scholarly journals Enhancement of the Water-Lubricated Tribological Properties of Hybrid PTFE/Nomex Fabric Laminate Composite via Epoxy Resin and Graphite Filler

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 62
Author(s):  
Ying Liu ◽  
Gengyuan Gao ◽  
Dan Jiang ◽  
Zhongwei Yin

This paper studied a hybrid polytetrafluoroethylene (PTFE)/Nomex fabric composite with lower friction coefficient (COF) and high underwater wear resistance. A pin-on-disk tribometer was used to test tribological properties under different applied loads and rotation speeds. The wear surface, transfer film and cross-section were analyzed by scanning electron microscope (SEM) and optical microscope. The results showed enhanced underwater tribological properties because of excellent self-lubricating properties of PTFE fibers and a good lubricating effect and load-carrying capacity of graphite fillers. Improved underwater mechanical strength was connected to the high strength of epoxy resin and high bonding force between Nomex and epoxy resin.

Mechanika ◽  
2019 ◽  
Vol 25 (6) ◽  
pp. 426-433 ◽  
Author(s):  
Tao LAN

In this paper, load-carrying and deformation capacity of tension lap splices that have both welds and bolts acting in the same shear plane are studied using numerical method. The failure criterion of bolts and welds are given based on the finite element calculation and compared with existing experiment results, it shows that the established numerical model is correct and reliable. The strength of longitudinal welds and the bearing capacity of the high-strength bolts before slipping can be fully used in the combined joints, the bolts and welds fail almost simultaneously. The deformation of welds in combined connections is less uniform than its’ deformation in welded joints as the welds fails, and it causes the deformation of welds as failure is larger in combined connections than in welded connections. The deformation capacity of the combined joint are slightly increased contrasted with bolts joint and welds joint because of the interplay of bolts and welds acting in the same shear plane. The strengths of welds and bolts performed in combined connections can reach 0.95 and the deformation of combined connection is increased at least 1.10 times as the welds connection or the bolts connection.


2021 ◽  
Vol 28 (1) ◽  
pp. 71-83
Author(s):  
Mazin Abdulrahman ◽  
Shakir Salih ◽  
Rusul Abduljabbar

In this research, an experimental study is conducted to investigate the behavior and strength of high strength reinforced concrete corbels externally bonded with CFRP fabric sheets and Plates with different patterns taking into account the effect of adopted variables in enhancing the ultimate strength; the effect of shear span to effective depth (a/d), configuration, type and amount of bonding. Eleven high strength reinforced corbels were cast and tested under vertical loads. Test results showed there was an improvement in the behavior and load carrying capacity of all strengthened corbels. An increasing in the ultimate strength of strengthened corbel by inclined CFRP strips reached to (92.1%) while the increasing reached to (84.21%) for using one horizontal CFRP Plates compared to un-strengthened reference specimen. Also, it can be conducted that the increase of (a/d) ratio from (0.6 to 0.8) resulted in decreasing by 21.05% in ultimate load capacity of corbels and from (0.4 to 0.6) by 31.25% and 58.69% in cracking and ultimate loads respectively Using CFRP .


2021 ◽  
Author(s):  
Anil K. Kar

Reinforced concrete is the number one medium of construction. It is important to have good quality concrete and reinforcing bar (rebar). It is equally important to have competent bond between rebar and concrete. About six decades ago ribbed rebars of high strength steel started replacing plain round bars of mild steel, the use of which had made reinforced concrete constructions durable. It was overlooked that ribbed rebars of carbon steel would be highly susceptible to corrosion at accelerated rates. That would not only make reinforced concrete constructions reach states of distress early, that could also destroy or reduce bond between ribbed rebars and concrete. The continued use of ribbed rebars of high strength carbon steel demonstrates a widespread lack of understanding of the phenomenon of bond between rebars and concrete. This lack of understanding of bond has led to the introduction of epoxy coated ribbed rebars, ribbed stainless steel bars and glass fiber reinforced and granite reinforced polymer rebars, all of which permit reinforced concrete carry static loads because of engagement between such rebars and concrete. But the load-carrying capacity of reinforced concrete elements is impaired, and such elements become vulnerable to local or even total failure during vibratory loads. The use of PSWC-BAR, characterized by its plain surface and wave-type configuration, permits the use of medium strength and high strength steel. In the absence of ribs, the rate of corrosion is greatly reduced. The use of PSWC-BARs, at no added effort or cost, in lieu of conventional ribbed bars, leads to enhancement of effective bond or engagement between such rebars and concrete, thereby leading to increased load-carrying capacity, several-fold higher life span, ductility and energy-absorbing capacity, and great reduction in life cycle cost and adverse impact of construction on the environment and the global climate. In keeping with a lack of understanding of bond between rebars and concrete, there is arbitrariness in the selection of the required level of percent elongation and ductility of rebars.


2010 ◽  
Vol 16 (3) ◽  
pp. 352-362 ◽  
Author(s):  
Zdeněk Kala ◽  
Libor Puklický ◽  
Abayomi Omishore ◽  
Marcela Karmazínová ◽  
Jindřich Melcher

The presented paper deals with the stochastic analysis of the ultimate limit states of steel‐concrete building members. The load carrying capacity of steel‐concrete columns, comprising of steel profiles encased in high strength concrete, in compression is analyzed. The first part of the paper lists assumptions for the determination of the theoretical load carrying capacity of the column. Principles of elasticity and plasticity are used to determine stresses in the concrete and steel sections. Statistical characteristics of input material and geometrical imperfections are listed. Results of the theoretical analysis are then compared with results of experimental research. Statistical characteristics of obtained results of the theoretical analysis were verified using statistical characteristics obtained from experimental research. Numerical simulation LHS and Monte Carlo methods, which take into account the influences of variability of input imperfections, were employed. The influence of the utilization of the plastic reserve in the determination of the load carrying capacity of the analysed strut is shown. The influence of the initial geometric imperfections of initial strut curvature on the load carrying capacity is also presented. Santrauka Straipsnyje pateikta plienbetonio pastatu elementu didžiausiu ribiniu būkliu stochastine analize, analizuojama plienbetonio kolonu, sudarytu iš plieniniu profiliuočiu, padengtu didelio stiprio betonu, laikomoji galia gniuždant. Pirmoje straipsnio dalyje išvardytos kolonos teorines laikomosios galios nustatymo prielaidos. Tamprumo ir plastiškumo principai taikyti itempiams betono ir plieno skerspjūviuose nustatyti. Nustatytos medžiagu ir geometriniu defektu statistines charakteristikos, teorines analizes rezultatai palyginti su eksperimentiniu tyrimu rezultatais. Teorines analizes metu gautu rezultatu statistines charakteristikos patikrintos taikant iš eksperimentiniu tyrimu gautus statistinius rodiklius. Pritaikytas skaitinis modeliavimas LHS ir Monte Karlo metodais, kurie ivertina pradiniu defektu kintamumo itaka. Parodyta plastiškumo atsargos naudojimo itaka, nustatant analizuojamojo statramsčio laikomaja galia, pateikta pradinio statramsčio išlinkio pirminiu geometriniu defektu itaka laikomajai galiai.


1996 ◽  
Vol 118 (3) ◽  
pp. 232-237 ◽  
Author(s):  
R. J. Dexter ◽  
J. M. Ricles ◽  
L.-W. Lu ◽  
A. A.-K. Pang ◽  
J. E. Beach

Compression tests were conducted on high-strength single-cell and multiple-cell box sections with plate width-to-thickness (b/t) ratios ranging from 48 to 96. Local plate buckling occurred at stresses as low as 5 percent of the yield stress, whereas the ultimate compression stress ranged from 38 to 72 percent of the yield stress. These critical stresses were not significantly affected by the length of the specimen, the number of cells, the boundary conditions, or lateral load. Simple empirical design equations based only on b/t gave estimates of the collapse strength within five percent in all cases. Finite-element analyses were able to predict the significant reserve load-carrying capacity and ductility after ultimate load, which was dependent on the length of the specimen as well as the b/t ratio.


Author(s):  
Aizoh Kubo

Some typical examples of failure of gears made from very high strength steel are shown and its trigger and whose causes are discussed: Many of such failure are triggered by tooth side edge contact or tooth tip edge contact and meshing-in of the wear debris. The limit of validity of the traditional methods for load carrying capacity of gears exists in the fact that they are based on the theory of contact of tooth flanks that realize conjugate or almost conjugate action of gears. To be able to design reliable gears made from very high strength steel, a principle is shown that suggests a new method for tooth form modification and of longitudinal crowing modification to avoid such failure. Metallurgical problem of gear material and special heat treatment aiming high surface hardness is also discussed.


1990 ◽  
Vol 211 ◽  
Author(s):  
Mette Glavind ◽  
Tine Aarre

AbstractThe application of high-strength concrete in practice is strongly limited by its more brittle behaviour than normal strength concrete.The present study deals with an investigation of the possibilities of increasing the fracture toughness of high-strength concrete by adding fibres. Tests are made with both normal strength concrete and high-strength concrete containing different amounts of steel and polypropylene fibres. Stress-strain curves in compression are obtained by a deformation controlled test system. The toughness is described with different toughness indexes.By using a previously proposed expression for the stress-strain curves, it is possible to make a non-linear load carrying capacity calculation for reinforced concrete beams. The results of the load carrying capacity calculation are compared with results of similar calculations made with the Danish code extrapolated to be valid for high-strength concrete.The investigation shows that the addition of especially steel fibres is effective in increasing toughness and the non-linear load carrying capacity for high-strength concrete. It is also shown that the compression strength of high-strength concrete is increased by addition of steel fibres. The results of the load carrying capacity calculation show that the Danish code cannot be extrapolated to be valid for high-strength concrete without any modifications.


2010 ◽  
Vol 163-167 ◽  
pp. 433-438
Author(s):  
Xian Lei Cao ◽  
Ji Ping Hao ◽  
Chun Lei Fan

To obtain a better understanding of the behavior and load-carrying capacity of Q460 high-strength single-angle compression members bolted by one leg, using static loading way to 48 angles carried out experimental study. The experiments show test specimens produce biaxial bending, most small slenderness ratio members are controlled by local buckling, and slender specimens are controlled by overall buckling. In addition to these factors in model experiment, influences of residual stresses on ultimate load-carrying capacity were analyzed by finite element numerical simulation analysis, the results show the residual stresses affect the ultimate load-carrying capacity of angles by about 5% or less. Comparison of the load-carrying capacity of experimental and theoretical results indicate the difference of experimental and finite element values ranges from -9.99% to +9.76%, American Design of Latticed Steel Transmission Structure (ASCE10-1997) and Chinese Code for Design of Steel Structures (GB50017-2003) underestimate separately the experimental load-carrying capacity by about 2.34%~33.93% and 1.18%~63.3%, and the agreement is somewhat good between experimental program and the finite element analysis. Based on model experiment and simulated experiment, the formula of stability coefficient of single-angle compression members was established. It provides basic data for spreading Q460 high-strength single-angles members attached by one leg.


2013 ◽  
Vol 812 ◽  
pp. 226-230 ◽  
Author(s):  
Siti Shuhadah Mohd Saleh ◽  
Md Akil Hazizan ◽  
Ramdziah Md. Nasir ◽  
Herza Hasmi

Carbon nanotube (CNT) reinforced polymer composites are of great interest, because their superior properties can produce composite materials with high strength, light weight, and multifunctional features. In this work, the thermal and tribological properties (wear) of Phenolic/CNT-Alumina Hybrid composites were studied. The CNT-alumina hybrid (chemically hybrid) was produced via Chemical Vapour Deposition (CVD). The Phenolic/CNT-Alumina Hybrid composites were fabricated using hot mounting moulding. The tribological properties were monitored using a Ducom TR-20 pin-on-disk tester, under dry sliding conditions. The thermal conductivity was measured using the Transient Plane Source (TPS) method, using a Hot-DiskTM Thermal Constant Analyzer. The results show that CNT-Alumina hybrid enhanced the thermal and tribological properties of the polymer composites.


2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Mechri Abdel Ghani ◽  
Ghomari Tewfik ◽  
Djouadi Djahida

The evaluation of pipelines having external corrosion defect and their remaining load-carrying capacity is a concern which becomes important in energy industry, especially with the increasing operating pressures and the consequences which can occur following the bursting of these pipelines. A lower bound analytical solution for the prediction of the burst pressure of pipelines is proposed. This solution is based on the approach of plastic-instability criterion in terms of material strain-hardening exponent of internally pressurized corroded pipelines. The suggested solution is evaluated by using database comprising more than 100 carried out tests of pipelines with or without corrosion defects. This database is collected from the literature and covers the majority of steel materials as well as the various standard sizes. The accuracy of the proposed solution is compared with B31.G method and its improved version B31.G Mod by using statistical analyses in terms of average error and its correspondent standard deviation. The proposed solution is accurate than B31.G and modified B31.G methods that are conservative and provide in some cases of middle and high strength material an overestimated burst pressure predictions.


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