scholarly journals Optimal Design and Testing of a Thermoplastic Pressurized Passenger Door Manufactured Using Thermoforming

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3394
Author(s):  
Roman Růžek ◽  
Josef Křena ◽  
Radek Doubrava ◽  
Josef Tkadlec ◽  
Martin Kadlec ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Impact Damage ◽  
Research Work ◽  
Variable Cross Section ◽  
Mechanical Tests ◽  
Point Of View ◽  
Topological Optimization ◽  
Variable Cross ◽  
Thermoplastic Resin ◽  
Significant Difference

The present paper documents and discusses research work associated with a newly designed passenger door structure demonstrator. The composite structure was manufactured from carbon-fiber-reinforced thermoplastic resin. A composite frame with a variable cross-section was designed, optimized, and fabricated using thermoforming technology. Both numerical simulations and experiments supported structural verification according to the damage tolerance philosophy; i.e., impact damage is presented. The Tsai-Wu and maximal stress criteria were used for damage analysis of the composite parts. Topological optimization of the metal hinges from the point of view of weight reduction was used. All expected parameters and proposed requirements of the mechanical properties were proved and completed. The door panel showed an expected numerically evaluated residual strength (ultimate structure load) as well as meeting airworthiness requirements. No impact damage propagation in the composite parts was observed during mechanical tests, even though visible impact damage was introduced into the structure. No significant difference between the numerical simulations and the experimentally measured total deformation was observed. Repeated deformation measurements during fatigue showed a nonlinear structure behavior. This can be attributed to the relaxation of thermoplastics.

scholarly journals Theoretical and Experimental Research of The Stability of The Eccentrically Loaded Steel Columns with Variable Cross–Section

2018 ◽  
Vol 7 (3.2) ◽  
pp. 458
Author(s):  
Gennady Trusov ◽  
Vladimir Ruban
Keyword(s):  
Cross Section ◽  
Research Work ◽  
Variable Cross Section ◽  
Suggested Method ◽  
National Standards ◽  
Discrete Models ◽  
Practical Calculation ◽  
Variable Cross ◽  
Cross Sectional ◽  
Steel Columns

The article deals with the problem of determining the ultimate load for the eccentrically loaded steel columns with variable-cross section.The purpose of the research work is to offer an evaluation technique and practical calculation of load-bearing ability of the beam-columns with variable cross-section on the basis of numerical research, which will allow to consider the true form of element deflection curve, the effect of cross-section form, physical nonlinearity of the material, and variety of element boundary conditions. The distinctive characteristic of the suggested method is usage of the discrete models for cross-sectional parts, for the true stress-strain curves of the materials, and for the other input data. The method was tested and the results were compared to known theoretical solutions and national standards. To establish the reliability of the developed method, the experimental study of steel columns with variable cross-section was conducted. The suggested method allows to obtain column curves tables of lowering coefficients for these elements, that can be used in practice of civil engineering, and are convenient with national standards and Eurocode. 

scholarly journals Longitudinal-transverse thermal- force bending and stability layered inhomogeneous profiled rod

2021 ◽  
Vol 2131 (2) ◽  
pp. 022067
Author(s):  
A Mishchenko
Keyword(s):  
Cross Section ◽  
Variable Cross Section ◽  
Unstable State ◽  
Variable Cross ◽  
Normal Stresses ◽  
Initial State ◽  
Resistance Level ◽  
Initial Shape ◽  
Longitudinal Load ◽  
Significant Difference

Abstract The solution to the problem of the stress-strain state of an inhomogeneous profiled rod is based on the use of nonlinear equilibrium conditions and physical relations of a layered thermo elastic thin rod. A differential equation of bifurcation inhomogeneous rod stability of variable cross-section is obtained. The equation has variable functional coefficients. In the initial state, the rod is subjected to bending with the implementation of one of the asymmetric shapes. The critical state occurs under the action of a longitudinal load corresponding to one of the lowest symmetrical shapes, orthogonal to the initial shape. In the first series, numerical calculations of an inhomogeneous I-rod with a variable cross section height are performed. Shelves and wall I-rod are made of steel, aluminum and titanium alloys. The graphs of maximum deflection and normal stresses acting at the calculate points at the boundaries of the layers are plotted depending on the longitudinal load at the given levels of transverse loads and thermal field. A significant influence of the rod physical structure, the profiling its form and the factor of nonlinearity of static relations on the stress fields has been established. A homogeneous temperature field with a nominal value of 80°C creates fields of self-balanced stresses in an inhomogeneous rod. The components of normal stresses in this case reach 20-40% of the materials permissible resistance level. The presence of rod parts with a significant difference in the coefficients of thermal expansion in the composition enhances this effect. In the second, the stability analysis of an inhomogeneous I-rod with a variable width cross section was performed. The transition of the initial S-shaped bend to an unstable state is shown.

scholarly journals Evaluation of Novel Ornamental Cladding Resistance, Comprised of GFRP Waste and Polyester Binder, within an Acid Environment

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 448
Author(s):  
Emilia Sabău ◽  
Paul Bere ◽  
Mărioara Moldovan ◽  
Ioan Petean ◽  
Cristina Miron-Borzan
Keyword(s):  
Surface Roughness ◽  
Polarized Light ◽  
Mechanical Tests ◽  
Point Of View ◽  
Chemical Degradation ◽  
Chemical Attack ◽  
Significant Difference ◽  
Acid Environment ◽  
High Pollution ◽  
Building Walls

The paper presents the manufacturing technology for a material obtained from glass fiber waste, quartz sand, and polyester binder, used for ornamental building plates. The composite has a cover surface that ensures protection of the material from environment attacks and a structural material that can be subjected to chemical degradation. The mechanical properties of the obtained material were experimentally investigated through compressive mechanical tests. To observe the material’s behavior in contact with external agents (rain or acid rain, due to environmental pollution), analyses were performed in laboratory conditions. An investigation on the effects of chemical attack substances was conducted. SEM and macroscopic analyses were performed, and the surface roughness was determined for each sample area. The obtained results were statistically analyzed and showed that there is no significant difference between the surface roughness for treated and untreated samples. Furthermore, the surfaces were analyzed by X-ray diffraction and mineralogical optical microscopy in polarized light with crossed nicols. It was observed that rainwater does not affect the plate structure even if the plates are used in high-pollution environments. The material is suitable for exterior building walls from the point of view of chemical attack and resistance.

Sound Absorption Analysis of Micro Perforated Panel with Ladder Change Type Cross Section

2015 ◽  
Vol 1101 ◽  
pp. 379-384
Author(s):  
Zhi Hui Ma ◽  
Xian Hui Li ◽  
Xiao Ling Gai ◽  
Jun Juan Zhao ◽  
Bin Zhang
Keyword(s):  
Numerical Simulations ◽  
Cross Section ◽  
Sound Absorption ◽  
Variable Cross Section ◽  
Double Layers ◽  
Variable Cross ◽  
Absorption Model ◽  
Absorption Analysis ◽  
Change Type ◽  
Good Agreement

A kind of variable cross section micro perforated panel (MPP) with ladder micro porous is introduced in this paper. Based on the double layers MPP theory and neglected the effect of cavity between two layers of MPP, sound absorption model of MPP with ladder micro porous is established. Numerical simulations are carried out to predict the sound absorption of MPP with ladder micro porous. The predicted results show good agreement with measurements. Through analyzing the weight to the sound-absorbing of orifice size, this study also points out that the smaller orifices play the major role in the sound absorption.

Method of reducing the inertia of a thermocouple cable CTMS based on a cable of variable cross-section to improve reliability in aviation and rocket and space technology

2019 ◽  
pp. 65-71
Author(s):  
Р. A. Filippovich ◽  
S. A. Gurova
Keyword(s):  
Comparative Analysis ◽  
Cross Section ◽  
Thermal Equilibrium ◽  
Variable Cross Section ◽  
Point Of View ◽  
Variable Cross ◽  
Space Technology ◽  
Improve Reliability

The method of reducing the inertia of the thermocouple cable ctms based on the use of a cable of variable cross-section is considered. The comparative analysis of time of establishment of thermal equilibrium of a thermocouple cable with variable cross-section and without it is given. The time before the establishment of thermal equilibrium is considered. From a technological point of view, the use of thermocouples based on chromel-alumel is justified. The parameters of inertia of a thermocouple cable of variable cross-section are given.

LABORATORY TESTS OF THYROID FUNCTION IN HYPERTHYROIDISM II.

1969 ◽  
Vol 62 (4_Suppla) ◽  
pp. S23-S35
Author(s):  
B.-A. Lamberg ◽  
O. P. Heinonen ◽  
K. Liewendahl ◽  
G. Kvist ◽  
M. Viherkoski ◽  
...  
Keyword(s):  
Thyroid Function ◽  
Laboratory Tests ◽  
Goodness Of Fit ◽  
Point Of View ◽  
Accurate Estimation ◽  
Diagnostic Efficiency ◽  
Normal Limits ◽  
Significant Difference ◽  
Crossing Point ◽  
Hyperthyroid Patients

ABSTRACT The distributions of 13 variables based on 10 laboratory tests measuring thyroid function were studied in euthyroid controls and in patients with toxic diffuse or toxic multinodular goitre. Density functions were fitted to the empirical data and the goodness of fit was evaluated by the use of the χ2-test. In a few instances there was a significant difference but the material available was in some respects too small to allow a very accurate estimation. The normal limits for each variable was defined by the 2.5 and 97.5 percentiles. It appears that in some instances these limits are too rigorous from the practical point of view. It is emphasized that the crossing point of the functions for euthyroid controls and hyperthyroid patients may be a better limit to use. In a preliminary analysis of the diagnostic efficiency the variables of total or free hormone concentration in the blood proved clearily superior to all other variables.

The Effect of Using Students Peer Teaching on Iraqi EFL Students' Achievement in the Course of Library and Research Work

2019 ◽  
Vol 1 (33) ◽  
pp. 693-714
Author(s):  
. Muntaha Sabbar Jebur
Keyword(s):  
Basic Education ◽  
Teaching Method ◽  
Research Work ◽  
Peer Teaching ◽  
Control Group ◽  
College Of Basic Education ◽  
Significant Difference ◽  
Post Test ◽  
Efl Students ◽  
Experimental Group

          Peer teaching is a strategy that allows the students to teach the new content to each other, and they must be accurately guided by instructors.     The researcher proposes that the use of students peer teaching  may promote students' achievement  and ensure the engagement of all the students in the learning process. Therefore, the researcher employs it as a teaching method aiming at investigating its  effect on Iraqi EFL students' achievement in the course of Library and Research Work .      The study hypothesizes that there is no significant difference between the students' achievement who are taught library and research work by students peer teaching  and that of the students taught by the traditional way. The experimental design of the study is Parallel Groups, Random Assignment, posttest. Each group consists of 35 students, chosen randomly from the Third Year Students at the Department of English in the College of Basic Education. Both groups were matched in terms of their age and parents' education. The experiment was fulfilled in the first course for 15 weeks during the academic year 2016-2017.       The same materials were presented to both groups. This included   units from Writing Research Paper by Lester D. . Post-test was constructed and exposed  The t-test for  independent samples was used to analyze the results and it is found out that there is a statistical difference between the two groups in their achievement because the calculated t- value 2.635 is bigger than the tabulated t- value which is 2.000, and also shown the superiority of the experimental group. The results indicate that the experimental group, who was taught Library and Research Work by peer teaching   was better than the control group, who was taught according to the traditional way. So, the null hypothesis is rejected. Finally, some recommendations and suggestions are presented in the light of the study findings. to a jury of experts to verify its validity and it was administered to both groups.

Boundary element method in numerical study of three-dimensional Stokes flows in channels of arbitrary shape

2012 ◽  
Vol 9 (1) ◽  
pp. 94-97
Author(s):  
Yu.A. Itkulova
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Cross Section ◽  
Numerical Study ◽  
Three Dimensional ◽  
Cylindrical Tube ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Periodic Flows ◽  
Element Method

In the present work creeping three-dimensional flows of a viscous liquid in a cylindrical tube and a channel of variable cross-section are studied. A qualitative triangulation of the surface of a cylindrical tube, a smoothed and experimental channel of a variable cross section is constructed. The problem is solved numerically using boundary element method in several modifications for a periodic and non-periodic flows. The obtained numerical results are compared with the analytical solution for the Poiseuille flow.

Longitudinal oscillation of a rod with a variable cross section

2019 ◽  
Vol 14 (2) ◽  
pp. 138-141
Author(s):  
I.M. Utyashev
Keyword(s):  
Cross Section ◽  
Natural Frequencies ◽  
Liouville Problem ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Longitudinal Vibrations ◽  
Cross Sectional ◽  
Independent Functions ◽  
The Cross ◽  
The Right

Variable cross-section rods are used in many parts and mechanisms. For example, conical rods are widely used in percussion mechanisms. The strength of such parts directly depends on the natural frequencies of longitudinal vibrations. The paper presents a method that allows numerically finding the natural frequencies of longitudinal vibrations of an elastic rod with a variable cross section. This method is based on representing the cross-sectional area as an exponential function of a polynomial of degree n. Based on this idea, it was possible to formulate the Sturm-Liouville problem with boundary conditions of the third kind. The linearly independent functions of the general solution have the form of a power series in the variables x and λ, as a result of which the order of the characteristic equation depends on the choice of the number of terms in the series. The presented approach differs from the works of other authors both in the formulation and in the solution method. In the work, a rod with a rigidly fixed left end is considered, fixing on the right end can be either free, or elastic or rigid. The first three natural frequencies for various cross-sectional profiles are given. From the analysis of the numerical results it follows that in a rigidly fixed rod with thinning in the middle part, the first natural frequency is noticeably higher than that of a conical rod. It is shown that with an increase in the rigidity of fixation at the right end, the natural frequencies increase for all cross section profiles. The results of the study can be used to solve inverse problems of restoring the cross-sectional profile from a finite set of natural frequencies.

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