F-14 Tail Hook Analysis

Topics: Force, Shear stress, F-14 Tomcat Pages: 5 (958 words) Published: October 21, 2013

DP 209
Degree Project
F-14 Tomcat Tail Hook Safety Analysis Under Impact Load

Instructor:
Submitted By:

Wycliffe Falconer

Table of Contents

Abstract ……………………………………………………………... 4

Introduction ……………………………………………………………. 5

About the Material …………………………………………………… 6

Calculations ……………………...…………………………………. 7

Analysis on Catia …………………………………………………….. 11

Example of Failure …………………………………………………….. 13

Conclusion …………………………………………………………… 14

References …………………………………………………………….. 15

Abstract

The United States Navy's aircraft carrier is capable of launching and recovering airplanes out to see. Catapults that can reach speeds of 160 miles in less than a second are used to launch the airplanes from the flight deck of the aircraft carrier to the air. In order for these aircrafts to be recovered, a tail hook is used which catches a wire on the flight deck that slows down the aircraft to a complete stop in less than 40 ft. These tail hooks are only seen in military airplanes. Knowing the dimensions of the tail hook, a replica is redrawn using CATIA V5. The safety requirements that must met are also based on the characteristic of the airplanes, the weight and the minimum speed required for them not to stall in the air and crash on the flight deck. The report will show a safety analysis on the tail hook and the fused pin-clevis; from the forces acting on the tail hook at the moment of landing. This report will focus on the Factor of Safety of the hook and the bracket end. Factor of safety shows us how strong the structure is than it usually needs to be for an intended load.

Introduction

Our team has agreed to analyze the F-14 Tomcat tail hook. A replica of the hook will be redrawn on CATIA V5. Knowing the maximum load applied to the hook, calculated based on the maximum weight and maximum speed at landing; a safety analysis is conducted to determine the factor of safety of the hook, the bracket, and the at the fused pin-clevis end. Calculating the factor of safety on the hook and the bracket end will help us determine where the fracture will most likely occur in the case of a failure.

About the Material

The tail hook is made of alloy steel. The alloy steel is a material very resistant capable of withstanding forces of grate magnitude either tension or compression. Steel is not an element; it is an alloy of iron containing less than 1% carbon to make it stronger. The process of steelmaking had multiple changes in the last century to meet regulations based on the political, social and technological atmosphere, especially in the last decades since global warming became the most important factor. Steelmaking involves three steps which are melting, purifying and alloying. In the alloying process it is mixed with other elements such as manganese, nickel cobalt; depending on the desired alloy properties. The density of the alloy steel is 7850 kg/m^3, the elastic modulus is 190-210 GPa and the yield strength is 366-1793 MPa. These properties make the alloy steel the most suitable material for the Tomcat from an engineer’s perspective.

Calculations

P = Impact Load = 225 Kip F.S. = Factor of Safety D = Diameter of Tail Hook = 3.75 in Fs = Shear Force d = Diameter of Pin = 1.65 in.

Calculating the Stress applied at hook
Equation for stress
σapplied = P/Ahook + (Mz*C/Iz)

Area of the hook Ahook = (π * D^2)/4
Ahook = (3.1416) *(3.75 * 3.75) /4
Ahook = 11.044
Moment about neutral axis
Mz = Force x Distance
Mz = 225 * 2 = 450 Kip * in
Inertia at neutral axis
Iz = (π * D^4)/64
Iz = (3.14) (3.75^4)/64
Iz = 9.7

Now that we have...


References: Chatterjee, Amit. "Recent Developments in Ironmaking and Steelmaking." Iron and Steelmaking. 22:2 (1995), pp. 100-104
U.S. Department of Commerce. 1992 Census of Manufacturers — Blast Furnaces, Steel Works and Rolling and Finishing Mills. 1992.
Illinois University. http://www.istc.illinois.edu/info/library_docs/manuals/primmetals/chapter2.htm
Mechanics of Materials. Fifth Edition. Beer, Johnston, DeWolf and Mazurek.
Chapter 4 Pages 216-222

http://www.navy.mil/navydata/fact_display.asp?cid=1100&tid=1100&ct=1
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