Important Mechanical and Chemical Factors in the Failure Behavior of Polybutadiene Rubber Undergoing Oxidative Aging at Ambient Temperature

1969 ◽  
Vol 42 (4) ◽  
pp. 1095-1121 ◽  
Author(s):  
C. S. Kim
Keyword(s):  
Oxidative Degradation ◽  
Life Time ◽  
Failure Behavior ◽  
Oxidative Aging ◽  
Mechanical Effects ◽  
Chemical Effects ◽  
Polybutadiene Rubber ◽  
Atmospheric Exposure ◽  
Chemical Factors

Abstract Zhurkov's molecular kinetic concept of failure for hard solid materials was extended for application to rubber systems which undergo oxidative degradation during long-term atmospheric exposure. In an effort to analyze the chemical and mechanical effects separately, the dependency of the life-time of the uniaxially stressed rubber was expressed in terms of (1) chemical effects involving the primary chemical bonds in the effective chains, and (2) mechanical effects involving the network structure of the rubber.

The Oxidative Aging of a Compounded Natural Rubber Vulcanizate

1978 ◽  
Vol 51 (1) ◽  
pp. 1-6 ◽  
Author(s):  
R. A. Pett ◽  
R. J. Tabar
Keyword(s):  
Natural Rubber ◽  
Reaction Rate ◽  
Oxidative Degradation ◽  
Accelerated Aging ◽  
Zero Order ◽  
Elongation At Break ◽  
Oxidative Aging ◽  
Zero Order Reaction ◽  
The Impact

Abstract For the type of natural rubber compound used in the impact absorbing bumper system, it has been shown that an apparent zero order reaction rate is valid for the degradation of tensile strength, elongation at break and tear strength during oven aging. The zero order rate applies to aging times beyond an induction period and prior to the onset of hardening. Since the rates follow the Arrhenius equation for rate-temperature dependence, accelerated aging can be readily applied to the prediction of long term changes in properties (within the temperature range of 82–171°C). The magnitude of the activation energy determined from losses in mechanical properties indicates the dominance of oxidative degradation as the mechanism of the losses in properties.

The generalized regularities of damageability and integrity in estimations of the endurance in conditions of variability of loading regimes

2019 ◽  
Vol 85 (9) ◽  
pp. 61-65
Author(s):  
N. A. Makhutov
Keyword(s):  
Life Time ◽  
Cyclic Strength ◽  
Laboratory Diagnostics ◽  
Methodological Issues ◽  
Break Points ◽  
Number Of Cycles ◽  
Cyclic Damage ◽  
Damage Summation ◽  
Temperature Factors

We consider and analyze general methodological issues regarding the strength and endurance (life-time) of the materials and structure elements under a combined effect of various force, deformation and temperature factors. The Journal "Zavodskaya laboratoriya. Diagnostika materialov" (Industrial laboratory. Diagnostics of materials) has launched systematic publications on this problematic since 2018. For many decades, domestic and foreign laboratory studies have gleaned to a traditional methodology for obtaining initial curves of the long-term and cyclic strength that related the breaking stresses with time or number of cycles. These curves, with the characteristic sections and break points, separating the areas of elastic and inelastic (plastic strain or creep strain) strain, are used in analysis of long-term and cyclic damage. Using the elementary linear law of damage summation, it is possible to calculate at a first approximation the strength and endurance under varying conditions of loading. Stepping up the requirements to the accuracy of calculations necessitates a transition from force fracture criteria (at stresses a) to deformation criteria (in elastic and inelastic deformations e). Thus, it becomes possible to construct and use a unified expression for the curve of the long-term cyclic fracture (taking into account the temporal x and cyclic N factors) and a long-term cyclic damage. With such approach it is possible to remain the linear law of damage summation though those damages are obviously nonlinear. The goal of the study is to continue and support the discussion of the most complex problems of a comprehensive assessment of the strength, resource, survivability and safety of high-risk engineering equipment within the journal pages.

A Novel Potentiometric PVC-membrane Cysteamine-Selective Electrode Based on Cysteamine-Phosphomolybdate Ion-Pair

2020 ◽  
Vol 16 (2) ◽  
pp. 168-175 ◽  
Author(s):  
Merve Tumur ◽  
Gulsah Saydan Kanberoglu ◽  
Fatih Coldur
Keyword(s):  
Analytical Methods ◽  
Pharmaceutical Preparations ◽  
Life Time ◽  
Ion Pair ◽  
Pharmaceutical Formulation ◽  
Pvc Membrane ◽  
Selective Electrode ◽  
Potentiometric Response ◽  
Drug Quality Control

Background: Cysteamine is used as an orphan drug in the treatment of cystinosis to prevent long-term cystine accumulation in lysosomes. Dosing in cysteamine treatment is extremely important and overdose may cause some side effects. Up to now, various analytical methods have been used for cysteamine determination. Many of these methods require sophisticated instruments, expert operators, time-consuming measurement procedures and manipulation steps, expensive supplies and long analysis time. Aims and Objective: The present study deals with the development of a potentiometric PVC-membrane cysteamine-selective electrode based on an ion-pair of cysteamine and its application in a pharmaceutical formulation. Methods: Cysteamine (Cys)-Phosphomolybdate (PM) ion-pair was synthesized by mixing the equal volumes of 10-2 M Cysteamine HCl and sodium phosphomolybdate aqueous solutions. The obtained precipitate was used as ionophore in the structure of PVC-membrane. Results and Discussion: The electrode exhibited a linear response in the concentration range of 1.0×10- 1-1.0×10-5 M cysteamine with a slope of 51,7 mV per decade and detection limit of 1.0×10-5 M. The potentiometric response of the electrode was very rapid (5 s), adequately repeatable, stable and selective. pH working range and life-time of the electrode were also determined as 3.0-7.0 and 25 days, respectively. Conclusion: A PVC-membrane cysteamine selective electrode was easily prepared. Cysteamine determination in a pharmaceutical formulation was performed. Analysis results indicated that it can be successfully used in drug quality control laboratories for routine analysis of cysteamine in pharmaceutical preparations alternative to more sophisticated, expensive and time-consuming analytical methods.

A System Based Approach to Achieve Long Term Integrity of Gas Facilities

2012 ◽  
Author(s):  
W. Sloterdijk ◽  
M. Hommes
Keyword(s):  
Oil And Gas ◽  
Life Time ◽  
Transmission Systems ◽  
Design Life ◽  
Design Build ◽  
Challenging Environment ◽  
Time Extension ◽  
Optimum Cost ◽  
New Facility

In today’s challenging environment, the priority for many oil and gas operation companies is to design, build and safely operate facilities at optimum cost efficiency. This means that new facility designs must consider critical facility integrity and that existing facilities are operated well beyond their intended design life. Main gas transmission systems are now some 50 years old and operate for longer periods than anticipated during design and construction for reasons such as; the transition to renewables with another 50 years of service foreseen, and; gas transmission systems that operate satisfactorily, have very low failure rates and for which the planned safe life time extension is expected to be the lowest cost option.

Modified Dyson Continuum Damage Model for Austenitic Steel Alloy

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Seok Jun Kang ◽  
Hoomin Lee ◽  
Jae Boong Choi ◽  
Moon Ki Kim
Keyword(s):  
Damage Model ◽  
Life Time ◽  
Continuum Damage ◽  
Creep Life ◽  
Creep Tests ◽  
Continuum Damage Model ◽  
Thermal Plant ◽  
Uniaxial Creep ◽  
Term Creep

Ultrasuper critical (USC) thermal plants are now in operation around the globe. Their applications include superheaters and reheaters, which generally require high temperature/pressure conditions. To withstand these harsh conditions, an austenitic heat-resistant HR3C (ASME TP310NbN) steel was developed for metal creep resistance. As the designed life time of a typical thermal plant is 150,000 h, it is very important to predict long-term creep behavior. In this study, a three-state variable continuum damage model (CDM) was modified for better estimation of long-term creep life. Accelerated uniaxial creep tests were performed to determine the material parameters. Also, the rupture type and microstructural precipitation were observed by scanning electron microscopy. The creep life of HR3C steel was predicted using only relatively short-term creep test data and was then successfully verified by comparison with the long-term creep data.

Long Term Performance of PE4710 Materials in Disinfectant Treated Nuclear Raw Water Systems

2013 ◽  
Author(s):  
Alexander M. Summe ◽  
Douglas P. Munson ◽  
Kenneth Oliphant ◽  
Sarah Chung
Keyword(s):  
Power Plants ◽  
Slow Crack Growth ◽  
Life Time ◽  
Water Systems ◽  
Superior Performance ◽  
Mechanical Degradation ◽  
Service Water ◽  
Long Term Performance ◽  
Term Performance

Degradation of service water systems is a major issue facing nuclear power plants and many plants will require repair or replacement of existing carbon steel piping components. High-density polyethylene (HDPE) has been used in non-safety service water systems for over ten years and has demonstrated superior performance. However, there still exist knowledge gaps around material properties, inspectability, and long-term performance. Specifically, there is a lack of insight on the aging of HDPE piping in disinfectant treated service water systems. This paper summarizes the methodology and results of predicting the expected life time of HDPE piping exposed to oxidizing biocides in numerous end-use scenarios. The aging mechanism of concern is Stage III Chemical-Mechanical degradation, where the polymer is oxidized by biocides and then experiences slow crack growth (SCG). An Aging Model is used to provide general predictions of pipe service life. The results were analyzed for trends and limiting or sensitive operating parameters were identified. For most applications, the specific resin used in the model demonstrated good performance for lifetimes of well over 40 years.

scholarly journals Probability Calibration Of Load Duration Modification Factor For Timber Roofs In The Polish Mountain Zones

2014 ◽  
Vol 60 (2) ◽  
pp. 195-208
Author(s):  
T. Domański
Keyword(s):  
Limit State ◽  
High Stress ◽  
Life Time ◽  
Probabilistic Methods ◽  
Limit States ◽  
Term Limit ◽  
Load Duration ◽  
Maximum Likelihood Methods ◽  
Short And Long Term

Abstract The resistance parameters of timber structures decrease with time. It depends on the type of load and timber classes. Strength reduction effects, referred to as creep-rupture effects, due to long term loading at high stress ratio levels are known for many materials. Timber materials are highly affected by this reduction in strength with duration of load. Characteristic values of load duration and load duration factors are calibrated by means of using probabilistic methods. Three damage accumulation models are considered, that is Gerhard [1] model, Barret, Foschi[2] and Foshi Yao [3] models. The reliability is estimated by means of using representative short- and long-term limit states. Time variant reliability aspects are taken into account using a simple representative limit state with time variant strength and simulation of whole life time load processes. The parameters in these models are fitted by the Maximum Likelihood Methods using the data relevant for Polish structural timber. Based on Polish snow data over 45 years from mountain zone in: Zakopane – Tatra, Świeradów – Karkonosze, Lesko – Bieszczady, the snow load process parameters have been estimated. The reliability is evaluated using representative short – and long –term limit states, load duration factor kmod is obtained using the probabilistic model.

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