Engineering topics

Lerch, Bradley

Publications and source records attributed to Lerch, Bradley.

7 records

NASA NTRS2015

Material Characterization of Additively Manufactured Components for Rocket Propulsion

To advance Additive Manufacturing (AM) technologies for production of rocket propulsion components the NASA Glenn Research Center (GRC) is applying state of the art characterization techniques to interrogate microstructure and mechanical properties of AM materials and components at various steps in their processing. The materials being investigated for upper stage rocket engines include titanium, copper, and nickel alloys. Additive manufacturing processes include laser powder bed, electron beam powder bed, and electron beam wire fed processes. Various post build thermal treatments, including Hot Isostatic Pressure (HIP), have been studied to understand their influence on microstructure, mechanical properties, and build density. Micro-computed tomography, electron microscopy, and mechanical testing in relevant temperature environments has been performed to develop relationships between build quality, microstructure, and mechanical performance at temperature. A summary of GRCs Additive Manufacturing roles and experimental findings will be presented.

Additive Manufacturing↗

NASA NTRS2015

Materials Characterization of Additively Manufactured Components for Rocket Propulsion

To advance Additive Manufacturing (AM) technologies for production of rocket propulsion components the NASA Glenn Research Center (GRC) is applying state of the art characterization techniques to interrogate microstructure and mechanical properties of AM materials and components at various steps in their processing. The materials being investigated for upper stage rocket engines include titanium, copper, and nickel alloys. Additive manufacturing processes include laser powder bed, electron beam powder bed, and electron beam wire fed processes. Various post build thermal treatments, including Hot Isostatic Pressure (HIP), have been studied to understand their influence on microstructure, mechanical properties, and build density. Micro-computed tomography, electron microscopy, and mechanical testing in relevant temperature environments has been performed to develop relationships between build quality, microstructure, and mechanical performance at temperature. A summary of GRC's Additive Manufacturing roles and experimental findings will be presented.

Additive Manufacturing↗

NASA NTRS2010

Transparent Large Strain Thermoplastic Polyurethane Magneto-Active Nanocomposites

Smart adaptive materials are an important class of materials which can be used in space deployable structures, morphing wings, and structural air vehicle components where remote actuation can improve fuel efficiency. Adaptive materials can undergo deformation when exposed to external stimuli such as electric fields, thermal gradients, radiation (IR, UV, etc.), chemical and electrochemical actuation, and magnetic field. Large strain, controlled and repetitive actuation are important characteristics of smart adaptive materials. Polymer nanocomposites can be tailored as shape memory polymers and actuators. Magnetic actuation of polymer nanocomposites using a range of iron, iron cobalt, and iron manganese nanoparticles is presented. The iron-based nanoparticles were synthesized using the soft template (1) and Sun's (2) methods. The nanoparticles shape and size were examined using TEM. The crystalline structure and domain size were evaluated using WAXS. Surface modifications of the nanoparticles were performed to improve dispersion, and were characterized with IR and TGA. TPU nanocomposites exhibited actuation for approximately 2wt% nanoparticle loading in an applied magnetic field. Large deformation and fast recovery were observed. These nanocomposites represent a promising potential for new generation of smart materials.

Yoonessi, Mitra↗

NASA NTRS2001

Behavior of Three Metallic Alloys Under Combined Axial-Shear Stress at 650 C

Three materials, Inconel 718, Haynes 188, and 316 stainless steel, were tested under an axial-torsional stress state at 650 C. The objective of this study was to quantify the evolution of the material while in the viscoplastic domain. Initial and subsequent yield surfaces were experimentally determined to quantify hardening. Subsequent yield surfaces (yield surfaces taken after a preload) had a well-defined front side, in the prestrain direction, but a poorly defined back side, opposite the prestrain direction. Subsequent yield surfaces exhibited isotropic hardening by expansion of the yield surface, kinematic hardening by translation of the yield surface, and distortional hardening by flattening of the yield surface in the direction opposite to the last prestrain. An existing yield function capable of representing isotropic, kinematic, and distortional hardening was used to fit each yield surface. Four variables are used to describe each surface. These variables evolve as the material state changes and have been regressed to the yield surface data.

Colaiuta, Jason F.↗

NASA NTRS2000

GRCop-84 Development for Combustion Chamber Liners

The development, test, and thermophysical & mechanical properties of a GRCop-84 alloy for combustion chamber liners is discussed. Topics discussed include: History of GRCop-84 development, GRCop-84 thermal expansion, thermal conductivity of GRCop-84, yield strength of GRCop-84, GRCop-84 creep lives, GrCop-84 low cycle fatigue (LCF) lives, and hot fire testing of GRCop-84 spool pieces.

Ellis, David↗

NASA NTRS1997

Model Determined for Predicting Fatigue Lives of Metal Matrix Composites Under Mean Stresses

Aircraft engine components invariably are subjected to mean stresses over and above the cyclic loads. In monolithic materials, it has been observed that tensile mean stresses are detrimental and compressive mean stresses are beneficial to fatigue life in comparison to a base of zero mean stress. Several mean stress models exist for monolithic metals, but each differ quantitatively in the extent to which detrimental or beneficial effects are ascribed. There have been limited attempts to apply these models to metal matrix composites. At the NASA Lewis Research Center, several mean stress models--the Smith-Watson- Topper, Walker, Normalized Goodman, and Soderberg models--were examined for applicability to this class of composite materials. The Soderberg approach, which normalizes the mean stress to a 0.02-percent yield strength, was shown to best represent the effect of mean stresses over the range covered. The other models varied significantly in their predictability and often failed to predict the composite behavior at very high tensile mean stresses. This work is the first to systematically demonstrate the influence of mean stresses on metal matrix composites and model their effects. Attention also was given to fatigue-cracking mechanisms in the Ti-15-3 matrix and to micromechanics analyses of mean stress effects.

Lerch, Bradley↗

NASA NTRS1995

Bending properties of nickel electrodes for nickel-hydrogen batteries

Recent changes in manufacturing have resulted in nickel-hydrogen batteries which fail prematurely by electrical shorting. This is believed to be a result of a blistering problem in the nickel electrodes. This study investigates the bending properties of nickel electrodes in an attempt to correlate the bending properties with the propensity of the electrode to blister. Nickel electrodes from three different batches of material were tested in both the as-received and impregnated forms. Effects of specimen curvature and position within the electrode on the bending strength were studied and within-electrode and batch-to-batch variation were addressed. Two color imaging techniques were employed which allowed differentiation of phases within the electrodes. These techniques aided in distinguishing the relative amounts of nickel hydroxide surface loading on each electrode, relating surface loading to bend strength. Bend strength was found to increase with the amount of surface loading.

Lerch, Bradley↗