scholarly journals The specific heat loss combined with the thermoelastic effect for an experimental analysis of the mean stress influence on axial fatigue of stainless steel plain specimens

2014 ◽  
Vol 8 (30) ◽  
pp. 191-200
Author(s):  
G. Meneghetti ◽  
M. Ricotta ◽  
B. Atzori
Keyword(s):  
Stainless Steel ◽  
Specific Heat ◽  
Heat Loss ◽  
Experimental Analysis ◽  
Mean Stress ◽  
Thermoelastic Effect ◽  
The Mean ◽  
Stress Influence ◽  
Axial Fatigue

scholarly journals Bakerian Lecture :─On the variation of the specific heat of water, with experiments by a new method

1912 ◽  
Vol 86 (587) ◽  
pp. 254-257 ◽  
Keyword(s):  
Specific Heat ◽  
Experimental Evidence ◽  
Electric Current ◽  
Heat Loss ◽  
Mean Value ◽  
Mechanical Method ◽  
Order Of Accuracy ◽  
Steady Current ◽  
Differential Pair ◽  
The Mean

The question of the variation of the specific heat of water is so fundamental in calorimetry, and the results of different observers and different methods are still so discordant, that no apology is needed for the publication of fresh experimental evidence. The continuous electric method, which I carried out in conjunction with Prof. Barnes, was specially designed to avoid the main sources of error of the older methods in which mercury thermometers and open calorimeters were employed. In this method. the rise of temperature of a steady current of water, heated by a steady electric current in its passage through a fine tube hermetically scaled in a vaccumjacket, was observed with a differential pair of platinum thermometers. Errors due to lag, or to uncertainty of water-equivalent, or to evaporation or heat-loss in transference, were thus eliminated, and a higher order of accuracy was secured in the temperature measurements. The results of the continuous electric method in the case of water showed a variation of specific heat amounting to less than one half of 1 per cent. between 10° and 80°C., with a minimum at 37.6°C., followed by a very slow and steady rise. The mean value from 0° to 100°C. agreed to 1 in 2000 with the experiments of Reynolds and Moorby by the mechanical method, and the values from 5° to 35° C. agreed to a similar order of accuracy with the experiments of Rowland. But the value at 80°C. was 1 per cent. lower than that found by Lüdin's (Zürich, 1895), employing the ordinary method of mixture with an open calorimeter and mercury thermometers. Lüdin's results for the variation over the range 30° to 100°C. agreed more closely with the continuous electric method than those of any previous observers; but showed a minimum at 25°C., and a maximum at 87°C., which could not be reconciled with the experiments of Reynolds and Moorby on the mean specific heat from 0° to 100°C., or with the most probable reduction of Regnault's experiments between 110° and 190°C.

scholarly journals A recording calorimeter for explosions

1907 ◽  
Vol 79 (528) ◽  
pp. 138-154 ◽  
Keyword(s):  
Specific Heat ◽  
Heat Loss ◽  
Practical Importance ◽  
Copper Strip ◽  
Gas Engine ◽  
Coal Gas ◽  
Engine Cylinder ◽  
Solid Explosives ◽  
The Mean

The determination of the rate of loss of heat to the walls of a vessel after an explosion within it is a matter of considerable scientific interest and of practical importance. Hitherto such determinations, if we except the recent work of Dugald Clerk on the loss of heat in the gas engine cylinder, have been based upon a study of the fall of pressure during the cooling of the gases after the explosion. From the pressure the mean temperature can be deduced, and thence, if the specific heat is known, can be found the rate of heat loss at any moment. Such a calculation is, however, obviously unsatisfactory, because the only available values of the specific heat of gases at temperatures above 1500° are based upon explosion experiments, and involve doubtful assumptions as to the amount of loss before combustion is complete. Some means of determining the loss of heat at any instant without any knowledge of specific heat is therefore essential, both for finding the law of cooling of hot gases confined in a closed vessel and for placing on a satisfactory basis the specific heat values obtained from explosion experiments. I have devised a simple means of doing this which appears to be capable of considerable accuracy. It consists essentially in lining the explosion vessel as completely as possible with a continuous piece of copper strip and recording the rise of resistance of the copper strip during the progress of the explosion and the subsequent cooling. Knowing the temperature of the copper and its capacity for heat, the heat that has flowed into it from the gas may be calculated from the resistance, certain corrections being applied for the heat which the copper has lost to the insulating backing. Up to the present I have only used the apparatus for the investigation of the loss of heat after an explosion of coal gas and air, but it might, I think, be applicable, with certain modifications, to finding the heat loss during and after the combustion of solid explosives.

Mean Stress Effect on Fatigue Properties of Type 316 Stainless Steel: Part II — In PWR Primary Water Environment

2017 ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Effective Strain ◽  
Strain Range ◽  
Stress Effect ◽  
Mean Stress ◽  
316 Stainless Steel ◽  
Mean Stress Effect ◽  
Primary Water ◽  
The Mean

The mean stress effect on the fatigue life of Type 316 stainless steel was investigated at 325°C in simulated PWR primary water. It was shown that, as shown in high-temperature air environment, the fatigue life was extended by applying the mean stress under the same stress amplitude. An increase in the maximum peak stress by applying the mean stress induced additional plastic strain and this hardened the material. On the other hand, the fatigue life was shortened by the mean stress for the same strain range. The ratcheting strain caused by applying mean stress accelerated crack mouth opening and reduced fatigue life. It was also shown that the fatigue life in the simulated PWR primary water was shorter than that in air even without the mean stress. The magnitude of the reduction depended on the strain range. The reduction in fatigue life was the maximum when the strain range was 0.6%. The environmental effect disappeared when the effective strain was less than 0.4%.

scholarly journals Influence of Second-Order Effects on Thermoelastic Behaviour in the Proximity of Crack Tips on Titanium

2021 ◽  
Author(s):  
D. Palumbo ◽  
R. De Finis ◽  
F. Di Carolo ◽  
J. Vasco-Olmo ◽  
F. A. Diaz ◽  
...  
Keyword(s):  
Crack Tip ◽  
Thermoelastic Stress ◽  
Qualitative Evaluation ◽  
Second Order ◽  
Order Effects ◽  
Mean Stress ◽  
Thermoelastic Effect ◽  
Crack Tips ◽  
The Mean ◽  
Second Order Effects

Abstract Background The Stress Intensity Factor (SIF) is used to describe the stress state and the mechanical behaviour of a material in the presence of cracks. SIF can be experimentally assessed using contactless techniques such as Thermoelastic Stress Analysis (TSA). The classic TSA theory concerns the relationship between temperature and stress variations and was successfully applied to fracture mechanics for SIF evaluation and crack tip location. This theory is no longer valid for some materials, such as titanium and aluminium, where the temperature variations also depend on the mean stress. Objective The objective of this work was to present a new thermoelastic equation that includes the mean stress dependence to investigate the thermoelastic effect in the proximity of crack tips on titanium. Methods Westergaard’s equations and Williams’s series expansion were employed in order to express the thermoelastic signal, including the second-order effect. Tests have been carried out to investigate the differences in SIF evaluation between the proposed approach and the classical one. Results A first qualitative evaluation of the importance of considering second-order effects in the thermoelastic signal in proximity of the crack tip in two loading conditions at two different loading ratios, R = 0.1 and R = 0.5, consisted of comparing the experimental signal and synthetic TSA maps. Moreover, the SIF, evaluated with the proposed and classical approaches, was compared with values from the ASTM standard formulas. Conclusions The new formulation demonstrates its improved capability for describing the stress distribution in the proximity of the crack tip. The effect of the correction cannot be neglected in either Williams’s or Westergaard’s model.

Mean Stress Effect on Fatigue Properties of Type 316 Stainless Steel in Pressurized Water Reactors Primary Water Environment

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Water Environment ◽  
Stress Effect ◽  
Mean Stress ◽  
Pressurized Water ◽  
316 Stainless Steel ◽  
Mean Stress Effect ◽  
Primary Water ◽  
The Mean

The mean stress effect on the fatigue life of type 316 stainless steel was investigated in simulated pressurized water reactor (PWR) primary water and air at 325 °C. The tests in air environment have revealed that the fatigue life was increased with application of the positive mean stress for the same stress amplitude because the strain range was decreased by hardening of material caused by increased maximum peak stress. On the other hand, it has been shown that the fatigue life obtained in simulated PWR primary water was decreased compared with that obtained in air environment even without the mean stress. In this study, type 316 stainless steel specimens were subjected to the fatigue test with and without application of the positive mean stress in high-temperature air and PWR water environments. First, the mean stress effect was discussed for high-temperature air environment. Then, the change in fatigue life in the PWR water environment was evaluated. It was revealed that the change in the fatigue life due to application of the mean stress in the PWR water environment could be explained in the same way as for the air environment. No additional factor was induced by applying the mean stress in the PWR water environment.

Influence of Mean Strain on Fatigue Life of Stainless Steel (Effect of Constant and Ratcheting Mean Strain)

2014 ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Effective Strain ◽  
Mouth Opening ◽  
Strain Range ◽  
Fatigue Tests ◽  
Mean Stress ◽  
Crack Mouth ◽  
The Mean ◽  
Mean Strain

The influence of mean strain on fatigue life was investigated for Type 316 stainless steel at room temperature in ambient environment. Two types of mean strain were simulated in the fatigue tests: constant and increasing (ratcheting) mean strains. In order to apply the constant mean strain, prestraining was induced prior to fatigue tests. Although the stress amplitudes became larger due to the prestraining, fatigue lives were almost the same as those obtained using non-prestrained specimens for the same strain range. Change in the maximum peak stress and stress amplitude due to the prestraining had little influence on the fatigue life. It was shown that the mean strain showed little influence on the fatigue life under the same strain range. The ratcheting mean strain was observed during the fatigue tests under mean stress. The fatigue life was reduced by applying the mean stress for the same strain range. The degree of the reduction was increased with the magnitude of the ratcheting mean strain. It was deduced that the increasing mean strain enhanced the crack mouth opening and increased the effective strain range. It was concluded that the ratcheting mean strain reduced the fatigue life for the same strain range, and the reduction in fatigue life could be predicted conservatively by assuming the crack mouth was never closed during the fatigue tests.

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