FEM Simulation of Large Diameter Pipe Bending Using Local Heating

With the aid of elastic plastic large deformation finite element method （FEM）, an elastic plastic and cou pling thermo-mechanical model was built to calculate the bending process of the bent pipe, combining with local heating or cooling of the bent pipe. Based on the FEM simulation, the metal deformation during the bending process was analyzed in detail. The thinning and thickening ratio of the pipe wall thickness, the ovality of the cross section of the pipe and the spring back angle, etc. , are presented.

Non-uniform operative temperature distribution characteristics and heat-source-controlled core-area range of local heating radiators

Heating the whole space,which is currently used in northern China,leads to high energy consumption and substantial pollution.A transition to local heating has the potential to help address this problem.In this paper,the effects of radiator-related parameters(position,power,and size)and room-related parameters(aspect ratio and height)on local heating were studied.Two evaluation indices,the effective coefficient of operative temperature(OTEC)and the effective coefficient of local heating(LHEC),were proposed.In addition,the heat source-control core-area(HSCCA)was proposed,and the effect range of heat sources in the space was evaluated by the attenuation of operative temperature.The findings demonstrated that the radiator position has a greater influence on local heating than size.When the position of the radiator was changed from"close to the inner wall"to"close to the outer wall",the LHEC(the interior one-quarter of room is a local heating zone)was found to decrease by 73%.The size of the radiator,which is close to the inner wall,doubled or quadrupled,and the LHEC increased by 9%and 18%.Moreover,rooms with a larger aspect ratio or small room height were found to be the most optimal for local heating applications.The area of the HSCCA decreased as the position of the radiator approached the outer wall.The findings of this study can be used as a design reference for the radiator when the heating mode changes from"full-space heating"to"local heating".

A Study on Heat Transfer Enhancement through Various Nanofluids in a Square Cavity with Localized Heating

A two-dimensional(2D)laminar flow of nanofluids confined within a square cavity having localized heat source at the bottom wall has been investigated.The governing Navier–Stokes and energy equations have been non dimensionalized using the appropriate non dimensional variables and then numerically solved using finite volume method.The flow was controlled by a range of parameters such as Rayleigh number,length of heat source and nanoparticle volume fraction.The numerical results are represented in terms of isotherms,streamlines,velocity and temperature distribution as well as the local and average rate of heat transfer.A comparative study has been conducted for two different base fluids,ethylene glycol and water as well as for two different solids Cu and Al_(2)O_(3).It is found that the ethylene glycol-based nanofluid is superior to the water-based nanofluid for heat transfer enhancement.

Influence of Superathermal Electrons oll Central Plasma Relaxation Oscillations during Localized Electron Cyclotron Heating on the HL-1M Tokamak

During initial studies of ECRH in the HL-1M tokamak, non-standard central MHD activities,such as saturated sawtooth, partially saturated sawtooth, double sawtooth, and the strong m = 1 bursts have been observed while changing the heating location, the ECRH power, the plasma density. Complete suppression of sawtooth is achieved for the duration of the ECRH, when the heating power is applied on the high-field side of low-density plasma, and exceeds a threshold value of power. The m = 1 bursts riding on the ramp phase of sawtooth can only be excited when the ECRH location is near the q = 1 surface on the high field side. The conditions under which the various relaxation activities are produced or suppressed are described. Experimental results imply that the energetic electrons generated during ECRH are responsible for the modification/or stabilization/or excitation of the instability. Near the q = 1 surface, the passing electrons play the role of reducing the shear and tending to stabilize the sawtooth activity, while the barely-trapped electrons play the role of enhancing or driving an internal kink instability.

Simulation Study of IBW Heating in HT-7 Tokamak

Preliminary simulation results obtained with the code developed for ion Bernstein wave （IBW） heating in the HT-7 tokamak are presented. Comparison of the simulation of IBW heating and an HT-7 experiment confirms that using IBW of various frequencies can result in local or global plasma heating. The studies suggest that IBW absorption by ions near the ion cyclotron resonant layer and by electrons via electron Landau damping （ELD） around the maximum of n// offers a possible mechanism of plasma heating.

Effects of Electron Beam Local Postweld Heat Treatment on Microstructure and Properties of 30CrMnSiNi2A Steel Welded Joints

To improve the microstructure and properties of the electron beam welded joints, the vacuum or furnace whole post weld heat treatment (FWPWHT) usually should be done on it. The electron beam local post weld heat treatment (EBLPWHT) is a rather new heat treatment procedure that provides the advantages of high precision, flexibility and efficiency, energy saving and higher productivity. In this paper, the microstructure, mechanical properties, fracture toughness and fatigue properties of electron beam welded joints of 30CrMnSiNi2A steel in as-welded (AW) and EBLPWHT conditions have been investigated respectively. The results show that the microstructures of different zones of joints in as-welded condition are changed by EBLPWHT procedure, in which the welds from coarse needle martensite into lath-shaped martensite; the main structures of heat affected zones (HAZ) from lath-shaped martensite into lower bainite. The properties of welded joints can be improved by the EBLPWHT in some extent, especially the fracture toughness of the welds and the fatigue crack resistance of welded joints can be sufficiently improved. However, more appropriate heat treatment parameters of the EBLPWHT have to be studied in order to increase the mechanical properties of base metal near by the HAZ.

Temperature field analysis of main steam pipe under local post weld heat treatment

In local post weld heat treatment, the temperature difference is the criterion of the process. The temperature field in the main stream pipe under local post weld heat treatment is simulated by finite element method. A close-loop control program is designed to simulate the temperature field of two different pipes. Both the skin effect of induction heating and electro-thermal coupled effect are considered in the heating model. The local heat treatment temperature difference at the inner and outer side of the pipe is analyzed and the different convection conditions are also considered. The simulation results show that in appropriate induction heating process, the temperature difference in the pipe can be controlled within 30 ℃.

GLOBAL BLOW-UP FOR A HEAT SYSTEM WITH LOCALIZED SOURCES AND ABSORPTIONS

In this paper there are established the global existence and finite time blow-up results of nonnegative solution for the following parabolic system ut = △u ＋ v^P（x0, t） - au^τ, x ∈ Ω, t 〉 0, △u ＋ v^P（x0, t） - bu^τ, x ∈ Ω, t 〉 0 subject to homogeneous Dirichlet conditions and nonnegative initial data, where x0 ∈ Ω is a fixed point, p, q, r, s ≥ 1 and a, b 〉 0 are constants. In the situation when nonnegative solution （u, v） of the above problem blows up in finite time, it is showed that the blow-up is global and this differs from the local sources case. Moreover, for the special case r = s = 1, lim t→T＊（T＊-t）^p＋1/pq-1u（x,t）=（p＋1）^1/pq-1（q＋1）^p/pq-1（pq-1）^-p＋1/pq-1, lim t→T＊（T＊-t）^q＋1/pq-1u（x,t）=（p＋1）^1/pq-1（q＋1）^p/pq-1（pq-1）^-p＋1/pq-1 are obtained uniformly on compact subsets of/2, where T＊ is the blow-up time.

NUMERICAL ANALYSIS OF RESIDUAL STRESSES IN TITANIUM ALLOY DURING ELECTRON BEAM LOCAL POST-WELD HEAT TREATMENT

The distributions of temperature and residual stresses in thin plates of BT20titanium alloy are numerically analyzed by three-dimensional finite element software duringelectron beam welding and electron beam local post-weld heat treatment (EBLPWHT). Combined withnumerical calculating results, the effects of different EBLPWHT mode and parameters, including heattreating position, heating width and heating time, on the distribution of welding residual stressesare analyzed. The results show that, the residual tensile stresses in weld center can be largelydecreased when the weld is heat treated at back preface of the plate. The numerical results alsoindicated that the magnitude of the residual longitudinal stresses of the weld and the zone vicinityof the weld is decreased, and the range of the residual longitudinal stresses is increased alongwith the increase of heating width and heating time.

Investigation of influence of local cooling/heating on nonlinear instability of high-speed boundary layer with direct numerical simulations

The influence of local cooling/heating on two types of nonlinear instabilities of the high-speed boundary layer,namely,the First and Second Mode Oblique Breakdown(FMOB and SMOB),is studied using direct numerical simulations.Local cooling and heating are performed at the weak and strong nonlinear stages of the two types of nonlinear instabilities.It is found that for the FMOB,local cooling at the weak nonlinear region will suppress the increase of the fundamental mode,leading to transition delay.Opposite to local cooling,local heating at the weak nonlinear region of the FMOB will promote the growth of the fundamental mode,resulting in the occurrence of more upstream transition onset.However,if local cooling and heating are performed at the strong nonlinear region,the influence of both local cooling and heating on the FMOB can be neglected.Remarkably,both local heating and cooling can delay the SMOB for different mechanisms.Performing local cooling at the weak nonlinear region of the SMOB,the low amplitude of higher spanwise wavenumber steady mode caused by local cooling lies behind transition delay.When local cooling is set at the strong nonlinear region,the low amplitude of harmonic modes around the cooling area can cause transition delay.Additionally,local heating will suppress the SMOB for the slowing amplification rate of various modes caused by the local heating at both the weak and strong nonlinear stages of the SMOB.

Tailoring of Mechanical Properties of Indirect Hot Stamping Steel Tubes by Laser Assisted Local Rapid Heating

The effect of laser assisted local heating on the mechanical properties of a hot stamping steel tube was in vestigated. A heated region with a spiral shape was generated on the surface of the tube by combining the linear movement of the laser and the rotation of the tube. The results of axial crush tests show that the laser assisted local heating can be effectively used to modify the mechanical performance of the tube. A microstructural analysis confirms that the laser locally induces a martensitic phase transformation in the heated region and results in inhomogeneous microstructures alon- the length of the tube.

A Test Method for Torsion Strength of Refractory Materials at Elevated Temperatures

New apparatus for the determination of torsion strength of refractory materials at elevated temperatures has been developed in this work. With the employment of heating wire and induction heating unit,this device can carry out torsion strength test at high temperatures at the heating rate ranging from 10 ℃/min to 200 ℃/min.Torsion strength of high alumina brick,magnesia brick and Si3 N4 bonded SiC brick has been tested at different heating rates of 10 ℃/min,100 ℃/min and 200℃/min,separately. Results indicate that,for high alumina brick,the tested torsion strength at the heating rate of 10 ℃/min is very close to that at 100 ℃/min,but very different from that at 200 ℃/min. The tested torsion strength of magnesia brick at different heating rates differs greatly,while that of Si3 N4 bonded SiC brick is similar. This suggests that the structure of refractory materials with poor thermal shock resistance might be damaged when the heating rate of 200 ℃/min was applied,but the heating rate of 100 ℃/min is possible for a lot of refractory products. At fast heating rates,it takes only1 h to finish a test at elevated temperatures,thus saving a lot of time and energy.

Evaluation of microvascular reactivity with laser Doppler flowmetry in chronic kidney disease

Cardiovascular diseases are the major causes of mortality in patients with chronic kidney disease(CKD).The complex process of accelerated athero- and arteriosclerosis in CKD is associated with this phenomenon,where endothelial dysfunction(ED) is one of the initial steps. Hence, the early diagnosis of ED can potentially lead to early interventions which could result in a better outcome for these patients. Several methodologies have been developed for the diagnosis of ED. Laser Doppler flowmetry(LDF) enables us to study the microcirculation continuously in a non-invasive manner. In our review we would like to focus on different tests developed for LDF, like postocclusive reactive hyperaemia,local heating, iontophoresis, microdialysis or analysis of flowmotion. We would also like to summarize the available data in CKD with these methodologies to enlighten their perspectives in the clinical use on this patient population.

3D Finite Element Numerical Simulation of Residual Stresses on Electron Beam Welded BT20 Plates

A three-dimensional finite-element model (FEM) used for calculating electron beam (EB) welding temperature and stresses fields of thin plates of BT20 titanium has been developed in which the nonlinear thermophysical and thermo-mechanical properties of the material has been considered. The welding temperature field, the distributions of residual stresses in as-welded (AW) and electron beam local post-weld heat treatment (EBLPWHT) conditions have been successfully simulated. The results show that: (1) In the weld center, the maximum magnitude of residual tensile stresses of BT20 thin plates of Ti alloy is equal to 60%- 70% of its yield strength σs. (2) The residual tensile stresses in weld center can be even decreased after EBLPWHT and the longitudinal tensile stresses are decreased about 50% compared to joints in AW conditions. (3) The numerical calculating results of residual stresses by using FEM are basically in agreement with the experimental results. Combined with numerical calculating results, the effects of electron beam welding and EBLPWHT on the distribution of welding residual stresses in thin plates of BT20 have been analyzed in detail.

Microstructure and fatigue crack growth behaviour of electron beam welding in 30CrMnSiNi2A steel

The effects of two post-weld heat treatment processes on the microstructure and fatigue properties of the electron beam welded joints of 30CrMnSiNi2A steel were studied. Electron beam local post-weld heat treatment (EBLPWHT), in a vacuum chamber, immediately after welding and a traditional furnace whole post-weld heat treatment (FWPWHT) were accepted. The experimental results show that, after EBLPWHT, the main microstructure of weld is changed from coarse acicular martensite into lath martensite, and base metal is changed from ferrite and perlite into upper bainite and residual austenite, however the microstructures of different zones of joints in FWPWHT conditions are tempered sorbite. The fatigue crack growth rate da/dN of welds and base metal are not obviously changed among EBLPWHT, FWPWHT test and as-welded (AW) test, as the mechanical properties of materials have a certain but not large effect on the da/dN of welded joints. The resistance to near threshold fatigue crack growth data of welded joints can be largely improved by EBLPWHT and it is related to microstructure and crack closure effect.

Numerical Study on the Stress–Strain Cycle of Thermal Self-Compressing Bonding

Thermal self-compressing bonding(TSCB) is a new solid-state bonding method pioneered by the authors. With electron beam as the non-melted heat source, previous experimental study performed on titanium alloys has proved the feasibility of TSCB. However, the thermal stress–strain process during bonding, which is of very important significance in revealing the mechanism of TSCB, was not analysed. In this paper, finite element analysis method is adopted to numerically study the thermal elasto-plastic stress–strain cycle of thermal self-compressing bonding. It is found that due to the localized heating, a non-uniform temperature distribution is formed during bonding, with the highest temperature existed on the bond interface. The expansion of high temperature materials adjacent to the bond interface are restrained by surrounding cool materials and rigid restraints, and thus an internal elasto-plastic stress–strain field is developed by itself which makes the bond interface subjected to thermal compressive action. This thermal self-compressing action combined with the high temperature on the bond interface promotes the atom diffusion across the bond interface to produce solid-state joints. Due to the relatively large plastic deformation, rigid restraint TSCB obtains sound joints in relatively short time compared to diffusion bonding.

Pulsed-Laser Annealing of NiTi Shape Memory Alloy Thin Film

Local annealing of amorphous NiTi thin films was performed by using an Nd：YAG 1064 nm wavelength pulsed laser beam. Raw samples produced by simultaneous sputter deposition from elemental Ni and Ti targets onto unheated Si （100） and Silica （111） substrates were used for annealing. Delicate treatment with 15.92 W/mm^2 power density resulted in crystallization of small spots; while 16.52 and 17.51 W/mm^2 power densities caused ablation of the amorphous layer. Optical microscopy, scanning electron microscopy, X-ray diffraction and atomic force microscopy were performed to characterize the microstructure and surface morphology of the amorphous/crystallized spot patterns.

Novel Analytical Thermal Performance Rate Analysis in ZnO-SAE50 Nanolubricant: Nonlinear Mathematical Model

The investigation of local thermal transport rate in the nanolubricants is significant.These lubricants are broadly used in environmental pollution,mechanical engineering and in the paint industry due to high thermal performance rate.Therefore,thermal transport in ZnO-SAE50 nanolubricant under the impacts of heat generation/absorption is conducted.The colloidal suspension is flowing between parallel stretching disks in which the lower disk is positioned at z=0 and upper disk apart from distance d.The problem is transformed in dimensionless version via described similarity transforms.In the next stage,an analytical technique(VPM)is implemented for the solution purpose.The graphical results against multiple flow parameters were furnished over the region of interest and explained comprehensively.It is imperative to mention that the results are plotted for ZnO-SAE50 and conventional liquid as well.Further,rapid motion of the fluid is perceived against high Reynolds andγparameters.The wall shear stresses at the upper end rises for multiple Reynolds andγwhile;decrement is detected at the lower end.The significant contribution of an internal heat source is noted for thermal performance rate at the upper end.Foremost,the local heat transport rate declines at the lower disk.By altering Reynolds number,prompt heat transfer rate is gained at the upper disk and increasing behavior of the local heat transport rate is slow at the lower disk.From the study,it is concluded that the nanolubricants have high thermal characteristics.Therefore,such fluids are reliable to use in above stated areas.

Hyperthermia: Clinical Applications and Theoretical Models

Nanotechnology applications, which aid radiotherapy and chemotherapy, have revolutionized diagnosis, treatment planning, imaging, and medical machinery. The ability of nanoparticles to kill or freeze cancer cells by raising heat locally is a prominent application of nanoparticles. This paper will review the research on clinical applications of hyperthermia using nanoparticles stimulated by an alternating magnetic field and electromagnetic waves such as microwave and laser, as well as the foundation of the theoretical model used in bio-thermal applications.

Droplet Deposition Pattern Affected by Different Heating Directions

The coffee ring effect commonly exists in droplet deposition patterns,which fundamentally affects scientific research and industrial applications,like pharmaceutical purification,salt manufacturing,etc.Some researchers have tried different solutions to control the distributions of droplet deposition patterns,but most control deposits by adjusting droplet characteristics.In this work,droplet deposition patterns with different wettability are investigated by both localized and substrate heating.A whole process of droplet evaporation is recorded.The droplet generally evaporates from Constant Contact Radius(CCR)mode to Constant Contact Angle(CCA)mode,and CCR stage occupies the most of time.Experimental results show that,without any chemicals,laser induced local heating transitions particle deposition patterns from ring-like structure to dot-like patterns on a hydrophilic surface,driving most saline solvent to the center.Meanwhile,a hydrophobic surface is also investigated showing that the particles tend to assemble at the central area,but the pattern is slightly different compared to that on hydrophilic surface.In addition,physical mechanisms of local heating and heating from substrate are also explored.