Temperature tests

Vehicle tests are considered the ultimate in friction material evaluation, but to be accurate these tests must be carefully designed to eliminate variations caused by changing conditions. ControUed-temperature tests and parallel-test controlled vehicles normally perform the function satisfactorily but at increased cost. 

R. A. Mercuri, R. A. Howard, and J. J. McGl meiy, Ndranced High Temperature Test Methodsfor Gasket Materials, Automotive Eng 97, 49—52 (July 1989). 

Test Method for Electrical Resistivity of Manufactured Carbon and Graphite Articles at Room Temperature Test Method for Compressive Strength of Carbon and Graphite... 

Temperature tests ean be eondueted at ambient room temperature, but the designer must remember that the typieal produet is enelosed in a ease and its internal temperature rise must be added to the readings. Another eonsidera-tion is the highest external ambient temperature the produet may experienee. In the desert, where this book was written, daytime temperatures may reaeh A3°C in the shade and exeeed 55°C inside an automobile. 

Two particular test methods have become very widely used. They are the Vicat softening point test (VSP test) and the heat deflection temperature under load test (HDT test) (which is also widely known by the earlier name of heat distortion temperature test). In the Vicat test a sample of the plastics material is heated at a specified rate of temperature increase and the temperature is noted at which a needle of specified dimensions indents into the material a specified distance under a specified load. In the most common method (method A) a load of ION is used, the needle indentor has a cross-sectional area of 1 mm, the specified penetration distance is 1 mm and the rate of temperature rise is 50°C per hour. For details see the relevant standards (ISO 306 BS 2782 method 120 ASTM D1525 and DIN 53460). (ISO 306 describes two methods, method A with a load of ION and method B with a load of SON, each with two possible rates of temperature rise, 50°C/h and 120°C/h. This results in ISO values quoted as A50, A120, B50 or B120. Many of the results quoted in this book predate the ISO standard and unless otherwise stated may be assumed to correspond to A50.)... 

In the deflection temperature under load test (heat distortion temperature test) the temperature is noted at which a bar of material subjected to a three-point bending stress is deformed a specified amount. The load (F) applied to the sample will vary with the thickness (t) and width (tv) of the samples and is determined by the maximum stress specified at the mid-point of the beam (P) which may be either 0.45 MPa (661bf/in ) or 1.82 MPa (264Ibf/in ). 

At the risk of oversimplification it might be said that the Vicat test gives a measure of the temperature at which a material loses its form stability whilst the higher stress level heat distortion temperature (1.82 MPa) test provides a measure of the temperature at which a material loses its load-bearing capacity. The lower stress (0.45 MPa) heat distortion temperature test gives some rather intermediate figures and it is perhaps not surprising that it is today less often quoted than the other two tests. 

As might be expected of a somewhat polar thermoplastics material, mechanical, electrical and other properties are strongly dependent on temperature, testing rate and humidity. Detailed data on the influence of these Vciriables have been made available by at least one manufacturer and the following remarks are intended only as an illustration of the effects rather than as an attempt at providing complete data. 

The figures given in the table are obtained on mouldings relatively free from orientation and tested under closely controlled conditions of temperature, testing rate, and humidity. Changes in these conditions or the use of additives may profoundly affect these properties. Details of the influence of these factors on mechanical properties have been published in the trade literature but Figures 18.11-18.14 have been included to illustrate some salient features. 

The so-called flow temperature cannot be considered to be either the processing temperature or the maximum service temperature. It is obtained using the highly arbitrary Rossi-Peakes flow test (BS 1524) and is the temperature at which the compound is forced down a capillary of fixed dimensions by a fixed load at a specified rate. It is thus of use only for comparison and for quality control purposes. Since the rates of shear and temperatures used in processing are vastly different from those used in this test, extreme caution should be taken when assessing the result of flow temperature tests. 

Figure 25.9. Typical exotherm curves for polyester resin cured with 1% benzoyl peroxide over a range of bath temperatures. (Test tubes of 19 mm dia are filled to height of 8 cm with a mixture of resin plus peroxide. The tubes are immersed in a glycerin bath to the level of the resin surface. Temperature is measured with a thermocouple needle whose point is half-way down the resin...

The electrical properties will also depend on the above factors as well as on the test conditions, in particular temperature, test frequency and humidity. Table 26.12 quotes ranges for figures quoted in the literature for various electrical properties. 

High Temperature Test Reactor, HTTR (Japan)... 

There is second shear adhesion test that is now being reported with increasing frequency, the so-called SAFT, or shear adhesion failure temperature test. It is particularly popular among block copolymer PSA developers. In this test [15], a shear specimen with an overlap area of 2.54 cm x 2.54 cm is prepared and suspended in a circulating air oven. A 1-kg weight is attached to the tape and the oven temperature is raised continuously 5.5°C per 15 min until failure. An industry wide standard has not yet been written for this test. 

Temperature Tests. Temperature tests are tests taken to determine the temperature rise of certain parts of the machine above the ambient temperature, when running under a specified load. 

Room temperature test of duration 120 days, solution agitated. Caihode anode area = 100 1. 

Table 7.21 Oxidation of nickel-base alloys and nickel-chromium steels in cyclic temperature tests of 100 h duration" ...

Test temperature. Tests should be run at a minimum of three temperatures and preferably four to confirm the linear relation between the logarithm of life and the reciprocal of absolute temperature. Several samples are necessary to plot the results of changes occurring versus time for each testing temperature. The time available and the accuracy of the extrapolation desired determine the lowest test temperature. Usually the most desirable lowest temperature is one that will give results in about 1,000-2,000 h (6-12 weeks). 

It was concluded that any candidate component can be produced using PM forging techniques at a cost at least 50 per cent lower compared with conventional forging processes. The accelerators were endurance-tested and exceeded all requirements in the standard room-temperature tests. The accelerators also withstood the test firing of more than 10,000 rounds at minus 65 degrees Fahrenheit with no failures being experienced... 

Once the 5-minute heating period has ended, turn off the gas flow to the burner. When the test tube has cooled to room temperature, test the brittleness and viscosity of the polymer using a stirring rod. Record your observations. 

Ryles, R.G. "Elevated Temperature Testing of Mobility Control Reagents", SPE paper 12008, 1983 SPE Annual Technical Conference and Exhibition, San Francisco, CA, October 5-8. 

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