Quasi-static Impact Research Articles

Experimental study on test of wheel-rail impact based on iron plate strain of fastener system

The wheel-rail impact load can reach up to 3–4 times the normal wheel load, with two peaks including a high-frequency impact force (P1) and a mid-frequency or quasi-static impact force (P2). To effectively monitor the wheel-rail impact, this study utilizes strain gauges adhered to bottom of iron plates of fastener to measure rail-seat force, and conducts indoor static load and wheel-drop tests. A finite element model is established for verification and analysis. By analyzing the transmission law of the wheel-rail impact, a monitoring method through rail-seat force is proposed. The results reveal that the strain change of the iron plate in the static load test remains stable and exhibits a linear relationship with rail-seat force. Through a full-scale wheel-drop test, it demonstrates that rail-seat force can effectively monitor P2 force of wheel-rail impact. Compared to traditional method of directly adhering strain gauges to rail, the method of adhering strain gauges to iron plate enabled wheel-rail impact invalid test sections measurement. The peak value of wheel-rail impact P2 can be deduced from peak value of rail-seat force under different impact location, impact levels, and elastic pad stiffness. The proposed monitoring method of based on fastener iron plate strain offers a more efficient alternative for identifying wheel defects and rail defects.

Physics-Guided Machine Learning Approach to Safe Quasi-Static Impact Situations in Human–Robot Collaboration

Abstract Following the performance and force limitation method of the ISO/TS 15066 standard, safety of a human–robot collaboration task is assessed for critical situations assuming quasi-static impact. To this end, impact forces and pressures are experimentally measured and compared with limit values specified by ISO/TS 15066. Consequently, such a safety assessment must be repeated whenever something changes in the collaborative workspace or the task, which severely limits the flexibility of collaborative systems. To overcome this problem, in this paper, a physics-guided machine learning (ML) method for prediction of peak impact forces, within predefined modification dimensions of collaborative applications, is proposed. Along with a pose-dependent linearized model, an ensemble of boosted decision tree (BDT) in combination with a feed-forward neural network (NN) is trained with peak impact forces measured at a UR10e robot covering the range of interest. A generic pick and place task with two modification dimensions is considered as an example of the presented methodology. The method yields the maximal safe impact velocity in the collaborative workspace.

Accessing quasi-static impact process by 3D-NPR corrugated metamaterials

The conventional impact process is a quintessential impulse process that causes substantial damage due to the high initial impact force. However, the impact effect can be significantly diminished by making the impulse process quasi-statically by using a three-dimensional negative Poisson's ratio corrugated metamaterial (3D-NPRCM) structure. This paper proposes a novel 3D-NPRCM obtained by folding the 2D-NPRCM. This study examines the crashworthiness properties and impact force of 3D-NPRCM subjected to impact using the finite element method (FEM). The results reveal that the sequential matrix structure has the ability to make impact impulse processes quasi-statically. The effects of various folding angles, arrangements, and geometrical parameters on the properties are also explored. Finally, the 3D-NPRCM is employed in an automobile crash box design. Through axial quasi-static compression simulation, the peak crushing force of the 3D-NPRCM crash box is reduced by 25.374 % from 211.652 kN to 157.946 kN, and the energy absorbed is increased by 23.830 % from 11.259 kJ to 13.942 kJ, compared to the conventional crash box. Through cart lateral impact simulation, the peak crushing force of the 3D-NPRCM crash box is reduced by 18.076 % from 206.9 kN to 169.5 kN, and the compressive displacement is decreased by 9.457 % from 235.8 mm to 213.5 mm. This work presents a novel design proposition for a crash box in vehicle engineering and demonstrates a fresh approach to expand the design of three-dimensional mechanical metamaterials.

Evaluation of quasi static strength of Kevlar/Basalt-Epoxy and Kevlar/Glass-Epoxy Intra-woven composite laminate

The competency in combining the best qualities of materials and high-performance characteristics of the composites results in its wide range of applications. This paper describes the estimation of quasi-static impact properties on Kevlar/Basalt (KB) and Kevlar/Glass fibre (KG) intra-woven 1 × 1, 3 × 3, and 5 × 5 composite laminates based on ASTM D6264 standards. The novelty of this work is the weaving methods used in the fabrication of composites as well as the pattern in which it is intertwined. The Kevlar and basalt are intra-woven by placing one fibre of Kevlar and one fibre of basalt, one over the other to form ‘1 × 1′ configuration (KB1x1). Similar approaches are followed to form the ‘3 × 3′ configuration (KB3x3) and ‘5 × 5′ configuration (KB5x5). The same pattern is followed for Kevlar/Glass fibre. The Kevlar/Basalt and Kevlar/Glass fibre are woven using the manual handloom weaving hybridization method. Quasi-static and impact tests on composites gives an idea on the energy absorption capability and modes of collapse as energy-absorbing capacity is the main requirements for aerospace and ballistic applications. Square-shaped specimens of size 100 mm by 100 mm are cut out from the original composite plates using vertical band saw machine. Specimens are tested using Universal Testing Machine and the values of load at peak in kN and flexural stress in N/mm2 are noted. The damage area of each specimen is observed and calculated. On comparing the data of various intra-woven Kevlar/Basalt (1 × 1, 3 × 3 and 5 × 5) composite laminates with intra-woven Kevlar/Glass fibre (1 × 1, 3 × 3 and 5 × 5) composite laminates, it is observed that Kevlar/Basalt composite laminate, namely KB3 × 3 and KB5 × 5 have higher impact strength. This is due to its superior load-carrying capacity than other laminates. Finally, based on the quasi-static impact property, Kevlar/Basalt KB3 × 3 intra-woven composite laminate reports a greater impact strength thereby offering itself as an alternate material for varied aerospace and ballistic operations.

Bending Characteristics of CFRP Hexagon Honeycombs Stiffened with Corrugated Cores under Transverse Quasi-Static Impact Loading

Bending Characteristics of CFRP Hexagon Honeycombs Stiffened with Corrugated Cores under Transverse Quasi-Static Impact Loading

Experimental and Numerical Investigation of 3D Printing PLA Origami Tubes under Quasi-Static Uniaxial Compression.

The investigation aims to study the effects of temperature and damage constitutive model on the energy absorption performance of polymeric origami tubes under quasi-static impact. The uniaxial tensile responses of 3D-printed polylactic acid (PLA) samples following standard ASTM-D412 have been studied to characterize the mechanical properties at three temperatures: 30 °C, 40 °C, and 50 °C. The damage constitutive model is used to accurately characterize the stress-strain relations of the PLA. Quasi-static compressive experiments are performed on polymetric tubes with different temperatures. The 3D-printed technique is used to ensure the integrated formation of these polymeric origami tubes. The user-defined material subroutine VUMAT for ABAQUS/Explicit has been developed for the damage model. Compared with the results, the observed deformation processes are well captured by the numerical simulations, and the influence of temperature on the axial compression is also analyzed in detail.

Analysis of plastic yield behavior during impact of a rigid sphere on an elastic-perfectly plastic half-space

This paper investigates the plastic yield behavior during the supersonic, transonic and subsonic stages of impact. The frictionless impacts of a rigid sphere on an elastic-perfectly plastic half-space are simulated by the mesh-refined finite element (FE) models without the assumption of the rigid sphere moving at constant velocity. The dynamical characters of stress field and evolutions of the initial plastic zone are analyzed based on the simulations of a wide range of materials and impact velocities. The plastic yielding is found to occur at all the stages of impact. The present investigation shows that impact-induced waves and fast expansion of contact region have great influence on the high stress regions and the evolution modes of the initial plastic zone. A determination method for the stable yield inception is proposed to avoid the disturbances of the observed local unloading at the beginning of the main plastic zone. The critical parameters at the yield inception are extracted and their dependences upon the normalized impact velocity are analyzed. By considering the limitation of the plastic yield, a new velocity criterion is proposed to solve the critical impact parameters by the quasi-static impact theory. The present investigation shows that the impact with relative high impact velocity makes the plastic yielding shallower and reduces greatly the impact force and dynamic indentation required for yielding.

Brittle fracture development through sets of preexisting small-scale cracks under quasi-static and dynamic impact loading

Fracture development and its possible relation with wave motion in a brittle rectangular solid material with sets of preexisting small-scale parallel cracks are investigated. Experimental observations using high-speed cameras under external quasi-static tensile or dynamic impact loading conditions indicate that depending on the inclination angle, length and distribution pattern of cracks, fractures evolve considerably differently. Quasi-static load generally produces dynamic or quasi-static primary fracture with ensuing dynamic secondary retrograde fractures that are initiated at distant positions. Fractures can be arrested and jump easily, often resulting in clusters. Impact-related waves can induce primary fracture moving in both prograde and retrograde directions.

Investigation on impact resistance of hierarchical lightweight lattice structure

Abstract This paper is majorly discussing the impact resistance of hierarchical lightweight lattice structure. Firstly, the unit cells of hierarchical pyramidal lattice structure and traditional single-stage hollow pyramidal lattice structure are designed. At the same time, the concept of relative density is introduced to better demonstrate the impact resistance of hierarchical structure. In this paper, ABAQUS/Explicit software is used to simulate the drop hammer impact simulation of hierarchical structure and hollow structure. The result shows that the impact resistance of hierarchical structure is better than hollow structure. Meanwhile, the samples are prepared by 3D printing, and then quasi-static compression experiment and drop hammer impact experiment are carried out. It is concluded that the bearing and impact resistance performance of the hierarchical structure has obvious improvement than the hollow structure under both quasi-static compression and low-speed drop hammer impact.

Experimental study of the effect of clay nanoparticles on the strength of hybrid sandwich panels under quasi-static loading

The aim of this study is to investigate the effect of clay nanoparticles on the strength of a hybrid sandwich structure with polyurethane foam core with two different densities. The sandwich structure is made of E-glass woven fabric and basalt fiber. Different percentages of clay nanoparticles are 0.0%, 0.1%, 0.3% and 0.5%, respectively. Furthermore, polyurethane foam with two densities of 40 and 140 (kg/m3) was used for the core of the sandwich structure. By force-displacement diagram obtained from quasi-static impact, the experimental studies of the effect of clay nanoparticles and polyurethane foam with different densities in this type of structure were performed. In addition, crashworthiness features including crush force efficiency and energy absorption capability were discussed. Finally, images of the damage surface and the cut view were taken and the results were reported in order to scrutinize the damage in the hybrid structure. The results indicate that with the increase of clay nanoparticles in the resin of the hybrid structure, the performance of the structure against the indenter effect is improved and displays good resistance. Furthermore, the strength of the structure is enhanced by increasing the density of polyurethane foam. Holistically, polyurethane foam prevents the spread of damage in all structures. In samples with foam with a density of 40 (kg/m3), the hybrid structure with 0.0% Nano absorbs more energy and in samples with foam with a density of 140 (kg/m3), has less energy absorption.

Investigation of specific energy absorption of natural fiber honeycomb sandwich structure composite as building construction material application

The usage of incorporating natural fibre in composite material has seen some potential to be used as a future building construction material due to its recyclability, lightweight and high-reliability feature. However, the issue of implementing natural fibre as building construction material in composites material concerns the structural integrity of the material. As the characteristics of the natural fibre honeycomb composite have been discovered more in terms of properties which ranges from its physical and chemical structural composition to the quasi-static impact collapse of the material, the absorption energy of the material in different cell geometry is unknown. Therefore, the purpose of this study involves the testing of the natural fibre honeycomb (NFH) composite made from cement fibre (face sheet) and corn starch (core) with regards to its crushing behaviour when subjected to flatwise compression load according to ASTM D-3410 standard to analyse the performance of energy absorption of NFH composite with different thicknesses of the hexagonal core and cell wall thickness to determine the Specific Energy Absorption of the material. The result obtained shows that the increasing thicknesses of the core and cell wall improves the ability of the composite to absorb more energy and the specific energy absorption is higher when both factors are increased.

Dynamic Response of Electro-Mechanical Properties of Cement-Based Piezoelectric Composites

By employing ordinary Portland cement as a matrix and PZT-5H piezoelectric ceramic as the functional body, 1-3 and 2-2 cement-based piezoelectric composites were prepared. Quasi-static compression tests were performed along with dynamic impact loading tests to study the electro-mechanical response characteristics of 1-3 and 2-2 cement-based piezoelectric composites. The research results show that both composites exhibit strain rate effects under quasi-static compression and dynamic impact loading since they are strain-rate sensitive materials. The sensitivity of the two composites has a non-linear mutation point: in the quasi-static state, the sensitivity of 1-3 and 2-2 composites is 157 and 169 pC/N, respectively; in the dynamic state, the respective sensitivity is 323 and 296 pC/N. Although the sensitivity difference is not significant, the linear range of the 2-2 composite is 24.8% and 61.3% larger than that of the 1-3 composite under quasi-static compression and dynamic impact loading, respectively. Accordingly, the 2-2 composite exhibits certain advantages as a sensor material, irrespective of whether it is subjected to quasi-static or dynamic loading.

ABOUT THE ANALYTICAL SOLUTION OF THE EQUATION OF IMPACT FORCE OF TWO ELASTIC BODIES

A nonlinear differential equation of the force of direct central impact of elastic bodies of revolution, which have a singular point on the boundary contact surface, where its curvature is infinite, is compiled. To determine the coefficients of the equation and the order of its power nonlinearity, the well-known solution of the axisymmetric contact problem of the theory of elasticity, constructed by I. Ya. Shtaermann, is used. In the formulation of the dynamic problem, the classical assumptions of the theory of quasi-static impact proposed by H. Hertz were also used. The constituted equation of impact force is reduced to the Bernoulli equation and its closed analytical solution is constructed, which is expressed in terms of the Ateb-sine. Analytical time dependences of the impact force and the convergence of the centers of mass of elastic bodies are obtained. Compact formulas have been derived for calculating the maxima of these quantities, as well as the durations of the process of compression and impact of bodies. Compact approximations of Ateb-sine by elementary functions are proposed. Thanks to these approximations, it was possible to obtain a fairly simple analytical sweep in time of a fast-flowing mechanical process. Traditionally, in other works such a scan was obtained by numerical solution of the corresponding integral equations that determine the force of an impact. Examples of calculations are given in which the influence of various factors on the main characteristics of a body impact with a small initial velocity is investigated. The limitation on the collision rate is due to the elastic formulation of the problem, where the possibility of plastic deformations is excluded. As a result of this formulation, the need to determine the rate of recovery rate has disappeared, for it is equal to one. Comparison of numerical results is carried out, to which the obtained analytical solutions and the numerical integration of the impact force equation on a computer lead. Small divergences of the results confirmed the accuracy of the derived calculation formulas. Numerical results relate to the impact of a steel body on a fixed rubber half-space, the analogue of which is observed in practice when falling pieces of mineral raw materials on the rolls of a vibration classifier lined with rubber.

Modelling of ductile fracture in ship structures subjected to quasi-static impact loads

A phenomenological failure criterion, which attempts to achieve a tradeoff between simplicity and prediction quality, is developed to predict the fracture behavior of ship structures under quasi-static impact loads. For simplicity, only the dominant physical mechanism remains in the model. In high stress triaxiality regime, it is believed that ductile fracture is mainly influenced by the stress triaxiality, while under low stress triaxiality regime, Lode angle is considered as the key factor in the fracture prediction. Thus, the combined maximum shear stress and Rice Tracey (MSSRT) criterion is developed to cover a wide range of stress states. The calibration parameters in the criterion can be determined from the uniaxial tensile test only, which is suitable for industrial application where available material data are limited.Along with the fracture scaling framework, the developed failure criterion is implemented into the explicit finite element code LS-DYNA, and the performance of the failure criterion is evaluated by making comparisons with a series of indentation tests involving different materials, structural arrangements and indenter sizes. It is shown that the fracture behavior is well predicted by simulations for all cases. Besides, comparisons among different failure criteria are also carried out. It is found that MSSRT criterion could generate more consistent results when compared with other commonly used failure criteria.

Thermo-mechanical variability of post-industrial and post-consumer recyclate PC-ABS

The aim of this work is to investigate the performance variability of post-industrial (PIR) and post-consumer recycled (PCR) polycarbonate acrylonitrile-butadiene-styrene (PC-ABS). In addition, necessary testing methodology for understanding polymer variation in recycled polymers are established. The thermal expansion behaviour of all tested material were found to be similar and FT-IR testing revealed no conclusive evidence of oxidative degradation. Both PIR and PCR exhibited similar levels of variation in mechanical properties compared with prime samples, with the exception of elongation at break and quasi-static impact behaviour. In these two tests, prime polymers showed lower variation and superior performance to both recycled polymers. The presence of defects and changes in molecular weight were determined to be leading causes of the reduced deformability. Our work contributes by identifying key areas where recycled PC-ABS show good potential as replacements for neat PC-ABS. Furthermore, the work demonstrates methods for material testing against performance criteria to pave way for effective replacement of neat PC-ABS with its recycled counterparts.

Manufacturing Optimization and Experimental Investigation of Ex-situ Core-shell Particles Toughened Carbon/Elium® Thermoplastic Composites

Current research investigates the effect of the core-shell (C/SH) particles in composites manufactured using novel thermoplastic Elium® resin and carbon fiber reinforcement of different areal weights, 200 gsm and 400 gsm bi-angle non-crimp carbon fabrics (NCCFs). The core-shell particles were activated using the ex-situ methodology which involves the activation of particles before the Resin transfer molding (RTM) injection process. Recommended particle activation parameters are established after carrying out a detailed microscopic study to understand the melting and flattening behavior of these particles. Static indentation and damping attributes are studied to understand the influence of C/SH particles added novel carbon/Elium® composite in improving the out-of plane properties and dynamic mechanical attributes respectively. The interply regions were also toughened with the addition of 1% core-shell particles and the intensity of load drop has reduced by 20% while comparing the thick and thin ply NCCF/Elium® composites. Microscopic examination has shown that the core-shell particles helped to spread the damage evenly throughout the specimen and absorbed more energy during the static-indentation. Loss factor or damping for thick ply Elium® composite and thin ply epoxy composite is increased by 19% and 16.4% with the addition of 5% and 1% C/SH particles respectively. The underlying reasons for improvement offered by C/SH particles in quasi-static impact and dynamic mechanical tests are also deliberated in this paper.

Effect of rebar spacing on the behavior of concrete slabs under projectile impact

In this paper, the effect of different steel bar configurations on the quasi-static punching and impact response of concrete slabs was studied. A total of forty RC square slab specimens were cast in two groups of concrete strengths of 40 and 63 MPa. In each group of twenty specimens, ten specimens were reinforced at the back face (singly reinforced), and the remaining specimens were reinforced on both faces of the slab (doubly reinforced). Two rebar spacing of 25 and 100 mm, with constant reinforcement ratio and effective depth, were used in both singly and doubly reinforced slab specimens. The specimens were tested against the normal impact of cylindrical projectiles of hemispherical nose shape. Slabs were also quasi-statically tested in punching using the same projectile, which was employed for the impact testing. The experimental response illustrates that 25 mm spaced rebars are effective in (I) decreasing the local damage and overall penetration depth, (II) increasing the absorption of impact energy, and (III) enhancing the ballistic limit of RC slabs. The ballistic limit was predicted using the quasi-static punching test results of slab specimens showing a strong correlation between the dynamic perforation energy and the energy required for quasi-static perforation of slabs.

Evaluation of impact ductile fracture behaviour of low carbon austenitic stainless steel SUS304L using damage mechanics model

To clarify the applicability of the Gurson-Tvergaard-Needleman (GTN) model for impact ductile fracture behaviour, SHB test was reproduced by finite element analysis (FEA). The strain-rate dependence of the strength for austenitic stainless steel JIS SUS304L was obtained by tensile tests at quasi-static strain rate and impact strain rate. The CowperSymonds power law, which takes into the strain-rate dependence of strength, and the GTN model implemented in the commercial FEA code were used to simulate for impact ductile-fracture behaviour. GTN model parameters were determined by minimizing the difference between the simulated and measured stress-strain curve using response surface method. SHB test was simulated using GTN model obtained from quasi-static tensile test result. Simulation results did not occur the necking and fracture on the specimen. The fracture surfaces were observed by SEM micrograph. The appearance of ductile fracture since dimples are observed, regardless of the strain rate. It is necessary to adjust the parameter to accelerate the nucleation of the void. By identifying the GTN parameters in consideration of the strain rate dependence including impact strain rate. It would be possible to improve the simulation accuracy of impact ductile fracture behaviour.

Manufacturing of 3D Printed Laminated Carbon Fibre Reinforced Nylon Composites: Impact Mechanics

This paper presents the manufacturing development of laminated Carbon Fibre Reinforced Thermoplastics Polymer (CFRTP) specimens, which show significant improvement of mechanical properties in comparison with existing thermoplastic composites. There is a need to improve structural performance of thermoplastic composites by using a fully integrated chopped and continuous carbon fibre bundle into a thermoplastic resin matrix in a laminated shape with various stacking sequences. The developed manufacturing technique is capable to print components with various fibre orientations, which is spotted as the novelty of this research. The CFRTP specimens were tested under quasi-static tensile and low-velocity impact loading to proof the improvement of mechanical performance in both static and dynamic applications. Our results indicate a significant improvement in impact resistance and energy absorption capability of CFRTP composites in comparison with existing thermoplastic composites.

Dynamic Tensile Testing of Needle-Punched Nonwoven Fabrics

The tensile testing of a needle-punched nonwoven fabric is presented. A high-sensitivity Split-Hopkinson Tensile Bar device was specifically designed for this purpose. The strain gauge measurements were combined with high-speed photography and Digital Image Correlation to analyse the deformation micromechanisms at high strain rates. The experimental set-up allowed to determine the wave propagation velocity of the as-received nonwove fabric, the evolution of the strain field with deformation and the wave interaction inside the fabric. The deformation was accommodated by the same micromechanisms observed during quasi-static tensile testing and ballistic impact, which comprised fibre straightening, rotation and sliding. Heterogeneous strain fields were developed in the nonwoven fabric as a result of the non-linear pseudoplastic response of the fabric and the internal dissipation due to the frictional deformation micromechanisms, preventing the propagation of high magnitude strain waves into the specimen. Additionally, the output forces were analysed to determine the influence of high-strain rates in the mechanical response of the nonwoven fabric, finding an increment of the stiffness for low applied strains under dynamic loading. These findings provide the basis to develop strain-rate dependent constitutive models to predict wave propagation in needle-punched nonwoven fabrics when subjected to impact loads.