scholarly journals Experimental Investigations on Electrical Charge of Precracked Rock Specimens under Uniaxial Compression

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Feng He ◽  
Zhenwei Wang ◽  
Yangfeng Zhao ◽  
Gaofeng Song ◽  
Bowen Liu
Keyword(s):  
Uniaxial Compression ◽  
Analytical Model ◽  
Electrical Charge ◽  
Experimental Investigations ◽  
Charge Accumulation ◽  
Engineering Structures ◽  
Rock Samples ◽  
Rock Materials ◽  
Friction Factors ◽  
Secondary Cracks

The electrical charge characteristic of rock materials under compression is an important index for predicting the development of rock fractures and the failure of engineering structures. However, the charge behaviours of a preexisting rock sample have not been studied in depth. In this study, sandstone samples with a single fabricated precrack at different angles of inclination are prepared. The uniaxial compression tests are performed to study the charge behaviours associated with the initiation and propagation of secondary cracks, the mechanical properties, and the progressive failure of stressed rock samples. An improved analytical model based on the maximum tensile stress failure theory for brittle materials is also proposed for determining the crack growth paths of the single precrack rock samples under uniaxial compression. The friction factors of crack surfaces are computed. The results show that the step functions on the curves of charge accumulation over time correspond to the fluctuation of stress, indicating the initiation of microcracks. The sample with a crack inclination angle of π / 4 shows the largest amount of both the first charge and the total accumulation. The analytical model shows a positive relationship between the crack face friction factors and the charge accumulation. The analytical solution of the crack development angles shows good agreement with the experimental results. This work may provide reference for the similar studies regarding the correlation of charging behaviours to the compressed rock materials.

scholarly journals Multi-stable composite twisting structure for morphing applications

2012 ◽  
Vol 468 (2141) ◽  
pp. 1230-1251 ◽  
Author(s):  
X. Lachenal ◽  
P. M. Weaver ◽  
S. Daynes
Keyword(s):  
Analytical Model ◽  
Material Properties ◽  
Degrees Of Freedom ◽  
Design Parameters ◽  
Engineering Structures ◽  
The Past ◽  
Wide Range ◽  
Morphing Structure ◽  
Low Mass ◽  
Unstable States

Conventional shape-changing engineering structures use discrete parts articulated around a number of linkages. Each part carries the loads, and the articulations provide the degrees of freedom of the system, leading to heavy and complex mechanisms. Consequently, there has been increased interest in morphing structures over the past decade owing to their potential to combine the conflicting requirements of strength, flexibility and low mass. This article presents a novel type of morphing structure capable of large deformations, simply consisting of two pre-stressed flanges joined to introduce two stable configurations. The bistability is analysed through a simple analytical model, predicting the positions of the stable and unstable states for different design parameters and material properties. Good correlation is found between experimental results, finite-element modelling and predictions from the analytical model for one particular example. A wide range of design parameters and material properties is also analytically investigated, yielding a remarkable structure with zero stiffness along the twisting axis.

Problems of Cold-Bent Notched C-Shaped Profile Members

2014 ◽  
Vol 941-944 ◽  
pp. 1871-1875 ◽  
Author(s):  
Nikolay I. Vatin ◽  
Tatiana Nazmeeva ◽  
Roman Guslinscky
Keyword(s):  
Bearing Capacity ◽  
Cross Sections ◽  
Experimental Investigations ◽  
Heat Current ◽  
Thermal Profile ◽  
Engineering Structures ◽  
Normative Documents ◽  
Steel Members ◽  
Global Buckling ◽  
Stability Of Structures

Nowadays cold bent steel thermal сold-bent С-profile is widely used in building construction but we still have some little studied questions in the fields of thermal conductivity, air permeability, resistibility and corrosion behavior of the profile. Cold-bent notched С-profile is used for interior exterior panel members. Lengthwise notches made chequerwise in the profile walls increase the distance of heat flow and decrease heat conductivity and eliminate cold bridges that is why the profile is called “thermal profile”. Cold-bent profile made by cold bending requires alternate approach when engineering structures are designed and maintained. The approach means thin walls’ and the profile special form’ impact on the bearing capacity and stability of the structures should be taken into account. In spite of the wide use of cold-bent notched C-profile in building frameworks, we see lack of information on how the notches influence the bearing capacity and stability of structures. There are no official normative documents on calculation and designing of cold-bent notched profile structures. We carry out theoretical and experimental investigations on global buckling and bearing capacity of steel members of C-shaped notched profiles of different cross-sections area. We carry out theoretical and experimental investigations on heat current passing through the thermal profile structure is held with the use of testing bed.

Comparison of Failure Modes of Piping Systems With Wall Thinning Subjected to In-Plane, Out-of-Plane and Mixed Mode Bending Under Seismic Load: Computational Approach

2007 ◽  
Author(s):  
Satoshi Tsunoi ◽  
Akira Mikami ◽  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Analytical Model ◽  
Failure Modes ◽  
Experimental Investigations ◽  
Seismic Load ◽  
Piping System ◽  
Wall Thinning ◽  
Piping Systems ◽  
Out Of Plane ◽  
Seismic Loadings ◽  
Local Wall Thinning

The authors have proposed an analytical model by which they can simulate the dynamic and failure behaviors of piping systems with local wall thinning against seismic loadings. In the previous paper [13], the authors have carried out a series of experimental investigations about dynamic and failure behaviors of the piping system with fully circumferential 50% wall thinning at an elbow or two elbows. In this paper these experiments have been simulated by using the above proposed analytical model and investigated to what extent they can catch the experimental behaviors by simulations.

scholarly journals Method for Analytical Calculation of the Formability from Metallic Bipolar Plates

2019 ◽  
Vol 4 (1) ◽  
pp. 1 ◽  
Author(s):  
Nico Keller ◽  
Alexander Bauer ◽  
Thomas von Unwerth ◽  
Birgit Awiszus
Keyword(s):  
Analytical Model ◽  
Early Development ◽  
Cross Section ◽  
Analytical Calculation ◽  
Good Method ◽  
Channel Cross Section ◽  
Experimental Investigations ◽  
Channel Geometry ◽  
Development State ◽  
Model Approach

The constructive design of a flow field layout and the channel cross section parameters from a metallic half- or bipolar plate can have a significant influence on the performance characteristics of a fuel cell. One important aspect in the dimensioning of the channel geometry of half plates is the technical forming feasibility. In this article, first an equation is presented, which enables an analytical calculation of the channel parameters. Hereby, continuing calculations with parameter variations will be possible. Furthermore, the formability of the channel geometry of metallic half plates is evaluated through numerical and experimental investigations. Based on the results, an analytical model approach will be derived that enables an appraisal of the formability from channel cross section contours in an early development state. As a final step, the results of the numerical investigations and the analytical calculation method are compared and evaluated with the results of experimental investigations and other publications. It will be shown, that the derived analytical model approach has a good approximation compared to the effects and results from the numerical and experimental analysis. In particular, the assessment of whether a channel cross section can be manufactured safely is a result with high probability of the analytical model approach. Imprecisions happen, especially in variants with extreme geometries, for example, with very small radii or a huge channel depth. For this kind of variations, the analytical model behaves too sensitively, which makes it more difficult to estimate the damage effects. However, at an early development state, the analytical model offers a good method to get a pre-evaluation of the formability of channel cross sections with a simultaneous parameter variation possibility.

scholarly journals Failures of the Cast-Iron Columns of Historic Buildings—Case Studies

2020 ◽  
Vol 5 (9) ◽  
pp. 71
Author(s):  
Michał Gołdyn ◽  
Tadeusz Urban
Keyword(s):  
Cast Iron ◽  
20Th Century ◽  
Design Principles ◽  
Experimental Investigations ◽  
Engineering Structures ◽  
Technical Problems ◽  
Industrial Buildings ◽  
Material Uncertainties ◽  
19Th And 20Th Century ◽  
Post Industrial

Selected technical problems related to the rehabilitation of cast-iron columns in structures from the turn of the 19th and 20th century are discussed in the paper. Lack of contemporary standard regulations related to the design of cast-iron structures is a significant problem in the design works and experimental investigations on cast-iron columns are frequently required. The paper presents results of the tests concerning principal properties of cast-iron—strength and deformability. The historical design principles are discussed in the light of the results of experimental investigations. As it was demonstrated, the actual load-carrying capacities of cast-iron columns may exceed by several times the values resulting from the 20th century design rules. The conservatism of the design principles resulted, however, from the material uncertainties—lack of homogeneity and hidden defects of the cast-iron. Selected examples of failures of cast-iron columns from 19th-century structures such as post-industrial buildings and engineering structures are discussed. They resulted from errors made during adaptation works. The reasons for these failures and considered methods of repairing the structures are presented.

A New Bump-Type Foil Bearing Structure Analytical Model

2007 ◽  
Vol 129 (4) ◽  
pp. 1047-1057 ◽  
Author(s):  
Sébastien Le Lez ◽  
Mihaï Arghir ◽  
Jean Frene
Keyword(s):  
Analytical Model ◽  
Degrees Of Freedom ◽  
Load Capacity ◽  
Reaction Force ◽  
Analytical Models ◽  
Experimental Investigations ◽  
Underlying Structure ◽  
Static System ◽  
Theoretical Approaches ◽  
Foil Bearing

A gas bearing of bump foil type comprises an underlying structure made of one or several strips of corrugated sheet metal covered by a top foil surface. The fluid film pressure needs to be coupled with the behavior of the structure for obtaining the whole bearing characteristics. Unlike in classical elasto-aerodynamic models, a foil bearing (FB) structure has a very particular behavior due to friction interfaces, bump interactions, and nonisotropic stiffness. Some authors have studied this complex behavior with the help of three-dimensional finite element simulations. These simulations evidenced a lack of reliable analytical models that can be easily implemented in a FB prediction code. The models found in the literature tend to overestimate the foil flexibility because most of them do not consider the interactions between bumps that are highly important. The present work then develops a model that describes the FB structure as a multidegree of freedom system of interacting bumps. Each bump includes three degrees of freedom linked with elementary springs. The stiffnesses of these springs are analytically expressed so that the model can be adjusted for any dimensions and material properties. Once the stiffness matrix of the whole FB structure is obtained, the entire static system is solved taking friction into account. Despite its relative simplicity, comparisons with finite elements simulations for various static load distributions and friction coefficients show a good correlation. This analytical model has been integrated into a foil bearing prediction code. The load capacity of a first generation foil bearing was then calculated using this structure model as well as other simplified theoretical approaches. Significant differences were observed, revealing the paramount influence of the structure on the static and dynamic characteristics of the foil bearing. Some experimental investigations of the static stiffness of the structure were also realized for complete foil bearings. The structure reaction force was calculated for a shaft displacement with zero rotation speed, using either the multidegree of freedom model or the usual stiffness formulas. The comparisons between theoretical and experimental results also tend to confirm the importance of taking into account the bump interactions in determining the response of the structure.

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