NASTRAN Program Research Articles

Математическое и компьютерное моделирование колебания системы «груз-балка» козлового крана

Introduction. Gantry grappling cranes are the main equipment for cargo transportation in the technological processes of mining and enrichment of rocks. During the operation of the crane, undesirable effects such as the rocking of the payload occur, which in turn affects the dynamic state of the crane beam. Materials and methods. To solve this problem, methods of mathematical and computer modeling of a system with two degrees of freedom were used. To identify the influence of different combinations of the combination of payload mass and cable length on oscillation frequencies, a computational experiment was carried out and the response surface of the oscillation frequency function was constructed. The natural oscillation frequencies of the beam were determined by the finite element method in the NASTRAN program. Results. The results of mathematical modeling were graphs of changes in the angle of deviation of the cable from the vertical and the movement of the trolley, the response surface of the frequency of oscillation of the payload from the length of the cable and the weight of the cargo. Discussion. A comparison of the simulation results of cargo vibrations and crane beam vibrations showed the proximity of the values of the frequencies of the payload vibrations and the gantry crane design, which justifies the need for further analysis of the frequency response of the crane beam to the disturbance of the payload vibration force. Conclusion. The frequency of vibrations of the load significantly affects the static and vibration strength of the crane beam of the gantry crane Resume. The research results can be useful in the development of technical solutions for the engineering implementation of promising gantry crane designs.

Analysis of the influence of the meshing size for an oil tanker structural model on the stress hot spot values

The development of the shipbuilding industry leads to new requirements for the safety of ships. Stress hot spots are recorded on every floating structure and they influence nega-tively the hull strength. This analysis identifies the stress hot spots and the influence of the meshing size on their values for a 97235 tdw oil tanker, using the Femap/NX Nastran program. Structurally, two constructive options were considered for the central longitudi-nal bulkhead: corrugated and flat panels. The detailed local structural model is devel-oped for three mesh sizes: coarse, medium, and fine. Quad and triangle shell elements are used for the FEM local models.

On the strength assessment of a small liquid petroleum gas carrier in oblique waves by 1D and 3D-FEM analyses

The research from this paper is focused on the strength assessment in oblique design waves of a small LPG liquid petroleum gas carrier, with maximum length of 125.6 m. As loading conditions, full cargo and ballast cases are selected. Because the LPG carrier has an unrestricted maritime navigation class, the maximum height of the oblique quasi-static wave is 12 m, in hogging and sagging conditions, with a height step of 1 m. The LPG-oblique quasistatic waves heading angle is in the range 0 – 75 (360) degrees, with step 15 degrees, where the maximum structural response is expected to occur. For the numerical analyses two classes of structural models have to be considered, equivalent 1D-beam and 3D-FEM, both extended over the whole LPG length, on both sides. The 1D model is implemented in the eigen code P_QSW for the LPG and oblique waves equilibrium parameters and sectional efforts computation, by a non-linear iterative three parameters procedure. For detailed structural analysis the LPG 3D-FEM model is used, developed by Femap/NX Nastran program. Combining the numerical results by 1D and 3D models, the safety polar diagrams, in terms of limit oblique quasi-static waves’ height, for the small LPG carrier strength assessment are obtained.

Computer simulation and investigation vibration parameters of a centrifugal submersible pump

The dynamic characteristics of one of the centrifugal pump critical parts such as the rotor shaft are studied in the article whilst the highest level NASTRAN CAD PATRAN module was used to carry out the dynamic analysis. During the analysis a computational mechanical scheme has been compiled as well as force factors generating rotor vibrations have been determined. The axial, radial and hydrodynamic forces affecting the impeller and pump shaft have been calculated according to the analytical formula. Under the given boundary conditions in the FE model and the chosen method for determining the natural vibrations, a numerical solution of the equations of free and forced vibrations has been found using the algorithms of the NASTRAN program. The natural vibrations of the rotor have been determined using the Lanczos method. The dynamic stability of the shaft, the stress-strain state of the shaft and its displacement under static loads, the frequency and shape of the natural vibrations of the rotor necessary for the calculations have been determined. The amplitude-frequency characteristics of the system have been determined and analyzed for affection by external forces at the reverse and blade frequencies. Using the amplitude parameters of the forced oscillations, the dynamic gain of the rotor has been determined. Based on the amplitude-frequency parameters, the option of the number of blades for the working centrifugal impeller of the pump has been justified. The technique of computer simulation and determination of the vibroactivity parameters of a submersible centrifugal pump rotor shaft is given in the article.

Reinforcing the Holes in High-Pressure Vessels

Optimization of the design of reinforcements of holes is achieved through an analysis of conditions for reinforcing holes in pressure vessels adopted in contemporary regulatory documents. A calculation of their stress-strain state performed by the Nastran program is used as an example. For entries into elliptical floors, a decrease in the estimated length of the reinforcing metal is recommended. It is shown that effective reinforcement of the lateral entries into a cylinder is possible only by increasing the total wall thickness of the body at the site of the entry.

Comparison between Numerical Results of 1D Beam and 2D Plane Stress Finite Element Analyses Considering Aspect Ratio of Cantilever Beams

There exist different kinds of aircrafts, such as conventional airplane, rotorcraft, fighter, and unmanned aerial vehicle. Their shape and feature are dependent upon their own assigned mission. One of the fundamental analyses performed during the aircraft design is the structural analysis. It becomes more complicated and requires severe computations because of the recent complex trends in aircraft structure. In order for efficiency in the structural analysis, a simplified approach, such as equivalent beam or plate model, is preferred. However, it is not clear which analysis will be appropriate to analyze the realistic configuration, such as an aircraft wing, i.e., between an equivalent beam and plate analysis. It is necessary to assess the limitation for both the one-dimensional beam analysis and the two-dimensional plate theory. Thus, in this paper, the static structural analysis results obtained by EDISON solvers were compared with the three-dimensional results obtained from MSC NASTRAN. Before that, EDISON program was verified by comparing the results with those from MSC NASTRAN program and other analytic solutions.

A Method For Producing Hollow Shafts By Rotary Compression Using A Specially Designed Forging Machine

Abstract The paper presents a new method for manufacturing hollow shafts, where tubes are used as billet. First, the design of a specially designed forging machine for rotary compression is described. The machine is then numerically tested with regard to its strength, and the effect of elastic strains of the roll system on the quality of produced parts is determined. The machine’s strength is calculated by the finite element method using the NX Nastran program. Technological capabilities of the machine are determined, too. Next, the results of the modeling of the rotary compression process for a hollow stepped shafts by the finite element method are given. The process for manufacturing hollow shafts was modeled using the Simufact.Forming simulation program. The FEM results are then verified experimentally in the designed forging machine for rotary compression. The experimental results confirm that axisymmetric hollow shafts can be produced by the rotary compression method. It is also confirmed that numerical methods are suitable for investigating both machine design and metal forming processes.

Research on Structural Strength of Catamaran Superstructure Constructed with Aluminum Alloy

The design of Superstructure constructed with aluminum alloy do not have to follow the traditional standard design method. It can be designed by applying strength theory and ANSYS program or MSC Patran / Nastran program, which can ensure the strength requirements with the selected aluminum alloy components and make the weight of the ship lightest. In this paper, the 42.4m catamaran sightseeing boat is used as an example. The structural strength of the superstructure constructed with aluminum alloy is calculated by MSC Patran / Nastran program. The distribution of the superstructure stress is obtained, which proved the size of the selected components of the superstructure can meet the requirements of the local strength and can be the reference of selecting the structure size. As the other conditions are unchanged, the the local thickness of the junction of the front wall and the side wall of the compass deck is changed. the relationship between plate thickness and stress is obtained. It is found that as The plate thickness is thicker, the stress there decreases; and as the thickness is smaller, it is obvious to reduce stress as the plate thickness Increase. when the thickness increases to a certain extent, the effect of the plate stress decreases is not obvious.

Computer simulation of the new ring seal coaction in combustion engine

A computer simulation which as model loads uses program KIVA 3 for combustion engine work process (combustion chamber heat flux, pressure and temperature) computations has been developed. It makes it possible to compute the pressure and temperature distributions and the motion of the charge in the combustion chamber at a particular point in the work cycle. Computer models of the ring seal components were constructed using computer code Parasolid v. 11. The models render to the finest detail the design‐material features of the ring seal components. The Nastran program was used to perform FEM computations for a selected point of engine work (at a crank angle of 10°) at which the maximum averaged temperatures and pressures were found to occur in the combustion chamber. Finally, 3D temperature and pressure distributions for the whole ring seal were obtained. On their basis, inferences can be made about the design‐technological nature of the seal under development.

Post-buckling behavior of two elastica columns linked with a rotational spring

The post-buckling problem of a fixed-free column composed of two segments connected by a linear rotational spring with different flexural stiffness and lengths is studied. A semi-analytical solution is derived and the results are checked using two different numerical approaches. In the first approach, the problem is solved using numerical integration technique, while in the second approach, the problem is solved using large displacement finite element analysis of NASTRAN program. Excellent agreements have been obtained between the semi-analytical and the numerical approaches. Furthermore, a regression analysis has been made for the parameters covered in this study and a regression function has been obtained which relates to the tip axial horizontal displacement ( δ) as a function of load parameter ( α) and fixity ratio ( f). From this function, the stored strain energy ( U) is obtained and plotted to be used as a design chart for engineers to obtain the required fixity ratio for a given stored strain energy and load parameter.

A study on the dynamic characteristics of the Korean Yi-dynasty bell type structure

The dynamic characteristics of the Korean Yi-dynasty bell type structure, including the acoustic effects, are analyzed both theoretically and experimentally. The numerical solutions of natural frequencies and mode shape for membrane and flexural behavior are obtained by using the NASTRAN program for the finite element method with plate shell elements of triangular and quadrilateral types. Test bells, A and B types similar to the Kap-Sa bell in Kong-Ju chosen among typical Korean Yi-dynasty bells, are manufactured on different scales to the original bell. To consider the effects of the variation of the structural dimension on the dynamic response, these bells are analyzed with respect to the variation of the thickness of the wall and the bottom rim and the asymmetric Dang-Jwas. The impact method with the Fast Fourier Transform Analyzer is adopted to experimentally assess the dynamic response. Results are in good agreement with the numerical solutions.

A cost-effective eigensolution method for large systems with Rockwell NASTRAN

The Lanczos method with reorthogonalization based on Householder transformations has been implemented in Rockwell's version of the COSMIC-released NASTRAN program for partial solution of a large-scale symmetric eigenvalue problem. A special technique has been included for restarting Lanczos iteration with a new random vector, partly to avoid premature termination associated with a null or linearly dependent Lanczos feed vector and partly to discover multiple eigenvalues. The developed Lanczos-Householder algorithm with built-in random restart capability shows appreciable cost-savings over the conventional subspace iteration technique as well as the COSMIC NASTRAN method, FEER, which utilizes the modified Gram-Schmidt process to reorthogonalize the Lanczos feed vector with respect to those previously converged.

アルミナ・セラミックス人工足関節置換後における足関節の2次元FEMによる解析

Normally, arthrodesis is indicated if only an ankle joint is destroyed. However if there are pathological changes in the neighboring joints, it is desirable to preserve joint functions and an artificial ankle joint replacement is indicated in many cases. We made models of the lateral views of ankle joints and performed a comparative investigation of (1) deformations and (2) major and minor principal stresses by means of the finite element method by inferring (1) physiological conditions, (2) conditions immediately after replacement with an artificial ceramic joint, which we developed, without cement, (3) conditions of fusion between the ceramic and the bone a few months after the replacement, and positions of a lower leg (4) standing on one leg medially, (5) inclined posteriorly and (6) inclined anteriorly. The NASTRAN program was used in the analysis and membrane and rod elements were used for element divisions. A tibial component of an artificial joint was loaded mainly on the anterior cortical bone of the tibia and on the posterior cancellous and cortical bone. A component of a talus having a stem in the center replaced a joint surface. The physiological stress distribution was similar to the travecular course. Immediately after replacement with an artificial joint, there was a large amount of stress in the ceramic, but compressive stress was found between the ceramic and the bone. After fusion between the artificial joint and the bone, stress distributions changed to approximately the same conditions as the physiological conditions. These results were investigated comparatively with clinical results.

NASTRAN: A Preliminary Discussion of User Impacts

INDUSTRY and government agencies have devoted serious and concerted efforts to developing tools to aid in solving a wide variety of large, structural analysis problems. The NASA Structural Analysis Computer Program (NASTRAN) was specifically designed to provide such a capability. NASTRAN is a general purpose digital computer program designed to analyze the behavior of elastic structures under a range of loading conditions, using a finite-element displacement method approach. Analytical capabilities include 1) static response to concentrated and distributed loads, thermal expansion, and enforced deformation; 2) dynamic response to transient loads, steadystate harmonic loads, and random excitation; and 3) determination of real and complex eigenvalues for use in vibration analysis, dynamic stability analysis and elastic stability analysis. The system has the capability of treating problems of virtually unlimited size, because economic considerations will generally limit the problem size long before reaching the limitations of the NASTRAN algorithms. NASTRAN is highly user-oriented, which partially accounts for its widespread acceptance and popularity. The program is systematically organized to do much of the work automatically and minimize the burden on the analyst. NASTRAN includes over 151,000 fortran statements, which translate into more than 1,000,000 machine language statements. It is machine independent, with options available for the IBM 360 and 7090 series, UNIVAC 1108 and CDC 6000 series. The NASTRAN program has an extensive plotting capability. NASTRAN was developed during the period 1965-1970 at NASA's Goddard Space Flight Center at an estimated cost of $3,000,000. Since its release for public use in November, 1970, continued development and management of the program have been transferred to the Langley Research Center. Because it represents the capture of significant secondary returns on the investment of the public research and development dollar, NASA has sponsored a study to survey the extent of the usage of NASTRAN and estimate some of the benefits that have accrued to users. In addition, information has been compiled regarding costs of performing certain applications, as well as new improvements or adaptions which have been developed by users. The following are the major results of that study.