Dynamic Loading Conditions Research Articles

Influence of strain rate on the work hardening, strain induced martensite formation, strain partitioning, and variant selection in a medium-Mn steel

In this study, we investigated the effect of strain rate on the work hardening, strain-induced martensite transformation, strain partitioning, and crystallographic variant selection in a medium-Mn steel. Uniaxial compression tests were performed under quasi-static and dynamic loading conditions at the strain rates of 10−3, 1 and 103s−1. Besides, to determine the contribution of temperature rise due to adiabatic heating at a higher strain rate, compression tests were carried out at 409 K (estimated temperature rise) under quasi-static conditions. The work hardening rate was higher at high strain rates and it rapidly decreased at all strain rates up to a true plastic strain of ∼0.05. Beyond the true plastic strain of ∼0.05, the work hardening rate increased at a low strain rate up to a true plastic strain of ∼0.15 while at a high strain rate, it remained relatively constant and gradually decreased beyond a true plastic strain of ∼0.15. From the analysis of microstructures obtained from electron backscatter diffraction, it was observed that the strain-induced transformation of retained austenite to α′-martensite is significantly impeded at higher strain rates and in the sample tested at 409 K at low strain rates. The higher stability of retained austenite is attributed to the adiabatic heating which decreases the chemical driving force for retained austenite to martensite phase transformation and increases the stacking fault energy. Analysis of the misorientation axis and angle evolution revealed that while the Kurdjumov–Sachs relationship was followed under quasi-static conditions, it deviated at higher strain rates. Analysis of crystallographic variants related to strain-induced martensitic transformation at a true plastic strain of ∼0.15 revealed that the samples deformed at a lower strain rate did not show any noticeable variant selection. However, in samples deformed at a higher strain rate, a significant variant selection was observed. It is reasoned that the martensitic transformation nucleates initially on favorably oriented habit planes of retained austenite grains at all strain rates and other variants get activated with an increase in strain. As the transformation is impeded beyond a critical strain at a higher strain rate, the variants activated at lower strains remains predominant.

Comparative analysis of dynamic load characteristics of artillery steering gear based on different MBD methods

The multi-body dynamics analysis model of the steering gear of a certain type of artillery was established. The dynamic load characteristics of the output gear of the steering gear motor and its driven gear under the given speed and load conditions were calculated based on the three different MBD analysis methods, such as the speed, meshing force, and contact stress. Through the comparative analysis, it was concluded that the calculation results of rigid-flexible coupling analysis were closer to the theoretical value and the fluctuation range was smaller, which provides reference and basis for the prediction of gear fatigue life and the optimization design under dynamic load conditions.

Experimental study on the dynamic strength characteristics of combined heavy metals contaminated soil with nZVI treatment

Nanoscale zero-valent iron (nZVI), a high-performance nanomaterial, can treat heavy metal contaminants and is extensively employed for in-situ treatment of groundwater and contaminated subsoil. However, there are few studies that indicate trends in the dynamic strength parameters of nZVI-treated soils to assess site safety. In this study, three heavy metal contaminants, Zn(II), Pb(II), and Ni(II), were selected to contaminate virgin soil. The heavy-metal-contaminated soil was treated with nZVI at two concentrations (a low dose and high dose of 0.5% and 2%, respectively) of the soil's dry mass. Analyses of particle size distribution revealed a consistent shift towards larger particles upon nZVI treatment, and the percentage of sand gradually increased. Heavy metal contamination decreased the liquid and plastic limits of the virgin soil, while those of the treated soil increased with nZVI content. The dynamic triaxial results showed significantly lower maximum dynamic shear modulus for MS, MS-LdN, and MS-HdN than for NS. The damping ratios of all samples showed an S-shaped trend. Thus, nZVI has the potential to create cemented structures and immobilize heavy metals. However, its effectiveness is significantly modulated by the initial water content of the soil. While the application of nZVI proves beneficial in immobilizing heavy metal contaminants, careful consideration is imperative under dynamic loading conditions.

Dynamic tensile properties of a novel high strength and high toughness bolt steel: Constitutive models and microstructures

With the continuous increase of depth in underground engineering, rock bursts or rock explosions can cause instantaneous shock load and result in rock engineering disasters. To solve these problems, a novel high strength and high toughness (HSHT) bolt steel with constant resistance and large deformation is proposed. This study aims to investigate the dynamic constitutive models and microstructure of HSHT steel under extreme loading conditions. A series of dynamic tension tests were conducted using a Split Hopkinson Tensile Bar (SHTB) system with a high-speed camera. The results revealed that the HSHT steel exhibited a positive strain rate effect. As the strain rate increased from 1000 s−1 to 5000 s−1, the yield strength and ultimate strength of the HSHT steel increased gradually. However, no obvious changes in the uniform elongation. Specifically, the yield strength, tension strength, and uniform elongation of strain rate at 5000 s−1 were 1100 MPa, 1170 MPa, and 30%, respectively. According to the results of the SHTB tests, a modified Johnson-Cook model was proposed. Additionally, we investigated the microstructure of HSHT steel at a high strain rate through microscopic characterization techniques. A large number of fine and deep dimples were observed near the fracture of HSHT steel under dynamic loading. Moreover, the HSHT steel demonstrates a significant presence of nano-twins, which effectively impedes crack propagation both within the grain interior and along grain boundaries. The above findings reveal the relationship between mechanical behavior and microstructure in HSHT steel within dynamic loading conditions, providing valuable insights for the design of HSHT steel in underground engineering.

Parametric Analysis on the Static and Modal Response of Folded Metamaterials

Metamaterials have been studied and analyzed in the past three decades because of their outstanding properties. Generally speaking, a metamaterial is a material that exhibits a mechanical behavior that does not depend only on the bulk material but also on the geometrical configuration in which it lies. This aspect leads to the possibility of tuning and engineering the structural response. One of the most interesting properties is the auxetic behavior of metamaterial. An auxetic material shows a global negative Poisson’s ratio. Shock absorption, acoustic dissipation, and shape morphing are some of the most popular employment for auxetic materials. In this article, we focus on the response of folded material under static and dynamic load conditions. Folded materials consist of folding a sheet under specific geometrical constraints. One of the most famous is the Miura-ori pattern, which comes from the origami-folding technique. The geometrical parameters, such as folding angles and edge lengths, play a fundamental role in achieving the desired auxetic behavior. These geometrical parameters define a unit cell that can be stacked into a periodic structure. This article proposes an experimental parametric study of the thickness impact on the auxetic behavior while edge dimensions and folding angles are fixed. The geometrical complexity of the pattern forced us to use additive manufacturing for the specimen fabrication. In particular, we choose Fused Filament Fabrication (FFF) using polymers like ABS and PLA. Digital Image Correlation (DIC) is used for monitoring the displacement and strain fields onto the Miura-ori surface under tensile load. Finally, Time Averaged Speckle Interferometry is employed for evaluating the modal response by using a quasi-full out-of-plane sensitivity setup.

PMSM motor drive and their control schemes

This paper investigated different control Techniques of Permanent magnet synchronous motor (PMSM) drive with open loop, voltage/frequency (V/F) control, closed-loop Space Vector Pulse Width Modulation (SVPWM) control, and sensor-less Modified Space Vector Pulse Width Modulation (MSVPWMM) control with MATLAB/Simulink. The different applications of commercial used required different control schemes due to cost-effectiveness. In a small commercial application where not much precision is required, open-loop or V/F control is used, due to their easy calculation and implementation and becomes a low-cost product outcome. Where their high precision has required closed-loop control is being adopted. In this paper, closed-loop SVPWMM and sensor-less MSVPWM techniques are proposed. The algorithm has a very fast response and output has fewer glitches, highly efficient. Constant speed response available at desired load. The control techniques have been modeled and simulated in MATLAB simulation software. The proposed scheme provides efficient performance in steady-state and dynamic load conditions.

Prediction of long-term creep response: accelerated characterization of industrial nylon6,6 and HMLS PET filaments

The performance of polymeric materials in dynamic loading conditions and their long-term reliability are the two main issues practitioners in the composite field face today. The purpose of this study was to construct master creep curves for industrial nylon6,6 and high modulus-low shrinkage polyethylene terephthalate (HMLS PET) filaments in order to predict their long-term performance. Here, the procedure to develop the master creep curves with short-term creep strain of industrial filaments was investigated under different isothermal conditions in the glass transition region. Nylon consistently exhibits a higher short-term creep strain than PET by around 5–10% based on its lower tensile modulus. Then, master creep curves were developed to foresee the creep of yarns for almost two decades (∼20 years) by the Time-Temperature Superposition principle shift factors. Based on the shift factors derived from master curves, PET and nylon have constant activation energies over the temperature range tested, implying that their creep mechanisms remain constant regardless of the temperature. Overall, rapid prediction of filament creep behavior and lifetime using this method is proposed.

Fatigue-Life Prediction of the Optimized Savonius Vertical-Axis Wind Turbine Composite Blades

Abstract The sustainability of modern human civilization is significantly concerned with enhancing sustainable energy resources. Vertical-Axis Wind Turbines (VAWTs) gained a promising impact on the global energy mix due to their belief in sustainable energy solutions. This paper presents an integrated study of the dynamic performance and fatigue-life characteristics of the optimized Savonius-rotor VAWT composite blades. Furthermore, this paper introduces an experimental validation, numerical modeling, and visualization/verification study of the optimized VAWT composite blades and assesses its impact on the whole performance of the optimized Savonius VAWTs. Four combination levels of the optimal settings of the S-VAWT composite blade configurations are designed, modeled, simulated, and fabricated of Carbon/Glass—Polyester. The modal parameters such as natural frequency, mode shape, and damping factor are investigated using fast Fourier transformer (FFT) analyzer. The numerical finite element models (FEM) are generated to model, visualize, simulate, and predict the dynamic nature and fatigue-life characteristics of the optimal S-VAWT composite blade configurations. A correlation between the experimental and numerical results is established. The study findings highlight the significant impact of VAWT composite blades in enhancing the dynamic performance and fatigue-life characteristics of Savonius VAWTs. Furthermore, a small damage percentage of 2.8% predicted by the finite element analysis (FEA) for the optimal S-VAWT composite blade configuration validated the sustainability of the VAWT composite blade configurations in dynamic loading conditions.

Sustainability of Existing Phase of Extruded Fiber-Reinforced Polylactic Acid under Dynamic Shock Loading Conditions

Sustainability of Existing Phase of Extruded Fiber-Reinforced Polylactic Acid under Dynamic Shock Loading Conditions

Response and Damage Characteristics of Segmental Tunnel Lining under Various Dynamic Load Conditions

Response and Damage Characteristics of Segmental Tunnel Lining under Various Dynamic Load Conditions

Experimental investigation of dynamic bond behaviors between LRS-FRP and concrete

The dynamic bonding behaviour at the interface between a large-rupture-strain fibre-reinforced polymer (LRS-FRP) and concrete was investigated via drop weight impact tests of notched beam specimens. The main experimental variables included the concrete strength grade, number of LRS-FRP layers, and loading rate. With increasing loading rate, the location of the peeling damage at the interface between the LRS-FRP and concrete shifted from the interior of the concrete layer to the concrete–binder layer interface, binder layer, and even binder layer–FRP interface. The ultimate debonding load of the LRS-FRP strips increased with increasing strain rate, reaching more than 1.7 times the static value at a strain rate of approximately 4/s, while the effective bond length did not show a clear increasing or decreasing tendency with increasing strain rate. For the local bond-slip relationship, both the peak interfacial bond stress and interfacial fracture energy increased with increasing strain rate, and the influences of the concrete strength and number of FRP layers on the strain rate sensitivity were insignificant. Based on the experimental results, improved models to predict the ultimate debonding load and effective bond length at the LRS-FRP–concrete interface under both static and dynamic loading conditions were proposed. Furthermore, dynamic increase factor (DIF) formulas for the peak interfacial bond stress and interfacial fracture energy for bond-slip modelling of the interface between a polyethylene naphthalate (PEN)-FRP and concrete were established.

Fabrication, mechanical, finite element and In vitro evaluation of 3D printed polylactide/biphasic calcium phosphate composite blends

Polylactic acid (PLA) reinforced with biphasic calcium phosphate mixtures were extruded as filaments and subsequently 3D printed into definite shapes in accordance with the ASTM standards. The optimum combination of PLA and BCP to attain a stable 3D printed component has been respectively determined as 80 and 20 wt %. BCP inclusions in the range of 2.5 and 5 wt % in PLA led to a respective upsurge ∼11 % in tensile strength and ∼15 % upsurge in compressive strength than pure PLA. While excess BCP additions led to a decline in the material strength. Further, representative volume element models were developed using the properties of BCP and PLA to build ASTM models for performing Finite element analysis (FEA) under both static and dynamic loading conditions. FEA results specified good uniformity with the experimental mechanical data. In vitro tests ensured the biocompatibility of 3D printed PLA-BCP composites.

Test and prediction for the shear behavior of the sand–irregular concrete interface under constant and dynamic normal loading

Pile foundations commonly withstand dynamic loading, which calls for a detailed analysis of cyclic shear properties at the pile–soil interface. This research entailed a sequence of direct shear tests on sand and concrete with irregular surface under both constant and dynamic normal loading, employing joint roughness coefficients (JRC) of 0.4, 5.8, 9.5, 12.8, and 16.7, and varying initial normal loading of 100, 150, and 200 kPa. Results showed that dynamic normal loading diminished the shear strength at the sand–concrete interface and hastened the onset of shear displacement at peak shear stress. Increased surface roughness and initial normal loading mitigated the detrimental effects of dynamic normal loading on this interface. A specific surface roughness was identified as critical for maximizing shear stress under both constant and dynamic normal loading conditions. Furthermore, an increase in the initial normal loading enhanced the interface shear strength. Dynamic normal loading also reduced the interface dilatancy, which could be further influenced by changes in surface roughness and initial normal loading. Notably, dynamic normal loading caused a phase shift in shear stress relative to normal stress, lessened by increased surface roughness. The study introduced a shear strength prediction method for the sand–irregular concrete interface under dynamic normal loading, validated through comparison with experimental data.

Forecasting model for hypoid gear elastohydrodynamic lubrication considering entrainment effect

In full consideration of time-varying meshing performance and oil film characteristics, entrainment effect on elastohydrodynamic lubrication (EHL) is developed for establishing accurate forecasting model of the complex hypoid gears. Firstly, dynamic loaded tooth contact analysis (DLTCA) is employed to determine the meshing interface kinematics, load distribution and entrainment speed under dynamic load condition. Then, entrainment speed is introduced into the EHL governing equation and accurate forecasting model is established. With accurate discretization of EHL governing equation, discrete convolution and fast Fourier transformation (DC-FFT) method is employed to compute the flank elastic deformation. Finally, a hypoid gear set in automotive industrial application is exercised to verify entrainment effect on EHL assessment in the proposed model.

Surface strengthening mechanism of graphene-oxide membrane and its modified aluminium lamina under penetration loading

The contact surface is crucial in determining the ability of membranes or laminas to absorb energy during penetration. This study conducted experiments to explore the mechanical properties of the pristine graphene oxide (GO) membrane when dry, as well as the anti-penetration performance of four surface-modified GO membranes (dry, oil, water, and grease) under various loading velocities. Dynamic penetration occurs when the kinetic energy exceeds a specific threshold, as opposed to the quasi-static outcomes. Additionally, the examination of failure mode indicated that the GO membrane demonstrates significant elastic rebound when subjected to comparatively lower levels of dynamic loading. Further analysis after penetration revealed a transition from brittleness to ductility under dynamic loading conditions. Uniaxial tensile tests of aluminium sheets revealed a distinct negative velocity sensitivity behaviour. Moreover, surface treatment with the GO membrane can enhance the penetration failure strength and energy absorption capacity of the sheet. This study provides crucial insights into the physical principles governing the energy absorption of membrane structures and how they are influenced by surface conditions.

An undrained dynamic strain-pore pressure model for deep-water soft clays from the South China Sea

With the increasing use of oceans for engineering purposes, such as the installation of suction anchors and pipelines, the stability of seabed structures has become a pivotal concern and is intricately linked to the characteristics of seabed soils. This study focuses specifically on deep-sea soft clay, a predominant seabed soil type distinguished by its high water content, thixotropy, and low permeability. These clays are vulnerable to destabilization and damage when disturbed, thereby posing threats to seabed installations. While the existing literature extensively examines the cyclic behavior of clay, considering factors such as the pore pressure response and strain and deformation characteristics, there is a notable gap in research addressing the behavior of deep-sea soft clay under comprehensive stress levels and prolonged cyclic loading. In this study, cyclic shear tests of the natural marine clay of the South China Sea were conducted, and the cyclic stress ratio (CSR), overpressure consolidation ratio (OCR), consolidation ratio (Kc), and loading frequency were varied. It was found that the CSR, OCR, and Kc significantly impact the cumulative dynamic strain in deep-sea soft clay during undrained cyclic dynamic tests. Higher CSR values lead to increased dynamic strain and structural failure risk. Subsequently, a dynamic strain-dynamic pore pressure development model was proposed. This model effectively captures the cumulative plastic deformation and dynamic pore pressure development, showing correlations with the CSR, OCR, and Kc, thus providing insights into the deformation and pore pressure trends in deep-sea clay under high cyclic dynamic loading conditions. This research not only furnishes essential background information but also addresses a critical gap in understanding the behavior of deep-sea soft clay under cyclic loading, thereby enhancing the safety and stability of seabed structures.

Математичне моделювання динамічних впливів на будівельні конструкції

The solution of the problem of mathematical modeling of dynamic influences on building structures is considered in general and in connection with important scientific and practical tasks. In modern conditions, special attention should be paid to the problems of taking into account dynamic influences, parameters of load-bearing structures of buildings that affect their structural reliability and safety. For many years, information about catastrophic destruction of buildings and structures has been appearing more often, which are the result not only of errors that arose during the construction of facilities, but also due to dynamic influences that arose during their operation. A buildable technical system will be used in advance with the technical parameters set, which is responsible for the control of the process of the preparation of structures, the installation of the equipment, during the operation and operation. The development will be carried out and the sporud will be constantly used to promote the development of future technologies, the development and the establishment of the future, as well as the development of dynamic developments in the future. In particular, it is important to understand the development of the engineering and geological minds of the spores, as they have known the front deformation of the non-essential axis of the runt foundations. Various methods are used for structural dynamics, such as modal analysis, response spectrum analysis, time analysis, and finite element analysis. These methods include mathematical modeling, numerical simulation, and computational methods to predict the behavior and response of a structure under dynamic load conditions. Knowing the frequency and form of the structure, it is possible to estimate the dynamic reaction of the design to the application. For the purpose of including the transfer of the world, the destruction of internal forces in the real parts of the construction. Analyses of the response to the additional assessment of the characteristics of the construction, the identification of critical areas and the re-conversion, which the project is able to meet the criteria.

Cyclic dynamic-static loading and acoustic emission signal monitoring method of coal in solid–gas coupling environment and its application

Cyclic dynamic-static loading and acoustic emission signal monitoring method of coal in solid–gas coupling environment and its application

Discussion on ‘Insight into enhancing foundation stability with rubber-soil mixtures: A nanofriction study’

Wan and Zaoui (2024) conducted molecular dynamics simulations (MDS) to explore friction dynamics at the rubber-clay interface under the realm of rubber-soil mixtures (RSM). It’s an interesting deviation from the regular RSMs wherein rubber-sand mixtures only have been considered so far. However, it should be noted that the mixing of rubber with clays would result in the creation of heterogeneous mixtures. Furthermore, Wan and Zaoui (2024) have overlooked the effect of moisture, which, in the case of clays, and especially in the case of sodium-montmorillonite, will influence the shearing (which the authors have referred to as sliding) behavior and thus, the friction dynamics. Furthermore, the influence of horizontal stresses and/or confinement, excess pore-water pressure, and interfacial deformation on the RSM have been overlooked, which limit the applicability of the work for the ‘dynamic loading conditions’. These issues emphasize the necessity of a broader perspective on the material properties (viz., particle size, specific gravity, etc.) and environmental influences (viz., loading conditions, moisture, etc.) within RSM, and thus, considering these issues might help in enhancing the scientific understanding and future research in this area.

Rate-dependent augmented finite element method for fast arbitrary crack growth

Experimental observations indicate that fast crack growth often exhibits a rate dependency, which is caused by the viscosity of the material and the dissipation of energy resulting from the branching of microcracks. To address this phenomenon in simulation modeling, this study introduces a rate-dependent augmented finite element method designed for analyzing fast arbitrary crack growth. The method utilizes the maximum principal stress criterion to simulate arbitrary crack growth and predict the path of crack growth. The elements where crack growth is expected are divided into subelements, and they are re-assembled by incorporating rate-dependent cohesive elements between them to construct augmented finite elements. The cohesive elements are based on a rate-dependent trapezoid traction–separation relationship, where the critical traction and fracture toughness are modeled as functions of the separation rate and crack growth speed. The augmented finite elements only contain external nodal degrees of freedom (DoFs), while internal nodal DoFs are condensed. They can be utilized as conventional elements. A numerical algorithm based on the proposed method was developed in this article, and it was implemented in ABAQUS via user element subroutine. The effectiveness of this method and algorithm is validated through an example of dynamic crack growth in a double cantilever beam. The results demonstrate agreement with experimental and computational findings reported in the literature. Additionally, the method was applied to other structures, yielding reasonable outcomes. Analysis of these examples confirms the method’s utility in predicting fast arbitrary crack growth under dynamic load conditions.