Central Deflection Research Articles

Low-velocity impact behaviours of AFP manufactured fibre metal laminate structures

This study reports the findings on the impact behaviour of metal-composite structures. Carbon fibre/Epoxy composite laminates were manufactured by using the Automated Fibre Placement (AFP) technique. Subsequently, hybrid structures were fabricated by bonding fibre laminate and aluminium plate together. The hybrids were tested at low velocity impact energies to probe the role of AFP composite laminates on the performance of the hybrid system. Our findings show that the bonding of the composite onto aluminium plate increased the natural frequency (stiffness) of the system and its energy absorption capability by almost 40 %. It was also found that the fibre layout of AFP composite significantly improved the central deflection of the hybrid. For instance, the deflection of cross-ply hybrids was 15% less in comparison to their counterparts with unidirectional fibrous composites. Nevertheless, under the investigated energies, the fibre layout appeared to have a marginal influence on the peak contact force. Post-mortem examination showed that at an impact energy of 150 J there was no fibre failure observed in asymmetric FMLs with unidirectional composite laminates. Conversely, the fibre failure in cross-ply hybrids occurred at 150 J. This suggests that less energy is required to induce fibre failure energy in cross-ply hybrids when compared to their unidirectional hybrid counterparts. Furthermore, it was also found that substrate treatment was successful in preventing excessive delamination, even though its influence on the peak contact force was not significant.

Bending and flexural-buckling strength of steel members considering strain-rate-effects at elevated temperatures

PurposeIn this study, the bending strength, flexural buckling strength and collapse temperature of small steel specimens with rectangular cross-sections were examined by steady and transient state tests with various heating and deformation rates.Design/methodology/approachThe engineering stress and strain relationships for Japan industrial standard (JIS) SN400 B mild steels at elevated temperatures were obtained by coupon tests under three strain rates. A bending test using a simple supported small beam specimen was conducted to examine the effects of the deformation rates on the centre deflection under steady-state conditions and the heating rates under transient state conditions. Flexural buckling tests using the same cross-section specimen as that used in the bending test were conducted under steady-state and transient-state conditions.FindingsIt was clarified that the bending strength and collapse temperature are evaluated by the full plastic moment using the effective strength when the strain is equal to 0.01 or 0.02 under fast strain rates (0.03 and 0.07 min–1). In contrast, the flexural buckling strength and collapse temperature are approximately evaluated by the buckling strength using the 0.002 offset yield strength under a slow strain rate (0.003 min–1).Originality/valueRegarding both bending and flexural buckling strengths and collapse temperatures of steel members subjected to fire, the relationships among effects of steel strain rate for coupon test results, heating and deformation rates for the heated steel members were minutely investigated by the steady and transient-state tests at elevated temperatures.

Assessment of Creep Properties Using Small Punch Test for a 9%Cr-Mo-Co-B Power Plant Steel

The present study provides a feasible method to evaluate creep properties for a 9%Cr-Mo-Co-B power plant steel by comparing two sets of data obtained from small punch tests and conventional uniaxial creep tests. The method includes three steps: firstly, conduct a series of small punch tests and conventional creep tests in different load and temperature conditions; secondly, convert the load and central deflection data obtained from the small punch test to stress and strain data; thirdly, determinate the best fit correlation factor by comparing the two sets of data in selected creep models. It is found that two sets of data show a similar trend in stress–rupture time relation, stress–minimum strain rate relation and LMP–stress relation. The correlation factor, ksp, can effectively bridge the gap between the load in small punch test and the stress in conventional creep test. For a high-Cr martensitic heat-resistant steel named as CB2, the ksp value 1.4 can make a good prediction for rupture time, while for minimum creep rate and the Larson–Miller parameter, the ksp value 1.4 will lead a conservative prediction in the low-stress range.

Strengthening of Un-Reinforced Brick Masonry Walls Using Epoxy Mortar

Abstract This study is carried out to investigate the effectiveness of using externally applied epoxy mortar on joints of masonry wall panels to enhance their load carrying capacity under axial compressive and lateral loads. A total of six 113 mm thick masonry wall panels of size 1200 x 1200 mm were constructed for this study. Four out of six walls were strengthened using locally available CHEMDUR-31 epoxy mortar on joints. The remaining two walls were tested as control specimens. The control and strengthened wall panels were tested under axial compression and lateral loads. In axial compression test, out of plane central deflection and vertical strain at the center of wall panel were recorded while in lateral load test, in-plane lateral displacement of wall and horizontal strain at the center were recorded at each load increment. Failure pattern of each wall panel is also studied to notice its structural behavior. The results of this experimental study showed an increase of 45% and 60% in load carrying capacity under axial compression and lateral bending, respectively by the use of strengthening technique employed in this study.

Effectiveness of line type and cross type piezoelectric patches on active vibration control of a flexible rectangular plate

Abstract In the present work, vibration control of a simply supported plate with line type and cross type piezoelectric (PZT) patches are investigated with and without actuation voltage. The plate is modeled under the assumption of Kirchhoff’s Plate theory. The mass of PZT patches remain constant in all cases. In case of actuation, applied voltage considered are 1, 2 and 3 mV. The external excitation to the plate is in the form of harmonically varying point load of 1 mN. It is noticed that cross type PZT patch is more effective in deflection suppression of plate than that of line type PZT patch at 3 mV of actuation at patch thickness of 0.75 μm. Suppression of central deflection of plate for line type and cross type PZT patches are obtained in different frequency bands of (175–185 Hz) and (870–880 Hz) respectively.

Effect of hygrothermal load on amplitude frequency response for CFRP spherical shell panel

During the service life of polymer matrix composites, various loading conditions often occur. To use such materials effectively in high-performance applications, their behaviors under hygrothermal effects should be clearly understood. Firstly, a laminated spherical shell panel is established under hygrothermal effects, followed by geometric properties’ analysis and internal forces analysis of the shell. Then, the constitutive relations related to the hygrothermal effects are considered in the laminated spherical shell panel, and equations of motion with geometric nonlinearity are derived by employing Hamilton’s principle; thereafter, solution of equations of motion is obtained using the Navier solution technique. Finally, influences of the hygrothermal effects on nondimensionalized center deflections, nondimensionalized fundamental natural frequency, and vibration-deflection amplitude for the shell are discussed.

Structural behaviour of isolated composite beam-slab system subject to elevated temperature

Composite beam-slab systems are frequently used in buildings because they can reduce construction cost and time effectively, but the supporting steel beams are vulnerable under fire condition, weakening the structural performance. Therefore, fire safety should be carefully considered in the design of composite slab-beam system. In this study, the structural behaviour of isolated composite beam-slab system under fire condition has been experimentally and numerically investigated. Three specimens, viz. an isolated composite square slab without interior beam, and two isolated composite slab panels with an unprotected interior beam with aspect ratios of 1 and 1.5, respectively, were heated during which uniformly distributed load was applied. Temperature, centre deflection, crack patterns, failure time, and lateral movements and strains of supporting columns were recorded by conventional techniques. A novel non-contact approach based on photogrammetry was adopted to measure three-dimensional displacements of the specimens in fire testing for the first time, which could avoid direct contact between instrumentation and the heated specimen. However, some points may be obscured in the image view by either rising water vapour or load cell. Each specimen kept its integrity due to tensile membrane action (TMA) although large deformations occurred. Finite element (FE) models using concrete damage plasticity (CDP) model were also built up and verified by the experiments. The results of this study showed that the slab with larger aspect ratio had TMA in earlier stage, greater the cross-sectional tensile forces and lower fire resistance because the failure mechanism changed from two-directional TMA to one-way catenary action.

Large Deformation Problem of Bimodular Functionally-Graded Thin Circular Plates Subjected to Transversely Uniformly-Distributed Load: Perturbation Solution without Small-Rotation-Angle Assumption

In this study, the large deformation problem of a functionally-graded thin circular plate subjected to transversely uniformly-distributed load and with different moduli in tension and compression (bimodular property) is theoretically analyzed, in which the small-rotation-angle assumption, commonly used in the classical Föppl–von Kármán equations of large deflection problems, is abandoned. First, based on the mechanical model on the neutral layer, the bimodular functionally-graded property of materials is modeled as two different exponential functions in the tensile and compressive zones. Thus, the governing equations of the large deformation problem are established and improved, in which the equation of equilibrium is derived without the common small-rotation-angle assumption. Taking the central deflection as a perturbation parameter, the perturbation method is used to solve the governing equations, thus the perturbation solutions of deflection and stress are obtained under different boundary constraints and the regression of the solution is satisfied. Results indicate that the perturbation solutions presented in this study have higher computational accuracy in comparison with the existing perturbation solutions with small-rotation-angle assumption. Specially, the computational accuracies of external load and yield stress are improved by 17.22% and 28.79% at most, respectively, by the numerical examples. In addition, the small-rotation-angle assumption has a great influence on the yield stress at the center of the bimodular functionally-graded circular plate.

Dynamic analysis of a Drum Charger: Large amplitude vibrations of clamped circular thin plate on a linear foundation

The Impulse Drum Charger® (IDC) represents a valid and innovative alternative in the field of the superchargers, in particular when the available space is limited, such as in motorcycles. In fact, with respect to the traditional one, which uses turbine-compressor system for engine supercharging, the IDC exploit the deflection of an elastic membrane-spring system to generate overpressure at the intake from the pressure waves generated by the exhaust gases. In this way, the aim of this work is the development of a mathematical model of the membrane-spring system, both realized in 102-RGUD600 glass fiber composite (PA matrix), of a Drum Charger® using Von Karman theory with Berger's approximation. Focusing on the central deflection of the membrane in time and frequency domain, the derived models reproduces with good accuracy the results of the complete finite-element simulations computed with Ansys™, especially in the higher frequencies. Moreover, in order the system work properly, the spring behavior must maintain in linear-elastic range. Hence, a three-point bending test of the spring was carried out, following the specifications in ASTM (D790-03), in order to verify the force-displacement linear relation. The numerical simulations shown excellent agreement with the force-displacement curve observed in the experimental tests.

Finite element simulation for investigation on thermal post-buckling of geometrically imperfect GOP-reinforced beam

In this paper, a finite element (FE) simulation has been provided for investigation on thermal post-buckling of geometrically imperfect beams reinforced with graphene oxide powders (GOPs). To this end, a higher-order refined beam theory has been utilized to model the reinforced beam with uniform and non-uniform GOP content. Thus, the employed FE simulation contains a refined beam element in which shear deformations have been considered. Therefore, the degrees of freedom due to both bending and shear displacements have been included. It is also considered that the beam is in thermal environment leading to the thermal buckling at elevated temperatures. The first buckling mode shape of the beam has been considered as the geometrically imperfect configuration. The calculated post-buckling loads of a GOP-reinforced beam are shown to be dependent on several factors including graphene oxide volume, graphene oxide distribution, geometry imperfectness and also center deflection.

Evolution Mechanism and Stability Analysis of Roof Deflection of Composite Structure Roadway Under Dynamic Load Disturbance

The lithology of the roof of the mining roadway is compound and the thickness of each layer varies considerably, and it is disturbed by dynamic load all the year round. The above factors has caused a huge difference in the stability of the roadway surrounding rock. Taking the 11,020 lower tunnel of a mine in Henan Province as the engineering geological background, using on-site investigation, formula derivation, numerical simulation and other methods, the composite roof roadway model group was established to study the deflection evolution characteristics of the surrounding rock under dynamic load disturbance, and summarize the plastic zone of the surrounding rock of the roadway Deformation and evolution of roof surrounding rock to evaluate the stability of surrounding rock with different roof structures. The research results show that the change of the roof surrounding rock structure will also lead to the change of the center deflection of the roadway roof. Therefore, the center deflection of the surrounding rock of various roof composite structures is different, and the deflection is the most direct indicator of the stability of the surrounding rock. The center deflection (\(\omega_{0}\)) of the soft rock type is the largest, the center deflection (\(\omega_{0}\))of the upper soft and the lower hard type, and the soft and hard type is larger, and the soft and hard progressive type, thin, hard and thick soft type (\(\omega_{0}\)) is the smallest, and the dynamic load The relationship between the magnitude of deflection before and after the disturbance is consistent. By constructing a composite roof roadway numerical model group, using the plastic failure zone of the roadway as the evaluation standard, the surrounding rock stability is evaluated and divided, and then the cross-point field measurement method is used to verify the stability of the surrounding rock on the roof of different composite structures. And the development of composite roof roadway surrounding rock deformation and failure mechanism and numerical simulation method has important theoretical significance and practical value for the analysis and control of composite roof roadway surrounding rock stability.

An investigation of impact resistance capacity of polypropylene (PP) added plasterboard subjected to soft-body impact

Plasterboard is one of the most-commonly used construction materials because of its low cost and easy installation characteristics. Although the low strength and fragility make plasterboard functioned as non-load-bearing components. Plasterboard walls are always required to satisfy impact resistance against impact from accidental body strike, hard-body impact from wheelchair, etc. during its usage. This study investigates the impact resistance capacity of plasterboards being subjected to soft-body impact load. Laboratory sandbag impact tests are conducted to examine the responses of plasterboard and PP fibre strengthened plasterboard system at different velocities. Detailed numerical models of plasterboards are also generated to assist the analysis. Different damage and failure modes are observed on the plasterboards when subjected to impactor strike at different velocities. It is found that the coupled deformation of plasterboard and sandbag leads to different impact load time histories from sandbag soft impact, which results in the different failure modes. The PP fibre strengthened board exhibits better impact resistance than conventional plasterboard. Parametric study is then conducted to quantify the peak central deflections under different strength and thickness variances on plasterboard. An empirical formula is then derived based on the parametric results for preliminary assessment of the plasterboard impact resistance capacity.

Impact response of a novel sandwich structure with Kirigami modified corrugated core

A novel Kirigami modified corrugated core was proposed recently and its superior crushing performance under static loading was demonstrated. The proposed core is modified from the conventional corrugated core using Kirigami design, where a portion of the corrugated sheet is cut and then folded vertically. The vertical fold-ins of Kirigami modified corrugated core provide extra support and constraints to the adjacent un-folded cell walls, which increase the crushing resistance of a unit cell up to 10 times as previously studied. However, for a panel with multiple unit cells, its longitudinal flexural stiffness and impact resistance could be affected because of the fold-ins. This study investigates its performance and energy absorption under dynamic crushing through pendulum impact tests. Four configurations of panels, including laminated flat plate (FL), conventional corrugated (CC), Kirigami modified corrugated 1 (KC1) and Kirigami modified corrugated 2 (KC2) were tested. Different impact mass, velocities as well as impacting locations were considered. Impact force and rear face centre deflection were measured and compared to evaluate the impact performance of the panels. Superior impact resistance was demonstrated for proposed KC panel over CC panel under all impact scenarios.

Nonlinear vibration behavior of doubly-curved functionally graded piezoelectric microshells in thermal environments

In this paper, nonlinear vibrational behaviors of doubly-curved functionally graded piezoelectric (FGP) microshells in thermal environments have been studied. The doubly-curved microshell has been modeled by using modified couple stress and thin shell theories. The microshell has two material constituents which are piezoelectric materials and their gradation is described using power-law functions. Temperature fields are considered to be uniform, linear, and nonlinear. A closed-form of nonlinear vibration frequency has been obtained by analytically solving the governing equations using the Harmonic balance method. It will be demonstrated that nonlinear vibrational frequency of doubly-curved microshell relies on couple stress influence, material gradation, curvature radius, center deflection, and electrical field.

New approximate analytical solution of the large deflection problem of an uniformly loaded thin circular plate with edge simply hinged

In this paper, the large deflection problem of an uniformly loaded circular plate with edge simply hinged is considered. First, a new algorithm for the deflection problem is proposed based on Adomian decomposition method. Then, a new approximate analytic solution of the large deflection problem is obtained by the algorithm. Final, its bending moments are analyzed corresponding to different center deflections. And the relationship between the center deflection and the external load is discussed. Through comparing the errors of the obtained approximate solution with the previous perturbation solution and homotopy perturbation solution, one can see that the obtained solution in this paper is a better one and the result in this paper has a certain practical value.

Bending analysis of functionally graded sandwich plates using the refined finite strip method

In this study, static analysis of functionally graded (FG) sandwich plates is performed using the finite strip method based on the refined plate theory (RPT). Two types of common FG sandwich plates are considered. The first sandwich plate is composed of two FG material (FGM) face sheets and a homogeneous ceramic or metal core. The second one consists of two homogeneous fully metal and ceramic face sheets at the top and bottom, respectively, and a FGM core. Differential equations of FG sandwich plates are obtained using Hamilton's principle and stiffness and force matrices are formed using the finite strip method. The central deflection and the normal stress values are obtained for a sinusoidal loaded FG sandwich plate and the accuracy of the results are verified against those obtained from other theories such as the classical plate theory (CPT), the first-order shear deformation theory (FSDT), and the higher order shear deformation theory (HSDT). For the first time, this study presents a finite strip formulation in conjunction with the RPT to analyze FG Sandwich plates. While the proposed method is fast and simple, it is capable of modeling a variety of boundary conditions.

Multiscale based finite element modeling for the nonlinear bending and postbuckling analyses of some noncarbon nanomaterials

Multiscale based finite element model developed in the framework of the Cauchy–Born rule is employed to investigate the nonlinear response of some noncarbon nanosheets considering geometric and material nonlinearities. The Tersoff–Brenner type interatomic potentials with newly calibrated empirical parameters are employed to model the atomic interactions. The quadratic-type Cauchy–Born rule is used to couple atomic entities with entities at the continuum scale. A four-node Kirchhoff-type finite element is used for the continuum approximation of the different nanosheets. The governing finite elemental equations are derived through the principle of minimum potential energy and Newton–Raphson method is used to linearize the nonlinear algebraic equations. The nonlinear bending response of the noncarbon nanosheets, with clamped boundary conditions, subjected to uniformly distributed and central concentrated load is reported in detail. The present results obtained from the multiscale based finite element method are also supported with molecular static simulations for some cases. The postbuckling response of the nanosheets subjected to uniaxial in-plane compression is also reported. The effect of initial strain on the central deflection of nanosheets under distributed and central point load is also investigated in detail and few interesting findings are revealed.

Crack Width Estimation Using Measurements of Central Deflection in ASTM C1609/C1609M

Abstract The ASTM C1609/C1609M beam test, Standard Test Method for Flexural Performance of Fiber-Reinforced Concrete (Using Beam with Third-Point Loading), has been used for assessing the flexural performance of fiber-reinforced concrete (FRC) for many years. The procedure involves the application of third-point loading to a relatively short, simply supported beam that consequently cracks and experiences extension and pull-out of fibers across the crack. The flexural performance of FRC tested in this way is normally expressed as a function of vertical deflection at the center of the beam. This is limiting because central deflection is specific to this test and is difficult to relate to structural applications. However, the two halves of the cracked beam experience essentially rigid-body rotation about the crack, raising the possibility that the maximum crack width can be calculated as a function of central deflection. Crack width is a more useful assessment parameter because it can be related to many structural applications. In the current investigation, seven FRC mixtures were produced and tested in accordance with ASTM C1609/C1609M, with both central deflection and crack width measured in all tests. The maximum crack width was then calculated as a function of central deflection and compared with the measured values. The results indicate that crack width can be calculated with sufficient accuracy using only the central deflection and crack offset from the center, thereby permitting flexural performance to be expressed as a function of crack width without any change to the current test procedure. The coefficient of variation in postcrack flexural strength was found to be slightly smaller for the same set of specimens when expressed as a function of maximum crack width rather than central deflection.

Novel photostrictive 0-3 composites: A finite element analysis

Simultaneous action of photovoltaic effect and converse piezoelectric effect will induce the photostrictive effect. In contrast to the naturally occurring photostrictive material, the present study proposes a 0-3 photostrictive composite. The current photostrictive composite comprises of poly{4,8-bis[5-(2-ethyl-hexyl) thiophen-2-yl] benzo[1,2-b:4,5-b′] dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethyl-hexyl) carbonyl] thieno[3,4-b] thiophene-4,6-diyl} (PTB7-Th) as organic photovoltaic polymer matrix and Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-35PT) as the particulates. The current study shows that the present 0-3 photostrictive composite is a suitable alternative for the most popular lead-based photostrictive material. While evaluating all the effective elastic, dielectric, piezoelectric, and pyroelectric properties of 0-3 photostrictive composite, the effect of local fluctuations was incorporated in representative volume element (RVE) using the finite element method. A finite element formulation using a degenerated shell element is derived to simulate the actuation response of the proposed 0-3 photostrictive composite. Numerical studies have been performed on cantilever and simply supported beams. The maximum tip and center deflection of cantilever beam and simply supported beam bonded with 0-3 photostrictive patch is mm and mm, respectively. The maximum value of the effective piezoelectric coefficient effective thermal expansion coefficient effective Young’s modulus and effective pyroelectric coefficient of proposed 0-3 photostrictive composite are m/V, 4.59 1.63 N/m2, and 7.57 C/m2 K, respectively, obtained at 25% volume fraction of particulates. This study opens possibilities of photostrictive coupling in composites.

공작기계의 공작물 장착과 탈착을 위한 4축 스카라형 로봇 설계

This paper describes the design of a 4-axis SCARA-Type robot in the form of a scalar robot for the loading and unloading of workpieces in machine tools. The 4-axis dedicated robot is a 4-degrees-of-freedom robot consisting of a joint 1, 2, 3 motor and a 180° rotating gripper made up of a horizontal gripper and a vertical gripper. It was designed in a scalar shape that is suitable for machine tools, and the size of each link and elbow was determined through structural analysis. Through additional structural analysis, the deflection of the end center of the workpiece fixed to the horizontal gripper and the vertical gripper was designed to be within 0.1 mm, and based on the design result, a 4-axis SCARA-Type robot was manufactured, and the basic motion characteristics of the manufactured robot were tested. As a result of the characteristic test, the manufactured 4-axis SCARA-Type robot operated smoothly, so it is judged to be adequate for usage in loading and unloading the workpieces in machine tools.