Patent Application
20200039641
Abrasions strips are attached to the leading edges of rotor blades to protect the rotor blades from being damaged by high-speed impact of airborne debris and/or water. Most conventional abrasion strips are composed of a stainless-steel base layer with a nickel cap attached thereto. The stainless steel base layer is formed by bending and/or stretching a sheet of stainless steel over a die. Then, a nickel cap is either electroplated directly onto the formed stainless steel base layer, or the nickel cap is created via electroless nickel plating and the nickel plate is then bonded or mechanically fastened to the stainless steel base layer.
However, stainless steel has a minimum bend radius that is larger than what is often preferred for aerodynamically optimal rotor blade design, particularly toward the rotor blade tip as the radius of the leading edge tapers down. In addition, nickel electroplating and electroless nickel plating is a very expensive and extremely complicated, particularly when forming complex shapes. As such, abrasion strips that have complex profiles along the span of the rotor blades are usually formed in several parts that are then separately attached.
Precision repeatability is also difficult to achieve with nickel plating. Given the immense importance to the aerodynamic performance and balance of the rotor blades, it is imperative that all the abrasions strips match each other as closely as possible. Therefore, a large amount of time is spent manually abrading and/or chemically stripping excess material from the nickel caps in order to achieve the desired profile. Moreover, as rotor blade design continues to evolve, more complex leading edge shapes are being utilized, exacerbating the difficulty in forming the required abrasion strips.
In this disclosure, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of this disclosure, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction. In addition, the use of the term “coupled” throughout this disclosure may mean directly or indirectly connected, moreover, “coupled” may also mean permanently or removably connected, unless otherwise stated.
This disclosure divulges abrasion strips formed of INCONEL® alloy 718SPF™ and a method of manufacturing the same. INCONEL alloy 718SPF™ was developed to meet the need for an alloy suitable for manufacture into components subject to a combination of high temperature, high-temperature corrosion, and high stress. INCONEL® alloy 718SPF™ has excellent creep-rupture strength at temperatures up to 1300 degrees Fahrenheit (700 degrees Celsius). As such, INCONEL® alloy 718SPF™ is used for the manufacture of components in gas turbines, rocket engines, nuclear reactors, and spacecraft. Helicopter rotor blades are never subject to the conditions INCONEL alloy 718SPF™ was designed for. In addition, INCONEL® alloy 718SPF™ has inferior abrasion resistance when compared to a 100 percent nickel or an 85+percent nickel-phosphorous alloy, as produced from electroplating or electroless plating, respectively. However, because INCONEL® alloy 718SPF™ does include 50 to 55 percent nickel and 17 to 21 percent chromium, it has fairly robust abrasion resistance. It also has the ability to be superplastically formed into complex shapes, in an accurate and repeatable manner. Therefore, even though abrasion strips formed of INCONEL® alloy 718SPF™ may have inferior wear properties compared to the nickel-capped abrasion strips currently used, the time/labor savings afforded by manufacturing complexly shaped abrasion strips by superplastic forming can outweigh the relatively shorter service life of the INCONEL® alloy 718SPF™ abrasion strips disclosed herein. The composition and physical properties of INCONEL® alloy 718SPF™ are described in Special Metals Corporation's Publication Number SMC-096, September 2004, which is incorporated by reference herein in its entirety.
Referring to
As shown in
Given the complexity of leading edge 214, it would be nearly impossible to fabricate a unitary abrasion strip for rotor blade 210 utilizing conventional methods. As described in further detail below, this tapering of material from middle 244 to top end 246 and bottom end 248, as well as tapering from tip 236 to root end 218, results from what is often considered an undesirable side effect of superplastic forming. That is, the further the material is stretched from its original form, the thinner the material becomes. When creating an abrasion strip by superplastic forming, that normally undesirable side effect leads to a desirably contoured cross-sectional profile.
Referring to
In addition to producing the chordwise thickness variation formed by the orientation shown in
Sheet 304 may be pre-shaped in any variety of ways to aid in achieving the final desired shape, including by cutting, bending, and even welding additional sheets of INCONEL® alloy 718SPF™ to sheet 304. In addition, INCONEL® alloy 718SPF™ may be heat treated to further increase the durability of the formed abrasion strip.
While this disclosure shows and discusses rotor blade abrasion strips superplastically formed of INCONEL® alloy 718SPF™ for use with tiltrotor aircraft 100, it should be understood that the abrasion strips, and methods for manufacturing the same, disclosed herein may be used for any rotary blades that may benefit from utilizing abrasions strips.
At least one embodiment is disclosed, and variations, combinations, and/or modifications of the embodiment(s) and/or features of the embodiment(s) made by a person having ordinary skill in the art are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numerical range with a lower limit, Rl, and an upper limit, Ru, is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=Rl+k*(Ru−Rl), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . 50 percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 95 percent, 98 percent, 99 percent, or 100 percent. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. Use of the term “optionally” with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives being within the scope of the claim. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Accordingly, the scope of protection is not limited by the description set out above but is defined by the claims that follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present invention. Also, the phrases “at least one of A, B, and C” and “A and/or B and/or C” should each be interpreted to include only A, only B, only C, or any combination of A, B, and C.
