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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Investigations into the mechanical behavior of composite bolted joints

Testing procedures and data reduction and interpretation techniques were established for a program to study the mechanical behavior of bolted joints at room temperature, -157 C (-250 F), and 315 C (600 F). The load transfer characteristics, from one bolt to another, in double-bolt joints were investigated by examining data generated in previous investigations. From the results, it appears the increase in load-carrying capacity by adding a second bolt in tandem can be predicted.

Perry, J. C.↗
NASA NTRS1979

Strain measurements in composite bolted-joint specimens

Strain data from a series of bolted joint tests is presented. Double lap, double hole, double lap, single hole, and open hole tensile specimens were tested and the strain gage locations, load strain responses, and load axial displacement responses are presented. The open hole specimens were gaged to determine strain concentration factors. The double lap, double hole specimens were gaged to determine the uniformity of the strain in the joint and the amount of load transferred past the first bolt. The measurements indicated roughly half the load passed the first bolt to be reacted by the second bolt.

Hyer, M. W.↗
NASA NTRS1985

Failure mechanisms of laminates transversely loaded by bolt push-through

Stiffened composite panels proposed for fuselage and wing design utilize a variety of stiffener-to-skin attachment concepts including mechanical fasteners. The attachment concept is an important factor influencing the panel's strength and can govern its performance following local damage. Mechanical fasteners can be an effective method for preventing stiffener-skin separation. One potential failure mode for bolted panels occurs when the bolts pull through the stiffener attachment flange or skin. The resulting loss of support by the skin to the stiffener and by the stiffener to the skin can result in local buckling and subsequent panel collapse. The characteristic failure modes associated with bolt push-through failure are described and the results of a parametric study of the effects that different material systems, boundary conditions, and laminates have on the forces and displacements required to cause damage and bolt pushthrough failure are presented.

Waters, W. A., Jr.↗
NASA NTRS1994

System Measures Loads In Bolts

Improved technique for ultrasonic nondestructive measurement of loads in bolts involves use of pulsed phase-locked loop interferometer. Provides for correction of errors and for automatic readout of loads in bolts. Actual bolt load measured, using transducers rebonded after bolts tightened. Calibration block and thermometer added. Technique applicable to critical fasteners in aerospace applications, nuclear reactors, petroleum and other chemical processing plants, steel bridges, and other structures.

Allison, Sidney G.↗
NASA NTRS1995

Fatigue-Arrestor Bolts

Bolts that arrest (or, more precisely, retard) onset of fatigue cracking caused by inelastic strains developed. Specifically developed to be installed in flange holes of unrestrained rocket engine nozzle. Fanges sometimes used to bolt nozzle to test stand; however, when rocket engine operated without this restraint, region around bolt holes experience severe inelastic strains causing fatigue cracking. Interference fits introduce compressive preloads that retard fatigue by reducing ranges of strains. Principle of these fatigue-arrestor bolts also applicable to holes in plates made of other materials and/or used for different purposes.

Onstott, Joseph W.↗
NASA NTRS1999

Ultrasonic Bolt Gage

An ultrasonic bolt gage is described which uses a crosscorrelation algorithm to determine a tension applied to a fastener, such as a bolt. The cross-correlation analysis is preferably performed using a processor operating on a series of captured ultrasonic echo waveforms. The ultrasonic bolt gage is further described as using the captured ultrasonic echo waveforms to perform additional modes of analysis, such as feature recognition. Multiple tension data outputs, therefore, can be obtained from a single data acquisition for increased measurement reliability. In addition, one embodiment of the gage has been described as multi-channel, having a multiplexer for performing a tension analysis on one of a plurality of bolts.

Gleman, Stuart M.↗
NASA NTRS2010

Mechanics of Re-Torquing in Bolted Flange Connections

It has been widely accepted that the phenomenon of time-dependent loosening of flange connections is a strong consequence of the viscous nature of the compression seal material. Characterizing the coupled interaction between gasket creep and elastic bolt stiffness has been useful in predicting conditions that facilitate leakage. Prior advances on this sub-class of bolted joints has lead to the development of (1) constitutive models for elastomerics, (2) initial tightening strategies, (3) etc. The effect of re-torque, which is a major consideration for typical bolted flange seals used on the Space Shuttle fleet, has not been fully characterized, however. The current study presents a systematic approach to characterizing bolted joint behavior as the consequence of sequentially applied torques. Based on exprimenta1 and numerical results, the optimal re-torquing parameters have been identified that allow for the negligible load loss after pre-load application

Gordon, Ali P.↗
NASA NTRS2020

Aeroheating Measurements of BOLT Aerodynamic Fairings and Transition Module

The Air Force Office of Scientific Research (AFOSR) has sponsored the Boundary Layer Transition (BOLT) Experiments to investigate hypersonic boundary layer transition on a low-curvature, concave surface with swept leading edges. This paper presents aeroheating measurements on a subscale model of the BOLT Flight Geometry, aerodynamic fairings, and Transition Module (TSM) in the NASA Langley 20-Inch Mach 6 Air Tunnel. The purpose of the test was to investigate and identify any areas of localized heating on the TSM for inclusion in the BOLT Critical Design Review (CDR). Surface heating distributions were measured using global phosphor thermography, and data were obtained for a range of model attitudes and free stream Reynolds numbers. Measurements showed low heating on the fairings and TSM. Additional analysis was completed after the CDR to compare heating on the TSM for the nominal BOLT vehicle reentry angle-of-attack with heating on the TSM for possible reentry angle-of-attack excursions. The results of this analysis were used in conjunction with thermal analyses from Johns Hopkins Applied Physics Lab (JHU/APL) and the Air Force Research Laboratory (AFRL) to assess the need for thermal protection on the flight vehicle TSM.

Rieken, Elizabeth F.↗
NASA NTRSDate not supplied

A Preliminary Assessment of Step Effects on the BOLT Geometry in Mach 6 Flow

An infrared thermography measurement technique has been installed in the Langley Aerothermodynamic Laboratory. The system is calibrated for use with commercially available thermoplastics and ceramic materials, and to the surface temperature ranges when exposed to the facility hypersonic flow. Herein an uncertainty quantification is performed, revealing 5% surface temperature and 20% heat transfer uncertainty bands to two-sigma confidence. As a first application of the test measurement technique, an investigation was conducted to explore the correlation between the height of forward facing (FF) and rearward facing (RF) two-dimensional steps, free stream Reynolds number, and the onset of boundary layer transition from laminar to turbulent in Mach 6 flow on a 50% scale Boundary Layer Transition (BOLT) flight test vehicle geometry. Computational predictions were generated to identify potential x/L locations of transition onset for various flow conditions with a smooth outer mold line geometry and are compared to experimental results. The BOLT Step Test was conducted in the NASA Langley Aerothermodynamic Laboratory 20-inch Mach 6 wind tunnel at Reynolds numbers between 1.4 and 11.3 million conditions for various step heights. Data were collected using a developmental infrared thermography test technique and reduced to heat transfer for comparison with CFD solutions. This is a preliminary assessment of the developmental infrared thermography test technique used to acquire and reduce the experimental data. insight into the ongoing comparative analysis of the effects of FF and RF steps on boundary layer transition for the BOLT geometry in Mach 6 flow.

BOLT↗
NASA NTRSDate not supplied

A Preliminary Assessment of Step Effects on the BOLT Geometry in Mach 6 Flow

An infrared thermography measurement technique has been installed in the Langley Aerothermodynamic Laboratory. The system is calibrated for use with commercially available thermoplastics and ceramic materials, and to the surface temperature ranges when exposed to the facility hypersonic flow. Herein an uncertainty quantification is performed, revealing 5% surface temperature and 20% heat transfer uncertainty bands to two-sigma confidence. As a first application of the test measurement technique, an investigation was conducted to explore the correlation between the height of forward facing (FF) and rearward facing (RF) two-dimensional steps, free stream Reynolds number, and the onset of boundary layer transition from laminar to turbulent in Mach 6 flow on a 50% scale Boundary Layer Transition (BOLT) flight test vehicle geometry. Computational predictions were generated to identify potential x/L locations of transition onset for various flow conditions with a smooth outer mold line geometry and are compared to experimental results. The BOLT Step Test was conducted in the NASA Langley Aerothermodynamic Laboratory 20-inch Mach 6 wind tunnel at Reynolds numbers between 1.4 and 11.3 million conditions for various step heights. Data were collected using a developmental infrared thermography test technique and reduced to heat transfer for comparison with CFD solutions. This is a preliminary assessment of the developmental infrared thermography test technique used to acquire and reduce the experimental data. insight into the ongoing comparative analysis of the effects of FF and RF steps on boundary layer transition for the BOLT geometry in Mach 6 flow.

BOLT↗
NASA NTRS1966

Fastener provides for bolt misalignment and quick release of flange

Fastener enables two large flanges to be bolted together without close alignment between the bolt and bolt-hole diameters, and provides for a quick release of one of the flanges under emergency conditions. It contains a nut that is retained by a square head in a recess in one side of the removable flange and by a collar and snap ring on the other side of the flange.

England, C.↗
NASA NTRS1978

Torquing preload in a lubricated bolt

The tension preload obtained by torquing a 7/8 in. diam UNC high strength bolt was determined for lubricated and dry conditions. Consistent preload with a variation of + or - 3% was obtained when the bolt head area was lubricated prior to each torque application. Preload tensions nearly 70% greater than the value predicted with the commonly used formula occurred with the lubricated bolt. A reduction to 39% of the initial preload was observed during 50 torque applications without relubrication. Little evidence of wear was noted after 203 cycles of tightening.

Seegmiller, H. L.↗
NASA NTRS1979

Space Shuttle orbiter separation bolts

Evolution of the space shuttle from previous spacecraft systems dictated growth and innovative design of previously standard ordnance devices. Initially, one bolt design was programmed for both 747 and external tank application. However, during development and subsequent analyses, two distinct designs evolved. The unique requirements of both bolts include: high combined loading, redundant initiation, flush separation plane, self-righting and shank attenuation. Of particular interest are the test methods, problem areas, and use of subscale models which demonstrated feasibility at an early phase in the program. The techniques incorporated in the shuttle orbiter bolts are applicable to other mechanisms.

Ritchie, R. S.↗
NASA NTRS1979

Preliminary bolted-joint data

Bolted-joint strength and failure modes for advanced graphite/polyimide composite laminates at 116K (-250 F), room temperature, and 589K (600 F) were determined to provide preliminary design data. The bolted-joint test setup for the low and elevated temperature tests is described. Test results are reported on a quasi-isotropic laminate of Celion 6000/PMR-15. Single bolt, double lap shear specimens were tested to obtain maximum joint strength and failure mode. The effect of joint geometry and temperature on joint strength and failure mode is presented.

Wichorek, G. R.↗
NASA NTRS1980

Bolt-bearing fatigue of a graphite/epoxy laminate

Graphite/epoxy laminates were tested under bolt-bearing loads for a range of bolt clampup torques and for several test conditions involving water. High clampup torque improved both the static strength and fatigue limit by about 100 percent compared to a simple pin-bearing case, which had no through-the-thickness constraint. The static strength improvement was explained in terms of failure modes. Bolt clampup also influenced the hole elongation that developed before failure. For both the static and fatigue tests, the hole elongations were much larger for the low-torque clampup. Tests in water degraded static bearing strength only slightly, but reduced the fatigue limit about 40 percent below that for tests conducted in air.

Crews, J. H., Jr.↗
NASA NTRS1979

Development of forward and aft separation bolts for the NASA Space Shuttle solid rocket booster separation system

A program is underway to design, develop, fabricate, and qualify large high-load forward and aft separation bolts for the Space Shuttle; the bolts will serve as attachment between two solid rocket boosters and the external tank. This paper reviews bolt development, with emphasis on the scaling of components, the use of high strength maraging steel for the internal components, and the use of lead as a hydraulic fluid.

Nein, H.↗
NASA NTRS1982

Strain-Gaged Bolts Are Easily Prepared

New method for installing strain gages in structural bolts is implemented as standard workbench procedure. Rather than potting gages in a hole along axis of bolt, gages are first installed on outside of plastic carrier tube. Tube is then epoxied in axial hole. Procedure can be used to prepare gages to monitor bolt tension, shear, or torsion.

Walker, R. L.↗
NASA NTRS1982

Safety Bolt Doubles as a Bushing-Removal Tool

Bushings fitted to close tolerances and limited access can be removed without damage to housing by using bolt with integrated locking dog. Such self-retaining positive - locking bolts are normally used as fasteners in critical joints where accidentally loosened bolt could cause damage or injuries.

Haverkamp, C. E.↗