scholarly journals Layered shock-resistant element parts shape change process selection and modeling

2021 ◽  
Author(s):  
Roman Arhat ◽  
Serhiy Shlyk ◽  
Viktor Shchetynin ◽  
D. Moloshtan ◽  
Volodymyr Drahobetskyi ◽  
...  
Keyword(s):  
Plastic Material ◽  
Shape Change ◽  
Outer Part ◽  
Back Surface ◽  
Process Selection ◽  
Protected Object ◽  
Develop Technology ◽  
Stiff Material ◽  
Absorbing Layer ◽  
The Impact

An impact-resistant layered element consisting of two outer layers from highly rigid material and an inner layer from viscoelastic material has been developed. The item reduces the barring effect on the protected object. The design peculiarity is that the outer part has a bend with a deflection arrow within 10… 15 thicknesses, and has a connection of the outer layers from high-stiff material on opposite edges with staples from plastic material, which during plastic deformation flows into the edge holes coaxially in the outer layers, on the inner side of the impact-resistant element is attached a shock-absorbing layer from elastic foamed polymeric material, the back surface of which corresponds to the surface of the protected object. For the parts manufacture it has been developed bending sheet parts method in which the bending the part shelves with a bending element with their subsequent straightening. The aim is to increase the process productivity and the geometric dimensions’ accuracy of the part. Modeling the process of parts spontaneous forming "Impact-resistant element upper sheet" on the reverse and direct schemes is performed by the finite element method in the AnSYS / AutoDYN system. The study purpose is to develop technology and modeling the process of the impact-resistant element sheet parts deformation.

Effect of Particle Impact Velocity on Cone Crack Shape in Ceramic Material

2005 ◽  
Vol 297-300 ◽  
pp. 1321-1326 ◽  
Author(s):  
Sang Yeob Oh ◽  
Hyung Seop Shin
Keyword(s):  
Impact Velocity ◽  
Computational Simulation ◽  
Back Surface ◽  
Particle Impact ◽  
Cone Crack ◽  
Crack Shape ◽  
The Impact ◽  
Particle Impact Velocity ◽  
Sic Particle ◽  
Ring Cracks

The damage behaviors induced in a SiC by a spherical particle impact having a different material and size were investigated. Especially, the influence of the impact velocity of a particle on the cone crack shape developed was mainly discussed. The damage induced by a particle impact was different depending on the material and the size of a particle. The ring cracks on the surface of the specimen were multiplied by increasing the impact velocity of a particle. The steel particle impact produced the larger ring cracks than that of the SiC particle. In the case of the high velocity impact of the SiC particle, the radial cracks were generated due to the inelastic deformation at the impact site. In the case of the larger particle impact, the morphology of the damages developed were similar to the case of the smaller particle one, but a percussion cone was formed from the back surface of the specimen when the impact velocity exceeded a critical value. The zenithal angle of the cone cracks developed into the SiC decreased monotonically as the particle impact velocity increased. The size and material of a particle influenced more or less on the extent of the cone crack shape. An empirical equation was obtained as a function of impact velocity of the particle, based on the quasi-static zenithal angle of the cone crack. This equation will be helpful to the computational simulation of the residual strength in ceramic components damaged by the particle impact.

Mechanical Event Simulation of Drop Testing for Toy Product

2006 ◽  
Vol 532-533 ◽  
pp. 993-996
Author(s):  
Anthony Yee Kai Yam ◽  
Kai Leung Yung ◽  
Chi Wo Lam
Keyword(s):  
Material Properties ◽  
Impact Analysis ◽  
Plastic Material ◽  
Free Fall ◽  
Drop Impact ◽  
Local Analysis ◽  
Element Analysis ◽  
Event Simulation ◽  
Long Time ◽  
The Impact

Toys that are free from drop failures normally take a long time to develop. It is often time and cost consuming after the production tooling is built to detect drop test failure. This paper introduces a new drop testing analysis method for Toys. The method uses a simple approach with a local analysis that based on the linear and non linear finite element analysis. Modeling and transient drop analysis of a pre-school toy is used as a case study to demonstrate the method. The impact analysis of the product hitting the solid concrete floor after a free fall is presented. The analysis focuses on the deformation of the housing for a product with electronic circuit and mechanical mechanism inside. Experimental data has been obtained for drop simulation of the housing and its correlation with the plastic material properties. The stress and strain of the housing during drop impact tests are noted. The effects of the material properties to the housing deflection under drop/impact shock have been investigated. Numerical results are compared with experimental results to validate the method.

scholarly journals ANALYSIS OF EXPERIENCE IN THE APPLICATION OF MISSILE LAUNCH DETECTION SYSTEMS

2021 ◽  
pp. 118-129
Author(s):  
A. Pinchuk ◽  
M. Garbuz ◽  
P. Zeleny ◽  
D. Harnets ◽  
D. Ivanov
Keyword(s):  
High Speed ◽  
Armed Forces ◽  
The United States ◽  
Armed Conflicts ◽  
Desert Storm ◽  
Detection Systems ◽  
The Face ◽  
Protected Object ◽  
Conducting Research ◽  
The Impact

Analysis of combat losses of aircraft in local armed conflicts in recent decades shows that most cases of aircraft hits are related to the impact of guided surface-to-air and air-to-air missiles equipped with homing warheads. The use of modern guided missiles equipped with homing warheads is one of the main threats to aircraft of various types. This is due to the fact that modern guided missiles are characterized by high speed, maneuverability, accuracy of aiming and difficulty of detection. Solving the problem of protecting aircraft from guided missiles consists of several stages: detection of missile launch; confirmation that the detected missile is heading directly toward the protected object; missile identification and decision-making on the most effective countermeasure system employment. At present, there are no missile launch detection systems that guarantee a 100% probability of threat detection, but an analysis of aviation combat losses in local armed conflicts in recent decades convincingly shows that the number of combat losses of aircraft equipped with such systems is much lower than those in which missile launch detection is carried out visually. For example, most of the Soviet Union's losses during the war in Afghanistan and the United States‟ losses during Operation “Desert Storm” in Iraq were related to the use of portable anti-aircraft missile systems, which missiles were equipped with infrared homing warheads. Realizing the scale of the threat posed by such missiles, most of the world's leading countries have significantly increased the expenses on development new or improvement existing countermeasures. As a result, the aggregate losses of coalition forces in Iraq, Afghanistan and Syria since 2001 clearly suggest that these costs have paid off, with losses from the use of portable anti-aircraft missile systems significantly reduced, while the total number of combat sorties increased. Therefore, in the face of all the challenges and threats posed to Ukraine due to the aggressive actions of the Russian Federation, conducting research in the interests of aviation of the Armed Forces of Ukraine to improve the effectiveness of missile detection systems for ensuring timely detection of threats, warning of aircraft crew and activation in the automatic mode the means of countermeasures is as relevant as ever.

Abundance and size of European lobsters (Homarus gammarus) and brown crabs (Cancer pagurus) inside and outside the Kåvra lobster reserve (west coast of Sweden)

Crustaceana ◽  
2020 ◽  
Vol 93 (2) ◽  
pp. 157-169
Author(s):  
Vidar Øresland ◽  
Gert Oxby ◽  
Fredrik Oxby
Keyword(s):  
Size Distribution ◽  
Relative Abundance ◽  
West Coast ◽  
Outer Part ◽  
Swedish West Coast ◽  
Offshore Area ◽  
Homarus Gammarus ◽  
Cancer Pagurus ◽  
And Migration ◽  
The Impact

Abstract The common method of using lobster-pot catch data for investigating relative abundance, sex and size distribution has serious disadvantages. This study estimates relative abundance and size of the European lobster Homarus gammarus and the brown crab Cancer pagurus using scuba diving techniques. The study areas were the Kåvra lobster reserve (Kåvra) on the Swedish west coast and three very different nearby areas where fishing for crustaceans is allowed: Gullmarsfjorden; the archipelago; and the offshore area. A total of 167 lobsters and 337 brown crabs were observed during 33 scuba dives (each 30 minutes long) in 2018-2019. The estimated mean abundance of lobsters was three to fifteen times as high at Kåvra in comparison with the other three areas (all exact showing that the statistical populations were distinct in comparison with Kåvra; Wilcoxon-Mann-Whitney Test). Dive sites in the outer part of the offshore area had the lowest abundance of lobsters although they had seemingly good lobster habitats and low fishing intensity. Large lobsters with a carapace length of ⩾15 cm were found only at Kåvra where they made up 24% of the lobsters. The proportion of large lobsters inside Kåvra continues to increase after 30 years of protection. Together, this emphasizes the impact of fishing on lobster abundance and size distribution, and indicates that limited recruitment and migration might possibly affect offshore lobster “sub populations”. Kåvra was the only area where the abundance of lobsters exceeded the abundance of brown crabs (). However, the abundance of brown crabs at Kåvra was as low as in Gullmarsfjorden () where fishing for crabs is allowed. Possible complex lobster/brown crab interactions together with other factors that might explain the low abundance of the protected brown crab at Kåvra, need to be investigated further.

Failure Analysis of a Ruptured Final Reheat Tube

2007 ◽  
Author(s):  
S. M. French
Keyword(s):  
Shock Wave ◽  
Charpy Impact ◽  
Charpy Impact Test ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Back Surface ◽  
Damage Area ◽  
Local Overheating ◽  
Spalling Failure ◽  
The Impact

Two damaged final reheat tubes from a 30 year old supercritical unit were submitted to the laboratory for evaluation following the discovering of a failure of one of the tubes after deslagging operations; a third, dented tube was left in service. The 304H stainless steel tubes were installed in 1990 when the reheater was replaced. The bulk microstructure of both tubes shows evidence of sensitization, which is not unusual given this application (reheater). The failed tube appears to be an intergranular separation that started either subsurface or at the ID, propagating to the OD surface. The sensitization of the steel apparently made the material susceptible to corrosion as well as significantly reduced the impact strength of the material to 10–15% of its estimated original level (verified by Charpy impact test). Examination of the dented tube (#101A) showed a subsurface plane of damage some 30 mils from the ID surface, running parallel to the surface. The damage consisted of intergranular separation, caused by the impact loading event, and referred to in the literature as an “attached spalling failure”. Spalling failures occur when the shock wave is reflected from the back surface (the ID surface of the tube), interacting with the incident shock wave as a stress wave. When the magnitude of this tensile stress exceeds the inherent strength of the material, failure occurs. The overall area of the attached spalling failure is being investigated; the concern there is if it is exceptionally large, it may provide a thermal barrier to heat transfer from the OD to the ID and result in a local overheating failure. Within the metallographic sample, however, the damage area was quite small and therefore did not appear to be an immediate issue. The long-term suitability of tube 105A, which remains in service with a dent induced by the same deslagging process that damaged tubes 101A and 103A, is doubtful and should be addressed during the Fall 2006 boiler overhaul. For the shortterm, the assumption was made that cracking due to the deslagging impact would be oriented similar to non-failed tube and extension of these fissures to failure between Spring 2006 and the Fall outage is not expected.

scholarly journals Characterization of Impacts of Elastic-plastic Spheres

2020 ◽  
Vol 64 (2) ◽  
pp. 165-171
Author(s):  
Bence Szabó ◽  
Attila Kossa
Keyword(s):  
Plastic Material ◽  
Analytical Models ◽  
Material Models ◽  
Elastic Plastic ◽  
Analytical Functions ◽  
Elastic Plastic Material ◽  
Explicit Dynamic ◽  
The Impact ◽  
The Given

This work presents explicit dynamic finite element simulations of various impacts of elastic-plastic solid spheres with flat walls. Different  analytical models describing the mechanics of the impact phenomenon are also presented. Elastic and elastic-plastic material models for the sphere and the wall are considered during the analyses. The applicability of these different models is demonstrated and their accuracies are investigated. Closed-form analytical functions are proposed to describe the relationship between the initial velocity of the sphere and the investigated contact characteristics for the given material models. Analysis is carried out to study the effect of the friction coefficient as well as the angle of impact for various cases.

Introduction

2017 ◽  
Author(s):  
Ellen F. Steinberg ◽  
Jack H. Prost
Keyword(s):  
Large Scale ◽  
Shape Change ◽  
The State ◽  
Food Preparation ◽  
Rural And Urban ◽  
Production And Consumption ◽  
Economic Practices ◽  
The Impact

This introductory chapter provides an overview of the book's main themes. This book explores the state, shape, change, and evolution of Midwestern Jewish cuisine through time. It tracks geographically based culinary recipes and changes made to them through time by presenting and analyzing ones from Midwestern Jewish sources, both kosher and non-kosher. It documents the availability of fruits, vegetables, and other comestibles throughout the Midwest that impacted how and what Jews cooked; and considers the effect of improved preservation and transportation on rural and urban Jewish foodways. Then, it examines the impact on Jewish foodways—the cultural, social, and economic practices relating to the production and consumption of food—of large-scale immigration, relocation, and Americanization efforts during the nineteenth and early twentieth centuries, paying special attention to the attempts of social and culinary reformers to modify traditional Jewish food preparation and ingredients.

Degradation of nanoplastics in aquatic environments: reactivity and impact on dissolved organic carbon

2020 ◽  
Author(s):  
Angelica Bianco ◽  
Fabrizio Sordello ◽  
Mikael Ehn ◽  
Davide Vione ◽  
Monica Passananti
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Aqueous Phase ◽  
Surface Waters ◽  
High Resolution Mass Spectrometry ◽  
Degradation Products ◽  
Plastic Material ◽  
Environmental Models ◽  
Reactivity Constant ◽  
The Impact

<p>The large production of plastic material (PlasticsEurope, 2019), together with the mishandling of plastic waste, has resulted in ubiquitous plastic pollution, which now reaches even the most remote areas of the Earth (Allen et al., 2019; Bergmann et al., 2019). Plastics undergo a slow process of erosion in the environment that decreases their size: microplastics (MPs) and nanoplastics (NPs) have diameters between 1 µm and 5 mm and lower than 1 µm, respectively (Frias and Nash, 2019).</p><p>The occurrence, transformation and fate of MPs and NPs in the environment are still unclear. Therefore, the objective of this work is to better understand the reactivity of NPs using an aqueous suspension of polystyrene NPs (PS-NPs) as a proxy, in the presence of sunlight and chemicals oxidants. The results obtained are relevant to both the atmospheric aqueous phase, such as cloud and fog droplets, and surface waters. We investigated the reactivity of PS-NPs with light and with two important oxidants in the environment: ozone (O<sub>3</sub>) and hydroxyl radicals (<sup>•</sup>OH). The adsorption of ozone (O<sub>3</sub>) on PS-NPs is investigated, showing a significant O<sub>3</sub> uptake. Moreover, for the first time, a reactivity constant with <sup>•</sup>OH is determined. We found a linear correlation between the kinetic constants measured for three different sizes of PS-NPs and the surface exposed by the particles. Degradation products (short chain carboxylic acids and aromatic compounds), obtained by direct and <sup>•</sup>OH-mediated photolysis of PS-NPs suspensions, are identified by high-resolution mass spectrometry. Irradiation of a PS-NPs suspension under natural sunlight for 1 year has shown the formation of formic acid and organic compounds similar to those found in riverine and cloud dissolved organic matter.</p><p>This work is crucial to assess the impact of NPs abiotic degradation in atmospheric and surface waters; indeed, the reactivity constant and the degradation products can be implemented in environmental models to estimate the contribution of NPs degradation to the natural dissolved organic matter in the aqueous phase. A preliminary simulation using APEX (Aqueous Photochemistry of Environmentally occurring Xenobiotics) (Bodrato and Vione, 2014) model shows that in NPs-polluted environments (10<sup>9</sup> particles mL<sup>-1</sup>) there is potential for NPs to significantly scavenge <sup>•</sup>OH, if the content of natural organic matter is not too high, as observed for surface and cloud water.</p><p>Allen, S., et al., 2019.  Nat. Geosci. 12, 339–344. https://doi.org/10.1038/s41561-019-0335-5<br>Bergmann, et al., 2019.  Sci. Adv. 5, eaax1157. https://doi.org/10.1126/sciadv.aax1157<br>Bodrato, M., Vione, D., 2014. Environ. Sci.: Processes Impacts 16, 732–740. https://doi.org/10.1039/C3EM00541K<br>Frias, J., Nash, R., 2019. Mar. Pollut. Bull. 138, 145–147. https://doi.org/10.1016/j.marpolbul.2018.11.022</p>

The brittle fracture of solids by liquid impact, by solid impact, and by shock

1964 ◽  
Vol 282 (1390) ◽  
pp. 331-352 ◽  
Keyword(s):  
Surface Wave ◽  
High Velocity ◽  
High Speed ◽  
Turbine Blades ◽  
Explosive Loading ◽  
Back Surface ◽  
High Speed Photography ◽  
Liquid Mass ◽  
Liquid Impact ◽  
The Impact

The type of stress pulse produced when a liquid mass strikes a solid at high velocity is first examined. Compressible behaviour, giving rise to a sharp peak of pressure, is found to occur in the initial stages of the impact. The duration of this peak depends on the dimensions and impact velocity of the liquid mass, and also on the compressible wave velocity for the liquid. A comparison is made with pulses produced by solid/solid impact and by the detonation of small quantities of explosive. Both the high-speed liquid impact and the explosive loading give intense pulses of duration only a few microseconds. A solid/solid impact has, by comparison, a much longer impact time of the order of hundreds of microseconds. The fracture of glasses and hard polymers using these three types of loading is described. The development of fracture is followed by high-speed photography. Differences in the modes of fracture are attributed to variations in the shape and duration of the applied stress pulses. Short circumferential fractures produced around the loaded area in liquid impact and explosive loading are shown to be initiated by the Rayleigh surface wave at points where flaws existed. More complex fracture patterns on the front surfaces of plates are due to the reinforcement of the surface wave with components of stress waves reflected from the back surface. A combination of impact loading and etching makes it possible to investigate the distribution and depths of flaws, their role in the fracture process, and the effect which etching has upon them. The observation on the deformation produced in solids by liquid impact has practical significance in the problem of supersonic aircraft flying through rain and in the erosion of turbine blades moving at high velocity through wet steam.

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