Hysteresis Energy Loss Research Articles

Fracture behavior of polypropylene/ ethylene- diene-terpolymer blends : Effect of temperatures, notch radius and rubber content

The mechanical fracture and ductile-brittle transition (DBT) behavior, hysteresis phenomenon and the plastic zone size of polypropylene (PP) / ethylene-propylene-diene terpolymer (PP/EPDM) blends were investigated by varying EPDM content and notch radius under different temperatures. An increase in test temperature or rubber content in the PP/EPDM blend results in lower yield stress and Young's modulus. The ductile-brittle transition temperature (DBTT) of the notched impact strength decreases with the increase of the EPDM content. However, the DBTT is fairly independent of the notch radius. SEM morphologies of the fracture surfaces indicate that two separate modes, localized and mass shear yielding, work simultaneously in these blends. The plane-strain localized shear yielding dominates the brittle failure at lower temperatures, whereas the plane stress mass shear yielding dominates the ductile fracture at higher temperatures. The presence of EPDM rubber decreases the yield stress of the PP/EPDM blend due to the overlapping stress fields of adjacent particles, resulting in higher hysteresis energy. The relationships among the test temperature, hysteresis loss energy and the size of plastic zone are discussed in detail.

Effect of the coupling between Co and CoO in metal evaporated tapes

In metal evaporated (ME) tapes the interaction between the ferromagnetic Co grains and the antiferromagnetic CoO layer may affect the magnetic behaviour at low temperatures. In fact, when the tapes are cooled from room temperature in the remanence state or in the presence of a strong magnetic field, a shift in the hysteresis cycle is observed. This is an effect of the presence of unidirectional exchange anisotropy, which originates in the exchange coupling between the ferromagnetic and antiferromagnetic phases, and also affects the magnetic behaviour in the presence of a rotating magnetic field. The torque curves have been measured at 80 K. For tapes cooled in the remanence state or in the presence of a strong magnetic field, they show a superposition of sin 2 θ and sin θ torque functions, which indicates the simultaneous presence of the uniaxial anisotropy of the ferromagnetic phase, and of the unidirectional exchange anisotropy. The rotational hysteresis energy loss at 80 K, deduced from the area enclosed in the torque curves, shows anomalous behaviour, with no decrease with increasing field, and also finite values at applied fields larger than the anisotropy field of the ME tapes. This is due to the drag of the ferromagnetic Co moments by the antiferromagnetic CoO exchange-coupled spins during the rotation of the field direction.

Rotational hysteresis in particles for magnetic recording with different switching modes

The rotational hysteresis analysed in fine particles used in magnetic recording media is reported and compared with the expected behaviour for coherent and incoherent cooperative reversal modes. The analysed materials are particles which are modified with the addition of doping ions, which induces an evolution of the magnetization reversal towards more incoherent and heterogeneous mechanisms. The rotational hysteresis energy loss W r and its dependence on the applied field evolve in agreement with the behaviour expected from the evolution of the reversal mode.

Aging monitoring via magnetic property change of pressure vessel materials

The coercive force and magnetic remanence in A533B steel were measured in terms of the magnetic hysteresis energy loss. It was found that magnetic hysteresis energy loss in the tested materials are increased linearly with irradiation fluences of 1017 n/cm 2 range and decreasing with thermal annealing temperature below 1200K. The results can be explained in terms of the influence of pinning mechanisms on magnetic domain structures and these are related to changes in pressure vessel steel mechanical properities. It seems that this techniques can be successfully applied for development of a nondestructive testing method for monitoring of embrittlement in nuclear power pressure vessel materials. Applicability of this method for higher exposure levels is discussed.

Rotational hysteresis and magnetization curling of FeAl thin films obtained by magnetron sputtering

Magnetic characteristics (magnetization, magnetic anisotropy, rotational hysteresis energy loss, rotational hysteresis integral) of Fe 100− x Al x films have been measured (for x = 18.2 and 24.2) to further make clear the effect of atomic ordering on their macroscopic properties. The results are discussed in terms of the presence of a fine-domain DO 3 ordered phase, dispersed within a disordered α matrix. The rotational hysteresis loss dependence W r = f( H) shows a two-peak shape and anisotropy fields have been inferred corresponding to the two phases. The shape anisotropy energy of the dispersed ordered domains (5.5 × 10 7 erg/cm 3), as well as of the matrix (≤ 1.5 × 10 4 erg/cm 3) have been evaluated. The volume fractions of the ordered domains were calculated as 0.19% and 0.23% for x = 18.2 and 24.2 respectively. The experimental results suggest that the changes in magnetization of the investigated films occur mainly by curling mechanism.

A Study of the Durability of a Paper-Based Friction Material Influenced by Porosity

The friction performance and thermal resistance of paper-based oil immersed friction materials are influenced by the material structure formed as a result of the combination of porosity and resiliency. In this paper, the effects of porosity on the thermal durability of paper-based friction materials were studied, of which the contents are varied but the geometries are the same as used in real applications. The relationship between the degree of carbonization and the durability was discussed in several terms of mechanical property changes of the material. The friction and thermal durability tests were conducted by using an SAE No. 2 apparatus under a repeated engage-disengagement condition. To obtain the thermal durability performance the sliding surface temperature was also measured. Coefficients of friction of the low porosity material tend to decrease as the test cycle increases. And the total thickness loss of the low porosity material after durability test is bigger than that of the high porosity material. These durability performances were well correlated with the mechanical and physical property changes of the material, that is, variations of carbonization degree, permeability and hysteresis loss energy.

Rotational hysteresis and magnetic anisotropy of particles for magnetic recording

The rotational hysteresis energy losses have been measured as a function of the applied field in particles for magnetic recording, where the magnetic anisotropy is varied with addition of doping ions (magnetocrystalline anisotropy) or with densification of particles in the assemblies (shape anisotropy). Both the values of the rotational hysteresis and the range of field where the losses occur result strictly related to the magnetic anisotropy and to its evolution.

Effect of glass fiber‐matrix polymer interaction on fatigue characteristics of short glass fiber‐reinforced poly(butylene terephthalate) based on dynamic viscoelastic measurement during the fatigue process

AbstractFatigue behaviors of glass fiber‐reinforced poly(butylene terephthalate) (PBT) were studied based on dynamic viscoelastic measurements during the fatigue process. The fatigue strength of glass fiber‐reinforced PBT was greatly improved by strengthening the interfacial adhesion between glass fiber and matrix PBT. The heat generation rate under cyclic fatigue for PBT reinforced with surface‐unmodified short glass fiber was always larger than that reinforced with surface‐modified short glass fiber because of the large net imposed strain amplitude of PBT matrix which occurred due to the interfacial debonding under cyclic fatigue. A fatigue fracture criterion based on the magnitude of hysteresis energy loss being consumed for a structural change was established for the PBT/short glass fiber composites in consideration of glass fiber‐matrix polymer interfacial interaction. © 1994 John Wiley & Sons, Inc.

The radiation damage and magnetic properties change on nuclear reactor structure materials

In this work we describe an experimental investigation of the effect of neutron irradiation on the magnetic properties change of nuclear pressure vessel materials. The irradiations were carried out in the 1MW open pool reactor at National Tsing Hwa University for various fluence levels up to 10 17 n/cm 2 under neutron energy greater than 0.1 Mev.The experimental results show that there is a linear relation between magnetic hysteresis energy loss with the irradiation dose levels. The magnetic loss factor increases with Vicker microhardness and decreases with thermal annealing temperature. This reduction may be attributed to the formation of tiny void or subgrains which become significant at an higher temperature and higher integrated flux levels.

Magnetization processes in CoNiW films

The torque curves of hard magnetic CoNiW films with perpendicular magnetic anisotropy are analysed. Using the dependence of the rotational hysteresis energy losses on the field, both in the film plane and perpendicular to it, a conclusion is drawn about the magnetic structure of the films and the mechanism of magnetization reversal consisting of an inhomogeneous rotation of the magnetization vector.

The importance of thermo-mechanical properties in the selection of athletic shoe cushioning foams

VALIDATION OF A MATHEMATICAL MODEL OF THE EFFECT OF SOLE ELASTICITY DISTRIBUTiON ON PRONATION Perry Lit and Zvi LadinS iDepartment of Mechanical Engineering, University of California, Berkeley, CA 94720 SBiomedical Engineering Department and NemoMuscular Research Center, Boston University, Boston, MA 02215 Excessive pronation has been cited as a major cause for many musculo-skeletal injuries associated with running. An accurate mathematical model is a useful tool in the design of midsoles in running shoes to prevent excessive pronation. A validation experiment is presented to verify a mathematical model which predicts the effect of the coronal plane elastic distribution in the midsole on pronation and the center of pressure location. The model is based on a rigid body model of the sole obtained via an energy minimization approach presented earlier. Experimental results show that the predictions of both the pronation angles and the center of pressure locations are accurate when the elastic distribution was systematically varied. The model is believed to have the potential of being a useful quantitative tool for engineers and shoe designers. THE IMPORTANCE OF THERMO-MECHANICAL PROPERTIES IN THE SELECTION OF ATHLEI’K SHOE CUSHIONING FOAMS Jeff Poliner, Spencer White, and Mark Fenton Reebok International, Ltd. Material tests have demonstrated that the foams used for cushioning in athletic footwear exhibit a large amount of hysteresis energy loss during impact. Some of this energy is converted to heat, which can modify the stiffness characteristics of the foam. This study was designed to measure the temperature increase in running shoes, to examine its effect on material stiffness during the course of a single exercise bout, and to compare materials with high and low hysteresis. Six subjts ran in shoes constructed with midsoles composed of either EVA or Hytrel foam (I-IF) of similar stiffness, which exhibited approximately half the hysteresis energy loss of the EVA. This teat resulted in an average increase in temperature of 11.7T in EVA and 90°C in HF shoes over the course of a 7.3 km run. testing found a similar rise in temperature, and a significant drop in stiffness (EVA 36%, Mechanical impact HF 11%) over 4ooO cycles. This test also demonstrated that EVA was significantly more sensitive to changes in temperature than HF. These results demonstrate that during a single bout of exercise there is a significant increase in temperature, and a concomitant decrease in stiffness, of foam materials. The increase in temperature appears to be related to mechanical energy losses during impact, since a material with lower hysteresis (Hytrel foam) demonstrated less temperature increase than one with higher hysteresis (EVA). I-IF also demonstrated less sensitivity to changes in temperature. These results indicate that them-to-mechanical behavior should be considered when choosing cushioning materials for use in athletic footwear. SESSION t&CERVICAL SPINE Chairperson: Gary Y amaguchi VERIFICATION OF ANALYTICAL MODELS APPLICABLE TO MOTION ANALYSIS IN THE CERVICAL SPINE. Peter Rootmon, Serge A. Gracovetsky, Gerard J Gouw, Nicholas Newman. Diagnospine Research Inc, Concordia University Departments of Electrical and Mechanical Engineering, Department of Orthopaedic Surgery, Hotel Dieu Hospital, Montreal,Quebec. In recent years, numerous in-vivo and in-vitro studies have been undertaken to quantify the mobility of cervical motion segments. As a result, much of the information required to verify comprehensive analytical models of the cervical spine is now available. A new opto-electronic device has been developed which may be used to help in such verifications. This is a high resolution system which tracks light emitting diodes affixed to the subjects’ skin. Our purpose is to consider some of the existing models and to see how they may be correlated with motion studies. We begin by examining the role of analytical models in studying the entire spine. Then we look at experimental methods employed in modelling of the spine, as well as some specific examples of analytical and physical models which are applicable specifically to the cervical region. We also consider the current state of modelling for the spinal cord. The physical models available do not yet appear to simulate head/neck motion adequately. Hence, entirely accurate predictive injury modelling is not currently possible. Nevertheless, normal and pathological motion can be approximated. Hence motion analysis through tracking of skin markers is expected to be useful in the verification of analytical models. Ti!I 25~6-6 663

Toughening behavior of elastomer‐modified polycarbonates based on the j‐integral

AbstractThe J‐integral method to determine the fracture toughness of tough and ductile polymeric materials previously developed has been applied to the elastomer‐modified polycarbonates. This investigation compares three different methods to obtain Jc: the conventional crack growth length, the stress whitening zone, and the newly developed hysteresis method. Jc values obtained from these three comparative methods are fairly close. The hysteresis method has the advantage over the other two methods of obtaining Jc without requiring the measurement of the crack growth length or the stress whitening zone, therefore avoiding the controversy in defining crack blunting. Results also indicate that the effect of elastomer quantity in polycarbonate on Jc is insignificant as long as the crack is in a stable condition. Higher elastomer contents in polycarbonate result in higher dJ/dΔa, dJ/dΔl, and tearing modulus (Tm). This indicates that the elastomer toughening mechanism is due to the increase of the energy required for crack growth extension. The hysteresis loss energy is directly related to the size of the crack tip plastic zone, and the presence of more elastomer indeed increases the crack tip plastic zone, thus making the polycarbonate tougher. Besides, the presence of elastomer tends to increase the crack initiation displacement and shift the failure modes from an unstable fracture. Jc and the criterion for crack initiation based on rate change of hysteresis energy are discussed in detail.

Hysteresis loop properties of nonoriented Fe-Si alloys

The magnetization curve, hysteresis loop shape and energy loss per cycle have been investigated in nonoriented Fe-Si laminations (3.4 wt% Si, 0.8 wt% Al, 0.2 wt% Mn), from about 5×10 -5 T to 1 T. Evidence is obtained of deviations from the Rayleigh law, as regards both the nonlinear dependence of the permeability on the applied field and the shape of the minor hysteresis loops. A power law dependence of the energy loss per cycle on peak induction W α ( B m) n , with n≌2.2, also in contrast to with Rayleigh law predictions, is found to hold in the investigated induction range.

Effect of polycarbonate molecular weight on precrack hysteresis energy in determining its ductile‐brittle transition

AbstractThe distinctive ductile‐brittle transition behavior of pseudoductile polymeric materials such as polycarbonate (PC) has been discovered to be closely related to the precrack hysteresis loss energy. The higher molecular weight (MW) PC with higher ductility also results in higher precrack hysteresis energy and therefore greater precrack plastic volume under condition of constant loads. If the precrack plastic volume exceeds a critical value, crack initiation thereafter will propagate within the domain of the plastic zone and results in ductile fracture. The deformation displacement is closely related to the precrack plastic volume, and the critical displacement actually determines the critical plastic volume. The higher molecular weight polycarbonate with higher entanglement density is able to withstand earlier crack initiation more effectively. Toughening plastics, such as rubber modification, is simply the result of delaying or retarding the crack initiation and allows the precrack plastic zone to grow over its critical value. A model of crack criterion based on precrack plastic zone is proposed to interpret the ductile‐brittle transition phenomenon.

Hysteresis characteristic analysis of transformer under different excitations using real time measurement

A simplified method for the analysis of hysteresis characteristics in a transformer under nonsinusoidal excitation is discussed. The nonsinusoidal sin m (wt) waveforms are used in the experiments. The hysteresis analysis is treated as a shape identification problem and is solved using the piecewise curve fitting technique. The proposed method uses a real-time data acquisition system, for measurement data and calculates hysteresis loop and loss directly from those data. Expressions for the hysteresis loop and energy loss using the proposed method are shown to agree well with analog measurements. The discrepancy between these two methods is less than 0.65%.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

ROTATIONAL HYSTERESIS MEASUREMENTS ON ALUMITE PERPENDICULAR MEDIA

Rotational hysteresis energy loss measurements have been performed to support the analysis of the magnetization processes of Fe- and Co-alumite perpendicular recording media. Two measurement techniques gave comparable results within error limits. The rotational hysteresis integral is severly lowered by the demagnetizing field. Normalizing the integral with the remanent magnetization instead of the saturation magnetization gives for Fe-alumite values indicating the curling mode, which was also proved by other measurement techniques. The half width value D(1/H)50 is introduced in the rotational loss graph. This value is an estimate for the dispersion of anisotropy axes and in our case it its proportional to the diameter of the Fe-needles. The in-plane loss is very low for the Fe-alumite samples, whereas it is high for the Co-alumite. In the well aligned Fe-alumite, rotation around the easy-axis does not give rise to an energy loss because no anisotropy is present in the rotation plane to cause irreversible magenetization jumps. The crystal anisotropy of fcc-Fe is small compared to the shape anisotropy of the particles. The high in-plane loss measured for Co-alumite is thought to originate from the dispersion of hcp-axes in the Co-needles.

Fatigue Fracture Behavior of Solid-State Extruded High-Density Polyethylene

High-density polyethylene (HDPE) specimens for fatigue experiments were prepared by solid-state extrusion. Variations of dynamic viscoelasticity and surface temperature of the specimen were measured under cyclic fatigue. Fatigue behavior of extruded HDPE showed characteristic features depending on the type of cyclic fatigue. In the case of the fatigue test including compression deformation, extruded HDPE fatigue-fractured via the formation of a kink-band along the maximum shear stress direction. On the other hand, in the case of the pure tension fatigue test, the fatigue fracture surface generated in the normal direction of cyclic straining. The total hysteresis loss energy is divided into the two parts: the energy consumed to fracture the specimen and the energy dissipated as heat under cyclic fatigue. A fatigue fracture criterion based on the magnitude of the hysteresis loss energy consumed for a structural change was established. The fatigue strength of extruded HDPE estimated on the basis of this criterion was high in the cases of pure tension and pure compression fatigue tests, and also, was low in that of the tension-compression fatigue test.

Dynamic and hysteresis losses

A measuring procedure has been developed to determine the hysteresis loss as function of the magnetizing frequency. It was applied to single crystal frames of iron-silicon and tape wound cores of that alloy and metallic glasses. Actually the hysteresis loss energy is frequency dependent and to an extent that must not be neglected if the dynamic loss shall be separated.

The effect of crystal structure of very thin hcp Co-Ni films on the initial magnetization curves and hysteresis loops

Magnetic properties of thin films are strongly influenced by the orientation of the film. In this paper, thin (800 Å) hexagonal Co-Ni films with different textures were studied to understand the effect of film structure on the initial magnetization curves and hysteresis loops. It was found that films with [0002] texture had lower coercivity (∼100–250 Oe depending on grain size) and the energy required to saturate such samples was ∼2–4×106 ergs/cm3. Whereas films with [101̄1] texture had a coercivity of ∼700 Oe and energy required for saturation was ∼107 ergs/cm3. The hysteresis loss (energy of hysteresis) from these samples ranged from 0.6 to 3.5×107 ergs/cm3. It was found that the coercivity and hysteresis loss increases linearly with the magnetization energy. These results were consistent with the measurements on bulk single crystals where the energy required for saturation is smallest for basal plane samples.

Energy loss, anisotropy, magnetoresistivity and recovery in aluminum strained at 4.2 K

High purity aluminum is often considered and sometimes used as the stabilizing material for practical composite superconductors. Such material has a residual resistivity ratio ( RRR = \partial273 K/ \partial4.2 K) in the range 1000 - 5000 when fully annealed. An understanding of how the RRR will change during conductor use is necessary for optimum system design. We have investigated the effects of cyclic plastic strain at 4.2K and annealing to room temperature on the RRR and magnetoresistance of aluminum covering a wide purity range. Measurements of mechanical hysteresis energy loss, anisotropic resistivity and strain induced magnetoresistance are reported. We describe selected experiments and discuss the implications of results on conductor operation.