Quasi-static Compressive Properties Research Articles

Effect of recycled polymer fibre on dynamic compressive behaviour of engineered geopolymer composites

To enhance the cost-effectiveness and sustainability of engineered geopolymer composites (EGC), polyvinyl alcohol (PVA) fibres in EGC can be partially replaced with recycled tyre polymer (RTP) fibres. This paper presents a systematic experimental study on the effects of PVA fibre volume fraction (1.0%, 1.5% and 2.0%) and RTP fibre content (0.25%, 0.5%, 0.75% and 1.0%) on the dynamic compressive behaviour of EGC under various strain rates (54.43–164.13 s−1). Results indicate that the flowability, quasi-static compressive strength and elastic modulus of EGC reduce with the increase of PVA fibre content, where the reductions can be effectively mitigated by adding RTP fibres. The dynamic compressive properties of all investigated mixtures including dynamic compressive strength, dynamic increase factor (DIF) and energy absorption capacity show a pronounced strain rate dependency which can be well described using the proposed equations for DIF against strain rate ranging from 10−5 s−1 to 103 s−1 with R2 values of mostly greater than 0.9. The dynamic compressive properties of EGC are enhanced with the increasing PVA fibre dosage under various strain rates while replacing PVA fibre with a certain amount of RTP fibre (0.25% and 0.5%) can result in better dynamic compressive properties compared to EGC with 2.0% PVA fibre. EGC containing 1.75% PVA fibre and 0.25% RTP fibre can be considered as the optimal mixture given its superior quasi-static and dynamic compressive properties in comparison with EGC with 2.0% PVA fibre.

Effects of multi walled carbon nanotubes and multilayer graphene on the damping and quasi-static compressive mechanical properties of novel EP/ZA22 composites

In order to develop novel high damping materials with excellent compressive mechanical properties and energy absorption capacity to meet the needs of buffering and vibration reduction in various fields, epoxy resin (EP) filled foam Zn-22Al (ZA22) composites were fabricated for the first time. EP can significantly improve the damping and compressive mechanical properties of the ZA22 foam due to the superposition of multiple damping sources and the support of EP to pores, respectively. However, the filling of EP will lead to brittleness in the compression process of the composites. It is found that the addition of multi walled carbon nanotubes (MWCNTs) or multilayer graphene (MLG) to EP can efficiently improve the toughness of the composites because of the increased energy consumption in the fracture process of EP, and the damping can also be further improved due to the increased interface density and the amount of polymer chains involved in friction.

Finite element analysis of pitting corrosion on mechanical behavior of E690 steel panel

PurposeThe purpose of this study is to analysis the pitting corrosion on the mechanical behavior of E690 high-strength steel sandwich panel. The pitting corrosion depth and degree of pitting (DOP) damage were used to evaluate the mechanical behaviors such as peak load and specific energy absorption of E690 panel.Design/methodology/approachThe mechanical behavior of quasi-static compression, low-speed impact and three-point bending of E690 panel after pitting corrosion was simulated by ABAQUS nonlinear finite element method.FindingsThe quasi-static compression and low-speed impact mechanical properties can be greatly reduced by the pitting corrosion of the panel core, the pitting corrosion of the outer panel shows no obvious effect. The mechanical properties decrease with the increase of the pitting corrosion depth and DOP, and the influence of DOP is greater than that of pitting corrosion depth. The DOP of outer panel has less effect on mechanical properties of three-point bending compared with that of the core. Therefore, the pitting corrosion in the core of panel should be strictly controlled to prevent adverse effects on the mechanical properties of the structure.Originality/valueTo make up for the deficiency of the research on the corrosion behavior of high-strength steel sandwich panel structure, this paper chose E690 high-strength steel panel as the research object, and nonlinear finite element method was adopted to simulate the influence of pitting corrosion coverage area and pitting depth on its mechanical property degradation. The quasi-static compression, low-speed impact and three-point bending mechanical properties of panel with various DOPs and pitting depths were systematic studied.

Mechanical Properties and Constitutive Model of Selective Laser Melting 316L Stainless Steel at Different Scanning Speeds

To investigate the effects of different scanning speeds on the mechanical properties of selective laser melting 316L stainless steel (SLM 316L SS), process specimens with scanning speeds at 350 mm/s, 650 mm/s, 950 mm/s, and 1250 mm/s were prepared using the SLM technique in this paper. The quasistatic and dynamic compressive mechanical properties of the four specimens were tested by electrohydraulic servo experimental machine and Hopkinson compression bar experimental device, and the mechanical differences of the specimens were analyzed by microscopic observation. Finally, the modified Johnson-Cook (J-C) model was adopted to describe the dynamic mechanical properties of SLM 316L SS. Results showed that the four process steel specimens exhibited typical viscoplastic characteristics and significant strain rate strengthening effects in the mechanical property tests. Moreover, the scanning speed significantly affects the internal defects and melt pool characteristics of the SLM 316L specimens, and the yield strength decreases significantly with the disappearance of the melt pool characteristics. Finally, the modified J-C model can better describe the mechanical behavior of SLM 316L SS material more accurately. This study can provide theoretical references for improving the fabrication process of SLM 316L SS to broaden the practical application of this material.

Crushing behavior and energy absorption of a bio-inspired bi-directional corrugated lattice under quasi-static compression load

The dactyls of Odontodactylus scyllarus have been proved to be an exceptionally damage-tolerant natural material that can readily smash mollusk shells, crab exoskeletons or other hard-shelled preys. In the present study, inspired by the microstructural features of the impact region in the dactyl of Odontodactylus scyllarus, a novel lightweight bi-directionally corrugated lattice was designed and manufactured by additive manufacturing technology to enhance impact energy absorption capacity. The quasi-static compressive properties and energy absorption behavior of the bi-directionally corrugated lattices were investigated experimentally. The compression responses were simulated by finite element (FE) models to duplicate the deformation process. A parametric analysis based on the validated FE model was conducted to study the effects of wave number, wave amplitude and relative density on collapse mode and energy absorption characteristic of the corrugated lattice structures. The collapse process of the bi-directional corrugated lattices can be mainly classified into three representative failure modes, including the full-folded mode, the global buckling mode and the transitional mode. It was found that the specific energy absorption of the corrugated lattice has a strong connection with the three representative collapse modes. With the same relative density, the lattices collapsed with a transitional mode have better energy absorption than those collapsed with a global buckling mode. Due to the higher energy absorption capacity and crushing force efficiency, the corrugated structures collapsed with a transitional mode are more efficient and suitable to act as an energy absorber than those collapsed with the other collapse modes.

The effect of supplementary cementitious material systems on dynamic compressive properties of ultra-high performance concrete paste

Supplementary cementitious materials (SCMs) have been widely used to replace cement in UHPC, which benefits to reducing CO2 emissions and declining construction costs. However, the influence of SCMs on the dynamic compressive properties of Ultra-high performance concrete (UHPC) paste has not been well understood. Here, the workability, pore structure, quasi-static compressive strength and dynamic compressive properties of UHPC paste with different SCM systems are comprehensively studied. The results show that the substitution of cement by ground granulated blast furnace slag (GGBS) and limestone powder (LP) increases workability. With the substitution rate of 10% LP, the microstructure of M2 becomes denser. With the further increasing replacement of GGBS and LP, the porosity increases, while the quasi-static compressive strength and dynamic compressive properties trend to decrease, but the extent is limited. The compressive properties such as dynamic compressive strength, dynamic increase factor (DIF), peak strain and toughness are highly dependent on the strain rate. An applicable DIF model for UHPC is established at the strain rate of 53.9 - 170.7 s−1. The fractal dimension increases with the rising of GGBS and LP. Additionally, a positive linear relationship is observed between the fractal dimension and the denary logarithms of the strain rate.

The Microstructure and Quasi-Static Compression Properties at Elevated Temperatures of the Aged Vacuum Die-Casting Mg-4al-4(La, CE) Alloy

The Microstructure and Quasi-Static Compression Properties at Elevated Temperatures of the Aged Vacuum Die-Casting Mg-4al-4(La, CE) Alloy

Preparation and Quasi-Static Compression Properties of Hybrid Aluminum Matrix Syntactic Foam Reinforced with Glass Cenospheres and Silicon Carbide Nanowires

Preparation and Quasi-Static Compression Properties of Hybrid Aluminum Matrix Syntactic Foam Reinforced with Glass Cenospheres and Silicon Carbide Nanowires

Experimental and modeling investigations on the quasi-static compression properties of isotropic silicone rubber-based magnetorheological elastomers under the magnetic fields ranging from zero to saturation field

The isotropic magnetorheological elastomers (MREs) containing three different contents of carbonyl iron particles (CIPs) based on silicone rubber were prepared, and their quasi-static compression properties under various magnetic fields were characterized by a material testing machine with specialized electromagnet. The magneto-induced actuation stress at zero strain condition as well as the deformation stress during compression process of MREs were tested. According to the magnetization model and demagnetizing energy theory, a magneto-induced actuation model of isotropic MREs was proposed. Meanwhile, a magneto-hyperelastic model was established for calculating the magnetic field- and strain-dependent deformation stress of MREs via combining the Neo–Hookean model, the magnetization model, and the magnetic dipole theory. Therefore, a new constitutive model was established to describe compression properties of isotropic MREs by considering the magneto-induced actuation and the magneto-hyperelastic behaviors. Finally, the effect of CIP content and model applicability were analyzed. It is verified that the developed compression model was able to exactly predict the compression properties of isotropic MREs with various CIP contents over the magnetic field range varying from zero field to saturation field by adopting a set of unified model parameters.

Quasi-Static, Dynamic Compressive Properties and Deformation Mechanisms of Ti-6Al-4V Alloy with Gradient Structure

Gradient structure metals have good comprehensive properties of strength and toughness and are expected to improve the dynamic mechanical properties of materials. However, there are few studies on the dynamic mechanical properties of gradient structured materials, especially titanium alloys. Therefore, in this study, ultrasonic surface rolling is used to prepare a gradient structure layer on the surface of Ti-6Al-4V, and the quasi-static and dynamic compressive properties of coarse-grained Ti-6Al-4V (CG Ti64) and gradient-structured Ti-6Al-4V (GS Ti64) are investigated. The results show that a GS with a thickness of 293 µm is formed. The quasi-static compressive strength of GS Ti64 is higher than that of CG Ti64. Both CG Ti64 and GS Ti64 exhibit weak strain hardening effects and strain rate insensitivity during dynamic compression, and the compressive strength is not significantly improved. The lateral expansion of CG Ti64 is more obvious, while the lateral side of GS Ti64 is relatively straight, indicating that uniform deformation occurs in GS Ti64. The α phase in the GS produces dislocation cells and local deformation bands, and the lamellar structure is transformed into ultrafine crystals after dynamic compression. Both of them produce an adiabatic shear band under 2700 s−1, a large crack forms in CG Ti64, while GS Ti64 forms a small crack, indicating that GS Ti64 has better resistance to damage. The synergistic deformation of GS and CG promotes Ti-6Al-4V to obtain good dynamic mechanical properties.

Preparation, microstructure and compressive property of NiTi alloy hollow spheres fabricated by powder metallurgy

NiTi alloy hollow spheres were prepared using a powder metallurgy at 1100 °C, 1150 °C, 1170 °C and 1200 °C in vacuum sintering furnace. The effects of different sintering temperatures on thin-wall porosities, microstructural evolution and quasi-static compression properties of NiTi alloy hollow spheres were studied. The results showed that NiTi alloy hollow spheres with good surface quality are obtained at 1200 °C. The thin-wall porosity decreases with increasing sintering temperature, while the uniformity of thin-wall thickness increases. The number of pores decreases during sintering process, while the pores with large size grow bigger and become spherify. The NiTi alloy hollow spheres mainly consist of the predominant NiTi phase (B2 and R), and precipitated phases Ti2Ni, Ni3Ti and Ni4Ti3. The size of Ti2Ni increases first and then decreases with increasing sintering temperature, while the Ni3Ti phase continuously and uniformly precipitates at grain boundary. Compressive strength of NiTi alloy hollow spheres increases with increasing sintering temperature, and increases to 189 MPa when sintering temperature reaches to 1200 °C. The loading-unloading curves of hollow spheres revealed that the hollow spheres show superelastic behavior to a certain extent. The fracture characteristics of sintered NiTi alloy hollow spheres were also addressed in this work.

Dynamic mechanical response and damage mechanisms of nacre-inspired 2024Al/B4C composite at elevated temperature

In this study, the nacre-like 2024Al/B4C composites with a lamellar-interpenetrated architecture, virtually free of pores and cracks, were fabricated through combining freeze casting with pressure infiltration, and their quasi-static and dynamic compressive properties were investigated over the temperature ranged from 25 to 500 °C. The dynamic compressive strength and strain were greater than quasi-static ones due to strain-rate hardening and adiabatic heating softening mechanisms. Regardless of strain rates, the compressive strength decreased with temperature, while the failure strain increased. This could be explained by four main fracture phenomena including cracking of B4C and intermetallic compounds (IMCs), matrix deformation and interfacial debonding. The matrix deformation prevailed actively at high temperatures, with a reduced overall trend towards cracking and interfacial debonding. The interfacial debonding and particle cracking acted as the dominant factors that deteriorated the compressive behavior, whereas the soften matrix induced by elevated test temperatures effectively blocked the crack propagation that favorably worked for the strain. As the temperature was raised, the softened matrix destabilized particle skeleton with the deformation behavior of the composites determined by the alloy matrix. However, recrystallization occurred within the alloy matrix, accompanied by a reduction in dislocation density, which degraded the strength of the composites. The elevated temperatures significantly enhanced the strain rate sensitivity of the composites because of the matrix softening yielding a greater proportionate enhancement of particle stress at high temperature than at low temperature.

Quasi-Static Compression Properties of Bamboo and PVC Tube Reinforced Polymer Foam Structures.

In recent years, there has been a growing interest for composite materials due to the superior capability to absorb energy and lightweight factor. These properties are compatible to be utilized in the development for transportation system as it can reduce the fuel consumption and also minimize the effect of crash to the passenger. Therefore, the aim for this project is to study the compression strength and energy absorbing capability for Polyvinyl chloride (PVC) and bamboo tubes reinforced with foam. Several parameters are being considered, these being the effect of single and multiple tube reinforced foam structure, foam density, diameter of the tube as well as effect of different crosshead speed. The results showed that increasing the relative foam density will led to an increase in the compression strength and specific energy absorption (SEA) values. Furthermore, a significant increase of compression strength can be seen when several tubes are introduced into the foam while SEA remained almost the same. Finally, the influence of crosshead below 20 mm/min did not vary significantly for both compression strength and SEA.

Morphological and mechanical characterisation of three-dimensional gyroid structures fabricated by electron beam melting for the use as a porous biomaterial

Additive manufactured porous biomaterials based on triply periodic minimal surfaces (TPMS) are a highly discussed topic in the literature. With their unique properties in terms of open porosity, large surface area and surface curvature, they are considered to have bone mimicking properties and remarkable osteogenic potential. In this study, scaffolds of gyroid unit cells of different sizes consisting of a Ti6Al4V alloy were manufactured additively by electron beam melting (EBM). The scaffolds were analysed by micro-computed tomography (micro-CT) to determine their morphological characteristics and, subsequently, subjected to mechanical tests to investigate their quasi-static compressive properties and fatigue resistance. All scaffolds showed an average open porosity of 71–81%, with an average pore size of 0.64–1.41 mm, depending on the investigated design. The design with the smallest unit cell shows the highest quasi-elastic gradient (QEG) as well as the highest compressive offset stress and compression strength. Furthermore, the fatigue resistance of all unit cell size (UCS) variations showed promising results. In detail, the smallest unit cells achieved fatigue strength at 106 cycles at 45% of their compressive offset stress, which is comparatively good for additively manufactured porous biomaterials. In summary, it is demonstrated that the mechanical properties can be significantly modified by varying the unit cell size, thus enabling the scaffolds to be specifically tailored to avoid stress shielding and ensure implant safety. Together with the morphological properties of the gyroid unit cells, the fabricated scaffolds represent a promising approach for use as a bone substitute material.

Study on the Axial Quasi-Static Compression Properties of Molded Regular Hexagonal Glass Fiber Tube

Five kinds of regular hexagonal glass fiber single tubes with wall thickness were fabricated by molding pressing method. The quasi-static compression test was performed on the glass fiber tubes using a universal testing machine. Then, the failure mode in the compression process was analyzed and the influence of the cell wall thickness on the energy absorption performance of the glass fiber composite thin-walled tube was explored. The results show that the single glass fiber tube appears to fold inward or outward and the fiber at the corner of the hexagonal was torn during the quasi-static compression process. With the increase of the wall thickness, the glass fiber tube appears to be layered, in the compression process, the direction of crack propagation is along the fiber direction (0 °/90 °), the PCF, MCF and SEA all increase with the increase of cell wall thickness, and the value increases sharply when the cell wall thickness increases from 0.8 mm to 1.0 mm, the minimum specific energy absorption is 9.72(j/g), the maximum specific absorption energy is 35.73(j/g), and the crack fracture zone has significant effect on the specific absorption energy.

Improving sintering kinetics and compositional homogeneity of Inconel 625 superalloy open-cell foams made by suspension impregnation method

Open-cell Inconel 625 superalloy foams were prepared by suspension impregnation method which involves replication of pure nickel foam ligaments with a mixed powder suspension and subsequent heat treatments. The objective of the present study is to find a suitable method ensuring complete densification of the superalloy foam ligaments without using low-melting additives and achieving uniform chemical composition at moderate sintering temperatures. Foams prepared using the above methodology were evaluated for the microstructure and compositional variation across the foam ligaments by scanning electron microscopy (SEM) coupled with electron dispersive spectroscopy (EDS). Quasi-static compressive properties of the foams were evaluated. It is shown that if elemental powders of Cr, Mo and Ni are used as additives to the superalloy powder suspension, high ligament density with uniform chemical composition conforming to the Inconel 625 specification is achieved at moderate sintering temperatures. These results are attributed to the formation of low melting eutectics and to acceleration of the diffusion kinetics due to the non-equilibrium thermodynamic conditions created by large compositional gradients in the presence of elemental powders.

Three-Dimensional Mesoscopic Investigation on QuasiStatic Compressive Properties of Coral Aggregate Concrete

Three-Dimensional Mesoscopic Investigation on QuasiStatic Compressive Properties of Coral Aggregate Concrete

Microcapsule mechanics: Quasi-static compressive properties and the effect of liquid core

Liquid-filled microcapsules with a core-shell structure have been developed and widely applied in multi-functional materials. Mechanical properties of microcapsules play a vital role in production, collection and re-processing. Nevertheless, their mechanical behaviors have not been comprehensively understood. In this study, poly urea-formaldehyde (PUF) shelled microcapsules with paraffin oil are selected for experiments. Intrinsic mechanical properties of the shell material obtained from nanoindentation test and uniaxial compression test show remarkably good consistence. Both experimental and simulation results unprecedentedly reveal that the liquid core has a significant effect on the mechanical properties of a microcapsule by enhancing the stability and facilitating the stretching of the shell under compression, especially at large deformations. Moreover, the relationship between the rising hydrostatic pressure and the structural deformation is found to nicely follow up a quadratic function. When the structural deformation increases, plasticity successively appear at the circular contact area, contact edge, and non-contact area of the shell.

Development of dynamic constitutive model of epoxy resin considering temperature and strain rate effects using experimental methods

Epoxy resin composite materials are increasingly used in the aerospace field. The dynamic mechanical behavior of the resin matrix is of great significance in studying the impact response of composites. In the current study, the quasi-static and dynamic compression properties of TDE86 epoxy are studied at different temperatures, and the influence of the temperature and strain rate on the mechanical properties of epoxy are analyzed. The quasi-static and dynamic compression stress–strain curves are used to fit the parameters of the Zhu–Wang–Tang (ZWT) constitutive equation at different temperatures. A subroutine for the ZWT constitutive model is developed in ABAQUS, and numerical simulations of split Hopkinson pressure bar tests are performed. The results show that, at low strain rates, the elastic modulus, yield stress, and yield strain of the epoxy increase as the strain rate increases and decrease as the temperature increases. The dynamic stress–strain curve of the epoxy can be divided into four stages, namely the initial elastic, yield, strain softening, and unloading stages. There is no distinct relationship between the yield strain and the logarithmic strain rate under high strain rates, although the yield strain is generally smaller than that under low strain rates. The yield stress increases linearly with the logarithmic strain rate. Under the same strain rate, the yield stress decreases as the temperature increases, whereas the yield strain does not change monotonically. By comparing the stress–strain curves obtained by simulations with the test results, the developed subroutine is validated and the applicability of the ZWT constitutive model at different temperatures is verified.

Statistical analysis for cost effective process parameters and localized strain hardening behavior of Al-7050 foam

Cost effective process parameters of fabricating Al-7050 foam were obtained by reducing amount of blowing agent and processing time in advancement of low cost, low density and high mechanical properties for structural applications. Quasi-static compressive properties and localized plateau deformation behavior were studied. Maximum strength to density ratio up to 40.38 MPa/(gm/cm3) with utilizing 0.2 wt% TiH2 was achieved. Localized brittleness of plateau cell walls were observed by localized strain hardening behavior in plateau deformation.