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Viewing 70801 to 70830 of 103874
1988-04-01
Technical Paper
880871
Toru Matsumoto
Many factors affect the susceptibility of steel to hydrogen-induced delayed brittle failure. The most important factor is the strength level of the specific steel alloy. Other factors are the applied load and hydrogen control. The susceptibility of high-strength steels to this type of failure can be determined with a sustained load test using notched round-bar tensile specimens or Douglas Aircraft Company stress rings. This paper describes the Douglas method of embrittle­ment testing(ASTM F519, Type 2a) for plating processes and contains information on how the stress rings were used to rate the relative embrittling tendencies of various plating processes. Stress rings and four different-sized loading bars were used to determine the susceptibility of electrolytic tank plating processes (cadmium, chromium and sulfamate nickel) and electrolytic brush plating processes (cadmium and sulfamate nickel) to hydrogen embrittlement under sustained load.
1988-04-01
Technical Paper
880872
Anthony F. Klarman, James A. Heist
Abstract A freeze crystallization process is being demonstrated for treating a wide variety of wastes generated in the plating and other industrial shops at the Norfolk, VA Naval Aviation Depot (NAD). As envisioned the freeze process will treat various rinses, plating baths, and cleaning solutions for recycle at the NAD, greatly reducing and even eliminating discharges to the industrial waste treatment plant. The manner in which the freeze process will be incorporated to do this includes: remove water with sufficient purity for recycle as rinse water and in bath makeup; concentrate the chemicals in rinse waters for recycle to plating baths; concentrate pickling wastes to recycle the concentrated acid while precipitating the dissolved metals for removal as innocuous sludge; concentrate paint strippers and solvents in rinses and other contaminated waters, separating useful organics from residual aqueous concentrates.
1988-04-01
Technical Paper
880874
Stanley J. Cieslak, Jerry T. Whicker
Environmental regulations are tightening worker exposure limits and disposal options for airlines who chemically strip and repaint their fleets. An alternative is to operate a polished aluminum aircraft fleet. The authors present an explanation of the grades of alclad aluminum fuselage skins used by commercial aircraft manufacturers and offer instructions on how to polish the unpainted alclad aluminum in order to operate the aircraft in the polished look. All fuselages on aircraft built by Boeing, Douglas, Lockheed, and the new EMBRAER Brasilia, were assembled using premium grade polished alclad aluminum. As a result, painted versions of aircraft built by the airframers have the capability to be stripped, polished and put in service as a polished aluminum aircraft.
1988-04-01
Technical Paper
880910
Shin-ichi Ishiyama, Moriyuki Imai, Shin-ichi Maruyama, Hironobu Ido, Noboru Sugiura, Shinji Suzuki
Noise level prediction computer code ACOUST/BOOM has been developed to analyze the sound pressure radiated by a vibrating structure and calculate the acoustic resonance of the field. The program is based on the numerical analysis computation of a sound wave equation in a three-dimensional field using the boundary element method. The boundary element method uses simplified input data, reduces computation time and cost, and produces highly accurate results. Applications has been performed on sound radiation analysis for engine oil pan, engine head cover and horn type speaker and also on the acoustic analysis for sedan compartment models, which confirmed the accuracy and the versatility of the program.
1988-04-01
Technical Paper
880908
Daniel S. Drucker, Maurice Lou, Semyung Wang, Kenneth A. Kline
Reduced basis techniques and the method of mode-acceleration are applied to transient analysis of simple beam and truss structures. It is noted that the method of mode-acceleration effectively recovers the first Ritz vector used in Ritz procedures. The theoretical basis for Lanczos algorithms that generate Ritz vectors is explained. Both mode-acceleration and Ritz procedures are found, generally, to be more accurate than mode-displacement in calculation of transient shear stresses, moments and normal stresses. Reanalysis using Ritz vectors is discussed following Kitis and Pilkey [9] and Noor and Lowder [10].
1988-04-01
Technical Paper
880907
Jianhong Zhang, William J. Anderson
Several automated redesign methods have been proposed for static linear structures. Those methods that use approximate modes incorporate different length scales into the basis vectors, including the overall geometric scale, the loading scale and possibly vibration wavelength scales. The proposed approach uses Ritz vectors derived from pseudo-loads acting on linked-design-variable regions and hence bring a “redesign scale” into the set of base vectors. The results look promising for cases of redesign where substantial changes are required in regional parameters. As might be expected, “pseudo-force modes” due to loads at a regional length scale are best able to predict response of a structure with changes on that length scale. To date only the “forward” problem has been solved, and the fully automated redesign using nonlinear mathematical programming is underway.
1988-04-01
Technical Paper
880906
Joseph Whitesell
Abstract Due to its iterative nature, engineering design typically involves the analysis of several design candidates before a final design decision can be made. Since the number of design candidates that can be considered is often limited by the availability of computational resources, design reanalysis methods have been proposed in order to extend those resources. These methods attempt to reduce the cost of a design reanalysis by utilizing information derived from a previous analysis. In the past these methods have had only limited success since they have been able to cope only with relatively small design changes. In this paper an application of rational approximation theory is made which overcomes this problem. The basic approach is to treat the design change as a numerical homotopy problem and apply a rational approximation method to evaluate the solution. In order to guarantee robustness a new rational approximation method is used which has improved numerical properties.
1988-04-01
Technical Paper
880905
Walter D. Pilkey, Bo Ping Wang
A unified formalization for reanalysis of modified structures is discussed in this paper. Both exact and approximate reanalysis are viewed as a form of Ritz analysis. These formulations are applicable to static, steady state and free vibration reanalysis problems.
1988-04-01
Technical Paper
880904
T. R. Grimm, D. M. Johnson, J. E. Kajander, G. L. Viegelahn
The crush characteristics of thin-walled flanged columns with circular and octagonal cross-sections were studied. Specimens tested were fabricated by spot welding together along the flanges, two separate sections of formed 1018 CR steel sheet metal. The flange width was varied for each of the three different thicknesses considered. Loading was limited to pseudo-static uniaxial compression for all specimens. Triggering devices consisting of drilled holes and notches cut out of the flanges were investigated. The holes were found to increase the structural effectiveness of the flanged cylinders, whereas the notches caused a decrease in absorbed energy. The most promising members however were the flanged octagonal columns with the minimum flange width. Larger flange sizes were found to cause global buckling modes and loss of structural effectiveness.
1988-04-01
Technical Paper
880902
R. A. McEachern, L. G. Watson, P. B. Hertz
In this paper the authors compare the experimental load response of several welded aluminum structures with the response of equivalent finite element models. The samples tested represent frame components of NEXUS, a light weight research vehicle. The initial elastic response of thin walled specimens was accurately predicted using quadrilateral shell finite element models. Beam or shell element models were used to predict the elastic response of thick walled tubular samples. The material used to construct all of the samples was 0061-T6 aluminum. Tungsten inert gas welding was used to join the aluminum components. The heat of welding produced a heat affected zone with a large material property variation. The resultant difficulties with the accurate modelling of yield and post yield behaviour are discussed.
1988-04-01
Technical Paper
880901
T. R. Grimm, S. E. Minarecioglu, G. L. Viegelahn
The large deformation crush behavior of axially loaded thin-walled circular columns was studied using an experimental approach. Many specimens were crushed by uniaxial quasi-static loads to establish a data base. The maximum load capacity, wavelength of buckled folds, mode shapes and post-mean buckling load magnitude were determined for many specimens. These values were then expressed in terms of cross-sectional geometry parameters, tube length, and material properties. Based on the results obtained, empirical design formulations were developed for predicting the crush characteristics, including mode of collapse, of circular columns.
1988-04-01
Technical Paper
880903
John F. Carney, John R. Veillette, Malcolm H. Ray
Laterally loaded metallic tubes possess desirable energy dissipation properties which have led to their use as impact attenuation devices in highway safety applications. These attenuation devices are composed of arrays of metallic tubes in which energy is dissipated by inelastically deforming mild steel cylinders. This paper describes the energy dissipation characteristics of braced and unbraced tubes and tubular clusters when subjected to quasi-static and impact loadings causing large deformations. The effects of strain rate, stress waves and collapse mode on the impact response and energy dissipation characteristics are described and results of full-scale crash tests for the crash cushion application are shown. The large-scale deformation of metallic tubes is shown to be an effective method for dissipating the energy associated with an impact event.
1988-04-01
Technical Paper
880898
Gene H. McNay
In the automotive crash event, the bending and folding of the metal structural members is the method whereby impact energy is absorbed. Lately, the development of supercomputers, such as the CRAY-XMP/24, and non-linear finite element codes, such as DYM-3D, have made it possible to model this bending and folding in detail. In order to verify these capabilities, an example problem of the axial crush of a rectangular steel tube is analyzed experimentally and numerically. Quasistatic conditions are chosen over dynamic conditions because, quasistatic experiments are more repeatable than are dynamic experiments and quasistatic modelling results are less ambiguous to interpret than are dynamic test results. This paper describes, the experimental program and results, and the numerical models and the results from these models when analyzed with DYNA-3D. The predicted peak force, mean force level and the energy absorbed are compared against an average of the experimental data.
1988-04-01
Technical Paper
880900
M. M. Sadeghi, H. Mellander
This paper describes the method of incorporating a three point seat belt for the rear centre seat passenger in an Estate car. The necessary analyses were carried out to determine the load path through the belt, seat structure and the floor, highlighting the area to be redesigned. It was assumed that the 2/3 folding seat back would be supported in its upright position by the floor and the vehicle inner wall only. The support from the 1/3 seat back was ignored. The specifications are based on a very severe front crash and therefore represent the worst case. The design, which is in both steel and composite material versions, complies with forward and rearward accelerations (16000N belt load) concerning the passenger, as well as 100kg of luggage. It also complies with a severe forward deceleration (21500N) related to the centre seat passenger. In the case of the 16000N, the deformation was limited to 100mm, whilst for the 21500N the requirement was ‘no material separation’.
1988-04-01
Technical Paper
880896
L. Todorovska-Azievska, D. Kecman
The paper reviews the main results of the theoretical and experimental analysis of the multiaxial collapse modes in rectangular section tubes used in bus and other vehicle structures. The tubes were tested quasistatically to collapse under the uniaxial bending, biaxial bending, pure torsion, torsion combined with uniaxial bending and torsion combined with biaxial bending. Hinge characteristics under multiaxial loading were simulated by a combination of the uniaxial collapse data. The analytical model compared well with the experiments.
1988-04-01
Technical Paper
880897
Thomas Scharnhorst
Numerical calculations with high predictability for the analysis of deformation and nonlinear energy management of car structures during frontal impact are an essential tool when decisisons are needed regarding the structural design of car bodies in white during the early stages of car development without the existence of prototypes. Graphics-aided preprocessing allows the modelling of three-dimensional car structures with about 10,000 finite elements. The numerical calculations are based on the physics of crash metal-forming. The entire analysis is divided into about 40,000 simulated time steps. Supercomputers have to be used so as to enable a single crash simulation to be run overnight, whereas scalar computers would need many days. The results of crash simulation are postprocessed by way of coloured computer graphics which make it possible to assess the deformation of the car structure and to take special engineering results into account.
1988-04-01
Technical Paper
880895
T. Weirzbicki, W. Abramowicz
SUMMARY A new solution technique is proposed for a class of problems involving deep plastic collapse and large shape distortion of thin shells which is based on the concept of special finite elements with built-in knowledge on local folding mechanisms. These elements are characterized by floating, rather than fixed, boundaries and continuity of slopes of the displacement field. Typically, eighteen special elements would accurately represent the complex deformation pattern of a single corner or fold line. The condition of slope continuity further reduces the number of free parameters to three (3)! The new procedure is illustrated by example of progressively crushing a rigid-plastic box column.
1988-04-01
Technical Paper
880894
H. F. Mahmood, A. Paluszny, X. Tang
Abstract The structural analysis for crashworthiness, presented in this paper, consists of three parts: thin-walled element modeling, stiffness formulation and numerical solution. In thin-walled elements the stresses rarely reach the yield level and the element's force-deformation relationship is usually controlled by local buckling and subsequent collapse of the section. This relationship can be generally divided into four regimes: linear, post-buckling, crippling and deep collapse. In the post buckling regime only a part of the section contributes to its load carrying capacity and it is this effective part that is being used to calculate the section properties. In the deep collapse regime the stiffness is calculated by considering an appropriate mechanism of section collapse. The element stiffness is then assembled into the structural stiffness matrix.
1988-04-01
Technical Paper
880893
Ted Belytschko
The evolution of computational methods for crashworthiness and related fields is described and linked with the decreasing cost of computational resources and with improvements in computational methodologies. The latter includes more effective time integration procedures and more efficient elements. Some recent developments in methodologies and future trends are also summarized. These include multi-time step integration (or subcycling), further improvements in elements, adaptive meshes, and the exploitation of parallel computers.
1988-04-01
Technical Paper
880911
L. I. Nagy, M. Dede, G. C. Campbell, S. G. Borders
Acoustic analysis of a Light Truck cab in the frequency range of 0 to 140 Hz was performed by utilizing an analytical method combined with experimental data. The structural and acoustic modes of the cab were determined by utilizing the MSC/NASTRAN dynamic analysis capability. Chassis, powertrain, and suspension components were simulated with the experimental modal data, acquired from dynamic testing of an actual vehicle. Triaxial transfer functions were obtained at all six cab-mount locations due to shaker excitation at the pinion nose and the 4 spindles, as well as neutral engine run-ups. The overall system model was constructed by combining analytical structural and acoustic modes with the experimental modal data using the modal synthesis technique and an in-house developed computer code called MOTRAN. The acoustic mode shapes, response at critical cab-structure locations, and interior sound level at the driver's ear were obtained.
1988-04-01
Technical Paper
880912
Mark S. Shephard
This paper discusses recent developments of finite element modeling techniques that, when properly combined, hold the promise of automating the finite element modeling process. The areas considered are fully automatic mesh generation, geometric modeling needs of automated finite element modeling, and adaptive finite element analysis. Finally, consideration is given to how the user can expect to see finite element modeling evolve from its current interactive mode of operation to fully automatic operation.
1988-04-01
Technical Paper
880914
M. E. Botkin, M. J. Fiedler
Shape optimization of structural components is rapidly developing into a usable engineering design tool. Earlier -work was oriented toward proving the techniques on simple, academic test problems. Much as in the case of finite element modeling, most of the effort in carrying out a successful shape optimization design project comes in creating the design model. In this case the design model is a detailed, parameterized description of the geometry to be designed. The capability described in this paper is based upon a boundary-oriented geometrical description with no information about the interior. Although this is the simplest of all possible descriptions and has been shown to work well on less complex problems, a more automated tool was necessary for realistic components. This paper describes an interactive graphics modeling system which creates all of the data necessary to design stamped sheet metal components using optimization.
1988-04-01
Technical Paper
880915
James A. Bennett
Structural optimization has been used for many years as an algorithmic way to select the best structural design from a number of competing designs. Expert or knowledge based systems have been proposed as ways to include more discreet knowledge. This paper will discuss some of the recent applications of knowledge based systems to structural design. An example of an exploratory system which includes both structural optimization and knowledge based systems will be described. This system uses a knowledge based program to evaluate the results of a structural optimization program to suggest ways that the constraints might be modified if a lighter weight design is required.
1988-04-01
Technical Paper
880916
Chi-Mou Ni, Ren-Jye Yang, Joanne R. Zuzelski
A concurrent engineering approach to integrate forming analysis by METALFORM and stress analysis by NASTRAN has been proposed and demonstrated on a practical structure. Including the forming effects of thinning and residual stress improves correlation with actual behavior of structures when performing a finite element stress analysis. In addition a simplified structural optimization process was formulated by including both structural functional requirements, such as stiffness and crush strength, and manufacturing constraints of split and springback. Results obtained from applying this simplified optimization process to two-dimensional rail-type components show that a rectangular cross section is the optimal shape in terms of minimum mass while satisfying both structural functional requirements and manufacturing constraints.
1988-04-01
Technical Paper
880783
Kyung K. Choi, Jose L. T. Santos, Tse-Min Yao
This paper presents a summary of recently developed unified method of continum design sensitivity analysis of linear and nonlinear structural systems. Sizing design variables, such as thickness and cross sectional areas, and shape design variables, such as length and geometric shape, of structural components of built-up structures are considered. For design sensitivity analysis of nonlinear structures, both geometric and material nonlinearities are considered using the total and updated Lagrangian formulations. For sizing design variables, a distributed parameter structural design sensitivity analysis approach that retains the continum elasticity formulation throughout the derivation of design sensitivity analysis results is used. For shape design variables, the material derivative concept of continuum mechanics is used to relate variations in structural shape to measures of structural performance.
1988-04-01
Technical Paper
880784
O. H. Burnside, Y.-T. Wu
The purpose in doing probabilistic structural analysis is to provide the designer with a more realistic ability to assess the importance of uncertainty in the structural response. This paper provides an overview of the methodology and discusses validation of modular structural analysis packages capable of predicting the probabilistic response distribution for key structural variables such as stress, displacement, natural frequencies, buckling loads, transient responses, etc. The structural analysis solution is in terms of the cumulative distribution function (CDF). Probabilistic structural analysis methods (PSAM) can be used to estimate structural safety and reliability, while providing the engineer with information on the confidence that should be given to the predicted behavior.
1988-04-01
Technical Paper
880785
Gregg Huggenvik
With the ever increasing number of thermoplastic resins, alloys and composites on the market, selecting the correct material to meet a critical application can be difficult. Cost restrictions, resin morphology, operating environment, property requirements and processing requirements are discussed as to their affect on the selection of plastic materials.
1988-04-01
Technical Paper
880787
Per Flem
High performance plastics are cost effective solutions to a number of power train applications. These materials offer unique opportunties to reduce the number of components in an assembly because of the complexity of part design available with injection molding.
1988-04-01
Technical Paper
880786
Harold K. Coxon
Since its commercial introduction, Reaction Injection Molding has found advantages in Automotive, Industrial and Consumer markets, primarily in large part applications. However, the limitations of traditional polyurethane RIM materials have limited the use of the process to non-structural parts. Today, with new advances in polyurethane chemistry, combined with the technology of long fiber reinforcement and RIM processing advantages, structural applications for the construction equipment industry are a viable alternative. This paper will offer a snap shot review of the emergence of polyurethane RIM technology and the markets it serves.
1988-04-01
Technical Paper
880788
Jack Bruss
A new low weight high performance battery has been develolped to satisfy the extreme durability and vibration resistance requirements necessary for use in heavy duty off highway vehicles. A Polypropylene Container and Cover construction offers several benefits with respect to weight and strength. In addition, design changes have been made to the internal components of the battery to improve battery life in an extremely hostile envionment.