Impact Speed Research Articles

Effect of seawater aging on the erosive wear response of aramid fiber reinforced composites

This study presents the effect caused by the saline environment (artificial seawater) on the physical and tribological properties of laminated composite materials reinforced with aramid fibers when they are subjected to erosive wear by sand particles. Composite materials made by epoxy resin and reinforced with glass fiber, carbon fiber and hybrid fiber (aramid with carbon) were studied. The laminates were superficially reinforced with layers of Kevlar fiber and prepared by the vacuum-assisted resin infusion process. The samples were subjected to a seawater accelerated aging process at 70°C for 1122 h. To reproduce erosive wear conditions of marine structural components, sea sand was used as solid particle under conditions of 4.5 bar of pressure, impact speed of 4.7 m/s and impact angle of 90°. The results showed that aged materials absorb more impact energy with respect to unaged counterparts, causing less material loss and a less depth in the wear track. The information generated by this research work may serve for the design and durability analysis of marine structures such as tidal turbine blades.

Early, Rapid or Global? Internationalization Speed and SME’s Performance

The article investigates the impact of three dimensions of the speed of internationalization speed – the entry timing, the initial speed and the pace of international expansion – on the performance of exporting small‐ and medium‐sized enterprises (SMEs). To this purpose, we adopt a mixed-method approach analysing quantitative and qualitative data on Italian-exporting SMEs. The results show that entry timing, which is not relevant per se, moderates the positive impact of the initial speed on SME’s performance. Furthermore, a higher pace of international expansion is negatively related to the performance of SMEs. Building on the early internationalization literature, the study contributes to the existing literature on performance outcomes of the speed of internationalization of SMEs. The study has managerial implications for managers and entrepreneurs who are planning to internationalize.

Modelling and cycle‐by‐cycle control of an electromechanical engine valve actuator with impact speed limiter based on hydraulic damper

AbstractVariable valve actuation (VVA) systems based on electromechanical valve actuators (EMVAs) enable a flexible operation and management of internal combustion engines that results in a reduction of pollutant emission and fuel consumption while improving engine power and efficiency. However, to achieve the benefits promised by EMVAs, it is of utmost importance to guarantee the catch of the valve by the system magnets with an acceptable impact speed of the valve at the end‐strokes. Valve catching failures can severely damage engine valves while high impact speeds induce mechanical wear and unacceptable noise. The soft landing control of the valve at the end‐strokes is challenging because of system nonlinearities, parameter uncertainties, and external disturbances. The complexity of the control design increases further when industrial cost‐effective solutions are sought. This paper presents a novel solution for reducing the impact speed of the valve without the use of costly position valve sensors. The proposed solution leverages on a small hydraulic damper (HD) embedded into the EMVA and a feedback cycle‐by‐cycle controller. The passive element reduces the impact speed while the controller adjusts at every engine cycle the EMVA coil currents based on pressure peaks detected in the HD to guarantee valve catching while steering the impact speed toward its minimum. The design of the controller exploits a physics‐based model that maps the pressure peak in the HD onto the impact speed and a gradient descent algorithm is adopted searching the minimum. The closed‐loop permanence is assessed in simulation by using an experimentally validated EMVA model and considering detailed dynamics of the HD. Numerical results show the ability of the proposed control architecture to reduce the impact speed and its robustness to parameters variations (oil temperature) and external disturbances (gas pressure forces).

Experimental and numerical study on the dynamic behavior of prestressed concrete panels suffering low speed impact

Bidirectional bonded prestressed concrete (PS) structures have widely been used in energy infrastructure. Nonetheless, there has been a lack of research on the effect of the reinforcement ratio of longitudinal bars on the dynamic behavior of PS structures. Therefore, the low speed drop hammer impact tests of 4 reinforced concrete (RC) and 9 PS panels have been completed in this paper, firstly. The dynamic behavior of PS panels has been investigated through work, and the working mechanism of the reinforcement ratio on the dynamic behavior of the specimens is analyzed. The results show that the panels mainly suffer plastic deformation and damage; increasing the reinforcement ratio could improve the membrane force effect and enhance the confinement effect on concrete to improve the load-bearing capability of the specimen. However, it will expand the plastic damage area of the specimen. Furthermore, the numerical models have been verified based on the test results to deeply analyze the influence of reinforcement ratio on the energy dissipation mechanism of the specimen. It shows that the increase of the reinforcement ratio of reinforcement will increase the energy dissipation proportion of reinforcement, but it will also increase the plastic energy consumption ratio of the concrete and increase the prestress loss after the impact; while, the rise of the reinforcement ratio of prestressing bars is beneficial to use the reinforcement, prestressing bars and tensile bars fully. Therefore, the designer could increase the reinforcement ratio of prestressing bars to enhance the impact resistance of the structures.

Characterization of the mechanical energy absorption of honeycomb core sandwich panels filled with shear thickening fluid under low speed impact

Characterization of the mechanical energy absorption of honeycomb core sandwich panels filled with shear thickening fluid under low speed impact

Tram-Pedestrian Collision Modeling Using Experimental Data—Its Validation, Repeatability, and Challenges: A Pilot Study

To satisfy the needs of growing urban populations, mitigate the impacts of climate change, and improve the environmental conditions and quality of life in cities, there has been an increasing demand for public transport, especially effective and economically beneficial trams. As a consequence, the issue of pedestrians’ safety has become more important because of a higher risk of tram-pedestrian collisions. The article is focused on the development of a computational model that can accurately simulate such collisions, and its challenges and limitations. Experiments were conducted using various types of trams, different impact speeds, and an anthropomorphic test device (dummy). Computational models of the tram front ends were created based on CAD geometry supplied by VÚKV a.s. The finite-element mesh itself used a combination of 1D, 2D, and 3D elements. Depending on the shape of the individual components, TRIA, QUAD, HEX, PENTA, and TETRA elements were used for modeling. The results showed that the consequences of these collisions are sensitive to small differences in the posture of the dummies. Therefore, it is difficult to identify a generally more pedestrian-friendly shape for trams using the dummy-tram crash test method.

Effect of DH-shaped coil symmetry coefficient on EMPW process

ABSTRACT The coil is used for electrical connection and energy conversion in the electromagnetic pulse welding (EMPW) process, so its structure affects the welding effect. In this work, for the dual H-shaped (DH) coil, the influence of the symmetry coefficient on the Cu-Al sheets EMPW was studied through the simulation and experiment. When the voltage was 7 kV and the symmetry coefficient g was 0.75, 1, and 1.33, the V c-β trajectory curve contained by the simulation combined with the welding window curve (WWC) to analyze the dynamic process and welding effect. The relative impact speed was the fastest and the corresponding weld seam length was the longest when g was 1.33. The welding experiment results were consisted with the simulation results, it was beneficial to weld the Cu-Al sheets when g was 133. The symmetry coefficient could change the impact speed and angle to affect the welding effect. This work is of great significance for DH coil design.

What should I use to calculate vehicle EES?

Comprehensive crash analysis includes calculating impact speed, which requires the determination of kinetic energy expended on the deformation of the vehicle's structural elements at the point of contact during a collision. The accuracy of the input data affects the resulting analysis of the crash. Therefore, this article aims to analyse selected factors influencing the determination of Energy Equivalent Speed (EES) determination using the CRASH3 algorithm: the extent of damage using defined measurement points, deformation width, and also limit speed b0. The variables were varied depending on selected factors such as the extent of damage, the type of collision (overlap), and also vehicle type (vehicle category classification). The presented study concluded that using 2 equally spaced measurement points to define the deformation profile should not be recommended in forensic practice when using CRASH3 algorithm. Using 7 measurement points seems more appropriate in case of equal spacing, even though the differences in calculated EES are not high when using 5 or 6 measurement points, especially with respect to the inaccuracy/technically acceptable tolerance of the EES value determination. The resulting EES is significantly influenced by variation of the deformation width. The used b0 range had a significant effect on the resulting EES value only in the case of SUVs. These vehicles show higher stiffness, which supposes the use of lower b0 values should not be recommended.

Do It Right the First Time? Exploring the First Cross-border Acquisition and Expansion Frequency of Emerging Market Multinationals

AbstractDo it right the first time! But, how? Current dialogue on the expansion of emerging market multinational enterprises (EMNEs) is pervasive. Nonetheless, it ought to have examined strategic attributes and the speed of implementing different strategies for their first venture. Drawing on the springboard perspective, this study tests the impact of EMNEs' first cross-border acquisition (CBA) strategy and speed on their consequential expansion frequency and performance. We also examine the boundary conditions of comparative nationalism between countries, in view of the resurgence of nationalism in an era of deglobalization. Findings reveal that EMNEs' rapid adoption of a focused strategy for their first CBA increases their expansion frequency, while the adoption of a conglomerate strategy decreases it. These relationships are affected in reverse by high comparative nationalism, and the performance consequences of expansion vary with firms using different strategies for their first attempt. This study enriches the EMNE literature and highlights the role of national ideologies in international business research.

Negative symptoms and social cognition as mediators of the relationship between neurocognition and functional outcome in schizophrenia.

In this study we assessed the contribution of psychopathology, including the two domains of negative symptoms (motivational deficit and expressive deficit), processing speed as an index of neurocognition, and emotion recognition, as an index of social cognition, to poor functional outcomes in people with schizophrenia. The Positive and Negative Syndrome Scale was used to evaluate positive symptoms and disorganization and the Brief Negative Symptom Scale to assess negative symptoms. The Symbol Coding and the Trail Making Test A and B were used to rate processing speed and the Facial Emotion Identification Test to assess emotion recognition. Functional outcome was assessed with the Personal and Social Performance Scale (PSP). Regression analyses were performed to identify predictors of functional outcome. Mediation analyses was used to investigate whether social cognition and negative symptom domains fully or partially mediated the impact of processing speed on functional outcome. One hundred and fifty subjects from 8 different European centers were recruited. Our data showed that the expressive deficit predicted global functioning and together with motivational deficit fully mediated the effects of neurocognition on it. Motivational deficit was a predictor of personal and social functioning and fully mediated neurocognitive impairment effects on the same outcome. Both motivational deficit and neurocognitive impairment predicted socially useful activities, and the emotion recognition domain of social cognition partially mediated the impact of neurocognitive deficits on this outcome. Our results indicate that pathways to functional outcomes are specific for different domains of real-life functioning and that negative symptoms and social cognition mediate the impact of neurocognitive deficits on different domains of functioning. Our results suggest that both negative symptoms and social cognition should be targeted by psychosocial interventions to enhance the functional impact of neurocognitive remediation.

The impact of nozzle diameter and printing speed on geopolymer-based 3D-Printed concrete structures: Numerical modeling and experimental validation

3D Concrete Printing (3DCP) is a promising technology with significant advantages for the construction industry, encompassing reduced labor costs, diminished carbon dioxide emissions, enhanced time efficiency, improved user convenience, and design flexibility. To ensure optimal structural outcomes and resource efficiency, integrating numerical modeling and simulation is imperative for predicting structural behavior and identifying potential premature failures in 3DCP. Despite the recognized importance of this integration, the impact of different printing parameters on numerical models, particularly with variations in printing speed and printing layer, remains an unexplored area. This research delves into the influence of crucial printing parameters, specifically printing speed and nozzle diameter, on the buildability of 3D-printed structures within the built environment. A comprehensive experimental analysis is conducted on geopolymer-based 3D-printed structures, encompassing diverse process parameters associated with 3D printing (3DP) technology. A numerical model is deployed to predict the buildability of these structures, and its results are compared with experimental findings, assessing the efficacy of numerical modeling under varying printing parameter conditions. Rigorous characterization of input material properties is undertaken to ensure the accuracy of numerical simulations. Experimental results showcase favorable processability and buildability of geopolymer materials derived from novel Construction and Demolition Waste (CDW). Findings indicate that an increased nozzle size, reflected in greater layer height and width, positively influences buildability, whereas higher printing speeds correlate with reduced buildability. The numerical model successfully captures these buildability trends, though with an error ranging from 32 % to 45 % in predicting failure in 3D-printed structures. Nevertheless, the overall performance of the numerical model remains reliable in predicting the influence of printing parameters on buildability.

Research on the Impact of Air Temperature and Wind Speed on Ventilation in University Dormitories under Different Wind Directions (Northeast China)

This study employs computational fluid dynamics to analyze the natural ventilation conditions of university student dormitories in the northeastern region of China under various outdoor wind directions, wind speeds, and temperature conditions. By separately simulating room natural ventilation efficiency under four different outdoor wind speeds (1.5 m/s, 3.3 m/s, 5.4 m/s and 7.9 m/s) at different outdoor temperatures (−10 °C, 0 °C, 10 °C and 20 ℃), curves of indoor pollutant removal rates (VOA-Time) are established for different wind directions. The study also determines the minimum ventilation time required for rooms under different environmental conditions (TVOA=70%). The data indicate that, despite the promotion of ventilation efficiency with increasing wind speed or indoor-outdoor temperature difference, the wind direction determines the extent to which these factors enhance room ventilation efficiency. Furthermore, there are corresponding mathematical relationships between TVOA=70%, outdoor temperature, wind speed, and different wind directions, allowing for predictions related to the rate of indoor carbon dioxide change. The research findings will assist students in formulating more effective ventilation strategies under complex outdoor environmental conditions.

Study on dynamic response of cushion layer-reinforced concrete slab under rockfall impact based on smoothed particle hydrodynamics and finite-element method coupling

Abstract In the rockfall prevention and control project, the reinforced concrete (RC) slab and sand (gravel soil) soil cushion layer are commonly used to form the protection structure, thereby resisting the rockfall impact. Considering that the oversized deformation of the cushion layer under impact load using the finite element simulation cannot converge, this article establishes a numerical calculation model using smoothed particle hydrodynamics–finite-element method coupling (SPH–FEM). First, the standard Lagrange finite-element mesh is established for the whole model using ABAQUS, and then the finite-element mesh of the soil cushion layer is converted to SPH particle at the initial moment of the calculation, and finally the calculation results are solved and outputted. The results indicate that, compared with the results of the outdoor rockfall impact test, the relative errors of the rockfall impact force and the displacement of the RC slab are within 10%, which proves the rationality of the coupling algorithm; moreover, in terms of the numerical simulation, the SPH–FEM coupling algorithm is more practical than the finite element for reproducing the mobility of the rockfall impacting the sand and soil particles. In addition, at an impact speed of less than 12 m·s−1, the cushion layer is able to absorb more than 85% of the impact energy, which effectively ensures that the RC slab is in an elastic working state under small impact energy and does not undergo destructive damage under large impact energy; the peak impact force of the rockfall is approximately linear with the velocity, and the simulated value of the peak impact force is basically the same as that of the theoretical value of Hertz theory; the numerical simulation is good for reproducing the damage process of the RC slab in accordance with the actual situation. The SPH–FEM coupling algorithm is more justified than the FEM in simulating the large deformation problem, and it can provide a new calculation method for the design and calculation of the rockfall protection structure.

Simulation of pedestrian interaction with autonomous vehicles via social force model

Simulation of pedestrian motion in urban traffic networks is crucial for designing autonomous vehicle systems. In a mixed traffic system, a complex interaction occurs between a pedestrian and a vehicle. To understand this interaction pattern and evaluate traffic safety analysis, a simulation tool can be useful. It can help autonomous vehicle designers to visualize pedestrian and vehicle trajectory, extract velocity and acceleration profile of both agents, test different autonomous vehicle planning algorithms, and assess the traffic safety in severe traffic conflicts. This paper presents a rule-based social force model to simulate pedestrian trajectories during interaction with an autonomous vehicle. The social force model is then integrated with an autonomous vehicle control and planning algorithm for simulating the behavior of both pedestrian and vehicle in traffic conflicts by varying different parameters such as agent's initial speed, different vehicle sensor types (error percentage of pedestrian detection varies), different pedestrian types (risk-taking, cautious, and distracted), etc. This simulation tool provides minimum distance accepted by a pedestrian during a road crossing scenario as output. Additionally, the simulation illustrates the impact of vehicle initial speed on crossing decision and minimum distance accepted by pedestrians before crossing. The simulation tool can be useful to simulate risky interaction scenarios to understand the effectiveness of autonomous vehicle planning algorithm while interacting with different types of pedestrians.

A study on the cyclist lower extremity injury risk by using German in-depth accident data

The lower extremities of cyclists are the most vulnerable body parts in vehicle-bicycle traffic accidents. However, few studies have been conducted on the effects of vehicle front-end profile parameters on cyclist lower extremity injuries by using real accident data. This paper aimed to explore the correlation between the cyclist’s severe lower extremity injury (AIS2+) risk and impact speed, vehicle front-end profile variables, and cyclist parameters via using real cyclist accidents. A subsample of 390 cyclist accident cases with lower extremity injuries was selected from the German In-Depth Accident Study (GIDAS) to conduct statistical analysis. Furthermore, an independent samples t-test was performed to analyse the associations between the selected predictive parameters and the risk of cyclists with AIS2+ lower extremity injuries. Finally, the risk function for cyclists with AIS2+ lower extremity injuries was developed by using the logistic regression method. The research results indicated that vehicle impact speed, lower bumper height (LBH), bumper depth (BD), cyclist age, and weight were statistically significant factors for cyclists with AIS2+ lower extremity injuries. The higher vehicle speed, higher LBH and BD corresponded to a greater likelihood of the cyclist suffering an AIS2+ lower extremity injury. These findings contribute to developing more effective safety measures for vehicle front designs and establishing regulations to protect the lower extremities of cyclists.

Hypervelocity impact induced light flash experiments on single and dual layer Kapton targets to develop a time of flight space dust and debris detector

The impact flash from hypervelocity impact on thin (12.5 µm) Kapton film was observed. The projectile sizes ranged from 0.1 to 1 mm, with speeds from 2 to 5 km s−1 and penetrated the Kapton intact, leaving holes the same size as the projectile (to within measurement errors). The flash intensity (normalised to impactor mass) scaled with impact speed to the power 5.5. However, the data also suggest that at constant speed the intensity scales with the area of the hole in the Kapton and not the projectile mass (i.e. with some property of the target and not as a function of the projectile energy or momentum). Using two layers of Kapton, it was possible to construct a Time of Flight (TOF) system, which used the time of the onset of the flash in each layer to produce flight speeds accurate to within typically 1%. When compared to the projectile speed pre-impact, there was no indication of projectile deceleration during passage through the Kapton film. In addition, when PVDF acoustic sensors were placed on the Kapton film, they exhibited an electromagnetic “pick-up” signal from the impact of projectile on the Kapton, confirming suspicions of signal interference from past work with acoustic sensors. The ability of the light flash to provide accurate impact timing signals suggests the TOF system would be suitable for use as a cosmic dust or debris impact detector in space (e.g. Low Earth Orbit).

Microstructure, mechanical, electrical and wear properties of friction stir back extruded copper-6 vol.%Ti2SnC composite material

ABSTRACT This study investigates the impact of extrusion speed on the microstructure, mechanical and electrical properties, and wear resistance of friction stir back extruded Cu-6 vol.% Ti2SnC composite. The findings reveal that severe plastic deformation and heat generated during friction stir back extrusion (FSBE) of Copper-6 vol.% Ti2SnC composite prevented the formation of inter metallics at the particle-matrix interface and resulted in improved bonding. Increasing the speed from 45 to 85 mm/min reduced the maximum plastic strain from 65 to 48 and increased the strain gradient from the surface to the centre of the wire sample. The average grain size decreased from 7.6 ± 0.3 to 3.6 ± 0.2 µm and the average hardness increased from 121.59 ± 8.87 to 130.06 ± 9.95 HV. The yield strength, ultimate tensile strength and elongation decreased by 5.6%, 24% and 12.7% respectively. Wires obtained at the reduced speed of 45 mm/min exhibited an increase of 13% and 26% in electrical conductivity and wear resistance respectively relative to those of the copper matrix material. Analysis of results in the light of a few models indicate that they are in conformity with the results of some of them.

Performance Research on Heating Performance of Battery Thermal Management Coupled with the Vapor Injection Heat Pump Air Conditioning

Compared to the use of positive temperature coefficient (PTC) materials that consume electrical energy for low-temperature heating, heat pump air conditioners can provide more energy-efficient heating performance by absorbing and utilizing heat from the outdoor air to heat the cab in order to improve the range of electric vehicles. In addition, in order to make the battery work under safe working conditions, this paper proposes battery thermal management coupled with vapor injection heat pump air conditioning. The system is modeled and analyzed through simulation, and the impact of the compressor speed and ambient temperature changes in the battery cooling performance of the system. The results show that under different compressor RPM (Revolution Per Minute) with an ambient temperature of 5 °C, the average temperature of the battery pack remains below 30 °C, and the majority of individual cell temperatures are maintained within the range of 20 to 35 °C. At a constant compressor RPM of 4000/min under varying ambient temperatures, the average temperature of the battery pack remains below 30 °C, with the majority of individual cell temperatures staying within the range of 20 to 35 °C. And the battery cooling performance still performs well. In the low temperature of −10 °C and −20 °C, the system can still maintain a relatively stable heating capacity compared with the 2009.1W, provided by the environment temperature of 5 °C at the same RPM.

Experimental and simulation investigation of the impact of rotational speed on the performance of radial-flow gas wave ejector

The gas wave ejector (GWE) is a device that enables energy transfer between gases at different pressures through pressure waves. We conduct an experimental and simulation study on a novel radial-flow GWE, named DUT-R1, designed to harness centrifugal force to enhance mass and energy transfer efficiencies. Considering the significant influence of rotational speed (n) on the pressure waves and flow losses, we examine the relationship between the n of the DUT-R1 and both its ejection rate (ξ) and total efficiency (ηT).Experimental data demonstrate that the GWE can attain the highest ξ and ηT at an optimal designed rotational velocity (nd) when the pressure ports remain fixed. Simulations suggest that the primary cause can be attributed to the disruption of the ideal wave system. And when the equipment is equipped with ports matched to the nd, a consistent increase ξ is observed as the nd increases from 2000 r/min to 4000 r/min, resulting in a maximum improvement of 13.25 %. The simulation results demonstrate that increasing n enhances the suction capacity of the equipment through the inputting of shaft power (P). However, ηT initially increases and then decreases as the nd increases, with a maximum improvement of 11.86 %. The simulation provides an explanation for the observed variations in ηT during the experimental investigation by illustrating that flow losses initially decrease and then subsequently increase with an increasing value of n.

Optimizing Waste Heat Conversion: Integrating Phase-Change Material Heatsinks and Wind Speed Dynamics to Enhance Flexible Thermoelectric Generator Efficiency.

Flexible thermoelectric generators (FTEGs) have garnered significant attention for their potential in harnessing waste heat energy from various sources. To optimize their efficiency, FTEGs require efficient and adaptable heatsinks. In this study, we propose a cost-effective solution by integrating phase-change materials into FTEG heatsinks. We developed and tested three flexible phase-change material thicknesses (4 mm, 7 mm, and 10 mm), focusing on preventing leaks during operation. Additionally, we investigated the impact of wind speed on the output performance of FTEGs with a flexible phase-change material heatsink. The results indicate that the appropriate flexible phase-change material thickness, when integrated with considerations for wind speed, demonstrates remarkable heat-absorbing capabilities at phase-change temperatures. This integration enables substantial temperature differentials across the FTEG modules. Specifically, the FTEG equipped with a 10 mm thick flexible phase-change material heatsink achieved a power density more than four times higher when the wind speed was at 1 m/s compared to no wind speed. This outcome suggests that integrating phase-change material heatsinks with relatively low wind speeds can significantly enhance flexible thermoelectric generator efficiency. Finally, we present a practical application wherein the FTEG, integrated with the flexible phase-change material heatsink, efficiently converts waste heat from a circular hot pipe into electricity, serving as a viable power source for smartphone devices. This work opens exciting possibilities for the future integration of flexible thermoelectric modules with flexible phase-change material heatsinks, offering a promising avenue for converting thermal waste heat into usable electricity.