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Transient response of structures with uncertain properties to nonlinear shock loading

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... The shock response spectrum (SRS) is an effective standard tool for engineering analysis and environmental impact quantification [6]- [8]. It describes the relationship between the maximum absolute response and natural frequency of a series of single-degree-of-freedom (SDOF) oscillators in a given base excitation. ...
... Third, we ensure that the individuals with less than the ideal value (from f max to f avg for minimal optimization) maintain high crossover and mutation rates. Therefore, the values of P c and P m are tuned adaptively and nonlinearly at both branches via the following sigmoid function: (6) where, A = 9.903438. The adjustment curve of probability is presented in Fig. 8. ...
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The shock response spectrum (SRS) applied to pyroshock designs and tests for space systems does not include input acceleration time history; therefore, it cannot be used directly in structural nonlinear dynamic analysis before acceleration time history is synthesized. Existing synthesis methods typically rely on certain experimental data. In this study, a combined method for pyroshock acceleration synthesis is presented using a series of wavelets at low frequencies and damped sines at medium-high frequencies in the absence of experimental data. To improve the quality of the synthesized SRS, we develop an improved adaptive genetic algorithm (IAGA) with nonlinear adaptive adjustments of crossover and mutation probabilities. Numerical tests show that combined with the developed IAGA, the new method achieves higher accuracy and practicability in the synthesis of pyroshock acceleration compared with traditional methods. This work is expected to improve the calculation accuracy of spacecraft structure response under pyroshock loads.
... Li and Hua 8 calculated the transient vibration characteristics of the laminated composite cylindrical shells with infinite length, caused by the pressure wave from an underwater shock by the reflected-afterflow virtual-source (RAVS) method. Caresta et al. 9 predicted the transient response of a structure at the driving point following an impact or a shock loading based on random point process theory. The theory was applied to a wide range of structures and the results were experimentally verified for the case of a rigid object hitting a beam, a plate, a thin and a thick cylinder, and for the impact between two cylinders. ...
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This paper mainly focuses on the remarkable transient vibration and underwater acoustic radiation when the underwater vehicle changes direction or depth, and a short time Fourier transform signal processing method to evaluate transient vibration and acoustic radiation of steering engine is provided in this paper. Based on the vibration test of the 1:1 experimental scaffold of the steering engine for an underwater vehicle, the transient maximum excitation forces acting at the contact points between steering engine and experimental scaffold are calculated indirectly by the least square method of load identification in frequency domain and the short time Fourier transform signal processing method. The accuracy and feasibility of results are verified. In addition, taking excitation forces as an approximate input, the numerical solution of transient acoustic radiation for a cylindrical shell with ribs of the steering engine room, based on elastic shell theory and fluid–structure interaction theory, is presented. In the simulation, the steering engine room of the underwater vehicle is simplified into a cylindrical shell with two simply supported tips, because a cylindrical shell with ribs is the basic structure-borne used in underwater vehicles. The results show that transient acoustic radiation of the tested steering engine is higher than allowable value, while the evaluation results of another electric steering engine without retarder are suitable.
... Alexander et al. [13] predicted analytically the acceleration field and the corresponding SRS including the propagation and reflection of longitudinal waves because of the in-plane impact of a hammer pendulum by using Hertzian contact theory, the Galerkin procedure and numerical integration. Caresta et al. [14] presented a method to predict the transient response of a structure to a shock loading and calculated the displacement and the contact force by solving the discrete convolution between the impulse response and the contact force expressed in terms of a nonlinear Hertzian contact stiffness. ...
Article
The effect of different fiber orientations of composite panels of E-Glass/Epoxy under far-field pyroshock is presented in this article. To get the far-field pyroshock response, the experiments are conducted using Bi-plate technology under low range of input chamber pressures to projectiles of three different lengths. PCB accelerometers and NI-DAQ system with LabView software are used to capture the structural responses in the form of acceleration-time histories and analyze them at selected locations. Abaqus/Explicit code is used in the Finite Element Analysis (FEA) for the pyroshock response of composite panels with different fiber orientations. From the results, it is found that the selected locations on the [0/90/±45]s WRM (Woven Roving Mat) laminate experience higher accelerations, above 30% extra, than other fiber orientations. Since [0/90/±45]s laminate has lengthier fiber rovings along the diagonal direction, higher Young's modulus along the fiber direction and the most vibration modes are diagonally biased, the response amplitude would be high enough to experience maximum acceleration. The acceleration responses are obtained both from FEA and experiments and show good agreement. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers
... Li and Hua 8 calculated the transient vibration characteristics of the laminated composite cylindrical shells with infinite length, caused by the pressure wave from an underwater shock by the reflected-afterflow virtual-source (RAVS) method. Caresta et al. 9 predicted the transient response of a structure at the driving point following an impact or a shock loading based on random point process theory. The theory was applied to a wide range of structures and the results were experimentally verified for the case of a rigid object hitting a beam, a plate, a thin and a thick cylinder, and for the impact between two cylinders. ...
Article
When an underwater vehicle changes directions by the steering engine, the opening process of steering engine generates a high transient radiation noise. So before a steering engine is installed in an underwater vehicle, it is necessary to estimate transient radiation noise of the steering engine. In this paper, based on the vibration test of the steering engine for an underwater vehicle, the transient maximum and mean excitation forces acting on the positions of connections between steering engine and experimental setup are calculated indirectly by least square method of load identification in frequency domain and STFT signal processing method. In addition, the accuracy and feasibility of results are verified. Cylindrical shells with ribs are basic structures which are used in underwater vehicles. By taking excitation forces results as an approximate input, a cylindrical shell whose two tips are simply supported is chosen as calculation model of a cabin of underwater vehicle, and the transient maximum and mean radiation noise of shells are calculated separately to estimate the steering engine's characteristics of noise sources. A non-stationary STFT signal processing method to evaluate transient radiation noise of steering engine is provided. © 2016, China Ship Scientific Research Center. All right reserved.
... The researchers then used the method of torque excitation and angle displacement excitation to study the torsional vibration problems of the drill string and found that it is more realistic to use the angle displacement excitation method to study the torsional vibration of a drill string. Caresta et al. (2013) predicted the local response following an impact or a shock loading. The assumption underlying this approach is that the duration of the impact is short enough that the reverberant field does not affect the contact force. ...
Article
Down-the-hole hammer (hereafter DTH) drilling is an air hammer drilling technique designed for drilling through bedrock and features a typical drill string length of 200 m or shorter due to its technical specifications. During DTH drilling of granite-like hard rocks, the impacts of the piston-bit-rock system cause the drill string to generate severe vibration and noise pollution. In addition, the rapid wear of the button bit and drill string significantly decreases the drilling efficiency. Based on a distributed parameter drill string model of a DTH, this paper studies the phenomenon of the drill string’s axial forced vibration with a periodic impacting force under DTH drilling in an innovative manner. With the focus of study on DTH button bit, the transient impact force on the button bit during the drilling of the piston-bit-rock system is determined, and the impact force is converted to a periodic excitation force function using polynomial fitting. Then, the periodic impulse is transformed into a harmonic series using Fourier transforms, and finally, the drill string vibration response under the harmonic excitation force series is determined. The results reveal that a periodic impulse can mainly be determined by the nature of the DTH drill string and rock and the impact frequency during drilling. Further evidence demonstrates that at least one frequency component of the impulse harmonic series will be equal to the modal frequencies of the drill string insofar as the condition is met; the coupling of the short drill string with the DTH may cause resonance at a specific hole depth, whose resonance regions are adjacent to but not continuous with the extension of the drill string. This work should serve as an important theoretical guide for designers in the dynamic design, modification, and use of a DTH drilling system.
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An improved method based on the Hybrid Finite Element-Statistical Energy Analysis (FE-SEA) method and quasi-steady state theory is proposed to predict the response of spacecraft structure during the process of pyrotechnics separation. Firstly, the amplitude–frequency value of shock load is obtained by using time-frequency conversion technology. Then, according to the frequency response characteristics of each part of the spacecraft structure, a more accurate hybrid FE-SEA model is established. The piecewise loading method is used to predict the response of the hybrid model. Finally, the time domain response results are reconstructed, and the shock response spectrum (SRS) is calculated. Based on the test system of simulating pyroshock, the shock experiment of spacecraft structure is conducted. The high frequency and high velocity character of pyroshock could be effectively simulated, and an accurate shock force function could be obtained through the experiment. This indicates that the numerical results are in line with the ones of the experiment. The SRS obtained from experiments and calculations have similar trends and amplitudes. This conclusion verifies the rationality and sufficient accuracy of the novel method in this paper. The novel method presented in this paper greatly improves the computational efficiency. At the same time, it provides theoretical guidance for shock response prediction of spacecraft structure by steady-state methods.
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The experimental study on far‐field pyroshock responses of carbon/glass/Kevlar‐epoxy composite panels are presented in this article. Bi‐Plate Technology is used to conduct all the experiments on different combination of carbon, E‐glass, and Kevlar composite panel parameters, with epoxy resin as matrix. The structural responses computed from the acceleration–time histories are analyzed. Low range of chamber pressure and projectiles of three different lengths are used to carry out the experiments so that the far‐field response of the test panel is ensured. PCB accelerometers and NI‐DAQ system are used to capture the accelerations of panel at selected locations. Among all the composite panels, the one which is of Kevlar‐epoxy laminate shows the least acceleration because the said material has high vibrational energy absorption rate. The glass‐epoxy laminate being higher mass rate shows the intermediate category and the carbon‐epoxy accelerates itself the most. Hence, these types of fibers may be utilized in appropriate areas according to their degree of acceleration to minimize the effect of the far‐field pyroshock response.
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Pyrotechnic devices have been widely utilized in various applications: spacecraft, launch vehicles, missiles, and aircraft as well as for stage separation, valve control, and booster separation. However, most pyrotechnic separators generate an intensive mechanical transient response called pyroshock, which can cause catastrophic failures in electronic equipment. In order to validate that the structure or equipment can withstand the generated shock level, pyroshock tests should be performed with properly simulated structural configurations and the shock sources. Most of the previous pyroshock simulators using mechanical excitation have been developed as shock table configurations; they can effectively apply the target shock levels to the test component. However, it is difficult to simulate the pyroshock source in practical structures. In this study, a miniature pyroshock simulator that can easily replace a pyrotechnic device and is adaptable onto the most practical structures was developed. A disk resonator is introduced to control the shock response by changing the first natural frequency of the disk resonator. To excite the disk resonator, we devised a launch device that effectively controls the impact velocity with easy reloading capability. Experiments for 27 different conditions were conducted to identify the control parameters for the shock levels. The developed simulator also showed high repeatability, and it is easy to prepare repeated experiments using the developed shock simulator. This device can easily generate the simulated point-source pyroshock for real structures such as an assembled spacecraft.
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In order to solve the failure of traditional methods in the response prediction for the complex spacecraft under the wide frequency shock load, this paper provides the FE-SEA (Finite Element-Statistical Energy Analysis) hybrid modeling technique to improve the virtual mode synthesis and simulation (VMSS). Taking the L-shape typical structure as an example, the research is developed through the numerical analysis and experiment verification. In the FE-SEA hybrid model of the typical structure, the two honeycomb boards which have a higher modal density are built as the SEA model, while the connection beam that has a larger stiffness is established as FE model. And then the hybrid model is computed with the VMSS code, giving the transient response results. A shock experiment for the typical structure is carried out to verify the correctness of the methodology above. The results indicate that the numerical results have the similar trend and magnitudes with the ones of the experiment in time domain, and the shock response spectrum (SRS) of the numerical results can realize the ±6 dB tolerance limit compared with the experiment results. This paper finds that the FE-SEA hybrid modeling techniques for the typical structure can effectively overcome the problem of the dynamic differences between the substructures under the excitation of shock load, and the combination of FE-SEA and VMSS has the ability to predict the shock responses of the typical structure accurately. The research methods and conclusions achieved in this paper are expected to further extend to the shock response calculation of the complex spacecraft structures.
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Numerous pyrotechnic devices are used in aerospace vehicles to separate structural subsystems, deploy appendages, or activate on-board operational subsystems. The state-of-the-art for pyroshock prediction, design and test verification has not yet reached the maturity of other environmental disciplines, due to the complex, high-frequency nature of pyroshocks. However, recent advances in the analysis and simulation of pyroshocks have led to a better understanding of this environment. This paper presents an overview of the development of characterization of pyroshock, various experimental tests and simulations, analytical and numerical simulation for pyroshock prediction, and protecting techniques.
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Pyroshocks are structural responses to transient excitation caused by the essential use of pyrotechnic devices in aerospace applications. In order to avoid damage in aerospace structures due to pyroshocks, tests are performed on earth prior to launching space modules. In these tests, explosive loads are often replaced by alternative excitation methods such as hammer pendulums or shakers simulating on earth the impact taking place in space. However, there does not yet exist an adequate excitation method satisfying all requirements of a fast, reliable, predictable and repeatable test setup. Whereas hammers are poorely controllable in terms of generating desired shock spectra, shakers show limitations in terms of the bandwidths of up to 10 kHz which are prescribed in the test specifications. The authors present a novel contactless and non-destructive excitation method for pyroshock test devices based on a mechatronic coupling by applying Lorentz forces to the carrying structure. For generating the corresponding magnetic field, the capacitor of a Resistor-Inductor-Capacitor RLC resonator circuit is initially charged and then discharged leading to high currents in the coil which is placed close to the carrying structure. Latter is then inducing a counter current in the aluminum structure which reacts with high multidirectional Lorentz forces. Any adjustments are done by tuning the properties of the circuit such as initial charge, capacitance and inductance. By connecting several different coils, frequency modulation and by splitting the currents more complex signals can be generated matching the natural frequencies of the structure. Almost all disadvantages of common excitation methods are eliminated by the proposed mechanism.
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The most widespread vibration measurement on musical instrument bodies is of the point mobility at the bridge. Analysis of such measurements is presented, with a view to assessing what range of information could feasibly be extracted from the corpus of data. Analysis approaches include (1) pole-residue extraction; (2) damping trend analysis based on time decay information; (3) statistical estimates based on SEA power-balance and variance theory. Comparative results are shown for some key quantities. Damping trends with frequency are shown to have unexpectedly different forms for violins and for guitars. Linear averaging to estimate the “direct field” component gives a simple and clear visualisation of any local resonance behaviour near the bridge, such as the “bridge hill”, and reveals some violins that show a double hill, while viols show only weak hills, and guitars none at all.
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This work is concerned with the characteristics of the impact force produced when two randomly vibrating elastic bodies collide with each other, or when a single randomly vibrating elastic body collides with a stop. The impact condition includes a non-linear spring, which may represent, for example, a Hertzian contact, and in the case of a single body, closed form approximate expressions are derived for the duration and magnitude of the impact force and for the maximum deceleration at the impact point. For the case of two impacting bodies, a set of algebraic equations are derived which can be solved numerically to yield the quantities of interest. The approach is applied to a beam impacting a stop, a plate impacting a stop, and to two impacting beams, and in each case a comparison is made with detailed numerical simulations. Aspects of the statistics of impact velocity are also considered, including the probability that the impact velocity will exceed a specified value within a certain time.
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In aerospace missions pyroshocks occur due to controlled explosions of ordnance devices enabling the functionality of space modules. These shocks result from deployment mechanisms or opening solar sails and can cause failures of electronic devices and structures. Thus, essential components for assuring the reliability of modules are pyroshock tests for the completion of which strict requirements by the aerospace administrations have to be met. One of them is the definition of a specific acceleration signal and, based on this, the Shock Response Spectrum (SRS) for each part.
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In this paper, the dynamic problem of a rigid body colliding with an elastic rod is studied in some detail. Different contact theories for modeling impact responses are compared with experimental measurements. Based on an idea originally presented by Sears for collisions of two rods with rounded ends, a boundary approach combining Hertzian contact law and St. Venant's elastodynamics is developed to describe longitudinal waves in rods. It is shown that this boundary approach agrees very well with experimental results. For the simulation of long-term dynamic behavior after impact, a traditional rigid-body approach is advantageous because the elastic vibration of the rod will decay fast due to the structural damping and the elastic rod then moves like a rigid body. Hence, for modeling longitudinal impacts, it is suggested that both elastodynamics and rigid-body dynamics are combined into a two-timescale model. The short time behavior of wave propagation due to impacts is modeled using elastodynamics, and the state of the rigid-body mode is transferred to the rigid-body approach as the initial condition for the motion. The long-term behavior after impact is then computed using the rigid-body approach.
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The first edition of Sound and Structural Vibration was written in the early 1980s. Since then, two major developments have taken place in the field of vibroacoustics. Powerful computational methods and procedures for the numerical analysis of structural vibration, acoustical fields and acoustical interactions between fluids and structures have been developed and these are now universally employed by researchers, consultants and industrial organisations. Advances in signal processing systems and algorithms, in transducers, and in structural materials and forms of construction, have facilitated the development of practical means of applying active and adaptive control systems to structures for the purposes of reducing or modifying structural vibration and the associated sound radiation and transmission. In this greatly expanded and extensively revised edition, the authors have retained most of the analytically based material that forms the pedagogical content of the first edition, and have expanded it to present the theoretical foundations of modern numerical analysis. Application of the latter is illustrated by examples that have been chosen to complement the analytical approaches to solving fairly simple problems of sound radiation, transmission and fluid-structural coupling that are presented in the first edition. The number of examples of experimental data that relate to the theoretical content, and illustrate important features of vibroacoustic interaction, has been augmented by the inclusion of a selection from the vast amount of material published during the past twenty five years. The final chapter on the active control of sound and vibration has no precursor in the first edition. * Covers theoretical approaches to modeling and analysis * Highly applicable to challenges in industry and academia * For engineering students to use throughout their career.
The prediction, by the statistical energy analysis (SEA) method, of transient vibration envelopes for coupled systems is investigated. The relation between the time-varying energy transferred between two coupled subsystems and time-varying energies of the subsystems is studied numerically and experimentally. These studies indicate that time-varying energy transmitted between two subsystems is related to the subsystem energies by an apparent time-varying coupling loss factor. It is shown that the apparent coupling loss factor approaches the asymptotic (or steady-state) coupling loss factor as response energies and transferred energies are integrated over progressively larger times.
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This paper is concerned with the ensemble statistics of the energy density of a random system subjected to a harmonic point load. Both the mean and variance of the reverberant energy density (i.e., the total response minus the direct field) are investigated. It is shown that the ensemble average of the reverberant energy density is not spatially homogeneous, but rather the value at the drive point is between two and three times the spatially averaged value, depending on the modal overlap factor. This result is closely analogous to established results regarding the case of transient excitation. Expressions are also derived for the relative variance of the reverberant energy density both remote from the drive point and at the drive point, and a number of anomalies are found in existing results. A comparison is made with simulation results for a randomized plate, and this comparison highlights the importance of the ensemble size considered in the simulations. The present analysis is based on a random point process model of the system natural frequencies, and both Gaussian orthogonal ensemble (GOE) statistics and Poisson statistics are considered.
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Results are presented giving values of the phase velocities and the relative magnitudes of the components of displacement for all possible free waves in the wall of a thin, elastic, cylindrical shell. Three classes of waves are identified and their natures are discussed as frequency is varied continuously. The vibrations are interpreted not only as standing waves and waves progressing the axial direction, but also as fully free waves traveling in a helical direction in the wall of the cylinder.
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A new analysis method has been developed to solve the contact problems of a thin beam impacting against a stop. The motivation for this research came from impact failure problems frequently found in thin plate type valves used in small compressors. The developed procedure is believed to provide, for the first time, a complete analysis method for this kind of problem. The procedure has been developed in a general form so that it can be utilized for impact problems with any general stop geometry. (C) 1996 Academic Press Limited
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This paper presents the free vibrational characteristics of isotropic coupled conical–cylindrical shells. The equations of motion for the cylindrical and conical shells are solved using two different methods. A wave solution is used to describe the displacements of the cylindrical shell, while the displacements of the conical sections are solved using a power series solution. Both Donnell–Mushtari and Flügge equations of motion are used and the limitations associated with each thin shell theory are discussed. Natural frequencies are presented for different boundary conditions. The effect of the boundary conditions and the influence of the semi-vertex cone angle are described. The results from the theoretical model presented here are compared with those obtained by previous researchers and from a finite element model.
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The modelling of impacted structures may have a high numerical cost. For low velocity impact problem, single degree-of-freedom models may be used efficiently. Nevertheless, sometimes, these models are not suitable to describe the dynamic behaviour of the structure. This paper presents a new model of impacted structures which may be viewed as an extension of the single degree-of-freedom existing models: it allows for the dynamic behaviour of a structure and the numerical cost is low. The fundamental elements of this model are single degree-of-freedom systems called “anti-oscillators”: the natural frequencies of these single degree-of-freedom systems correspond to the antiresonant frequencies of the structure. The applications given in this paper show that only a small number of anti-oscillators are required for accurate simulations of an impact event.
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Considered are vibrations of elastic systems under the action of external forces which represent a space-time broadband random process. On the basis of the asymptotic method, advanced by the author, and of estimates for the density of natural frequencies of shells, integral estimates for displacements and stresses are proposed which occur in elastic systems. At the basis of the method advanced there lies the replacement of summation over separate natural modes of free vibrations by integration over a certain range of frequencies (or wave numbers). The question concerning limitations of this method is discussed. Investigated is the influence of the characteristics of the loading of the type of damping as well as of the type of boundary conditions on mean squares and spectral densities of displacements and stresses.
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The dynamic response of a thick plate to distributed pressure loading on its surface is obtained by superposing solutions obtained for the half-space which were reported by the authors in reference [1]. In order to enforce a traction-free plate surface, superpositions of both normal and shear load solutions are normally required. An algorithm was developed where superpositions of normal load solutions for the half-space are used in such a way that shear stresses are also removed. Several examples are given, and the three-dimensional result for a uniformly distributed load case is compared, in the limit, with a one-dimensional solution to verify partially the correctness of the approach.
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The finite element method is used to predict the dynamic behaviour of circular cylindrical shells in free vibrations. A suitable shape function for the circumferential displacement distribution has been proposed. This reduces the three-dimensional character of the problem to a two-dimensional one. The simultaneous iteration method to determine the eigen-frequencies and eigenvectors is utilised for solving the eigenvalue problem. The accuracy of the method has been checked by verifying the results of known cases. Finally an experimental shell structure containing elastic rings welded at the ends has also been analysed and the experimental results compared with the theoretical ones.
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Flow-induced vibration in heat exchanger tubes can result in fretting wear at the baffle supports and subsequent tube failure. As one step in correlating the random flow excitation to the rate of fretting wear, this paper presents a dynamic finite element technique for predicting the motions and baffle contact forces of a single heat exchanger tube. Using a modal superposition approach, the modal equations of motion are generated and numerically integrated. The predicted results are compared with experimental data for both planar and spatial vibration of harmonically-excited cantilevered beams with a clearance support at the free end.
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Although pyrotechnics have successfully accomplished many critical mechanical spacecraft functions, such as ignition, severance, jettisoning and valving (excluding propulsion), failures continue to occur. Provided is a listing of 84 failures of pyrotechnic hardware with completed design over a 23-year period, compiled informally by experts from every NASA Center, as well as the Air Force Space Division and the Naval Surface Warfare Center. Analyses are presented as to when and where these failures occurred, their technical source or cause, followed by the reasons why and how these kinds of failures persist. The major contributor is a fundamental lack of understanding of the functional mechanisms of pyrotechnic devices and systems, followed by not recognizing pyrotechnics as an engineering technology, insufficient manpower with hands-on experience, too few test facilities, and inadequate guidelines and specifications for design, development, qualification and acceptance. Recommendations are made on both a managerial and technical basis to prevent failures, increase reliability, improve existing and future designs, and develop the technology to meet future requirements.
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This analysis is concerned with the derivation of a "diffuse field" reciprocity relationship between the diffuse field excitation of a connection to a structural or acoustic subsystem and the radiation impedance of the connection. Such a relationship has been derived previously for connections described by a single degree of freedom. In the present work it is shown that the diffuse-field reciprocity relationship also arises when describing the ensemble average response of connections to structural or acoustic subsystems with uncertain boundaries. Furthermore, it is shown that the existing diffuse-field reciprocity relationship can be extended to encompass connections that possess an arbitrary number of degrees of freedom. The present work has application to (i) the calculation of the diffuse field response of structural-acoustic systems modeled by Finite Elements, Boundary Elements, and Infinite Elements; (ii) the general calculation of the Coupling Loss Factors employed in Statistical Energy Analysis (SEA); and (iii) the derivation of an alternative analysis method for describing the dynamic interactions of coupled subsystems with uncertain boundaries (a generalized "boundary" approach to SEA).
Predicting mechanical shock transmission
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  • K Lee
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Free vibrational characteristics of isotropic coupled cylindrical-conical shells Please cite this article as: Transient response of structures with uncertain properties to nonlinear shock loading://dx.doi.org/10.1016/j.jsv.2013.06.014i M
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Pyroshock Test Criteria
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M.G. Ryschkewitsch, Pyroshock Test Criteria, NASA, TN D-3010, 2011.
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  • M Heckl
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