scholarly journals Analysis of O-Ring Seal Failure under Static Conditions and Determination of End-of-Lifetime Criterion

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1251 ◽  
Author(s):  
Anja Kömmling ◽  
Matthias Jaunich ◽  
Payam Pourmand ◽  
Dietmar Wolff ◽  
Mikael Hedenqvist
Keyword(s):  
Material Properties ◽  
Safety Margin ◽  
Mechanical Analysis ◽  
Butadiene Rubber ◽  
Dimensional Changes ◽  
Seal Failure ◽  
Ring Seal ◽  
Static Conditions

Determining a suitable and reliable end-of-lifetime criterion for O-ring seals is an important issue for long-term seal applications. Therefore, seal failure of ethylene propylene diene rubber (EPDM) and hydrogenated nitrile butadiene rubber (HNBR) O-rings aged in the compressed state at 125 °C and at 150 °C for up to 1.5 years was analyzed and investigated under static conditions, using both non-lubricated and lubricated seals. Changes of the material properties were analyzed with dynamic-mechanical analysis and permeability experiments. Indenter modulus measurements were used to investigate DLO effects. It became clear that O-rings can remain leak-tight under static conditions even when material properties have already degraded considerably, especially when adhesion effects are encountered. As a feasible and reliable end-of-lifetime criterion for O-ring seals under static conditions should include a safety margin for slight dimensional changes, a modified leakage test involving a small and rapid partial decompression of the seal was introduced that enabled determining a more realistic but still conservative end-of-lifetime criterion for an EPDM seal.

scholarly journals Influence of Bio-Based Plasticizers on the Properties of NBR Materials

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2095 ◽  
Author(s):  
Md Mahbubur Rahman ◽  
Katja Oßwald ◽  
Katrin Reincke ◽  
Beate Langer
Keyword(s):  
Material Properties ◽  
Canola Oil ◽  
Mechanical Characteristics ◽  
Mechanical Analysis ◽  
Mechanical And Thermal Properties ◽  
Butadiene Rubber ◽  
Main Interest ◽  
Oxidative Aging ◽  
Monomer Ratio ◽  
Aging Properties

A high number of technical elastomer products contain plasticizers for tailoring material properties. Some additives used as plasticizers pose a health risk or have inadequate material properties. Therefore, research is going on in this field to find sustainable alternatives for conventional plasticizers. In this paper, two modified bio-based plasticizers (epoxidized esters of glycerol formal from soybean and canola oil) are of main interest. The study aimed to determine the influence of these sustainable plasticizers on the properties of acrylonitrile–butadiene rubber (NBR). For comparison, the influence of conventional plasticizers, e.g., treated distillate aromatic extract (TDAE) and Mesamoll® were additionally investigated. Two types of NBR with different ratios of monomers formed the polymeric basis of the prepared elastomers. The variation of the monomer ratio results in different polarities, and therefore, compatibility between the NBR and plasticizers should be influenced. The mechanical characteristics were investigated. In parallel, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) were performed and filler macro-dispersion was determined. Bio-based plasticizers were shown to have better mechanical and thermal properties compared to conventional plasticizers. Further, thermo-oxidative aging was realized for 500 h, and afterwards, mechanical characterizations were done. It was observed that bio-based plasticizers have almost the same aging properties compared to conventional plasticizers.

scholarly journals Safety margin against the fatigue fracture under random loading

2018 ◽  
Vol 165 ◽  
pp. 22033 ◽  
Author(s):  
Martin Garan ◽  
Vladimír Chmelko ◽  
Ervin Schafer
Keyword(s):  
Yield Stress ◽  
Fatigue Fracture ◽  
Cross Section ◽  
Material Properties ◽  
Safety Margin ◽  
Time Varying ◽  
Random Loading ◽  
Fatigue Lifetime ◽  
Loading Process

The fatigue lifetime of the structure in operation is express in the number of working cycles, kilometers or time depending units. By harmonic process of loading is possible to express the safety margin as reserve against the required lifetime in the form of number cycles or amplitude of loading. By nonharmonic character of loading process in operation is difficult to express the level of safety margin as the reserve of loading (safety margin in loading). On the case of towing trailer will be discussed more ways of expression the reserve (safety margin) of structure against the fatigue fracture for required fatigue lifetime. For experimental acquired loading process in the most loaded cross-section will be discussed concept of determination of the level safety as reserve in the form of loading parameters. In the case, when the peaks of loading process exceeding the material yield stress (in the most loaded point of the structure) will be discussed concept of expression of loading in the form of time-varying process of strain. By using the cyclic material properties obtained in mode with controlled total strain is possible the safety margin to express also as the multiple of process loading parameters.

Examination of Prestressed Coating/Substrate Systems Using Spherical Indentation—Determination of Film Prestress, Film Modulus, and Substrate Modulus

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
James A. Mills ◽  
Hang Xiao ◽  
Xi Chen
Keyword(s):  
Material Properties ◽  
Indentation Test ◽  
Spherical Indentation ◽  
Indentation Force ◽  
Forward Analysis ◽  
Substrate Properties ◽  
Error Sensitivity Analysis ◽  
Film Substrate

There have been many studies performed with respect to the indentation of thin films affixed to a corresponding substrate base. These studies have primarily focused on determining the mechanical properties of the film. It is the goal of this paper to further understand the role that the film plays and how a potential prestressing of this film has on both the film and substrate base. It is equally important to be able to understand the material properties of the substrate since during manufacturing or long-term use, the substrate properties may change. In this study, we establish through spherical indentation a framework to characterize the material properties of both the substrate and film as well as a method to determine the prestress of the film. It is proposed that through an initial forward analysis, a set of relationships are developed. A single spherical indentation test can then be performed, measuring the indentation force at two prescribed depths, and with the relationships developed from the forward analysis, the material properties of both the film and substrate can be determined. The problem is further enhanced by also developing the capability of determining any equibiaxial stress state that may exist in the film. A generalized error sensitivity analysis of this formulation is also performed systematically. This study will enhance the present knowledge of a typical prestressed film/substrate system as is commonly used in many of today’s engineering and technical applications.

Reactor Pressure Vessel Life Management at French PWR Plants

2002 ◽  
Author(s):  
Anne Mermillod ◽  
Georges Bezdikian ◽  
Serge Rostain
Keyword(s):  
Electricity Generation ◽  
Safety Margin ◽  
Ductile Failure ◽  
Mechanical Analysis ◽  
Reactor Vessel ◽  
Experimental Program ◽  
Surveillance Programme ◽  
Input Parameters ◽  
Reactor Pressure

The capability of nuclear electricity generation by French Utility’s EDF (Electricite´ de France) is 75% of global generation, 58 PWR units are in operation, 34 units three-loop, 20 units four-loop (1300MWe) and 4 units four-loop (1450MWe). The French Utility methodology to justified reactor vessel assessment on specific plants is to verify, for a known defect (real or hypothetic), safety margin to non ductile failure for each transient and for case of loading. The demonstration must be done for each instant of the reactor vessel life, and must include material embrittlement caused by irradiation degradation. This paper will describe EDF methodology aging assessment for at least 40 years, comparing: • The boundary RTNDT (Reference Nil Ductility Transition Temperature) support by reactor vessel. • The estimated RTNDT at 40 years. Estimated RTNDT for 40 years is determined with a prediction formula that needs following input parameters: • The initial RTNDT during the construction. • Fluence assessment received by reactor vessel during 40 years in operation. • Chemistry material composition. The Boundary RTNDT supported by reactor vessel is determined with a mechanical analysis that needs the following input parameters: • Defect characteristics. • Transient definition. The determination of each parameter will be described, and an experimental program to verify the conservatism of methodology will be presented (Irradiation Surveillance Programme).

Preparation And elemental analysis of ancient fibers

1987 ◽  
Vol 45 ◽  
pp. 410-411
Author(s):  
Allen Angel ◽  
Kathryn A. Jakes
Keyword(s):  
Cross Sections ◽  
Physical Structure ◽  
Energy Dispersive ◽  
Archaeological Sites ◽  
X Ray ◽  
Long Term Storage ◽  
Backscattered Electron ◽  
Electron Imaging

Fabrics recovered from archaeological sites often are so badly degraded that fiber identification based on physical morphology is difficult. Although diagenetic changes may be viewed as destructive to factors necessary for the discernment of fiber information, changes occurring during any stage of a fiber's lifetime leave a record within the fiber's chemical and physical structure. These alterations may offer valuable clues to understanding the conditions of the fiber's growth, fiber preparation and fabric processing technology and conditions of burial or long term storage (1).Energy dispersive spectrometry has been reported to be suitable for determination of mordant treatment on historic fibers (2,3) and has been used to characterize metal wrapping of combination yarns (4,5). In this study, a technique is developed which provides fractured cross sections of fibers for x-ray analysis and elemental mapping. In addition, backscattered electron imaging (BSI) and energy dispersive x-ray microanalysis (EDS) are utilized to correlate elements to their distribution in fibers.

Improvement Of Curvilinear Diagrams Of Concrete Deformation

2019 ◽  
pp. 99-104
Keyword(s):  
Reinforced Concrete ◽  
Peak Load ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Deformation Model ◽  
Reinforced Concrete Structures ◽  
Significant Difference ◽  
Deformation Diagrams

Problems when calculating reinforced concrete structures based on the concrete deformation under compression diagram, which is presented both in Russian and foreign regulatory documents on the design of concrete and reinforced concrete structures are considered. The correctness of their compliance for all classes of concrete remains very approximate, especially a significant difference occurs when using Euronorm due to the different shape and sizes of the samples. At present, there are no methodical recommendations for determining the ultimate relative deformations of concrete under axial compression and the construction of curvilinear deformation diagrams, which leads to limited experimental data and, as a result, does not make it possible to enter more detailed ultimate strain values into domestic standards. The results of experimental studies to determine the ultimate relative deformations of concrete under compression for different classes of concrete, which allowed to make analytical dependences for the evaluation of the ultimate relative deformations and description of curvilinear deformation diagrams, are presented. The article discusses various options for using the deformation model to assess the stress-strain state of the structure, it is concluded that it is necessary to use not only the finite values of the ultimate deformations, but also their intermediate values. This requires reliable diagrams "s–e” for all classes of concrete. The difficulties of measuring deformations in concrete subjected to peak load, corresponding to the prismatic strength, as well as main cracks that appeared under conditions of long-term step loading are highlighted. Variants of more accurate measurements are proposed. Development and implementation of the new standard GOST "Concretes. Methods for determination of complete diagrams" on the basis of the developed method for obtaining complete diagrams of concrete deformation under compression for the evaluation of ultimate deformability of concrete under compression are necessary.

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