Measurements of magnetic circuit characteristics for comprehension of intrinsic magnetic properties of materials from surface inspection

A transfer function is presented for calculating magnetic field and flux density inside a test material as a result of surface measurement. By considering flux leakage, we introduce a parameter η, called the leakage coefficient, which can be experimentally determined. It is introduced into the equations to make the transfer function more practical. The distribution of field inside a test material is then discussed in accordance with a surfacemagnetic charge model

Magnetomechanical effect in nickel and cobalt

The change in magnetization as a result of applied uniaxial stress has been measured in nickel and cobalt. Both tensile and compressive stresses were applied up to 125 MPa. Magnetostriction and anhysteretic magnetization as a function of stress were also measured. The change in magnetization with stress depended on the applied stress and the displacement between the prevailing magnetization and anhysteretic. At the loop tips, nickel showed a +6 mT (compression) and −6 mT (tension) magnetization change while cobalt displayed a +15 mT (compression) and −15 mT (tension) magnetization change. At remanence,nickel decreased in magnetization by 45 mT under either sign of stress, while cobalt decreased by 20 mT also under either sign of stress. Magnetomechanical changes in magnetization near the loop tips were mostly reversible, while at remanence the magnetomechanical change was predominately irreversible. Cobalt generally displayed larger changes in magnetization with stress than nickel at locations close to the loop tips, while the converse was true at locations near remanence. The results confirm the hypothesis that the magnetomechanical effect(dM/dσ) depends on the displacement between the anhysteretic and prevailing magnetization

MARC-60 and Propulsion System Collaboration Status Meeting

No abstract availabl

When to invest in carbon capture and storage technology in the presence of uncertainty: a mathematical model. ESRI WP461, July 2013

We present a model for determining analytically the critical threshold for investment in carbon capture and storage technology in a region where carbon costs are volatile and assuming the cost of investment decreases. We first study a deterministic model with quite general dependence on carbon price and then analyse the effect of carbon price volatility on the optimal investment decision by solving a Bellman equation with an infinite planning horizon. We find that increasing the expected carbon price volatility increases the critical investment threshold and that adoption of this technology is not optimal at current prices, in agreement with other works. However, reducing carbon price volatility by switching from carbon permits to taxes or by introducing a carbon floor as in Great Britain would accelerate the optimal adoption of this technology. Our deterministic model provides a good description of this decision problem

Finite element analysis of the influence of a fatigue crack on magnetic properties of steel

Fatigue can affect the magnetic properties of materials due to microstructural changes. Previous investigations have shown that several structure sensitive magnetic properties, such as coercivityHc and remanenceBr, changed systematically as a result of fatigue. When approaching failure the accumulated changes in microstructure resulted in the occurrence of fatigue cracks and the magnetic properties showed dramatic changes which mainly resulted from the geometrical changes in samples due to the cracks. It was found that the remanenceBr followed the changes in stress, while the coercivityHc sometimes showed different trends. In this article the influence of the size and the position of a fatigue crack on magnetic field and magnetic induction were studied using finite element modeling. Models were constructed to simulate the geometry of the test sample and sensor. It was found that, for a given coil current in the exciting coil, the magnetic induction was mainly determined by the geometry of the crack, while the magnetic field was influenced by both the size and the position of the crack

Modeling of the magnetomechanical effect: Application of the Rayleigh law to the stress domain

Stress is one of the principal external factors affecting the magnetization of materials. The magnetomechanical effect, that is, the change of magnetization of a magnetic material resulting from the application of stress, has attracted attention because of its scientific complexity. An improved model equation for interpreting the magnetomechanical effect has been developed based on extension of the previous equation to include the Rayleigh law. According to the previous theory of the magnetomechanical effect, which is based on the “law of approach,” application of stress induces changes in magnetization toward anhysteretic magnetization which itself is stress dependent, and the rate of change of magnetization with the input elastic energy is dependent on the displacement of the prevailing magnetization from the anhysteretic magnetization. The theory has been refined by including a linear term in the model equation in addition to the well-known quadratic term. It was found that the modified theory provides a much better description of the magnetization changes under stress, particularly at small applied stress amplitudes and when the stress changes sign

Magnetic Property Changes in various Structural Steels Due to Irradiation

Nondestructive evaluation in nuclear power plants has been a growing concern for electric utility operators over the past decade 1. Many plants are operating beyond their original design lives primarily through intermittent replacement of individual components as necessary. It is critically important for the NDE field to develop technology that can evaluate the life expectancy of components in these plants, such as steam boiler pipes, headers and tubes, steam turbine rotors and blades, and nuclear pressure vessels. These components typically experience long service exposure, high temperature under high loading conditions, corrosive media and neutron irradiation. The focus of this paper will be on the irradiation effects

Electron-deuteron scattering in the equal-time formalism: beyond the impulse approximation

Using a three-dimensional formalism that includes relativistic kinematics, the effects of negative-energy states, approximate boosts of the two-body system, and current conservation, we calculate the electromagnetic form factors of the deuteron up to Q^2 of 4 GeV^2. This is done using a dynamical boost for two-body systems with spin. We first compute form factors in impulse approxmation, but then also add an isoscalar meson-exchange current of pion range that involves the gamma-pi contact operator associated with pseudovector pi-N coupling. We also consider effects of the rho-pi-gamma meson-exchange current. The experimentally measured quantities A, B, and t20 are calculated over the kinematic range probed in recent Jefferson Laboratory experiments. The rho-pi-gamma meson-exchange current provides significant strength in A at large Q^2 and the gamma-pi contact-term exchange current shifts t20, providing good agreement with the JLab data. Relativistic effects and the gamma-pi meson-exchange current do not provide an explanation of the B observable, but the rho-pi-gamma current could help to provide agreement if a nonstandard value is used for the tensor rho-N coupling that enters this contribution.Comment: 15 pages, 10 figures. (v2) Added references on rho-pi-gamma current as well as comparison to recent Novosibirsk data on T20. Implemented \includegraphics in place of \BoxedEPSF. (v3) Modified in order to clarify the nature of the boost we implemented for particles with spin. Other minor changes. Version to be published in Physical Review

Magnescope: Applications in nondestructive evaluation

This paper describes recent results obtained with the Magnescope, which has been used on location in industrial environments and has successfully detected impending fatigue failure, creep damage, applied stress, and microstructural differences. It is concluded that the device provides a useful nondestructive method for evaluating the mechanical properties of materials through the measurement of their structure sensitive magnetic properties