Thermal Expansion Tests Research Articles

Crystallization behaviors of R 2O–Al 2O 3–SiO 2 glass–ceramics for use as anodic bonding materials

In this work, the crystallization behaviors of R 2O–Al 2O 3–SiO 2 (R means K, Na and Li) glass–ceramics which was used as anodic bonding materials were discussed. The glass–ceramics with P 2O 5 as nucleation agents were investigated by means of differential scanning calorimeter (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and coefficient of thermal expansion (CTE) tests. The test results have shown that: the DSC trace of parent glass has two different precipitation crystallization peaks corresponding to formation the crystal phases of Li 2Si 2O 5 and Li 2SiO 3. According to the selected heat treatment schedules, the Li 2SiO 3 crystal phases changed into Li 2Si 2O 5 while the crystallization temperature at 650 °C in glass–ceramics; on the contrary, the Li 2Si 2O 5 crystal phases can be decomposed into Li 2SiO 3 at the crystallization temperature of 850 °C. The coefficients of thermal expansion with R 2O–Al 2O 3–SiO 2 glass–ceramics about 119–140 × 10 −7/°C at 450 °C, which could be nearly matched that of stainless steel (No. 430#).

Silkworm silk/poly(lactic acid) biocomposites: Dynamic mechanical, thermal and biodegradable properties

Silkworm silk/Poly(lactic acid) (silk/PLA) biocomposites with potential for environmental engineering applications were prepared by using melting compound methods. By means of Dynamic mechanical analysis (DMA), Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), Coefficient of thermal expansion test, Enzymatic degradation test and Scanning electron microscopy (SEM), the effect of silk fiber on the structural, thermal and dynamic mechanical properties and enzymatic degradation behavior of the PLA matrix was investigated. As silk fiber was incorporated into PLA matrix, the stiffness of the PLA matrix at higher temperature (70–160 °C) was remarkably enhanced and the dimension stability also was improved, but its thermal stability became poorer. Moreover, the presence of silk fibers also significantly enhanced the enzymatic degradation ability of the PLA matrix. The higher the silk fiber content, the more the weight loss.

Effect of Thermal Exposure on the Thermal Expansion Behavior of SiCf/Ti-6Al-4V Composite

Abstract SiCf/Ti-6Al-4V composites were used to study the effects of thermal exposure on the thermal expansion behavior of composites. The expansion behaviors of the matrix alloy, as-processed composite, and composites exposed at 900 °C for 10, 25 and 75 h were investigated by coefficients of thermal expansion (CTE) test. The results indicate both in longitudinal and transverse direction, the CTE of the exposed composite is higher than that of the as-processed composite. The CTEs of the specimens exposed at 900 °C for 10 and 75 h are higher than that of the specimen exposed at 900 °C for 25 h, no matter in longitudinal or transverse direction. It can be attributed to that there is an appropriate interfacial reaction for the composite exposed at 900 °C for 25 h. Because the prediction of Schapery's model for CTE of composite includes the influence of thermal tensile residual stress in matrix at the whole heating process, the CTE results predicted by Schapery's model are lower than the real CTE obtained from experiments at the high temperature stage of the CTE curve.

Direct observation of microcrack development in marble caused by thermal weathering

One of the properties that makes marble such an excellent construction and ornamental material is its low porosity. It is very difficult for water or decay agents to penetrate the internal structure of materials with no or few pores, so enhancing the durability of these materials. However, environmental temperature fluctuations bring about significant physical changes in marbles that result in an increase in porosity, due to the appearance of new microcracks and the expansion of existing ones. These cracks offer new paths into the marble which make it easier for solutions containing pollutants to penetrate the material. Thermal expansion tests were performed on three different types of marble known as White, Tranco, and Yellow Macael (Almeria, Spain), after which an increase in porosity (from 17 to 73% depending on marble type) was observed, mainly due to crack formation. The structural changes occurring during thermal expansion tests were more significant in the case of White Macael samples, a fact that is not only related to its mineralogical composition but also to the morphology of the grains, grain boundaries and crystal size. Our research suggests that thermally weathered White Macael marble could be more susceptible to decay by other contaminant agents than Tranco or Yellow Macael. The use of hot-stage environmental scanning electron microscopy is proposed as a valid tool for observing, both in situ and at high magnification, changes in the fracture system of building stones induced by thermal stress.

High temperature low cycle fatigue properties of a HF30-type cast austenitic stainless steel

This work investigated the high temperature low cycle fatigue behavior of HF30-type, cast austenitic stainless steel. In addition to the preliminary results from tensile and thermal expansion tests, isothermal strain controlled fatigue tests at 600°C and 800°C were carried out with a total strain amplitude from ±0.20 % to ±0.65% and with a strain rate of 10−3/s. The plastic strain amplitudes during cyclic strain loading were measured and correlated with the fatigue lifetime using Coffin–Manson plots at each test temperature. These plots were re-constructed into a general superposition curve containing the results from both temperatures using a constitutive equation of the energy criterion for fatigue failure in terms of thermally activated dislocation motion. The cast and wrought stainless steels showed similar fatigue properties.

Evaluation of Coefficient of Thermal Expansion Test Protocol and Its Impact on Jointed Concrete Pavement Performance

In order to determine the typical concrete paving mixture thermal expansion coefficient (CTE sub PCC) with mixture coarse aggregate derived from eight different Michigan sources, a laboratory investigation was conducted. Trap rock, gravel, slag, dolomite, and limestone were included in the primary aggregate class. The provisional AASHTO TP60 protocol was used to determine the CTE sub PCC. For each mixture-age combination, there was fabrication of three replicate test specimens. Prior to testing, there was moist curing of the test specimens for 3, 7, 14, 28, 90, 180, and 365 days. There was a 4.51 to 5.92 μe per degree F (8.11 to 10.65 μe per degree F) value range for average measured CTE sub PCC. That the number of heating and cooling cycles that the specimen is subjected to, the age of specimen at time of testing, and aggregate geology have statistically significant impacts (at 95% confidence level) on measured CTE sub PCC magnitude is indicated in test results. The test variables' practical impact on jointed plain concrete pavement transverse cracking performance is also discussed.

Synthesis and electrophysical properties of cation conductors Sr 3 − 3 xLa 2 x(V 1 − yP yO 4) 2 with palmierite structure

The solid solutions Sr 2.4La 0.4(V 1 − y P y O 4) 2 with palmierite structure were synthesized and characterized. The electrical conductivity was measured depending on temperature and partial pressure of oxygen. Both studies were carried out in the range of partial oxygen pressure 10 − 15 − 0.5atm at temperatures 400–1200°C. Thermal expansion tests were carried out in air within 20–1200°C. The cation transport over Sr2 positions is responsible for the ion conductivity below 950 °C. The disordering of palmierite structure in Sr 2.4La 0.4(V 1 − y P y O 4) 2, where y ≥ 0.3, near 1000 °C is accompanied by the conductivity increase in about two times and by the decrease of thermal expansion coefficient. These changes are explained as manifestation of interstitial strontium cations. The substitution of vanadium by phosphorus results in the increase in thermodynamic stability.

Oxygen nonstoichiometry and high-temperature transport in SrFe 1 − xW xO 3 − δ

The complex oxides in the series SrFe 1 − x W x O 3 − δ were synthesized and attested to have cubic structure. The oxygen content was measured by coulometric titration technique, and electrical conductivity was measured by four-probe d.c. method in the oxygen partial pressure range 10 − 18 –0.5 atm and at temperatures 650–950 °C. Thermal expansion tests were performed in air within temperature interval 20–1000 °C. The partial molar thermodynamic functions of labile oxygen ions were calculated using coulometric titration data. Conductivity analysis was utilized to separate partial contributions from oxygen ions, n-and p-type electron charge carriers. The concentration and mobility of p-type charge carriers were calculated by combining data from oxygen content and conductivity measurements. It is shown that partial replacement of iron for tungsten results in a strong disordering of the oxygen sub-lattice that renders the perovskite to brownmillerite phase transition suppressed. The observed ion conductivity level in the sample x = 0.1 at T < 850 °C occurs somewhat higher than in the undoped ferrite while electron contribution remains nearly the same. The increase in the concentration of the dopant results in filling of oxygen vacancies and in respective decrease of the oxygen ion conductivity level. The thermal expansion coefficient is observed to monotonously decrease with the increase in tungsten content.

Effect of Coefficient of Thermal Expansion Test Variability on Concrete Pavement Performance as Predicted by Mechanistic-Empirical Pavement Design Guide

The coefficient of thermal expansion (CTE) of concrete is a property that can affect the performance of the pavement and its service life and is one of the most important inputs in the Mechanistic-Empirical Pavement Design Guide (MEPDG). The CTE can be either estimated or measured in the laboratory. The test method used to determine this property is AASHTO TP 60, still a provisional test method and not yet evaluated for its precision. CTEs of more than 1,800 concrete specimens were measured at the Turner-Fairbank Highway Research Center. The specimens included cylinders that were cast in the laboratory as well as field cores obtained from the Long-Term Pavement Performance pavement sections. Approximately 150 of the specimens were tested individually several times for assessment of repeatability of the test method. An analysis is presented of test differences observed, as is a sensitivity analysis of the CTE test variability on predicted performance based on the MEPDG. The differences in predicted international roughness index (IRI), percent slabs cracked, and faulting due to test variability were determined for concretes with CTEs ranging from 4 to 7 × 10−6 in./in./°F. It was observed that differences in test results may result in significant discrepancies in the predicted IRI, percent slabs cracked, and faulting. Thus, a single test result should not be used as representative of the CTE of a mixture due to the considerable impact of the test variability on the predicted pavement performance. Moreover, the specifications should state the minimum number of tests necessary for the CTE determination and the acceptable test variability.

Measurement of thermal expansion characteristic of root canal filling materials: Gutta-percha and Resilon

The purpose of this study was to evaluate the thermal expansion characteristics of injectable ther-moplasticized gutta-perchas and a Resilon. The materials investigated are Obtura gutta-percha, Diadent gutta-percha, E&Q Gutta-percha Bar and Epiphany (Resilon). The temperature at the heating chamber orifice of an Obtura II syringe and the extruded gutta-percha from the tip of both 23- and 20-gauge needle was determined using a Digital thermometer. A cylindrical ceramic mold was fabricated for thermal expansion test, which was 27 mm long, with an internal bore diameter of 3 mm and an outer diameter of 10 mm. The mold was filled with each experimental material and barrel ends were closed with two ceramic plunger. The samples in ceramic molds were heated in a dilatometer over the temperature range from to . From the change of specimen length as a function of temperature, the coefficients of thermal expansion were deter-mined. There was no statistical difference between four materials in the thermal expansion in the range from to (p > 0.05). However, Obtura Gutta-percha showed smaller thermal expansion than Diadent and Metadent ones from to (p

The use of flow behavior and thermal expansion to monitor structural change of amorphous Fe78Si9B13 ribbon

Samples of the amorphous Fe78Si9B13 ribbon were annealed isothermally and isochronally under different tensile stresses. These samples were also investigated using thermal expansion tests, DSC and XRD methods. The results show that a structural transition similar to the glass transition was found using thermal expansion method. Comparing the XRD patterns of the tensile stress annealed samples with those of stress free annealed samples, it is suggested that tensile stress promotes the crystallization.

Mechanical properties of copper‐clad laminate using composite naphthalene–phenyl‐based epoxy as prepreg

AbstractA composite was prepared that contained diglycidyl ether of tetrabromobisphenol A (DGETBA) and 1,5‐di(2,3‐epoxypropoxy)naphthalene (A), 4,4′‐bis(2,3‐epoxypropoxy)benzylideneaniline (B), or 4,4′‐bis(2,3‐epoxypropoxy)biphenyl (C), and then was cured using different ratios of dicyandiamide (DICY). The results of DSC, TGA, coefficient of thermal expansion, dielectric constant, and dissipation factor testing of the composite epoxy resins were analyzed, and investigation of the copper‐clad laminate using the composite epoxy resins as prepreg was also performed. Additionally, moisture absorption, peel strength, arc resistance, comparative tracking index, and flammability of the copper‐clad laminate were examined. Clearly, some of the physical or mechanical properties of the composite and the copper‐clad laminate can be improved by optimal addition of naphthalene–phenyl‐based epoxy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1485–1492, 2005

Properties of Crumb Rubber Concrete

Crumb rubber is a material produced by shredding and commutating used tires. There is no doubt that the increasing piles of used tires create environmental concerns. The long-term goal of this research is to find means to dispose of the crumb rubber by placement of the rubber in portland cement concrete and still provide a final product with good engineering properties. The Arizona Department of Transportation and Arizona State University have initiated several crumb rubber concrete (CRC) test sections throughout Arizona over the past few years. Laboratory tests were conducted to support the knowledge learned in the field and enhance the understanding of the material properties of CRC. Concrete laboratory tests included compressive, flexural, indirect tensile strength, thermal coefficient of expansion, and microscopic matrix analyses. The unit weight and the compressive and flexural strengths decreased as the rubber content in the mix increased. Further investigative efforts determined that the entrapped air, which caused excessive reductions in compressive strength, could be reduced substantially by adding a deairing agent. The higher tensile strains at failure observed from the tests were indicative of more ductile, energy-absorbent mix behavior. The coefficient of thermal expansion test results indicated that CRC was more resistant to thermal changes. The CRC specimens tested remained intact after failure and did not shatter as a conventional mix did. Such behavior may be beneficial for a structure that requires good impact resistance properties. If no special considerations are made to maintain higher strength values, the use of CRC mixes in places where high-strength concrete is not required is recommended.

Mechanical testing of ultra-high temperature alloys

Specially designed facilities for tensile testing of ultra-high temperature alloys are presented. Ohmic heating is chosen for easy access to the sample, fast attainable heating and cooling rates, simplicity in design and operation. Strain is measured with a video extensometer by means of the software SuperCreep. The algorithm for the strain measurements is described. Stability and accuracy of the test system were determined by testing an oxide dispersion strengthened Pt alloy. Performance of the video extensometer was checked by thermal expansion tests on pure Pt. Tensile tests of the oxide dispersion strengthened alloy Pt-10 wt% Rh DPH at 1600°C have proven the reliability of the equipment.

Mechanical, hygroscopic, and thermal properties of metal particle and metal evaporated tapes and their individual layers

AbstractMechanical and thermal properties of magnetic tapes and their individual layers strongly affect the tribology of magnetic head–tape interface and reliability of tape drives. Dynamic mechanical analysis, longitudinal creep, lateral creep, Poisson's ratio, the coefficient of hygroscopic expansion (CHE), and the coefficient of thermal expansion (CTE) tests were performed on magnetic tapes, tapes with front coat or back coat removed, substrates (with front and back coats removed), and never‐coated virgin films of the substrates. Storage modulus and loss tangent values were obtained at a frequency range from 0.016 to 28 Hz, and at a temperature range from −50 to 150 or 210°C. Longitudinal creep tests were performed at 25°C/50% RH, 40°C/25% RH, and 55°C/10% RH for 50 h. The Poisson's ratio and lateral creep were measured at 25°C/50% RH. CHE was measured at 25°C/15–80% RH. CTE values of various samples were measured at a temperature range from 30 to 70°C. The tapes used in this research included two magnetic particle (MP) tapes and two metal evaporated (ME) tapes that were based on poly(ethylene terephthalate) and poly(ethylene naphthalate) substrates. The master curves of storage modulus and creep compliance for these samples were generated for a frequency range from 10−20 to 1015 Hz. The effect of tape manufacturing process on the various mechanical properties of substrates was analyzed by comparing the data for the substrates (with front and back coats removed) and the never‐coated virgin films. A model based on the rule of mixtures was developed to determine the storage modulus, complex modulus, creep compliance, and CTE for the front coat and back coat of MP and ME tapes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1319–1345, 2004

Al-Si 합금에 Ni, Ce 첨가 효과와 압출온도의 영향

The effect of extrusion temperature on the microstructure and mechanical properties were studied in He-gas atomized <TEX>$Al_{81-(x＋y)}Si_{19}Ni_xCe_y$</TEX> alloy powders and their extruded bars using SEM, tensile testing and thermal expansion testing. The extruded bar of <TEX>$Al_{73}Si_{19}Ni_7Ce_1$</TEX> alloy consists of a mixed structure in which fine Si particles with a particle size below 20∼500nm and very fine <TEX>$Al_3Ni,\;Al_3Ce$</TEX> compounds with a particle size below 200nm are homogeneously dispersed in Al martix with a grain size below 500nm. With increasing extrusion temperature, the microstructural scale was decreased. The ultimate tensile strength of the alloy bars has incresed with decreasing extrusion temperature from 500 to 35<TEX>$0^{\circ}C$</TEX> and <TEX>$Al_{73}Si_{19}Ni_7Ce_1$</TEX> alloy extreded at 35<TEX>$0^{\circ}C$</TEX> shows a highest tensile strength of 810 MPa due to the fine namostructure. The addition of Ni and Ce decreased the coefficients of thermal expansion and the effects of extression temperature on the thermal expansion were not significant.

Detection of cavitation in rubber phase of rubber toughened poly (methyl methacrylate) using thermal contraction measurements

Measurements of mechanical properties and thermal expansion–contraction behaviour have been carried out on plain PMMA and on a transparent grade of rubber toughened (RT) PMMA. Uniaxial tensile tests at 23°C show that the stress–strain (σ–ε) curve for the RTPMMA begins to deviate from linearity at ε ≈ 1·5%, and reaches a load maximum at ε ≈ 6·7%. Visible whitening begins at ε ≈ 1·5%, and intensifies with increasing strain, but annealing for 3 h at 115°C restores the material to its initial transparent condition. Thermal expansion and contraction tests show that pre-straining to ε ≥ 2% produces a marked decrease in the coefficient of thermal expansion (CTE) of RTPMMA over the temperature range -20 to +50°C, where the rubber is above its Tg. Lower pre-strains have little effect on expansion–contraction behaviour. Annealing after pre-straining leaves the CTE unchanged at its reduced value if the pre-strain is above 3%. However, it causes an increase in CTE towards its initial value in specimens pre-strained to ε= 2%. This work provides clear evidence for cavitation in the rubber particles. It also shows that annealing after pre-straining does not completely restore the rubber's resistance to cavitation. Creep tests at 23°C on pre-strained specimens, both before and after annealing, demonstrate that rubber particle cavitation promotes a substantial acceleration in strain rates.

Critical load of reversible thermal expansion of tyranno fiber.

To develop the high temperature shape memory bi-ceramics, the thermal expansion test was performed for Si-C-O glassy tyranno fiber which shows high resistant to heat and oxygen. The reversible shape change can be observed for Si-C-O glassy fiber sample under 1573K and below 25MPa.

Inelastic Response of a Woven Carbon/Copper Composite, Part I: Experimental Characterization

This paper presents the results of an extensive mechanical characterization of a new woven metal matrix composite, namely 8-harness (8H) satin carbon/copper (C/Cu). While woven polymer matrix composites have existed for some time, woven metal matrix composites such as C/Cu are now being developed for the first time. Due to the high thermal conductivity of the copper matrix, this material system is a good candidate for high heat flux applications such as those associated with space power radiator panels and computer chip casings. The mechanical characterization of the 8H satin C/Cu composite was carried out using monotonic and cyclic tension, compression, and Iosipescu shear tests, as well as combined tension-compression tests. Experiments involving applied compression were performed using a novel gripping apparatus not previously described in the open literature. Specimens containing small amounts of chromium and titanium in the copper matrix, in addition to specimens with pure copper matrix, were tested in order to investigate the effect of these alloying elements on the mechanical response. Previous data from thermal expansion and mechanical tests on unidirectional C/Cu composites suggested that the addition of small amounts of these alloying elements to the copper matrix improved the fiber/matrix bond. In addition to the monotonic and cyclic stress-strain response generated using the three types of mechanical tests, a summary of initial moduli, yield stress, and ultimate strength data for this novel woven metal matrix composite is provided and contrasted with the corresponding pure copper data. Further, the presented results provide a basis for validating a new micromechanical model developed by the authors for woven metal matrix composites which is the subject of Parts II and III of this paper.

The effect of solidification conditions on phase transformation of iron matrix of Fe-25mass%Cr-C-B alloys

M2B, M23(C,B)6 and M7(C,B)3 compound phases which constitute the eutectic structures of Fe-25mass%Cr-C-B alloys vary depending on both carbon and boron content. The composition of the matrix structure also varies with each eutectic structure. Due to this, it is presumed that the transformation behavior of the matrix is affected by the solidification rate of the cast material. In the present research, three kinds of molds are used in changing the solidification rate, namely, an exothermic mold, a sand mold and a metal mold. The alloys made from each mold are subjected to thermal expansion tests in order to clarify the transformation behavior both in furnace cooling and air cooling conditions. The results indicate that the hardness of each alloy is higher in a mold where solidification is faster. Most of the alloy transform to martensite during air cooling. In furnace cooling, low carbon with high boron alloys transform to bainite, whereas, high carbon alloys transform to pearlite. Furthermore, alloys with lower carbon content have ferritic matrix which does not transform to any other structure in any cooling condition.