Quasi-static Axial Loading Research Articles

Zirconium Oxide Three-Unit Fixed Partial Denture Frameworks Supported by Dental Implants in Acceptable and Reduced Interocclusal Space Possibilities: Pilot In Vitro Fracture Strength and Fractographic Analyses.

This study investigated the effect of fracture strength and fracture mode characteristics related to reduced interocclusal space on computer-aided design/computer-aided manufacturing (CAD/CAM). ZrO2 fixed partial denture (FPD) frameworks subjected to quasi-static loads. First, two dental implants (4 × 10 mm) were positioned simulating a three-unit FPD (second premolar and second molar abutments). The implants were distributed into two groups: control group (n = 10), positioned at the same level; and the test group (n = 10), where the interocclusal space corresponding to the second molar was reduced by 3 mm in relation to the second premolar to simulate a clinical situation. After FPD wax-up (25-mm long; connector height = 5 mm; connector width = 3 mm, proximal and lingual collar reinforcement), casting was made in a Co-Cr alloy to serve as a prototype. Upon scanning, screw-retained CAD/CAM ZrO2 FPDs were fabricated for each group. Then, FPDs were subjected to quasi-static axial loading until fracture in the mid-occlusal pontic area using a universal testing machine at the crosshead speed of 0.5 mm/min. Next, the samples were analyzed by scanning electronic microscopy (SEM) to describe the fracture characteristics. The mean fracture strength values for the control group (1,747.4 ± 122.3 N) and test group (1,817.7 ± 158.9 N) showed no significant difference (Student t test, P < .124). The SEM images of the fracture sites revealed two cleavage areas in the test group, providing representative sites with increased fracture energy storage in this group compared with the control group. Within the limitations of this study, the results showed that reduced interocclusal space and reduced length did not decrease the fracture strength of the ZrO2 FPD frameworks.

Crashworthy and Performance-cost Characteristics of Aluminum-CFRP Hybrid Tubes under Quasi-static Axial Loading

Metal/composite hybrid thin-walled structures combine the low cost of metallic materials and the high strength-toweight ratio of composites and thus have the potential to be utilized as cost-effective energy absorbers for vehicle applications. This study aimed to examine the crushing behaviors and performance-to-cost ratio of aluminum/carbon fiberreinforced plastic (CFRP) hybrid tubes under quasi-static axial loading. First, a single aluminum tube, a single CFRP tube and an aluminum/CFRP hybrid tube were tested to validate numerical models. The experimental results showed that the total energy absorption (EA) of the aluminum/CFRP hybrid tube was 32.46 % higher than the sum of that of the individual parts, and the special energy absorption (SEA) of the hybrid tube was improved by 105.26 % compared with that of the single aluminum tube. Then, the effects of the orientation angles ([±15°]n, [±45°]n, [±75°]n, [±90°]n, [90°/0°]n, n=2, 4, 6) and thicknesses of the CFRP tube wall (4-ply, 8-ply, 12-ply) on the crashworthiness of the hybrid tube were studied through validated numerical models. The numerical results showed that as the orientation angle increased, SEA, EA and the mean crushing force (Fmean) decreased first and then increased; in addition, the hybrid tubes with orientation angles of [±45°]n and [90°/0 °]n (n=2, 4, 6) consistently exhibited the worst and best crashworthiness, respectively. Furthermore, the SEA, EA, and Fmean of the hybrid tube increased with increasing thickness of the CFRP tube wall. Finally, the performance-to-cost ratio (SEA/cost) of the hybrid tube was analyzed, and the results show that aluminum/CFRP hybrid tubes with a smaller wall thickness of the CFRP tube exhibits superior potential in terms of both cost and performance for automotive applications.

A three-hinge-line method for calculating the deformation process of thin plates under quasi-static axial loading

This paper presents a modified calculation method for the crushing deformation of sheet metals, which is called the three-hinge-line method (THLM). Through developing the folding mechanism of a thin-walled square tube, the effect of the buckling curvature on thin plates is approximately considered by improving the original single hinge to three hinges, and a method for calculating the distance between the hinges is given. A program is designed for the solution of this problem. In addition to solving for the average force and energy, the deformation process and force-displacement curves are also included. The accuracy of the THLM can be checked by the finite element method (FEM). The good agreement between the methods shows that the compressive forces are predicted satisfactorily from the results of the proposed uniaxial crushing.

Parametric investigation of the mechanical behavior of expanding-folding absorbers and their implementation in sandwich panels core

Thin-walled energy absorbers are one of the common structures that are used in vehicle body for increasing the crashworthiness and consequently decreasing injuries. Investigated new type of thin-walled aluminum matrix and a thin-walled steel punch energy absorber structure has been investigated in this paper. Energy is absorbed as the matrix expansion followed by simultaneous matrix and punch folding. Present study proposes a sandwich panel based on expanding-folding absorber units to evaluate their crush mechanism. Parametric study has been done using finite element code LS-DYNA while experimental tests have been implemented to validate the FE model. The panels have been tested under three axial quasi-static loading conditions including a rigid half-cylinder and a rigid plate. Parametric study considers the punch angle, matrix thickness and punch thickness. The optimum structure based on energy absorption has then been used as a structural member in the sandwich panel until a panel with high specific energy absorption be introduced. Also it have been seen that all the curves for the expansion section can be estimated using polynomial second order functions, with a high accuracy.

RETRACTED: Experimental investigation of parameters affected on behavior of composite tubes under quasi static and dynamic axial loading

Abstract Composite tubes mayhap subjected to impact loads during placement or operation. By determining the impact properties of composite tubes and using them in the design process, the accuracy of the behavior of these structures is guaranteed under dynamic and quasi-static loading conditions. In the present study, the effect of changing parameters such as tube diameter, fiber density and fiber layout on the behavior of glass/epoxy composite tubes under dynamic and quasi-static axial loading is investigated. The Force-displacement diagrams were extracted for all experiments and compared with other experiments. Also, the rate of specific energy absorption of each test was calculated for all samples. The results of this study showed the change of parameters mentioned is effective on the energy absorption of composite tubes. In both groups of dynamic and quasi-static axial tests, variations of fiber density and samples diameter caused to change the specific absorbed energy. But the change in fiber layout from [0.90] to [± 45] reduced the specific absorbed energy. In the following, the results of dynamic and quasi-static tests were compared. Comparison of the results showed that for predicting of the average crushing force of the dynamic test for 10-layer samples with a height of 100 mm and [0.90] fiber layout, the average force of the quasi-static test can be used with coefficients of 1.1–1.3. Also, a model was proposed for predicting the average crushing force, maximum force and sample destruction in the dynamic test according to the quasi-static test results. Also, according to the results, in the dynamic and quasi-static impact tests, increasing the fiber density and internal diameter of the samples, increases the amount of specific energy absorption. In the case of changing the fiber orientation for samples made with 200 gr/m2 and 400 gr/m2 fibers in the dynamic impact tests, compared to quasi-static tests, have a different effect on the amount of specific energy absorption.

Determination of energy absorption in different cellular auxetic structures

This paper deals with the effect of unit cell configuration on the energy absorption response of different cellular auxetic structures subjected to quasi-static and dynamic loadings through the experimental and numerical methods. Among the various structures, a re-entrant structure was selected due to its fundamental properties underlying the main characteristics of an auxetic material. Computer simulation techniques using ABAQUS software validated by experimental testing were used to conduct the evaluation of such devices. Several re-entrant structures with different geometrical parameters were modeled and compared with the conventional ones. Standard compression tests were carried out on the different structures produced by the 3D printing machine to evaluate the influence of auxeticity phenomenon in the energy absorption capability. It is discovered that the auxetic structures are superior to non-auxetic structures in terms of all studied impact resistance and energy absorption indicators due to their ability to withstand quasi-static axial impact loads. The primary outcome of this research is to extract design information for the use of auxetic materials as energy absorbers where quasi-static loading is expected.

Investigation of the numerical, experimental, statistical and optimization of thin-walled energy absorber with novel configuration using response surface method under axial loading

In this study, aluminum thin-walled cylindrical absorbers for crashworthiness are investigated to introduce a novel system with better energy absorption and crushing characteristics under quasi-static axial compressive loading. The inside of the thin-walled cylinders is meshed with a square welded from vertices to the thin-walled cylinder. Here, the response surface method, which is one of the design of experiments techniques has been used to examine the effect of the parameters on energy absorption, initial peak crushing force, specific energy absorption per unit mass and energy absorption per length. The variables of thickness (t), height (h) and length of square (l) of the thin-walled cylinder were considered in three levels and initial peak crushing force, specific energy absorption per unit mass and energy absorption per length were selected as response. The specimens were analyzed under a quasi-static compressive test at a constant speed of 10 mm/min. Subsequently, for further investigation, the experimental results were compared with those obtained from the finite element simulation using Abaqus software, which indicated desirable accuracy. To decrease the solution time in this numerical analysis, the speed was set at 0.5 m/s. Finally, the experimental results were compared with the simulation ones, which showed acceptable compatibility. Further, there are the equations obtained from the multi-objective optimization testing design. The results indicated a linear relationship of thickness with responses, nonlinear relationship of height with responses, linear relationship of length of square with initial peak crushing force, and nonlinear relationship with specific energy absorption per unit mass and energy absorption per length.

Efficient crushable corrugated conical tubes for energy absorption considering axial and oblique loading

Thin-walled structures are of much interest as energy absorption devices for their great crashworthiness and also low weight. Conical tubes are favorable structures because unlike most other geometries, they are also useful in oblique impacts. This paper investigated the effect of corrugations on energy absorption characteristics of conical tubes under quasi-static axial and oblique loadings. To do so, conical tubes with different corrugation geometries were analyzed using the finite element explicit code and the effects of corrugations on initial peak crushing force and specific energy absorption were studied. The finite element model was validated by experimental quasi-static compression tests on simple and corrugated aluminum cylinders. An efficient analytical solution for EA during axial loading was also derived and compared with the FEM solution. The crushing stableness was analyzed using the undulation of the load-carrying capacity parameter and it was shown that corrugations made collapsing mode, more predictable and controllable. The findings have shown that corrugated conical tubes have much better energy absorption characteristics compared with their non-corrugated counterparts. It was also discovered that during oblique loadings, introducing corrugations can significantly increase the specific energy absorption compared with simple cones.

Experiment and simulation to compress destroyed process of novel tailor rolled tubes

A novel tailor rolled tube was manufactured to meet the weight reduction requirement and further improve the energy-absorbing properties. This study aims to investigate the compressive destructive behavior of a novel tailor rolled tube by a compress experiment and computer simulation. Quasi-static axial compressive tests were conducted on tubes of square variable thickness (TRT) and equal thickness (UT) using a hydraulic testing machine. It is shown that the TRT exhibits a lower initial peak force and higher energy absorption, leading to a change in the failure mode. Based on the experimental results, a numerical model using the ABAQUS/Explicit was constructed. The simulation results of deformation behavior and load–deflection performance of square TRT under the axial quasi-static loading show agreement with the results from the experiments. A parametric study was conducted by using the FE model to investigate the effects of the transition zone on the impact collapse characteristics of TRTs. Based on the analytical results, a design recommendation was presented for the novel TRT.

Evaluations of failure initiation criteria for predicting damages of composite structures under crushing loading

The crushing behaviors of thin-walled composite structures subjected to quasi-static axial loading are comparatively evaluated using four different failure initiation criteria. Both available crushing tests of composite corrugated plate and square tube are used to validate the stiffness degradation-based damage model with the Maximum-stress criterion. Comparatively, Hashin, Maximum-stress, Stress-based Linde, and Modified criteria are respectively implemented in the damage model to predict crush behaviors of corrugated plate and square tube. To develop failure criteria, effects of shear coefficients and exponents in the Modified and Maximum-stress criteria on damage mechanisms of corrugated plate are discussed. Results show that numerical predictions successfully capture both of experimental failure modes and load–displacement responses. The Modified criterion and particularly Maximum-stress criterion are found to be more appropriate for present crush models of corrugated plate and square tube. When increasing the failure index, the crushing load is decreased, which also causes premature material failure. The shear coefficient and exponents have dramatic influence on the crushing load. Overall, an insight into the quantitative relation of failure initiation is obtained.

Energy absorption analysis of a novel foam-filled corrugated composite tube under axial and oblique loadings

Composite thin-walled structures are of much interest in differnet applications as well as energy absorption devices for their great crashworthiness and light weight. In this paper, a new corrugated composite cylindrical tube has been introduced in order to improve crashworthiness along with a stable crushing. In cylindrical composite tubes, the effects of corrugations regarding charactristics of energy absorption have underwent quasi-static axial and oblique loading investigations. For this reason, composite cylindrical tubes with different corrugation geometries were analyzed using finite element explicit code and the effects of corrugations on crush force effiency and specific energy absorption were comperhensively studied. The finite element model has been validated by experimental quasi-static compression tests. An efficient analytical solution for SEA during axial loading has been also derived and compared with FEM solution. Furthermore, a comparison of empty and foam-filled corrugated composite tubes has been done. Based on the obtained results, generating corrugated surfaces on tubes improved the crush force efficiency significantly in both axial and oblique crushings. Performing a parametric study on geometrical corrugation parameters of tubes has been indicated that the energy absorption of these structures depends strongly on the corrugation parameters. Furthermore the absorbed energy has been increased by using foams in both axial and oblique crushing. SEA increases by increasing the foam density while the CFE decreases.

Finite element modelling of AA6063T52 thin-walled tubes under quasi-static axial loading

The behavior of aluminum alloy 6063T52 thin walled tubes have been present in this paper to determine absorbed energy under quasi-static axial loading. The correlation and comparison have been implemented for each experimental and finite element analysis results, respectively. Wall-thickness of 1.6 and 1.9 mm were selected and all specimen tested under room temperature standard. The length of each specimen were fixed at 125 mm as well as diameter as well as a width and diameter of the tube at 50.8 mm. The two types of tubular cross-section were examined whereas a round and square thin-walled profiles. The specific absorbed energy (SEA) and crush force efficiency (CFE) were analyzed for each specimen and model to see the behavior induced to failure under progressive collapse. Result showed that a correlation less than 5% different between both of comparison experimental and finite element model. It has been found that the thin walled round tube absorbed more energy rather than square profile in term of specific energy with both of either 1.6 or 1.9 of 23.93% and 35.36%, respectively. Overall for crush force efficiency (CFE) of each tube profile around 0.42 to 0.58 value. Indicated that the all specimen profile fail under progressive damage. The calibration between deformed model and experimental specimen were examined and discussed. It was found that the similarity failure mechanism observed for each thin walled profiles.

Quasi-static axial crushes on woven jute/polyester AA6063T52 composite tubes

Quasi-static axial loading have been studied in this paper to determine the behaviour of jute/polyester wrapped on aluminium alloy 6063T52. The filler material also was include into crush box specimen, which is polyurethane (PU) and polystyrene (PE) rigid foam at ranging 40 and 45 kg/m3 densities. All specimen profile was fabricated using hand layup techniques and the length of each specimen were fixed at 100 mm as well as diameter and width of the tube at 50.8 mm. The two types of tubular cross-section were studied of round and square thin-walled profiles and the angle of fibre at 450 were analysed for four layers. Thin walled of aluminium was 1.9 mm and end frontal of each specimen of composite were chamfered at 450 to prevent catastrophic failure mode. The specific absorbed energy (SEA) and crush force efficiency (CFE) were analyses for each specimen to see the behaviour on jute/polyester wrapped on metallic structure can give influence the energy management for automotive application. Result show that the four layers’ jute/polyester with filler material show significant value in term of specific absorbed energy compared empty and polyurethane profiles higher 26.66% for empty and 15.19% compared to polyurethane profiles. It has been found that the thin walled square profile of the jute/polyester tubes with polystyrene foam-filled is found higher respectively 27.42% to 13.13% than empty and polyurethane (PU) foam tubes. An introduce filler material onto thin walled composite profiles gave major advantage increases the mean axial load of 31.87% from 32.94 kN to 48.35 kN from empty to polystyrene thin walled round jute/polyester profiles and 31.7% from 23.11 KN to 33.84 kN from empty to polystyrene thin walled square jute/polyester profiles. Failure mechanisms of the axially loaded composite tubes were also observed and discussed.

Effects of triggering mechanisms on the crashworthiness characteristics of square woven jute/epoxy composite tubes

The usage of composite materials has been growing widely over the years due to their excellent characteristics such as lightweight, high-energy absorption capability and corrosion resistance. In this study, the crashworthiness characteristics of square woven jute/epoxy composite tubes with different configuration of triggering mechanisms were tested and evaluated when subjected to quasi-static axial loading. The deformation morphology of each composite tube was captured by using high-resolution photography. The composite tubes were fabricated by using the combination of hand layup and compression bladder moulding techniques in which total of three layers of woven bi-directional natural jute fabric (plain weave mat) were used, each with wall thickness and length of 3 mm and 100 mm, respectively. To induce the progressive crushing of composite tubes, four different types of triggering mechanisms were used: the non-trigger, single chamfered trigger, double chamfered trigger and tulip trigger. The influence of energy absorption, crush force efficiency, peak load, mean load and load–displacement history was examined and discussed. From this study, most of the composite tubes failed in progressive manner rather than catastrophic failure. Overall, the tulip trigger configuration is considered the optimal design for crashworthy structure applications.

Optimization of hole height and wall thickness in perforated capped-end conical absorbers under axial quasi-static loading (using NSGA-III and MOEA/D algorithms)

In this study, a perforated capped-end conical steel absorber was investigated to optimize its wall thickness and hole height. The holes were worked out on the perimeter of the absorber to lower peak force at collapse. For this purpose, once finished with simulating the absorber utilizing LS-Dyna software and verifying the simulated model using experimental data, hole height and wall thickness of the absorber were optimized to achieve maximum energy absorption along with minimum peak force. A total of 96 different cases were simulated, of which 7 cases were subjected to experimental tests. The optimization was performed using NSGA-III and MOEA/D algorithms implemented in MATLAB software. Response surface methodology was used to determine input functions for these algorithms. Finally, optimal position for the holes in conical absorbers was found to be the nearest point to the upper base of the truncated cone. A relatively good agreement was observed between the results of NSGA-III and MOEA/D algorithms, and the algorithms could predict optimal wall thickness and hole position at an acceptable accuracy in some cases.

Evaluation of delamination crack tip in woven fibre glass reinforced polymer composite using FBG sensor spectra and thermo-elastic response

This paper details a study which was carried out on the application of FBG sensors for investigation of delamination crack status in glass fibre reinforced composite materials. A woven glass (0/90) epoxy composite sample containing a purposely created delamination and an embedded FBG sensor was investigated to study the behaviour of delamination crack under applied axial quasi-static tensile load. The reflected spectra from FBG sensor and the thermo-elastic response using an infrared camera were recorded to detect the propagation of delamination crack tip. In addition a finite element analysis (FEA) was performed using cohesive elements to simulate delamination crack tip. It has been seen that the propagation of delamination crack tip monitored from thermal stress analysis (TSA) was consistent with the prediction of the FBG sensor response. Further it has been observed that the experimentally observed delamination damage propagation was in a good agreement with FEA simulation results.

Axial Crushing of Prismatic Multi-Corner Metal Columns Considering Plastic Hardening and Curvature

ABSTRACTIn this paper, progressive crushing of prismatic multi-corner thin walled metal tubes under quasi-static axial load is investigated in detail. The novelty of the paper is mainly in considering strain hardening effect during plastic deformation instead of rigid plastic model and also the effect of curvature in forming the folds instead of plastic hinges. For this purpose, a new geometric model based on FEM and experimental observations is used which is capable of being adapted with new crushing configurations during crushing. Based on this model, the instantaneous energy associated with plastic deformation of different regions are calculated and finally by summing all energies and using minimum absorbed energy, mean crushing force and collapse parameters are determined. To evaluate the results, a detailed finite element study using ABAQUS and LS-Dyna solver is conducted on some regular polygonal mild steel tubes under axial crushing. Comparing the results of the new theoretical approach with FEM results show very good capability of that in predicting collapse behavior of these structures.

Experimental and theoretical studies on axially crushed corrugated metal tubes

In this paper, crushing behaviors of tube with shallow and deep corrugation are experimentally and theoretically examined under axial loading condition. Three types of specimens were tested under quasi static axial loading. Their failure mechanism and failure history are presented and discussed. The experimental result showed that corrugated metal tubes demonstrate perfect energy absorption characteristics in terms of uniformity of load–displacement diagram, reduction of initial peak load and controlling failure mechanism. The theoretical solution based on experiment and modified simplified super folding element (MSSFE) theory is proposed that depends on the number of plastic hinge line, wall thickness, length of structure and flow stress of material. The comparison between theoretical solution and experiment shows a good agreement with acceptable errors.

An experimental study on the energy absorption characteristics of single- and bi-layer cups under quasi-static loading

ABSTRACTExperimental testing was conducted to study the mechanical behaviour and energy absorption characteristics of single- and bi-layer cups under axial quasi-static compressive loading. Bi-layer plates were fabricated by explosive welding or joined by adhesive and were formed by a deep drawing process to produce the cup . The tests were performed at a rate of 10 mm/min. The effect of geometric parameters and other apparatus parameters were considered in this study. Results from the experimental tests showed that the layer order of the bi-layer cup significantly influences energy absorption capacities of the cup such that the structures with stainless steel as the outer layer has total absorbed energy and mean crush force 8% and 14% higher, respectively, than those of cups with the aluminium outer layer. Furthermore, it was observed that cups fabricated by explosive welding displayed mean crush force and specific energy absorption 1.5 times greater than those fabricated with adhesive.

The Effects of Triggering Mechanisms on the Energy Absorption Capability of Circular Jute/Epoxy Composite Tubes under Quasi-Static Axial Loading

The usage of composite materials have been improving over the years due to its superior mechanical properties such as high tensile strength, high energy absorption capability, and corrosion resistance. In this present study, the energy absorption capability of circular jute/epoxy composite tubes were tested and evaluated. To induce the progressive crushing of the composite tubes, four different types of triggering mechanisms were used which were the non-trigger, single chamfered trigger, double chamfered trigger and tulip trigger. Quasi-static axial loading test was carried out to understand the deformation patterns and the load-displacement characteristics for each composite tube. Besides that, the influence of energy absorption, crush force efficiency, peak load, mean load and load-displacement history were examined and discussed. The primary results displayed a significant influence on the energy absorption capability provided that stable progressive crushing occurred mostly in the triggered tubes compared to the non-triggered tubes. Overall, the tulip trigger configuration attributed the highest energy absorption.