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Viewing 1 to 23 of 23
2006-09-12
Technical Paper
2006-01-3173
Prashanth Janardhan, Jamal Sheikh-Ahmad, Hossein Cheraghi
In the present work we studied the edge trimming process of CFRP with a diamond interlocking “burr” tool. Measurements of tool wear, surface roughness, spindle power and delamination depth were performed for different combinations of spindle speed and feed rate and were subsequently used to characterize machining quality. It was found that direct wear measurement for this type of cutting tool is not conclusive and thus not suitable for assessing tool life and machining quality. Instead, indirect indicators of tool wear were found more suitable for this purpose. Using these indirect methods an equation for tool life was defined and parameters for optimum machining quality were determined.
2008-08-19
Journal Article
2008-01-2259
K. S. Raju, B. L. Smith, F. Caido, C. Gomez, M. Shiao
The fatigue behavior of Hilok fastener joints under constant amplitude loading has been investigated experimentally. The effects of load transfer in an unbalanced joint configuration was characterized in terms of a stress severity factor relative to the open-hole configuration. The experimental data indicates that the clamp-up forces dominate the performance of fastener joints with the open-hole fatigue life being the lower bound at the stress levels investigated. The failure modes were observed to transition from a net-section type failure across the minimum section to a fretting induced failure at some distance from the hole. The experimental data has been used to develop stress severity factors to be used as a measure of the fatigue quality of the fastener joints.
2008-08-19
Journal Article
2008-01-2232
Linda K. Kliment, Richard B. Bramlette, Kamran Rokhsaz, Thomas DeFiore
Presented here are analyses and statistical summaries of data collected from 11,299 flight operations recorded on 6 BE-1900D aircraft during routine commuter service over a period of three years. Basic flight parameters such as airspeed, altitude, flight duration, etc. are shown in a form that allows easy comparison with the manufacturer's design criteria. Lateral ground loads are presented for ground operations. Primary emphasis is placed on aircraft usage and flight loads. Maneuver and gust loads are presented for different flight phases and for different altitude bands. In addition, derived gust velocities and various coincident flight events are shown and compared with published operational limits.
2006-08-30
Technical Paper
2006-01-2388
Pandya Rajen Subhashchandra, Bahr Behnam
This study presents the prediction of the dimensional variation of holes due to sheet metal bending using the hydroforming technique. Sheet metal with pre-drilled holes was evaluated for a bending operation using a hydroforming technique. Sheet metal with a variety of thicknesses, bending radii, and bending angles was evaluated. Variation in the dimensional tolerance due to the bending was attained using the minimum radial separation method. A dataset of dimensional variation in the holes was developed and used for development of the artificial neural network, which was able to predict the dimensional variation of the hole if an unknown pattern of inputs was provided.
2006-08-30
Technical Paper
2006-01-2410
Steven R. Skinner, Moreno L. Mitchell
The reliability and maintenance of electrical wiring and electrical components in aging aircraft have become areas of concern for the aviation industry. Numerous investigations have been conducted on the aging aspects of wiring and systems of large transport and military airplanes, with funding primarily from the FAA (Federal Aviation Administration), Air Force, and NASA. However, because of the large number of smaller general aviation aircraft in service, a need for examining the condition of wiring, electrical components and maintenance procedures for smaller aircraft exists. The Aging Aircraft Research Laboratory at the National Institute for Aviation Research (NIAR), Wichita State University, has conducted a comprehensive teardown evaluation of three high time commuter class airplanes. This teardown included assessment of aircraft wiring, electrical systems and circuit breakers through general and intrusive visual inspections and laboratory tests.
2006-08-30
Technical Paper
2006-01-2443
Issam K. Samarah, Gamal S. Weheba, Thomas E. Lacy
A series of carefully selected tests were used to isolate the coupled influence of various combinations of the number of facesheet plies, impact energies, and impactor diameters on the damage formation and residual strength degradation of sandwich composites due to normal impact. The diameter of the planar damage area associated with Through Transmission Ultrasonic C-scan and the compression after impact measurements were used to describe the extent of the internal damage and residual strength degradation of test panels, respectively. Standard analysis of variance techniques were used to assess the significance of the regression models, individual terms, and the model lack-of-fit. In addition, the inherent variability associated with given types of experimental measurements was evaluated.
1975-02-01
Technical Paper
750511
J. A. Alic, H. Archang
Laminated metal-metal composites can have attractive fracture toughness properties; they also offer potentially good fatigue performance. These attributes are reviewed and prospects for improvement discussed. Weak interlaminar bonds are seen to be important, while quite thin layers seem to be most promising for laminates of higher strength materials. The experimental program utilized 0.033 in (0.84 mm) thick laminae of 7075-T6 aluminum alloy, adhesively bonded. Eight-layer composites were compared with solid sheets of nearly the same total metal thickness. Both fracture toughness and fatigue properties were determined. Kc values of more than double the KIc for this alloy were observed in the laminates, while fatigue performance as indicated by comparative S-N curves was found to be slightly improved.
2017-09-19
Journal Article
2017-01-2152
Sean Taklimi, Ali Ghazinezami, Kim Cluff PhD, Davood Askari
Abstract The use of nanomaterials and nanostructures have been revolutionizing the advancements of science and technology in various engineering and medical fields. As an example, Carbon Nanotubes (CNTs) have been extensively used for the improvement of mechanical, thermal, electrical, magnetic, and deteriorative properties of traditional composite materials for applications in high-performance structures. The exceptional materials properties of CNTs (i.e., mechanical, magnetic, thermal, and electrical) have introduced them as promising candidates for reinforcement of traditional composites. Most structural configurations of CNTs provide superior material properties; however, their geometrical shapes can deliver different features and characteristics. As one of the unique geometrical configurations, helical CNTs have a great potential for improvement of mechanical, thermal, and electrical properties of polymeric resin composites.
1999-06-05
Technical Paper
1999-01-2270
B. Bahr, R. Vodrahalli
Composites are finding more and more applications in the aircraft industry. Drilling good quality holes is a major challenge for the manufacturing industry. The major factors which have an effect on hole quality are cutting parameters like speed and feedrate, machine rigidity, tool material, workpiece material, and tool geometry. The hole quality was studied by measuring the hole diameter and visually observing other parameters like shape and fiber breakout. Force analysis indicates that thrust increases with an increase in feedrate. Speed does not seem to have a very significant effect on thrust. The tool geometry plays a very important role in fiber pullout.
1999-04-20
Technical Paper
1999-01-1584
Sait Alansatan, Michael Papadakis
An experimental study was conducted to investigate ice-adhesion on clean and coated aluminum surfaces. A test apparatus using the parallel plate linear shear technique was designed along with a data acquisition system for conducting the tests and recording the experimental data. A low pulling rate was applied to specially prepared test specimens for measuring the strength of ice adhesion for a range of test conditions. The effects of surface roughness, surface contamination, and water impurity on ice adhesion were investigated. In addition, tests were conducted to evaluate the effectiveness of a low ice-adhesion coating applied to aluminum test specimens. The results obtained showed that the bond between ice and metal was considerably lower for tap water than for distilled water. For the clean and coated aluminum surfaces the strength of ice adhesion varied with specimen roughness. However, no clear trend was established between ice adhesion strength and surface roughness.
1999-04-20
Technical Paper
1999-01-1575
Bert Smith, Ala Hijazi, Roy Myose, Adil Mouak, Perry Saville
Multiple site damage (MSD) on aging aircraft accumulates from fatigue loading over a period of time. For ductile materials such as 2024-T3 aluminum, MSD may lower the strength below that which is predicted by conventional fracture mechanics. An analytical model referred to as the linkup (or plastic zone touch) model has previously been used to describe this phenomenon. However, the linkup model has been shown to produce inaccurate results for many configurations. This paper describes several modifications of the linkup model developed from empirical analyses. These modified linkup models have been shown to produce accurate results over a wide range of configurations for both unstiffened and stiffened flat 2024-T3 panels with MSD at open holes. These modified models are easy to use and give quick and accurate results over a large range of parameters.
1999-04-20
Technical Paper
1999-01-1574
Roy Y. Myose, Bert L. Smith, Waruna Seneviratne, Shaukat Khalil, Youngkeun Hwang, Chien-Chuan Lai
The residual strength of an aluminum panel with a centric hole and one cracked ligament was investigated experimentally. Each of the 7075-T6 aluminum panels which were tested included a cracked ligament of varying length on one side of the centric hole and an uncracked ligament on the other side of the hole. The failure of such a panel subjected to uniform tensile loading normally occurs according to the lower of two modes: brittle fracture or a net section type of yielding. On the other hand, the question of whether one or both ligaments fail is not easily answered. Results show that one or two ligament failure depends upon test conditions such as crack length and loading method. For short crack lengths, the uncracked ligament will fail almost simultaneously with the failure of the cracked ligament.
1999-04-20
Technical Paper
1999-01-1565
S. Hossein Cheraghi, Janet M. Twomey, K. Krishnan, B. Bahr
Aerospace manufactures purchase millions of drill bits each year for the manufacture of large aircraft structures. This paper describes an ongoing research project for the development of an automated system to detect poor quality drill bits before they are put to use.
1999-04-20
Technical Paper
1999-01-1564
B. Bahr, T. Mankad, R. Vodrahalli, J. Sha
Drilling is one of the most widely applied manufacturing operations. Millions of holes are drilled today in manufacturing industries especially in aerospace industry where high quality holes are essential. Rejection and rework rate of the products because of the bad hole is quite high. In this research graphite/honeycomb composite material and aluminum sheet metal has been used. The results show that drill geometry, speed and feed rate have substantial effects on the hole quality and also there was gradual variation of the thrust and lateral forces with feed rates.
2002-11-05
Technical Paper
2002-01-3007
Michael Papadakis, Hsiung-Wei Yeong, Reuben Chandrasekharan, Mike Hinson
Experimental studies were conducted to investigate the effect of tailplane icing on the aerodynamic characteristics of 15%-scale business jet aircraft. The simulated ice shapes selected for the experimental investigation included 9-min and 22.5-min smooth and rough LEWICE ice shapes and spoiler ice shapes. The height of the spoilers was sized to match the horns of the LEWICE shapes on the suction side of the horizontal tail. Tests were also conducted to investigate aerodynamic performance degradation due to ice roughness which was simulated with sandpaper. Six component force and moment measurements, elevator hinge moments, surface pressures, and boundary layer velocity profiles were obtained for a range of test conditions. Test conditions included AOA sweeps for Reynolds number in the range of 0.7 based on tail mean aerodynamic chord and elevator deflections in the range of -15 to +15 degrees.
2002-04-16
Technical Paper
2002-01-1537
Bert L. Smith, John S. Tomblin, K. S. Raju, K. H. Liew, A. K. M. Haque, Juan C. Guarddon
During this study, a number of 8.5-inch by 11.5-inch flat honeycomb sandwich panels were inflicted with low energy impact damage, inspected non-destructively, and tested for residual in-plane compressive strength. Each panel had either a 3/8-inch or 3/4-inch low density Nomex honeycomb core, and either 2-ply, 4-ply or 6-ply face sheets. The face sheets were either carbon or Eglass (prepreg) fabric. The panels were either clamped or simply supported in a test fixture during impact from a gravity assisted drop mechanism, and impacted with either a 1-inch or 3-inch diameter spherical indenter. After impact the damage to each panel was characterized by (1) ultrasonic through-transmission to obtain a c-scan representing planar damage area, (2) indentation volume and depth, and finally (3) visual inspection to rate the damage according to a predetermined rating scale. The panels were then tested for in-plane compressive strength.
2002-04-16
Technical Paper
2002-01-1538
T. E. Lacy, I. K. Samarah, J. S. Tomblin
The coupled influence of material configuration (number of facesheet plies, core density, core thickness) and impact parameters (impact velocity and energy, impactor diameter) on the impact damage resistance characteristics of sandwich composites comprised of carbon-epoxy woven fabric facesheets and Nomex honeycomb cores was investigated using empirically based quadratic response surfaces. The diameter of the planar damage area associated with TTU C-scan measurements and the peak residual facesheet indentation depth were used to describe the extent of internal and detectable surface damage, respectively. Estimates of the size of the planar damage region correlated reasonably well with experimentally determined values. For a fixed set of impact parameters, estimates of the planar damage size and residual facesheet indentation suggest that impact damage development is highly material and lay-up configuration dependent.
2002-04-16
Technical Paper
2002-01-1534
Bert L. Smith, Ala L. Hijazi, Roy Y. Myose
An aging aircraft accumulates fatigue cracks commonly referred to as multiple site damage (MSD). A simplified engineering fracture mechanics model, generally referred to as the linkup model (or plastic zone touch model), has been used with some success to describe the MSD fracture phenomenon in 2024-T3 aluminum panels. A disadvantage of the linkup model is that it gives excessively inaccurate results for some configurations. A modified linkup model has been developed through empirical analysis of test data taken from unstiffened panels with MSD cracks at open holes. The modified linkup model was then validated with test data from stiffened panels including single-bay panels with the lead crack centered between stiffeners and two-bay panels with the lead crack centered beneath a severed stiffener. Further validation of the modified linkup model was done with test data from panels with bolted lap joints. Test results were obtained from 112 different panels.
2002-04-16
Technical Paper
2002-01-1517
I. Syed, B. Bahr, J. Sha, F. Tadayon
This paper presents the experimental study of hole quality parameters in the drilling of titanium alloy (6Al-4V). Titanium alloy plates were drilled dry using three types of solid carbide drills i.e. 2-flute helical twist drill, straight flute and three-flute drill. The objective was to study the effects of process parameters like feed rate, speed and drill bit geometry on the hole quality features. Typical hole quality features in a drilling process are the hole quality measures such as surface roughness, hole diameter, hole roundness and burr height. The results indicate that proper selection of speed, feed rate, and drill geometry can optimize metal removal rate and hole quality.
2002-04-16
Technical Paper
2002-01-1516
R. Madhavan Nair, B. Durairajan, B. Bahr
The competitive market has forced the industry to develop methodologies to reduce lead-time of the products without sacrificing quality. One of the major metal removal operations in the aerospace industries is drilling. Over 100,000 holes are made for a small single engine aircraft. Naturally, demand for faster production rate results in the demand for high-speed drilling. But the cost of hole-making operations becomes a significant portion of the total manufacturing cost. This paper discusses the high speed drilling of Al-2024-T3 alloy, the effect of feed and speed on hole quality features like oversize, roundness error, burr height and surface roughness.
2002-04-16
Technical Paper
2002-01-1526
J. Sheikh-Ahmad, G. Sridhar
The work presented here illustrates the wear behavior of CVD diamond coated carbide tools during the machining of carbon fiber-reinforced composites. Cutting experiments were conducted on a CNC milling machine for edge trimming of a 9-mm thick multi-layered carbon fiber-reinforced epoxy laminate in a climb cutting configuration. The effects of feed speed and diamond film thickness on the wear behavior of the coated tools were determined. In addition, characteristics of the worn cutting edge were studied using optical and scanning electron microscopes. It was shown that diamond coated tools generally performed better than the uncoated tools under all conditions. Uniform wear by abrasion of the diamond film, without exposing the substrate, was obtained when cutting at low feed speeds with thicker coatings. At higher feed speeds the wear of the coated tools was characterized by abrasion through the diamond film and exposure and wear of the substrate.
2002-04-16
Technical Paper
2002-01-1515
J. Sha, Behnam Bahr
Metal cutting is a substantial constituent of airframe manufacturing. During the past several decades, it has evolved significantly. However, most of the changes and improvement were initiated by the machine tool industry and cutting tool industry, thus these new technologies is generally applicable to all industries. Among them, few are developed especially for the airframe manufacture. Therefore, the potential of high efficiency could not be fully explored. In order to deal with severe competition, the aerospace industry needs improvement with a focus on achieving low cost through high efficiency. The direction of research and development in parts machining must comply with lean manufacturing principles and must enhance competitiveness. This article is being forwarded to discuss the trend of new developments in the metal cutting of airframe parts. Primary driving forces of this movement, such as managers, scientists, and engineers, have provided significant influence to this trend.
2002-04-16
Technical Paper
2002-01-1514
A. H. Adibi-Sedeh, V. Madhavan, B. Bahr
A generalized upper bound model for calculating the chip flow angle in oblique cutting using flat faced tools with single cutting edge and multiple or curved cutting edges has been developed. The chip flow angle and chip velocity are obtained by minimizing the cutting power with respect to both these variables. The chip flow angles predicted by this model show good agreement with experimental values of chip flow angles for various tool geometries and cutting conditions. The model has the potential to be extended to the more complex machining processes such as drilling and milling.
Viewing 1 to 23 of 23

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