The main objective of this project is to study the characteristics of different alloys such as Steel, Aluminum and Cast Iron and to the design and analyze the stress distribution of the piston with a suitable material above the actual engine condition for a heavy duty diesel engine. In this paper, thermal analysis and mechanical analysis is done. The parameters used for the analysis are operating gas pressure, temperature and material properties of the piston. In I.C. Engine, a piston is most...

Topics: Design and Analyze, Analysis of Piston & Stress Distribution

An ideal engine mount should be able to completely isolate the engine vibration which is caused due to the engine Noise, Vibration and Harshness characteristics. Vibration in an automobile is due to different parts of the automobile, one of the main sources of vibration is the engine. In engine, the vibration is mainly due to drive trains. Hence, it is very important to optimize the engine mount to reduce vibration at the source itself, to increase the comfort of the passenger. In this paper,...

Topics: Passive Engine Rubber Mount, Finite Element Method, Elastic Characteristics, FEA Modeling,...

An ideal engine mount should be able to completely isolate the engine vibration which is caused due to the engine Noise, Vibration and Harshness characteristics. Vibration in an automobile is due to different parts of the automobile, one of the main sources of vibration is the engine. In engine, the vibration is mainly due to drive trains. Hence, it is very important to optimize the engine mount to reduce vibration at the source itself, to increase the comfort of the passenger. In this paper,...

Topics: Passive Engine Rubber Mount, Finite Element Method, Elastic Characteristics, FEA Modeling,...

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Furnaces are most commonly used for melting of materials. Induction furnaces are more beneficial as no fuel is required. It is a problem to find life cycle of Induction Melting Furnace Wall under load variation. The induction melting furnace wall is made of alumina ramming mass which is one kind of refractory material. The failure occurs due to cyclic thermal stresses due to heating and cooling cycles. Temperature distribution and thermal stress distribution fields of the induction melting...

Topics: Advanced stress life analysis, Temperature distribution, Stress distribution, explicit finite...

Furnaces are useful for melting different materials for casting process. In this research paper, we had done advanced heat transfer analysis of induction furnace wall made of silica ramming mass using explicit finite difference method. We have divided actual geometry of furnace refractory wall into 14 elements and 24 nodes. We have derived explicit finite difference equations for all 24 nodes. We have calculated temperature distribution and thermal stress distribution for all different nodes...

Topics: Advanced heat transfer analysis, Temperature distribution, Stress distribution, Explicit finite...

Furnaces are useful for melting different materials for casting process. In this research paper, we had done advanced heat transfer analysis of induction furnace wall made of silica ramming mass using explicit finite difference method. We have divided actual geometry of furnace refractory wall into 14 elements and 24 nodes. We have derived explicit finite difference equations for all 24 nodes. We have calculated temperature distribution and thermal stress distribution for all different nodes...

Topics: Advanced heat transfer analysis, Temperature distribution, Stress distribution, Explicit finite...

The U.S. Federal Aviation Administration (FAA) and the National Aeronautics and Space Administration (NASA) are actively involved in improving the predictive capabilities of transient finite element computational methods for application to safety issues involving unintended impacts on aircraft and aircraft engine structures. One aspect of this work involves the development of an improved deformation and failure model for metallic materials, known as the Tabulated Johnson-Cook model, or MAT224,...

Topics: NASA Technical Reports Server (NTRS), ALUMINUM, PENETRATION, THICKNESS, CYLINDRICAL BODIES, FINITE...

Dielectric insulators are used in a variety of laboratory settings when performing experiments in rock mechanics, petrology, and electromagnetic studies of rocks in the fields of geophysics,material science, and civil engineering. These components may be used to electrically isolate geological samples from the experimental equipment, to perform a mechanical compliance function between brittle samples and the loading equipment, to match ultrasonic transducers, or perform other functions. In...

Topics: NASA Technical Reports Server (NTRS), DIELECTRICS, INSULATORS, ROCK MECHANICS, ELECTRIC POTENTIAL,...

No abstract available

Topics: NASA Technical Reports Server (NTRS), THERMAL CONTROL COATINGS, DELAMINATING, PHOTOLUMINESCENCE,...

No abstract available

Topics: NASA Technical Reports Server (NTRS), MICROSTRUCTURE, CERAMIC MATRIX COMPOSITES, WOVEN COMPOSITES,...

The elastic stress intensity factor (SIF, commonly denoted as K) is the foundation of practical fracture mechanics (FM) analysis for aircraft structures. This single parameter describes the first-order effects of stress magnitude and distribution as well as the geometry of both structure/component and crack. Hence, the calculation of K is often the most significant step in fatigue analysis based on FM. This presentation will provide several reflections on the current state-of-the-art in SIF...

Topics: NASA Technical Reports Server (NTRS), CRACK PROPAGATION, FINITE ELEMENT METHOD, FRACTURE MECHANICS,...

No abstract available

Topics: NASA Technical Reports Server (NTRS), ACOUSTIC EMISSION, FAILURE ANALYSIS, EPOXY MATRIX COMPOSITES,...

Computing hardware, data-acquisition systems, communications systems, and many electronic control systems require well-controlled timing signals for proper and accurate operation. These signals are, in most cases, provided by circuits that employ crystal oscillators due to availability, cost, ease of operation, and accuracy. In some cases, the electronic systems are expected to survive and operate under harsh conditions that include exposure to extreme temperatures. These applications exist in...

Topics: NASA Technical Reports Server (NTRS), CRYSTAL OSCILLATORS, CHARACTERIZATION, FABRICATION, HIGH...

FATIG computes fatigue damage/fatigue life using the stress rms (root mean square) value, the total number of cycles, and S-N curve parameters. The damage is computed by the following methods: (a) traditional method using Miner s rule with stress cycles determined from a Rayleigh distribution up to 3*sigma; and (b) classical fatigue damage formula involving the Gamma function, which is derived from the integral version of Miner's rule. The integration is carried out over all stress amplitudes....

Topics: NASA Technical Reports Server (NTRS), DAMAGE, FATIGUE (MATERIALS), PROBABILITY THEORY, COMPUTER...

The originally designed SOFIA aircraft configuration included a system to pre-cool the telescope cavity on the ground before flight, however, due to various factors in the history of the project that system was not installed. This lack of ground pre-cooling was thus the source of the concern over whether or not the imagers would be exposed to a potentially unsafe thermostructural environment when the telescope cavity door was opened at altitude. This concern was in addition to the already...

Topics: NASA Technical Reports Server (NTRS), THERMAL SHOCK, STRUCTURAL ANALYSIS, THERMAL ANALYSIS, SOFIA...

A remaining useful life prediction methodology for electrolytic capacitors is presented. This methodology is based on the Kalman filter framework and an empirical degradation model. Electrolytic capacitors are used in several applications ranging from power supplies on critical avionics equipment to power drivers for electro-mechanical actuators. These devices are known for their comparatively low reliability and given their criticality in electronics subsystems they are a good candidate for...

Topics: NASA Technical Reports Server (NTRS), CAPACITORS, ELECTROMECHANICAL DEVICES, ACCELERATED LIFE...

The present invention is directed toward devices comprising carbon nanotubes that are capable of detecting displacement, impact, stress, and/or strain in materials, methods of making such devices, methods for sensing/detecting/monitoring displacement, impact, stress, and/or strain via carbon nanotubes, and various applications for such methods and devices. The devices and methods of the present invention all rely on mechanically-induced electronic perturbations within the carbon nanotubes to...

Topics: NASA Technical Reports Server (NTRS), CARBON NANOTUBES, DETECTION, SMART MATERIALS, STRESS...

Nano-fibers are used to reinforce polymer matrices to enhance the matrix dependent properties that are subsequently used in conventional structural composites. A quasi isotropic configuration is used in arranging like nano-fibers through the thickness to ascertain equiaxial enhanced matrix behavior. The nano-fiber volume ratios are used to obtain the enhanced matrix strength properties for 0.01,0.03, and 0.05 nano-fiber volume rates. These enhanced nano-fiber matrices are used with conventional...

Topics: NASA Technical Reports Server (NTRS), POLYMER MATRIX COMPOSITES, MECHANICAL PROPERTIES,...

A study is undertaken to determine the advantages and disadvantages associated with application of stress-free and pre-stressed modal bases in a reduced-order finite-element-based nonlinear simulation. A planar beam is chosen as an application example and its response due to combined thermal and random pressure loadings is examined. Combinations of two random pressure levels and two thermal conditions are investigated. The latter consists of an ambient temperature condition and an elevated...

Topics: NASA Technical Reports Server (NTRS), NONLINEARITY, REDUCED ORDER FILTERS, FINITE ELEMENT METHOD,...

Composite Overwrapped Pressure Vessels (COPVs) are frequently used for storing pressurized gases aboard spacecraft and aircraft when weight saving is desirable compared to all-metal versions. Failure mechanisms in fibrous COPVs and variability in lifetime can be very different from their metallic counterparts; in the former, catastrophic stress-rupture can occur with virtually no warning, whereas in latter, a leak before burst design philosophy can be implemented. Qualification and...

Topics: NASA Technical Reports Server (NTRS), PRESSURE VESSELS, KEVLAR (TRADEMARK), BURST TESTS, FAILURE,...

Tectonic patterns on Europa are influenced by tidal stress. An important well-organized component is associated with the orbital eccentricity, which produces a diurnally varying stress as Jupiter's apparent position in Europa's sky oscillates in longitude. Cycloidal lineaments seem to have formed as cracks propagated in this diurnally varying stress field. Maps of theoretical cycloid patterns capture many of the characteristics of the observed distribution on Europa. However, a few details of...

Topics: NASA Technical Reports Server (NTRS), CYCLOIDS, EUROPA, OBLIQUENESS, TECTONICS, MATHEMATICAL...

Ceramic thermal and environmental barrier coatings (TEBCs) will play an increasingly important role in gas turbine engines because of their ability to further raise engine temperatures. However, the issue of coating durability is of major concern under high-heat-flux conditions. In particular, the accelerated coating delamination crack growth under the engine high heat-flux conditions is not well understood. In this paper, a laser heat flux technique is used to investigate the coating...

Topics: NASA Technical Reports Server (NTRS), THERMAL CONTROL COATINGS, CERAMIC COATINGS, FAILURE ANALYSIS,...

A simple analysis method has been developed for predicting the residual compressive strength of impact-damaged sandwich panels. The method is tailored for honeycomb core-based sandwich specimens that exhibit an indentation growth failure mode under axial compressive loading, which is driven largely by the crushing behavior of the core material. The analysis method is in the form of a finite element model, where the impact-damaged facesheet is represented using shell elements and the core...

Topics: NASA Technical Reports Server (NTRS), FINITE ELEMENT METHOD, MATHEMATICAL MODELS, SANDWICH...

This paper outlines a method for the stress analysis of bonded composite corrugated panel facesheet to flange joints. The method relies on the existing HyperSizer Joints software, which analyzes the bonded joint, along with a beam analogy model that provides the necessary boundary loading conditions to the joint analysis. The method is capable of predicting the full multiaxial stress and strain fields within the flange to facesheet joint and thus can determine ply-level margins and evaluate...

Topics: NASA Technical Reports Server (NTRS), BONDED JOINTS, STRESS ANALYSIS, LAMINATES, COMPOSITE...

A study was conducted to determine the processes which govern hold time crack growth behavior in the LSHR disk P/M superalloy. Nineteen different heat treatments of this alloy were evaluated by systematically controlling the cooling rate from the supersolvus solutioning step and applying various single and double step aging treatments. The resulting hold time crack growth rates varied by more than two orders of magnitude. It was shown that the associated stress relaxation behavior for these...

Topics: NASA Technical Reports Server (NTRS), TIME DEPENDENCE, FATIGUE (MATERIALS), CRACKS, HEAT RESISTANT...

Anticipating the implementation of advanced SiC/SiC composites into turbine section components of future aero-propulsion engines, the primary objective of this on-going study is to develop physics-based analytical and finite-element modeling tools to predict the effects of constituent creep on SiC/SiC component service life. A second objective is to understand how to possibly manipulate constituent materials and processes in order to minimize these effects. Focusing on SiC/SiC components...

Topics: NASA Technical Reports Server (NTRS), COMPOSITE MATERIALS, SILICON CARBIDES, CREEP PROPERTIES,...

The pad stay and rollout components of the Ares I-X life cycle can generate cyclic stress oscillations to the vehicle that could initiate and grow fatigue cracks from weld defects. The Ares I-X Project requested that a study be performed to determine if stabilization of the vehicle is required to reduce the stresses that could initiate and grow fatigue cracks at the flange-to-skin weld of the Command Module (CM) and Service Module (SM) interface. A fatigue crack growth analysis was conducted...

Topics: NASA Technical Reports Server (NTRS), ARES 1 LAUNCH VEHICLE, STRUCTURAL STABILITY, FATIGUE...

A friction stir weld (FSW) repair method has been developed and successfully implemented on Al 2195 plate material for the Space Shuttle External Fuel Tank (ET). The method includes restarting the friction stir weld in the termination hole of the original weld followed by two reweld passes. Room temperature and cryogenic temperature mechanical properties exceeded minimum FSW design strength and compared well with the development data. Simulated service test results also compared closely to...

Topics: NASA Technical Reports Server (NTRS), FRICTION STIR WELDING, EXTERNAL TANKS, FUSION WELDING, STRESS...

Anticipating the implementation of advanced SiC/SiC ceramic composites into the hot section components of future gas turbine engines, the primary objective of this on-going study is to develop physics-based analytical and finite-element modeling tools to predict the effects of constituent creep on SiC/SiC component service life. A second objective is to understand how to possibly select and manipulate constituent materials, processes, and geometries in order to minimize these effects. In...

Topics: NASA Technical Reports Server (NTRS), CREEP PROPERTIES, CERAMIC MATRIX COMPOSITES, TIME DEPENDENCE,...

The simplified shear solution method is presented for approximating the through-thickness shear stress distribution within a composite laminate or panel based on laminated beam theory. The method does not consider the solution of a particular boundary value problem; rather it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply level stresses can be efficiently determined from...

Topics: NASA Technical Reports Server (NTRS), COMPOSITE STRUCTURES, PANELS, SHEAR STRESS, STRUCTURAL...

A modal basis selection technique for a reduced-order nonlinear numerical simulation with application to two-dimensional structures is presented as a two-step procedure. A system identification analysis is first performed using proper orthogonal decomposition. Using these results, a set of load-invariant bases consisting of the normal modes is next selected. Two criteria for making the basis selection are offered; one using the modal assurance criterion and the other using the modal expansion...

Topics: NASA Technical Reports Server (NTRS), NONLINEARITY, SIMULATION, MODAL RESPONSE, MATHEMATICAL...

The half-cycle crack growth theory was incorporated into the Ko closed-form aging theory to improve accuracy in the predictions of operational flight life of failure-critical aerostructural components. A new crack growth computer program was written for reading the maximum and minimum loads of each half-cycle from the random loading spectra for crack growth calculations and generation of in-flight crack growth curves. The unified theories were then applied to calculate the number of flights...

Topics: NASA Technical Reports Server (NTRS), CRACK PROPAGATION, AIRCRAFT STRUCTURES, B-52 AIRCRAFT, LIFE...

A method of depositing a ceramic film, particularly a silicon carbide film, on a substrate is disclosed in which the residual stress, residual stress gradient, and resistivity are controlled. Also disclosed are substrates having a deposited film with these controlled properties and devices, particularly MEMS and NEMS devices, having substrates with films having these properties.

Topics: NASA Technical Reports Server (NTRS), CERAMICS, MICROELECTROMECHANICAL SYSTEMS, ELECTRICAL...

The President's Vision for Space Exploration calls for the return of human exploration of the Moon. The plans are ambitious and call for the creation of a lunar outpost. Lunar Landers will therefore be required to land near predeployed hardware, and the dust storm created by the Lunar Lander's plume impingement to the lunar surface presents a hazard. Knowledge of the number density, size distribution, and velocity of the grains in the dust cloud entrained into the flow is needing to develop...

Topics: NASA Technical Reports Server (NTRS), DUST STORMS, LUNAR MODULE, MONTE CARLO METHOD, PLUMES,...

A process for aerospace structural concept analysis and design is presented, with examples of a blended-wing-body fuselage, a multi-bubble fuselage concept, a notional crew exploration vehicle, and a high altitude long endurance aircraft. Aerospace vehicle structures must withstand all anticipated mission loads, yet must be designed to have optimal structural weight with the required safety margins. For a viable systems study of advanced concepts, these conflicting requirements must be imposed...

Topics: NASA Technical Reports Server (NTRS), AEROSPACE VEHICLES, STRUCTURAL ANALYSIS, COMPUTATIONAL FLUID...

The simplified shear solution method is presented for approximating the through-thickness shear stress distribution within a composite laminate based on laminated beam theory. The method does not consider the solution of a particular boundary value problem, rather it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply level stresses can be efficiently determined from global load...

Topics: NASA Technical Reports Server (NTRS), LAMINATES, SHEAR STRESS, STRESS DISTRIBUTION, STRUCTURAL...

A special-purpose, semi-analytical solution method for determining the stress and deformation fields in a thin laminated-composite cylindrical shell with an elliptical cutout is presented. The analysis includes the effects of cutout size, shape, and orientation; non-uniform wall thickness; oval-cross-section eccentricity; and loading conditions. The loading conditions include uniform tension, uniform torsion, and pure bending. The analysis approach is based on the principle of stationary...

Topics: NASA Technical Reports Server (NTRS), COMPOSITE STRUCTURES, CYLINDRICAL SHELLS, DEFORMATION, DESIGN...

A semi-analytical method for determining the strain energy release rate due to a prescribed interface crack in an adhesively-bonded, single-lap composite joint subjected to axial tension is presented. The field equations in terms of displacements within the joint are formulated by using first-order shear deformable, laminated plate theory together with kinematic relations and force equilibrium conditions. The stress distributions for the adherends and adhesive are determined after the...

Topics: NASA Technical Reports Server (NTRS), ADHESIVE BONDING, ADHESIVES, MATHEMATICAL MODELS, CRACK...

High-cycle fatigue endurance of three candidate materials for the acoustic liners of the Enabling Propulsion Materials Nozzle Program was investigated. The ceramic matrix composite materials investigated were N720/AS (Nextel 720, 3M Corporation), Sylramic S200 (Dow Corning), and UT 22. High-cycle fatigue tests were conducted in air at 910 C on as-machined specimens and on specimens subjected to tensile cyclic load excursions every 160 hr followed by thermal exposure at 910 C in a furnace up to...

Topics: NASA Technical Reports Server (NTRS), CERAMIC MATRIX COMPOSITES, FATIGUE TESTS, HIGH TEMPERATURE,...

A segmented involute-foil regenerator has been designed, microfabricated and tested in an oscillating-flow rig with excellent results. During the Phase I effort, several approximations of parallel-plate regenerator geometry were chosen as potential candidates for a new microfabrication concept. Potential manufacturers and processes were surveyed. The selected concept consisted of stacked segmented-involute-foil disks (or annular portions of disks), originally to be microfabricated from...

Topics: NASA Technical Reports Server (NTRS), FABRICATION, METAL FOILS, REGENERATORS, STIRLING ENGINES,...

The influence of delamination on the progressing damage path and initial failure load in composite laminates is investigated. Results are presented from a numerical and an experimental study of center-notched tensile-loaded coupons. The numerical study includes two approaches. The first approach considers only intralaminar (fiber breakage and matrix cracking) damage modes in calculating the progression of the damage path. In the second approach, the model is extended to consider the effect of...

Topics: NASA Technical Reports Server (NTRS), DELAMINATING, FAILURE ANALYSIS, LAMINATES, LOADS (FORCES),...

A traction-displacement relationship that may be embedded into a cohesive zone model for microscale problems of intergranular fracture is extracted from atomistic molecular-dynamics simulations. A molecular-dynamics model for crack propagation under steady-state conditions is developed to analyze intergranular fracture along a flat 99 [1 1 0] symmetric tilt grain boundary in aluminum. Under hydrostatic tensile load, the simulation reveals asymmetric crack propagation in the two opposite...

Topics: NASA Technical Reports Server (NTRS), MOLECULAR DYNAMICS, CONTINUUM MODELING, CRACK PROPAGATION,...

The goal of this investigation is to assess the quality of high-cycle-fatigue life estimation via a reduced order method, for structures undergoing geometrically nonlinear random vibrations. Modal reduction is performed with several different suites of basis functions. After numerically solving the reduced order system equations of motion, the physical displacement time history is obtained by an inverse transformation and stresses are recovered. Stress ranges obtained through the rainflow...

Topics: NASA Technical Reports Server (NTRS), ACOUSTIC FATIGUE, FATIGUE LIFE, NONLINEARITY, LIFE...

Parametric solid and surface models of the crew exploration vehicle (CEV) command module (CM) structure concepts are developed for rapid finite element analyses, structural sizing and estimation of optimal structural mass. The effects of the structural configuration and critical design parameters on the stress distribution are visualized, examined to arrive at an efficient design. The CM structural components consisted of the outer heat shield, inner pressurized crew cabin, ring bulkhead and...

Topics: NASA Technical Reports Server (NTRS), COMMAND MODULES, MATHEMATICAL MODELS, CREW EXPLORATION...

Cryogenic vessels, such as the Space Shuttle External Tank, are often insulated with closed-cell foam because of its low thermal conductivity. The coefficient of thermal expansion mismatch between the foam and metallic substrate places the foam under a biaxial tension gradient through the foam thickness. The total foam thickness affects the slope of the stress gradient and is considered a significant contributor to the initiation of subsurface cracks. Rigid polymeric foams are brittle in nature...

Topics: NASA Technical Reports Server (NTRS), FOAMS, CRACK INITIATION, CRACK PROPAGATION, EXTERNAL TANKS,...

Bearing-load response for a pin-loaded hole is studied within the context of two-dimensional finite element analyses. Pin-loaded-hole configurations are representative of mechanically connected structures, such as a stiffener fastened to a rib of an isogrid panel, that are idealized as part of a larger structural component. Within this context, the larger structural component may be idealized as a two-dimensional shell finite element model to identify load paths and high stress regions. Finite...

Topics: NASA Technical Reports Server (NTRS), MATHEMATICAL MODELS, BEARINGS, MECHANICAL PROPERTIES, HOLES...

Fretting is a structural damage mechanism arising between two nominally clamped surfaces subjected to an oscillatory loading. A critical location for fretting induced damage has been identified at the blade/disk and blade/damper interfaces of gas turbine engine turbomachinery and space propulsion components. The high- temperature, high-frequency loading environment seen by these components lead to severe stress gradients at the edge-of-contact that could potentially foster crack growth leading...

Topics: NASA Technical Reports Server (NTRS), CRACK PROPAGATION, FRETTING, NICKEL ALLOYS, SINGLE CRYSTALS,...

Fretting is a structural damage mechanism observed when two nominally clamped surfaces are subjected to an oscillatory loading. A critical location for fretting induced damage has been identified at the blade/disk and blade/damper interfaces of gas turbine engine turbomachinery and space propulsion components. The high-temperature, high-frequency loading environment seen by these components lead to severe stress gradients at the edge-of-contact. These contact stresses drive crack nucleation and...

Topics: NASA Technical Reports Server (NTRS), HIGH TEMPERATURE, FRETTING, OSCILLATIONS, LOADS (FORCES),...

This report presents the use of a time-marching three-dimensional compressible Navier-Stokes equation numerical solver with a one-equation turbulence model to simulate the flow fields developed along concave wall surfaces without and with a downstream extension flat wall surface. The 3-D Navier- Stokes numerical solver came from the NASA Glenn-HT code. The one-equation turbulence model was derived from the Spalart and Allmaras model. The computational approach was first calibrated with the...

Topics: NASA Technical Reports Server (NTRS), NAVIER-STOKES EQUATION, TIME MARCHING, TURBULENCE MODELS,...

approach is presented for carrying out the reliability-based design of a plate-like wing that is part of a wind tunnel model. The goal is to design the wind tunnel model to match the stiffness characteristics of the wing box of a flight vehicle while satisfying strength-based risk/reliability requirements that prevents damage to the wind tunnel model and fixtures. The flight vehicle is a modified F/A-18 aircraft. The design problem is solved using reliability-based optimization techniques. The...

Topics: NASA Technical Reports Server (NTRS), DESIGN ANALYSIS, PROBABILITY THEORY, WIND TUNNEL MODELS,...