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1 – 10 of over 1000Dragan D. Milašinović, Ljiljana Kozarić, Smilja Bursać, Miroslav Bešević, Ilija Miličić and Đerđ Varju
The purpose of this paper is to contribute to the solution of the buckling and resonance stability problems in inelastic beams and wooden plane trusses, taking into account…
Abstract
Purpose
The purpose of this paper is to contribute to the solution of the buckling and resonance stability problems in inelastic beams and wooden plane trusses, taking into account geometric and material defects.
Design/methodology/approach
Two sources of non-linearity are analyzed, namely the geometrical non-linearity due to geometrical imperfections and material non-linearity due to material defects. The load-bearing capacity is obtained by the rheological-dynamical analogy (RDA). The RDA inelastic theory is used in conjunction with the damage mechanics to analyze the softening behavior with the scalar damage variable for stiffness reduction. Based on the assumed damages in the wooden truss, the corresponding external masses are calculated in order to obtain the corresponding fundamental frequencies, which are compared with the measured ones.
Findings
RDA theory uses rheology and dynamics to determine the structures' response, those results in the post-buckling branch can then be compared by fracture mechanics. The RDA method uses the measured P and S wave velocities, as well as fundamental frequencies to find material properties at the limit point. The verification examples confirmed that the RDA theory is more suitable than other non-linear theories, as those proved to be overly complex in terms of their application to the real structures with geometrical and material defects.
Originality/value
The paper presents a novel method of solving the buckling and resonance stability problems in inelastic beams and wooden plane trusses with initial defects. The method is efficient as it provides explanations highlighting that an inelastic beam made of ductile material can break in any stage from brittle to extremely ductile, depending on the value of initial imperfections. The characterization of the internal friction and structural damping via the damping ratio is original and effective.
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S. Belesis and G. Labeas
The purpose of this paper is to present an efficient engineering methodology for solving the problem of non‐linear (NL) damage and post‐buckling of large‐scale structures, which…
Abstract
Purpose
The purpose of this paper is to present an efficient engineering methodology for solving the problem of non‐linear (NL) damage and post‐buckling of large‐scale structures, which is of high importance mainly for the aircraft industry.
Design/methodology/approach
The methodology takes advantage of the capabilities of finite element substructuring technique in the simulation of large/complex structures and exploits the advantages of local‐global analysis logic. The main innovation deals with the appropriate modification of superelement method, such that it can deal with NL behaviour and efficiently model the entire large‐scale structure. In this study, the proposed methodology is demonstrated in the treatment of geometrical non‐linearity and its efficiency is assessed in the case of a large‐scale fuselage section.
Findings
A method capable of solving large‐scale NL problems by taking advantage of the linear response of the different model regions is developed.
Research limitations/implications
Further development of the proposed method is required for handling other means of non‐linearity.
Originality/value
The proposed approach is advantageous in terms of computational effort over the corresponding conventional ones.
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Zhe Yuan and Shihui Huo
Reinforced S-shape bellows are novel metal bellows with high pressure resistance. Displacement compensation ability is a key index in the design of metal bellows…
Abstract
Purpose
Reinforced S-shape bellows are novel metal bellows with high pressure resistance. Displacement compensation ability is a key index in the design of metal bellows. Axial-tension-compression deformation and bending deformation are two typical displacement compensation forms. Thus, analysis of axial and bending stiffness is important in structure design.
Design/methodology/approach
In this study, theory analytics of axial tension and compression stiffness of reinforced S-shaped bellows structure is derived, and the load-displacement relationship during axial deformation is obtained by correcting the geometric parameters of waveform during axial tension and compression deformations. On the basis of them, the relationships of bending stiffness with axial tensile and compression stiffness under the action of bending loading are constructed, and thus, the theory analytics of bending stiffness is realized for S-shaped bellows.
Findings
This theory analytics is verified by comparing the results of theory analytics with those of numerical simulation for a few typical examples. An investigation on the axial and bending non-linear mechanical behaviors of multi-layer-reinforced S-shaped bellows was also carried out by numerical simulation and experiment, and the experimental results verified the reliability of the analysis method.
Originality/value
It is found that non-linearity behavior occurs greatly during the first loading course of reinforced S-shaped bellows, and the structure is strain-strengthened due to plastic deformation; however, stable stiffness characteristic is exhibited during the succeeding cyclic-loading course.
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Lokamanya Chikmath, M.N. Ramanath, Syed Imtiaz and H. Murthy
This paper aims to study the benefits of use of bi-adhesive (combination of two different adhesives) over conventional single adhesive in bonded lap joints. Characterise damage…
Abstract
Purpose
This paper aims to study the benefits of use of bi-adhesive (combination of two different adhesives) over conventional single adhesive in bonded lap joints. Characterise damage severity due to cohesive and adherent failure as feedback for operating load levels that assist in developing damage tolerance design of the adhesively bonded joints.
Design/methodology/approach
Single lap joint where the adherent plate is made up of aluminium alloy joined together with bi-adhesives is analysed. The nature of adhesives ranges from brittle, elastic-plastic, moderately ductile to largely ductile. Numerical analysis is performed considering the material and geometric non-linear behaviour of the joint. The optimum bond ratio of bi-adhesives and the effect of the location of adhesive on the stress distribution are studied. The cohesive zone modelling (CZM) is adopted to account for the cohesive failure of the joint. The adherent plate failure is also addressed by modelling and studying the behaviour of the crack at different locations in the plate using modified virtual crack closure integral (MVCCI).
Findings
The results obtained from the stress analysis show some important characteristic behaviour of the bi-adhesive joint. Although bi-adhesive is expected to result in improved joint strength, the purpose gets defeated if a brittle adhesive is used at the corners and ductile adhesive at the middle. The joint strength based on CZM, evaluated for a single adhesive, is in good comparison with the experimental results from the literature. Also, the location of the crack in the adherent plate plays a significant role in the failure of the joint.
Originality/value
Estimating joint strength for the bi-adhesive model using CZM and evaluating damage severity in the presence of de-bond and crack in the bi-adhesive lap joint model assists in developing robust damage tolerance design models of such joints.
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Mica Grujicic, Subrahmanian Ramaswami, Jennifer Snipes, Ramin Yavari, Gary Lickfield, Chian-Fong Yen and Bryan Cheeseman
A series of all-atom molecular-level computational analyses is carried out in order to investigate mechanical transverse (and longitudinal) elastic stiffness and strength of p…
Abstract
Purpose
A series of all-atom molecular-level computational analyses is carried out in order to investigate mechanical transverse (and longitudinal) elastic stiffness and strength of p-phenylene terephthalamide (PPTA) fibrils/fibers and the effect various microstructural/topological defects have on this behavior. The paper aims to discuss these issues.
Design/methodology/approach
To construct various defects within the molecular-level model, the relevant open-literature experimental and computational results were utilized, while the concentration of defects was set to the values generally encountered under “prototypical” polymer synthesis and fiber fabrication conditions.
Findings
The results obtained revealed: a stochastic character of the PPTA fibril/fiber strength properties; a high level of sensitivity of the PPTA fibril/fiber mechanical properties to the presence, number density, clustering and potency of defects; and a reasonably good agreement between the predicted and the measured mechanical properties.
Originality/value
When quantifying the effect of crystallographic/morphological defects on the mechanical transverse behavior of PPTA fibrils, the stochastic nature of the size/potency of these defects was taken into account.
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Wenhua Ling and Henryk K. Stolarski
Some frictional contact problems are characterized by significant variations in the location and size of the contact area occurring in the process of deformation. When this…
Abstract
Some frictional contact problems are characterized by significant variations in the location and size of the contact area occurring in the process of deformation. When this feature is combined with strongly non‐linear, path‐dependent material behaviour, difficulties with convergence of the typically used iterative processes can be encountered. Demonstrates this by analysis of press‐fit connection, a typical problem in which both of those characteristics can be present. Offers an explanation as to the possible source of those difficulties. Suggests in support of this explanation, two simple modifications of the usual iterative schemes. In spite of their simplicity, they are found to be more robust than those usual schemes which are normally used in numerical analysis of similar problems.
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ZHI‐HUA ZHONG and JAROSLAV MACKERLE
Contact problems are among the most difficult ones in mechanics. Due to its practical importance, the problem has been receiving extensive research work over the years. The finite…
Abstract
Contact problems are among the most difficult ones in mechanics. Due to its practical importance, the problem has been receiving extensive research work over the years. The finite element method has been widely used to solve contact problems with various grades of complexity. Great progress has been made on both theoretical studies and engineering applications. This paper reviews some of the main developments in contact theories and finite element solution techniques for static contact problems. Classical and variational formulations of the problem are first given and then finite element solution techniques are reviewed. Available constraint methods, friction laws and contact searching algorithms are also briefly described. At the end of the paper, a bibliography is included, listing about seven hundred papers which are related to static contact problems and have been published in various journals and conference proceedings from 1976.
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Bernhard A. Schrefler, Carmelo E. Majorana, Gabriel A. Khoury and Dariusz Gawin
This paper presents the physical, mathematical and numerical models forming the main structure of the numerical analysis of the thermal, hydral and mechanical behaviour of normal…
Abstract
This paper presents the physical, mathematical and numerical models forming the main structure of the numerical analysis of the thermal, hydral and mechanical behaviour of normal, high‐performance concrete (HPC) and ultra‐high performance concrete (UHPC) structures subjected to heating. A fully coupled non‐linear formulation is designed to predict the behaviour, and potential for spalling, of heated concrete structures for fire and nuclear reactor applications. The physical model is described in more detail, with emphasis being placed upon the real processes occurring in concrete during heating based on tests carried out in several major laboratories around Europe as part of the wider high temperature concrete (HITECO) research programme. A number of experimental and modelling advances are presented in this paper. The stress‐strain behaviour of concrete in direct tension, determined experimentally, is input into the model. The hitherto unknown micro‐structural, hydral and mechanical behaviour of HPC/UHPC were determined experimentally and the information is also built into the model. Two examples of computer simulations concerning experimental validation of the model, i.e. temperature and gas pressure development in a radiatively heated HPC wall and hydro‐thermal and mechanical (damage) performance of a square HPC column during fire, are presented and discussed in the context of full scale fire tests done within the HITECO research programme.
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Introduces papers from this area of expertise from the ISEF 1999 Proceedings. States the goal herein is one of identifying devices or systems able to provide prescribed…
Abstract
Introduces papers from this area of expertise from the ISEF 1999 Proceedings. States the goal herein is one of identifying devices or systems able to provide prescribed performance. Notes that 18 papers from the Symposium are grouped in the area of automated optimal design. Describes the main challenges that condition computational electromagnetism’s future development. Concludes by itemizing the range of applications from small activators to optimization of induction heating systems in this third chapter.
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Qiaosheng Liu, Juntong Xi and Zhuoqi Wu
The purpose of this paper is to propose a universal, robust and efficient method to obtain a reliable initial guess solution for the one‐step finite element simulation.
Abstract
Purpose
The purpose of this paper is to propose a universal, robust and efficient method to obtain a reliable initial guess solution for the one‐step finite element simulation.
Design/methodology/approach
In one‐step simulation, getting initial guess solutions effectively is essential to ensure the success of the non‐linear resolution in the implicit static solver and to speed up the convergence of the Newton‐Raphson iterations. A newly emerging mesh parameterization approach named As‐Rigid‐As‐Possible method, which is widely used in computer graphics, is proposed as an effective initial guess estimation method in this paper. It is almost an isometric parameterization and showing excellent area‐preserving capability than other state‐of‐the‐art approaches. Several numerical examples are provided to verify the validity and efficiency of the presented method.
Findings
Compared with the geometry mapping methods, the presented ARAP method shows its universality in handling types of workpieces whether they have quasi‐vertical walls or they are long and complicated. Complex 3D workpieces with many local convex and concave features can also be well handled without large element shape distortions. In contrast to the energy based mapping algorithm, the method presented in this paper does not need to predefine the boundary nodes which will introduce less distortion to the elements near the boundary.
Originality/value
This paper is the first to utilize the As‐Rigid‐As‐Possible mesh parameterization algorithm to obtain an initial guess for the one‐step simulation. The numerical experiments show that the approach is universal, robust and efficient and can be further utilized in the optimum blank design or blank shape optimization.
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