This paper presents the development of an accumulative damage model based on continuum damage mechanics (CDM) to simulate the bearing failure and response in the bolted composite joints. The simulation is implemented into a general-purpose FEM code ABAQUS. The main damage mechanisms observed from experimental study are described as accumulated compressive damage that appeared by matrix compression failure and fiber compression-shear failure. The fundamental approach consists of contact problem at the pin/hole interface, progressive damage, large deformation problem and material nonlinear problem. A complex approach based on a nonlinear shear elasticity theory combined with a continuum damage mechanics approach can be also utilized to represent the material nonlinear behavior during loading. The damage accumulation criteria using the hybrid method based on Hashin and Yamada-Sun’s failure criteria are adopted, and the stress redistribution analysis using a degradation model for the damaged ply is performed. The accurate prediction results include progressive damage and strength response of the joints that agrees well with the existing experimental data.
This paper presents flight control designs of an unmanned space vehicle, HOPE-X vehicle using an interpolation gain scheduling technique. The ν-gap metric is used to evaluate the errors between linear models at operating points. The linear parameter varying models for the HOPE-X vehicle were then constructed by minimizing two types of indices defined with the ν-gap metric. On the other hand, the magnitude of the input is locally constrained to avoid the saturation of the control surfaces. In the numerical simulations of the HOPE-X, the gain scheduling control laws whose number of operating points was greater than two could be applicable to the whole region of the terminal area energy management phase of the HOPE-X. Furthermore, the input constraint was effective to suppress the magnitude of the input and to extend the stability region of the design parameter.
This paper proposes a new collision avoidance control law of aircraft. RCPA (Range of Closest Point of Approach) representing risk in the future and TCPA (CPA time to go) representing current risk are used as risk functions. Also fuzzy logic is introduced to achieve the human maneuvering and to settle singular point and chattering problems that are shown in previous studies. Avoidance strategy consists of four main phases; course keeping, avoidance, parallel flight, and recovery phase; and three intermediate phases. Parallel flight phase and three intermediate phases are introduced to achieve moderate avoidance and smooth phase transition, respectively. Simulation results show that the proposed control law settles the past problems and achieves the smooth and adequate avoidance. This paper also discusses on the fuzzy evaluation method.
The Structures and Materials Research Center of the National Aerospace Laboratory of Japan (NAL) and Kawasaki Heavy Industories, Ltd. (KHI) conducted a vertical drop test of a fuselage section cut from a NAMIC YS-11 transport airplane at NAL vertical drop test facility in December 2001. The main objectives of this program were to obtain background data for aircraft cabin safety by drop test of a full-scale fuselage section and to develop computational method for crash simulation. The test article including seats and anthropomorphic test dummies was dropped to a rigid impact surface at a velocity of 6.1 m/s (20 ft/s). The test condition and result were considered to be severe but potentially survivable. A finite element model of this test article was also developed using the explicit nonlinear transient-dynamic analysis code, LS-DYNA3D. An outline of analytical method and comparison of analysis result with drop test data are presented in this paper.
The erosive burning effects in a small test motor loaded with practical composite propellants have been investigated in detail by using an X-ray absorption diagnostics to measure the propellant local regression. The motor was specially designed to have two propellant slabs and was called as DSM (Double Slab Motor). Significant erosive burning was forced to occur in the motor by varying combustion pressure and mass flux in the port. A new simple correlative equation is derived, which predicts accurately not only pressure history but also local regression of burning surface. The equation is characteristic in the non-dimensionalized threshold mass flux and includes the terms to consider both effects of pressure and of motor scale.
Aircraft conceptual design method currently used for the university design education mainly utilises empirical values based on the statistical database to determine the main design parameters. Therefore, it is often difficult for students to understand the effects of aerodynamic parameters such as a wing aspect ratio and a taper ratio during the design process. In this paper, a conceptual design method that incorporates a boundary element method is discussed so that aerodynamic characteristic estimations are possible and that the students can easily comprehend the effects of aerodynamic parameters while designing the airplane. A single engine light airplane has been designed by the present conceptual design method. The results obtained by the present method and those by the conventional method are compared and discussed.
This paper deals with a guidance law for a flight vehicle with varying velocity after thrust cutoff. This guidance law is mechanized by combining the proportional navigation and the pure pursuit navigation with the mixture ratio. Since the performance of the guidance law depends on the ratio, the discussion is focused on the determination of the ratio. Finally, the simulation results show that if the LOS angle noises are small, the proposed guidance law is effective even if the missile velocity decreases and has higher off-boresight ability than the proportional navigation.
As for the design of the flight control system, it is necessary to have good handling qualities as well as having highly stability margin of the system. If feedback gains are merely modified in order to recover the stability margin of the system which is designed regard the closed system response as important, the proper position of poles and zeros collapse, and characteristics of the response receive a bad influence. Lateral-directional flight control system was taken for instance, this paper proposes a technique to design the feedback control law for which to be compatible with both characteristics of the response and the stability very well. Feedback gains are modified to increase the stability margin with that condition of the position of the complex zeros are same as the Dutch roll poles and the position of the spiral pole is coincide with the origin kept by using -90° phase locus method. This permits a designer to get a control system with large phase margin, and this is especially effective in the case that large delay is entailed in the system.
A full-size model of a lunar rover using a laser energy transportation to confirm directly the existence of ice on the moon has been fabricated and 100 m energy transportation test has been successfully performed. Problems to be solved to realize an actual lunar ice exploration mission are discussed.