Evaluation of Controlling Transient Ramp Times Using Piping Methodologies When Considering Environmental Fatigue (Fen) Effects

2007 ◽  
Author(s):  
J. Michael Davis ◽  
Gary L. Stevens
Keyword(s):  
Stress Response ◽  
Strain Rate ◽  
Temperature Change ◽  
Technical Support ◽  
Task Group ◽  
Temperature Changes ◽  
Plant Operations ◽  
Asme Code ◽  
Thermal Transient ◽  
Parametric Analyses

As a part of the 2006 ASME Code support being provided by the Materials Reliability Program (MRP) Fatigue Issue Task Group (ITG), and later the Technical Support Committee (TSC), it is desired to develop a solution that establishes the most severe transient for design purposes when environmental fatigue rules are considered. This problem does not have an obvious answer, since the environmental fatigue multiplier (e.g., Fen) expressions depend on the strain rate during a transient. The strain rate in a thermal transient is dependent on the ramp time of the temperature change. Classically, fatigue analysis has been performed by conservatively considering that temperature changes are instantaneous (e.g., ramp time = zero). This results in maximizing the stress response. But, all other things being equal, Fen effects are minimum at instantaneous changes. Previous work performed by the MRP to support 2005 ASME Code activities has investigated how Fen × Usage varies with ramp time and has concluded that Fen × Usage maximizes at a small but definitely non-zero ramp time [1]. The implications of non-zero transient ramp times are that difficulties arise in both specifying ahead of time and qualifying the component for appropriate ramp times and, at the same time, not creating a situation whereby plant operations are required to proceed at a specified pace to remain design compliant. Therefore, it is desirable to have the qualifying fatigue analyses cover all conceivable ramp times such that the operator neither has to: (a) be limited to a minimum pace, nor (b) confirm through observations that the pace is at least as fast as assumed in the design. This paper summarizes qualifying fatigue analyses that have been performed using piping methodologies to define bounding ramp times for a variety of piping geometry and material configurations. The intent of these analyses is to provide the component designer with a set of parametric tools that can be used to easily design components without the need for iterative fatigue analyses to determine the bounding conditions when Fen rules are considered. In addition, the tool developed to perform the parametric analyses is available for future use by the designer should more specific analyses be required.

A Parametric Study Into the Competing Effects of Stress and Strain Rate in Environmental Fatigue Usage Calculations

2013 ◽  
Author(s):  
Julian Emslie ◽  
Chris Watson
Keyword(s):  
Stainless Steel ◽  
Strain Rate ◽  
Detrimental Effect ◽  
Stress And Strain ◽  
Plant Materials ◽  
Penalty Factor ◽  
Asme Code ◽  
Parametric Studies ◽  
Thermal Transient ◽  
Stress And Strain Rate

Data have emerged that indicate a Pressurised Water Reactor (PWR) environment can have a significant detrimental effect on the fatigue life of plant materials. Proposed methods for accounting for the PWR environment in an ASME III fatigue assessment are presented in ASME Code Case N-792 and NUREG/CR-6909, both of which use a fatigue penalty factor (Fen) approach that directly multiplies the Partial Usage Factor (PUF). Formulae are provided for the Fen factor which are dependent on strain rate, temperature and the dissolved oxygen content of the water. A slower strain rate provides for increased Fen values and therefore increased PUFs. In stress analysis, defining the ramp of a thermal transient as a step change is pessimistic for thermal stress calculations. The dependence of the Fen factor on strain rate means that this approach may not be conservative when the stresses are carried through to a PWR environment enhanced ASME III fatigue calculation. An increased ramp time gives a lower stress, however this also provides for a slower strain rate, and therefore a larger Fen factor. By a series of parametric studies using simple austenitic stainless steel 2D axisymmetric cylinder FE models, this paper examines the competing effects of reduced stress and increased Fen that an increased transient ramp time has upon a PWR environment enhanced ASME III calculated fatigue usage factor for stainless steel components. It was found for thin walled sections that the assumption of a step to define the thermal transient is still pessimistic despite the competing effects. For thicker sections the results showed that this is not always the case, but the potential increase in PUF was found to be minimal.

scholarly journals SIMULATION AND EXPERIMENT OF EXTINCTION OR ADAPTATION OF BIOLOGICAL SPECIES AFTER TEMPERATURE CHANGES

2005 ◽  
Vol 16 (03) ◽  
pp. 389-392 ◽  
Author(s):  
D. STAUFFER ◽  
H. ARNDT
Keyword(s):  
Sexual Reproduction ◽  
Temperature Change ◽  
Biological Species ◽  
Biological Aging ◽  
Heterotrophic Flagellates ◽  
Temperature Changes ◽  
Penna Model ◽  
Simulation And Experiment ◽  
Unicellular Organisms

Can unicellular organisms survive a drastic temperature change, and adapt to it after many generations? In simulations of the Penna model of biological aging, both extinction and adaptation were found for asexual and sexual reproduction as well as for parasex. These model investigations are the basis for the design of evolution experiments with heterotrophic flagellates.

scholarly journals Plastometric tests for plasticine as physical modelling material

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Łukasz Wójcik ◽  
Konrad Lis ◽  
Zbigniew Pater
Keyword(s):  
Strain Rate ◽  
Temperature Change ◽  
Compression Test ◽  
Constitutive Equations ◽  
Metal Forming ◽  
Material Flow ◽  
Physical Modelling ◽  
Flow Curves ◽  
Black And White ◽  
White Colour

Abstract This paper presents results of plastometric tests for plasticine, used as material for physical modelling of metal forming processes. The test was conducted by means of compressing by flat dies of cylindrical billets at various temperatures. The aim of the conducted research was comparison of yield stresses and course of material flow curves. Tests were made for plasticine in black and white colour. On the basis of the obtained experimental results, the influence of forming parameters change on flow curves course was determined. Sensitivity of yield stresses change in function of material deformation, caused by forging temperature change within the scope of 0&C ÷ 20&C and differentiation of strain rate for ˙ɛ = 0.563; ˙ɛ = 0.0563; ˙ɛ = 0.0056s−1,was evaluated. Experimental curves obtained in compression test were described by constitutive equations. On the basis of the obtained results the function which most favourably describes flow curves was chosen.

A Life-Cycle Risk-Informed Systems Structured Nuclear Code

2002 ◽  
Author(s):  
Ralph S. Hill
Keyword(s):  
Life Cycle ◽  
American Concrete Institute ◽  
Design Code ◽  
Replacement Decisions ◽  
Plant Operations ◽  
Operations And Maintenance ◽  
Asme Code ◽  
American Society ◽  
Construction Operation ◽  
Design Construction

Current American Society of Mechanical Engineers (ASME) nuclear codes and standards rely primarily on deterministic and mechanistic approaches to design. The design code is a separate volume from the code for inservice inspections and both are separate from the standards for operations and maintenance. The ASME code for inservice inspections and code for nuclear plant operations and maintenance have adopted risk-informed methodologies for inservice inspection, preventive maintenance, and repair and replacement decisions. The American Institute of Steel Construction and the American Concrete Institute have incorporated risk-informed probabilistic methodologies into their design codes. It is proposed that the ASME nuclear code should undergo a planned evolution that integrates the various nuclear codes and standards and adopts a risk-informed approach across a facility life-cycle — encompassing design, construction, operation, maintenance and closure.

Comparative Study of the Dynamic Behavior of AA2519 Aluminum Alloy in T6 and T8 Temper Conditions

2019 ◽  
Author(s):  
Adewale Olasumboye ◽  
Gbadebo Owolabi ◽  
Olufemi Koya ◽  
Horace Whitworth ◽  
Nadir Yilmaz
Keyword(s):  
Plastic Deformation ◽  
Aluminum Alloy ◽  
Stress Response ◽  
Flow Stress ◽  
Yield Strength ◽  
Strain Rate ◽  
High Strain ◽  
Second Phase ◽  
Strain Rates ◽  
High Strain Rates

Abstract This study investigates the dynamic response of AA2519 aluminum alloy in T6 temper condition during plastic deformation at high strain rates. The aim was to determine how the T6 temper condition affects the flow stress response, strength properties and microstructural morphologies of the alloy when impacted under compression at high strain rates. The specimens (with aspect ratio, L/D = 0.8) of the as-cast alloy used were received in the T8 temper condition and further heat-treated to the T6 temper condition based on the standard ASTM temper designation procedures. Split-Hopkinson pressure bar experiment was used to generate true stress-strain data for the alloy in the range of 1000–3500 /s strain rates while high-speed cameras were used to monitor the test compliance with strain-rate constancy measures. The microstructures of the as received and deformed specimens were assessed and compared for possible disparities in their initial microstructures and post-deformation changes, respectively, using optical microscopy. Results showed no clear evidence of strain-rate dependency in the dynamic yield strength behavior of T6-temper designated alloy while exhibiting a negative trend in its flow stress response. On the contrary, AA2519-T8 showed marginal but positive response in both yield strength and flow behavior for the range of strain rates tested. Post-deformation photomicrographs show clear disparities in the alloys’ initial microstructures in terms of the second-phase particle size differences, population density and, distribution; and in the morphological changes which occurred in the microstructures of the different materials during large plastic deformation. AA2519-T6 showed a higher susceptibility to adiabatic shear localization than AA2519-T8, with deformed and bifurcating transformed band occurring at 3000 /s followed by failure at 3500 /s.

scholarly journals Temperature Distribution in a Sub-Isothermal Glacier

1976 ◽  
Vol 16 (74) ◽  
pp. 309
Author(s):  
M.S. Krass
Keyword(s):  
Temperature Field ◽  
Heat Conduction ◽  
Temperature Distribution ◽  
Strain Rate ◽  
Temperature Change ◽  
Linear Approximation ◽  
Analytical Dependence ◽  
Main Role ◽  
Steady Temperature ◽  
Linear Distribution

Abstract In sub-isothermal glaciers heat conduction plays the main role in the formation of the temperature field, and the contribution of advection is relatively small. The dependence of the strain-rate on the temperature is simplified by a linear approximation. If the whole range of the temperature change in a glacier does not exceed ≈ 3 deg, with the power rheological law the quasi-steady temperature distribution is described by a simple analytical dependence. In the upper part of the ice, the temperature varies with depth almost linearly; the deflection from the linear distribution is essentially in the lower part.

scholarly journals Thermal Time Constant of PV Roof Tiles Working under Different Conditions

2019 ◽  
Vol 9 (8) ◽  
pp. 1626 ◽  
Author(s):  
Kurz ◽  
Nawrowski
Keyword(s):  
Energy Balance ◽  
Thermal Resistance ◽  
Temperature Change ◽  
Environmental Parameters ◽  
Thermal Capacity ◽  
Electrical Characteristics ◽  
Legal Regulations ◽  
Temperature Changes ◽  
Different Types ◽  
The Relationship

This paper presents different types of photovoltaic (PV) roof tiles integrating PV cells with roof covering. Selected elastic photovoltaic roof tiles were characterised for their material and electrical characteristics. Practical aspects of using PV roof tiles are discussed, alongside the benefits and drawbacks of their installation on the roof. Thermal resistance, heat transfer coefficient and thermal capacity were identified for elastic PV roof tiles and roof construction built of boards and PV roof tiles, according to valid standards and legal regulations. The resistance–capacity (RC) models of PV roof tiles and roofs are proposed according to the time constants identified for the analysed systems. The energy balance of the studied systems (PV roof tiles alone and the roof as a whole) is presented, based on which temperature changes in the PV cells of the roof tiles working under different environmental conditions were identified. The timing of PV cells’ temperature change obtained by material data and energy balance analyses were compared. The relationship between the temperature change times of PV cells and the thermal resistance and heat capacity of the whole system are demonstrated, alongside environmental parameters.

Adaptation as a Mechanism for Gain Control in an Insect Thermoreceptor

2008 ◽  
Vol 100 (4) ◽  
pp. 2137-2144 ◽  
Author(s):  
Harald Tichy ◽  
Harald Fischer ◽  
Ewald Gingl
Keyword(s):  
Temperature Change ◽  
Thermal Effects ◽  
Gain Control ◽  
Input Function ◽  
High Gain ◽  
Oscillation Period ◽  
Rate Of Change ◽  
Temperature Changes ◽  
Precise Information ◽  
Instantaneous Temperature

Adaptation controls the gain of the input-function of the cockroach's cold cell during slowly oscillating changes in temperature. When the oscillation period is long, the cold cell improves its gain for the rate of temperature change at the expense of its ability to code instantaneous temperature. When the oscillation period is brief, however, the cold cell reduces this gain and improves its sensitivity for instantaneous temperature. This type of gain control has an important function. When the cockroach ventures from under cover and into moving air, the cold cell is confronted constantly with brief changes in temperature. To be of any use, a limit in the gain for the rate of change seems to be essential. Without such a limit, the cold cell will always indicate temperature change. The decrease in gain for the rate of change involves an increase in gain for instantaneous temperature. Therefore the animal receives precise information about the temperature at which the change occurs and can seek an area of different temperature. If the cockroach ventures back under cover, the rate of change will become slow. In this situation, a high gain improves the ability to signal slow temperature changes. The cockroach receives the early warning of slow fluctuations or even creeping changes in temperature. A comparison of the cold cell's responses with the temperature measured inside of small, cylindrical model objects indicates that coding characteristic rather than passive thermal effects of the structures enclosing the cold cell are responsible for the observed behavior.

scholarly journals Climate-induced population displacements in a 4 ° C+ world

2011 ◽  
Vol 369 (1934) ◽  
pp. 182-195 ◽  
Author(s):  
François Gemenne
Keyword(s):  
Climate Change ◽  
Temperature Change ◽  
Temperature Rise ◽  
Sub Saharan Africa ◽  
Population Movements ◽  
Temperature Changes ◽  
Policy Responses ◽  
Sub Saharan

Massive population displacements are now regularly presented as one of the most dramatic possible consequences of climate change. Current forecasts and projections show that regions that would be affected by such population movements are low-lying islands, coastal and deltaic regions, as well as sub-Saharan Africa. Such estimates, however, are usually based on a 2 ° C temperature rise. In the event of a 4 ° C+ warming, not only is it likely that climate-induced population movements will be more considerable, but also their patterns could be significantly different, as people might react differently to temperature changes that would represent a threat to their very survival. This paper puts forward the hypothesis that a greater temperature change would affect not only the magnitude of the associated population movements, but also—and above all—the characteristics of these movements, and therefore the policy responses that can address them. The paper outlines the policy evolutions that climate-induced displacements in a 4 ° C+ world would require.

scholarly journals The isothermal layer of the atmosphere and atmospheric radiation

1909 ◽  
Vol 82 (551) ◽  
pp. 43-70 ◽  
Keyword(s):  
High Pressure ◽  
Temperature Gradient ◽  
Temperature Change ◽  
Atmospheric Temperature ◽  
Atmospheric Radiation ◽  
Average Height ◽  
Vertical Temperature Gradient ◽  
Vertical Temperature ◽  
Temperature Changes ◽  
Isothermal Layer

The investigation of the upper air by means of balloons carrying self-recording instruments, which have furnished values for the atmospheric temperature up to heights between 15 and 20 kilometres, has revealed the existence of an abnormal change in the vertical temperature gradient. After a fairly uniform fall, with increasing altitude, of about 6° C. per kilometre, a height is reached above which the temperature changes very little, sometimes increasing, sometimes diminishing slowly. The phenomenon was first noticed by M. Teisserenc de Bort in a communication to the Société de Physique in June, 1899. He improved his apparatus and made further investigations, in many cases sending up the balloons by night to eliminate any possible insolation effects. He found the average height, at which the change began, to be about 11 kilometres. He discovered also that the height was greater near the centre of high pressure areas than in low pressure areas, the average heights for the two cases being 12-5 and 10 kilometres respectively. More recently he found that the height increased with approach towards the equator and that near the equator, ballons-sondes , ascending to 15 kilometres, had failed to reach this layer if it existed there. He proposed to call this layer, in which little temperature change occurred, the “Isothermal Layer of the Atmosphere,” and the name has been generally accepted.

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