WorldCat Identities

CALIFORNIA UNIV SAN DIEGO LA JOLLA Dept. of THE AEROSPACE AND MECHANICAL ENGINEERING SCIENCES

Overview
Works: 91 works in 93 publications in 1 language and 93 library holdings
Genres: Conference papers and proceedings 
Classifications: TA660.S5, 624.1776
Publication Timeline
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Most widely held works by CALIFORNIA UNIV SAN DIEGO LA JOLLA Dept. of THE AEROSPACE AND MECHANICAL ENGINEERING SCIENCES
Optimization of a standard linear viscoelastic material for use in a seat belt by W Nachbar( Book )

1 edition published in 1969 in English and held by 1 WorldCat member library worldwide

It is shown that a properly designed viscoelastic seat-belt material could have a low stiffness at low strain rates while still affording considerable improvement in the maximum safe cruising speed in comparison with a linear elastic belt. (Author)
Optimization in a Class of Relaxation Moduli for Linearly Viscoelastic Materials( Book )

1 edition published in 1971 in English and held by 1 WorldCat member library worldwide

Optimization of relaxation functions E for linearly viscoelastic materials is considered for a one-dimensional problem which is suggested by desirable performance of a lap-seat belt in automobiles. An optimum relaxation modulus E bar of the belt is sought which would permit the speed v sub 0 of the vehicle prior to an abrupt impact to have maximum value v bar sub 0 under certain constraints imposed for the safety of the user of the belt. A class c star of costfunctions is defined on the deceleration u that is imposed by the belt on the user. For given c belongs to c star, the post-impact constraints imposed are (1) the maximum displacement of the body must not exceed a critical displacement, (2) the forward speed of the body, if and when at the critical displacement, should not exceed a prescribed maximal value v sub f, and (3) the values of c during the motion of the body must not exceed an allowed maximal value cmax. Optimization of E is sought in a defined class of relaxation moduli, constructed so as to limit the rubbery moduli to values not exceeding a specified, relatively low value, thus contributing to the comfort of the passenger during non-crash conditions. It is shown in the paper, for each c belongs to c star, that constraints (1) and (2) are both active if the E bar material is employed at the maximal speed v bar sub 0. In addition, it is shown that constraint (3) is active for any c of a certain subset of c star. (Author)
The generation of thermoelastic stress waves by impulsive electromagnetic radiation( Book )

1 edition published in 1967 in English and held by 1 WorldCat member library worldwide

The absorption of electromagnetic radiation within a thin, but finite, surface layer of an elastic half-space provides a sudden heat source distribution through the layer, and stress waves are generated. A solution for uni-axial motion is given in the limit situation when the pulse duration approaches zero in comparison with the wave travel time through the layer, together with the neglect of thermal diffusion on this time scale. The radiation absorption is assumed to decay exponentially with depth. These simplifying features lead to stress wave profiles which clearly illustrate the effective nature of the solution. In the case when the surface is stress free, after the initial build-up (here instantaneous) of compressive stress within the layer, a tensile wave propagates out of the layer. Numerical data are presented to show that the peak tensile stress can attain significant levels within a few layer thicknesses of the surface. (Author)
Similarity solutions for expansion of a hole in anisotropic plastic disks( Book )

1 edition published in 1969 in English and held by 1 WorldCat member library worldwide

Similarity solutions are obtained for the expansion of a circular hole with zero (pin-hole) or finite initial radius in an infinitely extended, axisymmetric, anisotropic disk of a non-uniform initial thickness. A linear workhardening law is used together with Mises' and Tresca's yield conditions. A complete closed-form solution is developed for Tresca's yield condition and its associated flow rule. Similar results are obtained for Mises' yield condition and its associated flow rule; these results are not, however, in a closed-form. Two illustrative examples are worked out in detail to demonstrate the basic results, especially the effects of anisotropy and workhardening. (Author)
The lateral buckling of a circular ring sector plate subjected to pure bending( Book )

2 editions published in 1968 in English and held by 1 WorldCat member library worldwide

This paper is concerned with the lateral buckling of a thin circular ring sector plate loaded only at the ends with a system of stress resultants which are statically equivalent to a bending moment acting in the plane of the plate. The buckling moments obtained here from plate theory are shown to be in complete agreement with a recent paper by the author giving experimental and theoretical results on the lateral buckling of curved beams. Both of these papers are in disagreement with the classical curved beam theory solution to the problem. However, the author has shown in the earlier paper that this classical solution is in error due to an imposition of boundary conditions which are inconsistent with the basic differential equations of the problem. (Author)
Thin-shell structures; theory, experiment and design [proceedings] by Y. C Fung( Book )

1 edition published in 1974 in English and held by 1 WorldCat member library worldwide

The book describes the status of the theoretical and experimental understanding of the mechanics of thin-walled shell structures as known in the 1970's. The distinctive feature of this book is in its emphasis on experimental evaluation of the theories, and on practical concerns for shell design. The book is the edited proceedings of the Symposium on Thin Shell Structures: Theory, Experiment and Design which was held in Pasadena, California from June 29 to 30, 1972. (Author)
On local stability of a finitely deformed solid subjected to follower type loads( Book )

1 edition published in 1967 in English and held by 1 WorldCat member library worldwide

The problem of the local stability (stability in the small) of a finitely deformed solid subjected to a set of follower type surface loads is analyzed, and a necessary, and a sufficient condition for asymptotic stability is established. Certain implications of the commonly used modal analysis are also investigated, and necessary and sufficient conditions for stability are formulated. (Author)
Dynamic optimization of a viscoelastic structure: the seatbelt( Book )

1 edition published in 1968 in English and held by 1 WorldCat member library worldwide

Optimization of the parameters of elementary linear viscoelastic models is considered for the design of a lap seatbelt in automobiles. The vehicle is assumed to stop abruptly on impact. The parameters are optimized to allow the speed of the vehicle before impact to have the largest permissible value consistent with constraints imposed for the safety of the user of the belt. The constraints chosen here are: (1) the maximum displacement of the body after impact is equal to or less than a prescribed critical displacement; (2) the forward speed of the body at the critical displacement does not exceed a prescribed maximum value; (3) the force exerted by the belt on the body during the motion following impact does not exceed a prescribed maximum value. It is found that the optimized Kelvin-Voigt viscoelastic model is nearly 40% more effective than the purely elastic material. It is nearly as effective as constant deceleration. An additional and advantageous property is proposed, moreover, for belts of viscoelastic materials. This is that the material should have a relatively low spring rate at relatively small strain rates. The optimized belts for the elementary viscoelastic models are shown to be quite stiff at low strain rates, however. (Author)
A Koiter-Type Method for Finite Element Analysis of Nonlinear Structural Behavior. Volume I. The Modified Structure Method( Book )

1 edition published in 1970 in English and held by 1 WorldCat member library worldwide

Koiter's method for the asymptotic analysis of post-buckling behavior is reformulted in finite element notation for application to structures idealized by finite element models. Koiter's method is herein adapted to a general class of structures exhibiting the common snap-through (limit point) type of buckling. This is referred to as the Modified Structure method. It is accomplished by modification of the actual energy functional to create a hypothetical modified structure having a strictly linear pre-buckling path along which buckling must be of the bifurcation type. The analysis of the actual structure is then accomplished by application of Koiter's method through consideration of the actual structure as an imperfect version of the modified structure. The effects of pre-buckling nonlinearity are approximated asymptotically. The use of the Modified Structure method in conjunction with direct methods of nonlinear analysis is examined. A highly accurate finite element representation is employed in presenting a comprehensive numerical evaluation of the Modified Structure method of analysis on the basis of a number of planar frame problems. (Author)
Optimal design of elastic structures for maximum stiffness( Book )

1 edition published in 1967 in English and held by 1 WorldCat member library worldwide

The purpose the paper was to establish a general theory of optimal design of elastic structures such that the structure with a given volume would have maximum stiffness. A sufficient condition of optimality was derived from the principle of minimum potential energy. This optimality condition was proven by the variational method to be a necessary one under the condition that the optimal structure has certain continuity and differentiability properties. Physical interpretations of the optimality condition were discussed for problems of beams, plates and trusses. An application of the theory was illustrated in a problem of optimal design of a simply supported circular plate under uniform pressure. Detailed description of the numerical procedure for the solution of the plate problem was presented. (Author)
Minimum-weight design of beams for multiple loading( Book )

1 edition published in 1967 in English and held by 1 WorldCat member library worldwide

The paper discusses minimum-weight design of beams of continuously varying cross section that have to carry any one of n systems of loads. The weight per unit length is assumed to be given by w(x) = a + bY(x), where a and b are constants and Y(x) is the yield moment at the cross section x. A design method is presented that remains valid for the extreme cases n = 1 and n = infinity and that enables the designer to prescribe a minimum value Y sub o below which the yield moment is not allowed to drop. The use of the method is illustrated by examples. (Author)
Proceedings of the Symposium on Nonlinear Estimation Theory and Its Applications (2nd), Held at San Diego, Calif. on 13-15 Sep 71( Book )

1 edition published in 1971 in English and held by 1 WorldCat member library worldwide

The report gives the papers presented at the second symposium on nonlinear estimation theory and its applications
Stress wave generation in a temperature-dependent absorbing solid by impulsive electromagnetic radiation by G. A Hegemier( Book )

1 edition published in 1968 in English and held by 1 WorldCat member library worldwide

An elastic, partially transparent solid, occupying the half space x> 0, is subjected to uniform impulsive electromagnetic radiation at the surface x = 0. The deposition of radiant energy over a finite absorption depth gives rise to a distributed heat source within the solid (thermal shock) which, in turn, dilatates the medium and generates a stress wave. In this paper the nature of the stress-wave build up in the absorption layer is studied for the case of a temperature-dependent solid, i.e., when material properties vary with temperature. The mathematical problem is one of wave propagation in a non-homogeneous medium. An approximate solution to the posed problem is developed which readily exhibits the influence of temperature. Error bounds are provided. The results are illustrated by a numerical example. (Author)
The motion of the plasma between the red blood cells in the bolus flow( Book )

1 edition published in 1968 in English and held by 1 WorldCat member library worldwide

The motion of the plasma trapped between two adjacent red blood cells moving with a constant speed in a capillary blood vessel is studied. The convective inertia force of the plasma is neglected in comparison with the viscous stresses on the basis of the smallness of the Reynolds number of the flow in the capillary. The red cells are approximated by cylindrical pill boxes whose radii are the same as that of the blood vessel. The capillary blood vessel is approximated by a circular cylindrical tube with impermeable wall. With such an ideal model the velocity and pressure fields are determined. (Author)
Optimal plastic design of circular and annular sandwich plates with piecewise constant cross section( Book )

1 edition published in 1968 in English and held by 1 WorldCat member library worldwide

Hopkins and Prager used an intuitive approach based on the concept of competing yield mechanisms to discuss plastic minimum-weight design of a circular plate with piecewise constant cross section. Since their paper was written, the theory of optimal plastic design has progressed considerably, but subsequent papers on optimal plate design were exclusively concerned with plates of continuously varying cross section. In view of the lesser manufacturing cost of plates with piecewise constant cross section, the present paper reexamines the problem in the light of the modern theory of optimal plastic design. General optimality criteria are established and applied to full circular as well as annular plates. The relation of the designs obtained for annular plates to the singular designs investigated by Megarefs is discussed. (Author)
On linear ordinary differential equations with exponential coefficients( Book )

1 edition published in 1967 in English and held by 1 WorldCat member library worldwide

A system of linear ordinary differential equations with exponential coefficients is considered; several theorems are presented concerning general solutions and their asymptotic forms for large values of the independent variable; elementary examples are given and applications cited to illustrate, and demonstrate the utility of, the solution forms obtained. The relevance of the results to the solution of problems of structural stability and wave propagation is briefly discussed. (Author)
The lateral deflection of a circular ring plate buckled by a closing moment( Book )

1 edition published in 1968 in English and held by 1 WorldCat member library worldwide

This paper presents a numerical solution to the nonlinear von Karman plate equations. The particular problem considered is the axisymmetric lateral buckling of a circular ring plate having a ratio of the radii of 2 and a Poisson's ratio of 0.3. This problem corresponds to the lateral buckling of a complete ring under a closing moment, i.e., a moment tending to deform the plate into a ring of smaller radius. The equations are written in finite difference form, and an iterative technique is used to obtain the nonlinear solution. The results show that, for this particular case, the initial stage of post-buckling deformation is stable and does not exhibit any snap-through type of instability. This result is in agreement with experimental observations previously reported. (Author)
Fundamental Studies of Liquid-Propellant Rocket Combustion( )

2 editions published in 2004 in English and held by 0 WorldCat member libraries worldwide

This research was directed towards developing new knowledge of combustion processes in liquid-propellant rocket engines. Attention was given to the combustion of different fuels, beginning with hydrogen-oxygen but ultimately including multicomponent hydrocarbon mixtures representative of RP fuels, and to nonlinear processes of importance in combustion instability. Effects of detailed chemical kinetics on performance and stability were addressed by introducing systematically reduced chemistry that enables theoretical analysis to be completed thoroughly and accurately. The interactions between chemistry and turbulence were addressed, including the effects of the heat release on the turbulence. The orientation of the work was fundamental and aimed at predicting not only performance and acoustic response but also intrinsic instability. The results were intended to help to improve understanding of combustion mechanisms and combustion instabilities in liquid-propellant rocket motors. The most recent specific results concern induction times in hydrogen-oxygen mixtures and heal-release effects on turbulent missing
OPTIMAL DESIGN OF ELASTIC CIRCULAR SANDWICH BEAMS FOR MINIMUM COMPLIANCE( )

1 edition published in 1969 in English and held by 0 WorldCat member libraries worldwide

Elastic circular sandwich beams are designed for minimum compliance and given total weight. To treat the problem in a more realistic manner, the beams are regarded as extensible. Examples are given for the optimal design of circular rings and semicircular arches with different end conditions. The calculated optimal compliance is compared with the corresponding compliance of a uniform beam with identical weight. Finally, the optimal design with stress bounds is also investigated for the ring problem
Resilient Composites for Armor Applications( )

1 edition published in 2001 in English and held by 0 WorldCat member libraries worldwide

The original objectives of the proposed research were accomplished by H.C. Chen. After the successful completion of his Ph. D. Dr. Chen was employed by CERCOM and used the knowledge gained in his doctoral for the development of armor. He was actively involved in a number of defense projects, including the DARPA Light Weight Armor program coordinated by SwRI. The work in the AASERT proposal was published in Acta Materialia and the proceedings of the APS conference on shock compression of condensed matter. The objectives having been accomplished early, it was decided to redirect the program toward the processing, properties, and characterization of TiC-NiTi composites. Thus, the AASERT effort complemented and augmented the MURI in which the group was involved. Elizabeth Strun, a US citizen, was supported by the AASERT program throughout a good portion of its duration. The results reported herein are primarily her doctoral work, that is at an advanced state. It is felt that this AASERT program was highly successful, leading to seven publications
 
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English (22)