brief description of operation Experiment ME 418 Lab D1 - 2013 Objectives Background information Lab calculations Information for 4 machines Number of cycles at failure Sketch of failed specimen Treatment Procedure Justification, and References Future discussion points 14 CALCULATIONS (POWER RELATIONSHIP) ME 418 Lab D1 - 2013 Determine: 1) SN NGroup = To be Provided, DGroup = To be Measured, and: SUT = 114 ksi CL = 1 CS = 0.74 CG = 1 CT = 1 CR = 1 Z = 0.5 15 CALCULATIONS 2) Estimated time for test, assuming 5000rpm ME 418 Lab D1 - 2013 3) Moment, M 16 LOGBOOK CHECKLIST Sketch of Diagrams Method of loading Types of stresses produced Brief description of operation Experiment ME 418 Lab D1 - 2013 Objectives Background information Lab calculations Information for 4 machines Number of cycles at failure Sketch of failed specimen Treatment Procedure Justification, and References Future discussion points 17 RESEARCH CHALLENGE Literature search and Brain storming Treatment of same specimen to Increase fatigue strength showing 1. Specimen treatment Temperature Time 2. Justification Mechanical properties Micro-structural considerations 3. Note references ME 418 Lab D1 - 2013 18 AFTER LAB TO DO Treatment Submit treatment procedure within 2 school days Complete treatment within 1 week of acceptance Submit specimen according to schedule posted in 2C26 Email Rob peace – [email protected] Include all treatment results that will be sent out in your logbook Compare strength of heat treated sample with nonheat treated sample Plot S-N relationship from all groups data Assuming power relationship, determine experimental endurance ratio and ultimate strength of the steel Compare S-N for theoretical and experimental ME 418 Lab D1 - 2013 19 LOGBOOK CHECKLIST Sketch of Diagrams Method of loading Types of stresses produced Brief description of operation Experiment ME 418 Lab D1 - 2013 Objectives Background information Lab calculations Information for 4 machines Number of cycles at failure Sketch of failed specimen Treatment Procedure Justification, and References Future discussion points 20