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- Creators: Barrett, The Honors College
- Creators: Solanki, Kiran
- Status: Published
Description
Aluminum alloys and their composites are attractive materials for applications requiring high strength-to-weight ratios and reasonable cost. Many of these applications, such as those in the aerospace industry, undergo fatigue loading. An understanding of the microstructural damage that occurs in these materials is critical in assessing their fatigue resistance. Two distinct experimental studies were performed to further the understanding of fatigue damage mechanisms in aluminum alloys and their composites, specifically fracture and plasticity. Fatigue resistance of metal matrix composites (MMCs) depends on many aspects of composite microstructure. Fatigue crack growth behavior is particularly dependent on the reinforcement characteristics and matrix microstructure. The goal of this work was to obtain a fundamental understanding of fatigue crack growth behavior in SiC particle-reinforced 2080 Al alloy composites. In situ X-ray synchrotron tomography was performed on two samples at low (R=0.1) and at high (R=0.6) R-ratios. The resulting reconstructed images were used to obtain three-dimensional (3D) rendering of the particles and fatigue crack. Behaviors of the particles and crack, as well as their interaction, were analyzed and quantified. Four-dimensional (4D) visual representations were constructed to aid in the overall understanding of damage evolution. During fatigue crack growth in ductile materials, a plastic zone is created in the region surrounding the crack tip. Knowledge of the plastic zone is important for the understanding of fatigue crack formation as well as subsequent growth behavior. The goal of this work was to quantify the 3D size and shape of the plastic zone in 7075 Al alloys. X-ray synchrotron tomography and Laue microdiffraction were used to non-destructively characterize the volume surrounding a fatigue crack tip. The precise 3D crack profile was segmented from the reconstructed tomography data. Depth-resolved Laue patterns were obtained using differential-aperture X-ray structural microscopy (DAXM), from which peak-broadening characteristics were quantified. Plasticity, as determined by the broadening of diffracted peaks, was mapped in 3D. Two-dimensional (2D) maps of plasticity were directly compared to the corresponding tomography slices. A 3D representation of the plastic zone surrounding the fatigue crack was generated by superimposing the mapped plasticity on the 3D crack profile.
ContributorsHruby, Peter (Author) / Chawla, Nikhilesh (Thesis advisor) / Solanki, Kiran (Committee member) / Liu, Yongming (Committee member) / Arizona State University (Publisher)
Created2014
Description
Widespread knowledge of fracture mechanics is mostly based on previous models that generalize crack growth in materials over several loading cycles. The objective of this project is to characterize crack growth that occurs in titanium alloys, specifically Grade 5 Ti-6Al-4V, at the sub-cycle scale, or within a single loading cycle. Using scanning electron microscopy (SEM), imaging analysis is performed to observe crack behavior at ten loading steps throughout the loading and unloading paths. Analysis involves measuring the incremental crack growth and crack tip opening displacement (CTOD) of specimens at loading ratios of 0.1, 0.3, and 0.5. This report defines the relationship between crack growth and the stress intensity factor, K, of the specimens, as well as the relationship between the R-ratio and stress opening level. The crack closure phenomena and effect of microcracks are discussed as they influence the crack growth behavior. This method has previously been used to characterize crack growth in Al 7075-T6. The results for Ti-6Al-4V are compared to these previous findings in order to strengthen conclusions about crack growth behavior.
ContributorsNazareno, Alyssa Noelle (Author) / Liu, Yongming (Thesis director) / Jiao, Yang (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
This paper presents the methods and materials used to investigate the fatigue fracture properties of i) seamless twill weave carbon fiber and ii) stitch bonded biaxial carbon fiber polymer matrix composite. Additionally, the effect of notch tip placement relative to longitudinal fiber toes is investigated. The process for observing and characterizing fatigue crack damage propagation is presented. The fatigue fracture behavior is compared with data acquired from compact tension samples subjected to static tension tests in order to develop damage tolerant design guidelines for tube structures under fatigue loading.
ContributorsOramas, Mateo Alexis (Author) / Chattopadhyay, Aditi (Thesis director) / Yekani Fard, Masoud (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
The use of solar energy to produce power has increased substantially in the past few decades. In an attempt to provide uninterrupted solar power, production plants may find themselves having to operate the systems at temperatures higher than the operational capacity of the materials used in many of their components, which affects the microstructural and mechanical properties of those materials. Failures in components that have been exposed to these excessive temperatures have been observed during operations in the turbine used by AORA Solar Ltd. A particular component of interest was made of a material similar to the Ni-based superalloy Inconel 718 (IN 718), which was observed to have damage that is believed to have been initiated by Foreign Object Damage (FOD) and worsened by the high temperatures in the turbine. The potential links among the observed failure, FOD and the high temperatures of operation are investigated in this study.
IN718 is a precipitation hardened nickel superalloy with resistance to oxidation and ability to withstand high stresses over a wide range of temperatures. Several studies have been conducted to understand IN 718 tensile and fatigue properties at elevated temperatures (600- 950°C). However, this study focuses on understanding the behavior of IN718 with FOD induced by a stream of 50 μm Alumina particles at a velocity of 200 m/s. under high cycle fatigue at an elevated temperature of 1050 °C. Tensile tests were conducted for both as-received and heat treated (1050 °C in air for 8hrs) samples at room and high temperature. Fatigue tests were performed at heat treated samples at 1050 °C for samples with and without ablation. The test conditions were as similar as possible to the conditions in the AORA turbine. The results of the study provide an insight into tensile properties, fatigue properties and FOD. The results indicated a reduction in fatigue life for the samples with ablation damage, where crack nucleation occurred either at the edge or inside the ablation region and multisite cracking was observed under far field stresses that were the same than for pristine samples, which showed single cracks. Fracture surfaces indicate intergranular fracture, with the presence of secondary cracks and a lack of typical fatigue features, e.g., beach marks which was attributed to environmental effects and creep.
IN718 is a precipitation hardened nickel superalloy with resistance to oxidation and ability to withstand high stresses over a wide range of temperatures. Several studies have been conducted to understand IN 718 tensile and fatigue properties at elevated temperatures (600- 950°C). However, this study focuses on understanding the behavior of IN718 with FOD induced by a stream of 50 μm Alumina particles at a velocity of 200 m/s. under high cycle fatigue at an elevated temperature of 1050 °C. Tensile tests were conducted for both as-received and heat treated (1050 °C in air for 8hrs) samples at room and high temperature. Fatigue tests were performed at heat treated samples at 1050 °C for samples with and without ablation. The test conditions were as similar as possible to the conditions in the AORA turbine. The results of the study provide an insight into tensile properties, fatigue properties and FOD. The results indicated a reduction in fatigue life for the samples with ablation damage, where crack nucleation occurred either at the edge or inside the ablation region and multisite cracking was observed under far field stresses that were the same than for pristine samples, which showed single cracks. Fracture surfaces indicate intergranular fracture, with the presence of secondary cracks and a lack of typical fatigue features, e.g., beach marks which was attributed to environmental effects and creep.
ContributorsShenoy, Sneha (Author) / Peralta, Pedro (Thesis advisor) / Solanki, Kiran (Committee member) / Sieradzki, Karl (Committee member) / Arizona State University (Publisher)
Created2017
Description
Military personnel are affected by muscle fatigue during the various missions and training regimens for their work. Muscle fatigue is caused by the overuse and lack of nutrients to muscles. When a soldier is fatigued, they are unable to perform at their maximum potential and are also more susceptible to injury. For military personnel to save time and money as well as become more efficient within the missions they deploy soldiers, muscle fatigue should be predicted. Predicting fatigue will allow for a reduced rate of negative exercise-related impacts. This means that soldiers will be able to avoid potential life threatening situations they encounter due to the muscle fatigue. The newest technology in wearable devices includes clothing that incorporates heart rate monitors, breathing rate and breathing depth sensors, and a database that converts this information into the amount of calories burned during a workout. Fatigue can be tracked and predicted in the military using wearable clothing with activity sensors, preventing further injury to the soldiers and optimizing performance output at all times. For military personnel, the ability to predict fatigue using this technology would be beneficial to the soldiers and the military as a whole.
ContributorsFalk, Brady Thomas (Author) / Lockhart, Thurmon (Thesis director) / Williams, Deborah (Committee member) / Harrington Bioengineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
In real world applications, materials undergo a simultaneous combination of tension, compression, and torsion as a result of high velocity impact. The split Hopkinson pressure bar (SHPB) is an effective tool for analyzing stress-strain response of materials at high strain rates but currently little can be done to produce a synchronized combination of these varying impacts. This research focuses on fabricating a flange which will be mounted on the incident bar of a SHPB and struck perpendicularly by a pneumatically driven striker thus allowing for torsion without interfering with the simultaneous compression or tension. Analytical calculations are done to determine size specifications of the flange to protect against yielding or failure. Based on these results and other design considerations, the flange and a complementary incident bar are created. Timing can then be established such that the waves impact the specimen at the same time causing simultaneous loading of a specimen. This thesis allows research at Arizona State University to individually incorporate all uniaxial deformation modes (tension, compression, and torsion) at high strain rates as well as combining either of the first two modes with torsion. Introduction of torsion will expand the testing capabilities of the SHPB at ASU and allow for more in depth analysis of the mechanical behavior of materials under impact loading. Combining torsion with tension or compression will promote analysis of a material's adherence to the Von Mises failure criterion. This greater understanding of material behavior can be implemented into models and simulations thereby improving the accuracy with which engineers can design new structures.
ContributorsVotroubek, Edward Daniel (Author) / Solanki, Kiran (Thesis director) / Oswald, Jay (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Motorcycles must be designed for safety and long operation. Front suspension systems must in turn be safe and able to operate for long service lives. Challenges to achieving safe and long service lifetimes include designing components (rims, axles, forks, etc.) to withstand various loading conditions not just once but numerous times as a matter of fatigue life. An already developed CAD model of a motorcycle suspension was taken and optimized for various loading conditions. These conditions included static loading, braking, cornering, and wheelie and front impact loads. In all cases, front impact load was the critical loading condition when FEA in SolidWorks Simulation was conducted for the components. All components were then optimized to handle the impact load by changing geometry until safety factors of 4.0 ± 0.25 were achieved. Components were then analyzed for fatigue life, with all steel and magnesium components having infinite predicted fatigue lives and all aluminum components having fatigue lives predicted with corrected S-N curves created for up to 500 million loading cycles. The design was optimized with all components becoming improved for stress compliance, with room for improvement existing in both defining loads for analysis and developing more accurate and rigorous fatigue life models.
ContributorsOrth, Trentten (Author) / Nam, Changho (Thesis director) / Chen, Yan (Committee member) / Barrett, The Honors College (Contributor) / Engineering Programs (Contributor)
Created2023-05
Description
A unique geometry is presented that creates biaxial stresses and strains when subjected to uniaxial loading in order to facilitate further multiaxial fatigue research by reducing the need for the use of specialized multiaxial loading equipment. Cyclic plasticity is a critical process in fatigue and the geometry was successfully designed and fabricated to allow for the continuous monitoring of cyclic plastic strains of magnitude 10^(-4) mm/mm during cyclic loading. Simulation results show that plasticity occurs in a region central to the test specimen while also being subjected to biaxial stresses and strains characterized by average principal direction ratios of 1.18 and 1.39 respectively. Simulation shows fatigue life of the specimen to be 79 thousand cycles, which allows for a reasonable evolution of cyclic plasticity before reaching failure. Issues with the instrumentation process hindered experimental validation of the simulation results.
ContributorsHill, Alex (Author) / Peralta, Pedro (Thesis director) / Rajagopalan, Jagannathan (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2022-05
Description
Estimates indicate that in the United States 1 in 8 women will develop breast cancer in their lifetime. Improved cancer screenings, early detection, and targeted treatments have increased breast cancer survival rates. However, breast cancer patients treated with chemotherapy are at an increased risk for cardiovascular disease, functional impairments, and loss of cardiorespiratory fitness. These negative outcomes have implications for early morbidity and mortality. The purpose of this thesis was to test the hypothesis that high-intensity exercise preconditioning (exercise commenced prior to initiating chemotherapy and continued throughout treatment cycles) preserves health-related outcomes in breast cancer patients treated with anthracycline-containing chemotherapy. Here, we present a subset of preliminary data from an ongoing trial (NCT02842658) that is focused on VO2peak and skeletal muscle outcomes from the first 10 participants that have enrolled in the trial. Breast cancer patients (N=10; 50 ± 11 y; 168 ± 4 cm; 92 ± 37 kg; 32.3 ± 12.3 kg/m2) scheduled to receive anthracycline-containing chemotherapy were randomly assigned to one of two interventions: 1) exercise preconditioning, (3 days per week of supervised exercise throughout treatment) or 2) standard of care (attention-control). Pre-testing occurred 1-2 week prior to chemotherapy. The interventions were initiated 1 week prior to chemotherapy and continued throughout anthracycline treatment. Post-testing occurred 3-7 days following the last anthracycline treatment. VO2peak (L/min) was reduced by 16% in the control group (P < 0.05), whereas VO2peak was preserved in the exercise preconditioning group. Trends for greater preservation and/or improvement in the exercise preconditioning group were also observed for lean body mass and peak heart rate. Hand grip strength was not changed in either group (P > 0.05). Both groups demonstrated an increase in ultrasound-derived echogenicity measures of the vastus lateralis (P < 0.05), indicating changes in the composition of the skeletal muscle during treatment. These preliminary data highlight that exercise preconditioning may serve as a strategy to preserve cardiorespiratory fitness and perhaps lean mass during anthracycline treatment of breast cancer. There remains a need for larger, definitive clinical trials to identify strategies to prevent the array of chemotherapy-induced toxicities that are observed in breast cancer patients treated with anthracyclines.
ContributorsCasey, Kathleen (Author) / Angadi, Siddhartha (Thesis director) / Gaesser, Glenn (Committee member) / Dickinson, Jared (Committee member) / College of Health Solutions (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
A key aspect of understanding the behavior of materials and structures is the analysis of how they fail. A key aspect of failure analysis is the discipline of fractography, which identifies features of interest on fracture surfaces with the goal of revealing insights on the nature of defects and microstructure, and their interactions with the environment such as loading conditions. While fractography itself is a decades-old science, two aspects drive the need for this research: (i) Fractography remains a specialized domain of materials science where human subjectivity and experience play a large role in accurate determination of fracture modes and their relationship to the loading environment. (ii) Secondly, Additive Manufacturing (AM) is increasingly being used to create critical functional parts, where our understanding of failure mechanisms and how they relate to process and post-process conditions is nascent. Given these two challenges, this thesis conducted work to train convolutional neural network (CNN) models to analyze fracture surfaces in place of human experts and applies this to Inconel 718 specimens fabricated with the Laser Powder Bed Fusion (LPBF) process, as well as to traditional sheet metal specimens of the same alloy. This work intends to expand on previous work utilizing clustering methods through comparison of models developed using both manufacturing processes to demonstrate the effectiveness of the CNN approach, as well as elucidate insights into the nature of fracture modes in additively and traditionally manufactured thin-wall Inconel 718 specimens.
ContributorsVan Handel, Nicole (Author) / Bhate, Dhruv (Thesis director, Committee member) / Guo, Shenghan (Thesis director, Committee member) / Barrett, The Honors College (Contributor) / Engineering Programs (Contributor) / Dean, W.P. Carey School of Business (Contributor) / School of Mathematical and Statistical Sciences (Contributor)
Created2022-05