scholarly journals High-frequency fatigue tests

1925 ◽  
Vol 109 (749) ◽  
pp. 119-143 ◽  
Keyword(s):  
Mild Steel ◽  
High Frequency ◽  
High Speed ◽  
Fatigue Testing ◽  
National Physical Laboratory ◽  
Fatigue Tests ◽  
Research Committee ◽  
Engineering Research ◽  
Physical Laboratory ◽  
The Cost

The experiments on high-frequency fatigue in copper, Armco iron, and mild steel described in the following paper were carried out in the Engineering Laboratory, Oxford, for the Fatigue Panel of the Aeronautical Research Committee. The cost of the apparatus was defrayed by a grant from the Engineering Research Board of the Department of Scientific and Industrial Research. In 1911 Prof. B. Hopkinson called attention to the importance of ascertaining whether the fatigue limit of metals was dependent on the rate of alternation of stress. He designed and made an electric alternating directstress machine, and published the results of tests on mild steel carried out at about 7,000 periods per minute (116 per second), which was more than three times as fast as any tests made up to that time. The results at this speed were compared with those made by Dr. Stanton at the National Physical Laboratory on the same material at 2,000 periods per minute (33 per second). Prof. Hopkinson considered that the results showed that speed had a marked effect, but he did not consider that his tests were conclusive. In the light of the knowledge gained on fatigue testing since that date neither set of tests can be considered satisfactory. The question is of importance to the users of high-speed machinery. It is also of importance when comparisons are made between tests carried out at different speeds, and, finally, it has a bearing on the causes of fatigue failure. For these reasons it appeared to be desirable to make a more thorough investigation, and, if possible, to extend the tests to very much higher speeds.

Development of a New Fatigue Testing Machine for High Frequency Fatigue Damage Assessment

2013 ◽  
Author(s):  
Naoki Osawa ◽  
Tetsuya Nakamura ◽  
Norio Yamamoto ◽  
Junji Sawamura
Keyword(s):  
High Frequency ◽  
High Speed ◽  
Fatigue Testing ◽  
Low Cost ◽  
Plate Thickness ◽  
Testing Machine ◽  
Fatigue Tests ◽  
Frequency Effect ◽  
Wave Load ◽  
Out Of Plane

A new simple fatigue testing machine, which can carry out fast and low-cost fatigue tests of welded joints subject to wave with high frequency vibration, has been developed. This machine is designed for plate bending type fatigue tests, and wave load is applied by using motors with eccentric mass. Springing vibration is superimposed by attaching an additional vibrator to the test specimen, and whipping vibration is superimposed by an intermittent hammering. Fatigue tests which simulate springing and whipping by a conventional servo-type fatigue testing machines are very expensive and use a large amount of electricity. If one uses these conventional machines, it is difficult to simulate superimposed stress wave forms at high speed, and it takes long hours of testing to examine the high frequency effect. In contrast, it is found that fatigue tests can be carried out in fast, i.e. waves with 10Hz or higher frequency for out-of-plane gusset welded joint specimens with 12mm plate thickness by using the developed machine. The electricity to be used for fatigue tests could be minimal, for example one thousandth of that needed for conventional machines. These results demonstrate the superiority of the developed machine.

Large-Scale Torsional Fatigue Testing of Marine Shafting

1948 ◽  
Vol 159 (1) ◽  
pp. 399-415 ◽  
Author(s):  
S. F. Dorey
Keyword(s):  
Large Scale ◽  
Fatigue Testing ◽  
Testing Machine ◽  
National Physical Laboratory ◽  
Fatigue Tests ◽  
Torsional Fatigue ◽  
Physical Laboratory ◽  
Stationary Test ◽  
New Type ◽  
Stress Fatigue

The paper describes the design and construction of a new type of torsional fatigue testing machine of the resonance type capable of generating a reversed harmonic torque of up to ±3 × 106 lb.-in. in a stationary test shaft, at a frequency of approximately 2,500 vibrations per minute. Reference is made to a specially developed electronic method of speed control capable of regulating the nominal stress in the specimen to within one per cent. The paper includes the results of a number of fatigue tests carried out on 9 3/4-inch diameter mild steel shafts, and also on “Meehanite” cast-iron specimens of 6 inches diameter, and concludes with some remarks on scale effect, based on results from 1/2-inch diameter specimens subjected to reversed torsional fatigue tests carried out on a combined-stress fatigue testing machine at the National Physical Laboratory.

scholarly journals A high-speed fatigue-tester, and the endurance of metals under alternating stresses of high frequency

1912 ◽  
Vol 86 (584) ◽  
pp. 131-149 ◽  
Keyword(s):  
High Speed ◽  
Early Stage ◽  
National Physical Laboratory ◽  
Fatigue Tests ◽  
General Nature ◽  
Wrought Iron ◽  
Physical Laboratory ◽  
The Subject ◽  
Algebraic Difference ◽  
The Mean

The deterioration of metals under the action of stress varying rapidly between fixed limits has keen the subject of much experimental investigation. It is found that the important factor in the rate at which this "fatigue" goes on is the algebraic difference of the limits between which the stress varies, usually called the "range of stress"; and that the absolute position of these limits matters little, provided, of course, that the mean stress is not too large. The number of applications of a given range of stress required to fracture the piece increases as the range is diminished, the general nature of the relation between the two being as shown in the curve (fig. 1), which represents the results of a series of tests made by Dr. Stanton on mild steel. In these observations the stress alternated between compression and tension, the ratio of the compression and tension limits being 1·09. The form of the curve suggests that a range of stress not much below 25 tons, which in an average specimen would just cause fracture alter a million reversals, could never break the bar, however often applied. One of the chief objects of the fatigue tests hitherto made has been to discover tins "limiting range." At an early stage in these investigations the question was raised whether the endurance by the material of a given cycle of stress is affected by the rate of repetition of the cycle. Besides its intrinsic interest, tins question is of importance because on the answer to it depends the possibility of reducing the excessive amount of time taken to carry out fatigue tests. The determination within a few per cent, of the limiting range requires several separate tests in which the cycle is repeated at least a million times, and even that number is not always sufficient to give a reasonably close approximation. Wöhler worked with 60 to 80 reversals per minute, and he found that the same wrought iron which could just sustain a million applications of a range of 23 tons broke after 19 million repetitions of a range of 17½ tons. The more recent machines have keen run at much higher speeds, and there is now a machine of the Wöhler type at the National Physical Laboratory which gives 2000 cycles of bending stress per minute. Even at this speed, which I believe is the highest yet reached under conditions admitting of accurate measurement, it takes eight hours to do a million reversals.

scholarly journals VIII. Gaseous combustion at medium pressures. Part I. —Carbon monoxide air explosions in a closed vessel. Part II. —Methane-air explosions in a closed vessel

1926 ◽  
Vol 225 (626-635) ◽  
pp. 331-356 ◽  
Keyword(s):  
Carbon Monoxide ◽  
National Physical Laboratory ◽  
Closed Vessel ◽  
Engineering Research ◽  
The Past ◽  
Physical Laboratory ◽  
Wide Range ◽  
The Subject ◽  
Temperature And Pressure ◽  
Air Explosion

During the past five years a programme of research involving air-fuel explosions in a closed vessel has been in progress at the National Physical Laboratory for the Engineering Research Board of the Department of Scientific and Industrial Research. Among the experimental results obtained, those relating to Carbon Monoxide and Methane were considered likely to be of interest to the Society, and form the subject of the present communication. Of the two investigations described, the first gives experimental data on the respective influences of hydrogen-air and water vapour on a carbon monoxide-air explosion, and the second relates to explosions of methane and air over a comparatively wide range of initial temperature and pressure.

The Thermal Rating of Worm Gearboxes

1944 ◽  
Vol 151 (1) ◽  
pp. 326-337 ◽  
Author(s):  
Harry Walker
Keyword(s):  
Temperature Rise ◽  
High Speed ◽  
Testing Machine ◽  
National Physical Laboratory ◽  
Worm Gear ◽  
Variable Load ◽  
Power Losses ◽  
Heating And Cooling ◽  
Physical Laboratory ◽  
Worm Gears

The paper deals with the factors affecting the temperature rise of totally enclosed self-lubricated gearboxes, with particular reference to worm gearboxes, and is based on observations obtained from a power circulating apparatus through worm gears which has provision for the accurate measurement of efficiency and temperature rise under variable load and speed. The theory underlying the heating and cooling of gearboxes is discussed, for gears running under continuous load and also under a repeated cycle of intermittent load. Temperature rise depends on the heat-dissipating capacity of the gearbox and the power losses within the box; heat-dissipating capacity is dealt with in relation to surface area of the box, speed of the gears, and artificial cooling by air fan; power losses are discussed under the headings of efficiency and oil drag losses. It is shown that gear speed and turbulence in the lubricant contribute considerably to heat-dissipating capacity, and that oil drag losses play an important part, particularly on large gears running at moderate or high speed. Cooling by air or other means is shown to result in an increase in power capacity (for a given allowable temperature rise) much more than in proportion to the increase in heat-dissipating capacity of the box, owing to a higher overall efficiency when transmitting heavier loads. Results of worm gear efficiency tests carried out in the past on the Daimler-Lanchester testing machine at the National Physical Laboratory on the author's design of worm gear, which gave the highest efficiency of any published tests carried out on this machine, are reconsidered in the light of recent work and it is contended that the National Physical Laboratory machine gives efficiency figures which are in general higher than the true efficiency.

Alloys Research Committee: The Work of the Alloys of Iron Research Committee

1934 ◽  
Vol 127 (1) ◽  
pp. 277-298 ◽  
Author(s):  
C. H. Desch
Keyword(s):  
National Physical Laboratory ◽  
Basic Material ◽  
High Melting Point ◽  
Research Committee ◽  
Laboratory Methods ◽  
Physical Methods ◽  
X Ray ◽  
Upper Limit ◽  
Physical Laboratory ◽  
Systematic Knowledge

The Alloys Research Committee of The Institution of Mechanical Engineers began its work in 1890, and from 1902 onwards the investigations were conducted in the National Physical Laboratory. The Eleventh Report, published in 1921, dealt very fully with the light alloys of aluminium. At that stage it was decided that further research should be devoted to the alloys of iron with the object of determining the fundamental nature of the alloys of iron with various metals and non-metals to serve as a basis for a more systematic knowledge of the steels used in practice. The investigation has comprised the construction of equilibrium diagrams using thermal, microscopical, X-ray, and other physical methods. Iron being more sensitive to the influence of minute quantities of impurities than most other metals, it was necessary to prepare very pure iron as the basic material. Since 1921, the alloys of iron with oxygen, phosphorus, silicon, chromium, and manganese have been studied. As all the alloys are of high melting point, many new laboratory methods have had to be developed, the technique of experiments at high temperatures becoming more difficult the higher the upper limit is raised. In the course of the research, therefore, it has been necessary to prepare new refractories and to design special forms of apparatus in order to avoid contamination. The paper contains a summary of the results obtained in the course of the work, and it is shown how these bear upon the improvement of steels for structural and engineering purposes. The investigation is being extended to other elements, and ultimately to the influence of more than one solid element when present simultaneously in the alloy.

Characterization of Capacitance Standards at High Frequency at National Physical Laboratory, India

MAPAN ◽  
2017 ◽  
Vol 33 (2) ◽  
pp. 131-137
Author(s):  
Satish ◽  
Jyoti Swami ◽  
Babita ◽  
Thomas John
Keyword(s):  
High Frequency ◽  
National Physical Laboratory ◽  
Physical Laboratory

Influence of Frequency and Testing Technique on the Fatigue Behaviour of Quenched and Tempered Steel in the VHCF-Regime

2014 ◽  
Vol 891-892 ◽  
pp. 1430-1435 ◽  
Author(s):  
Norbert Schneider ◽  
Brita Pyttel ◽  
Christina Berger ◽  
Matthias Oechsner
Keyword(s):  
High Frequency ◽  
Fatigue Testing ◽  
Testing Machine ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Frequency Effect ◽  
Low Frequencies ◽  
Ultrasonic Fatigue ◽  
Quenched And Tempered Steel ◽  
Tempered Steel

Today in many cases ultrasonic testing machines with a frequency of f ≈ 20 kHz are used for investigations of the fatigue behaviour up to the very high cycle regime (VHCF-regime). A question that arises is if the results of these high frequency fatigue tests are comparable to conventional fatigue tests. This paper compares the fatigue behaviour of a quenched and tempered steel 50CrMo4 in two different tempered conditions investigated at low frequencies (f ≤ 400 Hz) on a servohydraulic testing machine and at a high frequency (f ≈ 20 kHz) on an ultrasonic fatigue testing machine. Effects which can occur because of the different testing techniques and testing frequencies are investigated. A concept is derived to describe the frequency effect caused by the strain rate. The estimations are compared with results of the fatigue tests.

Pseudo Fatigue Testing for Rapid Certification to Service

2014 ◽  
Vol 891-892 ◽  
pp. 1059-1064 ◽  
Author(s):  
Lorrie Molent ◽  
Simon A. Barter ◽  
Matthew Gordon ◽  
Liam Weibler
Keyword(s):  
Fatigue Test ◽  
Fatigue Testing ◽  
Critical Item ◽  
Aircraft Design ◽  
Fatigue Tests ◽  
Full Scale ◽  
Damage State ◽  
Proof Testing ◽  
The Cost ◽  
Size Estimates

Aircraft full-scale fatigue tests are expensive to conduct and they are a critical item on the certification path of any aircraft design or modification. Two aspects that contribute to the cost of a test are its duration and the loads spectrum development process. This paper provides a summary of a proposed supplemental pseudo full-scale fatigue test (FSFT) aimed at rapid certification. In this instance the method was developed with the aid of extant FSFTs that were found to be deficient. The proposed process involves the development of proof loads, damage size estimates, a loads application rig, insertion of the target damage or modifications and conducting proof testing. As all locations with a propensity to crack are known, the process is considered to be the equivalent of having conducted a representative fatigue test for the required service life target and then demonstrating adequate residual strength (i.e. proof testing the damage state at the end of a FSFT).

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