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Full-Text Articles in Engineering
Creep And Fatigue Interaction Characteristics Of Pwa1484, Christian J. Pierce
Creep And Fatigue Interaction Characteristics Of Pwa1484, Christian J. Pierce
Theses and Dissertations
One of the main methods for predicting the service life of jet engine turbine blades is through creep analysis. A sample of the turbine blade material will be mechanically tested to characterize its creep performance. This characterization will be used to determine safe operating conditions for the material. While methods for modeling creep behavior are generally well developed, this constant load creep testing does not fully represent the loading conditions present in a jet engine due to cyclic loading caused by the mission profile and throttle movements. As the industry seeks to become more accurate in physics based modeling of …
Effects Of Environment On Creep Behavior Of Nextel720/Alumina-Mullite Ceramic Composite With ±45º Fiber Orientation At 1200ºc, Muzaffer Ozer
Effects Of Environment On Creep Behavior Of Nextel720/Alumina-Mullite Ceramic Composite With ±45º Fiber Orientation At 1200ºc, Muzaffer Ozer
Theses and Dissertations
The present effort will investigate the off-axis creep behavior of the Nexte720/Alumina-Mullite CMC, a material system which relies on a porous alumina/mullite matrix for damage tolerance as compared to the pure alumina matrix in earlier studies. This research evaluated the creep behavior of N720/AM with a ± 45° fiber orientation at 1200°C in: laboratory air, steam, and argon environments. Creep-rupture tests at the creep stress levels of: 32, 30, 26, and 20 MPa were conducted in each environment. Additionally 35 MPa stress level examined in air and 13 MPa stress level examined both in air and steam. The N720/AM with …
The Effect Of Elevated Temperature On The Fretting Fatigue Behavior Of Nickel Alloy In-100, John F. Ownby
The Effect Of Elevated Temperature On The Fretting Fatigue Behavior Of Nickel Alloy In-100, John F. Ownby
Theses and Dissertations
This thesis studied the effect of elevated temperature (600 C) on the fretting fatigue behavior of IN-100. First, fretting and plain fatigue S-N curves were determined over a large range of applied stress at an identical stress ratio of 0.03 at 600 C and for fretting tests, with a constant contact load. The partial slip condition was verified by using hysteresis between shear force and axial stress techniques. The contact width and the crack initiation location were observed for all of the fretting specimens. The contact widths were consistent with expected values and the crack initiation location was at the …
Effects Of Polishing Shot-Peened Surfaces On Fretting Fatigue Behavior Of Ti-6al-4v, Kasey S. Scheel
Effects Of Polishing Shot-Peened Surfaces On Fretting Fatigue Behavior Of Ti-6al-4v, Kasey S. Scheel
Theses and Dissertations
The research of this thesis was done to investigate the effects of polishing a shot-peened specimen of Ti-6Al-4V on the fretting fatigue life of that specimen. The shot-peening process, though one of the most beneficial techniques in prolonging fretting fatigue life, creates a textured surface that may lead to problems on the micro level. This research was done in an attempt to further improve the peening process by examining the effects of another surface treatment to be used in conjunction, surface polishing. The rough peened surface may contain abrupt changes in surface geometry that act as stress risers, which are …
Tensile Stress Rupture Behavior Of A Woven Ceramic Matrix Composite In Humid Environments At Intermediate Temperature, Kevin J. Larochelle
Tensile Stress Rupture Behavior Of A Woven Ceramic Matrix Composite In Humid Environments At Intermediate Temperature, Kevin J. Larochelle
Theses and Dissertations
Stress rupture tests on the SylramicTM fiber with an in-situ layer of boron nitride, boron nitride interphase, and SiC matrix ceramic matrix composite were performed at 550°C and 750°C with 0.0, 0.2, or 0.6 atm partial pressure of water vapor, pH2O. The 550°C, 100-hr strengths were 75%, 65% and 51% of the monotonic room temperature tensile strength, respectively. At 750°C, the strengths were 67%, 51%, and 49%, respectively. Field Emission Scanning Electron Microscopy analysis estimated the total embrittlement times for 550°C with 0.0, 0.2, and 0.6 atm pH2O were >63 hrs, >38 hrs, and between …
Effects Of Variable Contact Load On Fretting Fatigue Behavior Of Shot-Peened And Un-Peened Titanium Alloy, Chia-Hawa Lee
Effects Of Variable Contact Load On Fretting Fatigue Behavior Of Shot-Peened And Un-Peened Titanium Alloy, Chia-Hawa Lee
Theses and Dissertations
Fretting fatigue occurs between two components in contact under relative motion and reduces fatigue life when compared with plain fatigue. Shot-peening, on the other hand, is the most commonly used cold working process to improve material fatigue resistance in aeronautical industries. Nearly all work accomplished to date has assumed a constant contact load while investigating fretting fatigue. The primary goal of this study was to explore fretting fatigue behavior under constant and variable contact load configurations using both shot-peened and un-peened specimens made up of Ti-6Al-4V alloy. Contact loads were applied with four different frequencies. Applied axial loads were also …
Role Of Plasticity On Fretting Fatigue Behavior Of Ti-6al-4v, Kisu Shin
Role Of Plasticity On Fretting Fatigue Behavior Of Ti-6al-4v, Kisu Shin
Theses and Dissertations
Fretting fatigue generally leads to the degradation of the fatigue strength of a material due to cyclic micro-slip between two contacting materials. Fretting fatigue is regarded as an important issue in designing aerospace structures. While many studies have evaluated fretting fatigue behavior under elastic deformation conditions, few studies have focused on fretting fatigue behavior under elastic-plastic deformation conditions. The primary goal of this study was to characterize the fretting fatigue crack initiation behavior in the presence of plasticity. Experimental tests were performed using pad configurations involving elastic-plastic deformations. In order to calculate stress distributions under elastic-plastic fretting fatigue conditions, FEA …
An Electromagnetic Tool For Damping And Fatigue Analysis, Todd M. Hoover
An Electromagnetic Tool For Damping And Fatigue Analysis, Todd M. Hoover
Theses and Dissertations
An automated test system was developed by the USAF Turbine Engine Fatigue Facility (TEFF). This system was initially designed to reduce the time and manpower required to characterize damping treatments. It is based on a digitally controlled environmental chamber with automated data acquisition and processing. Several outputs are available including identification of natural frequencies, modal damping ratios from the acquired frequency responses, and changes in damping with response amplitude; however, the TEFF additionally desires the capability to study fatigue under a free boundary condition. The system consists of a test specimen suspended by a pendulum to closely simulate free boundary …
Effect Of A Variable Contact Load On Fretting Fatigue Behavior Of Ti-6al-4v, Andrew J. Jutte
Effect Of A Variable Contact Load On Fretting Fatigue Behavior Of Ti-6al-4v, Andrew J. Jutte
Theses and Dissertations
Effects of a variable contact load on the high cycle fretting fatigue behavior of Ti-6AL-4V were investigated. Experimental tests were performed using a new test setup capable of applying a contact load varying in amplitude, frequency, and phase and independently measuring shear forces on opposite sides of a specimen. Finite element analysis (FEA) of experimental and idealized loading conditions was performed and local mechanistic parameters and the Modified Shear Stress Range (MSSR) fatigue parameter were determined. Correlations between contact width, slip amplitude, fatigue life and a variable contact load were established with variable contact loading shown to have a damaging …
Determination And Studying Of Stress Distribution In Various Ankle-Foot Orthoses : Experimental Stress Analysis, Rong Feng
Theses
Ankle-Foot Orthosis (AFO) is prescribed to constrain and inhibit abnormal motion such as "drop foot" due to stroke. Most orthoses were hand-made by orthotists according to their own experience. However, some types of AFO were easy to fatigue (out of their functional capabilities) than others due to regular usage. In order to improve the design and usage, quantitative stress analysis of different types of orthoses is needed. The objective of this project is to obtain experimental data which will confirm the results obtained from previous Finite Element Analysis (FEA)[1]. In addition, the experimental analysis is extended to obtain …