Crashworthiness Simulation Analysis of Light Sport Aircraft Fuselage Structure

Impact, absorption and evaporation of raindrops on building facades

Impingement on blade surface by fine particles with high velocity is commonly seen in steam turbines, gas turbines and compressors, which affect the service life and reliability of the equipment. Study on particles’ rebound characteristics is of great significance to reduce the blade erosion and to control particle trajectory. Based on the nonlinear explicit dynamics analysis software ANSYS/LS-DYNA, the impacts of fine spherical particles with different diameters (20 to 500μm) on a typical martensitic stainless steel (AISI 403) target with high velocity (50 to 250m/s) have been systematically studied. The influences of incident velocities, impact angles, particles sizes on its rebound characteristics, relative impact depth, and relative dissipated energy have been analyzed. Results show that velocity restitution coefficient e decreased with the impact angle β1, the incident velocity V1, and the particle size dp. However, the role of particle size on the velocity restitution coefficient seemed to be far less than that of the other two factors. Both of particle’s tangential and normal velocity coefficient of restitution declined with the increasing impact angle in most cases. However, when the incident velocity V1 = 200m / s and the impact angle β1 > 45°, the tangential velocity restitution coefficient et of 100 μm and 200 μm particles increased with the increase in the impact angle β1. The reason might be that the relative impact depth drel was located a zone ranged from 0.1515 to 0.1677, where the tangential rebound behavior could be enhanced. Most of the variation of the tangential and normal velocity restitution coefficient along β1 decreased with the increase in the particle diameter. However, when V1 = 200m/s and β1 > 15°, the tangential reflected velocity of the larger particles was enhanced gradually. In addition, the values of the relative impact depth drel increased with the increasing impact angle and incident velocity, and it increased with the increasing particle diameter in most cases. The relative dissipated energy of particles steadily increased with the impact angle and incident velocity, respectively. Particle diameter had little effect on energy dissipation in comparison with the impact angle and incident velocity.

ABSTRACTRoadside safety barriers designs are tested with passenger cars in Europe using standard EN1317 in which the impact angle for normal, high and very high containment level tests is 20°. In comparison to EN1317, the US standard MASH has higher impact angles for cars and pickups (25°) and different vehicle masses. Studies in Europe (RISER) and the US have shown values for the 90th percentile impact angle of 30°–34°. Thus, the limited evidence available suggests that the 20° angle applied in EN 1317 may be too low.The first goal of this paper is to use the US NCHRP database (Project NCHRP 17–22) to assess the distribution of impact angle and collision speed in recent ROR accidents. Second, based on the findings of the statistical analysis and on analysis of impact angles and speeds in the literature, an LS-DYNA finite element analysis was carried out to evaluate the normal containment level of concrete barriers in non-standard collisions. The FE model was validated against a crash test of a portable concrete barrier carried out at the UK Transport Research Laboratory (TRL).The accident data analysis for run-off road accidents indicates that a substantial proportion of accidents have an impact angle in excess of 20°. The baseline LS-DYNA model showed good comparison with experimental acceleration severity index (ASI) data and the parametric analysis indicates a very significant influence of impact angle on ASI. Accordingly, a review of European run-off road accidents and the configuration of EN 1317 should be performed.

In-depth accident data were collected to investigate vehicle impact conditions (e.g., crash severity, impact speed, impact angle, and orientation) for crashes with roadside obstacles and features. Descriptive statistics of these variables are presented, including statistics for the data segregated by highway class, speed limit, and access control. Relationships between impact conditions and these segregating factors were explored. Statistical tests were applied to investigate the association between speed and angle, and univariate distributions were fitted for these two variables. Impact speed and impact angle are independent for most highway classes when segregated by highway class, and they have a relatively weak negative correlation. Both impact speed and angle data for all highway classes follow a normal distribution. Joint impact distributions were then determined using the bivariate normal distribution. The findings of this study are of significant importance to the establishment or reinforcement of full-scale vehicle crash testing guidelines, to benefit–cost analysis procedures, and to highway designers who seek more detailed information on probabilities of impact conditions for different highway classes.

Study on the motion law and force chain characteristics of buffer cushion layer of rolling stone impacting shed hole

The flow and heat transfer characteristics of a droplet obliquely impact on a stationary liquid film is numerically studied by using a coupled level set and volume of fluid method (CLSVOF). The effects of impact angle, Weber number, and film thickness are analyzed. As compared with the normal impact, the flow features and surface heat flux distribution for oblique impact are asymmetric and where the secondary droplets only can be observed on one side. Corresponding mechanisms have also been interpreted. The maximum value of the local surface heat flux decreases and moves to the right with the increase in impact angle, while the minimum local surface heat flux on both sides increases as the impact angle increases. With a greater Weber number or a thinner film thickness, the maximum local surface heat flux is higher, while the minimum local surface heat flux on both sides appears to be an opposite trend. In addition, the impact angle has little effect on the average surface heat flux.

The effect of test parameters on the impact resistance of a stainless steel/rubber/composite hybrid structure

The jet erosion of fibre reinforced plastics (FRPs) has been reported in many literatures available, but very few have reported on their slurry erosion behaviour of FRPs. Furthermore, limited studies have paid attention on slurry erosion characterisation of filler incorporated FRPs. Hence, present study was focused on slurry erosion behaviour of alumina fillers incorporated glass/epoxy composites. The parameters considered were slurry concentration, contact angle and impact velocity. The experimental results reveal that increase in filler percentage increased the erosion resistance of glass/epoxy composites. The increase in slurry concentration and impact velocity has resulted in higher amount of erosion of studied composites. The material loss due to erosion increased with increase of impact angle till 45°, whereas further increase in impact angle caused reduction in wear. Erosion mechanisms were studied through SEM image of eroded samples. Worn surface analysis revealed that plastic deformation, matrix debonding with microcutting, microploughing, and pulverisation were dominant erosion mechanisms at 45° to 60° impact angle.

Composites have become extensively used in aircraft, including the latest Airbus A380 and Boeing 787 models. Due to their high specific strength ratio, the composites can help to reduce fuel consumption. For this reason, small business jets and light aircraft have begun to use composites in their fuselage designs. The main purpose of this study is to analyze the reaction of the composite landing gear of a light sport aircraft (LSA), under loading. Finite element analysis software was used to analyze and compare the static and dynamic loads on the LSA landing gear. Takeoff weight and sink speed, defined by FAR and ASTM, were used as parameters. This work investigated three different types of landing gear materials: aluminum alloy, glass fiber reinforced composite and carbon fiber reinforced composite. The maximum stress, maximum strain and displacement of landing gear of different shapes (leaf, column and tube shapes) was also measured. Of all the samples tested, tube-shaped glass fiber reinforced composite landing gear exhibited the lowest maximum stress under a static load; it also exhibited the smallest maximum strain and y-axis displacement. The results for dynamic load show taht column-shaped landing gear exhibits the smallest maxiumum stress. The results also show that landing gear made with glass fiber reinforced composite exhibits the lowest maximum strain under a dynamic load, while landing gear made with carbon fiber reinforced composite exhibits the largest displacement of the three materials.

Experimental study on the rebound characteristics of high temperature alumina droplets impacting on an inclined cold wall

Factors associated with proximal femur fracture determined in a large cadaveric cohort.

In this paper, normal and tangential coefficients of restitution for gaseous molecules colliding with layerwise (single and few layers) graphene nanosheets were calculated using non-equilibrium molecular dynamics method. The normal and tangential coefficients of restitution depend on impact angle, velocity and landing position of projectiles. These parameters were evaluated computationally by implementation of several operations. Some differences were observed between proposed problem and macro-scale nature. The most notable difference was proportionality between the restitution coefficients and impact velocity, while in the case of macro-scale systems, they have inverse relation. Number of layers of graphene substrate does not contribute significantly to the normal and tangential coefficients of restitution. On the other hand, except for hydrogen, where its normal coefficient of restitution is approximately unity, the normal coefficient of restitution for other gasses increases as impact angle increases. Furthermore, tangential coefficients of restitution reduce with impact angle. These results can offer additional insights for further understanding the impact mechanisms and bombardment-related phenomena in low-dimensional materials. Presented results could be utilised to optimise some applied operations such as porosity generation via bombardment of layered nanostructures, gas detection process, thermal management and pressure sensor applications.

This paper describes a fault detection procedure based on the analysis of the properties of the residuals of an errors-in-variables model. This procedure has been applied to the detection of flaps servo actuator faults on a light sport aircraft. The results obtained on real data collected in actual flight conditions have shown that this kind of fault and even its magnitude can be reliably detected by means of the proposed procedure.

The issue of expanding flight privileges that do not require medical oversight is currently an important topic, especially in the United States. We compared personal flying accident rates in aircraft with special light sport aircraft (SLSA) and experimental light sport aircraft (ELSA) airworthiness certificates to accident rates for personal flying in other general aviation (GA) aircraft. To calculate accident rates, personal flying hours were obtained from the annual FAA General Aviation and Part 135 Activity Surveys, and numbers of personal flying accidents were obtained from the NTSB accident database. Overall and fatal personal flying accident rates for the SLSA and ELSA groups and other GA aircraft were calculated and accident rates were compared. The overall personal flying accident rate for SLSA and ELSA was found to be 29.8 per 100,000 flight hours and the fatal accident rate was 5.2 per 100,000 flying hours. These are both significantly greater than the overall personal flying rate of 12.7 per 100,000 h and fatal rate of 2.6 per 100,000 h for other GA aircraft. Although this study has several limitations, the significantly higher accident rates in the sport pilot aircraft suggests caution when expanding sport pilot privileges to include larger, more complex aircraft. Mills WD, DeJohn CA. Personal flying accident rates of selected light sport aircraft compared with general aviation aircraft. Aerosp Med Hum Perform. 2016; 87(7):652-654.

In this paper, the commercial FEM software package ABAQUS 6.14/EXPLICIT is used to model a vibration assisted nano impact machining process by loose abrasives (VANILA), in which an atomic force microscope (AFM) is used as a platform and the nanoabrasives (diamond particles) injected in slurry between the workpiece (silicon) and the vibrating AFM probe impact the workpiece and result in nanoscale material removal. The FEM model is validated first and then is used to investigate the influence of impact speed, impact angle, and the frictional coefficient between the workpiece and abrasives on the nanocavity's size and depth. It is concluded that the impact speed, impact angle, and frictional coefficient between the silicon workpiece and nanoabrasives have substantial influence on the nanocavity's size and depth, the optimal size of which along with material removal rate might be achieved by simultaneously considering impact speed, impact angle, and frictional coefficient. [Submitted 20 March 2018; Accepted 23 December 2018]