Trapezoidal Cycle Research Articles

Identification of Electronic Components Susceptible to Deterioration by Atmospheric Corrosion

Electronic components are often susceptible to deterioration by environmental effects. Several studies have been reported on atmospheric corrosion of electronic devices with focus on functionality, storage capacity, and their miniaturization. However, there is a lack of studies focused on identifying the components most susceptible to atmospheric corrosion, the corrosion products generated in them, and the possible variables that have a greater impact on deterioration. The present study is focused on linking the deterioration of electronic boards with temperature and humidity cycles. This was accomplished through accelerated tests inside an atmospheric chamber, where the concentrations of pollutant gases (NO2 and SO2) are kept constant. Each trapezoidal cycle within the accelerated tests equals one day of field exposure. The results show that the NO2 and SO2 gasses reduced the life of the electronic components by 49.8%. The SO2 gas was found to be the contaminant gas that most influenced the deterioration of electronic devices. Energy-dispersive spectroscopy (EDS) show the formation of CuSO4. The development of protective coating against these pollutant gasses could improve the operation of electronic components.

Shift-characteristics and bounds of thermal performance of organic Rankine cycle based on trapezoidal model

In consideration of the constraints of actual working fluids on theoretical study of organic Rankine cycle (ORC), a trapezoidal cycle (TPC) with theoretical model to simulate ORC was proposed in previous works. In this study, mathematical models of working fluids including model of simulated saturation curve (MSSC) and model of linear saturation lines (MLSL) are proposed and built. Combining mathematical models of working fluids and TPC, the thermodynamic characteristics and principles of TPC (or ORC) can be studied or predicted theoretically. There exists a shift-curve of net power output with corresponding shift-temperature of heating fluid for working fluids, which indicates the shift of net power output from having optimum condition of maximum power to monotonic increase with evaporation temperature. This shift-characteristic is significant to working fluid selection and evaluation of cycle performance, for it indicates that cycle without optimum condition can yield higher net power output than the cycle with optimum condition. Equations to calculate the shift-temperature in ORC (or TPC) are derived; and equations to calculate the highest optimal evaporation temperature and highest maximum power as the highest optimum condition at this shift-temperature are obtained. Based on TPC and its theoretical model, the lower and upper bounds of thermal performance (maximum power and corresponding thermal efficiency) of TPC (or ORC) can be demonstrated and acquired. TPC can develop to Carnot cycle or trilateral cycle that it is significant to use TPC as a generalized cycle to study the general principles and characteristics of the cycles.

Thermodynamic relation between irreversibility of heat transfer and cycle performance based on trapezoidal model

Irreversible degree of heat transfer in organic Rankine cycle (ORC) is proposed in this paper. Based on a trapezoidal cycle (TPC) and its theoretical model, the model and mathematic formulas of irreversible degree of heat transfer is built. Thermodynamic relation between irreversible degree and cycle performance (thermal efficiency, net power output and exergy efficiency) is built and studied, which can be applied to the coupling optimization between cycle performance and heat transfer processes. Similar to net power output, there exists a kind of shift-curve of irreversible degree and the corresponding shift-temperature of heating fluid for working fluids, which indicates the shift of irreversible degree from having optimum condition with a minimum to monotonic decrease with heating fluid temperature. The range of irreversible degree and range of cycle performance according to irreversible degree are obtained respectively. Moreover, a model of working fluid with linear saturation line is proposed to study the general thermodynamic principles of TPC (or ORC) theoretically without the restriction of actual working fluids.

A trapezoidal cycle with theoretical model based on organic Rankine cycle

Based on organic Rankine cycle (ORC), a trapezoidal cycle with theoretical model is proposed and built according to the trapezoidal configuration and the thermodynamic relation in T–s diagram. Simulations show that the relative deviation between trapezoidal cycle and ORC is lower than 5% within evaporation temperature of 5 °C lower than the critical temperature of the working fluids. Empirical equations to calculate the optimal evaporation temperature, the maximum net power output and the corresponding thermal efficiency are built, which relative deviations from ORC are lower than 4%. Trapezoidal cycle can break through the restrictions of the actual working fluids and the configuration of the ORC to extend the study of the ORC and investigate the general principle of the ORC (or the trapezoidal cycle). Trapezoidal cycle can develop to trilateral cycle or Carnot cycle, which are the boundary cycles of the trapezoidal cycle. Trapezoidal cycle can be used as a general cycle to investigate the relations and principles among the trilateral cycle, Carnot cycle and trapezoidal cycle (or ORC). The performance of these three cycles at maximum power and their relations are investigated in the same conditions of finite heat source. Results show that the maximum power and the corresponding thermal efficiency of the trapezoidal cycle are bounded between Carnot cycle and trilateral cycle. Copyright © 2016 John Wiley & Sons, Ltd.

Influence of confinement pressure and air voids on the repeated creep and recovery of asphalt concrete mixtures

A laboratory investigation was conducted to capture the influence of confinement pressure and specimen air voids on the creep and recovery response of asphalt concrete (AC) mixtures. AC specimens were fabricated at 2% and 7% air voids and tested at three temperatures (20, 40 and 55°C) and at unconfined and confined conditions (100 and 200 kPa). A total of 20,000 repetitions of a repeated trapezoidal loading and recovery cycle were applied. The resulting creep curves showed four distinct patterns of the three-stage creep curve depending on the loading condition and specimen density. To quantify the mechanical response during the secondary stage where the response was found to be linear, linear viscoelastic modelling was carried out. Using creep time, energy stored and energy dissipated, which were determined from model parameters; the influence of air voids and confinement pressure was quantified.

Regularities in macro- and micromechanisms of fatigue crack growth in a bimetal of continuous caster rolls

• Stage-like nature of the fatigue crack propagation in the bimetallic specimen into macro-, meso-, and micro-levels is determined. • It is found that 10 s hold under the maximum loading (trapezoidal cycle) increases the fatigue crack growth rate by 3–8 times. • The step of striations is 60% lower than the macrorate.

Closure to “Discussion of ‘Yield Function for Solder Elastoviscoplastic Modeling’” (2005, ASME J. Electron. Packag., 127, pp. 147–156)

Closure to “Discussion of ‘Yield Function for Solder Elastoviscoplastic Modeling’” (2005, ASME J. Electron. Packag., 127, pp. 147–156)

A quantum chemical study of [1.1.1.1]pagodane and its related compounds

The PBE0/6-31G** quantum chemical method is used to determine the symmetry and equilibrium structural parameters of the molecules of [1.1.1.1]pagodane (C20H20, D2h), two dienes (C20H20, D2h), two diradicals (C20H20, C2ν), and two dications (C20H202+, D2h and C2ν). The energy of a highly symmetric dication with a rectangular cycle is lower by 36 kcal/mole than that of a low symmetric dication with a trapezoidal cycle. The polarization interaction with liquid methylene chloride causes its decrease by 147 kcal/mole.

Development of a Nb 3Sn multifilamentary wire for accelerator magnet applications

CEA/Saclay and Alstom/MSA have carried out a program to develop a Nb 3Sn multifilamentary wire for accelerator magnet applications relying on the internal-tin process. The main wire specifications are: an overall diameter of 0.825 mm, a critical current larger than 405 A at 4.2 K and 7 T, hysteresis losses lower than 450 mJ/cm 3 for a±3 T trapezoidal cycle, and a copper-to-non-copper ratio greater than 1. The last phase of the optimization program was based on four different strands and we present here the results of the characterization tests, including residual resistivity ratio, critical current and AC loss measurements.

The Benefit of Hydrogen Addition to the Boiling Water Reactor Environment on Stress Corrosion Crack Initiation and Growth in Type 304 Stainless Steel

Intergranular Stress Corrosion Cracking (IGSCC) in Type 304 stainless steel in high temperature high purity water requires the simultaneous presence of sensitized material, high tensile stress and oxygen. Laboratory and in-reactor stress corrosion tests have shown the benefits of adding hydrogen to the boiling water reactor feed-water to reduce the dissolved oxygen concentration and thereby reduce the chemical driving force for IGSCC. The purpose of this program was to verify the benefit of hydrogen additions on the stress corrosion crack behavior. The program investigated the fatigue and constant load crack growth behavior using fracture mechanics specimens in hydrogen water chemistry (HWC). Isothermal heat treatments were used to sensitize Type 304 stainless steel. Additionally, full size pipe tests containing actual welds were used to evaluate crack initiation, as well as propagation of cracks, to verify the results of the fracture mechanics tests. These pipe tests were performed under a trapezoidal loading cycle. The results of the small specimen tests show that HWC inhibits IGSCC in Type 304 stainless steel. The effects of cyclic loading at slow frequencies which promote IGSCC were also evaluated. Computer aided methods were used in the collection and interpretation of the high temperature crack growth data. The full-size component tests substantiated the benefit of HWC in both crack initiation and growth. All results presented were compared to baseline test data to put the results into perspective.