1,621 research outputs found
Testing of a Composite Conical-Cylindrical Shell
No full textLaunch-vehicle shell structures, which can be comprised of both cylindrical and conical sections, are known to be susceptible to buckling due to their large radius-to-thickness ratios. The advancements in composite manufacturing and numerical methods have enabled designers to consider more nontraditional shapes, such as connecting the conical and cylindrical sections with a toroidal transition to create a single-piece conical-cylindrical shell. This single-piece construction eliminates the need for a heavy interface ring between sections and has the potential to save mass. To better understand the buckling behavior, a composite conical-cylindrical shell was designed, fabricated, and tested. Prior to test, a finite element model that included thickness variations and radial imperfections was created. The test article buckled elastically at 251.8 kN, approximately 8.8% higher than the predicted buckling load of 231.4 kN Continued research in conical-cylindrical structures has the potential to expand the design space for launch-vehicle structures and lead to improved designs and reduced weight
Experimental validation of the buckling behavior of unreinforced and reinforced composite conical-cylindrical shells for launch-vehicles
No full textConical-cylindrical shells are common geometries in launch-vehicle structures as stage adapters and payload adapters, and they are susceptible to buckling due to their large radius-to-thickness ratios. Buckling design guidance is available but it is limited for conical and cylindrical shells. There is no available buckling design guidance for conical-cylindrical shells. This paper presents the validation of two finite element models used to successfully predict the buckling behavior of a composite conical-cylindrical shell with and without reinforcement tested in two separate campaigns. The laminate design for the first test campaign consisted of a quasi-isotropic layup. For the second test campaign, additional composite plies were applied to reinforce the transition region of the original laminate. The work presented demonstrates the ability to predict the buckling behavior of a composite conical-cylindrical shells with two different designs, which may aid in creating buckling design guidance for conical-cylindrical shells. Additionally, this paper shows that there is no appreciable benefit to adding reinforcement to the transition region if the intent is to increase the buckling load, due to the fact reinforcement brings increased buckling imperfection sensitivity to the shell
Analysis and Testing of a Launch-Vehicle-Like Composite Conical–Cylindrical Shell
No full textLaunch-vehicle shell structures, which can be composed of both cylindrical and conical sections, are known to be susceptible to buckling due to their large radius-to-thickness ratios. Advancements in composite manufacturing and numerical methods have enabled designers to consider more nontraditional shapes, such as connecting the conical and cylindrical sections with a toroidal transition to create a single-piece conical-cylindrical shell. This single-piece construction eliminates the need for a stiff, heavy interface ring between sections and has the potential to reduce mass. To better understand the buckling behavior of a composite conical-cylindrical shell, a laboratory-scale article was designed, fabricated, and tested. Before the test, a finite element model that included thickness variations and radial imperfections was created. The test article buckled elastically at 251.8 kN, approximately 8.8% higher than the predicted buckling load of 231.4 kN. Because the test article buckled elastically, the buckling test was repeated. The buckling load measured from the second test was within 1% of that from the first test. Continued research on conical-cylindrical structures has the potential to expand the design space for launch-vehicle structures and lead to improved designs and reduced mass
Scaling Methodology for Buckling of Sandwich Composite Cylindrical Structures
No full textThe study of the buckling behavior of large shell structures through full-size tests can be complex and expensive. Therefore, scaled structures are often preferred to investigate the buckling behavior efficiently. However, it can be difficult to design scaled structures that are representative of the full-scale structures. Herein, an analytical scaling methodology for compression-loaded sandwich composite cylinders based on the nondimensionalization of the buckling equations is presented. The methodology is used to develop scaled configurations that show a similar buckling response. Both the baseline and the scaled configurations are verified by finite-element analysis. Limitations of the methodology are discussed and are a result of neglecting the flexural anisotropy and the transverse shear compliance
Scaling methodology for buckling of composite conical shells in axial compression
No full textConical shells are commonly used as structural components for launch vehicles. The axial compression experienced during launch is one of the sizing load cases, because it can lead to loss of structural stability. Because experimentally testing these full-scale structures is cumbersome and expensive, it is expedient to understand how reduced-scale shells can be designed such that their buckling behavior is representative of the full-scale shell behavior. An analytical, sequential scaling methodology is developed based on the nondimensional governing equations for composite conical shells with a symmetric, balanced layup and negligible flexural anisotropy. Linear and nonlinear finite element analyses characterizing the buckling behavior of the different size shells yielded comparable results in terms of buckling load, meridional displacement, and buckling mode. The inclusion of geometric imperfections affects the prediction accuracy, but not to the extent that the methodology is no longer valid.Aerospace Structures & Computational Mechanic
Variable-energy positron beam study of arsenic diffusion in poly-silicon
No full textThe positron beam technique is shown to be a sensitive indicator of the presence of arsenic within the grain boundaries of poly-silicon. Variable-energy positron beam and secondary-ion mass spectrometry studies have been performed on As+-implanted pre-amorphized Si samples as a function of dose and rapid thermal anneal temperature. Positron trapping within negatively-charged grain boundaries of the recrystallized poly-Si is observed, resulting in a similar to 2% elevation in the Doppler-broadening S lineshape parameter value. Infusion of As+-ions into the grain boundaries passivates the charge and reduces their specific positron-trapping rate.PT: J; CR: AERS GC, 1991, POSITRON BEAMS SOLIE, P162 ASOKAKUMAR P, 1993, NUCL INSTRUM METH B, V74, P89 BOUSETTA A, 1991, NUCL INSTRUM METH B, V55, P565 DANNEFAER S, 1987, PHYS STATUS SOLIDI A, V102, P481 DANNEFAER S, 1989, J APPL PHYS, V66, P3526 DLUBEK G, 1987, PHYS STATUS SOLIDI A, V102, P443 FLYNN CP, 1992, POINT DEFECTS DIFFUS GANIN E, 1989, APPL PHYS LETT, V54, P2127 HAKVOORT RA, 1992, MATER SCI FORUM, V105, P1391 HAKVOORT RA, 1993, THESIS DELFT U TECHN JACKMAN TE, 1989, APPL PHYS A-SOLID, V49, P335 KALISH R, 1984, APPL PHYS LETT, V44, P107 KEINONEN J, 1988, PHYS REV B, V37, P8269 LEO PH, 1981, PHYS STATUS SOLIDI B, V108, K145 LOMBARDO S, 1994, J APPL PHYS, V75, P345 MAKINEN J, 1990, J APPL PHYS, V67, P990 MITCHELL IV, 1991, POSITRON BEAMS SOLID, P121 NASU H, 1987, YOGYO-KYOKAI-SHI, V95, P5 NIELSEN B, 1987, APPL PHYS LETT, V51, P1022 NIELSEN B, 1991, PHYS REV B, V44, P1812 SCHULTZ PJ, 1988, PHYS REV LETT, V61, P187 SCHULTZ PJ, 1988, REV MOD PHYS, V60, P701 SEIDEL TE, 1991, NUCL INSTRUM METH B, V55, P17 SIMPSON PJ, 1991, POSITRON BEAMS SOLID, P125 TAKAI M, 1989, NUCL INSTRUM METH B, V39, P352 TANDBERG E, 1989, CAN J PHYS, V67, P275 VANDERDRIFT A, 1967, PHILIPS RES REP, V22, P267; NR: 27; TC: 0; J9: APPL SURF SCI; PG: 6; GA: QD950Source type: Electronic(1
Armadilloniscus ninae Schultz 1984
No full textArmadilloniscus ninae Schultz, 1984 Figs 1, 2F, 13–14 Armadilloniscus ninae Schultz, 1984: 4, figs 1–2. Material examined COLOMBIA – Bolívar, Cartagena de Indias, Islas del Rosario, Isla Grande • 1 ♂ (parts in micropreparations); Paraíso Secreto; 10°10′15.9″ N, 75°44′38.8″ W; 24 Nov. 2017; C.M. López- Orozco leg.; CUDC-CRU 212 • 1 ♂, 4 ♀♀; same collection data as for preceding; CUDC-CRU 214 • 21 ♂♂, 61 ♀♀; same locality as for preceding; 4 Apr. 2018; C.M. López-Orozco, R. Borja-Arrieta and K. Meza leg.; CUDC-CRU 213 • 3 ♀♀; same locality as for preceding; 6 Sep. 2017; C.M. López- Orozco leg.; CUDC-CRU 215 • 1 ♂, 6 ♀♀ (one with parts in micropreparations); Caño Ratón; 10°10′33.4″ N, 75°44′52.4″ W; 24 Nov. 2017; C.M. López-Orozco leg.; CUDC-CRU 216 • 5 ♀♀; 10°10′44.91″ N, 75°44′53.01″ W; same collection data as for preceding; CUDC-CRU 217. CUBA – Cayo Piedras del Norte, Varadero • 2 ♂♂, 2 ♀♀; 8 Aug. 1985; A. Poggesi leg.; MZUF 1824. Redescription BODY. Color pale brown; cephalon, antennae, epimera of pereonites 1–7, epimera of pleonites 1–5 and uropod protopods more pigmented; pereon and pleon with median and paramedian region more depigmented (Fig. 2F). Body elongated and elliptical-shaped (Fig. 13A). Dorsal surface bearing elongated scale-setae (Fig. 13B). Cephalon and pereon covered with small tubercles (Fig. 13A, C–D): cephalon bearing six tubercles in two rows, anterior row with two and posterior row with four; pereonites 1–7 with one row of 8 tubercles. CEPHALON. Lateral lobes well developed and directed outwards, median lobe triangular, slightly surpassing distal margin of lateral lobes, frontal and suprantennal lines absent; eyes consisting of 5 ommatidia (Fig. 13C–D). PLEON. Outline continuous with that of pereonite 7, epimera of pleonites 3–5 rectangular (Fig. 13A, E). Telson (Fig. 13E) triangular, wider than long, lateral margins almost straight, broadly rounded apex. ANTENNULA. Composed of two articles, second article bearing many lateral setae, distal margin bearing one flagellar seta and two aesthetascs (Fig. 13F). ANTENNA. When extended posteriorly slightly surpassing pereonite 1, flagellum of four articles (Fig. 13G). BUCCAL PIECES. As in Armadilloniscus luisi sp. nov. UROPOD. Protopod enlarged with distal margin slightly rounded, exopod not surpassing protopod, endopod longer than exopod (Fig. 13E). PEREOPODS. Pereopods 1–7 stout, merus to propodus bearing sparse setae on sternal margin, carpus 1 with strong distal seta bearing long sensilla, dactylus with elongated and digitform ungual seta, dactylar seta elongated, apically cleft and plumose. Male PEREOPODS 1 AND 7. Without any sexual modifications (Fig. 14A–B). GENITAL PAPILLA. Ventral shield stout triangular, papilla rounded at apex, bearing small setae (Fig. 14C). PLEOPODS. Pleopod 1 (Fig. 14D) exopod ovoid, wider than long; endopod stout, three times as long as exopod, apical portion slightly bent inwards. Pleopod 2 (Fig. 14E) exopod ovoid, wider than long; endopod with flagelliform distal article. Exopods of pleopods 3–5 as in Fig. 14F–H. Remarks Schultz (1984) described A. ninae from San Pedro beach, Ambergris Cay, Belize. Comparing Shultz’s description with the specimens examined here, it was possible to observe that almost all characters mentioned, including the pale dorsal pigmentation, are quite similar. However, Schultz (1984) mentioned that A. ninae has eyes composed of 14 ommatidia and antennula with three articles, and herein the specimens showed the eyes composed of 5 ommatidia and antennula of two articles. Most probably, the author misinterpreted the composition of the eyes of this species, since the illustrations of the cephalon clearly show a smaller number. The same statement can be applied to the antennula. In general, within Oniscidea, the composition of the antennula does not vary within the genera, with just few exceptions (see Schmidt 2002, 2003). Moreover, analyzing other representatives of Armadilloniscus, it is possible to observe that the antennula is always composed of two articles (see Taiti & Ferrara 1989; Kwon & Wang 1996). Therefore, we identify our specimens as A. ninae. Distribution This species was previously recorded only from San Pedro beach, Ambergris Cay, Belize (Schultz 1984). First record for Colombia and Cuba.Published as part of López-Orozco, Carlos Mario, Carpio-Díaz, Yesenia M., Borja-Arrieta, Ricardo, Navas-S, Gabriel R., Campos-Filho, Ivanklin Soares, Taiti, Stefano, Mateos, Mariana, Olazaran, Alexandra, Caballero, Isabel C., Jotty, Karick, Gómez-Estrada, Harold & Hurtado, Luis A., 2022, A glimpse into a remarkable unknown diversity of oniscideans along the Caribbean coasts revealed on a tiny island, pp. 1-50 in European Journal of Taxonomy 793 on pages 26-29, DOI: 10.5852/ejt.2022.793.1643, http://zenodo.org/record/603789
Analysis and validation of a scaled, launch-vehicle-like composite cylinder under axial compression
No full textLaunch vehicle structures, such as payload adapters and interstages, are increasingly designed and constructed using composite materials due to their high stiffness- and strength-to-weight ratios. Therefore, it is important to develop a validated finite element modeling methodology for designing and analyzing composite launch-vehicle shell structures. This can be achieved, in part, by correlating high-fidelity numerical models with test data. Buckling is often an important failure mode for cylindrical shells, and the buckling response of such structures is also often quite sensitive to imperfections in geometry and loading. Hence, it is crucial to understand the model parameters and details required to accurately predict the buckling load and behavior of composite cylindrical shells, especially if the shell is buckling critical. The inclusion of as-built features, such as radial imperfections, thickness variations, and loading imperfections can help improve the correlation between test and analysis. To demonstrate such an approach, a validated modeling methodology that was used to predict the buckling behavior of a scaled component for a launch-vehicle-like structure is presented, and results from the model are compared with experimental results. The modeling approach presented herein was used to successfully predict the buckling behavior.Aerospace Structures & Computational Mechanic
Toward A New, Musical Paradigm of Place: The Port River Symphonic Of Chester Schultz
No full textIn privileging music as a focus for applied ecology, the goal of this essay is to deepen perspectives on the musical representation of land in an age of complex environmental challenge. As the metaphor driving public narration of environmental crises, the notion of Earth as our home—signified by the prefix “eco”—brings with it a critical expectation for the musical academy to retreat from bland talk about a “sense of place.” Based on the premise that damaged ecologies are a matter of concern to many people, Indigenous and Settler; and building on the late Val Plumwood’s theory of “shadow” or “denied” places (Australian Humanities Review 44, 2008), the author introduces Within Our Reach: A Symphony of the Port River Soundscapes by anti-elitist South Australian composer Chester Schultz (b. 1945). Inspired by the tradition of R. Murray Schafer’s performances for outdoor sites, Schultz predicated this niche symphony on the noise-polluting defoliation of Adelaide’s “wetland wonder,” the Old Port Reach. Presented as a series of narrative soundscapes, the symphony harnesses the power of music, including popular genres, to engender a sense of local “belonging” to the Port. In an ecological subtext an Indigenous Elder sings in the re-awakening language of the Kaurna people who, in 1890, were evicted from their “nourishing terrain” (terminology after Rose, 1996) by the CSR Sugar Refinery. Schultz’s ethical musical representation of local oral, natural and industrial history generates a benchmark opus for what shadow place composition might sound like in the modern global city
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