Impact Conditions Research Articles

Analysis of low-velocity impact on FG-CNT reinforced cantilever sandwich beams: An FOSNDT approach

This study analyzes the low-velocity impact response of cantilever sandwich beams with foam cores and carbon nanotube (CNT) reinforced facesheets. Using the fifth-order shear and normal deformation theory, we explore three CNT distribution types through the thickness of the facesheets: uniformly distributed UD, functionally graded-V FG-V, and functionally graded-Λ FG-Λ. The contact force during impact is calculated according to Hertz contact law. Our findings indicate that the FG-V distribution offers the highest contact stiffness, resulting in reduced deflection compared to UD and FG-Λ distributions. Additionally, an increase in the core-to-face thickness ratio leads to decreased deflection and increased contact force, attributed to enhanced beam stiffness. The volumetric fraction of CNTs also plays a critical role, increased CNT content raises beam stiffness, decreasing deflection and enhancing contact force. Furthermore, the impactor’s initial velocity directly influences the deflection and contact force, with higher velocities leading to greater deflections due to increased kinetic energy. This comprehensive analysis underscores the significant effects of CNT distribution, volumetric fraction, and geometrical parameters on the dynamic response of sandwich beams under impact conditions.

An appropriate approach of design and machining of mechanical part by means of probabilistic multi‐objective optimization

AbstractAppropriate design and machining of mechanical part are of great importance to guarantee the comprehensive quality of product. In this paper, a rational approach of design and machining of mechanical part with multiple objectives is formulated by combining the probability‐based method for multi‐objective optimization with sequential optimization. The probability‐based method for multi‐objective optimization is employed to transfer the problem of multiple objectives into a single objective one in the respect of probability theory, while the “sequential algorithm for optimization” is used to conduct successive deep optimization quantitatively. By performing the assessment of preferable probability of each scheme and the “sequential algorithm for optimization”, the optimal design of materials processing is thus completed rationally. Furthermore, the approach is used to deal with thermal design of spindle system for computerized numerical control grinder, optimal designs of large floor‐type milling and boring machine spindle box and bending performance of B‐pillar under condition of side impact as examples, respectively. The results indicate the rationality of the approach.

High-velocity micromorphological observation and simulation of magnetorheological gel using programmable magneto-controlled microfluidics system and micro-tube dynamic models

Application of magnetorheological gel (MRG) is a promising tool for high performance mitigation due to its outstanding energy absorption and dissipation properties. However, the lack of recognition on micromorphological variation for MRG and its magneto-mechanical coupling mechanism limits its extensive application. Herein, combined with the magnetic sensitivity nature of MRG, we develop a magneto-controlled microfluidic system for flexible simulation toward ms-level impact conditions. Microstructural changes of MRG, prepared with solid–liquid composite method, are characterized from variable magnet-field setups and gradual velocities. Experiments reveal that the increasing magnetic flux density can effectively enhance the stability of chains in as-fabricated MRG, while the chains can support excessive velocities up to 4.5 m s−1 before breaking. Meanwhile, under the preset velocity range, the maximum change rates of the average and standard deviation for inclinations are 183.71% and 40.06%, respectively. Successively, an experiment-conducted microdynamic model is developed for numerical simulation of the MRG mechanical behaviors. During that, high-velocity MRG behaviors are explored with a tubular rather than regular flat-structure boundary condition setups, to pursue more trustable results. Simulation readouts meet nicely with those from experiments in revealing the magneto-mechanical coupling mechanism of MRG under multiphysics. The interaction between magnetic force, repulsive force and viscous resistance is mainly illustrated. This work provides a reliable observation basis for micromorphological variation of MRG, also suggests a new method for the mechanism of magneto-mechanical coupling at extreme velocities.

Exterior cladding in the German architecture of Valdivia. A metaphor of refinement and social distinction

As a result of the colonization process that began in the mid-19th century in southern Chile and, with it, the systematic arrival of European immigrants, an informal discourse has been favored over time to sustain the transcendent contribution of foreigners in the area, as well as the architectures accrued, thus emerging a widely spread valuation and cataloging discourse; the «German architecture of southern Chile.» Notwithstanding the widely publicized colonizing agenda and its overall impact, economic progress and better material conditions are not transversal issues within this migrant colony. Within this scenario, the Typical Zone of General Pedro Lagos Street, located in the city of Valdivia, constitutes a highly representative sector in terms of its social recognition and the valuation given to the properties located there as exponents of a prolific colonization process. In a specific group of buildings in this area, this article will review and present detailed background information that will allow building a situated and complex architectural scene, revealing the mechanisms used to exhibit prosperity and social climbing as an expiatory vehicle to cover production conditions alien to the neatness of capitalist German entrepreneurship and the European sophistication that was so desired to be transmitted in the cities undergoing fledgling immigration processes.

XFEM-Based Study of Fatigue Crack Propagation in Rocket Deflector Troughs under Coupled High-Temperature and Impact Conditions

This research investigated fatigue crack propagation on the lower surface of rocket deflector troughs in offshore rocket launch platforms. Initially, a numerical model of an offshore rocket launch platform was established using ABAQUS based on the Extended Finite Element Method (XFEM). Subsequently, two variable parameters—the initial crack length and initial tilt angle—were introduced. This research systematically analysed the impact of these parameters on the fatigue crack propagation patterns in both the maximum stress and maximum deformation regions of the deflector channels under the combined conditions of high temperature and impact. Finally, the research indicated that the propagation length of surface cracks in the deflector trough exhibited an initial increase followed by a decrease with the rise in the pre-set inclination angle. Notably, the stable propagation rate of the crack in the region of maximum deformation surpassed that observed in the region of maximum stress. Through meticulous comparative analysis, it was evident that temperature loading significantly exacerbated the initiation and propagation of cracks, particularly in the upper region of the deflector channel’s lower surface.

Effects of kinetic energy and firearm-to-target distance on fracture behavior in flat bones.

This research implements a fractographic approach to investigate the relationships between kinetic energy, firearm-to-target distance, and various aspects of fracture behavior in gunshot trauma. Gunshot experiments were performed on pig scapulae (n = 30) using three firearms generating different muzzle (initial) kinetic energies, including a 0.32 pistol (103 J), 0.40 pistol (492 J), and 0.308 rifle (2275 J). Specimens were shot from two distances: 10 cm (n = 15) and 110 cm (n = 15). Features evaluated in fractographic analysis such as cone cracks, radiating cracks, crack branching points, and circumferential cracks could be easily identified and measured in flat bones and allowed for statistical comparison of crack propagation behavior under different impact conditions. Higher-energy bullets produced more radiating cracks, more crack branching points, and longer fracture lengths than lower-energy bullets. Distance had no significant effect on fracture morphology at the distances tested. That quantitative measures of crack propagation varied with energy affirms that kinetic energy transfer is important in determining the nature and extent of fracture in gunshot wounds and suggests it may be possible to infer relatively high- versus relatively low-energy transfer using these features. Ranges obtained with the three firearms exhibited considerable overlap, however, indicating that other variables such as bullet caliber, mass, and construction influence the efficiency of energy transfer from bullet to bone. Therefore, fracture morphology cannot be used to identify a specific firearm or to directly reconstruct the muzzle (initial) kinetic energy in forensic cases.

Experimental and numerical investigations on the microstructural features and mechanical properties of explosively welded aluminum/titanium/steel trimetallic plate

In this paper, 3A21Al/TA1/CCSB composite plate was fabricated successfully by explosive welding to improve the bond strength. The microstructure characteristics of aluminum/titanium and titanium/steel bonding interfaces were systematically investigated by two-step numerical simulation and SEM/EBSD characterizations. Firstly, the SPH (Smoothed Particle Hydrodynamics) and Lagrange methodology were used to simulate and calculate the collision velocity and collision angle, establishing an accurate impact condition. Secondly, the SPH model was used to simulate the high-speed oblique impact welding process. The simulation results reproduce the formation of wavy interface, vortex zone and jet, which are consistent with the experimental results. Combined with SEM, EBSD, and EDS analysis, continuous and uniform wavy structures were found at different interfaces of the composite plate, showing significantly different wave lengths and amplitudes. Dynamic recovery and recrystallization took place at the bonding interfaces which showed refined grain with different preferred orientations. The observed structural characteristics and the thermodynamic state predicted by SPH simulation inferred the evolutions of microstructures (including morphologies, micro defects, grain structures). The tensile strength and fracture elongation of the trimetallic plate reach 448.2 MPa and 14.15%, respectively. In addition, the shear strengths of each interface far exceed the corresponding acceptable standard values.

Assessment of macrozoobenthos baseline diversity for monitoring the ecological quality of Finima Nature Park Lake.

The scarcity of pristine, intact ecosystems limits opportunities to learn about succession and ecosystem evolution under conditions of limited human impact. Finima Nature Park (FNP) has been identified as a possible RAMSAR site. Its protected lake-"FNP Lake" (also known locally as "Bonny Lake")-is an unusual habitat that enables monitoring of aquatic ecological succession in the Niger Delta, where pristine and near-pristine ecosystems are becoming scarce. Macrozoobenthos are one of the best-known bio-monitors of ecological health integrity because they are widespread and long-lasting, with moderate mobility and high diversity, among other valuable characteristics. Monthly data of the community structure of macrozoobenthos and some of the FNP Lake's priority abiotic factors were collected in 2018, which provided a baseline for identifying future water quality changes and succession in the lake. Except for temperature and dissolved oxygen (DO), which were spatially uniform, the physico-chemical parameters varied spatio-temporally. The diversity indices values were low. According to the canonical correspondence abundance (CCA) plot, taxa distributions were influenced mainly by pH, DO, and temperature, which explains the prevalence of oxygen-insensitive species.

Demand management processes to improve access to cognitive-behavioral therapies for anxiety disorders: a grounded theory study.

Anxiety disorders are impactful mental health conditions for which evidence-based treatments are available, notably cognitive-behavioral therapies (CBTs). Even when CBTs are available, demand-side factors limit their access, and actors in a position to perform demand management activities lack a framework to identify context-appropriate actions. We conducted a constructivist grounded theory study in Quebec, Canada, to model demand management targets to improve access to CBTs for anxiety disorders. We recruited key informants with diverse experiences using purposeful, then theoretical sampling. We analyzed data from 18 semi-directed interviews and 20 documents through an iterative coding process centered around constant comparison. The resulting model illustrates how actors can target clinical-administrative processes fulfilling the demand management functions of detection, evaluation, preparation, and referral to help patients progress on the path of access to CBTs. Modeling clinical-administrative processes is a promising approach to facilitate leveraging the competency of actors involved in demand management at the local level to benefit public mental health.

Probing the small-scale impact deformation mechanism in an aluminum single-crystal

Although the rate-dependence of metals has been widely researched, the deformation mechanism under small-scale impact conditions lacked exploration and in-depth understanding. Using quasi-static nanoindentation (strain rate, SR, < 1 s–1) and high strain-rate nano-impact (SR > 103 s–1) with a pyramidal Berkovich tip, this study investigates the influence of SR on the deformation response of an aluminium single crystal (110). The underlying microstructural variance was analyzed using on-axis TKD and TEM. The results show that the impact deformation involves great elastic recovery and different substructural characteristics. In contrast to the uniform sub-grain substructure with medium and high-angle grain boundaries formed during quasi-static indentation, the substructure formed under impact has a more heterogeneous nature including microbands near the surface and sub-grains underneath with dominant low-angle grain boundaries. The significant change in substructure for the impact deformation comes from suppressed thermally activated dislocation motion, leading to the conversion of dislocation glide from wave-like (quasi-static) to planar regime (impacting), and the insufficient rearrangement of geometrically necessary dislocations (GNDs). The heterogeneous microstructure develops due to the competition between high strain-rate-induced planar-slip and strain gradient-induced GND rearrangement, as well as the uneven distribution of SR and strain gradient. Moreover, the underlying incipient mechanism of the microband is proposed, in which successive primary dislocations are nucleated at the surface and glide perpendicular to flanks to pile up. Finally, the influence of SR on indentation size effects is discussed.

Mechanical safety prediction of a battery-pack system under low speed frontal impact via machine learning

In response to nonrenewable energy consumption and environmental pollution, the development of electric vehicles has accelerated. The safety of electric vehicles has garnered considerable attention. There are numerous incalculable foreign objects on the road that may collide with or scratch the battery-pack’s frontal, resulting in battery-pack system damage or even explosion. This poses a significant risk to the safety of passengers and drivers. In this paper, a diversity of mechanical safety prediction models for battery-pack systems are proposed. These models support data-driven structural optimization of the battery-pack system by utilizing the numerical results of the bottom shell deformation. These simulation-based prediction models combine response surface method and machine learning algorithms. First, a nonlinear finite element model of the battery-pack system is established. The efficacy of the model is verified using constrained modal analysis in a variety of commercial software packages. Second, the collision simulations are executed and the data in various collision conditions are collected. Different sample sizes are used to develop various response surface models and machine learning models. The machine learning algorithms adopt support vector machine, Gaussian process regression, and neural network models. Third, the prediction accuracy of multiple prediction models is investigated according to error functions. The results show that the neural network model can predict the most accurate deformation under the condition of low speed frontal impact. The prediction average absolute percentage error of the neural network model is only 0.34% within the design domain, and only 2.54% outside the design domain. The proposed prediction model can be used for reliable design of the battery-pack system in electric vehicles. It also can be employed to design the early warning system of the battery-packs.

Impact Force Algorithm and Parameters of Rolling Stone Impact Pier in Mountain Area

In mountainous bridge engineering, the impact of falling rocks on bridge piers is a critical issue. Although various algorithms have been used to calculate impact forces, there is limited research on the impact force algorithm for rolling stones hitting bridge piers. This study, based on the impulse–momentum theorem and the impact force algorithm proposed by professor Ye Siqiao, derived an impact force algorithm for rolling stones hitting bridge piers at different impact velocities and angles. Additionally, an indoor scaled‐down test was designed to analyze the effects of impact velocity, angle, and position on impact force, and the results were compared with domestic and international algorithms and the calculated values of the formula derived in this paper. The results show that at an impact velocity of 3.45 m/s and an impact angle of 30°, the peak impact force reached 16.37 kN, which is a 22% increase from 12.85 kN at 2.83 m/s and a significant 53.9% increase from 10.56 kN at 2.29 m/s. Furthermore, the impact force decreased by 13.8% and 21.73% as the impact angle increased from 30° to 45° and 60°, respectively. These findings underscore the significant influence of impact velocity and angle on impact force, highlighting the necessity for accurate algorithms in engineering applications. The formula derived in this paper yielded results closest to the peak impact force, with errors between the results under each impact condition and the peak impact force fluctuating within an engineering acceptable range of ~10%, indicating that the formula derived in this paper is more accurate and reasonable for engineering applications.

Study of fractography of ferritic ductile iron at different temperatures and loading conditions

This study characterizes the fractography of ferritic ductile iron under various loads, including tensile, fatigue and bending, and impact conditions. The results indicate that ductile fracture is the primary mechanism observed during tensile testing at room temperature. The fractography resulting from fatigue testing exhibits characteristics similar to cleavage fracture, and explains the formation of fatigue striations caused by the joint effects of dislocation slip and oxidation under crack tip stress. Under impact testing, the main fracture mechanism transitions from ductile to brittle with decreasing temperature. At high temperatures, fractography is mainly characterized by elliptical dimples with graphite nodules at the center that deform along the stress direction. In the ductile-brittle transition temperature range, a mixed fracture mechanism involving both dimples and cleavage patterns is observed. At low temperatures, the fracture mechanism is cleavage fracture, cleavage fracture is mainly caused by the deformation twin, inducing crack nucleation. These findings further validate D.O.Frenandino’s quantitative analysis method for determining the main crack propagation direction of ductile fracture and brittle fracture. By employing larger statistical datasets, it is shown that this method yields high accuracy in determining the main crack propagation direction of ferritic ductile iron, thereby promoting its application as a general method for impact fractography analysis.

Experimental study on the impact resistance of bamboo scrimber beams under impact loading

Drop-weight impact tests were conducted on bamboo scrimber beams to assess their resistance to dynamic stress. The study focused on investigating the influence of impact orientation, velocity, and cross-section size on failure modes and mechanical behavior. A comparison of data between dynamic impact and static load conditions consistently showed failure via cracking at the bottom of the beam. The severity of damage increased with impact velocity. Beams with greater stiffness exhibited less deformation, increased peak force, and reduced deflection. The energy absorption increased nonlinearly with impact speed, eventually stabilizing at higher velocities. Additionally, it was observed that increased stiffness led to a slight reduction in energy dissipation. The study also demonstrated the presence of inertia effects in bamboo beams during impact and proposed a design approach for enhancing impact resilience. Furthermore, a predictive model was developed to estimate the maximum deflection under dynamic conditions.

INFLUENCE OF BUBBLE GROWTH AND LIQUID FILM INSTABILITIES ON DROPLET IMPACT PHENOMENA UNDER SATURATED BOILING REGIMES

Evaporation and boiling are processes that occur in many industrial applications involving multiphase flows. For liquid films, however, studies are scarce regarding heat and mass transfer mechanisms and require further research. The main objective of this work is to evaluate bubble formation and detachment, followed by the impact phenomena. Therefore, an experimental setup was built and adapted for this purpose. A borosilicate glass impact surface is placed over a heat source, which consists of an aluminum block with four embedded cartridge heaters that heat the liquid film by conduction. Water and n-heptane are the fluids adopted for the experimental study, as the differences in thermophysical properties allow for a wider range of experiments. Study cases include dimensionless temperatures of &amp;theta; &amp;#62; 0.6 for similar impact conditions. In terms of bubble formation, n-heptane displays smaller bubble diameters and higher release rates, whereas water exhibits larger bubbles and lower rates. Qualitatively, liquid film temperatures close to the saturation temperature do not reveal a direct influence on the crown development and posterior secondary atomization. For later stages of the impact, the central jet height and breakup are influenced by the film temperature, which is associated with the variation of thermophysical properties.

Numerical analysis of an experimental ballistic test of Al/SiC functionally graded materials

Metal/ceramic functionally graded materials (FGMs) have been increasingly used for impact-resistant applications because of their ability to combine the strength of both components. However, understanding the local response of FGMs under ballistic impact conditions remains a complex nonlinear problem. Moreover, performing experimental investigations is difficult due to technical limitations in measuring critical parameters such as stress, strain, and pressure. That is why research in this field also concentrates on modeling methodologies, such as numerical simulations. In this study, a finite element model (FEM) was implemented to investigate the behavior of a particular metal/ceramic-based FGM impacted with fragment-simulating projectiles (FSPs). The studied FGMs, exhibiting an elastoplastic behavior, were composed of aluminum (Al) and silicon carbide (SiC). The ceramic volume fraction (Vc) varies according to a power-law distribution, through the thickness. Their effective material properties were evaluated using a homogeneization-based self-consistent method. FGM’s dynamic behavior was described using the dynamic Tamura-Tomota-Ozawa model (DTTO). The numerical simulations were in good correlation with experimental results. The importance of the DTTO model's introduction and the calibration of the plastic strain criterion in the failure modeling of FGMs were highlighted. In addition, it was observed that the variation in the composition exponent and grading continuity of mechanical properties has a significant effect on the predicted ballistic limit. It was finally noted that a linearly-composed 5-layerbased specimen exhibited a higher level of ballistic resistance.

Impact Velocity-Dependent Patterns and Mechanisms of Spalling Behavior in Single Crystal Nickel

To reveal the impact velocity (U&lt;sub&gt;p&lt;/sub&gt;) effect on the spalling and fracture behavior of single crystal nickel, a non-equilibrium molecular dynamics approach is performed to investigate the free surface velocity curve, radial distribution function, atomic crystal structures, dislocations, and void evolution process. The results show that the critical U&lt;sub&gt;p&lt;/sub&gt; for spalling behavior in single crystal nickel is 1.5 km/s, the spallation mechanism is classical spallation damage (U&lt;sub&gt;p&lt;/sub&gt;≤1.5 km/s) and micro-spallation damage (U&lt;sub&gt;p&lt;/sub&gt;＞1.5 km/s). The number and distribution area, and stress distribution area under micro-spallation damage much higher than those under classical spallation damage. Analyzed the influence of impact velocity on the classical spalling damage behavior (U&lt;sub&gt;p&lt;/sub&gt; ≤ 1.5 km/s) and obtained the corresponding spalling strength, an accident of spalling strength occurs at the U&lt;sub&gt;p&lt;/sub&gt; of 1.3 km/s. The spalling strength of single crystal nickel is influenced by the combined effects of stacking faults, phase transformation, and dislocation mechanisms. The nucleation and emission of dislocations increase lead to a decrease in the spalling strength. When U&lt;sub&gt;p&lt;/sub&gt; &lt;1.3 km/s, spalling damage is primarily influenced by stacking faults. When U&lt;sub&gt;p&lt;/sub&gt; =1.3 km/s, spalling strength is mainly affected by the competition between stacking faults and phase transformation. When U&lt;sub&gt;p&lt;/sub&gt; &gt;1.3 km/s, spalling strength is predominantly influenced by the body-centered cubic (BCC) phase transformation mechanism (transformation path: FCC → BCT → BCC). This study reveals the impact velocitydependent patterns, mechanisms, and effects on spalling damage and fracture, providing a theoretical basis for the protective application of nickel-based materials under extreme impact conditions.

Exploiting droplet impact-driven flows and jetting to guide and extract particles from particle-laden droplets

The low concentration of target particles in liquids necessitates their enrichment to a measurable level to provide precise and accurate analytical results. However, the enrichment and extraction of the adsorbed target particles from the droplets remains a challenge. The existing stimuli-responsive strategies for particle enrichment and extraction are not always desirable, as they depend on various parameters, including charge, dielectric constant, magnetic state, size of the particles, etc., which limits their applicability. An ideal method should be capable of extracting particles from the target droplet, irrespective of particle properties, and the process should be fast, preferably in an additive and electrode-free environment. This article presents an efficient strategy for realizing particle extraction based on droplet impact-driven fluid flows under isothermal, non-evaporative, and additive/electrode-free environments. The process relies on the droplet impact-driven redistribution of the particles at the liquid–air interface and the generation of a particle-rich satellite droplet at a designed Weber number, We ∼ 65. The impact dynamics and flow profiles are investigated using simulation and high-speed imaging, and the droplet impact-driven particle extraction is demonstrated experimentally. The particle extraction efficiency is estimated by weight percentage and optical profilometry analysis, and at optimal impact conditions, an extraction efficiency of about 90% is achieved, which takes only a few milliseconds to complete. The role of particle size, surface tension, and We on the extraction efficiency is investigated experimentally. Since the developed method is based on flows, it could be a potential candidate for the extraction/enrichment of various particles/biological entities and does not require complicated setups/skills.

Performance evaluation of the eight-one six-point occupant restraint system based on experiments

In order to further ensure occupant safety, a new type of motor vehicle occupant restraint system is proposed in the paper. According to its structural characteristics, the shoulder belts are shaped like the Chinese number eight (八), the lap belt is shaped like the Chinese number one (一), and it has six fixed points; hence, it is called the “Eight-one six-point occupant restraint system.” The effectiveness of the “Eight-one six-point occupant restraint system” for adult and child occupant protection was verified under frontal impact conditions (50 km/h) and lateral impact conditions (30 km/h) using the Hybrid III 50th percentile dummy and the Q3 child dummy, respectively. Meanwhile, a comparison was made with the safety performance of the typical occupant system. The conclusion indicates that wearing a typical occupant restraint system carries the risk of occupant detachment from the restraint, neck strangulation, and collision interference between occupants on the far side and on the collision side; it also cannot be applied for child occupant protection. However, the “Eight-one six-point occupant restraint” can effectively restrain adult and child occupants within safety areas with a simple and easy-to-wear structure and technological innovation, which has certain application value.

Study of Release of Biologically Active Compounds from Cord Blood Under Different Conditions of Low-Temperature Impact

Here, we have studied the impact of cord blood destruction method on composition of the cord blood-derived low molecular fractions, and compared the cryodestruction with other methods of cell destruction before extracting. Human cord blood was destroyed by rapid or slow freezing / warming, hypotonic lysis and thermal destruction. The obtained substance was used to produce the cord blood fraction (CBF) by multi-stage ultrafiltration and lyophilization. Dry weight, CBF composition and total protein content in them were evaluated by chromatographic profiles (gel permeation and reverse-phase high-performance liquid chromatography). The CBFs, obtained by diff erent techniques for cord blood destruction were established to diff er in the content and molecular weights of the components. These fi ndings suggest the possibility to vary the amount and range of low molecular weight compounds in lyophilized cord blood fractions by using low temperatures and combining diff erent regimens of freezing / warming. Key words: cryodestruction, cord blood, biologically active substances, low-molecular fraction, low temperatures