Thermodynamic Analysis of the Fracture Inheritance in Overheated Steels

Based on the experimental result that Crand C segregated on the prior grain boundariesof austenite in overheated steels,causing theinheritance of fracture mode after re-austeni-tization,a thermodynamic analysis is conductedthrough the calculation of equilibrium segregationamount of Cr and C in grain boundary at 860and 1050℃ and the segregation kinetics of Cris also calculated.Thermodynamic calculationgives an evidence that the segregation of Crand C at grain boundaries may be regarded asone of the mechanisms of the fracture inheritancein overheated steels.     

Effects of Microstructure on the Tensile, Fracture Toughness and Fatigue Behaviour of Gamma Titanium Aluminides

The effects of microstructure on the deformation and fracture behaviour of two-phase TiAl alloys were investjgated under monotonic and cyclical loading conditions, over a range of temperatu res.The tensile behaviour is analyzed for deformation temperatures between RT and 950℃, Fracture resistance behaviour and toughening mechanisms at RT and 800℃ are analyzed. and the inverse relationship botween ductility and toughness is explained using the crack initiation toughness. The preliminary results of load-controlled fatigue behaviour at 800℃ are interpreted using the tensile behaviour because deformation structure and fracture modes are similar under these two loading conditions     

Prediction of the Inversion Curve and the Maximum Value of μJ–T for Some Refrigerants

In the present work, the thermodynamic states of the inversion curve have been obtained using only p–v–T data. We have also shown a linear relationship between compressibility factor and pressure for each branch of the inversion curve. These lines can be used to find the maximum inversion pressure, P _in ^M . Finally, we have predicted the temperature at which the Joule–Thomson coefficient, _J–T, has its maximum value for each isobar, by using the specific heat capacity, isobaric expansivity, or compressibility factor.     

Scatter Analysis of Fatigue Life and Prediction of S–N Curve

In this study, the effects of salt solution, the presence of notch on fatigue life scatter, and sample size selection for estimation of fatigue life under different probabilities and confidence levels have been investigated. Comparison has been made with smooth specimen tested in air medium. It is seen that notches have significantly higher effect than other factors (salt solutions, smooth geometry, etc.). The minimum number of specimens required for fatigue life estimation within tolerable error, R _o, at different fatigue testing conditions has also been presented both for log normal and Weibull distribution models. It has been found that estimation of fatigue life using Weibull model needs higher sample size than log normal model. Beyond a certain sample size, fatigue life estimation is independent of sample size. The article also presents a method for minimum sample size selection procedure to estimate fatigue life or to draw S?CN curve.     

Biaxiality Dependence of the Fracture Toughness for Glass in Plane Stress State

The fracture behaviour of glass in biaxial stress state has been investigated. Fracture toughness of disk specimen with a straight-through crack was measured under biaxial tension and uniaxial tension loads respectively. The difference between them and the reasons for the difference are discussed. The influence of the stress parallel to crack on fracture of brittle material was demonstrated in theory and experiments. The results show that plane stress fracture toughness of glass is not a material constant. and that the fracture toughness measured in biaxial tension state is higher than that measured under uniaxial tension. The conventional fracture criterion upon the stress intensity factor is questioned in the case of biaxial stress problem, and the strain dependence of crack growth is discussed.     

A New Method for Determining J_(IC) of High StrengthHigh Fracture Toughness Steels by SingleThree Point Bend Specimen

A single three point bend specimen compliance method for determining JIC of high strength high fracture toughness steels is presented and a formula for calculatinff J-integral is proposed as follows.It is simple and valid for high strength high fracture toughness steels. The values of JIC and KIC measured by this method are in good agreement with those measured by standard test method.     

Fracture Toughness and Thermal Shock Properties of Calcium Aluminate Composite with Controlled Duplex Structure

This study used monocalcium aluminate (CaAl2O4,CA) for producing ceramic composites with duplex microstructures by hydration and gelation reactions of the aluminate, and compared the properties with those made by a die-pressing process of mixed powders. Densification of the composite was optimized. The microstructure of sintered bodies, the fracture strengths and toughness of the composites with and without thermal shocking was characterized by different techniques. Experimental results show that the green body with the addition of CA resulted glomerated platelets or uniform distribution of platy CA6 grains. The former, which appeared a duplex microstructure consisted of dense matrix and distributed clusters of CA6 platelets, performed an improvement on toughness and thermal shock resistance. Toughness mechanisms of samples with duplex microstructure are also investigated.     

Value Capture in the Global Electronics Industry: Empirical Evidence for the “Smiling Curve” Concept

This research asks who captures the greatest value in the global electronics industry by testing the concept of the “smiling curve”, which predicts that the greatest value is captured by upstream and downstream firms, and the lowest value is captured in the middle of the value chain. We test the concept using the Electronic Business 300 data-set for 2000–2005. We find that lead firms and component suppliers earn higher gross margins and net margins compared to contract manufacturers. However, the differences are minimal for return on assets (ROA) and return on equity (ROE). We also find that active component suppliers gain higher profits than passive component suppliers. These findings suggest that the smiling curve is right if value is defined in terms of gross margins, but the cost of sustaining a position on either end of the curve is so high that returns on investment are similar across the curve.     

Considerations on the Possibility of “Straightening” the Toe of the Characteristic Curve of Photographie Black and White Negative Materials

Considerations of the possibility of straightening the toe of the characteristic curve of photographie black and white negative materials have suggested the realization of a material which allows the approximate attainment of this effecl. Said material is characterized by the presence in the protective non-photosensitive layer of a colour former. In consequence of a process constituted by the re-halogenation of the image, colour development and image transfer in the auxiliary layer, an effect can be obtaimd which is comparable approximately to a doubling of the original sensitivity.     

Effect of Post-weld Heat Treatment on Microstructure and Fracture Toughness of 30CrMnSiNi2A Steel Welded Joints

The electron beam local post-weld heat treatment (EBLPWHT) is a rather new method that provides the advantages of high precision, flexibility and efficiency, energy saving and higher productivity. This paper studies the effect of two post-weld heat treatment processes on the microstructure, mechanical properties and fracture toughness of an electron beam welded joints in 30CrMnSiNi2A steel. EBLPWHT, in a vacuum chamber, immediately after welding and a traditional furnace whole post-weld heat treatment (FWPWHT) were compared. The experimental results show that, after EBLPWHT treatment, the main microstructure of weld was changed from coarse acicular martensite into lath rnartensite, HAZ was changed from lath martensite, bainite into lower bainite, and base metal was changed from ferrite and pearlite into upper bainite and residual austenite. The microstructures of different zones of joints in FWPWHT condition were tempered sorbite. The properties of welded joints can be improved by the EBLPWHT in some extent, and especially largely for the fracture toughness of welded joints. However the value of fracture toughness of base metal is comparatively low, so appropriate heat treatment parameters should be explored in the future.     

Two-dimensional Model of the Microstructural Evolution in Hot-strip Rolling Processes of C-Mn Steels by Computer Simulations

In the present paper,the two-dimensional comprehensive model,which integrates the temperaturemodel developed by the authors using finite difference methods and microstructural evolutionmodel,has been developed.By using different microstructural evolution equations developed bySellars,Senuma et al.and Easka et al.,the comparison studies have been made,which present that(1) the calculated γ-grain sizes show good agreements with the measured;(2) these equationsshow consistencies at the end of finishing stands.     

Effects of B and Ti on the Toughness of HSLA Steel Weld Metals

Effects of microalloying Ti and B on themicrostructures and low temperature toughness ofmanual metal arc (MMA) deposits were investi-gated.Weld metals containing 200-300 ppm Ti and29-60 ppm B deposited by manual coated elec-trodes provided an optimum low temperaturetoughness.The addition of B in weld metals low-ered the γ→α transformation temperature whichpromoted the acicular ferrite (AF) transformation.Solid solutioned B suppressed grain boundaryferrite as well as side plate ferrite formation andbenefited the acicular ferrite formation.Titaniumprotected B from oxidizing as well as nitriding andformed Ti-Mn silicate inclusions.Ultra-high volt-age electron microscope analyses showed that TiOstructure in the Ti-Mn silicate inclusions was thefavorable nucleation site for acicular ferrite forma-tion.     

On the Origin of the δk-Model and the Model of Plastic Strips

On the basis of a survey of works, we demonstrate the priority of the Lviv school of mechanics in the field of creation and development of the deformation theory of limiting equilibrium of bodies with cracks known as the _k -model. The theory is based on the criterion of crack opening displacement proposed by Leonov and Panasyuk and on the procedure of evaluation of this quantity by modeling the inelastic zones in front of the crack by cuts the edges of which are loaded by certain stresses ₀ whose physical meaning is determined by the properties of the material. This method (known as the model of plastic strips) is also used for the determination of the development of plastic zones at the crack tip for various configurations of plates and loads and also in twisted bodies. The results of numerical calculations agree with the experimental data.     

Prediction of the Occurrence of a Phase in Austenitic Matrix of Ni-base Superalloys Using Thermodynamic Equilibria Calculation

Using the calculation of thermodynamicequilibria in multicomponent systems,two ternaryphase diagrams,Ni-Cr-Mo and Ni-Cr-Co,havebeen calculated by optimizing the Gibbs free ener-gies with respect to phase diagrams andthermodynamic data.On the basis of this calcula-tion,the occurrence of σ-phase in the residual solidsolution of commercial Ni-base superalloys,IN-713C and U-700,has been predicted.The re-sults show that the calculation of phase equilibria issuccessful in the prediction of the occurrence of theσ-phase.     

Factors Affecting the Relation of Fracture Toughness V_(GC) with Critical Void Growth Ratio R_C/R_O

The relationship between fracture toughness VGC and critical void growth RC/RO was studied for ten kinds of Steel. The macroscopic fracture toughness VGC was determined by using notched tensile specimens. and the microscopic parameters of critical void growth ratio RC/RO were quantitatively measured under SEM. Then, the coefhcient C in the relation VGC = C In(RC/RO) proposed in author's past work was specifically explored. The correlation of C with tensile proderty parameter φ=σyδ/(Eφn) was presented for the Steel investigated, and the effects of low temperature on C were also discussed. Results show that the coefficient C is linearly related to the parameter and insensitive to low temperature.     

Sustained Release Matrix of Mebeverine Hydrochloride Using Polyacrylate Resin “Eudragit Retard” Kinetic of Drug Release and Evaluation of a Kinetic Model

Abstract

In this study Eudragit RS PM and RL PM were evaluated as carriers for the preparation of prolonged release solid dispersions of mebeverine hydrochloride by solvent and melting methods. The prepared tablets were examined for dissolution at pH 1.2 and 7.4, Eudragit RS PM and RL PM were found satisfactory as potential slow release carriers. The solid dispersion prepared by the solvent method showed a slow release pattern. Drug release appeared to fit both, first order and Higuchi matrix model kinetics. However, on application of the differential rate treatments, the evidence supported the Higuchi matrix model. Effect of temperatures on dissolution rate was studied for thermodynamic consideration.

The drug release was pH-independent until pH 7.4.As the pH increased, the release was significantly reduced due to solubility problem.     

Fracture analysis of turbine disks and computational–experimental background of the operational decisions

In this paper, fatigue crack growth under operation conditions for rotating disks of aircraft gas turbine engines is analyzed. Initiation and growth of surface cracks for compressor disks made from two-phase titanium alloy has occurred in a disk and blade attachment. Damage accumulation and growth for turbine disks made from steel took place on the inner surface of hole in a hub of wheel. Suggested approach of simulation modeling is used for an analysis and prevention of operation failures of engine rotating components. In the approach described, finite-element models (FEMs) in two and three dimensions were applied to the study of stress–strain state and stress intensity factors for the basic configurations of compressor and turbine disks and their operational damage. Proposed design modifications and repair technologies to existing in-service aircraft gas-turbine engine rotating components are analyzed and substantiated on a static strength and fatigue life basis.