Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


mellott stephenFE.pdf (19.14 MB)

ETD Abstract Container

Abstract Header

Tensile, Creep, and Fatigue Behaviors of Thermoplastics Including Thickness, Mold Flow Direction, Mean Stress, Temperature, and Loading Rate Effects

Mellott, Stephen Richard
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1344541288

Abstract Details

2012, Master of Science in Mechanical Engineering, University of Toledo, College of Engineering.
The overall objective of this study was to conduct a systematic and comprehensive experimental investigation to evaluate and quantify the tensile, creep, and fatigue behaviors of two thermoplastic polymers. The effects considered in this experimental study include mold flow direction, thickness, mean stress, temperature, and loading rate. Specimens were subjected to monotonic tension, creep, and load-controlled fatigue tests. The two materials considered were a neat impact polypropylene and a mineral and elastomer reinforced polyolefin. A unique test specimen geometry was developed for this study along with a procedure for fatigue testing. Tensile tests were performed at various strain rates at room, -40¿¿C, and 85¿¿C temperatures with specimens cut parallel and perpendicular to the mold flow direction. Tensile properties including elastic modulus, ultimate tensile strength, yield strength, and strain at the ultimate tensile strength were determined from these tests. The Ramberg-Osgood model for metals was used to model the tensile deformation behavior, in addition to other models specific to polymeric materials. Creep tests were conducted at room temperature, 85¿¿C, and 125¿¿C at various stress levels, and data from these tests were used to model the creep deformation behavior by a power-law model for both materials. The effect of creep damage in fatigue tests with mean stress was also investigated with a linear damage model. Fatigue tests were performed with test specimens of two different thicknesses and cutting directions with respect to the mold flow. These tests were performed at room temperature, -40¿¿C and 85¿¿C in tension-compression and tension-tension. Several frequencies were used for the same stress levels to examine the effect of frequency on fatigue life. Prediction of stress-life fatigue properties from tensile properties was also examined and compared to existing predictions from tensile properties for steels. The effect of mean stress was modeled using various parameters developed for metals and with models specific to polymeric materials obtained from a literature review. In terms of effectiveness, the Walker equation and a simple model with a mean stress sensitivity factor (¿¿) proved to be the most effective. Incremental step cyclic deformation tests were performed to generate cyclic stress-strain curves to enable the determination of strain-life fatigue properties from stress-controlled tests. The effect of self-heating under cyclic loading was modeled with tests that measured the specimen surface temperature as a function of the applied stress amplitude and cycling frequency.
Dr. Ali Fatemi (Advisor)
Dr. Saleh Jabarin (Committee Member)
Dr. Yong Gan (Committee Member)
328 p.
Materials Science
tensile; creep; fatigue; thermoplastic

Recommended Citations

Citations

  • Mellott, S. R. (2012). Tensile, Creep, and Fatigue Behaviors of Thermoplastics Including Thickness, Mold Flow Direction, Mean Stress, Temperature, and Loading Rate Effects [Master's thesis, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1344541288

    APA Style (7th edition)

  • Mellott, Stephen. Tensile, Creep, and Fatigue Behaviors of Thermoplastics Including Thickness, Mold Flow Direction, Mean Stress, Temperature, and Loading Rate Effects. 2012. University of Toledo, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1344541288.

    MLA Style (8th edition)

  • Mellott, Stephen. "Tensile, Creep, and Fatigue Behaviors of Thermoplastics Including Thickness, Mold Flow Direction, Mean Stress, Temperature, and Loading Rate Effects." Master's thesis, University of Toledo, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1344541288

    Chicago Manual of Style (17th edition)

toledo1344541288
705
© 2012, all rights reserved.
This open access ETD is published by University of Toledo and OhioLINK.