Engineering Commons^™

Achievements And Developments Of Hysteresis And Creep Of Pneumatic Artificial Muscles, Shenglong Xie, Haitao Liu, Jiangping Mei

Journal of System Simulation

Abstract: Regarding to the problems of hysteresis and creep, the developments and achievements of the research on pneumatic artificial muscles at home and abroad are systemically reviewed. The state of the art is summarized in terms of characteristics, reasons causing, modeling and control strategies based on the hysteresis and creep modeling. The problems in recent research are analyzed and the direction for further research is put forward. The theoretical study on hysteresis and creep of pneumatic artificial muscle is limited. The hysteresis modeling needs to consider the time-varied parameters caused by creep. Neural network modeling needs to solve …

Molecular Dynamics Study Of Creep Deformation In Nickel-Based Superalloy, Sabila Kader Pinky

MSU Graduate Theses

The present study employs molecular dynamics simulations of Ni-based superalloy to investigate the creep behavior under uniaxial compression test. Dislocation dynamics is analyzed for the nickel-based single crystal superalloy with the presence of void and with varying the distribution of gamma-prime phase The results show that multiple-void systems are more prone to yield than single-void systems and single-void systems are more prone to yield than the system without void. From the simulations, it has been determined that the creep mechanism in Ni/Ni3Al is subject to change on the applied stress depending on the distribution of gamma-prime phases change. Dislocation behavior …

Fundamental Mechanism Of Time Dependent Failure In Shale, Neel Gupta

Graduate Theses, Dissertations, and Problem Reports

In underground coal mines, mining activity disturbs the natural equilibrium state of in-situ stresses. The induced and in-situ stresses deform the rockmass surrounding the mine openings. Primary roof supports impede the deformation of the rockmass overlying the entries. However, failure can occur in the bolted rockmass, causing fatalities and injuries. The rockmass failure is erratic, and its occurrence often varies from a few days to months and years after the opening of the entry. One of the often-neglected factors in this process is the effect of time on the stability of mine openings, which can often be observed in the …

Reliability Of Lead-Free Solder Joints Under Combined Shear And Compressive Loads, Ian Bernander, Travis Dale, Yuvraj Singh, Ganesh Subbarayan

The Summer Undergraduate Research Fellowship (SURF) Symposium

In electronic assemblies, solder joints are used to create electrical connections, remove heat, and mechanically support the components. When an electronic device is powered on, the solder joints and the board they are attached to heat up, expanding at different rates. Due to the difference in expansion, shear stress is imposed on the solder joints. As the device is powered on and off, this shear stress can eventually fracture the solder joint, causing the device to fail. Therefore, to increase the lifespan of electronics, it is important to investigate the mechanical properties of solder alloys. The present study investigates how …

Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 1100°C In Air And In Silicic Acid-Saturated Steam, Logan M. Gumucio

Theses and Dissertations

Innovations in SiC based ceramic matrix composites (CMCs) have yielded exceptional high-temperature properties and performance in aggressive oxidizing environments. These material characteristics provide potential avenues for future advancements in many applications where current metallic alloys perform near their operating temperature limits in a harsh environment. As steam (typically present in these environments) enters through cracks in the matrix of a SiC/SiC composite, it leaches Si and becomes saturated with silicic acid, Si(OH)₄, prior to attacking the reinforcing SiC fibers. Therefore, it is paramount that a thorough understanding of the performance and durability of SiC fibers be obtained under …

Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 1000°C In Air And In Silicic Acid-Saturated Steam, Brian G. Kroeger

Theses and Dissertations

Advanced SiC/SiC ceramic matrix composites (CMCs) are being considered for a variety of applications. Of interest is their ability to withstand exposure to high temperature in an aggressive oxidizing environment. The presence of steam creates such an environment. As steam traverses across a SiC/SiC composite and through cracks in the SiC matrix, it becomes saturated with silicic acid, Si(OH)₄. It is essential to understand the long-term impacts and durability of SiC/SiC CMCs that have been exposed to such a demanding environment. The present research investigated creep of Hi-Nicalon™ S SiC fibers at 1000°C in air and in silicic …

Design And Testing Of A Linear Compliant Mechanism With Adjustable Force Output, William Niemeier

USF Tampa Graduate Theses and Dissertations

This thesis presents a novel compliant mechanism with adjustable force output. The force comes from the bending of a rectangular cross section beam within the mechanism. By rotating this beam with a stepper motor, the force output of the mechanism changes. A model was made to simulate this mechanism, and a prototype was made based off of this data. A test apparatus was constructed around this mechanism, and a series of tests were performed. These tests adjusted parameters such as beam rotation speed and weight in order to characterize the system. Adjustments were made based on this information and the …

High Temperature Compression Creep Of U3si2, Emil Angelo Cahanap Mercado

Theses and Dissertations

As a result of the Fukushima Daiichi Nuclear Disaster in 2011, a push for increasing the safety of nuclear power plants was made through research grants funded through the United States Department of Energy via the Accident Tolerant Fuels (ATF) campaign. One of the focuses of the campaign is improving the accident tolerance of nuclear fuel during a loss of coolant accident.

A promising set of being researched from the ATF is Silicon Carbide (SiC) composite cladding and Uranium Silicide (U3Si2) fuel pellets. Under high temperatures, stresses, and times the creep deformation can play an important factor in pellet to …

Constitutive Modeling Of Creep In Leaded And Lead-Free Solder Alloys Using Constant Strain Rate Tensile Testing, Eric Thomas Stang

Browse all Theses and Dissertations

Environmental and safety concerns have necessitated a phase-out of lead-based alloys, which are often used in electronics solder applications. In order to properly assess suitable replacement materials, it is necessary to understand the deformation mechanisms relevant to the application. In the case of electronics solder, creep is an important mechanism that must be considered in the design of reliable devices and systems. In this study, Power-Law and Garofalo constitutive creep models were derived for two medium temperature solder alloys. The first alloy is known by the commercial name Indalloy 236 and is a quaternary alloy of lead, antimony, tin, and …

Sic Fibers And Sic/Sic Ceramic Matrix Minicomposites Damage Behavior, Amjad Almansour

Advanced Ceramic Matrix Composites: Science and Technology of Materials, Design, Applications, Performance and Integration

Silicon Carbide based Ceramic Matrix Composites (CMCs) are attractive materials for use in high-temperature applications in the aerospace industry. The performance and durability of a CMC depends on the properties of its constituents. Therefore, the limitations and damage mechanisms of CMC matrix and fiber reinforcement are discussed and characterized in representative simulated application conditions, and the dominant damage mechanisms at elevated temperatures are identified. The tensile creep behavior of single Hi-Nicalon^TM Type S and Sylramic^TM SiC fibers was characterized via testing and creep parameters were extracted. Fiber creep tests were performed in air or vacuum at 1200-1482°C under …

Effect Of Formation Hydrodynamics On Mechanical Properties Of Container Materials, Barry Hojjatie Dr, D. W. Coffin, C. K. Aidun

Georgia Journal of Science

The objectives of this study were to compare the mechanical and physical properties of the sheets made using the Vortigen technology (a non-conventional technique that creates very high number vortices in a fluid flow mixture of water, fibers, and chemical additives) with those produced from a conventional method of papermaking and to provide insight into the impact of formation hydrodynamics on sheet properties. The results of formation, ultrasonic stiffness, and creep/accelerated creep measurements of the Vortigen sheets as compared with the standard sheets are presented. Samples of Vortigen (V) and standard (S) sheets (4 samples from each group) were obtained …

Experimental And Computational Investigation Of High Entropy Alloys For Elevated-Temperature Applications, Haoyan Diao

Doctoral Dissertations

To create and design novel structural materials with enhanced creep-resistance, fundamental studies have been conducted on high-entropy alloys (HEAs), using (1) thermodynamic calculations, (2) mechanical tests, (3) neutron diffraction, (4) characterization techniques, and (5) crystal-plasticity finite-element modeling (CPFEM), to explore future candidates for next-generation power plants.

All the constituent binary and ternary systems of the Al-Cr-Cu-Fe-Mn-Ni and Al-Co-Cr- Fe-Ni systems were thermodynamically modeled within the whole composition range. Comparisons between the calculated phase diagrams and literature data are in good agreement. The Al_xCrCuFeMnNi HEAs have disordered [face-centered-cubic (FCC) + body-centered-cubic (BCC)] crystal structures. Excessive alloying of the Al …

Flexural Creep Behavior Of Adhesively Bonded Metal And Composite Laminates, Hasan M. Nuwayer

Wayne State University Dissertations

Adhesively bonded structures exhibit time dependent behavior when subjected to constant load (creep). In this investigation, long-term creep behavior of adhesively bonded aluminum and carbon fiber composite beams under flexural loading was investigated. Three point bending test was selected because of its simplicity and the fact that bending stresses are quite common. In this study, two types of adhesively bonded beam specimens were tested: specimens prepared by adhesively bonding two aluminum beams and specimens prepared by adhesively bonding two unidirectional carbon fiber laminated beams. Accelerated creep tests were performed at higher temperatures up to 60 °C and deflection was measured …

Microstructure Control And Correlation To Creep Properties In Grade 91 Steel Weldment After Thermo-Mechanical Treatments And An Fe-30cr-3al Alloy Strengthened By Fe2nb Laves Phase, Benjamin Allen Shassere

Doctoral Dissertations

Type IV cracking in weldments of steel pipes after creep deformation is a concern in modern fossil-fueled power plants. Two possible methods for minimizing or eliminating Type IV cracking will be discussed. The first method alters the initial microstructure of typical Grade 91 steel base metal before welding, while the second provides baseline microstructure characteristics and creep performance of a new alloy that is strengthened by the intermetallic Fe2Nb Laves phase. The initial microstructure of the Grade 91 steel can be controlled by Thermo-Mechanical Treatments, which aids in precipitation of fine (5-10 nm) MX particles in austenite before transformation to …

Temperature Dependent Mechanical Behavior Of Solid Acids, Ryan Scott Ginder

Doctoral Dissertations

Existing literature data on the creep behavior of superprotonic solid acids, which is important for their use in fuel cell applications, is scant and unreliable. Steady state creep behavior for the model material system cesium hydrogen sulfate (CHS) is probed using nanoindentation and corroborated using uniaxial compression testing. To facilitate nanoindentation creep result interpretation, a radial flow model of power law indentation creep is developed. This model is compared with the related model from Bower, et. al. for several pre-existing literature datasets showing that the nonlinear, steady state creep law underpinning both appears valid for power law indentation creep.

Bi-Directional Fatigue Life Behavior Of Bovine Meniscus, Jaremy Creechley

Boise State University Theses and Dissertations

Meniscal injuries due to tissue tearing are prevalent in the U.S. yet the failure behavior of the meniscus is poorly understood. Clinical studies indicate that fatigue failure causes many of these tears. The highly circumferentially aligned fibers result in transversely isotropic material properties. Tears preferentially align bi-directionally to the fiber orientation. The aim of this study is to present the bi-directional fatigue life behavior of meniscal fibrocartilage. A novel fatigue life approach was developed to achieve this aim. Forty-eight bovine specimens were subjected to cyclic sinusoidal tension-tension stress at 2 Hz until rupture. Normalized peak tensile stresses were determined at …

An Examination Of The Indentation Size Effect In Fcc Metals And Alloys From A Kinetics Based Perspective Using Nanoindentation, David Earl Stegall

Mechanical & Aerospace Engineering Theses & Dissertations

The indentation size effect (ISE) in metals is described as the rise in hardness with decreasing depth of indentation and contradicts conventional plasticity behavior. The goal of this dissertation is to further examine the fundamental dislocation mechanisms that may be contributing to the so-called indentation size effect. In this work, we examined several metals and alloys including 99.999% Aluminum (SFE ~200 mJ/m²), 99.95% Nickel (SFE ~125 mJ/m²), 99.95% Silver (SFE ~22 mJ/m²⁾, and three alloys, alpha brass 70/30 (SFE >10 mJ/m²), 70/30 nickel copper (SFE ~100 mJ/ …

Γ/Γ' Co-Base Superalloys – New High Temperature Materials Beyond Ni-Base Superalloys?, Steffen Neumeier, Christopher H. Zenk, Lisa P. Freund, Mathias Göken

Beyond Nickel-Based Superalloys II

In 2006 a new L1₂ phase, Co₃(Al,W), was discovered in the Co-Al-W system which has led to the development of novel Co-base superalloys with g/g¢ microstructures similar to those of the well-established Ni-base superalloys. First investigations on simple ternary alloys could show that these Co-Al-W based alloys exhibit higher solidus temperatures and show less segregations after casting compared to typical Ni-base superalloys. This leads to the question whether this g/g¢ Co-base superalloys can be regarded as new class of high temperature materials that can compete with or even supersede established Ni-base superalloys.

In the first part of …

Effect Of Cured Time On Creep Of Lightweight Aggregate Concrete, Hongzhi Cui, Haibin Yang, Xiaoxiao Xu, Zitao Lin, Tommy Yiu Lo

International Conference on Durability of Concrete Structures

Creep and shrinkage are such properties that will occur in concrete when they are under load and exposed to surrounding. Since this property will cause deformation which may decrease the design strength of the concrete, it is necessary to do have more knowledge on this phenomenon. So, we will study the effect of creep on 7 and 14 days of cured time of specimens which sealed or unsealed will be considered, respectively. The specimens have shown how the concrete strains when they are under sustained load with time. Besides, the sealed specimens have shown how the basic creep is different …

Ceramics Sintering And Shaping Using The Electrical Field Assisted Sintering Method, Amiya Mukherjee, Troy Holland

Electric Field Assisted Sintering and Related Phenomena Far From Equilibrium

Ceramic powders are often produced by sol-gel method or by pyrolysis of some form of precursors. This presentation will emphasize the consolidation of such powders using the Electrical Field Assisted Sintering (EFAS) method. The role played by the external electrical field and/or the heating rate will be specifically investigated. This observation will be supported by in-situ sintering studies inside a TEM in the presence of a biased electrical voltage.

One can take advantage of the EFAS process to produce functionally graded material by using asymmetric die design. Similarly, one can consolidate, as well as form to shape, ceramic components in-situ …

Modeling Long-Term Deformations Of Unbound Pavement Materials Using The Miniaturized Pressuremeter Creep Data, A. M. Shaban, P. J. Consentino

Mechanical and Civil Engineering Faculty Publications

This research was undertaken to study the predictive capability of the pressuremeter test for characterizing in situ creep behavior of unbound pavement layers. Although the creep potential of granular pavement materials is less pronounced than fine-grained soils, consideration of actual creep deformations in the pavement evaluation process will improve long-term pavement performance. In this investigation, the long-term deformations determined from laboratory one-dimensional creep tests were compared with those investigated by field pressuremeter tests. The pressuremeter test consisted of inflating a cylindrical probe incrementally up to a given stress level, and then maintaining the pressure constant for a 5-min single stage. …

Biaxial Creep Test Study On The Influence Of Structural Anisotropy On Rheological Behaviour Of Hard Rock, Chuangzhou Wu, Qingsheng Chen, Sudip Basack, Riqing Xu, Zhenming Shi

Faculty of Engineering and Information Sciences - Papers: Part A

Rheological characteristics are one of most important properties needed to be considered for the designing and construction for the long term stability and serviceability of underground structures in the rock mass. Up to date, although extensive studies on the rheological properties of rocks are available in the literature, most of existing studies reported the strain-time data for the axial deformation through compression rheological method and did not mention the lateral deformation, and mainly focused on the soft rocks at shallow depth. Thus, very limited attention has been paid to the rheological properties of deep and hard rock, neglecting the effects …

A Compilation Of Research On Self-Consolidating Concrete For Prestressed Bridge Girders, Eduardo S. Torres

Electronic Theses and Dissertations

Self-Consolidating Concrete (SCC) is a relative new concrete technology developed in the 1980s in Japan. Since, SCC has been used for several applications around the world. Initially, SCC was used for on-site applications where it was difficult to place concrete. SCC workability benefits facilitated construction procedures by freely flowing, filling space and passing through dense reinforcement without vibration mechanism. Meanwhile, SCC has also been used in other applications such as the precast industry, where the benefits of the workability SCC delivers can be utilized to improve fabrication of prestressed girders. SCC has been used in the precast industry with a …

Locally Optimized Covariance Kriging For Non-Stationary System Responses, Daniel Lee Clark Jr.

Browse all Theses and Dissertations

In this thesis, the Locally-Optimized Covariance (LOC) Kriging method is developed. This method represents a flexible surrogate modeling approach for approximating a non-stationary Kriging covariance structures for deterministic responses. The non-stationary covariance structure is approximated by aggregating multiple stationary localities. The aforementioned localities are determined to be statistically significant utilizing the Non-Stationary Identification Test. This methodology is applied to various demonstration problems including simple one and two-dimensional analytical cases, a deterministic fatigue and creep life model, and a five-dimensional fluid-structural interaction problem. The practical significance of LOC-Kriging is discussed in detail and is directly compared to stationary Kriging considering computational …

Methodology For Analysis Of Stress, Creep, And Fatigue Behavior Of Compliant Mechanisms, Joshua Allen Crews

Doctoral Dissertations

"A methodology is developed for analyzing stress within homogeneous and metallic-reinforced, fixed-free compliant segments and small-length flexural pivots. Boundary conditions related to the inclusion of metallic reinforcing components within a polymer compliant segment are investigated. The analysis method outlined herein relies on key outputs from the pseudo-rigid-body models (PRBMs). A method is presented for the redesign of compliant mechanisms to include metallic reinforcement to reduce stress while maintaining force-deflection behavior. Examples are provided in which a compliant segment is redesigned to include metallic reinforcement by using the stress equations developed from the PRBM. The effect of bonding between the polymer …

Creep And Oxidation Of Hafnium Diboride-Based Ultra High Temperature Ceramics At 1500°C, Anthony J. Degregoria

Theses and Dissertations

Ultra high temperature ceramics (UHTCs) are leading candidates for aerospace structural applications in high temperature environments, including the leading edges of hypersonic aircraft and thermal protection systems for atmospheric re-entry vehicles. Before UHTCs can be used in such applications, their structural integrity and environmental durability must be assured, which requires a thorough understanding and characterization of their creep and oxidation behavior at relevant service temperatures.

Use Of Fiber Reinforced Polymer Composite Cable For Post-Tensioning Application, Xiong Yang

FIU Electronic Theses and Dissertations

Corrosion of steel tendons is a major problem for post-tensioned concrete, especially because corrosion of the steel strands is often hard to detect inside grouted ducts. Non-metallic tendons can serve as an alternative material to steel for post-tensioning applications. Carbon fiber reinforced polymer (CFRP), given its higher strength and elastic modulus, as well as excellent durability and fatigue strength, is the most practical option for post-tensioning applications.

The primary objective of this research project was to assess the feasibility of the use of innovative carbon fiber reinforced polymer (CFRP) tendons and to develop guidelines for CFRP in post-tensioned bridge applications, …

Creep Of Sylramic-Ibn Fiber Tows At Elevated Temperature In Air And In Silicic Acid-Saturated Steam, Kevin B. Sprinkle

Theses and Dissertations

Stressed oxidation experiments on Sylramic-iBN fiber tows were performed to evaluate the novel fiber's mechanical performance, creep behavior, and creep mechanisms. This research effort investigated creep response of Sylramic-iBN fiber tows at elevated temperatures in both air and in silicic acid-saturated steam environments. Creep experiments were conducted at creep stresses ranging from 127 to 762 MPa at 400°C and 500°C in order to examine the mechanical behavior of the Sylramic-iBN fiber tows at temperatures below and above the melting point of boria (450°C). Sylramic-iBN fibers are known to have excellent creep resistance, better than most other non-oxide fibers and significantly …

Microstructures And Mechanical Behavior Of Nial-Strengthened Ferritic Alloys At Room And Elevated Temperatures, Zhiqian Sun

Doctoral Dissertations

In order to improve the thermal efficiency and decrease the greenhouse gases emission, it is required to increase the steam temperature and pressure in fossil-energy power plants. In the United States, research has been performing in order to push steam temperature to 760 Celsius degree and steam pressure to 35 MPa. However, the highest operational temperature for current commercial heat-resistant ferritic steels is ~ 620 Celsius degree. In this sense, new advanced ferritic alloys with better creep resistance are needed, considering such service conditions in next-generation ultra-supercritical fossil-energy power plants.

Coherent B2-ordered NiAl-type precipitates have been employed to reinforce the …

Creep And Shrinkage Behavior Of Fly Ash Based Geopolymer Concrete, Md Rashedul Islam

Doctoral Dissertations

The manuscript presented herein is based on the investigation of the short and long term properties of fly ash based geopolymer concrete (GPC) and their link to fly ash characteristics. Fly ash (FA) exhibits a significantly different particle morphology, which impacts the mechanical properties of the resulting GPC and typically contains impurities that fluctuate from one FA source to another. A key contribution of this research work is the capturing of the variability posed by the FA stockpile with a wide range of physical, chemical, and crystallographic characteristics as a source material to select the GPC mix design. In the …