Results 1 - 10 of 16479
Results 1 - 10 of 16479. Search took: 0.034 seconds
|Sort by: date | relevance|
[en] This invention concerns a device for reducing the thermal stresses of the bottom of a vertical heat exchanger which appear when significant temperature differences occur, in the transient state, between the primary and secondary sodium. This is a double wall around the bottom of the exchanger in which primary sodium flows
[fr]Cette invention concerne un dispositif permettant de reduire les contraintes thermiques du fond d'un echangeur de chaleur vertical, contraintes qui apparaissent lors des differences de temperatures importantes, en regime transitoire, entre le sodium primaire et le secondaire. Il s'agit d'une double paroi entourant le fond de l'echangeur dans laquelle circule du sodium primaire
[en] Precise measurements of bulk-wave ultrasonic velocity in orthogonal directions in samples of the 15Cr2NMFA steel after uniaxial compression (UC) on degree of deformation ε = 0...60% were made. Based on the obtained data and theoretical computations the residual macrostresses (RMS) for different degrees of deformation with taking account of the texture contribution were calculated. The orientation distribution coefficients of crystallites (texture coefficients W4i0) were determined and pole figures were constructed, by which was defined the relative intensity of diffraction lines (Δ/[ijk]) for the main crystallographic directions. The peculiarities in the dependencies of the researched quantities on ε were found and explanations to the observed effects were given
[en] Thermally-induced stress singularities for a strip containing a partially heat conductive crack are investigated, based upon the theory of steady-state plane strain thermoelasticity. The crack is located parallel to the bounding planes of the strip. The Fourier integral transform technique is employed and a set of simultaneous singular integral equations of the first kind is derived. Thermal stress intensity factors are defined in terms of the solutions of the integral equations. Numerical results are obtained to illustrate the effects of partial heat conductance through crack surfaces on the values of stress intensity factors
[en] In most engineering problems, more than one model can be created to represent an engineering system's behavior. Uncertainty is inevitably involved in selecting the best model from among the models that are possible. Uncertainty in model selection cannot be ignored, especially when the differences between the predictions of competing models are significant. In this research, a methodology is proposed to quantify model uncertainty using measured differences between experimental data and model outcomes under a Bayesian statistical framework. The adjustment factor approach is used to propagate model uncertainty into prediction of a system response. A nonlinear vibration system is used to demonstrate the processes for implementing the adjustment factor approach. Finally, the methodology is applied on the engineering benefits of a laser peening process, and a confidence band for residual stresses is established to indicate the reliability of model prediction.
[en] This paper presents a study on the material behaviors and constitutive models of lead at high strain rates. Quasi-static compressive tests and split Hopkinson pressure bar (SHPB) tests were conducted at room temperature. The results of the SHPB tests were verified by high-speed photography, and the error of strain is less than 3% at high strain rate (5000/s). Our results show that the yield stress and flow stress increase at high strain rates. This result indicates that lead is sensitive to the strain rate at high strain rates, but the dependence is not linear during 3000-5000/s. The strain-rate dependence of lead was fitted by a quadratic polynomial curve. To describe the nonlinear strain-rate relationship of lead, modified Johnson–Cook and Cowper–Symonds material models were used to fit the experimental stress–strain curves. The modified Cowper–Symonds model agrees better with the experimental results and can better describe the dynamic mechanical behavior of lead under high strain rates.
[en] The intense development of Taipei City has caused high thermal stress in its urban areas. This study used the urban climatic map (UCmap) and the local climate zone (LCZ) to analyze how land development patterns have affected urban thermal conditions. The UCmap is an efficient tool for obtaining information about urban microclimatic conditions based on urban development parameters and the map provides urban planners with information to mitigate the growing problem of thermal stress. The LCZ is system for classifying urban morphology including land cover, buildings, and vegetation, which can be used to relate land patterns to climate conditions. The results of this study indicate that combining UCmap and the LCZ is helpful for assessing thermal conditions in urban areas, and this approach can be used in many cities to determine the most suitable built environment for mitigating thermal stress.
[en] An extensive development effort has resulted in the successful application of energy absorbers as alternative supports. Several installations of energy absorbers demonstrating the feasibility of this support concept have been successfully completed. Designed in accordance with the ASME Code Case N-420, these ductile supports undergo limited and controlled yielding under dynamic conditions, thereby dissipating energy. The design methodology determines the specific damping ratios applicable for a given piping system on the basis of the energy absorbers used. Thus, using energy absorbers permits predictable damping to be engineered into the system desing. They can be used in operating plants to replace existing snubbers. In plants under construction, they can be used in place of both snubbers and rigid supports. In both applications, fewer energy absorbers are required as compared to snubbers and rigid supports. (orig.)
[en] The structure and mechanical properties of multiphase allows are considered. The behavour of particles which are not amenable to shift deformation such as carbides and nitrides and capable of shift deformation such as finely devided intermetallic compounds are presented. Some approaches to representation about internal stresses are presented. Different mechanisms of strengthening, the processes of high-temperature creep and recrystallization and dependence of mechanical properties of materials on these processes are analyzed
[en] Deep wells have forced the well logging tool designer to design for reliable operation at high temperature and to put as much circuitry as possible into the small space available. To meet this need the designer must have a wide range of semiconductors, passive electronic components, and dielectric materials commercially available. The key point here is commercial availability such that tools can be designed and then manufactured in sufficient quantities to support the expanding field requirements
[en] A mechanical measuring method is presented for inexpensive measuring of internal stresses. The accuracy of the method is assessed by considering a number of errors and is checked by means of comparative measurements. The distributions of internal stresses in depth determined so far are physically plausible. (orig./HP)
[de]Zur kostenguenstigen Messung von Eigenspannungen wird ein mechanisches Messverfahren vorgestellt. Die Verfahrensgenauigkeit wird aufgrund einer Fehlerbetrachtung abgeschaetzt und mit Hilfe von vergleichenden Messungen ueberprueft. Die bisher ermittelten Eigenspannungs-Tiefenverteilungen sind physikalisch plausibel. (orig./HP)