Application of an Additive Manufactured Hybrid Metal/Composite Shock Absorber Panel to a Military Seat Ejection System

In this work, a preliminary numerical assessment on the application of an additive manufactured hybrid metal/composite shock absorber panels to a military seat ejection system, has been carried out. The innovative character of the shock absorber concept investigated is that the absorbing system has a thickness of only 6 mm and is composed of a pyramid-shaped lattice core that, due to its small size, can only be achieved by additive manufacturing. The mechanical behaviour of these shock absorber panels has been examined by measuring their ability to absorb and dissipate the energy generated during the ejection phase into plastic deformations, thus reducing the loads acting on pilots. In this paper the effectiveness of a system composed of five hybrid shock absorbers, with very thin thickness in order to be easily integrated between the seat and the aircraft floor, has been numerically studied by assessing their ability to absorb the energy generated during the primary ejection phase. To accomplish this, a numerical simulation of the explosion has been performed and the energy absorbed by the shock-absorbing mechanism has been assessed. The performed analysis demonstrated that the panels can absorb more than 60% of the energy generated during the explosion event while increasing the total mass of the pilot-seat system by just 0.8%.

The Effect of Relative Porosity on the Survivability of a Powder Metallurgy Part During Ejection

The desire to produce functional powder metallurgy (PM) components has resulted in higher compression forces during compaction. This in turn increases the ejection stresses and therefore the possibility of failure during ejection. This failure can be caused by sprig back during ejection due to frictional forces that are generated between the powder part and the die walls. In order to predict these factors a stress analysis of the powder part during ejection was done. Due to complexity, finite element analysis was used to model the powder during compaction and ejection. Since the ejection stage is the most critical stage of the PM process, it is essential to understand the factors that determine the survivability of a part during this stage. This work uses experimental data, finite element modeling and reliability analysis to determine the probability of failure of metallic powder components during the ejection phase. The results show that there is an increased possibility of failure during ejection as compaction pressure is increased. This information can be used by designers and process planners to determine the optimal process parameters that need to be adopted for optimal outcomes during powder metallurgy.

The Effect of Relative Porosity on the Survivability of a Powder Metallurgy Part During Ejection

The desire to produce functional powder metallurgy (PM) components has resulted in higher compression forces during compaction. This in turn increases the ejection stresses and therefore the possibility of failure during ejection. This failure can be caused by sprig back during ejection due to frictional forces that are generated between the powder part and the die walls. In order to predict these factors a stress analysis of the powder part during ejection was done. Due to complexity, finite element analysis was used to model the powder during compaction and ejection. Since the ejection stage is the most critical stage of the PM process, it is essential to understand the factors that determine the survivability of a part during this stage. This work uses experimental data, finite element modeling and reliability analysis to determine the probability of failure of metallic powder components during the ejection phase. The results show that there is an increased possibility of failure during ejection as compaction pressure is increased. This information can be used by designers and process planners to determine the optimal process parameters that need to be adopted for optimal outcomes during powder metallurgy.

Regional Strain Pattern Index—A Novel Technique to Predict CRT Response

Background: Cardiac resynchronization therapy (CRT) improves outcome in patients with heart failure (HF) however approximately 30% of patients still remain non-responsive. We propose a novel index—Regional Strain Pattern Index (RSPI)—to prospectively evaluate response to CRT. Methods: Echocardiography was performed in 49 patients with HF (66.5 ± 10 years, LVEF 24.9 ± 6.4%, QRS width 173.1 ± 19.1 ms) two times: before CRT implantation and 15 ± 7 months after. At baseline, dyssynchrony was assessed including RSPI and strain pattern. RSPI was calculated from all three apical views across 12 segments as the sum of dyssynchronous components. From every apical view, presence of four components were assessed: (1) contraction of the early-activated wall; (2) prestretching of the late activated wall; (3) contraction of the early-activated wall in the first 70% of the systolic ejection phase; (4) peak contraction of the late-activated wall after aortic valve closure. Each component scored 1 point, thus the maximum was 12 points. Results: Responders reached higher mean RSPI values than non-responders (5.86 ± 2.9 vs. 4.08 ± 2.4; p = 0.044). In logistic regression analysis value of RSPI ≥ 7 points was a predictor of favorable CRT effect (OR: 12; 95% CI = 1.33–108.17; p = 0.004). Conclusions: RSPI could be a valuable predictor of positive outcome in HF patients treated with CRT.

Large Eddy Simulation of Heat Transfer Within a Multi-Perforation Synthetic Jets Configuration

Synthetic jets are produced by devices that enable a suction phase followed by an ejection phase. The resulting mean mass budget is hence null and no addition of mass in the system is required. These particular jets have especially been considered for some years for flow control applications. They also display features that can become of interest to enhance heat exchanges, for example, for wall cooling issues. Synthetic jets can be generated through different mechanisms, such as acoustics by making use of a Helmholtz resonator or through the motion of a piston as in an experience mounted at Institut Pprime in France. The objective of this specific experiment is to understand how synthetic jets can enhance heat transfer in a multi-perforated configuration. As a complement to this experimental setup, large-eddy simulations are produced and analyzed in the present document to investigate the flow behavior as well as the impact of the synthetic jets on wall heat transfer. The experimental system considered here consists in a perforated heated plate, each perforation being above a cavity where a piston is used to control the synthetic jets. Placed in a wind tunnel test section, the device can be studied with a grazing flow and multiple operating points are available. The one considered here implies a grazing flow velocity of 12.8 m s−1, corresponding to a Mach number around 0.04, and a piston displacement of 22 mm peak-to-peak at a frequency of 12.8 Hz. These two latter parameters lead to a jet Reynolds number of about 830. A good agreement is found between numerical results and experimental data. The simulations are then used to provide a detailed understanding of the flow. Two main behaviors are found, depending on the considered mid-period. During the ejection phase, the flow transitions to turbulence and the formation of characteristic structures are observed; the plate is efficiently cooled. During the suction phase, the main flow is stabilized; the heat enhancement is particularly efficient in the hole wakes but not between them, leading to a heterogeneous temperature field.

Haemodynamic effects of hyperventilation on healthy men with different levels of autonomic tone

The topicality of the research is stipulated by insufficient study of the correlation between the functional state of the cardiorespiratory system and autonomic tone. The goal of the research was to analyze the changes of central haemodynamics with 10-minute regulated breathing at the rate of 30 cycles per minute and within 40 minutes of recovery after the test in healthy young men with different levels of autonomic tone. Records of the chest rheoplethysmogram were recorded on a rheograph KhAI-medica standard (KhAI-medica, Kharkiv, Ukraine), a capnogram - in a lateral flow on a infrared capnograph (Datex, Finland), and the duration of R-R intervals was determined by a Polar WIND Link in the program of Polar Protrainer 5.0 (Polar Electro OY, Finland). Systolic and diastolic blood pressure were measured by Korotkov’s auscultatory method by mercury tonometer (Riester, Germany). The indicator of the normalized power of the spectrum in the range of 0.15–0.40 Hz was evaluated by 5-minute records; three groups of persons were distinguished according to its distribution at rest by the method of signal deviation, namely, sympathicotonic, normotonic and parasympathicotonic. The initial level of autonomic tone was found to impact the dynamics of СО2 level in alveolar air during hyperventilation and during recovery thereafter. Thus, PetCО2 was higher (41.3 mm Hg) in parasympathicotonic than in sympathicotonic (39.3 mm Hg) and normotonic (39.5 mm Hg) persons. During the test, R-R interval duration decreased being more expressed in normotonic persons. At the same time, the heart index was found to increase in three groups, and general peripheral resistance – to decrease mostly in normo- and parasympathicotonic persons. In addition, the reliable increase of stroke index and heart index was found in these groups. In the recovery period after hyperventilation, the decrease of tension index and ejection speed was found in normo- and, particularly, parasympathicotonic compared with sympathicotonic men and the increase of tension phase and ejection phase duration.

420 Vortex formation in the pre-ejection phase in the left ventricle

Funding Acknowledgements Central Norway Regional Health Authority Background/Introduction: Vortex formation during left ventricular filling have been described since the 1980’s. We have investigated vortices in the left ventricle (LV) in healthy adults with a new technology based on high frame rate vector flow imaging (VFI) using blood speckle tracking. Purpose In this study we investigated the intraventricular flow pattern during the pre-ejection period. Material and methods We examined 21 healthy volunteers with a GE E95 ultrasound scanner, both in ordinary clinical mode and with an experimental setup. The latter was developed to achieve high frame rates by utilizing plane waves in combination with ECG-gating over multiple (5-6) heart cycles, allowing continuous acquisition of > 3500 FPS. Blood speckle tracking followed by model based regularization was used to obtain vector flow velocity measurements. Results During the pre-ejection phase we observed blood flow from the apex to the basis of the LV along the septum. At the base, the flow is deflected. A basal vortex is then created just above the mitral valve, which persists into the isovolumetric contraction (IVC). The lateral part of the vortex is then seen as an apically directed flow during IVC, as shown in the illustration. The vortex is also visible in the first phase of the ejection; the part of the blood in the LV not passing through the aortic valve is deflected and continues to conserve this vortex. These findings correspond to patterns found in colour M-Mode (CMM), showing a column of blood toward the apex in the IVC/early ejection phase. Time from peak R to the first sighting of this IVC vortex, and to the pre-ejection spike in tissue Doppler imaging (TDI), are similar, as reported in table 1. Conclusion(s): Our imaging setup allows for a very high temporal resolution (>3500 FPS), and enables VFI using blood speckle tracking, without using a contrast agent. We observed an intraventricular vortex during pre-ejection and into early ejection, with the same direction as the later vortices seen in filling. Initiation of this vortex may be conserved energy from late filling. This vortex is simultaneous with the pre-ejection spike in TDI. We postulate that this IVC vortex contributes to the closing of the anterior mitral leaflet in the IVC. As we also observe this vortex during the early ejection phase, we believe it may conserve rotational energy into early filling. Table 1 Timing of the IVC vortex and the pre-ejection spike in TDI Mean Median SD Min Max Time between R and the basal vortex during IVS (ms) 16,7 16 15,1 -13 47 Time between R and the pre-ejection spike TDI (ms) 16,3 21 14,4 -10 36 Abstract 420 Figure.

Quantitative Analysis of Left Ventricular Flow Dynamics in Latent Obstructive Hypertrophic Cardiomyopathy Using Vector Flow Mapping

Objectives: This study aimed to assess left ventricular (LV) energy loss (EL), circulation and vortex area using vector flow mapping (VFM) in patients with latent obstructive hyper­trophic cardiomyopathy (LOHCM) and nonobstructive hypertrophic cardiomyopathy (NOHCM). Methods: Fourteen LOHCM patients, 10 NOHCM patients, and 11 healthy individuals were evaluated by transthoracic echocardiography. An offline VFM workstation was used to analyze the LV blood flow patterns and fluid dynamics. The hemodynamic parameters, EL, circulation, and vortex area in 7 cardiac phases were calculated and analyzed. Results: Compared with controls and NOHCM patients, EL was significantly higher in ­LOHCM patients during the rapid ejection phase, slow ejection (SE) phase, and isovolumetric relaxation phase (p < 0.05). LOHCM patients also showed increased circulation during SE compared to the other two groups (p < 0.05). The ability to discriminate between NOHCM and LOHCM was assessed by the area under the receiver-operating characteristic curve (AUC), and EL during SE was found to have the largest AUC (0.964); the best cutoff value was 6.34 J/m3/s, with a sensitivity of 100% and specificity of 80%. Conclusions: The VFM technique can detect abnormal changes of LV EL and vortex characteristics in hypertrophic cardiomyopathy patients. Compared with controls and NOHCM patients, the LOHCM patients have worse systolic and diastolic functions.

P5686Role of internal stretch fraction parameter in quantification of mechanical dyssynchrony and prediction of cardiac resynchronization therapy outcome

Background Dyssynchronous activation of the heart is a prerequisite for cardiac resynchronization (CRT) efficacy. Although the main goal of CRT is to resynchronize ventricular contraction, our abilities to quantify mechanical dyssynchrony are still limited. However, so called “internal stretch fraction” (ISF) might serve as a marker of global discoordination of ventricular contraction. Methods and aim of the study Thirty-six CRT candidates and 7 healthy controls underwent MRI scanning. Feature tracking data (in short axis) were analysed using Segment software and cicrumferential strain (S)/ strainrate (SR) was obtained for each of the 16 left-ventricular (LV) segments. ISF was calculated as an extent of stretch (product of number of stretched regions and their mean amount of stretch, integrated over given time period; ie. area under the positive part of the global SR curve) in relation to the extent of shortening (area under the negative part of the global SR curve) in 6 basal LV segments during the ejection time (ET). The onset and end of ejection for ISF calculation were set from the global S curve (obtained by the averaging of S curves in 6 basal LV segments). For flow-derived ISF (FISF) parameter, ET was defined from the MRI-flow through pulmonic and aortic valve (Fig-1). Higher ISF and FISF marks more ineffective ventricular contraction. Aim of our study was to assess the ability of ISF and FISF to distinguish healthy controls from CRT candidates and to predict CRT responders (↓LVESV>15% after 6 months of CRT). Results ISF and FISF were significantly higher in CRT candidates than in healthy controls, greater difference between the two groups exhibited FISF (Fig-2). There were 37% of nonresponders among CRT recipients. Both parameters (ISF and FISF) were higher in future CRT responders. Cut-off value discriminating CRT responders from CRT nonresponders was >0,045 for ISF and >0,174 for FISF, however FISF had higher sensitivity than ISF (Fig-3; sensitivity 71% (ISF) versus 79% (FISF) and specificity 70% for both ISF and FISF). Conclusion Internal stretch fraction might be a useful parameter for selection of patients with discoordinated ventricular contraction who might profit from CRT. Higher sensitivity of FISF compared to ISF may be explained by the fact that ET derived from global S curve reflects only part of the ejection phase whereas FISF describes presence of ventricular discoordination in the entire ejection phase. Acknowledgement/Funding Supported by Ministry of Health of the Czech Republic, grant nr. 15-31398A. All rights reserved.