Finite integration method for nonlocal elastic bar under static and dynamic loads

The finite integration method is proposed in this paper to approximate solutions of partial differential equations. The coefficient matrix of this finite integration method is derived and its superior accuracy and efficiency is demonstrated by making comparison with the classical finite difference method. For illustration, the finite integration method is applied to solve a nonlocal elastic straight bar under different loading conditions both for static and dynamic cases in which Laplace transform technique is adopted for the dynamic problems. Several illustrative examples indicate that high accurate numerical solutions are obtained with no extra computational efforts. The method is readily extendable to solve more complicated problems of nonlocal elasticity.     

Regularities of the deformation of metallic materials under various conditions of static loading

The article analyzes the results of the application of the equation for describing creep of metals in various temperature and force ranges with the aid of the same numerically specified constants. An experimental evaluation is made of the possibility of describing from the same positions the regularities of instantaneous and short-term deformation, creep, stress relaxation, and creep limit.Translated from Problemy Prochnosti, No. 8, pp. 51–58, August, 1990.     

Structural shape optimization using equivalent static loads transformed from dynamic loads

In structural optimization, static loads are generally utilized although real external forces are dynamic. Dynamic loads have been considered only in small‐scale problems. Recently, an algorithm for dynamic response optimization using transformation of dynamic loads into equivalent static loads has been proposed. The transformation is conducted to match the displacement fields from dynamic and static analyses. This algorithm can be applied to large‐scale problems. However, the application has been limited to size optimization. The present study applies the algorithm to shape optimization. Because the number of degrees of freedom of finite element models is usually very large in shape optimization, it is difficult to conduct dynamic response optimization with conventional methods that directly treat dynamic response in the time domain. The optimization process is carried out by interfacing an optimization system and an analysis system for structural dynamics. Various examples are solved to verify the algorithm. The results are compared to the results from static loads. It is found that the algorithm using static loads transformed from dynamic loads based on displacement is valid for very large‐scale shape optimization problems. Copyright © 2005 John Wiley & Sons, Ltd.     

Transformation of dynamic loads into equivalent static loads based on modal analysis

All the forces in the real‐world act dynamically on structures. Since dynamic loads are extremely difficult to handle in analysis and design, static loads are usually utilized with dynamic factors. Static loads are especially exploited well in structural optimization where many analyses are carried out. However, the dynamic factors are not determined logically. Therefore, structural engineers often come up with unreliable solutions. An analytical method based on modal analysis is proposed for the transformation of dynamic loads into Equivalent Static Loads (ESLs). The ESLs are calculated to generate an identical displacement field with that from dynamic loads at a certain time. The process is derived and evaluated mathematically by using the modal analysis. Since the exact solution is extremely expensive, some approximation methods are proposed. Error analyses have been conducted for the approximation methods. Standard examples for structural design are selected and solved by the proposed method. Applications of the method to structural optimization are discussed. Copyright © John Wiley & Sons, Ltd.     

Modeling for fracture in materials under long-term static creep loading and neutron irradiation. Part 2. Prediction of creep rupture strength for austenitic materials

We present some results of prediction of creep rupture strength and plasticity for austenitic materials prior to and after irradiation with variable neutron flux rates, based on physicomechanical model as outlined in Part 1. The calculated results are compared with the available experimental data. __________ Translated from Problemy Prochnosti, No. 5, pp. 5–15, September–October, 2006.     

Corrugated panels under dynamic loads

Corrugated panels are commonly used as blast walls on offshore installations, and an assessment of their response to dynamic pressure loads needs to be made during design. Although detailed numerical models are commonly used, simplified models based on spring-mass idealisations, such as Biggs’ method, are still important for preliminary design. Based on an earlier static formulation, the dynamic response of a corrugated panel (as characterised by its central deflection) subjected to a uniformly distributed pressure pulse is analysed. A simplified theoretical method is built up and new transformation factors for panels with straight endplates are derived. The method is calibrated against corresponding finite element and experimental results. Good agreement is achieved.     

Discrete variable optimization of structures subjected to dynamic loads using equivalent static loads and metaheuristic algorithms

Optimization and Engineering - This paper presents a new computational procedure for optimization of structures subjected to dynamic loads. The optimization problem is formulated with discrete...     

Optimal arch shape solution under static vertical loads

In this paper, a new analytical solution for the optimal shape of a plane-statically determined arch subjected to uniform vertical loads is presented. The classical problem of a catenary subjected to the self-weight is extended to an inverted catenary subjected to the self-weight and to a constant vertical load distribution. In this condition, the authors demonstrate that a class of analytical solutions exists and that unlike previously proposed solutions it corresponds to the minimum ratio of the self-weight of the arch to the total applied load. Finally, existence conditions for such a solution are derived.     

Optimal structural design under dynamic loads

This paper presents an algorithm for optimal design of elastic structures, subjected to dynamic loads. Finite element, modal analysis and a generalized steepest descent method are employed in developing a computational algorithm. Structural weight is minimized subject to constraints on displacement, stress, structural frequency, and member size. Optimum results for several example problems are presented and compared with those available in the literature.     

Behaviour of shear connectors under dynamic loads

The details of an experimental investigation of the fatigue strength of stud type shear connectors are described. A new type of test set-up called ‘New Standard Test Method’ has been employed to assess the fatigue strength of an individual shear connector. The results of the fatigue tests are discussed and a simple relationship between the stress range and the number of cycles has been obtained. This relationship is compared to the one obtained by Slutter on the basis of his experiments.     

Calculation of the static creep of heat-resistance materials according to the method of isochrones

The principle of similarity of isochronic curves is sued to devise a unidimensional creep model describing all stages of the process, and the basic experiment is specified. The instantaneous deformation diagram is used as the initial characteristic of the medium in the model. The model describes accelerated creep without making use of the damage function. The creep parameters of heat-resistant materials are calculated in a wide range of temperatures; satisfactory agreement between the theoretical values and experimental data was obtained.Translated from Problemy Prochnosti, No. 2, pp. 40–44, February, 1990.