NASA Contributions to Development of Special-Purpose Thermocouples. A Survey

The thermocouple has been used for measuring temperatures for more than a century, but new materials, probe designs, and techniques are continually being developed. Numerous contributions have been made by the National Aeronautics and Space Administration and its contractors in the aerospace program. These contributions have been collected by Midwest Research Institute and reported in this publication to enable American industrial engineers to study them and adapt them to their own problem areas. Potential applications are suggested to stimulate ideas on how these contributions can be used

Sensors for ceramic components in advanced propulsion systems: Summary of literature survey and concept analysis, task 3 report

The results of a literature survey and concept analysis related to sensing techniques for measuring of surface temperature, strain, and heat flux for (non-specific) ceramic materials exposed to elevated temperatures (to 2200 K) are summarized. Concepts capable of functioning in a gas turbine hot section environment are favored but others are reviewed also. Recommendation are made for sensor development in each of the three areas

Temperature and heat flux measurements: Challenges for high temperature aerospace application

The measurement of high temperatures and the influence of heat transfer data is not strictly a problem of either the high temperatures involved or the level of the heating rates to be measured at those high temperatures. It is a problem of duration during which measurements are made and the nature of the materials in which the measurements are made. Thermal measurement techniques for each application must respect and work with the unique features of that application. Six challenges in the development of measurement technology are discussed: (1) to capture the character and localized peak values within highly nonuniform heating regions; (2) to manage large volumes of thermal instrumentation in order to efficiently derive critical information; (3) to accommodate thermal sensors into practical flight structures; (4) to broaden the capabilities of thermal survey techniques to replace discrete gages in flight and on the ground; (5) to provide supporting instrumentation conduits which connect the measurement points to the thermally controlled data acquisition system; and (6) to develop a class of 'vehicle tending' thermal sensors to assure the integrity of flight vehicles in an efficient manner

Fuzzy Logic Control in High Temperature Furnace

This work presents a novel technique to maintain temperature of a furnace using Fuzzy Logic.  The furnace temperature has to be controlled and maintained upto 1500 degree Celsius and the purpose of the furnace is to study the characteristics of welding materials at very high temperature.  Since the range of temperature above ambient is fairly high and the furnace working area is also large, the phenomenon of maintaining the temperature at the desired value poses many challenges.  In this work, Fuzzy Logic Control (FLC) system has been implemented by duly considering the working temperature range, as well as working area. The advent of the control system is, its ability to attain the set temperature at the set time and also to maintain it. A complete study of the furnace, as well as TRIAC based final control element has been done.  The choice of membership function is done, so that to minimize steady state errors and also to reach the set temperature at the pre-defined time interval.Fuzzy Logic uses conventional electronics and instrumentations along with Micro controllers for controlling the furnace temperature.  Complete mathematical modeling of the furnace temperature control system based on fuzzy technique delivers a good solution to this work.Keywords: Pulse width Modulation, Fuzzy logic control, Fuzzy logi

In-situ characterization of tool temperatures using in-tool integrated thermoresistive thin-film sensors

Metal cutting is characterized by high temperatures at the tool-workpiece interface. Although valuable information could be provided by the temperature values, their direct measurement still presents a challenge due to the high contact pressure and the inaccessibility of the process kinematic. In this research work, the current state of thin-film sensors for measuring temperatures on the chip-tool interface has been analyzed with a focus on the measuring phenomena: thermoelectricity and thermoresistivity. Thin-film sensors placed on the cutting tools in or close to the tool-chip contact area are expected to obtain accurate temperature information at the expense of a short lifetime. New insights into thin-film sensors manufacturing, design and calibration are presented, and a new concept of a three-point thermoresistive thin-film sensor is proposed. During orthogonal cutting tests the workpiece deformations were measured through high-speed imaging and the process temperatures were measured with thin-film sensors. In order to validate the temperatures and to obtain the temperature distribution on the cutting edge, Finite Element simulations were carried out. Finally, the potential of using cutting tools with integrated thin-film sensors for in-situ characterization is investigated and a statement for its limitations and potential applications is given

NBS monograph

From Introduction: "The purpose of this paper is to present information on materials that are used from 0 degrees C up in thermocouples intended primarily as immersed temperature sensors, and to give so far as is practical properties of these materials that might affect their use in temperature measurement.

Instrumentation design study for testing a hypersonic ramjet engine on the x-15 a-2. volume 3- conceptual design of measurement systems

Instrumentation for testing hypersonic ramjet engine on X-15A-2 aircraf

Index to NASA Tech Briefs, January - June 1966

Index to NASA technological innovations for January-June 196

Design, Manufacture and Properties of Cr-Re Alloys for Apllication in Satellite Thrusters.

Aquesta tesi ha consistit en el disseny, fabricació i estudi de les propietats d'aleacions Cr-Re destinades a substituir els aliatges base Pt utilitzats en els motors d'apogeu i de correcció orbital de satél.lits i ha estat recolzada pel Centre de Recerca d'EADS en col.laboració amb la Universitat Politècnica de Catalunya. Els aleatges de Cr-Re han estat objecte d'alguns estudis en el passat que indicaven una millora de les propietats mecàniques amb addicions de fins un 35% de Re. Malhauradament aquests estudis de caire fonamental no incluïen la investigació de la influència del Re en altres proprietats importants per aplicacions estructurals. En aquesta tesi s'ha dissenyat un métode de fabricació semi-industrial pels aliatges Cr-18at%Re i Cr-35at%Re i s'ha estudiat les propietats mecàniques, químiques i tèrmiques rellevants a l'aplicació potencial dels aliatges en càmeres de combustió de motors de satél.lit Un métode de fabricació pulvimetal.lúrgic ha estat dissenyat per la producció d'aliatges prototip i s'ha desenvolupat un métode de fabricació per fosa mitjançant arc eléctric en cressol fred per produir els aliatges d'alta puresa. Per millorar l'homogeneïtat dels aliatges Cr-18Re s'ha implementat un métode d'inoculació de la fosa amb Cr, Pr i Sc. Els aliatges produits per aquest métode presenten una alta puresa i homogeneïtat.Les proprietats mecàniques dels aliatges milloren amb percentatges de Re creixents. Els aliatges Cr-35Re produits en fase líquida presenten les millors propietats mecàniques amb un límit elàstic de 800 MPa a temperatura ambient i una deformació a la ruptura del 5% en tracció. A 1400°C el límit elàstic en tracció i compressió és superior a 140MPa. El Cr-35Re presenta fractura en mode mixte intergranular-transgranular fins a 1200°C i intergranular a temperatura més elevada, això limita la seva plasticitat a alta temperatura. La ductilitat màxima, amb una deformació en tracció del 10% s'assoleix en mode intergranular entre 600 i 1000°C. La resistència dels aliatges Cr-18Re i Cr-35Re a l'oxidació i a la nitruració va ser assajada fins a 1500°C. L'estabilitat dels Cr-35Re a alta temperatura és molt bona i la influència de l'exposició a alta temperatura en la ductilitat és limitada. Els aliatges Cr-18Re presenten una resistència a temperatures elevades mediocre, caracteritzada per la la segregació del Cr a les boreres gra durant l'exposició i la seva evaporació.Com era previsible les addicions de Re al Cr disminueixen la conductivitat tèrmica i elèctrica, ja que els àtoms de Re distorsionen la simetria cristal.lina de l'aliatge. La disminució de la conductivitat térmica unida a la millora de les propietats mecàniques fa difícil fer una estimació sobre la resitència de l'aliatge al xoc tèrmic. Per aquesta raó es va decidir comprovar experimentalment la resistència dels aliatges als gradients térmics característics de l'aplicació. La cinètica d'escalfament de 500K/s i el gradient térmic geomètric de 500K/mm van ser impossibles de reproduir amb equips comercials i va ser necessàri dissenyar una instal.lació específica basada en un forn d'arc eléctric. Els aliatges de Cr-35Re donen la millor resposta en xoc i gradient tèrmic, presentant micro fissures de menys de 150µm a la superfície després de 100 cícles i cap fissuració interna, mentre que els aleatges de Cr-18Re presenten fissuració a les boreres de gra de la superfícies fins a una findària de 200µm.La millora de les propietats mecàniques, químiques i de ciclatge tèrmic de l'aleatge contenint un 35% de Re es significativa i indica que s'adequa a l'aplicació. L'estudi ha resultat en la fabricació d'un motor de 22N que serà assajat a les instal.lacions de EADS Space a Lampoldhausen, Alemanya.The manufacturing process and properties of various Cr-Re alloys have been investigated in this work to replace Pt alloys used currently in the satellite thruster combustion chambers. This Thesis has been supported by the Corporate Research Center of EADS and tutored by the Technical University of Catalonia. The studies carried out in the past on the Re effect on the mechanical properties of refractory alloys resulted in the industrial application of Mo-Re and W-Re alloys. Cr-Re alloys have been studied at a fundamental level indicating an improvement of the mechanical properties of the alloys containing Re. Other properties related to its potential application in satellite thrusters were not characterized and an industrial manufacturing process for Cr-Re alloys does not exist, hence the motivation for this PhD. In this work Cr-Re alloys were manufactured initially by means of powder metallurgy. Their mechanical properties improved with increasing Re content verifying the results of the few literature references available. High purity Cr-18at%Re and Cr-35at%Re alloys were produced by melting and casting by a specific procedure. Heterogeneity problems in Cr-18Re alloys were reduced by inoculation of the melt with Ce, Pr and Sc. Mechanical properties of the high purity Cr-Re alloys improve significantly over the powder metallurgical alloys. Compressive elastic limit of both Cr-18 and Cr-35Re alloys at room temperature is over 800 MPa and compressive deformation is possible up to 70% without formation of surface cracks. Elastic limit at 1400°C is over 140 MPa both under compression and tension. Fracture under tension is mixed transgranular and intergranular up to 1200°C. Above this fracture becomes intergranular, characterized by very little plasticity. Best ductility under tension is obtained between 600 and 1000°C with a deformation to fracture of about 10%.Resistance of the alloys to oxidation and nitruration was characterized up to 1700 °C. Tests revealed that Cr-18Re alloys are not capable of building a stable protective layer during exposure to air or nitrogen at the test temperature. They also present a grain boundary instability caused by Cr segregation and evaporation during exposure. Cr-35Re alloys create a stable protective layer of Cr oxide that protects the substrate against light element diffusion. In nitrogen atmosphere Cr-35Re builds a stable layer that is not protective against diffusion of nitrogen. The investigation of the plasticity of the samples after exposure shows that diffused nitrogen does not affect significantly the plasticity of Cr-35Re however there is some scatter in the results due to the small sample cross section relative to grain size. Exposure to vacuum at 1700 °C verified that the grain boundary instability of Cr-18Re was not related to any reaction with the atmosphere as it also takes place in vacuum. Cr-35Re alloys did not present any significant sublimation at this temperature and no grain growth could be detected after exposure. Additions of Re to Cr reduce the thermal and electric conductivity of the alloys as the symmetry of the lattice is distorted by the Re atoms. This, coupled to the improvement of the mechanical properties makes a prediction of the thermal shock resistance of the alloys difficult. For this reason it was decided to build an installation reproducing the thermal shocks and thermal gradients, of 500K/s and 500K/mm respectively, characteristic of the application. When cycled, Cr-18Re alloys suffered also from the grain boundary instability and fractured up to a depth of 200µm. Cr-35Re alloys showed minor cracks and accommodated the linear thermal gradient by means of twinning. The mechanical, chemical and thermal cycling properties of the Cr-35Re alloys indicate that it is suitable for the application. This work resulted in the construction of a 22N satellite thruster with Cr-35Re alloy that will be tested in EADS Space Transportation in Lampoldshausen

Cumulative Index to NASA Tech Briefs, 1963 - 1966

Cumulative index of NASA Tech Briefs dealing with electrical and electronic, physical science and energy sources, materials and chemistry, life science, and mechanical innovation