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Aviation regulations requires that engine mounts, and other flight structures located in designated fire zones must be constructed of fireproof material so that they are capable of withstanding the effects of fire. Historically, steel is defined as being inherently fireproof, however, titanium was not. Therefore, a fireproof test was conducted using 6AL-4V titanium structure for the attachment of the propulsion system on a mid-size business jet to satisfy FAA Federal Aviation Requirement 25.865. To determine if the titanium structure would be able to support normal operating loads during the fire event, finite element analysis was performed on the titanium structure simulating the fire test. The fire test simulates a fire on the aircraft from the propulsion system by using a burner with jet fuel exposing the component to a 2000 °F (1093°C) flame. The 2000 °F (1093°C) Flame is calibrated based on FAA Advisory Circular AC20-135.

Abrasive blasting and chemical etching processes are often performed on titanium substrates to improve the adhesion performance of paints, coatings, and adhesives. Abrasive blasting and chemical etching processes alter the physical metallurgy of surfaces so they can produce varied and uncertain effects on the fatigue life of the substrate. The fatigue life of titanium subjected to various blasting intensities and etching has been determined and statistically analyzed. The results of this work indicate that, for titanium alloys, increased aluminum oxide abrasive blasting intensities decrease fatigue life and that chemical etching also decreases fatigue life.

Torsional rubber heavy vehicle suspensions have been used for over 60 years. The historical background makes an interesting engineering case study. A new simplified updated redesign of the system has been accomplished. It retains the long-life, relatively soft spring rate and roll stability advantages of the original design. Reduced adhesion stresses and a simplified vehicle leveling system are new advantages. Vehicle comparison testing with other suspension systems indicates significant improvement in ride comfort, stability and vibration reduction. Future designs will likely use new more sophisticated compression springs operating in combination with the torsional springs to further improve the ride.

This paper describes the fundamental concepts of semi-active control, and the development and testing of a semi-active suspension on an M551 tank. The single degree-of-freedom (SDOF) model of a vehicle suspension is used in explaining the basic concepts. Background information is presented on conventional, fully active, and optimal suspension systems. One goal of this paper is to give the reader an intuitive “feel” for semi-active control. Primary vehicle suspension systems are a natural application for semi-active control, but the concepts apply equally well to general vibration isolation problems.

Controlling the vibration and internal cabin noise levels of fixed wing aircraft has long been a challenge and neverending trade off of system performance variables. A presentation of the fundamental aspects of vibration and how it relates to fixed-wing aircraft engine attachment is made. Available technologies related to engine vibration treatments are presented with a preferred design approach.

Vibration and shock isolation pose conflicting design requirements in vehicle seating; thus, conventional passive seat suspensions are typically designed to optimize either vibration or shock isolation, depending on the application. Semi-active suspensions can significantly reduce this tradeoff, providing additional vibration and/or shock protection. For this experiment, a commercial vehicle seat was excited by a simulated pothole and random vibration containing shocks with both the standard passive damper and a commercial semi-active damper. The input vibration required to cause end-stop impacts, and the vibration and shock isolation performance were measured and compared. The results showed that the semi-active damper significantly reduced VDV ratios as well while improving overall.

Adhesive bond-line read-through is a visible distortion of the substrate over a cured adhesive bond-line. Bond-line read-through deformations are primarily the result of a difference in the thermal expansion coefficients between the substrate and the adhesive. Substrate and adhesive thermo-mechanical properties play a large role in determining the severity of the distortions. This work describes the approaches taken to understand, predict, and minimize bond-line read-through. It presents a simple model which relates physical deflections in SMC (Sheet Molding Compound) sheets to the thermal stresses that arise as part of the adhesive cure cycle. Model predictions of both the shape and magnitude of the deflection over the bond-line will then be experimentally verified for two extreme types of bond designs. General approaches for reducing bond-line read-through by way of process, part design, and adhesive formulation modifications will be discussed.

15-5PH is a precipitation-hardening, martensitic stainless steel used for primary structural elements such as engine mounts where corrosion resistance, high strength, good fatigue and fracture toughness is required. The material composition is defined in AMS5659M. This alloy can be either Type 1 - vacuum arc remelt (VAR) or Type 2 - electro slag remelt (ESR) and is most commonly heat treated per SAE AMS-H-6875 or AMS2759/3 to condition H1025 (an ultimate tensile strength of 155 ksi [1070 MPa] minimum). Typically material handbooks have limited fatigue data and most data is only for Type 1. Therefore, the fatigue properties of 15-5PH H1025 stainless steel for both Type 1 and Type 2 were determined. The objective of the fatigue testing was to generate a family of S-N curves (maximum stress versus number of cycles to failure) for a series of stress ratios across the entire range of cycles to failure.