1,721,104 research outputs found
Local Strain for Fatigue Strength of Welded Structures
No full textField criteria, which are usually applied in fracture mechanics to ensure the structural integrity of cracked components, are extended to the fatigue design of welded joints, whose weld toe can be assimilated to a notch with a small tip radius. In particular, fatigue strength in terms of strain rather than of stress has been determined by applying stress cycles with different stress ratios R = sigma (min)/sigma (max). Finally, for the evaluation of the fatigue strength of welded joints in structural steel, a strain curve versus different R ratios is given to be compared with the service measured local strain at the weld toe
An efficient Sequential Linear Programming algorithm for engineering optimization
No full textThis paper discusses the features of a new tool for engineering optimization problems. The new tool, Linearization Error Sequential Linear Programming (LESLP), includes an improved formulation of the well-established Sequential Linear Programming method. The LESLP algorithm is tested in seven structural optimization problems and two mathematical programming problems. The numerical efficiency, merits and limitations of LESLP are investigated in detail and compared with other general purpose optimization algorithms. Results indicate that LESLP is competitive with respect to other optimization algorithms published in the literature
Stress field near sharp notches
No full textThe correct description of the stress field of a two dimensional linear elastic domain with sharp notches and under complex load conditions can be obtained using the superposition of two elementary stress fields having respectively symmetric and anti-symmetric displacements. On the free boundaries of a sharp notch, the distance between the singularity and the points where the radial stresses have the same values for both the elementary stress fields, can be used for a complete description of the stress distribution of domains with the same shape and different sizes. This distance is proportional to the intrinsic defect introduced by the shape of the domain. An example of application of the described approach has been performed with regard to the parametric analysis of the stress field and of the intrinsic defect in an idealised model of a welded butt join
Applicazione di tecniche numeriche e sperimentali alla progettazione dei giunti a sovrapposizione
No full textA numerical code for lay-out optimization of skeletal structures with Sequential Linear Programming
No full textThis paper discusses a new Sequential Linear Programming (SLP) algorithm denoted as LESLP (Linearization Error Sequential Linear Programming). The new algorithm implements an advanced strategy to choose the move limits which are defined by limiting the difference between the original nonlinear problem and its linearized counterpart. Besides, LESLP includes a trust region model to increase the design freedom and to improve the overall efficiency of the optimization process. LESLP is tested in five lay-out optimization problems of skeletal structures (i.e. bar trusses and frames) where the, objective is to minimize the weight of the structure. It is obviously intended that the objective function does not require structural analysis. The new algorithm is compared to other SLP based techniques and globally convergent optimization methods like Sequential Quadratic Programming (SQP). Results indicate that LESLP is competitive with recently published algorithms and commercial softwares. Also, the new algorithm is robust with respect to starting designs
Improved sequential linear programming formulation for structural weight minimization
No full textThis paper presents an optimization algorithm for weight minimization of structures. The algorithm-denoted as LSTRLP (line search trust region linear programming)-combines sequential linear programming (SLP) and Trust region methods (TRM). LSTRLP solves a linearized sub-problem in each design cycle and accepts or rejects intermediate designs based on a line-search strategy which detects if the eventual improvement in cost is actually the largest possible. It is to be noticed that the present work is the closure to several studies carried out by the present authors in order to improve the overall efficiency and robustness of the sequential linear programming method.
The LSTRLP algorithm is implemented by an optimization code written in Fortran 90. The optimization code is tested in eight cases of weight minimization of bar truss and frame structures. The test cases include examples of large-scale and configuration optimization. The results obtained here are compared to those presented in literature. The optimizations are run also with sequential quadratic programming (SQP) routines implemented in commercial software. The results indicate that LSTRLP is competitive with recently published algorithms and commercial software
Polycarbonate for frozen stress photoelasticity
No full textThe possibility of using polycarbonate in the frozen stress photoelastic technique is investigated. The results obtained from strip specimens made of laminated and extruded polycarbonate and from plates confirm this possibilit
- …
