Elevated Temperature Tests Research Articles

Strain and fatigue testing of large expansion bellows

An experimental study was performed to investigate the strain and fatigue behavior of two 635-mm-diam 316 H stainless-steel convolute bellows. Bellows No. 1 was initially subjected to an axial deflection test and a pressure test, both at ambient temperature. The primary objective of these tests was to acquire strain data utilizing strain-gaging techniques. These strain tests were followed by an elevated-temperature fatigue test. Bellows No. 2 experienced the fatigue test.

The Development of Precision Thin Film Resistors for Submerged Repeater Applications

The paper describes development of a low inductance thin film resistor series with a stability of ±0.15% change in resistance, over a 25 year life, in a submerged repeater environment. (40% RH maximum and 0 to 30℃ ambient temperature).It was first necessary to establish an appropriate mathematical model relating resistor stability with time and temperature. This was devised from experimental data based on measured resistor drift at various temperatures, and enabled acceleration of resistor drift to be carried out to ensure that each resistor possessed the required stability.Deposition of a secondary nichrome layer protects the gold/nichrome interface and promotes SiO2adhesion. This results in an improvement in the basic elevated temperature resistor stability by minimising diffusion effects of nichrome into the conductor, and protection against electrochemical corrosion as demonstrated by 10,000 hours life test at 83% RH @ 28℃ on 5 mW load and by elevated temperature tests under electrical loading.

A New Method for Measuring Adhesion of Vulcanized Rubber to Steel Cord at Elevated Temperatures

Abstract The analysis of variance of the elevated temperature tests conducted in this study showed that the experimental sample holder gave slightly higher values than tests run in an oven with the standard sample holder. However, this difference was less than 1% of the average adhesion value. Student's t-tests of the individual unit-to-unit comparison rated the test procedures equivalent over a wide range of temperature and aging histories. The advantages of this experimental sample holder are: 1. lower equipment costs; 2. rapid means of testing steel cord adhesion at elevated temperatures; 3. ease and simplicity of operation; 4. adaptability of the experimental holder to various tensile testing equipment.

An investigation of the aging of thermally prestabilized sintered samarium-cobalt magnets

The effects of long-term air exposure at 25°, 150°, 200° and 250° C on the stability of the open-circuit remanence at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B_{d}/H_{d}\approx 1</tex> were studied. Magnets were prestabilized by heating at 150°-250° before room temperature aging, 50° above exposure level for the elevated-temperature tests, then they were exposed for periods of up to 8000 hours. Loss data for different operating temperatures and preheating conditions are reported. Preheating anticipates initial aging by thermally activated wall motion. This reduces aging losses at 25°C at least by a factor 2 to 4, at 150° by a factor 5-8. At operating temperatures above 200° the medium-term stability is strongly improved, but catastrophic losses set in after several 100 to 1000 hours. Prestabilized magnets show more uniform aging behavior than lots of samples tested without preheating. No significant differences were found between diepressed and isopressed magnets. Heating to at least 200°C and at least 50° above the use level for 2 hours is recommended for prestabilization.

Effect of thermal aging upon the fatigue-crack propagation of austenitic stainless steels

The effect of thermal aging upon the elevated temperature fatigue-crack propagation behavior of several austenitic stainless steels was investigated using linear-elastic fracture mechanics. The steels studied were ABI Types 304, 304L, 316 (both annealed and cold-worked), and weldments in Type 304 using Type 308 filler. Aging temperatures of 1000°F and 1200°F were employed, and aging times ranged between 1500 and 6000 hours. In general, thermal aging produced beneficial results (i.e., lower crack growth rates) relative to unaged material in elevated temperature tests. It is suggested that the precipitation of the various carbide and intermetallic phases is responsible for the beneficial effect. One possible mechanism might be a blunting effect each time the crack tip encounters a second-phase particle, thereby requiring the crack to partially reinitiate itself before proceeding.

Effect of Elevated Temperature Operation on the Strength of Aluminum Conductors

The relationships between "remaining strength", time and temperature for conductors operated at elevated temperatures are presented as empirical models based on elevated temperature test results. The comparison between the remaining strength predicted from the models and the measured remaining strength is shown. Use of the models is explained and examples of their use are presented.

The Relationship of Glass Transition Temperature to Adhesive Strength

Abstract The effects of glass transition temperature (Tg ) on mechanical properties have been further demonstrated by the observation of adirect relationship between the Tg of an epoxy adhesive and its lap shear bond strength to metal at elevated test temperatures. An additive (coupling agent) which lowers the Tg from a point near or above the test temperature to below it causes a subsequent decrease in the strength of the system and generally increased cohesive failure. Therefore effects on the Tg of the adhesive are more important than on interfacial properties. The end result is that differential thermal analysis (DTA) can be utilized as a effective screening method for adhesives and additives, and can be a good indicator of maximum use temperature. From these data Tg can also be used to estimate adhesive strength at a given use temperature.

Unusual organism which gives a positive elevated temperature test for fecal coliforms.

Organisms apparently not of fecal origin isolated from a sulfur hot spring gave a positive elevated temperature test for fecal coliforms.

Unusual Organism Which Gives a Positive Elevated Temperature Test for Fecal Coliforms1

Organisms apparently not of fecal origin isolated from a sulfur hot spring gave a positive elevated temperature test for fecal coliforms.

Rapid Recovery of Escherichia coli from Estuarine Water

The efficiencies of two 24-hr elevated-temperature tests to recover Escherichia coli from estaurine water were compared simultaneously with the 72-hr standard methods procedure of the American Public Health Association (APHA). From 1,710 tubes, E. coli was recovered 222 times in lauryl tryptose medium incubated at 44 +/- 0.2 C for 24 hr, 261 times in an experimental medium incubated at 44.5 +/- 0.2 C for 24 hr, and 257 times by the 72-hr APHA method. The number of false positives enumerated was similar in all three tests. The data indicated that E. coli in raw seawater could be determined in 24 hr without a significant loss of accuracy.

Chemical Vapor Deposited Tungsten—Mechanical Evaluation at High Temperatures

A high‐temperature hoop stress measurement apparatus has been developed for ring specimens of CVD tungsten or other refractory metal alloys. This apparatus has the advantage of being adaptable for high‐temperature tensile testing. Force is applied to a tapered cone which transmits force to eight equal segments which press uniformly on the inner surface of the ring specimen. The specimen is heated by induction in either vacuum or a protective atmosphere. Equations are developed for stress and strain from hoop stress parameters. Room temperature hoop and tensile tests on aluminum, copper, and brass specimens were compared to ascertain the role of friction in the hoop stress tests. For temperatures up to 1400°C, the effective friction coefficient, µ, of the hoop testing apparatus was determined using CVD tungsten in a similar manner. Design details and the results of the elevated temperature tests on CVD tungsten are discussed.

Fatigue-crack propagation behavior of type 304 stainless steel at elevated temperatures

The fatigue-crack propagation behavior of Type 304 stainless steel was investigated within the framework of linear elastic fracture mechanics at temperatures of 75‡, 600‡ 1000‡ and 1200‡F. The cyclic frequency for the elevated temperature tests was 4 cpm. It was found that, in general, fracture mechanics concepts may be used to describe the crack propagation behavior at these temperatures, and that increasing the temperature had a significant effect in increasing the fatigue-crack growth rate.

Dynamic Behavior of Metals Under Tensile Impact—Part 1: Elevated Temperature Tests

The mechanical behavior of metals subjected to uniaxial tensile impact at elevated temperatures is reported. Tests were conducted on annealed 1100 aluminum at 200, 350, 550, and 800 deg F; annealed 2024 aluminum at 200, 450, and 600 deg; and annealed C1010 steel at 430, 700, 1050, and 1400 deg F. The materials exhibit a wide range of dynamic behavior, including some in which the stress required to produce a given level of strain is significantly lowered by dynamic loading. The ratios of the dynamic ultimate stresses to the static are found to range from 0.71–6.0.

Use of Elevated-Temperature Creep Data in Sag-Tension Calculations

This paper presents a simplified method of using elevated- temperature creep data in sag-tension calculations. A time- temperature prediction model for the line and data obtained from laboratory elevated-temperature creep tests are the only data required in addition to standard stress-strain and creep data.

An evaluation of the standard biochemical and elevated temperature tests for differentiating faecal and non-faecal coliforms

In this study the relative efficacies of the biochemical IMViC and the elevated temperature (FC) tests have been compared for differentiating the faecal and non-faecal coliforms. Altogether 1628 coliform strains comprised of 427 from 143 samples of human faeces, 301 from 101 samples of cattle faeces, 631 from 113 samples of sewage and 269 from 120 samples of soil were classified as to their IMViC types and response to elevated temperature reactions. Parr's Escherichia group (+ + − −, + − − − and − + − −) was represented by 83 and 85 per cent of the coliform strains isolated from human and cattle faeces respectively. Of the coliform strains isolated from human and cattle faeces 82.0 and 76.4 per cent respectively were found positive for the FC test. Hence, neither the IMViC nor the FC tests by themselves can be considered adequate for differentiating coliforms of faecal and non-faecal origin. Based on the results obtained in this study the authors have interpreted the sanitary significance of the coliforms present in various sources.

Test Methods to Establish Strength and Reliability

Three main subjects are presented in this paper: (i) A description of tests made for the purpose of determining design data; (ii) a discussion of the problems arising in the establishment of the approval procedures necessary to ensure safety and reliability; and (iii) a discussion of proposals for cyclic reliability tests. In the first section, tests to provide design data for glazing materials are described with particular emphasis placed on glasses. Types of specimen and apparatus for obtaining data at room temperature are mentioned and illustrations given of apparatus and specimens used in long term elevated temperature tests. In the second section, the overall level of reliability of complete components is discussed both in terms of structural safety and satisfactory service. While the current requirements have proved satisfactory for the past generation of aircraft, proposals are now put forward for patterns of testing that are more closely linked to the various design conditions now in use with both high‐speed and low‐speed aircraft, in order to place equal importance on the effects of temperature. In the third section, proposals are put forward for cyclic testing to overcome what appears to be an increasingly unsatisfactory record of reliability. The purpose of the tests is not to establish a safe life for any particular design but to reveal design deficiencies occurring from repeated applications of flight and thermal loadings.

Chloride Corrosion and Fouling In Catalytic Reformers With Naphtha Pretreaters

Abstract A study was made of chloride corrosion and fouling occurring in low-temperature sections of catalytic reformer naphtha pretreaters. These problems were related to corrosion by aqueous HCl-H 2 S-NH 3 solutions. Laboratory corrosion studies were made with these solutions to establish the effect of pH and composition in the presence or absence of an air atmosphere. Suppression of corrosion by ammonia neutralization and amine-type inhibitors also was studied. Elevated temperature tests were conducted in a nitrogen atmosphere. Field tests were made on six metals in a commercial pretreater reactor effluent stream. The removal of ammonium chloride fouling deposits was discussed briefly. 8.4.3, 4.3.2, 5.7.7, 3.3.2

Short-Time, Rapid-Heating, Elevated Temperature Testing

Short-Time, Rapid-Heating, Elevated Temperature Testing

Aircraft Structural Testing Techniques at Elevated Temperatures

Abstract The object of this paper is to review some of the test-system requirements and problems associated with structural testing of aircraft at elevated temperatures. A brief description of loading methods used for the past generation of aircraft is presented. The requirements of an elevated-temperature test facility are established on the basis of the need for simultaneous heating and loading of an aircraft structure. Heating devices such as heating blankets, strip heaters, film heaters, induction coils, radiant heating coils, and infrared lamps which are being investigated by the Wright Air Development Center are discussed in relation to methods of attaching loads. Complications caused by simultaneous heating and loading are illustrated by a discussion of two structural tests performed at the Wright Air Development Center. A description is also given of an electronic computer developed to program the aerodynamic heating of a structure.

Comparisons at Elevated Temperatures of Some Commercial Grades of Ferritic Cast Steels

Abstract This paper presents some direct elevated-temperature test comparisons of cast steel Grades WC4, WC5, WC6, and WC9 of ASTM Specification A217-49T. The materials studied are from commercial heats. Care has been taken to hold all variables in manufacture, treatment, and composition (aside from prescribed “alloy elements”) as closely alike as possible. The tests show that at the temperatures under consideration the nominal 1 per cent molybdenum grades WC5 and WC9 are higher in “creep strength” than the nominal ½ per cent molybdenum grades, WC4 and WC6. Grade WC5 has shown, in this direct comparison, higher “stress-rupture strength” than the other three grades.