Quasi-static Axial Loading Research Articles

Novel geometric arrangement effects on energy absorption of a conical structure with various cross-sections

In this research, the crushing behavior of interlocking 430 steel conical tubes with different arrangements and cross-sections in both experimental and numerical forms under quasi-static axial load was investigated. New samples were designed, by changing the number of layers, the arrangement of the layers and the geometry of the conical section. A total of seven different arrangements were designed in five different cross-sections (35 modes) and mass retention constant and energy absorption parameters were extracted for them. The non-linear Finite element method of simulation was performed using LS-Dyna software. To evaluate the accuracy of the simulation results, several experimental samples were made and tested by deep drawing method. As the number of layers increased, the amount of specific energy absorption (SEA) of the structure in different arrangements showed a different process, which emphasizes the importance of choosing the type of arrangement of layers for each structure. Also, increasing the number of layers does not necessarily increase the crush force efficiency (CFE), but how the layers are arranged is important. In samples with the same number of layers and the same arrangement, it was found that the change in the cross-section of the structure had a significant effect on the energy absorption of the samples. Choosing a suitable arrangement of the number of layers and their arrangement, while keeping the mass constant and reducing the space occupied for its installation, can improve the SEA up to 81% compared to a sample with improper and poor arrangement and geometry. SEA in a sample with three-layer design, circular cross-section and special arrangement was higher than other samples (21.8 J/g).

Effect of layering layout on the energy absorbance of bamboo-inspired tubular composites

Gradient distribution of vascular structure made the bamboo wall structure so effective which improved the load-bearing capacity of such bio-mimicked energy absorption structures and modify the crush behavior of thin-walled composite tubes. In this research, the influence of the layering design and stacking sequence on the crush behavior, failure mechanism and absorbed energy of bamboo-inspired GFRP composite tubes is assessed experimentally and numerically. Quasi-static compression tests were conducted to explore seven permutations of Coarse Woven (CW), Fine Woven (FW), and Unidirectional (UD) E/glass fiber sheets, taking into account the longitudinal vascular bundles strengthened by organic matrix. Samples were fabricated employing a modified hand laying up method by using mechanical pressure to obtain better surface finishing and interlaminar adhesion compared to conventional hand layering up methods. To evaluate the corresponding crashworthiness parameters and characterize the crushing behavior of composite tubes, quasi-static axial compressive loading was done. The numerical simulations were validated versus experiments by a commercial finite element (FE) LS-DYNA integrating material model 54. The predicted load-displacement curves and failure mechanisms of FE analysis demonstrate acceptable correlations with visual observations during experimentation. Furthermore, the parametric numerical was performed to examine the effect of different distributions of vascular bundles. The FE analysis results revealed that the crushing behavior of bio-inspired composite tubes depended substantially on layering configuration and the stacking sequence design. The outcomes showed that the combination of woven and unidirectional fibers, respectively, located in the inner layer and hoop direction provide the optimal layering configuration design in terms of crush length efficiency, crush load efficiency, Specific energy absorption, stable progressive crushing, and better manufacturing quality.

Crashworthiness analysis of cylindrical tubes with coupling effects under quasi-static axial loading: An experimental and numerical study

In most cylindrical tubes, the occurrence of negative stiffness under compression is unavoidable. This downward trend in the force–displacement relationship means a decrease in the energy-absorption capacity. To this end, this paper introduces a new assembly method comprising two concentric cylindrical tubes. The inner cylinder possesses positive Poisson's ratio behavior, whereas the outer cylinder exhibits negative Poisson's ratio behavior. When compressed, the outer and inner cylinders shrink and expand, respectively, creating surface contacts between the two cylinders, called coupling effects. This property not only avoids the occurrence of negative stiffness in outer cylindrical tube, but also increases the energy-absorption capacity in an upward trend in the force–displacement relationship. To confirm this claim, three different types of cylindrical tubes, possessing positive Poisson’s ratio, zero Poisson's ratio, and negative Poisson’s ratio behaviors, are considered. A finite-element analysis is implemented to simulate deformation patterns of cylindrical tubes. Then, to verify the results of finite-element analysis, a laser-cutting method is applied to fabricate cylindrical tubes from stainless steel tubes. The results show that the proposed assembly method increases the energy-absorption capacity by up to 95% compared to the well-known auxetic tube. Next, a parametric study is performed, in which the gap space between the two cylinders is considered as a design variable. The results reveal the smaller the gap space, the higher the energy-absorption capacity. The absorbed energy in the assembled cylinders without gap space is 17.6 J, which is 36% greater than that of cylinders with 13 mm gap space. The effects of relative density and crushing speed are also evaluated. When compared to the crushing speed, the energy-absorption capacity is highly dependent on relative density.

Helical plating – a novel technique to increase stiffness in defect fractures

Single-plate fixation bridging bone defects provokes nonunion and risks plate-fatigue failure due to under- dimensioned implants. Adding a helical plate to bridge the fracture increases stiffness and balances load sharing. This study compares the stiffness and plate surface strain of different constructs in a transverse contact and gap femoral shaft fracture model. Eight groups of six synthetic femora each were formed: intact femora; intact femora with lateral locking plate; contact and gap transverse shaft osteotomies each with lateral locking plate, lateral locking plate and helical locking plate, and long proximal femoral nail. Constructs underwent non-destructive quasi-static axial and torsional loading. Plate surface strain evaluation was performed under 200 N axial loading. Constructs with both lateral and helical plates demonstrated similar axial and torsional stiffness- independent of the contact or gap situations - being significantly higher compared to lateral plating (p < 0.01). Torsional stiffness of the constructs, with both lateral and helical plates in the gap situation, was significantly higher compared to this situation stabilised by a nail (p < 0.01). Plate surface strain dropped from 0.3 % in the gap situation with a lateral plate to < 0.1 % in this situation with both a lateral and a helical plate. Additional helical plating increases axial and torsional construct stiffness in synthetic bone and seems to provide well-balanced load sharing. Its use should be considered in very demanding situations for gap or defect fractures, where single-plate osteosynthesis provides inadequate stiffness for fracture healing and induces nonunion.

Investigations on crush behavior and energy absorption characteristics of GFRP composite conical frusta with a cutout under axial compression loading

The changes in energy-absorption and deformation characteristics of thin-walled E-glass fiber reinforced composite conical frusta upon introduction cutouts were studied through quasi-static axial compression loading. The 15°, 18° and 21° semi-apical angled conical frusta with a circular, square, and elliptical cutout were axially compressed, and its crush-force-efficiency, energy-absorption, and specific-energy-absorption (SEA) characteristics were analyzed. Further, the ABAQUS® finite element software was used to simulate the crush behavior of perfect and imperfect conical frusta, and the corresponding results were compared with the experimental results, and the results are reported in this article.

Comparative Analysis of Energy Absorption Capacity of Single and Nested Metal Matrix Composite Tubes Under Quasi-Static Lateral and Axial Loading

In this paper the behavior of nested tube systems under quasi-static compressive loading is investigated. Two nested tube systems with metal matrix composite are subjected to compressive loads so that in the system A the exterior and interior tubes are under axial and lateral loads, respectively but in the system B the exterior and interior tubes are under lateral and axial loads, respectively. Furthermore, these systems behavior are studied numerically. The results show that energy absorption capacity for both of nested tube systems is greater than the sum of energy absorption capacities of two constitutive tubes when loaded individually. Also, it is shown that the absorbed energy for system A is greater than that of system B. In this research the effects of section geometry and the condition of loading (axial or lateral)of thin-walled tubes on energy absorption capacity and the value of the peak load are studied both experimentally and numerically.

Crashworthiness Performance of Aluminium, GFRP and Hybrid Aluminium/GFRP Circular Tubes under Quasi-Static and Dynamic Axial Loading Conditions: A Comparative Experimental Study

Offshore structures are exposed to risks of vessel collisions and impacts from dropped objects. Tubular members are extensively used in offshore construction, and thus, there is scope to investigate their crashworthiness behaviour. Aluminium, glass fibre reinforced polymer (GFRP) and hybrid aluminium/GFRP circular tube specimens were fabricated and then tested under quasi-static and dynamic axial loading conditions. Two hybrid configurations were examined: external and internal layers from respectively aluminium and GFRP, and vice versa. The material impregnated with epoxy resin woven glass fabric was allowed to cure attached to the aluminium layer to ensure interlayer bonding. The quasi-static and dynamic tests were conducted using respectively a universal testing machine at a prescribed crosshead speed of 10 mm/min, and a 78 kg drop hammer released from 2.5 m. The non-hybrid configurations (aluminium and GFRP specimens) outperformed their hybrid counterparts in terms of crashworthiness characteristics.

Optimization design in perforated AL-CFRP hybrid tubes under axial quasi-static loading

Induced structure has been widely used in thin-walled structures to reduce the initial peak crash force (PCF) and improve the crashworthiness. In this paper, the perforated aluminum-carbon fiber reinforced polymer thin-walled tube (AL-CFRP tube) was investigated to explore the design issue of the parameters of induced holes. For the purpose, firstly, a finite element model of perforated AL-CFRP tube was established and verified with experiments. Secondly, under the condition of single factor, the effects of different diameter, number and number of rows of induced holes on the AL-CFRP tube were studied respectively. Finally, the response surface method (RSM) was used to analyze the influence of the parameters of the induced holes on the total energy absorption (EA) and initial PCF values of perforated AL-CFRP tube. The non-dominated sorting genetic algorithm II (NSGA-II) was used to seek the optimal combination of the parameters of induced holes. The results demonstrate that the induced holes structure can effectively improve the crashworthiness of AL-CFRP tube, when the parameters of induced holes are a row of holes with a diameter of 5 mm and a number of 4, the PCF can be reduced by 17.43% and the crush force efficiency (CFE) can be increased by 20% without weakening the total EA.

Buckling of unstiffened cone-cylinder shells subjected to axial compression and thermal loading

Numerical and experimental study on the instability of unstiffened mild steel cone-cylinder assembly under simultaneously acting quasi-static axial compression and thermal load is presented in this paper. Results for one model subjected to axial compression were obtained first. Then, the combined action of axial compression and temperature was applied to the remaining four models. There was a good correlation between the experimental data and the numerically obtained buckling load for the cone-cylinders assembly. The percentage difference between experimental to the numerically predicted failure load ranges from +10% to −7%. Finally, the first combined stability domains for cone-cylinder assembly under combined axial compression and temperature was presented. Further study has been conducted to evaluate the buckling effect for cone-cylinder shell subjected to combined loading to the change of these parameters (i) dimensionless radius-to-thickness ratio, rcyl/t, (ii) semi-vertex cone angle, β, and (iii) dimensionless cylinder length-to-cylinder radius ratio, Lcyl/rcyl. Finally, the influence of structural initial imperfection also has been considered by following the recommendation of ECCS (2008).

Experimental studies on quasi-static axial crushing of additively-manufactured PLA random honeycomb-filled double circular tubes

The Voronoi-based random honeycomb cylindrical shell with specific mesostructures was constructed programmatically and additively manufactured on material of polylactide (PLA). Then, a new PLA random honeycomb-filled double circular tube (PLA-RHFDCT) was proposed. The mechanical performance of the PLA-RHFDCTs in terms of deformation mode, crushing response and energy absorption was studied experimentally by carrying out the quasi-static axial compression loading. A parametric study was performed to evaluate the influence of tube sizes and the mesostructures of honeycomb cores on the crushing resistance and energy absorption capacity of the PLA-RHFDCTs. Results indicate that the cell configuration dominates the deformation modes of PLA honeycomb cylindrical structure. For the PLA-RHFDCTs, the deformation and the bearing capacity are mainly determined by the wall thicknesses of tubes. The introduction of PLA honeycomb core enhances the mechanical performance and affects the localized buckling of the PLA-RHFDCTs due to both the in-plane and out-of-plane crushing resistance of honeycomb core structures. Compared with the parameter of cell irregularity, the relative density of honeycomb cylindrical cores exhibits a higher influence on the energy absorption performance of the PLA-RHFDCTs, though the relatively low crushing strength of PLA honeycomb cylindrical structures.

Additive manufacturing of continuous carbon fiber tubes and experimental investigation of the energy absorption capability under quasi-static loading

Additive manufacturing (AM) is becoming increasingly important in the field of mechanical engineering. Therefore, the mechanical performance of this new technology can have a huge impact on the component’s life. Hence, a fourth axis is added to an existing Fused Filament Fabrication printer and a customized slicing strategy is used. To meet the high demands of mechanical strength, a symmetrical layer stack-up with an alternating variation of the inclination angle is printed onto the fourth axis. Each tube consists of eight layers in total. Starting from α = 15° fiber angle [+15,-15,0,0]S up to α = 75° fiber angle with a 15° angle increase. Each layer has a height of t1 = 0.125 mm thickness adding up to a tube wall thickness of tw = 1 mm. These tubes are tested under quasi-static axial loading conditions in a universal testing machine.

Theoretical prediction and analysis of hybrid material hat-shaped tubes with strengthened corner structures under quasi-static axial loading

This paper proposes an innovative hybrid material hat-shaped tube with strengthened corner structures (HMHT-SCS) to overcome the disadvantages of the limited energy absorption capacity and lightweight potential of conventional hat-shaped tubes. First, an improved theoretical prediction model of a corner element is established by modifying the simplified super folding element theory, and analytical formulas for energy absorption are derived under quasi-static axial loading. Second, a prediction model of the HMHT-SCS is developed based on the improved prediction model of corner element. Analytical formulas for the mean crushing force (MCF) of single-hat HMHT-SCS and double-hat HMHT-SCS are derived. Then, the accuracy of the analytical formulas is validated through axial crushing tests and simulation analysis. Finally, a discussion is performed. The total effect generation method is proposed to visually characterise the effects of input parameters on output responses. The parametric study showed that the thickness of the hat element of HMHT-SCS has the strongest effect on the MCF, and the thickness and material type of the hat element have similar effects on mass. The thickness of the corner element has a noticeable effect on MCF, while its section width has the weakest effect on the MCF and mass. Furthermore, the comparative analysis showed that the specific energy absorption (SEA) of the HMHT-SCS is larger than that of conventional hat-shaped tubes with one single material. Additionally, the SEA of the ‘aluminium & steel’ HMHT-SCS is larger than that of the ‘steel & aluminium’ HMHT-SCS under the same flow stress.

Experimental research of absorption properties of rigid foam filled circular seamless tube energy absorber under quasi-static axial load

The aim of this research work is investigations of absorption characteristics of a circular seamless tube collision absorber filled by rigid polyurethane (PU) foam under axial load. Shrinking of circular tube passing through cone bushing starts after absorber is activated at the moment of collision. The energy absorption realises in three ways: elastic-plastic deformation of the tube wall, friction between absorption elements and compression the rigid PU foam inside the tube. Using rigid PU foam, as the seamless tube filler, in the process of collision energy absorption increases absorption power in comparing to with only empty tube, as well as gives gradual increases of deformation resistance during deformation process. Experimental research was prepared and realized in the laboratory using the scaled samples. The effect of rigid PU foam, configuration of absorber filled by PU foam on the absorption power and manufacturing technology of the samples, are considered and discussed in this paper. The results indicate that the shrinking foam filled tube absorber has for about 18% bigger absorption power than the empty one. Formation of numerical model and numerical analyses of shrinking foam filled tube absorber were realized using ANSYS software package. Force vs. stroke (F(s)) diagrams obtained by tests and numerical analyses are in a good correlation which confirms formed numerical model as a suitable for further quasi-static analyses and for dimensioning the similar types of absorber.

Experimental, numerical, and multi-objective optimization investigations on the energy absorption features of single- and bi-layer deep-drawn cups

In this article, the energy absorption features of single- and bi-layer deep-drawn cups (S- and B-cups, respectively) under a quasi-static axial loading are investigated experimentally and numerically. The S-cups were made of 304L stainless steel and explosively welded B-cups were composed of aluminum and 304L stainless steel layers. A multi-objective optimization was performed on specific energy absorption and initial peak force based on the polynomial response surface method. Furthermore, to compare the energy absorption features of deep-drawn cups, two groups of 304L stainless steel tubes (with the same mass or the same height as the S-cups) were axially compressed. The experimental results indicated that the S-cups experienced total energy absorption and mean crush force approximately 24% and 51% greater than those of tubes with the same mass and thickness, respectively. Furthermore, the total efficiency and specific total efficiency of the S-cups were approximately 0.23 and 1.82 times greater than those of tubes with the same height and thickness. Moreover, the energy absorbing effectiveness factor of B-cups was approximately twice of the S-cup.

Effect of infill pattern, density and material type of 3D printed cubic structure under quasi-static loading

The present research work is aimed to investigate the effect of infill pattern, density and material types of 3D printed cubes under quasi-static axial compressive loading. The proposed samples were fabricated though 3D printing technique with two different materials, such as 100% polylactic acid (PLA) and 70% vol PLA mixed 30% vol carbon fiber (PLA/CF). Four infill pattern structures such as triangle, rectilinear, line and honeycomb with 20%, 40%, 60%, and 80% infill density were prepared. Subsequently, the quasi-static compression tests were performed on the fabricated 3D printed cubes to examine the effect of infill pattern, infill density and material types on crushing failure behaviour and energy-absorbing characteristics. The results revealed that the honeycomb infill pattern of 3D printed PLA cubic structure showed the best energy-absorbing characteristics compared to the other three infill patterns. From the present research study, it is highlighted that the proposed 3D printed structures with different material type, infill pattern and density have great potential to replace the conventional lightweight structures, which could provide better energy-absorbing characteristics.

Improvement of energy absorption of expanded metal tubular structures under compressive loads

Herein, several approaches with the aim of improving the crashworthiness performance of expanded metal tubes were assessed experimentally and numerically. In this regard, various expanded metal tubes were produced out of expanded metal sheets including expanded metal tubes, stiffened expanded metal tubes, foam-filled expanded metal tubes and multi-layered expanded metal tubes. Their crashworthiness performance was evaluated under quasi-static axial compressive loading. The effect of cross-sectional type (square and circular) and cell size (large and small) were also evaluated. Results showed the significant effect of cell size on the crashworthiness performance of expanded metal tubes, while the cross-sectional type had negligible effect. Moreover, the energy absorption properties of expanded metal tubes improved through welding expanded metal sheets in the core (stiffened expanded metal tubes), embedding expanded metal tube in foam, and placing several expanded metal tubes concentrically. Among the studied approaches, the foam-filled expanded metal tubes exhibited the most stable compressive load-displacement response, which is desirable for energy dissipation. Furthermore, the load-displacement responses of prepared expanded metal tubes were also predicted acceptably by the proposed finite element modeling. Finally, the effects of expanded metal tube parameters on the crashworthiness performance of tubes were investigated numerically.

Energy absorption of origami tubes with polygonal cross-sections

Thin-walled tubes are widely used as energy absorption devices in transport vehicles. In this paper, with the goal of improving the energy absorption performance of tubes under quasi-static axial loading, origami tubes with polygonal cross-sections are designed. The geometric characteristics of polygonal origami tubes are controlled by three parameters: the number of sides, the number of modules and the dihedral angle. To investigate the effect of the origami pattern and polygonal structure on the crashworthiness of tubes, a full factorial experiment is adopted, and then parametric analysis is conducted based on eighty-five simulations. The numerical results validate that origami tubes collapsing in the complete diamond mode perform better than conventional tubes. However, this special mode can only be triggered in the crushing process of square and hexagonal origami tubes with smaller dihedral angles. The optimal design leads to a maximum reduction in the initial peak crushing force of 56.96% and a maximum increase in the mean crushing force of 45.49%. The parametric study shows that the initial peak crushing force of tubes with an identical number of modules and edges increases with an increasing dihedral angle, while it decreases with an increasing number of modules when the angle remains the same. Additionally, the influence of geometric parameters on the mean crushing force varies with different collapse modes. Furthermore, a deep insight into the in-extensible deformation mechanism of origami tubes deformed in the complete diamond mode is presented. The theoretical model is subsequently proposed to predict the mean crushing force.

Crashworthiness Performance of Multi-Cornered Structures under Quasi-Static Compression and Dynamic Axial Loading Conditions

Crashworthiness Performance of Multi-Cornered Structures under Quasi-Static Compression and Dynamic Axial Loading Conditions

Experimental and numerical studies on failure and energy absorption of composite thin-walled square tubes under quasi-static compression loading

Abstract To analysis the failure and energy absorption of carbon fiber reinforced polymer (CFRP) thin-walled square tube, the quasi-static axial compression loading tests are conducted for [±45]3s square tube, and the square tube after test is scanned to further investigate the failure mechanism. Three different finite element models, i.e. single-layer shell model, multi-layer shell model and stacked shell mode, are developed by using the Puck 2000 matrix failure criterion and Yamada Sun fiber failure criterion, and three models are verified and compared according to the experimental energy absorption metrics. The experimental and simulation results show that the failure mode of [±45]3s square tube is the local buckling failure mode, and the energy are absorbed mainly by intralaminar and interlaminar delamination, fiber elastic deformation, fiber debonding and fracture, matrix deformation cracking and longitudinal crack propagation. Three different finite element models can reproduce the collapse behaviours of [±45]3s square tube to some extent, but the stacked shell model can better reproduce the failure mode, and the difference of specific energy absorption (SEA) is minimum, which shows the numerical simulation results are in better agreement with the test results.

Crashworthiness analysis of multi-configuration thin walled co-axial frusta tube structures under quasi-static loading

Abstract In the present study crashworthiness performance of monolithic and co-axial multi-wall (double, triple, and four layered) frusta tube structures was investigated under the quasi-static axial loading. The developed layered frusta tubular structures having a total equivalent thickness of 2.3 mm were made of aluminium alloy AA-1080 sheet. A series of layered configurations were simulated and analysed using non-linear finite element analysis code LS-DYNA, keeping volume approximately the same as the monolithic frusta tube. For the effectiveness of the simulated results, double-tubular structure was examined through experimental results. A parametric study was performed by keeping taper angle constant as 5.71° with the variation in height (91.6 and 82 mm for double layered, 91.6, 86 and 78 mm for triple layered and 91.6, 87, 82 and 77 mm for four layered), thickness (2.3–0.4 mm) and diameter (smaller end diameter in the range of 42.8 mm–48.4 mm while larger end diameter varied from 61 mm to 64 mm) to analyse the crushing performance of layered structures. The crashworthiness performance indicator like peak force (PF), mean force (MF), energy absorbing capacity (EAC), specific energy absorption (SEA) and crush load efficiency (CLE) which is defined as the ratio of MF to the PF, were studied for the various layered frusta tubular structures. Moreover, optimization technique GRA (Grey Relational Analysis) was employed to obtain a better combination of multi-wall layered structures. With the increase in the layer, the initial peak force was reduced compared to the monolithic frusta. The optimization technique suggested the triple-layer configuration showed better crashworthiness performance.