Effect Of Rapid Heating Research Articles

Measurement of the Shrinkage Tension of Melt-spun Fibres with Rapid Heating and Cooling

An investigation is reported in which, to study the effect of rapid heating and cooling on polymeric fibres, constant-geometry isothermal and dynamic shrinkage-tension experiments were designed by using a flexible thermomechanical analyser (FTMA). In isothermal shrinkage-tension experiments, the monofilaments (nylon and PET) were monitored at different setting temperatures over a range of times. The effects of the previous thermal history and different heating rates were also studied. During initial experiments, stress build-up was observed after cooling, and this was shown to be a major instrumental artefact. Shrinkage tension on heating is discussed in terms of the unlocking of frozen-in strains.

Nanosecond Dynamics of Excimer Laser Induced Thermal Decompositon of Thin Polymer Films

AbstractA novel method to study the effect of rapid heating on polymers is presented. Nanosecond time resolved reflectivity measurements of thermal decomposition of poly(3-butenyltrimethylsilane sulfone) (PBTMSS) and polymethylmetacrylate (PMMA) films spun on silicon wafers and irradiated by a pulsed excimer laser at 248 nm are reported. It was found that there exists a critical temperature for effective decomposition. The time scale for thermal decomposition is comparable with the time scales determined for photo-ablation processes. The results indicate that thermal effects are very important in the interaction between polymers and pulsed UV-lasers.

Effect of rapid heating on the nature of short-term rupture strength for steels 28Kh3SNMVFA and 30KhGSA

1. A procedure has been proposed for determining the stress limit for materials with short-term heating (over a few seconds) in the temperature range 673–1173°K. 2. It was established that ultimate strength for steels 28Kh3SNMVFA and 30KhGSA with heating to 873°K for 1 sec exceeds the value determined with a normal heating time of 900 sec by 210 and 170 MPa, respectively.

Superconducting V 3Si produced by pulsed laser annealing

Pulsed laser annealing has been utilized to fabricate superconducting V 3Si from multilayer V-Si thin film samples. It is demonstrated that a single laser pulse can induce mixing to form V 3Si in the A15 phase. The effects of multiple laser pulses and post thermal annealing on the superconducting transition temperature and width are presented, and a model is proposed to explain the effects of rapid heating and cooling on the V 3Si structure.

Effect of Steam Temperature, Speed of Cooling and Cutin Disruption in Steam and Lye Peeling of Apples

ABSTRACTA laboratory model steam peeler was adapted to accept superheated steam and direct injection of cold water in order to study the effect of rapid heating with superheated steam and rapid cooling under partial vacuum on the peeling efficiency of‘Red Delicious’apples. A test was also designed to determine the effect of physical disruption of the cutin layer on the efficiency of caustic peeling. Steam peeling resulted in higher peeled yields and brighter product color than caustic peeling. The peeled yields were 97.5% for superheated steam‐peeled apples with flash cooling, 91.7% for caustic peeled fruit which had a prepeel treatment to physically disrupt the cutin layer, 85.8% for conventionally caustic‐peeled fruit, and 82.7% for the mechanically peeled control.

低炭素マルテンサイト鋼線材の瞬間加熱によるストレイン・テンパリングについて

In the production of prestressed concrete steel wires, a series of the cold drawing-patenting process are performed to improve the strength. In order to reduce cyclic process, the low carbon martensite steel wire which can be produced only by the process of hot rolling and direct quench has been investigated as strain-tempering material. When strain-tempering is performed on the low carbon martensite steel wire, stress relaxation (Re%) increases and mechanical properties such as total elongation, reduction of area, ultimate tensile strength and proof stress decrease remarkably by annealing.In order to shorten the heating time, the authors performed on the steel wire the strain-tempering with a heating time of 1.0 s using direct electrical resistance heating and examined the effects of rapid heating on the stress relaxation and the mechanical properties.Stress relaxation decreases without impairment of the mechanical properties up to a strain-tempering temperature of 573 K.Re (%) after 10.8 ks is 0% at the testing temperature 301 K, 0.49% at 363 K and 1.39% at 433 K.

The effect of rapid heating on the properties of ShKh15 steel in assembling rolling bearing units

The effect of rapid heating on the properties of ShKh15 steel in assembling rolling bearing units

Effect of rapid heating and cooling on the transition from transcrystalline to intercrystalline fracture of low-alloy molybdenum alloys

One of the most dangerous types of f rac ture is in tercrysta l l ine f rac tu re and the metals often susceptible to it are the transit ional meta ls of group UIA. In papers [1-3] the assumption was put forward that the variat ions in the strength of grain boundaries of low-alloy molybdenum alloys is due to the segregat ion of the intersti t ial impuri t ies in the boundary region, or to the fiat boundary segregat ions covering a cons ide r able par t of grain boundaries. In par t icular , the transi t ion f rom t ranscrys ta l l ine to in tercrys ta l l ine f r a c ture has been observed after annealing in a furnace at t empera tures causing the dissolution of boundary segregat ions [3]. During the investigations into the dependence of strength cha rac t e r i s t i c s on s t ruc ture af ter annealing at various t empera tures it was interest ing to hea t t r ea t specimens in this way (e. g . , by rapid heating with subsequent sharp cooling) in o rde r to prevent an intense dissolution of the second phase par t ic les .

急速加熱焼入されたニッケル・クロム・モリブデン浸炭鋼の機械的性質

As the present author reported previously, the surface hardness and toughness of carburized Ni-Cr-Mo steel which was heated rapidly to the optimum austenitizing temperature and quenched afte holding at that temperature for a short time were higher than those of steels which was slowly heated and quenched after holding for a longer time.To invcstigate the reason of the above result, static bending test, rolling-bending fatigue test, investigation of tempering characteristics as well as the metallographic examination in electron microscope were carried out.The results are summarized as follows:(1) The optimum austenitizing conditions for JIS SNCM21 steel carburized to content of 0.73%C are the quenching temperature of 800°, the holding time of 5 minutes, and the minimum heating rate of 30° per minutes.(2) From the results of static bending test and rolling-bending fatigue test, it was found that the beneficial effect of rapid heating and short time holding treatment was very small in steels containing less than 0.50%C.(3) The rapid heating and short time holding result in lower carbon content in martensite, higher Ms temperature and finer austenitic grain size compared with the case of the slow heating and long time holding.(4) Lower carbon martensite with undissolved carbide and fine grain size are attributed to rapid heating and short time holding.From these reasons and analysis of the thermal expansion curves of the specimens of different carbon content, it is clarified that the specimens treated by rapid heating and short time holding can be tempered at lower temperatures than those treated by slow heating and short time holding.

Heat Resistance of Certain Pathogenic Bacteria in Milk Using a Commercial Plate Heat Exchanger

This investigation was undertaken to determine the effect of rapid heating and cooling of milk, with very short holding time, on the thermal resistance of certain organisms important to milk pasteurization. Suspensions of strains of Escherichia coli, Staphylococcus aureus, Streptococcus pyogenes, Corynebacterium diphtheriae, Salmonella typhosa, and Shigella dysenteriae were inoculated into milk which subsequently was processed at varying temperatures with a commercial plate pasteurizer. The pasteurizer was modified slightly to reduce resident heating, holding, and cooling times to a minimum.D values were determined from recovery data for each strain of organisms, and were used to calculate theoretical lethalities by an arbitrary standard of 15 D being equivalent to unit lethality. From these data, it was calculated that a temperature of 82.2C would adequately, pasteurize milk. Milk can be pasteurized successfully by faster rates of heating and cooling, without an intended holding time at temperatures attainable with commercial heat exchangers. However, consideration must be given to rates of heating and cooling milk by individual pasteurizers and to controlling instrument responses in establishing standards.

Diffusion of chromium out of the galvanic layer in iron and steel during rapid electroheating

1. An essential effect of the rate of heating on the course of diffusion of chromium in Armco iron, 45 steel, and has been established. Increasing the rate of heating from 10 deg/min to 3000 deg/sec increases the depth of penetration of chromium atoms (by 2–3 times for iron and by 4–6 times for steel). 2. For all the steels investigated the accelerating effect of rapid heating is the more appreciable the higher the temperature of the process; therefore, with high heating rates it is expedient to use high temperatures as well. 3. When conducting the diffusion processes without holding or with very brief holding (0.5 min), rapid heating should be used only at temperatures greater than 1100–1150°C, since at lower temperatures the diffusion process proceeds more completely under conditions of slow heating. 4. Chromium carbide does not form during diffusion of chromium in 45 and U8 steel. 5. The indicated effect of the rate of heating on the diffusion mobility of chromium in iron and steel is theoretically related to the properties of the austenite structure obtained by rapid heating.

Fatigue Test Result of Large Scaled Test Piece : 1st Report, Induction Hardened Cracked Specimen

The 0.35% carbon steel specimens with crack, whose diameter is 50 mm, were made, and some of them were induction-hardened. The results of comparative tests on them show that the fatigue limit, which is only about 6 kg/mm2 in case of no heat treatment, rises nearly to 40kg/mm2 through induction-hardening. These induction-hardened specimens were rather overheated, so that the rapid heating effect could not be expected, nevertheless their fatigue limit did not remarkably fall. This is presumably due to the residual compressive stress on the surface of specimens. Strain gages were set across the crack and strain variations were measured under both compression and tension loads, respectively. When it is suspected that residual compressive stress is present, the strain is approximately equal under either load, but, when it is not, the strain becomes much larger under tension load. Such phenomenon must originate from the fact that strain at the tip of crack becomes smaller, due to the existence of residual compressive stress and seems to explain one of the main reasons for the increased fatigue limit in the above mentiones results.