Search

This paper focuses on the crash response characteristics related to the collapse mechanism and occupant injury during a vertical drop test, which is crucial for evaluating the crashworthiness of fuselage section. A simplified three-frame typical large aircraft fuselage section is designed using the equivalent design methods for weight and moment of inertia, which including two sets of triple seats and four 50th-percentile FAA Hybrid III Anthropomorphic Test Devices (ATDs). A vertical drop test is conducted at a velocity of 6.02 m/s, and the collapse mechanism and occupant injury are analyzed. To evaluate the aircraft's crashworthiness, a comprehensive evaluation is performed considering the survivable volume, retention strength, occupant injury and emergency evacuation, and the Integrated Crashworthiness Index (ICI) is also obtained by a scoring method. It has been proven that the failure position and failure sequence of fuselage structures affect the unrolling failure mode (three plastic hinges failure mode) and the flattening failure mode (multiple plastic hinges failure mode) of fuselage section, providing valuable insights into the crashworthiness design of aircraft fuselage section. [ABSTRACT FROM AUTHOR]

Introduction: Turpentine derivatives and eucalyptus oil are herbal substances traditionally used to treat various skin infections. Limited non-clinical data suggest they exert an immunological activity, but only scant information exists on their antibiotic effects. This in vitro study has been carried out to investigate the antibacterial and antifungal activity of a marketed skin ointment; its active pharmaceutical ingredients larch turpentine, eucalyptus oil, and turpentine oil; and their mixture, against bacteria and yeasts commonly present on the skin and causing skin infections. Methods: The antibiotic activity was tested using the drop dilution assay on the Gram-positive bacteria Staphylococcus aureus (wild type), a methicillin-resistant S. aureus strain, S. epidermidis, S. haemolyticus, Streptococcus pyogenes, the Gram-negative Pseudomonas aeruginosa, and the yeasts Candida albicans and C. tropicalis. Results: The ointment exerts a strong inhibitory effect on all Gram-positive bacteria at a concentration of 5 g/100 mL in the Müller-Hinton medium. It also has inhibiting effect on both Candida species but does not inhibit P. aeruginosa growth. As for the single active pharmaceutical ingredients, larch turpentine was the most active substance. The mixture of the three ingredients, in the concentrations used in the ointment, had a higher antibiotic effect than any of the individual ingredients studied, suggesting at least an additive activity. Conclusions: Our study has shown that the herbal ingredients and their combination exert antimicrobial activities, especially against Gram-positive bacteria, that justify their use in the treatment of skin infections. [ABSTRACT FROM AUTHOR]

Objective: To assess the antibacterial and antifungal activity in vitro of a patented Spirulina extract on sensitive and multidrug-resistant bacteria, yeasts, and filamentous fungi commonly causing skin infections. Methods: The antimicrobial activity was tested using the drop dilution assay on the Gram-positive bacteria Staphylococcus aureus (wildtype), a methicillin resistant S. aureus, S. epidermidis, S. haemolyticus, Streptococcus pyogenes, the Gram-negative multidrug resistant Pseudomonas aeruginosa, the yeasts Candida albicans and C. tropicalis, and the dermatophytes Trichophyton rubrum and Microsporum gypseum. Results: A concentration of 4 g of Spirulina extract per 100 mL of Mueller Hinton agar completely inhibited the growth of all tested bacteria and yeasts, and suppressed dermatophytes growth by 5 log10 units. Conclusion: The Spirulina extract tested could be used as an effective natural, broad-spectrum antimicrobial agent, with potential applications in the therapy of bacterial and fungal infectious diseases. [ABSTRACT FROM AUTHOR]

In the approval process of dangerous goods packagings, drop tests onto a flat, essentially unyielding surface are used to assess resistance against mechanical damage. International adopted regulations like ADR and RID define filling good dependent drop heights and filling degrees whilst the user needs to define the maximum gross mass to be tested and approved. Maximum packaging gross mass is defined conservatively and not reached in practice. To meet the defined gross mass in testing, using additives is permitted. However, in some cases, additives are not desirable due to packaging design or filling substance properties. This leads to deviations from the initial gross mass definition. Hence, a certain drop height adjustment is necessary to achieve the required impact loading. Laboratories frequently adjust drop height assuming a perfectly elastic collision that is inaccurate. Appropriate adjustment is not trivial due to energy conversion processes, for example, plastic deformation. In this work, a test stand is developed for measuring the change in kinetic energy of different packaging designs and filling substances in regulative drop tests. The experimental results are used to validate finite‐element (FE) models so that packaging properties can be varied in simulated drop test scenarios. The findings intend to describe the appropriate drop height adjustment of the respective packaging with same design but deviating gross mass to produce comparable mechanical response. The results are highly beneficial for testing laboratories, approval issuing authorities and packaging institutes confronted with the problem of testing packages with gross masses other than those to be approved. [ABSTRACT FROM AUTHOR]

Apples have been constantly damaged in collecting, transporting, and processing, leading research focus on apples' mechanical‐structural damage behavior. To research apples' mechanical‐structural damage behavior during collision, a dropping collision damage testing device was self‐established, with PLC control, data acquisition‐processing, in situ high‐speed observation. The effect of impact material, drop height, impact orientation on apple deformation and bruise area was investigated with self‐established device, considering three typical kinds of apples. The results indicated that apple dropping collision can be divided into two stages: dropping down contact deformation stage and recovering contact deformation stage. Three kinds of apples demonstrate the largest deformation and bruise area when the impact material is steel and acrylic plate. The deformation is similar when apples collide with soil and foam, apples have no bruise area when the impact material is foam. The correlation between apple deformation, bruising area, and drop height was established, reflecting the relationship between drop height and apples' mechanical‐structural damage behavior. Yellow Marshal apple deformation is the largest compared to other two kinds of apples under the same collision condition. Red Fuji apple bruise area is the largest compared to other two kinds of apples. The largest bruise area of Yellow Marshal apple and Guoguang apple are in apple transverse, and Red Fuji apple is in apple top. The study can provide basic theoretical and practical guidance for apples postharvest work. [ABSTRACT FROM AUTHOR]

To evaluate the energy absorption ability of composite beams with corrugated web under impact, the drop tests were conducted to demonstrate the fracture modes and obtain the load and energy history curves. Based on the drop tests, a finite element (FE) model was proposed with a weak link designed to trigger crushing, developed using Abaqus/Explicit, which integrates cohesive elements and employs the improved Hashin criterion along with the Choi–Chang criterion to accurately predict the onset and progression of delamination. The model accounts for the anisotropy and progressive damage in composite laminates. The periodic boundary conditions (PBCs) were integrated into the single-wave corrugated web beam model, the inherent limitations of which were corrected, enabling it to simulate the crushing process with the same effectiveness as the multi-wave model. As a result, the proposed model can accurately depict the progressive crushing behavior of corrugated web beams under impact loads while maintaining high computational efficiency. [ABSTRACT FROM AUTHOR]

Ignition delay is one of the most important parameters characterising hypergolic propellants. This parameter has a strong impact on thruster operation, especially during the cold start. Ignition delay influences the intensity of pressure rise and its peak values during the start of a thruster. High-pressure levels cause stress inside the chamber wall, which directly affects durability and safety. One of two measurement techniques is usually chosen to determine the ignition delay: visual and pressure-based methods. Visual methods are based on high-speed imaging and subsequent image analysis. In the pressure-based method, the pressure trace is analysed. In this study, both techniques were used together and compared in terms of ignition delay determination of hypergolic propellants igniting during the drop tests. The advantages and disadvantages of both techniques were indicated and described. In the setup used in the study, the visual method was found to be more accurate and reliable. [ABSTRACT FROM AUTHOR]

Injury mechanisms of the lumbar spine under dynamic loading are dependent on spine curvature and anatomical variation. Impact simulation with finite element (FE) models can assist the reconstruction and prediction of injuries. The objective of this study was to determine which level of individualization of a baseline FE lumbar spine model is necessary to replicate experimental responses and fracture locations in a dynamic experiment. Experimental X-rays from 26 dynamic drop tower tests were used to create three configurations of a lumbar spine model (T12 to L5): baseline, with aligned vertebrae (positioned), and with aligned and morphed vertebrae (morphed). Each model was simulated with the corresponding loading and boundary conditions from dynamic lumbar spine experiments. Force, moment, and kinematic responses were compared to the experimental data. Cosine similarity was computed to assess how well simulation responses match the experimental data. The pressure distribution within the vertebrae was used to compare fracture risk and fracture location between the different models. The positioned models replicated the injured spinal level and the fracture patterns quite well, though the morphed models provided slightly more accuracy. However, for impact reconstruction or injury prediction, the authors recommend pure positioning for whole-body models, as the gain in accuracy was relatively small, while the morphing modifications of the model require considerably higher efforts. These results improve the understanding of the application of human body models to investigate lumbar injury mechanisms with FE models. [ABSTRACT FROM AUTHOR]

Background: Polyurethane foams have many uses ranging from comfort fitting seats and shoes to protective inserts in helmets and sports equipment. Current military helmet designs employ foam pads of varying densities and bulk material properties to help absorb energy from impacts ranging from quasi-static to ballistic level strain-rates. Objective: This study aims to analyze the thermomechanical uniaxial compression behavior of a high density liner foam pad and a low density liner foam pad used in the Advanced Combat Helmet. These experiments were conducted under strain-rates of 10 2 s - 1 and under temperature conditions ranging from -20 to 40 °C. This temperature range was chosen to simulate desert and arctic conditions, with a strain-rate regime chosen to represent loads that would occur often throughout the life of the helmet, such as drops, bumps from riding in a vehicle, or heavy collisions from falling. Method: Multiple experimental apparatuses were used in this study, including a Shimadzu TCE-N300 thermostatic chamber (used to create the varying temperature environments) and a custom-built drop-test system (used to induce intermediate strain-rates). Every experiment was paired with two accelerometers and a high speed camera used for Digital Image Correlation (DIC) to analyze sample deformation and resultant acceleration. The foam's mechanical response and energy absorption properties were investigated from the measured stress-strain curves. Additionally, each foam composition was analyzed with X-ray computed micro-tomography (XCT) to investigate microstructure properties pre and post-mortem. Results: Results show that temperature decreased the energy absorption of the low density composition by 48% ± 5% as temperature changed from -20 °C to 40 °C, while energy absorption increased by 53% ± 16% for the high density composition over the same temperature. Conclusion: A comparison between the loading response and the material's density characteristics revealed that the foam's mechanical properties are heavily dependent on strain-rate applications, as well as environmental factors including temperature. Several important characteristics surrounding each foam composition's deformation mechanics and damage tolerance as a result of temperature are discussed. [ABSTRACT FROM AUTHOR]

The investigation of multi-body dynamics (MBD) modeling for landing gear drop tests is a hot topic in the realm of landing gear design. The current results were primarily focused on the multi-rigid body simulation or a simple multi-flexible body simulation, with little regard for the correctness of longitudinal loads and their experimental confirmation, particularly wheel–axle loads. Based on a genuine oleo-pneumatic landing gear drop test of a large civil aircraft, enhanced multi-body dynamics simulation research is carried out, considering the structural flexibility and bearing support by adopting flexible multi-bodies modeling and rigid-flex coupling contacts. When compared to the test data, which purposefully measured the longitudinal wheel–axle loads, the simulation results show that the loads, shock absorber compression, and shock absorber inner pressures are all within good agreement. Furthermore, the influence of structural stiffness and bearing contact was investigated by adjusting the model settings to confirm their importance. [ABSTRACT FROM AUTHOR]

Payloads for light unmanned free balloons must meet several safety requirements such as being able to protect the inner electronics in order to extract scientific data and to reduce the chance of inflicting personal injury in case of an accidental fall. This article proposes a novel payload structure, which exhibits the form of a dodecahedron. The actual form was determined by carrying out theoretical drop tests on different polyhedrons using the finite element method (FEM). From the simulations, it could be deduced that the dodecahedron was the optimal choice, since the duration of the impact was longer, while the impact force was slightly lower. The payload was produced by additive technologies; therefore, after performing tensile tests on probable materials, PLA was selected as the optimal candidate. The theoretical results about the dodecahedron's ability were validated by laboratory and real-life drop tests, where the new payload was subjected to 56% less impact force under a 78% longer collision time compared to a classic, rectangular cuboid design. Based on these tests, it was demonstrated that the new structure is safer and it is applicable. [ABSTRACT FROM AUTHOR]

Lycium barbarum L. (L. barbarum) is an economic crop with high added value and profit. Vibration harvesting is a suitable mechanized harvesting method for L. barbarum. It bruises easily during harvesting due to the softness and vulnerability of fresh ripe fruit, resulting in economic losses. This study analyzed the fruit drop and collision during vibration harvesting. High-speed photography was used to obtain the impact speed and angle of the falling fruit, and a kinematic analysis of the collision with the collection surface was conducted. The majority of the fruit had an impact speed of 3-6 m/s and an impact angle of 30-90° with the collection surface. A drop test was conducted to assess fruit bruising, and the impact speed was converted to the drop height. An orthogonal rotation experiment was conducted, and mathematical model was established between the drop height, impact angle, and impact material, and the fruit bruise rate, maximum impact force, recovery coefficient, and impact time. The effects of the factors on the fruit bruise rate, maximum impact force, recovery coefficient, and impact time were analyzed. The test results show that a vibration harvesting device for L. barbarum should be designed to reduce the height between the fruit and the collection surface and utilize a tilted collection surface and high cushioning materials to reduce the fruit bruising. This study provides guidance for subsequent research on the bruising of L. barbarum during vibration harvesting and harvester design. [ABSTRACT FROM AUTHOR]

For traumatic lumbar spine injuries, the mechanisms and influence of anthropometrical variation are not yet fully understood under dynamic loading. Our objective was to evaluate whether geometrically subject-specific explicit finite element (FE) lumbar spine models based on state-of-the-art clinical CT data combined with general material properties from the literature could replicate the experimental responses and the fracture locations via a dynamic drop tower-test setup. The experimental CT datasets from a dynamic drop tower-test setup were used to create anatomical details of four lumbar spine models (T12 to L5). The soft tissues from THUMS v4.1 were integrated by morphing. Each model was simulated with the corresponding loading and boundary conditions from the dynamic lumbar spine tests that produced differing injuries and injury locations. The simulations resulted in force, moment, and kinematic responses that effectively matched the experimental data. The pressure distribution within the models was used to compare the fracture occurrence and location. The spinal levels that sustained vertebral body fracture in the experiment showed higher simulation pressure values in the anterior elements than those in the levels that did not fracture in the reference experiments. Similarly, the spinal levels that sustained posterior element fracture in the experiments showed higher simulation pressure values in the vertebral posterior structures compared to those in the levels that did not sustain fracture. Our study showed that the incorporation of the spinal geometry and orientation could be used to replicate the fracture type and location under dynamic loading. Our results provided an understanding of the lumbar injury mechanisms and knowledge on the load thresholds that could be used for injury prediction with explicit FE lumbar spine models. [ABSTRACT FROM AUTHOR]

Copyright of Gazi Üniversitesi Fen Bilimleri Dergisi Part C: Tasarım ve Teknoloji is the property of Gazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

为保证包装产品的质量，通过对普通瓶型和加强筋瓶型PET瓶进行壁厚测定、抗压试验和跌落试验来比较瓶身结构对瓶子的抗压性能及标签完好性的影响。结果表明，加强筋瓶型的瓶子更厚，垂直抗压能力更好，对标签的保护程度优于普通瓶型的，且瓶子质量的改变不影响其性能。综上，选择加强筋瓶型的PET瓶更有利于保证包装产品的质量。In order to ensure the quality of the packaged products, through wall thickness measurement, compression test and drop test of ordinary PET bottle and reinforced PET bottle, the influences of bottle body structure on the compression performance of bottles and label integrity were compared. The results showed that the reinforced bottle was thicker, its vertical compression resistance and label protection were better than the ordinary bottle, and the change of bottle mass did not affect its performance. In conclusion, choosing reinforced PET bottle is more conductive to ensure the quality of the packaged products.

Cu-to-Cu direct bonding has been regarded as an important approach to achieve three-dimensional integrated circuit integration. This study aims to investigate the effects of microstructure and Xenon flash exposure on the direct bonding of copper deposits. Copper electrodeposits, along with a sputtered deposit, with various grain sizes, preferred orientations, as well as surface hardnesses, were prepared to clarify the influence of individual factors quantitatively. Experimental results show that joint strength and grain boundary density followed a positively linear relationship regardless of other microstructural differences, suggesting the dominating role of grain boundary diffusion. Grain refinement can effectively enhance bonding strength, even only one side of the directly bonded joints possessed fine grains. Considering the portable device applications which may suffer from drop shocks, drop testing of the packages comprising sputtered copper on Si chips joined with electroplated copper on Al2O3 substrates assembled by thermal compression bonding was performed for the first time. Noticeably, a proper flash irradiaiton prior to bonding brought about not only remarkable improvement in shear strength by up to 60 % but also drop resistance for direct-copper bonds. The resistance against drop shock for directly-bonded daisy chains subjected to an appropriate light exposure prior to bonding was superior than the joints bonded using impact-resistant solders.

With the increased stress in people’s daily lives, the secretion of sweat from the human body has steadily increased. Therefore, textile industries continue to introduce various products to meet consumers’ demands. Thus far, people use more cotton and polyester fabrics among other textile fabrics in their daily usage or total living period. Textile products, especially those made from cellulose fibers such as cotton, can promote the growth of microorganisms due to their high surface area and moisture retention. In contrast to cellulosic materials, polyester contains no chemically functional or hydrophilic groups. Therefore, it is necessary to ensure wearers’ protection as both cotton and polyester can create unwanted odors due to the decomposition of sweat by microorganisms. The application of chitosan on textile substrates is a useful approach for textile functionalization. Chitosan has been reported as a popular finishing agent due to its intrinsic properties, such as biocompatibility, biodegradability, non-toxicity, abundance in nature, antimicrobial, and antistatic ability, etc. In this study, the solution of chitosan was applied to 100 % cotton and polyester fabrics using a common pad-dry-cure technique. The resulting fabrics were characterized by drop-test, scanning electron microscopy (SEM), and color measurement. Thus, this study presents a small overview of the finishing using chitosan-containing recipes on both cotton and polyester fabrics.

The coefficient of restitution (COR) is used to estimate the equivalent free fall drop height of packaging during handling and transportation. Various experimental studies were designed to explore factors affecting the conversion of the COR to equivalent free fall drop height. These factors include the number of drops, drop height, drop orientation, drop base, temperature and humidity on the COR. The results indicate that the number of drops and drop orientation are the two most influential factors affecting COR values. As the package undergoes more drops, the COR increases. Among the various orientations, the COR is largest for flat drops, followed by edge and corner orientations. Within flat drops, a smaller impact area results in a smaller COR. Manufacturing joints and the flats, edges and corners adjacent to manufacturing joints tend to yield smaller COR values. A COR correction matrix was developed to correct the conventional COR calculation. This matrix allows engineers to refine COR values based on the number of drops and drop orientations in the field. The matrix‐corrected equivalent free fall drop heights demonstrated an average accuracy of 96%. Compared to the conventional COR calculation method, it effectively reduces errors by a factor of 2–3. [ABSTRACT FROM AUTHOR]

Purpose: The primary objective of this study is characterizing the anisotropic mechanical properties of corrugated cardboard and simultaneously simulating its drop cushioning dynamic effects under various drop conditions. Design/methodology/approach: Static and dynamic tests were conducted on corrugated cardboard to obtain adequate experimental data in different directions. An effective anisotropic constitutive model is introduced by developing the honeycomb materials model in ANSYS LS-Dyna, and an effective approach is established toward effectively determining the material parameters from the test data obtained. The model is validated by comparing simulation results with experimental data from five drop conditions, including bottom drop, front drop, side drop, 30° side drop and edge drop. Additionally, simulations are conducted to study the cushioning performance of the packaging by dropping the corrugated cardboard at different heights. Findings: The study establishes a fast and effective approach to simulating the drop cushioning performance of corrugated cardboard under various drop conditions, which demonstrates good agreement with experimental data. Originality/value: This approach is of value for packaging protection and provides guidance for stacking of packaging during transportation. [ABSTRACT FROM AUTHOR]

The aim of this article was to assess the behavior of polymer composites under low-velocity impact considering stress concentrators (two side holes at the point of impact) and determine the residual mechanical properties of these materials using FAI (Flexural After Impact). Analysis of residual properties ascertained the effects of damage and stress concentrators, assessing their individual influence in increasing the stress concentration factor (K). This analysis was conducted via tests that consider the separate effects of each case and a formulation that relates them. In addition, this paper also assessed the influence of void percentage on the impact and residual strength, developing two E-glass fiber fabric-based composites with different void percentage. The tests performed showed that impact damage increased the concentration factor of the material by 18%, but in samples tested with side holes, damage decreased residual strength by only 5%. [ABSTRACT FROM AUTHOR]

The investigation of multi-body dynamics (MBD) modeling for landing gear drop tests is a hot topic in the realm of landing gear design. The current results were primarily focused on the multi-rigid body simulation or a simple multi-flexible body simulation, with little regard for the correctness of longitudinal loads and their experimental confirmation, particularly wheel–axle loads. Based on a genuine oleo-pneumatic landing gear drop test of a large civil aircraft, enhanced multi-body dynamics simulation research is carried out, considering the structural flexibility and bearing support by adopting flexible multi-bodies modeling and rigid-flex coupling contacts. When compared to the test data, which purposefully measured the longitudinal wheel–axle loads, the simulation results show that the loads, shock absorber compression, and shock absorber inner pressures are all within good agreement. Furthermore, the influence of structural stiffness and bearing contact was investigated by adjusting the model settings to confirm their importance.

Landing impact load design is essential, but the process has rarely been fully described, and some designers have even neglected the differences between wheel-axle and ground-contact loads, as well as loads in the longitudinal direction, especially in experimental validations. In this paper, the entire design process of a nose landing gear is addressed, including a theoretical analysis of the unit and its experimental validation. In the theoretical analysis, a mathematical model of a two-mass system with four degrees of freedom was adopted, a computer simulation model was built accordingly, and a preliminary analysis was subsequently conducted to analyze the landing impact loads, verify the landing gear performance, and gauge the difference between the wheel-axle and ground-contact loads. For the experimental validation of the gear, a landing gear drop test was conducted in an optimized manner that emphasized pre-test preparation and during-test wheel-axle load measurement. The test results showed that both the vertical and less studied longitudinal loads, as well as the wheel-axle and ground-contact loads, had good agreement with the analysis; thus, the model, the tool, and the preliminary design were considered to be experimentally validated. [ABSTRACT FROM AUTHOR]

Purpose: Because of growing demand for slim, thin and cheap handheld devices, reduced-volume solder interconnects like land grid array (LGA) are becoming attractive and popular choices over the traditional ball grid array (BGA) packages. This study aims to investigate the mechanical shock and impact reliability of various solder alloys and BGA/LGA interconnect configurations. Design/methodology/approach: Therefore, this paper uses drop testing experiments and numerical finite element simulations to evaluate and compare the reliability performance of both LGA and BGA components when exposed to drop and impact loadings. Additionally, three common solder alloys, including 63Sn37Pb, SAC305 and Innolot, are discussed. Findings: The results of this study showed that electronic packages' drop and impact reliability is strongly driven by the solder configuration and the alloy type. Particularly, the combination of stiff solder alloy and shorter joint, LGA's assembled with SAC305, results in highly improved drop reliability. Moreover, the BGA packages' performance can be considerably enhanced by using ductile and compliant solder alloys, that is, 63Sn37Pb. Finally, this paper discussed the failure mode of the various solder configurations and used simulation results to explain the crack and failure situations. Originality/value: In literature, there is a lack of published work on the drop and impact reliability evaluation and comparison of LGA and BGA solders. This paper provides quantitative analysis on the reliability of lead-based and lead-free solders when assembled with LGA and BGA interconnects. [ABSTRACT FROM AUTHOR]

For dangerous goods packagings, drop testing onto an essential unyielding target can be used to assess the mechanical resistance to impact loads. Adopted regulations like Agreement concerning the International Carriage of Dangerous Goods by Road (ADR)/Regulation concerning the International Carriage of Dangerous Goods by Rail (RID) require that the impact surface provided shall be integral with a mass at least 50 times than that of the heaviest package to be tested. The problem is that many manufacturers do not possess impact targets that satisfy the required 50 times mass ratio for regulative drop tests during series production. The objective of this work is to verify existing and define improved criteria for impact target structures based on systematic investigations. Previous evidence highlights the relevance of other parameters in addition to the mass ratio. Therefore, in this research, a variation of drop test parameters was carried out experimentally. Furthermore, numerical vibration analysis was applied to investigate the deformability of the impact surface. The results conclude that the mass ratio of 1:50 cannot be defined as a decisive criterion. In order to determine the influence of further drop test parameters, the research findings were used to validate a parametric model that assesses impact target deflection. An approximation quality of over 90% was achieved. As a result, new evaluation criteria are proposed. First, a method for identifying critical impact target designs is provided. Second, a new comprehensive formula compares the approximated maximum deflection of a real impact target to the respective theoretical threshold derived from a worst‐case assumption. In practice, this leads to great advantages in the evaluation of already installed impact targets for dangerous goods packagings. [ABSTRACT FROM AUTHOR]

Article highlights Direction with protection most influenced by wrapping turns: parallel to tray surface and perpendicular to tray length. Acceleration profile and peak variance show when 3S package failed in fully suspended protection. Wrapping around the corners of the object greatly influences the 3S package performance in the tray length direction.

Energy-absorbing rockbolts have been widely adopted in burst-prone excavation support, and their serviceability is closely related to the frequency and magnitude of seismic events. In this research, the split-tube drop test with varying impact energy was conducted to reproduce the dynamic performance of MP1 rockbolts under a wide range of seismic event magnitudes. The test results showed that the impact process could be subdivided into four distinct stages, i.e. mobilization, strain hardening, plastic flow (ductile), and rebound stage, of which strain hardening and plastic flow are the primary energy absorbing stages. As the impact energy per drop increases from 8.1 to 46.7 kJ, the strain rate of the shank varies between 1.20 and 2.70 s−1, and the average impact load is between 240 and 270 kN, which may be considered as constant. The MP1 rockbolt has a cumulative maximum energy absorption (CMEA) of 31.9–40.0 kJ/m, with an average of 35.0 kJ/m, and the elongation rate is 11.4%–14.7%, with an average of 12.7%, both of which are negatively correlated with the impact energy per drop. Regression analysis shows that energy absorption and shank elongation, as well as momentum input and impact duration, conform to the linear relationship. The complete dynamic capacity envelope of MP1 rockbolts is proposed, which reflects the dynamic bearing capacity, elongation, and distinct stages. This study is helpful to better understand the dynamic characteristics of energy-absorbing rockbolts and assist design engineers in robust reinforcement systems design to mitigate rockburst damage in seismically active underground excavations.

Metal shock absorbers of nuclear spent fuel casks for storage have been developed. The shock absorbers are equipped at both ends of the cylindrical cask to reduce the impact force and maintain the safety functions of the cask in the event of an unexpected drop accident. As a countermeasure to meet long-term storage requirement (against material degradation), the shock absorber was designed with metal instead of usual wood and its energy absorption performance against 2.5 m height drop (maximum hypothetical handling height in nuclear power plants during storage) was evaluated. With the aim of reducing compression stiffness the metal shock absorber was designed from a perforated aluminum block. Two tests were done for static compression characteristics using cubic specimens and energy absorption capacity against 2.5 m drop using 1/4 scale mockup of metal shock absorber. In addition, a drop test using 1/10 scale mockup cask with metal shock absorbers confirmed that it could deform as assumed and reduce the applied acceleration on the cask to a safety level at crash. As a result of the finite element analysis of the cask with designed shock absorbers dropped from a height of 2.5 m that was verified by the drop test, the fitting portion between body and primary lid in the cask remained within elastic deformation thus confirming the design’s validity.

The modeling clay is an oil-based soft, flowable, and pliable material made from waxes and oils. Besides its primary use for making sculptures, the modeling clay is commonly used to evaluate bulletproof vests and simulate metal manufacturing processes by conformation. In ballistic tests, the clay is used to retain the deformation of the rear face of body armors; and in the study of metal forming processes, it is used as a physical model to provide information on the plastic flow. However, its mechanical dynamic behavior is not entirely understood. In this study, Plastilina Roma No. 1 modeling clay was mechanically characterized using the power-law constitutive model at medium strain rates (10 2 s − 1). The material parameters were determined using a penetration model based on the Cavity Expansion Theory and an inverse technique involving the comparison of the model with experimentation. The optimum set of constitutive parameters was found by reducing the difference of the calculated penetration profile and the measurements from a drop test. This optimization process was programmed on the MATLAB–Simulink environment. The determined material parameters were validated by comparing the results from a computational model with three test set-ups. Finite element model results show good concordance with experimental measurements. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To determine the damage characteristics of potato falling on the separating screen and their relationship with the vibration characteristics, it is expected to provide a reference for the structural optimization of potato harvesting related machinery. The vibration characteristics of the separating screen were theoretically analyzed and a forced vibration model of separating screen was developed. The effects of vibration model parameters on the damage volume of potatoes were studied by single‐factor experiments with fall height, potato mass, fall direction, and potato varieties as experimental factors. Especially, the changes of decay coefficient α and the potato damage volume with test factors were obtained: the attenuation coefficient α increased with increasing falling height and potato mass and showed a significant correlation with potato damage volume. The decay coefficient α becomes largest when the potato falls along the length direction and smallest when it falls along the thickness direction. The α decreased with increasing hardness of potato varieties and showed a significant negative correlation with potato damage volume. Fitting equations between the attenuation coefficient α and the damage volume for each effects were established to predict the potato damage under different height, mass, and variety, as follows: V1 = 498035α − 2516, V2 = 209646α − 286, and V3 = −84397α + 1149. Practical Applications: During the mechanized harvest process, severe potato damage occurred on the swing separation screen. This will seriously affect the quality and economic value of potatoes. At present, there are few studies on the vibration damage theory and experiment during potato harvest. Therefore, in order to clarify the vibration characteristics of the separation screen and its relationship with the potato damage characteristics, we studied the influence of the vibration characteristics on the potato damage through the drop test, and established the vibration model of the separation screen. The relationship between the model parameters and the potato damage volume was further explored, and a mathematical model was developed to predict the volume of potato damage. This study provides a reference for the study of the coupled vibration of the potato soil mixture and the optimization of the potato soil separation device. [ABSTRACT FROM AUTHOR]

The determination of suitable testing and qualification procedures for fiber-reinforced polymer matrix composite structures is an active area of research due to the increased demand, especially in the field of aerospace. This research illustrates the development of a generic qualification framework for a composite-based main landing gear strut of a lightweight aircraft. For this purpose, a landing gear strut composed of T700 carbon fiber/epoxy material was designed and analyzed for a given lightweight aircraft having mass of 1600 kg. Computational analysis was performed on ABAQUS CAE® to evaluate the maximum stresses and critical failure modes encountered during one-point landing condition as defined in the UAV Systems Airworthiness Requirements (USAR) and Air Worthiness Standards FAA FAR Part 23. A three-step qualification framework including material, process and product-based qualification was then proposed against these maximum stresses and failure modes. The proposed framework revolves around the destructive testing of specimens initially as per ASTM standards D 7264 and D 2344, followed by defining the autoclave process parameters and customized testing of thick specimens to evaluate material strength against the maximum stresses in specific failure modes of the main landing gear strut. Once the desired strength of the specimens was achieved based on material and process qualifications, qualification criteria for the main landing gear strut were proposed which would not only serve as an alternative to drop test the landing gear struts as defined in air worthiness standards during mass production, but would also give confidence to manufacturers to undertake the manufacturing of main landing gear struts using qualified material and process parameters. [ABSTRACT FROM AUTHOR]

It is important to achieve high strength, high modulus of elasticity, good energy damping for lightweight armor materials. For this purpose, two or more similar or different materials are combined at the macro level. In this way, a new structure emerges that we call composite material. A composite is a new structure in which the good properties of the components in its structure become evident in the material. Research on the production and mechanical properties of composites that meet the needs of the developing technology continues. Military personnel, armored vehicles and many security elements are tested in the field with a lot of threats (such as mines, armor piercing ammunition, explosives etc.). Therefore, the armor used by security elements should be strengthened without compromising features such as lightness, cost and longterm use. This study covers the development of Kevlar's ballistic properties by impregnating Shear Thickening Fluid (STF). STF is composed of silica (AEROSIL 200) and polyethylene glycol (PEG 400). STF-impregnated Kevlar fibers have been subjected to impact testing at low and high speeds. Low-speed tests were carried out with a drop tower. High-speed tests were carried out according to NIJ 0101.06 Level II standards. The mass fraction of silica in the STF was determined as the research parameter. The change in the behavior of the materials with the change of silica ratio was investigated; Although improvements were observed in energy dissipation in low-speed impacts, it was noted that ballistic behavior improved up to a certain point, and then the improvement in behavior decreased. [ABSTRACT FROM AUTHOR]

The oil characteristics and inflation pressure inside the oil-air shock absorber will change with the ambient temperature,which will affect the cushioning performance of landing gear.In order to explore the effect of temperature on the cushioning performance of oil-air landing gear,a buffer environment temperature simulation method is proposed based on the landing gear drop shock test,and the cushioning performance of oil-gas landing gear buffer at ambient temperature from 20 to 80℃is studied.The results show that within the studied temperature range,the initial inflation pressure of the buffer is sensitive to the change of temperature.With the increase of temperature,the stiffness of the air spring in the buffer increases and the oil damping force decreases,the ground vertical load of the landing gear system increases and the efficiency coefficient of the buffer system decreases.The temperature has a significant impact on the performance of the oil-gas landing gear buffer.

International Atomic Energy Agency (IAEA) regulations for the safe transport of radioactive materials require a 9-m drop test for the Type B packages, such as large spent fuel (SF) transport casks. In vertical drop tests, where the SF cask is in a lid-down orientation, it has been observed that the pullout force of the lid bolts delays the impact from the grounding of the specimen. This phenomenon is known as delayed impact and is of significant concern for the safe transport of radioactive materials. Previously, the delayed impact has been considered to occur because of the delayed collision of the contents in the cask with its lid when there is a gap between the contents and lid. In such case, since the lid of the SF cask is usually fixed at the end of the cask body, the contents push the lid plate to increase the pullout force, leading to the delayed impact. Herein, a new noise reduction method, which is the acceleration integrated velocity approximation (AIVA) method, is proposed to analyze the acceleration data from a 9-m drop test. Based on a reevaluation of the existing acceleration data using the proposed noise reduction method, it is concluded that the delayed impact could occur even when there is no gap between the contents and lid. To evaluate practical SF casks, the mechanical characteristics of the contents are estimated based on the published results of a full-scale drop test, and the delayed impact in a no-gap case is estimated based on the obtained characteristics. In a previous safety analysis of a wet-type SF cask, the delayed impact was not considered to be important, since the contents might be restricted by the water present inside the cask. However, based on this study, it is concluded that the delayed impact caused by the content reaction should be considered even in such no gap cases. • The delayed impact was considered attributed to collision of contents inside cask. • Acceleration waveforms noise of the SF cask drop test was reduced by AIVA method. • The delayed impact of SF cask drop test was analyzed and evaluated by spring model. • The practical spring characteristics of SF were determined by published article. • By the spring model, delayed impact scenario in the no gape case can be proposed. [ABSTRACT FROM AUTHOR]

A molded expanded polystyrene (EPS) cushion is a flexible, closed-cell foam that can be molded to fit any packing application and is effective at absorbing shock. However, the packaging waste of EPS cushions causes pollution to landfills and the environment. Despite being known to cause pollution, this sustainable packaging actually has the potential to reduce this environmental pollution because of its reusability. Therefore, the objective of this study is to identify the accurate design parameter that can be emphasized in producing a sustainable design of EPS cushion packaging. An experimental method of drop testing and design simulation analysis was conducted. The effectiveness of the design parameters was also verified. Based on the results, there are four main elements that necessitate careful consideration: rib positioning, EPS cushion thickness, package layout, and packing size. These parameter findings make a significant contribution to sustainable design, where these elements were integrated directly to reduce and reuse packaging material. Thus, it has been concluded that 48 percent of the development cost of the cushion was decreased, 25 percent of mold modification time was significantly saved, and 27 percent of carbon dioxide (CO2) reduction was identified. The findings also aided in the development of productive packaging design, in which these design elements were beneficial to reduce environmental impact. These findings had a significant impact on the manufacturing industry in terms of the economics and time of the molded expanded polystyrene packaging development. [ABSTRACT FROM AUTHOR]

Hydrogen, a clean and renewable energy fuel is termed the fuel of the future. Although the production of hydrogen is well-established, its storage is a major concern. The conventional metallic cylinders are bulky and cause difficulties in transportation and long-term sustenance, calling for the exploration of alternatives that are durable, lightweight and easy to fabricate. Composite high-pressure cylinders appear to be a promising solution for the storage of gaseous hydrogen. In this work, weight optimization of Type 1, Type 3 and Type 4 cylinders have been performed using lightweight materials such as Titanium, Acrylonitrile Butadiene Styrene (ABS) and Carbon fibre. The stability of these cylinders has been confirmed via structural analysis. In addition, explicit analyses such as drop and crash tests have also been carried out to evaluate the performance of the cylinder. Type 1 shows the least deformation, however, failed both the crash as well as drop tests. Whereas, the type 4 cylinder exhibits better performance in both structural and explicit simulations and is 39.2% lighter than the Type 1 cylinder. Such type 4 cylinders can revolutionize the energy storage sector and can advance mobility to a great extent in the near future. [Display omitted] • Cylinder modelled using Titanium, Acrylonitrile Butadiene Styrene and Carbon Fibre. • Weight Optimization of cylinder through structural analysis. • Evaluating explicit performance of the cylinder though drop and crash tests. • Influence of carbon fibre in absorbing shock during drop and crash tests. [ABSTRACT FROM AUTHOR]

Roma Plastilina No. 1 clay has been widely used as a conservative boundary condition in bulletproof vests, namely to play the role of a human body. Interestingly, the effect of this boundary condition on the ballistic performance of the vests is indiscernible. Moreover, back face deformation should be characterized by measuring the indentation in the deformed clay, which is important for determining the lethality of gunshots. Therefore, several studies have focused on modeling not only bulletproof vests but also the clay backing material. Despite various attempts to develop a suitable numerical model, determining the appropriate physical parameters that can capture the high-strain-rate behavior of clay is still challenging. In this study, we predicted indentation depth in clay using an artificial neural network (ANN) and determined the optimal material parameters required for a finite element method (FEM)-based model using an inverse tracking method. Our ANN-FEM hybrid model successfully optimized high-strain-rate material parameters without the need for any independent mechanical tests. The proposed novel model achieved a high prediction accuracy of over 98 % referring impact cases. [ABSTRACT FROM AUTHOR]

To investigate the ability of energy absorption of composite beams with corrugated web in the crash process, the drop tests of composite beams with corrugated web are carried out, and the morphology of fracture, load and energy history curves are obtained. Based on the ABAQUS/Explicit platform, a simulation analysis model is developed to simulate the impact collapse process of composite beams with corrugated web by secondary development. The improved Hashin criterion and Choi‑Chang criterion are used with Cohesive interface element. The anisotropy and progressive damage of composite laminates are implemented. Specific energy absorption (SEA) and average loads are obtained by numerical simulation, which is verified by experimental results. Based on this model, further studies on the energy absorption of composite beams with corrugated web are analyzed with different wavenumbers. The progressive damage of corrugated web beams under impact loads are simulated by the developed FE model. The relative errors of average crushing load are small, which verifies the validity of the FE model. When the wave length of web is defined, the length of corrugated web beams has influence on energy absorption under impact. The shorter beam with corrugated web is instability and ineffective in energy absorption. [ABSTRACT FROM AUTHOR]

This paper presents the evaluation process of a Recovery System developed for the ILR-33 AMBER suborbital rocket, designed for small payloads and capable of launching 10 kg to altitudes up to 100 km. The Recovery System allows for retrieval of the payload by means of highangle-of-attack motion with flat spin and a two-stage parachute system. After presenting the design of the Recovery System, this study focuses mainly on a subsonic drop test campaign that allowed the system to be qualified for the first version of the AMBER rocket vehicle. Analytical and numerical methods for the recovery phase development are presented and compared with the experimental results obtained from the drop tests. Overall, the drop tests proved to be indispensable for the successful development of the AMBER rocket platform, by providing essential load and spin data to feed back into the re-design processes, and also by confirming the viability of the concept of three-stage parachute recovery. [ABSTRACT FROM AUTHOR]