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1
Content available Reinforcement layout design of three-dimensional members under a state of complex stress
Cui Hao, Xia Junjie, Wu Lang, Xiao Min
Archives of Civil Engineering
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2023
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Vol. 69, nr 1
421--436
EN
This paper proposes a method to optimize reinforcement layout of three-dimensional members under a state of complex stress and multiple load cases (MLCs). To simulate three-dimensional members, the spatial truss-like material model is adopted. Three families of truss-like members along orthotropic directions are embedded continuously in concrete. The optimal reinforcement layout design is obtained by optimizing the member densities and orientations. The optimal design of three-dimensional member is carried out by solving the problem of minimum volume of reinforcing bars with stress constraints. Firstly, the optimized reinforcement layout under each single load case (SLC) is obtained as per the fully stressed criterion. Second, on the basis of the previous results, an equivalent multi-case optimization is proposed by introducing the idea of stiffness envelope. Finally, according to the characteristics of the truss-like material, a closed and symmetrical surface is adopted to fit the maximum directional stiffness under all SLCs. It can be proved that the densities and orientations of truss-like members are the eigenvalues and eigenvectors of the surface coefficient matrix, respectively. Several three-dimensional members are used as examples to demonstrate the capability of the proposed method in finding the best reinforcement layout design of each reinforced concrete (RC) member and to verify its efficiency in application to real design problems.
2
Content available Endurance limit of the axial-piston hydraulic machine cylinder block
Khomiak Yuriy, Kibakov Oleksandr, Medvedev Stanislav, Nikolenko Ilya, Zheglova Victoria
Diagnostyka
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2020
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Vol. 21, No. 1
71--79
EN
The fatigue resistance of the cylinder block (CB) of an axial-piston hydraulic machine (APHM) made of tin bronze CuSn12 has been investigated. Fatigue tests of smooth and notched standard samples were performed and fatigue curves were constructed. The stress state of the CB is investigated by the finite element method. It is established that the maximum stresses are localized on a small part of the partition between axial cylinders holes loaded by internal pressure. A method for recalculating the established length of this zone of partition with an uneven distribution of dangerous stresses by an equivalent length with a constant stress equal to the maximum is proposed. The use of the statistical theory of the similarity of the fatigue failure of Serensen-Kogayev, the results of the fatigue tests of the samples and the calculation of the equivalent length made it possible to determine the endurance limit of the CB considered. The acceptability of the proposed method estimating the endurance limit by the known results of resource tests of the CB APHM 210.25 is confirmed.
3
Content available Symulacja plastycznego zakresu pracy stali konstrukcyjnych w złożonym stanie naprężeń w oparciu o model Gursona-Tvergaarda-Needelmana
Kossakowski P.
Przegląd Budowlany
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2012
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R. 83, nr 3
43-49
PL
Analiza stanów plastycznych jest zagadnieniem często podejmowanym zarówno w badaniach naukowych jak i zwykłej praktyce inżynierskiej. Tematyka ta jest szczególnie aktualna w odniesieniu do konstrukcji budowlanych w kontekście katastrof, które ostatnio miały miejsce w Polsce. Zagadnieniom tym jest poświęcony niniejszy artykuł, w którym przybliżono procedury związane z numerycznym modelowaniem pracy elementów w złożonych stanach naprężenia w zakresie plastycznym.
EN
The analysis of plastic states is frequently undertaken both in scientific research and in ordinary engineering practice. The topic is a particularly current one in relation to building structures, in the light of recent disasters which have occurred in Poland. These issues are discussed in this article, which describes procedures relating to the numerical modelIing of plastic behaviour of elements under complex stresses.
4
Content available Modelling S235JRG2 steel load-carrying capacity and micro-damage development for static and quasi-static loads
Wcislik W.
Challenges of Modern Technology
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2011
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Vol. 2, no. 3
58--61
EN
This paper deals with the analysis of plastic deformation and damage development in S235JRG2 steel in complex stress states and at different rates of loading. The material Gurson Tvergaard Needleman (GTN) model was applied. The analysis was performed for notched bars subjected to tension. An attempt was made to investigate the impact of load conditions on the value of critical void volume fraction (fc) in the GTN model. Numerical computations carried out with the use of GTN model made it possible to identify the sites of ductile fracture initiation.
5
Content available Material responses to the laboratory simulation of complex cyclic loadings
Szymczak T., Kowalewski Z. L., Rutecka A.
Journal of KONES
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2008
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Vol. 15, No. 3
509-516
EN
The paper presents investigations identifying an influence of complex cyclic loading controlled by the strain signals on the selected mechanical properties of the 2024 aluminium alloy. Investigations of proportional and non-proportional loading paths in the form of square and circle were carried out at room temperature using thin-walled tubular specimens enabling realisation of complex stress states due to acting of axial force and twisting moment. The hardening effect of the material due to cyclic loading was observed on the basis of: stress responses into the strain controlled loading programme; hysteresis loop variations and amounts of stress amplitude. In the case of the non-proportional cyclic loading an additional hardening effect was identified. Second-order effects, which allow better understanding of the influence of proportional and non-proportional loading paths on mechanical behaviour of engineering materials, were identified. In the case of the circular loading path a delay of the maximum stress signals with respect to strain ones is demonstrated. For the square loading path a softening effect was observed. It is reflected by the rapid stress drop on this direction, which is perpendicular to that where the stress level begins to turn back. The yield surface approach is also applied in order to assess the mechanical properties variations due to cyclic loading of the material.
6
Content available remote Numerical models of masonry based experimental data
Szojda L., Wandzik G.
Architecture Civil Engineering Environment
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2008
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Vol. 1, no. 1
113-122
PL
Zamierzeniem autorów było zdefiniowanie powierzchni granicznej dla muru w celu zastosowania jej w systemie komputerowym do nieliniowych analiz metodą elementów skończonych. W artykule przedstawiono wyniki trójosiowych i jednoosiowych badań cegły i zaprawy. Stanowiły one podstawę do wyznaczenia położenia powierzchni granicznych tych materiałów w przestrzeni naprężeń. Zaprezentowano również rezultaty badań laboratoryjnych standardowych murków poddanych ściskaniu. Zostały one uzupełnione symulacją komputerową z wykorzystaniem systemu Mafem3d przeznaczonego do nieliniowej analizMES. Analizie numerycznej poddano mur, w którym cechy poszczególnych materiałów były modelowane niezależnie (model heterogeniczny). Wykonano również obliczenia takiej samej próbki muru z użyciem homogenicznego modelu materiałowego. Kształt powierzchni granicznej homogenicznego modelu materiałowego muru określony został na podstawie wyników badań eksperymentalnych materiałów składowych oraz wyników uzyskanych dla próbek muru. Przeprowadzono weryfikację zgodności wyników obliczeń dla modeli heterogenicznego i homogenicznego z wynikami doświadczalnymi. Stworzenie homogenicznego modelu materiałowego muru wynikało z potrzeby jego zastosowania w nieliniowej analizie większych obiektów wykonanych z cegły, gdzie występuje konieczność tworzenia elementów skończonych o wymiarach większych od wymiarów cegieł i spoin.
EN
The authors’ intention was to define the failure surface for the masonry for its further use in computational system for nonlinear finite element method analysis. Results of triaxial and uniaxial experimental tests for brick and mortar have been presented in the paper. These results were used as a basis for determination of the failure surfaces in stress space for both materials. Simultaneously, results of laboratory experiments carried out on standard masonry specimens under compression have been presented. These tests were supplemented with computational simulation performed with the use of nonlinear FEM analysis system Mafem3D. Masonry specimen was numerically analysed with use of individual mathematical description of brick and mortar behaviour (heterogeneous model). Calculation of the same specimen with the use of homogeneous material model have been carried out. Shape of the failure surface for homogeneous model was derived from the experimental test results for components (brick and mortar) and masonry specimens. Verification of simulation (made with the use of heterogeneous and homogeneous models as well) results with experimental data was done. Homogeneous material model was formulated because of the necessity of its use in nonlinear FEM analysis of real-scale masonry structures, where size of finite elements exceeds the size of singular masonry units (bricks and joints).
7
Content available remote Wpływ pełzania i plastycznego płynięcia na zachowanie miedzi w złożonym stanie naprężenia
Kowalewski Z. L.
Zeszyty Naukowe Politechniki Białostockiej. Mechanika
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2001
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Z. 24
254--264
PL
W pracy dokonano porównania zmian właściwości mechanicznych miedzi wywołanych deformacją plastyczną i procesem pełzania. Analizę przeprowadzono na podstawie ewolucji kształtu i położenia pierwotnej powierzchni plastyczności.
EN
Variations of mechanical properties of copper are compared for the material after both the plastic deformation at room temperature and the creep deformation at elevated temperature. An analysis is carried out on the basis of the initial yield surface evolution.
8
Content available remote Ocena wytrzymałości polipropylenu w złożonym stanie naprężeń
Plewa M
Zeszyty Naukowe Politechniki Białostockiej. Mechanika
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1998
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Z. 20
197-213
PL
W pracy przedstawiono badanie wytrzymałości rurkowych próbek z polipropylenu przy jednoosiowym rozciąganiu i obciążeniu ciśnieniem. Próby prowadzono na specjalnym stanowisku badawczym. Uzyskane wyniki eksperymentu wykorzystano do oceny przydatności hipotez HMH i Treski do opisu wytrzymałości badanego tworzywa w złożonym stanie naprężeń.
EN
The paper presents the strength investigation of polypropylene. The tubular specimens are tested under axial force and internal pressure. The results of the experiments have been used to evoluate applicability of von Mises and Treska criteria to descrite the strength of the material under investigation under complex stress states.
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