Plate Section Research Articles

Machine learning RBF-based surrogate models for uncertainty quantification of age and time-dependent fracture mechanics

This paper proposes a machine learning strategy using radial basis function (RBF) as surrogate models for uncertainty quantification of age and time-dependent fracture mechanics problems. The RBF surrogate models are trained to replace the time-consuming evaluations of the mapping integral of the time-dependent energy release rate. The probabilistic problem considers input random variables of geometry, loading, and material parameters for a concrete plate section with the presence of an initial surface crack. The performance of the RBF surrogates was evaluated through cross-validation and Monte Carlo reference solutions that expensively evaluated the integrals. The results of mean square errors and the Kolmogorov-Smirnov goodness-of-fit tests on the predicted probability and cumulative density functions show that, the RBF surrogates reached good accuracy even for a small training set size, rather than second-order polynomial models which could reasonably perform only for bigger training set sizes. The RBF surrogates accurately predict even long-tail distributions for farther prediction times with relatively small training sets. The proposed RBF surrogate models presented the generalization capabilities to predict thousands of unseen data points from Monte Carlo simulations and successfully assess the uncertainty quantification of the time-dependent energy release rate.

Repairing of one-way reinforced concrete slab using externally CNC perforated steel plate. Theoretical study.

This research includes the design steps for using solid and perforated steel plate to repair an under reinforcement one-way concrete slab in flexure. All slabs were assumed to be subjected to 85 percent of ultimate load in flexure, therefore the section of the slab to be repairing assumed to be cracked, and the additional external reinforcement represented by the steel plate will be designed according to this assumption and according to the limitations of ACI 318 code specifications. Results of the theoretical calculation indicated that increasing the thickness of the solid plate causes increasing the interface stresses by (72.6%) when replacing the dimensions (width x thickness) of the plate section from (300mm×1mm) to (200mm×1.5mm), while increasing the width of the plate reduces the interface stresses by (48%) when changing dimensions of the plate section to (400mm×0.75mm). Using perforated plate will increase the ductility and reduce the interface shear stresses. Using the plate width to thickness ratio { (bP/dP)=300} will reduce these stresses by (14.8%) when using perforated plate instead of solid one. Increasing the ratio of (bP/dP) lead to reduce the interface shear stresses, as well as reduce the difference between the effect of using solid or perforated steel plates on interface stresses, also when reducing ratio of (bP/dP) the interface shear stress will be increase. Changing the number and diameters of the holes from (10 # 10 mm) to (2 # 50 mm) with keeping the cross-section area of the steel plate constant for both cases increased the resistance of the epoxy nails to the shear stresses that transmitted to them from the axial stresses in the plate by (400%). A new expression is presented in study to calculation the interface shear stress.

Experimental evaluation and numerical simulation of low-yield-point steel shear panel dampers

Shear panel dampers are considered as a type of reliable passive energy dissipation device for seismic resistant structures with a damage-controlling concept. It has been revealed that the shear bulking of core plates and the premature failure of boundary plates are the main concerns for a shear panel damper that result in insufficient energy dissipation and undesirable ultra-low cycle fatigue performance. This study utilizes square steel tubes serving as out-of-plane stiffeners for the core plates made of a low-yield-point steel with a nominal yield stress of 225 MPa (named LYP225 steel). Meanwhile, a reduced flange plate section is adopted to mitigate the end fracture. An experimental study is carried out on three full-scale damper specimens with different flange plates and loading protocols. The test results show that the square tubes well prevent the bulking of the core plates and all the specimens exhibit plump hysteretic response and satisfactory energy dissipation capacity. The reduced plate sections reduce the likelihood of crack propagation occurring at the flange end, and thereby improve the ultra-low cycle fatigue performance. In order to develop the numerical model of shear panel dampers, a combined-hardening constitutive model with a memory surface is applied to represent the plasticity of LYP225 steel. Based on a plasticity analysis, a simplified calibration procedure is proposed associated with the three-dimensional constitutive model, where the plasticity parameters of LYP225 steel are determined using only the monotonic tensile test data. Eventually, the numerical results of uniaxial specimens and damper specimens are in good agreement with the test results, which validates the effectiveness of the constitutive model and the proposed calibration method.

Paleozoic sequence stratigraphy, depositional systems, and hydrocarbon habitats across the Arabian plate

The Paleozoic sedimentary section of the Arabian plate recorded the effects of numerous fluctuations in sea level and gentle epeirogenic movements. Eustatic changes in sea level over the Arabian plate resulted in transgressions and regressions and created many local and regional unconformity surfaces, identified by missing section and nondeposition. The distant deformation of the Caledonian tectonic orogeny and mountain building of the North Atlantic region, and the later Hercynian tectonic event, are partially responsible for eustatic sea-level changes. Additionally, detailed evidence of Paleozoic glacial erosion and glacial eustasy in the regressive sedimentary section over uplifted paleohighs comes from deep wells penetrating local exotic tectonic blocks. The resulting surfaces mark the sea-level falls associated with the glacial events in the Ordovician, Late Devonian, and Carboniferous–early Permian sediments. The depositional settings of the Cambrian–upper Permian rocks include deltaic and glacial settings and are expressed as alluvial–fluvial fans that grade into braided plains and shallow-marine carbonates flanked by distal shales. Late Permian sediment fill accompanied the development of widespread accommodation, resulting from a major sea-level rise, coinciding with a major period of carbonate–evaporite deposition, in which clastic sediments were only a minor factor. The regional sedimentary facies have good reservoir quality and are juxtaposed to regional source rocks and seals associated with both structural and minor stratigraphic traps. Production occurs in Precambrian through Permian strata in which mature clastic and shallow-water carbonate reservoirs occur, commonly sealed by shales, and sourced by Silurian hot shales or older source rocks in the section.

Analysis of flexural capacity of a novel straight-side U-shaped steel-encased concrete composite beam

This paper proposes a novel straight-side U-shaped steel-encased concrete composite beam (SUSCCB). The SUSCCB is constituted by encasing the top sections of the U-shaped steel plates directly into the concrete flange, with the composite action generated through perfobond connections consisting of reinforcement bars transversely passing through perforations in the encased top sections of the steel plates. It is engineered to overcome the shortcomings of the existing varus or valgus U-shaped steel-encased concrete composite beams (USCCB), for which the installation of shear connectors can be complex and costly to achieve because of the numerous required welds. The main objective of this paper is to study the flexural behavior of the proposed SUSCCB and develop a method for calculating its flexural capacity. A finite element model (FEM) is developed and validated against available USCCB experimental results. After, the validated FEM is used to conduct a parametric study of the SUSCCB. The flexural behavior is assessed from the strain distribution, stress analysis, and load–deflection curves. Results show that the flexural performance of the SUSCCB is superior to that of a traditional USCCB, and that its flexural capacity can be calculated through the simplified plastic theory. Lastly, the analytical flexural capacity of the SUSCCB is derived. The analytical values show close agreement with results from the numerical simulations.

АНАЛИЗ ПРОЦЕССА ИЗМЕНЕНИЯ СВОЙСТВ И СТРУКТУРЫ МАТЕРИАЛА ОБРАЗЦОВ ПОД ВОЗДЕЙСТВИЕМ УЛЬТРАЗВУКОВОЙ СТАБИЛИЗАЦИИ

The most important task of precision engineering on the modern stage is the development of effective technological processes of manufacturing, providing not only achieving high precision at low costs, but also retaining the original in terms of accuracy throughout the life of the product. (Research purpose) The research purpose is in studying the possible negative effect of ultrasonic mechanical vibration in the process of stabilizing the deformation of circular plates on the subject of appearing of various kinds of micro-cracks, which result will be a sharp decrease in resource products in general, and to make a comparative analysis of changes in the properties and structure of the material. (Materials and methods) Half of the prepared samples were processed using a thermomechanical technology based on the cyclic action of a liquid or gas in different temperature conditions, the other part of the samples was processed using the proposed technology based on the method of ultrasonic mechanical action. The end section of the round plate for both processing options was prepared. (Results and discussion) In the structure of the material of both the samples treated by different methods, there are certain bundles of the micro-cracks type caused by plastic impact. The structure of sample material processed by standard method is more rough, the concentration of microcracks in the material of the sample treated by ultrasonic impact does not exceed the concentration of microcracks of the sample material processed in a standard way. (Conclusions) Changing the structure of the material of the round plate after ultrasonic treatment may not have a negative impact and does not affect the durability of the product during operation. With the correct choice of the ultrasonic treatment mode, a more uniform stress reduction can be achieved during the processing, and the quality and efficiency of the process can be improved. Ultrasonic processing increases the mechanical characteristics of the material, such as tensile strength and proportionality.

Tensile behavior and load transfer mechanism of concrete-filled square steel tube exterior-diaphragm connections stiffened with PBL

An innovative concrete-filled square steel tube (CFSST) exterior-diaphragm connection stiffened with perfobond ribs (PBL) is proposed to overcome the limits of CFSST exterior-diaphragm connections. Different CFSST connections, including one ordinary CFSST connection, one CFSST exterior-diaphragm connection, two CFSST exterior-diaphragm connections stiffened with PBL, and two CFSST connections stiffened with PBL, were tested under tensile loads. The tensile behavior, including failure modes, initial stiffness, yield load, peak load, and deformation of different connections, was analyzed and compared based on the test results. By analyzing the stress distribution in critical sections of branch plates or exterior diaphragms and the contribution of different parts to the total tensile load in critical sections of joint regions at different loading stages using the finite element method, the load transfer mechanism of different connections was analyzed and compared quantitatively. The results showed that the PBL transferred a considerable percentage of the tensile load from the branch plates or exterior diaphragms to the core concrete, which resulted in a more uniform stress distribution in the branch plates and exterior diaphragms and caused the core concrete to have a direct function in the load transfer in joint regions; thus, the load transfer and deformation condition of connections were improved. The innovative CFSST exterior-diaphragm connections stiffened with PBL had excellent tensile behavior with the largest initial stiffness, yield load, and peak load, the smallest joint region deformation, and the most uniform stress distribution, thus failed due to the yielding of branch plates.

АНАЛИЗ ПРОЦЕССА ИЗМЕНЕНИЯ СВОЙСТВ И СТРУКТУРЫ МАТЕРИАЛА ОБРАЗЦОВ ПОД ВОЗДЕЙСТВИЕМ УЛЬТРАЗВУКОВОЙ СТАБИЛИЗАЦИИ

The most important task of precision engineering on the modern stage is the development of effective technological processes of manufacturing, providing not only achieving high precision at low costs, but also retaining the original in terms of accuracy throughout the life of the product. (Research purpose) The research purpose is in studying the possible negative effect of ultrasonic mechanical vibration in the process of stabilizing the deformation of circular plates on the subject of appearing of various kinds of micro-cracks, which result will be a sharp decrease in resource products in general, and to make a comparative analysis of changes in the properties and structure of the material. (Materials and methods) Half of the prepared samples were processed using a thermomechanical technology based on the cyclic action of a liquid or gas in different temperature conditions, the other part of the samples was processed using the proposed technology based on the method of ultrasonic mechanical action. The end section of the round plate for both processing options was prepared. (Results and discussion) In the structure of the material of both the samples treated by different methods, there are certain bundles of the micro-cracks type caused by plastic impact. The structure of sample material processed by standard method is more rough, the concentration of microcracks in the material of the sample treated by ultrasonic impact does not exceed the concentration of microcracks of the sample material processed in a standard way. (Conclusions) Changing the structure of the material of the round plate after ultrasonic treatment may not have a negative impact and does not affect the durability of the product during operation. With the correct choice of the ultrasonic treatment mode, a more uniform stress reduction can be achieved during the processing, and the quality and efficiency of the process can be improved. Ultrasonic processing increases the mechanical characteristics of the material, such as tensile strength and proportionality.

Study on Vibration and Stability Analysis of Thick Rectangular Plates Section

This paper is the second part of free vibration and stability analysis of thick isotropic and orthotropic plates. The support condition CCCC and CCFC support was considered by applying the alternative II theory based on polynomial shape function. The work was based on the application of the formulation earlier derived using Ritz method. The frequency values of the first mode and critical loads obtained were compared with those obtained using first order shear deformation theory. For span to depth ratio of 10, the fundamental linear frequency for orthotropic CCFC plate corresponding to modulus of elasticity ratios (E1/E2) of 10, 25 and 40 were 0.00312Hz, 0.00373 Hz and 0.00398Hz.

Features for calculating beams with a thin transverse corrugated web plate considering bending-twisting forces

The article describes the features of the work of beams with a thin transverse corrugated web plate. Exponential fractional regression is presented, which allows one to estimate the relative height of web plate sections working together with flanges, obtained by the authors based on an analysis of numerical experiments. Based on the features of the work, a method is proposed for describing the stress state of an arbitrary cross-section of an I-beam with a thin transverse corrugated web plate (the profile of the corrugations is triangular, trapezoidal, sinusoidal) bent in the plane of the web plate and compressed in the longitudinal direction, using the theory of thin-web platted elastic rods by Professor V.Z. Vlasov. The calculations are given for determining the bending-twisting forces (local bending moments and bimoments arising from the action of the main forces) in an arbitrary cross section.

Study of Effects of Stress Concentration and Variation of Mechanical Properties

In this paper, we compare two approaches to the determination of stress-strain states (SSS) and the strength analysis of a thin plate with a circular hole concentrator under static and cyclic loading by solving the elastic problem (Kirsch problem) and applying the deformation criteria developed at the Mechanical Engineering Research Institute for deformation and fracture. In the new approach, the characteristics of the main mechanical properties, the values ​​of the nominal stresses, and the strain field in the zones of stress concentration (a total of four calculated cases) were varied for the first time. Studies showed that elastoplastic stresses and strains, which differ significantly from those obtained as a result of solving the elastic problem, arise even under the initial loading at the points of the cross section near the concentrator. Determined by deformation criteria, the results of the SSS analysis and strength analysis of a thin plate with a circular hole significantly differed from those obtained by the traditional elastic solution. This applies to the initial loading both in the maximum concentration zone (on the hole contour) and at other points of the dangerous cross section under cyclic loading. Using the above method, the cyclic kinetics of stresses and strains in the concentration zones (for a specified plate section) for any loading cycle can be calculated, while cyclic durability can be more accurately calculated taking into account the dispersion of the basic mechanical properties of the structural material.

Effective heat transfer surfaces of tubes and plates with spiral vortex generators – inclined oval-trench dimples

Numerical simulation of laminar heat transfer enhancement at the hydrodynamic stabilization length of the tube with 8 inclined longitudinal oval-trench dimples (OTDs) in the transformer oil flow has revealed an optimal inclination angle of dimples, at which a value of thermal and hydraulic performance (THP) is achieved. Heat transfer of a dimpled tube increases by a factor of 28 in comparison with a smooth tube at practically invariable hydraulic losses. Heat transfer enhancement is calculated in turbulent air flow around a flat plate with a package of 16 one-row dimples inclined at an angle of 60° on the longitudinal section of 40 in length and 4 in width under the symmetry conditions at the side boundaries of the plate section and at a dimple step of 2.4. The dimple is 1 in width, 4.5 in length, and 0.2 in depth. Its rounding radius is 0.3. The boundary layer thickness at the section inlet is 0.175. The effect of abnormal separated flow intensification and heat transfer enhancement in dimples has been confirmed. (f/f pl )min=-3, (Nu/Nu pl )max = 4. Relative heat transfer grows by a factor of 1.43 in comparison with the smooth plate and the drag coefficient increases by a factor of 2.08. However the thermal and hydraulic performance defined in terms of heat load growth is 1.12.

Design and Calculation of PC Composite Rigid Frame Bridge with Variable Section Steel Truss Webs

Steel truss web prestressed concrete composite bridge has many advantages, such as light weight, clear stress, beautiful structure, convenient construction, etc., but it is still in its infancy in China. Taking Shuinianbao bridge of Yanchong high speed as an example, this paper introduces the design method of PC composite rigid frame bridge with variable cross-section continuous steel truss web, and analyzes the static calculation of the whole bridge in combination with the code, so as to provide design reference for the construction and development of PC composite bridge with variable cross-section steel truss web. The analysis results show that: the calculation results obtained after modeling according to the design size meet the design requirements. Under the condition of ultimate bearing capacity, the top plate obtains a more uniform maximum resistance, and the arch curve makes the internal force of the bottom plate relatively small. Under the combination of short-term load effect, the main tensile stress of the inclined section appears at the position close to the support and the middle span section of the top plate. The main tensile stress of the steel truss web member is the most different under the unfavorable load combination, the maximum tensile stress is greater than the compressive stress, and the maximum tensile stress occurs at 1/4 of the mid-span.

An Experimental Study of the Influence of Eccentricity on Shear Lag Effects in Welded Connections

In the 2010 AISC Specification, the shear lag factor for longitudinally welded tension members was applicable only to plate-type members having equal length welds on each side with a minimum length equal to the distance between the welds (AISC, 2010). Fortney and Thornton (2012) used experimental data from three previous research programs consisting of 175 various tension members to develop a generalized shear lag model that addresses the aforementioned limitations. The members comprising this dataset consisted of 158 flat plates with equal weld lengths, 4 single angles with unequal but balanced weld lengths, and 13 other members having equal weld lengths. The shear lag factor presented in the 2016 AISC Specification Table D3.1, Case 4 (AISC, 2016b) is a product of Fortney and Thornton’s work and applies to longitudinally welded plates, angles, channels, tees, and W-shapes having equal or unequal lengths and no length-to-width limitation. This paper presents an experimental study on the shear lag effects in longitudinally welded tension members under both in-plane and out-of-plane eccentricity through the testing of eight 3×1/2 plate sections and twelve 3×3×1/2 single-angle sections having both equal and unequal longitudinal weld lengths. Experimental shear lag factors were determined for each of the 20 tested specimens and compared to three theoretical values: (1) the shear lag factor in the 2010 AISC Specification (AISC, 2010), (2) the shear lag factor based on a bi-planar model (Fortney and Thornton, 2012), and (3) the shear lag factor from Case 4 in the 2016 AISC Specification. The findings of this experimental study confirm that shear lag factor given by Case 4 in the 2016 AISC Specification provides the best prediction of shear lag factors in welded connections subject to both in-plane and out-of-plane eccentricity.

Specific features of structure formation during the development of the lithosphere of the Gulf of Aden (physical modeling)

The study was focused on the tectonic structure features of the Gulf of Aden, which includes three provinces. The western, central and eastern provinces differ in morphostructural segmentation of the spreading ridge of the Gulf of Aden, which took place in different geodynamic regimes of their formation and development. In our study, physical modeling was performed to investigate the segmentation mechanisms of the three parts and the formation of the marginal plateau and the island of Socotral. In experiments, an elastic-plastic plate lying on a liquid base (simulating melt) was subjected to normal or oblique stretchig. Plate sections imitating the continental or oceanic lithosphere in the model had different thicknesses. Various heterogeneities, such as cuts, linear weakened zones (rift heating zones) etc., were set in the plate sections in accordance with natural analogues. The modeling results show that morphostructural segmentation of the spreading axis in the Gulf of Aden depends on the degree of heating and the thickness of the lithosphere, associated with different distances from the Afar plume and local thermal anomalies, spreading obliquity and the existence of structural inhomogeneities with increased lithosphere strength, which are associated in this case with the presence of Mesozoic grabens on the pre-breakup basement. The smaller is the lithosphere thickness, the smaller is the size of the segments. The sharper is the angle, the more pronounced is segmentation. The study of the connection of the Gulf of Aden continental rift with the rift zone of the Carlsberg ridge suggests that during their development, these rift fractures propagated towards each other. The experiment results show that in case of a «sharp» boundary between blocks that differ in thickness, a shear zone is likely to occur. Such a case is applicable, for example, to the Alula-Fartak fracture zone, or to Owen’s fracture zone. With a less ‘sharp’ boundary, overlapping structures are often formed, such as microplates or microblocks enclosed between two rift fissures. In such case, one microblock then dies, while the other develops into a spreading ridge. Apparently, such a microblock is represented by the marginal plateau and the island of Sokotra. As shown by the modeling, propagation of the two rifts towards each other was important for the formation of the plateau and the island of Socotra. Moreover, a significant role was played by the initial geometry of the rift zones and their initial positioning separate from each other.

Determination of stress concentration factor in the section of the composite plate weakened by the hole, upon contact of the hole with the cylinder

Problematic. When designing bolted joints (BJ), it is necessary, to carry out verification strength calculations. In this case, it is advisable to use express analysis: calculations using simple formulas of sufficient accuracy. One of the main strength calculations of BJ is the calculation of the gap section weakened by the hole. For BJ plates made of layered fibre-reinforced polymers (FRP), the problem has not yet been solved.Research objective. To verify the accuracy of two well-known express analysis formulas for stress concentration factors (SCF) at the contact of the hole with the bolt, using contrasting examples of materials and schemes for reinforcing FRP plates.Realization technique. Numerical calculations were carried out using the finite element method (contact problem) for a BJ plate made of layered FRP. A 3D orthotropy of each monolayer was assumed. Two simple express analysis formulas were tested. The results are tabulated. The illustrations are provided.The results of research. Numerical estimates are obtained that characterize the degree of influence of material characteristics and reinforcement patterns in a layered FRP plate and the accuracy of the formulas considered.Conclusions. A change in the material and the reinforcement scheme of the layered FRP leads to a significant change in the SCF values of the bolt-loaded hole in the section of the plate weakened by the hole, and the considered express analysis formulas have insufficient accuracy for contrast cases of materials and plate reinforcement schemes. More research is needed.

Hydroelasticity effects on water-structure impacts

Local and global loadings, which may cause the local damage and/or global failure and collapse of offshore structures and ships, are experimentally investigated in this study. The research question is how the elasticity of the structural section affects loading during severe environmental conditions. Two different experiments were undertaken in this study to try to answer this question: (i) vertical slamming impacts of a square flat plate, which represents a plate section of the bottom or bow of a ship structure, onto water surface with zero degree deadrise angle; (ii) wave impacts on a truncated vertical wall in water, where the wall represents a plate section of a hull. The plate and wall are constructed such that they can be either rigid or elastic by virtue of a specially designed spring system. The experiments were carried out in the University of Plymouth’s COAST Laboratory. For the cases considered here, elasticity of the impact plate and/or wall has an effect on the slamming and wave impact loads. Here the slamming impact loads (both pressure and force) were considerably reduced for the elastic plate compared to the rigid one, though only at high impact velocities. The total impact force on the elastic wall was found to reduce for the high aeration, flip-through and slightly breaking wave impacts. However, the impact pressure decreased on the elastic wall only under flip-through wave impact. Due to the elasticity of the plates, the impulse of the first positive phase of pressure and force decreases significantly for the vertical slamming impact tests. This significant effect of hydroelasticity is also found for the total force impulse on the vertical wall under wave impacts.Graphic abstractHydroelasticity effects on water-structure impacts: a impact pressures on dropped plates; b impact forces on dropped plates; c, d, e, f wave impact pressures on the vertical walls; g wave impact forces on the vertical walls; h wave force impulses on the vertical walls: elastic wall 1 vs. rigid wall (filled markers); elastic wall 2 vs. rigid wall (empty markers)

Effect of cold rolling process on microstructure and properties of T1 Copper sheet

The 8mm thick T1 state copper plate was cold rolled into 3mm, 2mm and 1mm thin plate sections, and its microstructure and texture were analyzed by optical metallographic microscope and X-ray diffraction (XRD). The mechanical properties were tested by cupping machine and micro-hardness tester. The results show that with the increase of cold rolling deformation, the grain size decreases and a strong (220) diffraction surface texture appears. The highest tensile strength is 421.76MPa, and the microhardness is 129.9HV, all of which are greatly improved, but the elongation decreases from 40% to 5%, and the fracture morphology changes from ductile fracture to quasi cleavage fracture.

Investigation of the generalized solution behavior for the transverse deflection of a rigid-plastic clamped plate: Eccentric and multiple punches loading

For most of the studies concerning about the transverse deflection of plates subjected to the loading of a rigid punch, the sections of the punch and the plate are usually circular and concentric. However, eccentric loading conditions in which the punch and the plate may not be circular and concentric have seldom been discussed. This paper firstly studied the solution behavior for a rigid-plastic clamped plate under quasi-static eccentric loading conditions based on the theory of rotation-rate continuity and the method of fundamental solutions (MFS). For eccentric loading, four types of loading conditions have been applied: circular punch vs circular plate (CC), circular punch vs elliptical plate (C-E), elliptical punch vs circular plate (E-C) and elliptical punch vs elliptical plate (E-E). The load position of the punch is also arbitrary with respect to the plate. Contour lines of transverse deflection, principal stress and strain and punching force-punch displacement curves have been obtained for different loading conditions. It has been proved that the circuit integral of the product of transverse deflection gradient and contour line's outer normal is constant for any contour line, leading to a linear relationship between the punching force and deflection of the punch. It turns out that the ratio of punch section area to plate section area and the deviation distance of the punch center from the plate center will both influence the value of the circuit integral term, which is correlated with the punching force, as they increase the punching force will also increase if the punch displacement is fixed, and vice versa. Finally, accounting for the merits of MFS in solving the Laplace equation, the solution procedure can be extended to multiple punches loading conditions. Results have revealed that rotation-rate continuity still prevails in rigid-plastic solids in this case. Finite element analysis has been conducted to show that its results agree with the analytical results at a satisfactory level.

Finite amplitude torsional oscillations of shape-morphing plates immersed in viscous fluids

In this paper, we study torsional oscillations of a cross section of a thin plate submerged in a quiescent, Newtonian, incompressible, and viscous fluid. The plate is subjected to a prescribed shape-morphing deformation in phase with the rigid oscillation. The problem is completely described by three nondimensional parameters indicating oscillation frequency and amplitude and intensity of the shape-morphing deformation. We conduct a parametric study to investigate the possibility of controlling hydrodynamic moments and power dissipation through an active time-varying shape-morphing strategy. The problem is studied in both the linear and nonlinear flow regimes, by employing the boundary element method and direct numerical simulations via computational fluid dynamics methods, respectively. Investigation of flow physics demonstrates that, similarly to what is observed for the case of flexural oscillations, the shape-morphing strategy is effective in modulating vortex shedding in torsional oscillations. The results show that hydrodynamic power dissipation can be minimized and hydrodynamic moments can be controlled through an optimal imposed shape-morphing deformation. Findings from this study are directly applicable to torsional oscillation-based underwater energy harvesting or sensing and actuation systems, where control of hydrodynamic moments and reduction of hydrodynamic power losses are necessary for optimal device operation.