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Technical Paper

Evaluation of Alternatives to Electrodeposited Cadmium for Threaded Fasteners Applications (III)

2009-11-10
2009-01-3228
Since 2005, Alcoa Fastening Systems (AFS) and Lockheed Martin have been partnering to identify a Cadmium (Cd) plating replacement for threaded fasteners. Previously reported Phase I, II and III studies resulted in alternative coatings that indicated promise as suitable plating materials. Phase IV and V studies continued the program by testing two different fasteners (NAS1580 and NAS4452) manufactured in AFS facilities. Testing included plating material characterization such as coating thickness, torque-tension relationships, locking and breakaway torque measurements, salt spray (fog) corrosion, stress corrosion, and push-in and interference properties. Additionally, mechanical properties of the plated fasteners were tested (tensile, double shear, durability, and fatigue). Candidates included two electroplated zinc-nickel coating systems (Zn-Ni and Zn-Ni2) and an electrodeposited aluminum coating (AI).
Technical Paper

A Quick Change System for Portable Fastening Tooling Systems

2009-11-10
2009-01-3269
The installation of aerospace fasteners with pneumatic or cordless tools generally requires specialized systems which are dedicated to the fastener hex size and torque, often requiring laborious disassembly for a configuration change. This paper presents a quick change system that can be used together with a large variety of tooling configurations and provides instant socket exchange without requiring wrenching or disassembly. A comparison with traditional socket system is made, highlighting the characteristics and benefits of this new technology in terms of ergonomics, productivity and cost.
Technical Paper

Evaluation of Alternatives to Electrodeposited Cadmium for Threaded Fastener Applications (II)

2008-09-16
2008-01-2312
Cadmium electroplating is coming under increasing pressure due to both environmental and worker safety issues. Since 2005, Alcoa Fastening Systems (AFS) and Lockheed Martin have been conducting a collaborative research program to identify the most appropriate fastener coating materials for a Cadmium (Cd) plating replacement. Four candidate coatings were selected for the initial Phase I evaluation: electroless nickel (EN), electroless nickel composite (EN-PTFE), electrodeposited surface mineralization based zinc-nickel (Zn-Ni), and electroplated aluminum (Al). The Phase I testing results indicated that the Zn-Ni and Al coatings were the best of the four candidates for Cd replacement. However, it is hard to conduct direct comparisons with different coating thicknesses, surface treatments, and lubrication among various Cd alternatives. Thus, further evaluation with more careful control of these parameters would be necessary.
Technical Paper

Effects of Fastener Coating and Shear Strength on Joint Lap Shear Strength

2008-09-16
2008-01-2311
In aerospace fastener industry, all materials used or being considered for fastener applications must meet specified minimum shear strength values tested via single-shear test and double-shear test. However, shear testing results are not as precise as tension and compression testing due to the introduction of friction and bending forces in the testing process, resulting in the difficulty in obtaining accurate test data. Previous study showed the various effects of coating tribology on fastener single and double shear strength. Experimental results, statistical analysis and finite element analysis all confirmed that surface tribology could significantly affect the shear strength test results. Comparing to un-coated or bare fasteners, confirmed that fasteners from the same lot exhibited significantly lower shear strength values after coating. This effect is well known in the Aerospace fastener industry.
Technical Paper

Effects of Coating Tribology on Fastener Single and Double Shear Strength

2006-09-12
2006-01-3155
In aerospace fastener industry, all materials used or being considered for fastener applications must meet specified minimum shear strength values. It is widely known that shear strength is dependant on the type of shear test. However despite the suspected test dependencies, no detailed open research literature on the fastener shear test, especially shear strength variation via single and double shear approaches, and factors including surface coatings that affect tested shear values, has been conducted. Thus, the objective of this program is to systematically evaluate the effect of coating tribology on the threaded fasteners shear property tested via single shear and double shear testing methods. Five most common fastener finishes were selected, including uncoated, Aluminum CVD, Hi-KOTE, MoS2 coated, and Anodized.
Technical Paper

Evaluation of Alternatives to Electrodeposited Cadmium for Threaded Fastener Applications

2006-09-12
2006-01-3169
Cadmium (Cd) plating offers good corrosion resistance, lubricity, solderability, adhesion, and ductility, as well as consistent torque-tension and uniform thickness on components with complex geometries. However, the intrinsic Environmental, Health, and Safety issues associated with Cd have driven many users to seek alternatives. Currently, various Cd replacement teams/programs such as the Joint Group on Pollution Prevention (JG-PP)/Boeing, the Joint Cadmium Alternatives Team (JCAT), the Canadian Cadmium Replacement Program (CCRP), and the REFOCUS Program (AEA Technology, European) have been investigating alternatives to Cd plating. Some of the current coatings being considered in the aerospace industry include Zn-Ni alloy plating, electrodeposited aluminum, electroless nickel, nickel composite, and molten salt aluminum manganese (Al-Mn). Each option has its own particular characteristics; however, most experiments have been conducted on aerospace structural panels or components.
Technical Paper

Development of an Automated Part Loading and Unloading System for a Cylindrical Die Thread Roller

2007-09-17
2007-01-3916
This paper outlines the design of a part transport and loading/unloading automation system for a cylindrical die thread roller, enumerating many of the design decisions encountered. Specifically, a transport tray system is proposed and prototyped as a benchmark for factory automation. Details of an automation system which will interface with the proposed transport tray system are discussed. A gripping system which accommodates a wide variety of fastener head styles is developed to work in conjunction with the tray concept, and prototyped with favorable results.
Technical Paper

Influence of Fastener Coatings on Fretting Fatigue

2007-09-17
2007-01-3890
Previous fatigue tests on mechanically fastened aerospace joints showed fatigue cracks often initiated in the countersink of the fastener hole where the fastener head was in contact with and caused fretting on, the hole bore. The work presented here evaluated the potential of a number of possible fastener coatings to reduce fretting and increase the fatigue life of the joint. The coatings were tested in a fretting fatigue test and in a ‘zero load’ fatigue test. The results showed that the best fretting resistance and fatigue life was obtained when aluminum pigmented coating (in accordance with NAS 4006) was used. The results also suggest that both test methods provide a similar ranking of performance. This means that the simpler fretting fatigue test may be useful as an initial screening method. However, more testing is needed to confirm this relationship.
Technical Paper

Portable Fastener Delivery and Installation System

2003-09-08
2003-01-2953
The Portable Fastener Delivery System or PFDS, has been developed at the Boeing St. Louis facility to streamline the manual fastener installation process. The PFDS delivers various fasteners, on demand, through a delivery tube to an installation tool used by the operator to install the fasteners in an aircraft assembly. This paper describes the PFDS in its current configuration, along with the associated Huck® International (now Alcoa Fastening Systems) installation tooling, as it is being implemented on the F/A-18E/F Nosebarrel Skinning application. As a “portable” system, the PFDS cart can be rolled to any location on the shop floor it might be needed. The system uses a removable storage cassette to cache many sizes and types of fasteners in the moderate quantities that might be required for a particular assembly task. The operator begins the installation sequence by calling for the particular fastener grip length needed using a wireless control pendant.
Journal Article

FC43®: A New Structural Panel Fastener

2012-09-10
2012-01-1888
Structural panel fasteners have been used in the aerospace industry for longer than the previous half century. This paper presents the new FC43® Panel Fastener with a novel retaining feature which enables the use of a full shank stud. The retaining feature can be used with a variety of thread configurations and is independent of nut style or head configuration, providing an unprecedented modularity for this type of fastening system. With a stud design that is free of slots or axial recesses, the FC43® provides higher mechanical performance than existing equivalent panel fasteners. Mechanical characteristics and performance comparisons with the most commonly used panel fasteners in the aerospace industry are also presented.
Journal Article

The Effects of Surface Texture on Fretting Fatigue between Fastener and Aluminum Structure

2010-09-28
2010-01-1854
Multi-fastener lap joints are vulnerable to fretting fatigue when they are subjected to repeated loading. In general the fretting fatigue condition leads to degraded properties of metallic structures due to the presence of the surface stress concentration resulting at the sites of fretting pits. In many cases, fretting can result in premature structure failures therefore a series of counter measures are frequently taken to minimize fretting especially at the fastener holes. One of major factors that affect the fretting phenomena between the fastener and fastener hole is the surface condition of the fasteners. In this study, the influences of the surface texture and the surface plating of the fastener on the joint life were investigated by conducting double lap shear fatigue testing. It has been found that the joint fretting fatigue resistance is very sensitive to the surface texture of the fastener and as the surface roughness of the fastener is reduced the joint life increases.
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