Materials thermal properties

Mass Flow Sensors Extraction of Thermal Material Properties... 

Thermophysical properties are defined, in Chapter 9 by Cagran and Pottlacher, as a selection of mechanical, electrical, optical, and thermal material properties of metals and alloys (and their temperature dependencies) that are relevant to industrial, scientific, and metallurgical applications, and this covers a wide range of different material properties obtained by numerous different measurement techniques. The focus in Chapter 9 is, however, on thermophysical properties that are accessible through dynamic pulse calorimetry Other non-calorimetric techniques have been developed but, with the exception of levitation (needed to measure technologically important properties like viscosity and surface tension) have been excluded from consideration. 

Because there are many possible ways to define thermophysical properties , we propose to define thermophysical properties as a selection of mechanical, electrical, optical, and thermal material properties of metals and alloys (and their temperature dependencies) that are relevant to industrial, scientific, and metallurgical applications. 

Various thermal material properties (as opposed to thermal stability. Chapter 9) are discussed in Chapter 16. These include coefficient of expansion, melting temperature, Vicat softening point, heat deflection/distortion temperature by thermomechanical analysis, also brittleness temperature, minimum filming temperature, delamination temperature, meltflow index, heat of volatilisation, thermal conductivity, specific heat and ageing in air. 

In the investigation of refractory lining systems, the analysis is typically done in two stages. Stage 1 is the thermal analysis. The thermal analysis can be simply steady-state thermal analysis or a transient thermal analysis. For a steady-state thermal analysis, only the thermal material property, thermal conductivity AT, is required. For transient thermal analysis, the thermal material properties required include thermal conductivity, specific heat c and density p. In any thermal analysis other data needed are the external ambient temperatures, the emissivity of the external surfaces, the external wind velocity, and other boundary conditions data that are important to the thermal analysis. 

Let us assume there are two candidate refractory materials. Refractory A and Refractory B, chosen for the lining project. We will also assume that both materials have the same thermal material properties, meaning that both refractories have the same temperature profiles. For the mechanical material properties, we assume that both materials have the same coefficient of thermal expansion and Poisson s ratio. The only difference is in the static compressive stress-strain (SCSS) data. Figure 4 shows the hypothetical SCSS data curves for the two materials at an operating temperature Tq. Since both materials have the same temperature and the same coefficient of thermal expansion, both materials have the same thermal strain, The ultimate crushing stress for Refractory A is /ca... 

The temperature data file is created from the thermal analysis. This file is used as input into the mechanical stress-strain model. The thermal model is, in most programs, converted to a mechanical model by replacing the thermal elements with the equivalent mechanical elements and converting the thermal material properties to mechanical material properties. In most cases the conversion from the thermal model to the mechanical model requires significant effort due to the addition of the nonlinear joint elements and the necessary additional... 

Material Properties. The properties of materials are ultimately deterrnined by the physics of their microstmcture. For engineering appHcations, however, materials are characterized by various macroscopic physical and mechanical properties. Among the former, the thermal properties of materials, including melting temperature, thermal conductivity, specific heat, and coefficient of thermal expansion, are particularly important in welding. 

T and are the glass-transition temperatures in K of the homopolymers and are the weight fractions of the comonomers (49). Because the glass-transition temperature is directly related to many other material properties, changes in T by copolymerization cause changes in other properties too. Polymer properties that depend on the glass-transition temperature include physical state, rate of thermal expansion, thermal properties, torsional modulus, refractive index, dissipation factor, brittle impact resistance, flow and heat distortion properties, and minimum film-forming temperature of polymer latex... 

Material property specifications must be written by design and material engineers to control engineering requirements and to control incoming raw material quahty. Material property requirements depend on various ia-use functional needs ia terms of electrical, mechanical, thermal, chemical, optical, and magnetic properties. 

There is considerable literature on material imperfections and their relation to the failure process. Typically, these theories are material dependent flaws are idealized as penny-shaped cracks, spherical pores, or other regular geometries, and their distribution in size, orientation, and spatial extent is specified. The tensile stress at which fracture initiates at a flaw depends on material properties and geometry of the flaw, and scales with the size of the flaw (Carroll and Holt, 1972a, b Curran et al., 1977 Davison et al., 1977). In thermally activated fracture processes, one or more specific mechanisms are considered, and the fracture activation rate at a specified tensile-stress level follows from the stress dependence of the Boltzmann factor (Zlatin and Ioffe, 1973). 

To minimize the gradual embrittlement that can occur on aging of cyanoacrylate adhesives, plasticizers are added. Some of the materials, which have been used as plasticizers, include phthalates, phosphonates, acyl esters, succinates, and cyano-acetates. The use of allyl, methallyl, and crotyl phthalates is also claimed to improve thermal resistance properties in addition to plasticizing the adhesive [23]. 

Moisture-transport simulation includes transport as well as storage phenomena, quite similar to the thermal dynamic analysis, where heat transfer and heat storage in the building elements are modeled. The moisture content in the building construction can influence the thermal behavior, because material properties like conductance or specific heat depend on moisture content. In thermal building-dynamics simulation codes, however, these... 

The toughness of a material is a design driver in many structures subjected to impact loading. For those materials that must function under a wide range of temperatures, the temperature dependence of the various material properties is often of primary concern. Other structures are subjected to wear or corrosion, so the resistance of a material to those attacks is an important part of the material choice. Thermal and electrical conductivity can be design drivers for some applications, so materials with proper ranges of behavior for those factors must be chosen. Similarly, the acoustical and thermal insulation characteristics of materials often dictate the choice of materials. 

If a plastic product is free to expand and contract, its thermal expansion property will usually be of little significance. However, if it is attached to another material, one having a lower CLTE, then the movement of the part will be restricted. A temperature change will then result in developing thermal stresses in the part. The magnitude of these stresses will depend on the temperature change, the method of attachment and relative expansion, and the modulus characteristics of the two materials at the point of the exposed heat. 

We present a few basic ideas of structural mechanics that are particularly relevant to the design of telescopes and to the support of related optics. This talk only touches on a very rich and complex held of work. We introduce the ideas of kinematics and kinematic mounts, then review basic elasticity and buckling. Simple and useful mles of thumb relating to structural performance are introduced. Simple conceptual ideas that are the basis of flexures are introduced along with an introduction to the bending of plates. We finish with a few thoughts on thermal issues, and list some interesting material properties. 

---