scholarly journals Analysis of generic reentry vehicle flight dynamics

2018 ◽  
Author(s):  
Yu. Metsker ◽  
K. Weinand ◽  
G. Geulen ◽  
O. J. Haidn
Keyword(s):  
Mechanical Properties ◽  
Geometrical Shape ◽  
Impact Point ◽  
Flight Trajectory ◽  
Body Dimensions ◽  
Reentry Vehicle ◽  
Aerodynamic Properties ◽  
Medium Range ◽  
Precise Prediction ◽  
Reliable Methods

The knowledge of reentry vehicles (RV) flight characteristics regarding geometrical shape, dimensions, and mechanical properties is essential for precise prediction of their flight trajectory, impact point, and possible deviations according to simulation uncertainties. The flight characteristic estimations of existing RV require both body dimensions and mechanical properties of the objects. Due to comparatively simple and reliable methods of specifying the vehicle outer dimensions, e. g., photos and videomaterials, the estimation of mechanical properties is a subject of higher uncertainties. Within this study, a generic medium range ballistic missile (MRBM) RV was examined for several modifications such as center of gravity (CoG) position, weight moment of inertia, and initial reentry flight states. Combinations of these variables with constant aerodynamic properties for maximal lateral accelerations will be determined. Basing on these, potential evasion maneuver capabilities of the RV will be described.

Evolution of Pipe Properties During Reel-Lay Process: Experimental Characterisation and Finite Element Modelling

2005 ◽  
Author(s):  
Michae¨l Martinez ◽  
George Brown
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Computation Time ◽  
Material Model ◽  
Point Of View ◽  
Fatigue Properties ◽  
Geometrical Shape ◽  
Element Analysis ◽  
New Model ◽  
Tension And Compression

The development of finite element analysis, in terms of simulation power and theoretical model accuracy, enables one to understand and simulate industrial processes more precisely, especially those involving non linear behaviour and analysis. Reeled pipe technology is one of these, and has a lot to gain from this increasing efficiency. In the reel-lay process the pipe is first reeled onto a drum on a vessel for transportation. During offshore installation the pipe is unreeled, straightened and deployed into the sea. During the process, the pipe is fully and cyclically plastified. Plastification modifies the pipe properties, which is not by itself detrimental but should be understood by the designer. Pipe properties are affected in three ways: geometrical shape – reeling and straightening induce some residual ovalisation; mechanical properties – yield stress, hardening slope, isotropy are modified; and fatigue properties. Technip and IFP have studied these property evolutions for many years, both from an experimental and a numerical point of view. The present paper discusses the first two points. A wide experimental programme has been performed. Full scale pipes were reeled and straightened on a bending rig device especially built for that purpose. Pipe ovalisation was monitored through the whole process. Pipe mechanical properties were also fully characterised in the pipe axial, hoop and thickness directions, both in tension and compression, before and after reeling process. Extruded and UOE pipes were tested and characterised. Pipe initial properties are dependent on the manufacturing process but they are modified by the reeling process. Reeling induces some anisotropy that cannot be properly accounted for by usual plasticity models. Finite element simulations with Abaqus software, using the material behaviour of unreeled pipe, underestimate stiffness evolution in the hoop direction and overestimate ovalisation induced by the reeling process. Anisotropy has indeed a great effect on ovalisation that results from an interaction between axial and hoop loading. Hardening is also a key parameter. A new plasticity model has been written in an Abaqus User Material Model, known as UMAT. The new model is based on an anisotropic Hill criterion and special attention is paid to the hardening. This new model reduces by more than two the error on ovality estimation, and gives a realistic prediction of material anisotropy evolution through the process. Although, the tuning of the model coefficients is more complex than for usual models, its use is quite straightforward and does not increase computation time.

Analysis and Numerical Simulation of the Mechanical Performance of FDM Samples With Variable Infill Values

2017 ◽  
Author(s):  
Steffany N. Cerda-Avila ◽  
Hugo I. Medellín-Castillo ◽  
Dirk F. de Lange
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Prediction Models ◽  
Mechanical Performance ◽  
Numerical Models ◽  
Research Work ◽  
Tensile Tests ◽  
Geometrical Shape ◽  
Cad System ◽  
Fem Method

The prediction of the mechanical properties of AM parts is very important in order to design and fabricate parts not only of any geometrical shape but also with variable or customized mechanical properties. A limited number of investigations have focused on the analysis and prediction of the mechanical properties of AM parts using theoretical and numerical approaches such as the Finite Element Method (FEM); nevertheless, their results have been not accurate yet. Thus, more research work is needed in order to develop reliable prediction models able to estimate the mechanical performance of AM parts before fabrication. In this paper the analysis and numerical simulation of the mechanical performance of FDM samples with variable infill values is presented. The aim is to predict the mechanical performance of FDM components using numerical models. Thus, several standard tensile test specimens were fabricated in an FDM system using different infill values, a constant layer thickness, one shell perimeter, and PLA material. These samples were measured and modelled in a CAD system before performing the experimental tensile tests. Numerical models and simulations based on the FEM method were then developed and carried out in order to predict the structural performance of the specimens. Finally the experimental and numerical results were compared and conclusions drawn.

scholarly journals An evaluation of the physical, dynamic and aerodynamic properties of olives

2019 ◽  
Vol 65 (No. 2) ◽  
pp. 48-55
Author(s):  
Abbas Akbarnia ◽  
Mahdi Rashvand
Keyword(s):  
Mechanical Properties ◽  
Physical And Mechanical Properties ◽  
Agricultural Products ◽  
Test Material ◽  
Mechanical Sensitivity ◽  
Aerodynamic Properties ◽  
Sphericity Index ◽  
The Mean ◽  
Power And Energy

The determination of the physical and mechanical properties of agricultural products has always been considered as the basis for the design and fabrication of transmission, grading, and processing equipment for agricultural products. Due to the increasing production of olives and the foreign exchange earnings from its trade, the mechanisation of harvesting and processing operations is inevitable. Therefore, the aim of this study was to evaluate the physical, dynamic and aerodynamic properties of olive species in order to design and fabricate an olive oiling machine. In this research, four species of olives, namely the Manzanilla, Kalamata, Fishemi, and Oily, were used. The physical properties of the samples were completely different. The mean dimensions of the Manzanilla species are the largest and the Oily is smallest and were the inverse in relation to the sphericity index. To determine the mechanical properties of the samples, the test material was used at a speed of 8 mm·min–1. The results showed that the maximum and minimum power and energy of rupture were allocated to the Manzanilla and Oily species, respectively. The Oily samples have the most mechanical sensitivity when compared to the other samples. The aerodynamic properties of the olive species were measured using a wind tunnel. The highest velocity and drag coefficient were assigned to the Oily sample and the lowest values were assigned to the Kalamata sample.

Sensitivity Study of Surface Curvature in Characterisation of Cartilage Mechanical Properties

2013 ◽  
Vol 393 ◽  
pp. 941-946
Author(s):  
Mohd Juzaila Abd Latif ◽  
Noor Rizan Adzwa Ismail ◽  
Roszaidi Ramlan ◽  
Jamaluddin Mahmud ◽  
Mohammed Rafiq Abdul Kadir
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Elastic Modulus ◽  
Sensitivity Study ◽  
Surface Curvature ◽  
Finite Element Models ◽  
Geometrical Shape ◽  
Computational Studies ◽  
Synovial Joint ◽  
Cartilage Surface

The mechanical properties of articular cartilage serve as important measures of tissue function or degeneration, and are known to change significantly with asteoarthritis. In previous computational studies, the cartilage surface of axisymmetric models was assumed to be flat in order to evaluate the cartilage behaviour. This assumption was inappropriate since the synovial joint possessed curvature geometrical shape and may contribute to the inaccurate in characterising the cartilage properties. Therefore, this study aims to examine the sensitivity of cartilage surface curvature of characterized cartilage biphasic properties using a combination of experimental and computational methods. Axisymmetric biphasic poroelastic finite element models were generated to measure cartilage surface radius and thickness. Based on the results, the smaller cartilage surface of 20 mm radius produced higher difference of the characterised properties where its generate 9% difference in the permeability and 5% difference in the elastic modulus, compared to the flat cartilage. Based on these results, it may indicate that the cartilage curvature will affect the characterised cartilage biphasic properties of elastic modulus and permeability.

scholarly journals A REVIEW ON THE ENGINEERING PROPERTIES OF SOYBEAN TO SUPPORT THE TOFU AGRO-INDUSTRIAL MACHINERY DEVELOPMENT AND IMPORTANT HIGHLIGHTS

AGROINTEK ◽  
2021 ◽  
Vol 15 (3) ◽  
pp. 921-931
Author(s):  
Agustami Sitorus ◽  
Devianti Devianti ◽  
Ramayanty Bulan
Keyword(s):  
Mechanical Properties ◽  
Moisture Content ◽  
Physical Properties ◽  
Angle Of Repose ◽  
Engineering Properties ◽  
Future Research ◽  
Aerodynamic Properties ◽  
Study Results ◽  
Scientific Papers ◽  
Soybean Processing

The physical and mechanical properties of the material to be processed are fundamental and continue to be a challenge for researchers to design a machine appropriately. Studies of the soybean engineering properties have not been widely highlighted and reviewed. This makes researchers and engineers of soybean processing machines still have to search through experimentation or read deeply through scientific papers before applying it. Therefore, this paper presents highlights and reviews of studies related to the measurement and modelling of soybean engineering properties. The objective is to study methodologies uses and identify future research directions to get a result in more accuracy. Several papers are searched from various search engines for scientific articles that are available online. Some keywords and a combination of keywords used in the search process are “physical properties”, “mechanical properties”, “soybean grains” and “moisture-dependent”. The results show that ten scientific papers are strictly related to the measurement and modelling of the engineering properties of soybean. In general, the documents found were in the period 1993 to 2012. The research paper investigated the engineering properties of soybean in the moisture content ranges from 6.7% (d.b.) to 49.7% (d.b.). The widely studied physical properties are diameter, surface area, roundness, the weight of 1000 soybeans, bulk density, and true density associated with moisture content. Mechanical parameters investigated include friction coefficient, angle of repose, terminal velocity, angle of internal friction, rupture force, and rupture energy. On the one hand, some of the engineering properties of soybeans that have not yet been discovered are thermal, optical, and aerodynamic properties. On the other hand, the effect of soaking and blanching on changes in the engineering properties of soybean (physical, mechanical, thermal, optical, and aerodynamic) has not been done in-depth. Besides that, most of the soybean processing agro-industry requires engineering properties of soybean to be able to design their machines more precisely. One of the agro-industries that need data on the study results of the nature of engineering with these treatments is the tofu processing industry.

scholarly journals Anisotropic Plastic Behavior of Additively Manufactured PH1 Steel

2021 ◽  
Author(s):  
Wenqi Liu ◽  
Zinan Li ◽  
Sven Bossuyt ◽  
Antti Forsström ◽  
Zaiqing Que ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Thermal History ◽  
Deformation Behavior ◽  
Uniaxial Tensile ◽  
Plastic Behavior ◽  
Geometrical Shape ◽  
Anisotropic Plasticity ◽  
Plastic Deformation Behavior ◽  
Anisotropic Plastic

Metals made by additive manufacturing (AM) have intensely augmented over the past decade for customizing complex structured products in the aerospace industry, automotive, and biomedical engineering. However, for AM fabricated steels, the correlation between the microstructure and mechanical properties is yet a challenging task with limited reports. To realize optimization and material design during the AM process, it is imperative to understand the influence of the microstructural features on the mechanical properties of AM fabricated steels. In the present study, three material blocks with 120×25×15 mm3 dimensions are produced from PH1 steel powder using powder bed fusion (PBF) technology to investigate the anisotropic plastic deformation behavior arising from the manufacturing process. Despite being identical in geometrical shape, the manufactured blocks are designed distinguishingly with various coordinate transformations, i.e. alternating the orientation of the block in the building direction (z) and the substrate plate (x, y). Uniaxial tensile tests are performed along the length direction of each specimen to characterize the anisotropic plastic deformation behavior. The distinctly anisotropic plasticity behavior in terms of strength and ductility are observed in the AM PH1 steel, which is explained by their varied microstructure affected by the thermal history of blocks. It could also be revealed that the thermal history in the AM blocks is influenced by the block geometry even though the same process parameters are employed.

scholarly journals STUDIES OF FLIGHT TRAJECTORY OPTIMIZATION AND THE WORKLOADS OF AIR TRAFFIC CONTROL OFFICERS

2019 ◽  
Vol 10 (1) ◽  
pp. 70-86
Author(s):  
Weiyang Sun ◽  
Wei-Chuen Wallace Ong ◽  
Zhao-Wei Zhong
Keyword(s):  
Standard Deviation ◽  
Southeast Asia ◽  
Case Studies ◽  
Traffic Control ◽  
Trajectory Optimization ◽  
Air Traffic Control ◽  
Air Traffic ◽  
Flight Trajectory ◽  
Fuel Savings ◽  
Medium Range

We studied a methodology for flight trajectory optimization, and also the workloads of air traffic control officers (ATCOs). Case studies were conducted through simulations for flight trajectory optimization. The aircraft model was A320-200s, which is pre-dominantly utilized in Southeast Asia for short to medium range flights. Fuel savings were computed for selected routes, and were compared with that of existing operations and flights simulations, which revealed significant fuel savings. The research also determined the coefficients of ATCOs’ workloads and demonstrated dynamic sectorization in selected airspace of Southeast Asia. It was found that dynamic sectorization was more efficient than static sectorization in balancing the workloads of ATCOs, reducing the standard deviation by 50% and the balance of workloads among sectors by 12.9%.

Thermoelastic Analysis of an Heterogeneous Orthotropic Nose Cap for a Hypersonic Vehicle

2011 ◽  
Vol 338 ◽  
pp. 325-334
Author(s):  
Xing Hua Cheng ◽  
Tao Yang ◽  
Zhong Dong Chang
Keyword(s):  
Mechanical Properties ◽  
Thermal Stress ◽  
Equivalent Stress ◽  
Hypersonic Vehicle ◽  
Flight Trajectory ◽  
Thermal Pressure ◽  
Thermoelastic Analysis

Considering xz plane heterogeneous mechanical properties and thermal-pressure loads, thermoelastic analysis is applied on orthotropic nose cap of a hypersonic vehicle in the flight trajectory. The results show that the thermal-stress of sphere section presents annular, the Mises equivalent stress is of periodicity of 90° in tail so obviously that a reasonable connection is important. Finally, two connections, bolted and plug connection, are considered to relax the overnice tail constrains, and the results show that the plug connection is reasonable for the hypersonic heterogeneous orthotropic nose cap

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