1. |
Tauzowski P., Błachowski B.D., Zawidzka E., Zawidzki M., MorphoGen: Topology optimization software for Extremely Modular Systems,
SoftwareX, ISSN: 2352-7110, DOI: 10.1016/j.softx.2024.101797, Vol.27, pp.1-10, 2024Streszczenie: This paper introduces MorphoGen — an integrated reliability-based topology optimization and nonlinear finite element analysis system for 2D and 3D domains. The system’s key innovation is its seamless prototyping of scientific formulations for computational problems in topology optimization. Its layered and object-oriented architecture, based on the template method design pattern, facilitates effortless modifications of algorithms and the introduction of new types of finite elements, materials, and analyses. MorphoGen also offers flexible handling of objective functions and constraints during topological optimization, enhancing its adaptability. It empowers researchers and practitioners to explore a wide range of engineering challenges, fostering a deeper understanding of complex structural behaviors and efficient design solutions. There are many topology optimization software and open source codes, especially based on the classical SIMP method. Unlike these codes our package is freely distributed among users and since it is distributed on the MIT licence, which allows for its easy modification depending on the particular needs of the users. For this purpose, we use the topology optimization algorithm proposed for the first time in our previous paper (Blachowski et al., 2020). The algorithm is based on a fully stress design-based optimality criteria and can be applied for topology optimization of either linearly elastic and elastoplastic structures. Additionally, the novelty of the proposed system is related to its ability of solving optimal topology under various constraints such as displacement, stresses and fatigue in both deterministic and probabilistic cases. Another application are modular structures, which reduce design complexity and manufacturing costs as well as rapid reconfiguration. However, in the realm of structural optimization, modular systems are more challenging due to various: modes of operation of the modules and the stresses configurations. Moreover, this area of research is dramatically less explored. Thus the effectiveness of MorphoGen for structural engineering is demonstrated with examples of topological shape optimization of two Extremely Modular Systems: a planar robotic manipulator Arm-Z and spatial free-form ramp Truss-Z. Słowa kluczowe: Stress Constrained Topology Optimizatio,Extremely Modular System,Object-oriented software architecture,MATLAB-based array programming,First Order Reliability Analysis Afiliacje autorów:
Tauzowski P. | - | IPPT PAN | Błachowski B.D. | - | IPPT PAN | Zawidzka E. | - | IPPT PAN | Zawidzki M. | - | IPPT PAN |
| | 200p. |
2. |
Tauzowski P., Błachowski B., Lógó J.^{♦}, Computational framework for a family of methods based on stress-constrained topology optimization,
COMPUTERS AND STRUCTURES, ISSN: 0045-7949, DOI: 10.1016/j.compstruc.2024.107493, Vol.303, pp.1-14, 2024Streszczenie: This study presents a general computational framework for topology optimization under constraints related to various engineering design problems, including: reliability analysis, low-cycle fatigue assessment, and stress limited analysis. Such a framework aims to facilitate comprehensive engineering design considerations by incorporating traditional constraints such as displacement and stress alongside probabilistic assessments of fatigue failure and the complex behaviors exhibited by structures made of elastoplastic material. The framework's amalgamation of diverse analytical components offers engineers a versatile toolkit to address intricate design challenges. Notably, the inclusion of reliability analysis introduces a probabilistic perspective, transforming conventional design constraints into random parameters, thereby enhancing the robustness of the design process.
Key to the framework's efficacy is its implementation using MATLAB mathematical computing software, leveraging the platform's efficient code execution and object-oriented programming paradigm. This choice ensures an intuitive and potent environment for designers and researchers, facilitating seamless adaptation across various engineering applications. Additionally, the proposed previously by the Authors algorithm for the topology optimization is extended by adaptive strategy allowing for efficient adjustment of an amount of material removed at individual optimization step.
The presented framework is offering a comprehensive and integrated approach to address multifaceted design challenges while enhancing design robustness and efficiency. Słowa kluczowe: Topology optimization, Stress constraints, First order reliability analysis, Low-cycle fatigue, Plasticity Afiliacje autorów:
Tauzowski P. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Lógó J. | - | University of Technology and Economics (HU) |
| | 140p. |
3. |
Tauzowski P., Błachowski B., Lógó J.^{♦}, Optimal topologies considering fatigue with reliability constraint,
Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2023.103590, Vol.189, pp.1-12, 2024Streszczenie: This paper addresses a challenging engineering problem that combines stress-limited topology optimization, reliability analysis, and plasticity-based low-cycle fatigue. Each of these issues represents a complex problem on its own, necessitating significant computational effort. In this study, we propose a novel approach that integrates safety assessment into the topology optimization process while considering the number of cycles for low-cycle fatigue. Our method employs a linear approximation of the performance function for safety control, incorporating the number of failure cycles within a complex, multi-level load program. The methodology is validated through real experiments, using a finite element model with cubic shape functions that yield nearly identical results between numerical and experimental outcomes in the case of fatigue-resistant design for a bi-axially tensioned structural joint. Słowa kluczowe: Topology optimization, stress constraints, Reliability analysis, low-cycle fatigue, fatigueplasticity Afiliacje autorów:
Tauzowski P. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Lógó J. | - | University of Technology and Economics (HU) |
| | 140p. |
4. |
Zabojszcza P.^{♦}, Radoń U.^{♦}, Tauzowski P., Robust Optimization of the Steel Single Story Frame,
Acta Polytechnica Hungarica, ISSN: 1785-8860, DOI: 10.12700/APH.21.1.2024.1.2, Vol.21, No.1, pp.9-29, 2024Streszczenie: In contemporary design practices, building structures are expected to not only meet safety requirements but also be optimized. However, optimal designs can be highly sensitive to random variations in model parameters and external actions. Solutions that appear effective under nominal conditions may prove inadequate when parameter randomness is considered. To address this challenge, the concept of robust optimization has been introduced, which extends deterministic optimization formulations to incorporate the random variability of parameter values. In this study, we demonstrate the applicability of robust optimization in the design of building structures using a simple orthogonal frame as an example. The static-strength analysis is conducted based on the displacement method, utilizing second-order theory. To assess the safety level of the steel frame, a preliminary evaluation is performed by determining the reliability index and failure probability using the Monte Carlo Method. Robust optimization is then employed, leveraging the second-order response surface. Experimental designs are generated following an optimal Latin hypercube plan. The proposal of a mathematical-numerical algorithm for solving the optimization problem while considering the random nature of design parameters constitutes the innovative aspect of this research. Słowa kluczowe: reliability, robust optimization, second order theory, displacement method Afiliacje autorów:
Zabojszcza P. | - | inna afiliacja | Radoń U. | - | inna afiliacja | Tauzowski P. | - | IPPT PAN |
| | 70p. |
5. |
Zabojszcza P.^{♦}, Radoń U.^{♦}, Tauzowski P., Robust and reliability-based design optimization of steel beams,
ARCHIVES OF CIVIL ENGINEERING, ISSN: 1230-2945, DOI: 10.24425/ace.2023.147651, Vol.69, No.4, pp.125-140, 2023Streszczenie: In line with the principles of modern design a building structure should not only be safe but also optimized. In deterministic optimization, the uncertainties of the structures are not explicitly taken into account. Traditionally, uncertainties of the structural system (i.e. material parameters, loads, dimensions of the cross-sections) are considered by means of partial safety factors specified in design codes. Worth noticing, that optimal structures are sensitive to randomness design parameters and deterministic optimal solutions may lead to reduced reliability levels. It therefore seems natural to extend the formulation of deterministic optimization with the random scatter of parameter values. Such a formulation is offered by robust optimization and reliability-based design optimization. The applicability of RBDO is strongly dependent on the availability of the joint probability density function. A formulation of non-deterministic optimization that better adapts to the design realities is robust optimization. Unlike RBDO optimization, this formulation does not require estimation of failure probabilities. In the paper using the examples of steel beams, the authors compare the strengths and weaknesses of both formulations.
Słowa kluczowe: first order reliability method, reliability index, reliability-based design optimization, robust optimization Afiliacje autorów:
Zabojszcza P. | - | inna afiliacja | Radoń U. | - | inna afiliacja | Tauzowski P. | - | IPPT PAN |
| | 140p. |
6. |
Moneta J.^{♦}, Staszczak G.^{♦}, Grzanka E.^{♦}, Tauzowski P., Dłużewski P., Smalc-Koziorowska J.^{♦}, Formation of a-type dislocations near the InGaN/GaN interface during post-growth processing of epitaxial structures,
JOURNAL OF APPLIED PHYSICS, ISSN: 0021-8979, DOI: 10.1063/5.0128514, Vol.133, pp.045304-1-045304-12, 2023Streszczenie: Cross-sectional transmission electron microscopy studies often reveal a-type dislocations located either below or above the interfaces in
InGaN/GaN structures deposited along the [0001] direction. We show that these dislocations do not emerge during growth but rather are a
consequence of the stress state on lateral surfaces and mechanical processing, making them a post-growth effect. In cathodoluminescence mapping, these defects are visible in the vicinity of the edges of InGaN/GaN structures exposed by cleaving or polishing. Finite element cal-culations show the residual stress distribution in the vicinity of the InGaN/GaN interface at the free edge. The stress distribution is discussed in terms of dislocation formation and propagation. The presence of such defects at free edges of processed devices based on InGaN layers may have a significant negative impact on the device performance. Słowa kluczowe: Luminescence ,Transmission electron microscopy ,Focused ion beam ,Semiconductor materials ,Epitaxy ,Crystal structure ,Crystal lattices ,Crystallographic defects,Mechanical stress,X-ray diffraction Afiliacje autorów:
Moneta J. | - | inna afiliacja | Staszczak G. | - | inna afiliacja | Grzanka E. | - | inna afiliacja | Tauzowski P. | - | IPPT PAN | Dłużewski P. | - | IPPT PAN | Smalc-Koziorowska J. | - | inna afiliacja |
| | 100p. |
7. |
Ostrowski M., Błachowski B., Wójcik B.^{♦}, Żarski M.^{♦}, Tauzowski P., Jankowski Ł., A framework for computer vision-based health monitoring of a truss structure subjected to unknown excitations,
Earthquake Engineering and Engineering Vibration, ISSN: 1993-503X, DOI: 10.1007/s11803-023-2154-3, pp.1-17, 2023Streszczenie: Computer vision (CV) methods for measurement of structural vibration are less expensive, and their application is more straightforward than methods based on sensors that measure physical quantities at particular points of a structure. However, CV methods produce significantly more measurement errors. Thus, computer vision-based structural health monitoring (CVSHM) requires appropriate methods of damage assessment that are robust with respect to highly contaminated measurement data. In this paper a complete CVSHM framework is proposed, and three damage assessment methods are tested. The first is the augmented inverse estimate (AIE), proposed by Peng et al. in 2021. This method is designed to work with highly contaminated measurement data, but it fails with a large noise provided by CV measurement. The second method, as proposed in this paper, is based on the AIE, but it introduces a weighting matrix that enhances the conditioning of the problem. The third method, also proposed in this paper, introduces additional constraints in the optimization process; these constraints ensure that the stiff ness of structural elements can only decrease. Both proposed methods perform better than the original AIE. The latter of the two proposed methods gives the best results, and it is robust with respect to the selected coefficients, as required by the algorithm. Słowa kluczowe: computer vision,structural health monitoring,physics-based graphical models,augmented inverse estimate,model updating,non-negative least square method Afiliacje autorów:
Ostrowski M. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Wójcik B. | - | Institute of Theoretical and Applied Informatics, Polish Academy of Sciences (PL) | Żarski M. | - | Institute of Theoretical and Applied Informatics, Polish Academy of Sciences (PL) | Tauzowski P. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
| | 70p. |
8. |
Błachowski B., Tauzowski P., Preface,
COMPUTER ASSISTED METHODS IN ENGINEERING AND SCIENCE, ISSN: 2299-3649, Vol.29, No.4, pp.295-296, 2022, EDITORIALStreszczenie: The contents of this special issue comprise four research papers devoted to engineering optimization, three of which were presented during the 2nd edition of the Workshop on Engineering Optimization (WEO-2021). The workshop was held in Warsaw, Poland, on October 7–8, 2021. Due to the COVID-19 pandemic, the 2021 edition of the workshop was organized in a hybrid form and was dedicated to the exchange of experiences in the field of engineering optimization including its theoretical and algorithmic aspects as well as practical applications. The workshop hosted six invited lectures and six thematic sessions. 21 presentations by authors from seven European and non-European countries (50% of them from outside Poland) were delivered.
Additionally, the organization of the second edition of WEO was supported by the project entitled Development of regional network on autonomous systems for structural health monitoring financed by the Visegrad Fund, under the grant agreement 22110360. More details on the workshop and the V4SHM project can be found on the following website: http://v4shm.ippt.pan.pl. Afiliacje autorów:
Błachowski B. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN |
| |
9. |
Tauzowski P., Błachowski B., Lógó J.^{♦}, Topology optimization of elasto-plastic structures under reliability constraints: a first order approach,
COMPUTERS AND STRUCTURES, ISSN: 0045-7949, DOI: 10.1016/j.compstruc.2020.106406, Vol.243, pp.106406-1-15, 2021Streszczenie: The objective of this study is to propose a relatively simple and efficient method for reliability based topology optimization for structures made of elasto-plastic material. The process of determining the optimal topology of elasto-perfectly plastic structures is associated with the removal of material from the structure. Such a process leads to weakening of structural strength and stiffness causing at the same time increase the likelihood of structural failure. An important aspect of engineering design is to track this probability during the optimization process and not allow the structure safety to exceed a certain level specified by the designer. The purpose of this work is to combine the previously developed yield-limited topology optimization method with reliability analysis using first order approach. Effectiveness of the proposed methodology is demonstrated on benchmark problems proposed by Rozvany and Maute, and the elasto-plastic topology design of L-shape structure which is frequently used in different approaches for stress constrained topology optimization. Słowa kluczowe: topology optimization, reliability analysis, elasto-plastic analysis Afiliacje autorów:
Tauzowski P. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Lógó J. | - | University of Technology and Economics (HU) |
| | 140p. |
10. |
Błachowski B., Świercz A., Ostrowski M., Tauzowski P., Olaszek P.^{♦}, Jankowski Ł., Convex relaxation for efficient sensor layout optimization in large‐scale structures subjected to moving loads,
Computer-Aided Civil and Infrastructure Engineering, ISSN: 1093-9687, DOI: 10.1111/mice.12553, Vol.35, No.10, pp.1085-1100, 2020Streszczenie: This paper proposes a computationally effective framework for load‐dependent optimal sensor placement in large‐scale civil engineering structures subjected to moving loads. Two common problems are addressed: selection of modes to be monitored and computational effectiveness. Typical sensor placement methods assume that the set of modes to be monitored is known. In practice, determination of such modes of interest is not straightforward. A practical approach is proposed that facilitates the selection of modes in a quasi‐automatic way based on the structural response at the candidate sensor locations to typical operational loads. The criterion used to assess sensor placement is based on Kammer's Effective Independence (EFI). However, in contrast to typical implementations of EFI, which treat the problem as a computationally demanding discrete problem and use greedy optimization, an approach based on convex relaxation is proposed. A notion of sensor density is applied, which converts the original combinatorial problem into a computationally tractable continuous optimization problem. The proposed framework is tested in application to a real tied‐arch railway bridge located in central Poland. Słowa kluczowe: optimal sensor placement, effective independence method, Fisher information matrix Afiliacje autorów:
Błachowski B. | - | IPPT PAN | Świercz A. | - | IPPT PAN | Ostrowski M. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Olaszek P. | - | Instytut Badawczy Dróg i Mostów (PL) | Jankowski Ł. | - | IPPT PAN |
| | 140p. |
11. |
Błachowski B.D.^{♦}, Tauzowski P.^{♦}, Lógó J.^{♦}, Yield limited optimal topology design of elastoplastic structures,
STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, ISSN: 1615-147X, DOI: 10.1007/s00158-019-02447-9, Vol.61, pp.1-24, 2020Streszczenie: This study is devoted to a novel method for topology optimization of elastoplastic structures subjected to stress constraints. It should be noted that in spite of the classical solutions of the different type of elastoplastic topology problems are more than 70 years old, the integration of the Prandtl-Reuss constitutive equations into the topology optimization process is not very often investigated in the last three decades. In the presented methodology where the classical variational principles of plasticity and the functor-oriented programming technique are applied in topology design, the aim is to find a minimum weight structure which is able to carry a given load, fulfills the allowable stress limit, and is made of a linearly elastic, perfectly plastic material. The optimal structure is found in an iterative way using only a stress intensity distribution and a return mapping algorithm. The method determines representative stresses at every Gaussian point, averages them inside every finite element using the von Mises yield criterion, and removes material proportionally to the stress intensities in individual finite elements. The procedure is repeated until the limit load capacity is exceeded under a given loading. The effectiveness of the methodology is illustrated with three numerical examples. Additionally, different topologies are presented for a purely elastic and an elastoplastic material, respectively. It is also demonstrated that the proposed method is able to find the optimal elastoplastic topology for a problem with a computational mesh of the order of tens of thousands of finite elements. Słowa kluczowe: topology optimization,elastoplastic structures,minimum-weight design,stress constraints Afiliacje autorów:
Błachowski B.D. | - | inna afiliacja | Tauzowski P. | - | inna afiliacja | Lógó J. | - | University of Technology and Economics (HU) |
| | 100p. |
12. |
Tauzowski P., Błachowski B., Lógó J.^{♦}, Functor-oriented topology optimization of elasto-plastic structures,
Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2019.102690, Vol.135, pp.102690-1-11, 2019Streszczenie: The paper deals with a novel approach to development of optimality criteria based finite element code for topology optimization of elasto-plastic structures. The novelty of this work is related to the concept of function object called functor and its application to efficient FE code development. First, the general problem of topology optimization under stress constraints is briefly formulated. Then, the programming aspects of topology optimization using traditional object-oriented and functor based programming are discussed. The advantages of the functor based approach are related to simplicity of designing the FE code architecture and reusability of this code. In particular the metric known as 'Lack of cohesion of methods' is useful in comparing these two different paradigms. Finally, the paper is also illustrated with numerical examples of topology optimization using the proposed methodology. Słowa kluczowe: topology optimization, function object, functor programming, optimal design, elasto-plastic structures, finite element programming Afiliacje autorów:
Tauzowski P. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Lógó J. | - | University of Technology and Economics (HU) |
| | 140p. |
13. |
Tauzowski P., Lógó J.^{♦}, Pintér E.^{♦}, Parametric Study on the Element Size Effect for Optimal Topologies,
Periodica Polytechnica Civil Engineering, ISSN: 0553-6626, DOI: 10.3311/PPci.11551, Vol.62, No.1, pp.267-276, 2018 | | 15p. |
14. |
Błachowski B., Tauzowski P., Lógó J.^{♦}, Modal Approximation Based Optimal Design of Dynamically Loaded Plastic Structures,
Periodica Polytechnica Civil Engineering, ISSN: 0553-6626, DOI: 10.3311/PPci.11016, Vol.61, No.4, pp.987-992, 2017Streszczenie: The purpose of this study is to present an optimal design procedure for elasto-plastic structures subjected to impact loading. The proposed method is based on mode approximation of the displacement field and assumption of constant acceleration of impacted structure during whole time of deformation process until the plastic displacement limit is reached. Derivation of the method begins with the application of the principle of conservation of linear momentum, followed by determination of inertial forces. The final stage of the method utilizes an optimization technique in order to find a minimum weight structure. Eventually, effectiveness and usefulness of the proposed method is demonstrated on the example of a planar truss structure subjected to dynamic loading caused by a mass impacting the structure with a given initial velocity. Słowa kluczowe: structural dynamics, optimal design, elasto-plastic structures, short-time dynamic loading Afiliacje autorów:
Błachowski B. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Lógó J. | - | University of Technology and Economics (HU) |
| | 15p. |
15. |
Lasota R., Stocki R.^{♦}, Tauzowski P., Szolc T., Polynomial chaos expansion method in estimating probability distribution of rotor-shaft dynamic responses,
BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.1515/bpasts-2015-0047, Vol.63, No.2, pp.413-422, 2015Streszczenie: The main purpose of the study is an assessment of computational efficiency of selected numerical methods for estimation of vibrational response statistics of a large multi-bearing turbo-generator rotor-shaft system. The effective estimation of the probability distribution of structural responses is essential for robust design optimization and reliability analysis of such systems. The analyzed scatter of responses is caused by random residual unbalances as well as random stiffness and damping parameters of the journal bearings. A proper representation of these uncertain parameters leads to multidimensional stochastic models. Three estimation techniques are compared: Monte Carlo sampling, Latin hypercube sampling and the sparse polynomial chaos expansion method. Based on the estimated values of the first four statistical moments the probability density function of the maximal vibration amplitude is evaluated by the maximal entropy principle method. The method is inherently suited for an accurate representation of the probability density functions with an exponential behavior, which appears to be characteristic for the investigated rotor-shaft responses. Performing multiple numerical tests for a range of sample sizes it was found that the sparse polynomial chaos method provides the best balance between the accuracy and computational effectiveness in estimating the unknown probability distribution of the maximal vibration amplitude. Słowa kluczowe: stochastic moment estimation, sparse polynomial chaos expansion, maximum entropy principle, rotor, uncertainties, hybrid mechanical model, random unbalance distribution Afiliacje autorów:
Lasota R. | - | IPPT PAN | Stocki R. | - | inna afiliacja | Tauzowski P. | - | IPPT PAN | Szolc T. | - | IPPT PAN |
| | 20p. |
16. |
Kowalczyk P., Rojek J., Stocki R., Bednarek T., Tauzowski P., Lasota R., Lumelskyj D., Wawrzyk K.^{♦}, NUMPRESS − integrated computer system for analysis and optimization of industrial sheet metal forming processes,
HUTNIK - WIADOMOŚCI HUTNICZE, ISSN: 1230-3534, Vol.81, No.1, pp.56-63, 2014Streszczenie: The NUMPRESS System has been developed in IPPT PAN as a result of a project financially supported by European Regional Development Fund (within the Innovative Economy Programme) and is dedicated to small and middle enterprises dealing with sheet metal forming. The program consists of (i) an analytical module for analysis of forming processes with the finite element method, (ii) an optimization module controlling execution of the analytical module and performing optimization with respect to selected process parameters, in both deterministic and robust formulation, (iii) a reliability analysis module controlling execution of the analytical module to assess how random distribution of design parameters affects forming results, and (iv) a graphical user interface enabling communication between modules and easy definition of design parameters and optimization criteria. The analytical module consists of two independent programs up to the user's choice: NUMPRESS-Flow, a faster and less accurate program for implicit quasi-static analysis of rigid-viscoplastic shells (based on the flow approach) and NUMPRESS-Explicit, a program for explicit dynamical analysis of elastic-plastic and elastic-viscoplastic shells. Both programs are interfaced to a well-known commercial graphical pre- and postprocessor GiD. Fundamentals of formulations employed in the system and numerical examples are presented in the paper. Słowa kluczowe: sheet metal forming, finite element method, deterministic and robust design optimization, reliability analysis Afiliacje autorów:
Kowalczyk P. | - | IPPT PAN | Rojek J. | - | IPPT PAN | Stocki R. | - | IPPT PAN | Bednarek T. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Lasota R. | - | IPPT PAN | Lumelskyj D. | - | IPPT PAN | Wawrzyk K. | - | inna afiliacja |
| | 6p. |
17. |
Stocki R., Szolc T., Tauzowski P., Knabel J., Robust design optimization of the vibrating rotor shaft system subjected to selected dynamic constraints,
MECHANICAL SYSTEMS AND SIGNAL PROCESSING, ISSN: 0888-3270, DOI: 10.1016/j.ymssp.2011.07.023, Vol.29, pp.34-44, 2012Streszczenie: The commonly observed nowadays tendency to weight minimization of rotor-shafts of the rotating machinery leads to a decrease of shaft bending rigidity making a risk of dangerous stress concentrations and rubbing effects more probable. Thus, a determination of the optimal balance between reducing the rotor-shaft weight and assuring its admissible bending flexibility is a major goal of this study. The random nature of residual unbalances of the rotor-shaft as well as randomness of journal-bearing stiffness have been taken into account in the framework of robust design optimization. Such a formulation of the optimization problem leads to the optimal design that combines an acceptable structural weight with the robustness with respect to uncertainties of residual unbalances – the main source of bending vibrations causing the rubbing effects. The applied robust optimization technique is based on using Latin hypercubes in scatter analysis of the vibration response. The so-called optimal Latin hypercubes are used as experimental plans for building kriging approximations of the objective and constraint functions. The proposed method has been applied for the optimization of the typical single-span rotor-shaft of the 8-stage centrifugal compressor. Słowa kluczowe: Rotor-shaft system, Robust design optimization, Lateral vibrations, Rubbing effects, Random unbalance distribution Afiliacje autorów:
Stocki R. | - | IPPT PAN | Szolc T. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Knabel J. | - | IPPT PAN |
| | 45p. |
18. |
Stocki R., Lasota R., Tauzowski P., Szolc T., Scatter assessment of rotating system vibrations due to uncertain residual unbalances and bearing properties,
COMPUTER ASSISTED METHODS IN ENGINEERING AND SCIENCE, ISSN: 2299-3649, Vol.19, pp.95-120, 2012Streszczenie: The main objective of the presented study is an evaluation of the effectiveness of various methods for estimating statistics of rotor-shaft vibration responses. The computational effectiveness as well as the accuracy of statistical moment estimation are essential for efficient robust design optimization of the rotor-shaft systems. The compared methods include sampling techniques, the perturbation approach, the dimension reduction method and the polynomial chaos expansion method. For comparison, two problems of the rotor-shaft vibration analysis are considered: a typical single-span rotor-shaft of the 8-stage centrifugal compressor driven by the electric motor and a large multi-bearing rotor-shaft system of the steam turbo-generator. The most important reason for the observed scatter of the rotor-shaft vibration responses is the inherently random nature of residual unbalances as well as stiffness and damping properties of the journal bearings. A proper representation of these uncertain parameters leads to multidimensional stochastic models. It was found that methods that provide a satisfactory balance between the estimation accuracy and computational effectiveness are sampling techniques. On the other hand, methods based on Taylor series expansion in most of the analysed cases fail to approximate the rotor-shaft response statistics. Słowa kluczowe: Scatter analysis, rotor-shaft vibrations Afiliacje autorów:
Stocki R. | - | IPPT PAN | Lasota R. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Szolc T. | - | IPPT PAN |
| | 6p. |
19. |
Lógó J.^{♦}, Movahedi Rad M.^{♦}, Knabel J., Tauzowski P., Reliability based design of frames with limited residual strain energy capacity,
Periodica Polytechnica Civil Engineering, ISSN: 0553-6626, Vol.55, No.1, pp.13-20, 2011Streszczenie: The aim of this paper is to create new type of plastic limit design procedures where the influence of the limited load carrying capacity of the beam-to-column connections of elasto-plastic steel (or composite) frames under multi-parameter static loading and probabilistically given conditions are taken into consideration. In addition to the plastic limit design to control the plastic behaviour of the structure, bound on the complementary strain energy of the residual forces is also applied. If the design uncertainties (manufacturing, strength, geometrical) are taken into consideration at the computation of the complementary strain energy of the residual forces the reliability based extended plastic limit design problems can be formed. Two numerical procedures are elaborated. The formulations of the problems yield to nonlinear mathematical programming which are solved by the use of sequential quadratic algorithm. Słowa kluczowe: reliability analysis, limit analysis, residual strain energy, Monte Carlo simulation, optimal design Afiliacje autorów:
Lógó J. | - | University of Technology and Economics (HU) | Movahedi Rad M. | - | University of Technology and Economics (HU) | Knabel J. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN |
| |
20. |
Szolc T., Tauzowski P., Knabel J., Stocki R., Nonlinear and parametric coupled vibrations of the rotor-shaft system as fault identification symptom using stochastic methods,
NONLINEAR DYNAMICS, ISSN: 0924-090X, Vol.57, pp.533-557, 2009Streszczenie: In the paper several stochastic methods for detection and identification of cracks in the shafts of rotating machines are proposed. All these methods are based on the Monte Carlo simulations of the rotor-shaft lateral-torsional-longitudinal vibrations mutually coupled by transverse cracks of randomly selected depths and locations on the shaft. For this purpose there is applied a structural hybrid model of a real cracked rotor-shaft. This model is characterized by a high practical reliability and great computational effi-ciency, so important for hundreds of thousands numerical simulations necessary to build databases used in solving the inverse problem, i.e. crack parameter identifications. In order to ensure a good identification accuracy, for creating the Monte Carlo samples of data points there are proposed special probability density functions for locations and depths of the crack. Such an approach helps in enhancing databases corresponding to the most probable faults of the rotor-shaft system of the considered rotor machine. In the presentedstudy six different database sizes are considered to compare identification efficiency and accuracy of considered methods. A sufficiently large database enables us to estimate almost immediately (usually in less than one second) the crack parameters with precision that is in most of the cases acceptable in practice. Then, as a next stage, one of the proposed fast improvement algorithms can be applied to refine identification results in a reasonable time. The proposed methods seem to provide very convenient diagnostic tools for industrial applications. Słowa kluczowe: Crack rotor dynamics, Nonlinear and parametric vibrations, Hybrid modeling, Monte Carlo simulation, Crack identification methods Afiliacje autorów:
Szolc T. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Knabel J. | - | IPPT PAN | Stocki R. | - | IPPT PAN |
| | 32p. |
21. |
Szolc T., Tauzowski P., Stocki R., Knabel J., Damage identification in vibrating rotor-shaft systems by efficient sampling approach,
MECHANICAL SYSTEMS AND SIGNAL PROCESSING, ISSN: 0888-3270, Vol.23, pp.1615-1633, 2009Streszczenie: In the paper a stochastic method for fault detection and identification in the shafts of rotating machines is proposed. This approach is based on the Monte Carlo simulations of rotor-shaft lateral–torsional–longitudinal vibrations mutually coupled by transverse cracks of various possible and randomly selected depths and locations on the shaft. For this purpose the structural hybrid model of a real faulty object is applied. This model is characterized by a high practical reliability and great computational efficiency, so important for many hundred thousand single numerical simulations necessary for a creation of the databases applied for inverse problem solution finally leading to crack identification. These databases are created with an arbitrary assumed probability densities of crack parameters which ensures appropriate spread of the dynamic responses of the considered faulty mechanical system. A sufficiently large database determined for the investigated object enable us to estimate almost immediately, i.e. within less than 1 s, the crack depth and axial position with identification errors not exceeding 9% and 5%, respectively. Thus, the proposed method seems to be a very convenient diagnostic tool for engineering applications in the industry. Słowa kluczowe: Rotor-shaft system, Dynamic diagnostics, Crack identification, Monte Carlo simulation, Coupled vibration analysis Afiliacje autorów:
Szolc T. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Stocki R. | - | IPPT PAN | Knabel J. | - | IPPT PAN |
| | 32p. |
22. |
Stocki R., Kolanek K., Knabel J., Tauzowski P., FE based structural reliability analysis using STAND environment,
COMPUTER ASSISTED METHODS IN ENGINEERING AND SCIENCE, ISSN: 2299-3649, Vol.16, pp.35-58, 2009Streszczenie: An assessment of structural reliability requires multiple evaluations of the limit state function for various realizations of random parameters of the structural system. In the majority of industrial applications the limit state functions cannot be expressed explicitly in terms of the random parameters but they are specified using selected outcomes of the FE analysis. In consequence, in order to be useful in practice, a structural reliability analysis program should be closely integrated with a FE module or it should be interfaced with an advanced external FE program. When the FE source code is not available, which is usually the case, the only option is to establish a communication between the reliability analysis program and an external FE software through the batch mechanism of data modification, job submission and results extraction. The main subject of this article is to present the reliability analysis capabilities of STAND software, which is being developed in the Institute of Fundamental Tech no logical Research of Polish Academy of Sciences. A special emphasis is put on the issues related to it s interfacing with external general purpose FE codes. It is shown that when shape type random variables are used, leading to modifications of the FE mesh, or when the limit state function contains numerical noise, standard algorithms for localizing the design point often fail to converge and a special method based on some response surface approximation is needed. A proposition of such a strategy that employs an adaptive response surface approximation of the limit state function is presented in this article. Development of a reliability analysis program is a challenging project and calls for such a code organization, which would facilitate a simultaneous work of many programmers and allow for easy maintenance and modifications. The so-called object-oriented programming seems to provide a convenient framework to realize these objectives. The object-oriented approach is used in STAND development. The advantages of this programming paradigm and a short description of the STAND’s class hierarchy are presented in the text. The study is concluded with two numerical examples of interfacing STAND with state of the art commercial FE programs. Słowa kluczowe: Reliability, optimization software Afiliacje autorów:
Stocki R. | - | IPPT PAN | Kolanek K. | - | IPPT PAN | Knabel J. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN |
| | 6p. |
23. |
Movahedi Rad M.^{♦}, Lógó J.^{♦}, Knabel J., Tauzowski P., Reliability based limit design of frames with limited residual strain energy capacity,
Proceedings in Applied Mathematics and Mechanics, ISSN: 1617-7061, DOI: 10.1002/pamm.200910323, Vol.9, pp.709-710, 2009Streszczenie: The aim of this paper is to take into consideration the influence of the limited load carrying capacity of the connections on the plastic limit state of elasto-plastic steel (or composite) framed structures under multi-parameter stochastic loading and probabilistically given conditions. In addition to the plastic limit design to control the plastic behaviour of the structure, bound on the complementary strain energy of the residual forces is also applied. This bound has significant effect for the load parameter. If the design uncertainties (manufacturing, strength, geometrical) are expressed by the calculation of the complementary strain energy of the residual forces a reliability based extended limit design problem is formed. The formulations of the problems yield to nonlinear mathematical programming which are solved by the use of sequential quadratic algorithm. The bi-level optimization procedure governed by the reliability index calculation. Słowa kluczowe: limit analysis of frames, reliability analysis, optimization Afiliacje autorów:
Movahedi Rad M. | - | University of Technology and Economics (HU) | Lógó J. | - | University of Technology and Economics (HU) | Knabel J. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN |
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24. |
Stocki R., Tauzowski P., Knabel J., Reliability analysis of a crashed thin-walled s-rail accounting for random spot weld failures,
INTERNATIONAL JOURNAL OF CRASHWORTHINESS, ISSN: 1358-8265, DOI: 10.1080/13588260802055213, Vol.13, No.6, pp.693-706, 2008Streszczenie: Possibly the most common application of spot welding is in the automobile manufacturing industry, where it is almost universally used to weld the sheet-metal car components. However, due to manufacturing inaccuracies and fatigue failures an important number of spot welds may be missing in an operational vehicle. It seems that to properly analyse the reliability of such structures, in particular crashworthiness reliability, the spot weld failures must be considered. Representing properties of each spot weld in a stochastic model by corresponding random variables is extremely inefficient. Therefore, in this article an approach is proposed for handling spot-weld defects in the reliability analysis by accounting for their averaged influence on a failure criterion. The approach consists of the appropriate treatment of a random noise component of the limit state function. The noise results from the strategy of deleting a certain number of randomly selected spot-weld elements from the finite element model each time the limit state function value is computed. Dealing with noisy limit state functions in structural reliability analysis is a challenging task. The only method that seems to be insensitive to this phenomenon is Monte Carlo sampling, which for most of the applications of practical interest is prohibitively expensive. Having this in mind, a method based on the algorithm proposed by Zou et al. and published in the journal of Reliability Engineering and System Safety in 2002 is investigated in this article. The method combines the best features of the first-order reliability method, the response surface technique and the importance sampling method to achieve both accuracy and efficiency. A detailed study on the reliability of thin-walled s-rail subjected to crash is performed. Some suggestions concerning the modification of the original algorithm are proposed.
Słowa kluczowe: crashworthiness reliability, response surface approximation, adaptive importance sampling, spot weld failures Afiliacje autorów:
Stocki R. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Knabel J. | - | IPPT PAN |
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25. |
Tauzowski P., Kleiber M., Parameter and shape sensitivity of thermo-viscoelastic response,
COMPUTERS AND STRUCTURES, ISSN: 0045-7949, DOI: 10.1016/j.compstruc.2005.09.026, Vol.84, pp.385-399, 2006Streszczenie: Gradient-based optimization methods are still most efficient methods for solving structural optimization problems. The sensitivity formulation has been one of the central issues in the gradient-based optimization algorithm. Thermo-viscoelastic constitutive and parameter sensitivity formulation are presented in this paper. The model considered is composed of two coupled subproblems: the transient heat transfer problem and a rheological, viscoelastic material model known in literature as the standard model. Design variables considered are with material and shape-defining parameters. The investigation includes a finite element formulation and implementation in an object-oriented finite element environment. Results of numerical analysis are presented. Słowa kluczowe: Finite element method, Sensitivity analysis, Viscoelasticity Afiliacje autorów:
Tauzowski P. | - | IPPT PAN | Kleiber M. | - | IPPT PAN |
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