Stress-temperature Measurements Research Articles

A review of non-destructive evaluation techniques for axial thermal stress and neutral temperature measurement in rail: Physical phenomena and performance assessment

Thermal buckling of continuous welded rail (CWR) has been a long-standing challenge for the railroad industry because of the high derailment rate and the associated social, economic, and environmental impacts it causes. Rail buckling is generally attributed to excessive thermally-induced axial compressive stress developed in the rail from high temperatures. Knowing the rail thermal stress or its rail neutral temperature (RNT) is critical for safe and efficient rail system operation. There has been great interest and much work on the development of nondestructive evaluation (NDE) techniques to estimate rail thermal stress and RNT in situ. This paper reviews the findings and conclusions from research about NDE approaches for estimating rail thermal stress or RNT, emphasizing the physical phenomena and performance interpretation related to each of the approaches. We identify the type of reference measurements each technique relies on and tabulate this information showing key assumptions, performance, and limitations for each technique.

Thermoelastic characterization of carbon nanotube reinforced PDMS elastomer

Abstract Internal energy and entropy contribution to the elasticity of carbon nanotube reinforced polydimethylsiloxane (PDMS) is evaluated using statistical theory of rubber elasticity. Stress–temperature measurements were performed and the data was used to calculate the internal energy contribution to elastic stress. Interesting aspects such as increase in energy and low entropy contribution to the elasticity of carbon nanotube reinforced PDMS is observed. This can be related t o the deformation behavior of the network chains of pristine elastomers and the directional reorientation of nanotube entanglements. While the entropy change is associated with reorientation or directional preference of the carbon nanotube entanglements, the internal energy change is associated with structural bending or stretching of the nanotubes. A reversible deformation of nanotube entanglements complements rubber like elasticity and the present study gives insights into the thermoelasticity of reinforced elastomers as well as the elastic behavior of carbon nanotube entanglements inside a polymer matrix.

Thermal stability of amorphous Ti-B-Si-N coatings with variable Si/B concentration ratio

Due to their homogenous structure without grain boundaries, amorphous nitride-based coatings represent a potentially attractive material for high-temperature applications in aggressive environment. In this article, we report on the thermal stability and mechanical properties of amorphous quaternary Ti-B-Si-N coatings with variable Si/B concentration ratio prepared by reactive magnetron co-sputtering. Biaxial stress temperature measurement was used to evaluate thermal stability of amorphous as-deposited coatings in the region up to 600°C. The chemical composition of the coatings was stable up to 1100°C. During the annealing small amount of nanocrystalline fcc-TiN phase (with grain size of 1–4nm) in amorphous matrix a-(Ti)BSiN was formed. The prevailing BN, SiN and TiN bonds remained also unchanged as observed by X-ray photoelectron spectroscopy. The gradual increase of hardness to maximum at 14GPa and the overall positive effect on thermal stability was observed with increasing Si/B concentration ratio. The dominating volume of the amorphous phase after annealing had a significant influence on maintaining constant hardness values up to 1100°C.

Investigation of strain induced effect on linear shape fiber Bragg grating embedded in composite material

In this work experimental results are presented of strain induced effects on a linear shape fiber Bragg grating embedded in a composite material. Mechanical analysis of the composite material has been numerically performed by using commercially available software Ansys. Advanced Bragg gratings make it possible to simplify detection systems, calibration process of fiber optic sensors and quasi – spot metering. Full Text: PDF References P. Kisała, "Optoelectronic sensor for simultaneous and independent temperature and elongation measurement using Bragg gratings", Przegląd Elektrotechniczny 11a, 343 (2012). DirectLink X. Wen, D. Zhang, Y. Qian, J. Li, N. Fei, "Improving the peak wavelength detection accuracy of Sn-doped, H2-loaded FBG high temperature sensors by wavelet filter and Gaussian curve fitting", Sensors Actuat. A: Phys. 174, 91 (2012). CrossRef H. Peng, Y. Su, Z. Ye, B. Zhou, "A novel fiber Bragg grating sensor for weak pressure measurement based on the Stokes parameter", Opt. Fiber Technol. 18(6), 485 (2012). CrossRef G. Luyckx, E. Voet, N. Lammens, J. Degrieck, "Strain Measurements of Composite Laminates with Embedded Fibre Bragg Gratings: Criticism and Opportunities for Research", Sensors 11, 384 (2011). CrossRef S. Yashiro, N. Takeda, T. Okabe, H. Sekine, "A new approach to predicting multiple damage states in composite laminates with embedded FBG sensors", Composites Science Technol. 65, 659 (2005). CrossRef Y. Zhan, L. Li, F. Yang, K. Gu, H. Wu, M. Yu, "An all-fibre multi-parameter sensor for composite structures based on a chirped fibre Bragg grating", Opto-Electron. Rev. 21(3), 283 (2013). CrossRef Y. Okabe, R. Tsuji, N. Takeda, "Application of chirped fiber Bragg grating sensors for identification of crack locations in composites", Composites: Part A 35, 59 (2004). CrossRef S. Yashiro, T. Okabe, N. Toyama, N. Takeda, "Monitoring damage in holed CFRP laminates using embedded chirped FBG sensors", Intern. J. Solids Structur. 44, 603 (2007). CrossRef C. Fernandez-Valdivielso, I.R. Matoas, F.J. Arregui, "Simultaneous measurement of strain and temperature using a fiber Bragg grating and a thermochromic material", Sensors Actuat. A: Phys. 101, 107 (2002). CrossRef A. Makovec, G. Berruti, M. Consales, M. Giordano, P. Petagna, S. Buontempo, G. Breglio, Z. Szillasi, N. Beni, A. Cusano, "Radiation hard polyimide-coated FBG optical sensors for relative humidity monitoring in the CMS experiment at CERN", J. Instrumentation 9(3), C03040 (2014). CrossRef P. Kisała, "Detection of material defects with indirect metod by determining the linear expansion with FBG sensor", Przegląd Elektrotechniczny, NR 1a, R. 89, 29 (2013). DirectLink A. Papantoniou, G. Rigas, N.D. Alexopoulos, "Assessment of the strain monitoring reliability of fiber Bragg grating sensor (FBGs) in advanced composite structures", Composite Structur. 93, 2163 (2011). CrossRef Y. Okabe, R. Tsuji, N. Takeda, "Application of chirped fiber Bragg grating sensors for identification of crack locations in composites", Composites: Part A 35, 59 (2004). CrossRef P.Lesiak, M.Szeląg, D.Budaszewski, R.Plaga, K.Mileńko, G.Rajan, Y.Semenova, G.Farrell, A.Boczkowska, A.Domański, T.Woliński, Influence of lamination process on optical fiber sensors embedded in composite material", Measurement, Vol. 45, Issue 9, November 2012, Pages 2275–2280. CrossRef P. Lesiak, M. Szeląg, K. Mileńko, T. Woliński, A. Domański, K. Jędrzejewski, A. Boczkowska, "Polarimetric and Bragg Optical Fiber Sensors for Stress Distribution and Temperature Measurements in Composite Materials", Acta Phys. Polonica A 120, 698 (2011). CrossRef A.W. Domański, P. Lesiak, K. Milenko, A. Boczkowska, D. Budaszewski, S. Ertman, T.R. Woliński, "Temperature-insensitive fiber optic deformation sensor embedded in composite material", Photon. Lett. Poland 1(3), 121 (2009). CrossRef

Advanced characterization methods for wear resistant hard coatings: A review on recent progress

Abstract Due to economical demands to further increase the efficiency of production processes, it is essential to exploit the full potential of wear resistant hard coatings. This is, however, possible only if the coating microstructure and properties are well characterized. Thus, in the present work, recently suggested advanced characterization techniques for coatings are reviewed. The application of atom probe tomography, electron backscatter diffraction and synchrotron X-ray nanodiffraction enables previously unrevealed insights in their chemical composition, microstructure and crystallographic structure. For the determination of mechanical and tribological properties at elevated temperatures, high-temperature nanoindentation and high-temperature ball-on-disk tests in combination with in-situ measurement techniques are discussed. Utilization of micromechanical tests for coatings provides information about their fracture toughness and rupture strength. High-temperature X-ray diffraction and biaxial stress temperature measurements for the determination of the coefficient of thermal expansion are compared. The thermal conductivity as well as the specific heat capacity of coatings can be studied using the 3- ω technique, time domain thermoreflectance and differential scanning calorimetry. The introduced portfolio of characterization techniques enables the determination of a complementary microstructural, mechanical and thermo-physical fingerprint of wear resistant hard coatings, which allows to understand the complex structure–property relations in these materials and subsequently to further improve their performance.

전기자동차용 조향장치 제어 ECU 구조의 열해석에 관한 실험적 연구

The technical development of electric vehicles has been actively proceeding because of the reduction of oil resources and need for eco-friendly vehicle technology. In particular, an electronic control unit is an important element in the technology of electric vehicles due to the motor drive system. This paper concerns an experimental study on the thermal analysis of the steering control ECU structure for an electric vehicle. The ECU unit is designed for eight heat sinks for the thermal analysis of the ECU structure. The thermal analysis characteristics of the ECU structure are evaluated by the temperature distribution, heat flow, von Mises stress, total translation, and external surface temperature measurement of the ECU unit.

Exertional heat illness: emerging concepts and advances in prehospital care.

Exertional heat illness is a classification of disease with clinical presentations that are not always diagnosed easily. Exertional heat stroke is a significant cause of death in competitive sports, and the increasing popularity of marathons races and ultra-endurance competitions will make treating many heat illnesses more common for Emergency Medical Services (EMS) providers. Although evidence is available primarily from case series and healthy volunteer studies, the consensus for treating exertional heat illness, coupled with altered mental status, is whole body rapid cooling. Cold or ice water immersion remains the most effective treatment to achieve this goal. External thermometry is unreliable in the context of heat stress and direct internal temperature measurement by rectal or esophageal probes must be used when diagnosing heat illness and during cooling. With rapid recognition and implementation of effective cooling, most patients suffering from exertional heat stroke will recover quickly and can be discharged home with instructions to rest and to avoid heat stress and exercise for a minimum of 48 hours; although, further research pertaining to return to activity is warranted.

Polarimetric and Bragg Optical Fiber Sensors for Stress Distribution and Temperature Measurements in Composite Materials

Composite structures are made from two or more constituent materials with significantly different physical or chemical properties and they remain separate and distinct in a macroscopic level within the finished structure. This feature allows us for introducing an optical fiber sensors matrix into the composite material. These sensors can demonstrate stress distribution inside a tested material influenced by external tensions. Two types of the optical fiber sensors, placed into one fiber simultaneously, are used as s matrix structure. One of them is based on application of the Bragg grating structure written inside the core of the fiber. Longitudinal stress modifies changes parameters of the Bragg grating and in the same, spectral characteristics of the light transmitted through the fiber. The second one is based on application of highly birefringent fibers which under external stress introduce polarization changes in the output light. These sensors placed into one fiber give a possibility to the measure two external tensions separately.

Structure, mechanical properties and oxidation behaviour of arc-evaporated NbAlN hard coatings

Nb 1 − x Al x N hard coatings were synthesised by cathodic arc-evaporation in order to study the influence of the Al concentration on crystal structure, mechanical properties and oxidation resistance. Structural investigations by X-ray diffraction revealed a transition from the face-centered cubic structure of δ-NbN to the wurtzite structure of AlN at x = 0.45… 0.56 depending on the deposition parameters. The maximum values of the mechanical properties like hardness and residual stress obtained by nanoindentation and biaxial stress temperature measurements, respectively, were found for the coatings with cubic structure and generally decrease with increasing Al content. On the other hand, higher Al concentrations are beneficial in terms of oxidation resistance as shown by annealing experiments in ambient air. The onset temperature for oxidation rises from 600 to 700 °C for Nb 0.73Al 0.27N to above 800 °C for Nb 0.29Al 0.71N regardless of changes in the crystal structure.

MEMS fabrication based on nickel-nanocomposite: film deposition and characterization

Electrosynthesized metal-nanocomposites represent a unique class of microelectromechanical systems (MEMS) structural material due to their compatibility with MEMS and CMOS fabrication technologies via a one-step, selective on-chip deposition process at low temperatures (∼50–90 °C). In this paper, particle-reinforced, electrosynthesized nickel-nanocomposites of various compositions have been successfully demonstrated as potential structural materials for MEMS. We have achieved low-temperature, stress-free, wafer-level fabrication of nano-composite MEMS via both an electroless nickel (EN) and an electrolytic nickel (EL) deposition process, with the addition of uniformly dispersed micro- and nanoparticles of either cordierite (diameter ≈ 100 nm–5 µm) or diamond (diameter ∼ 4 nm). The as-deposited nickel-cordierite films exhibit better thermal compatibility with silicon, compared to nickel. The measured coefficients of thermal expansion (CTE) of EN-cordierite and EN are 17.34 ppm K−1 and 26.69 ppm K−1, respectively. Stress–temperature measurement of EN-cordierite composite also confirms that residual stress decreases with the incorporation of cordierite. Finally, by adding various concentrations of nanodiamond particles into an EL matrix, it is found that higher diamond concentration renders these films more compressively stressed.

Effect of O2 flow ratio on the microstructure and stress of room temperature reactively sputtered RuOx thin films

RuO x thin films were deposited at room temperature by reactive radio frequency magnetron-sputtering using Ar∕O2 discharges of varying O2 flow ratio (fO2) over the range 10%–50% and were characterized using x-ray diffraction, x-ray reflectivity, x-ray photoelectron spectroscopy, resistivity, and stress-temperature measurements. With the increase of fO2, the film texture changed from (110) to (101). Films deposited with fO2>25% were determined stoichiometric. The residual stresses in as-deposited films were all compressive and increased with addition of O2, except for the film sputtered at fO2=20% which was in biaxial tension. The film deposited at fO2=30% had a low resistivity value of 68μΩcm and near zero stress (<50MPa tensile) after a thermal cycle in air up to 500 °C which is promising for use in microdevices.

Characterization of Low-Temperature Stress Hump in Relation to Phase Formation Sequence of Nickel Silicide

The stress hump phenomenon observed at a low temperature of approximately 140°C during in situ stress-temperature measurement of sputtered Ni thin film on a (001) Si substrate has been investigated. We found that the stress hump was not related to the formation of NiSi2, but originated from the thickening of an amorphous Ni–Si intermixing layer in the temperature range of 100–140°C followed by the formation of the Ni2Si phase at temperatures above 140°C.

Effect of SiO 2 intermediate layer on Al 2O 3/SiO 2/n +-poly Si interface deposited using atomic layer deposition (ALD) for deep submicron device applications

Electrical and reliability characteristics of several Si/Al 2O 3 (barrier layer)/Si capacitor structures have been investigated. Al 2O 3 film was deposited by atomic layer deposition (ALD). ALD Al 2O 3 was found to be a good chemical oxide barrier layer which is important for achieving thin oxide thickness. Formation of a metallic Al cluster was observed at the Al 2O 3/n +-doped Si interface layer. SiO 2 formed by O 2 flushing at 400°C for 10 min was found to be very effective to prevent the formation of a metallic Al cluster and to reduce the leakage current to less than 1×10 −15 A/μm 2 at an applied voltage of 2.0 V. In situ stress–temperature measurement of Al 2O 3/SiO 2/n +-doped poly Si was carried out to evaluate the residual stain of the film. Average interband oscillator energy of the Al 2O 3 film on SiO 2 is greater than that of Al 2O 3 film on Si(100) by 1.162 eV. Al 2O 3 films exhibited excellent interface quality, dielectric reliability, and shrinkability. The capacitor using Al 2O 3 film satisfied the requirement for cell capacitance of 25 fF/cell in 0.30-μm pitched DRAMs.

Stress development in FeAl8 thin films during heat treatment

The development of biaxial stress in FeAl8 thin films was investigated during annealing in vacuum. The heat treatment leads to irreversible changes in the microstructure of the FeAl8 thin films, which were determined by stress–temperature measurements, transmission electron microscopy, and X-ray diffraction. The stress development is explained by semiquantitative considerations of atomic rearrangement (excess-vacancy annihilation, grain-boundary relaxation, and grain growth). The stress development between 180 and 400°C is affected by grain-boundary relaxation, and between 450 and 675°C by grain growth. The high thermal stability, which was measured in previous investigations, could not be confirmed.

Abnormal grain growth of sputtered CuNi(Mn) thin films

The evolution in both stress and microstructure was investigated on sputtered Cu0.57Ni0.42Mn0.01thin films of 400 nm thickness during the first temperature cycle up to 550 °C. Samples from stress–temperature measurements up to various maximum temperatures were analyzed by x-ray diffraction, scanning and transmission electron microscopy, and Auger electron spectroscopy. The columnar grains with lateral diameters of about 20 nm in the as-deposited state coarsen to about 400 nm above 300 °C. Probably due to the impurity (Mn) drag effect, the coarsening occurs by abnormal grain growth rather than by normal grain growth, starting near the film–substrate interface. The stress development results from a combination of densification due to grain growth and plastic stress relaxation.

Stress, microstructure, and stability of Mo/Si, W/Si, and Mo/C multilayer films

The stresses in periodic Mo/Si, W/Si, and Mo/C multilayer films were determined from wafer-curvature measurements. The layer thickness of each material was varied systematically, and parametric stress contours were generated, showing contours of constant stress in the two-dimensional layer thickness parameter space. These results illustrate that the net stress in a periodic multilayer is not an intrinsic property of the film (for specific deposition conditions) but, rather, depends strongly on the individual layer thicknesses. X-ray diffraction measurements show (a) how the lattice spacing in the W and Mo crystallites varies with layer thickness, and (b) in the case of the W/Si films, how the phase composition of the polycrystalline W layers vary with W layer thickness. In the case of the W/Si and Mo/Si multilayers, irreversible stress changes were observed after the samples were stored in air at room temperature for a period of several months. Stress–temperature measurements made on the as-deposited W/Si and Mo/Si samples also reveal irreversible stress changes (both positive and negative, depending on the layer thicknesses) after thermal cycling to 300 °C; x-ray diffraction measurements were used to identify any associated changes in the W and Mo microstructure. We describe mechanisms that can explain the observed stress behavior, and also discuss the significance of these results, particularly with regard to the use of these films for high-performance multilayer x-ray optics.

Mechanical Stress, Grain-boundary Relaxation, and Oxidation of Sputtered CuNi(Mn) Films

This paper focuses on understanding stress development in CuNi42Mn1 thin films during annealing in Ar. In addition to stress-temperature measurements, resistance-temperature investigations and chemical and microstructural characterization by Auger electron spectroscopy, scanning and transmission electron microscopy, x-ray diffraction, and atomic force microscopy were also carried out. The films are polycrystalline with a grain size of 20 nm up to 450 °C. To explain the stress evolution above 120 °C, atomic rearrangement (excess-vacancy annihilation, grain-boundary relaxation, and shrinkage of grain-boundary voids) and oxidation were considered. Grain-boundary relaxation was found to be the dominating process up to 250–300 °C. A sharp transition from compressive to tensile stress between 300 and 380 °C is explained by the formation of a NiO surface layer due to reaction with the remaining oxygen in the Ar atmosphere. This oxidation is masking the inherent structural relaxation above 300 °C.

Development of Mechanical Stress in Cuni(mn) Films During Temperature Ramping: Related Mechanisms

ABSTRACTThis paper focusses on the development of biaxial stress in Cu0.57Nio.42Mno.ol thin films during annealing in Ar and, for comparison, in vacuum. Besides stress-temperature measurements also resistance-temperature investigations as well as chemical and microstructural characterization by Auger electron spectroscopy, scanning and transmission electron microscopy, and X-ray diffraction were carried out. To explain the stress evolution, atomic rearrangement (excessvacancy annihilation, grain-boundary relaxation, and shrinkage of grain-boundary voids) and oxidation were considered. Up to 250 - 300 °C grain-boundary relaxation was found to be the dominating process. A sharp transition from compressive to tensile stress between 300 °C and 380 °C is explained by the formation of a NiO surface layer

Energy Storage And Recovery In Thin Metal Films On Substrates

ABSTRACTDislocation segments which extend through the thickness of a film can move through the film only if dislocation line length is deposited or removed at the film/substrate and film/passivation (if any) interfaces. The dislocation density and, therefore, the energy stored in the film increase during plastic deformation. The reverse process, that is, the reduction of strain energy in the film by the reduction of dislocation line length, is here suggested to be the origin of a number of unexplained features of experimentally obtained stress-temperature curves, including very low (or even “negative”) yield stresses in compression, tensile-compressive flow stress asymmetries, increasing strength with increasing temperature upon heating, and a very strong Bauschinger-like effect which has been seen in thin Cu films. The results of stress-temperature measurements of passivated Cu thin films on silicon substrates are presented.

Microstructure - Stress - Property Relationships in Nanometer Ge/C Multilayers

ABSTRACTA series of sputtered as-prepared and annealed Ge/C multilayer structures with periods ranging from 2 to 8 nm has been studied with high resolution transmission electron microscopy (HRTEM), x-ray scattering, and stress measurement techniques. Ge/C multilayers have potential applications as normal incidence reflective mirrors near 4.4 nm wavelength. The reflectivity and stress in these structures depend on the microstructural evolution of the component layers. The as-prepared structure of both Ge and C layers appear amorphous from TEM imaging and diffraction. Annealing at 500°C for 60 minutes leads to crystallization of the Ge layers. As the phase diagram indicates, no carbide compound has been found. X-ray scattering reveals that the multilayer period expands by as much as 10% after annealing. Both TEM images and x-ray profiles suggest that the layer structures remain well-defined upon annealing. In-situ stress-temperature measurements directly show the Ge/C multilayer microstructure evolution path. X-ray measurements show that the structures with periods near 2 nm undergo a significant improvement on optical performance with annealing. The physical mechanisms that may have caused the optical enhancement are discussed. Correlation of the stress evolution in the multilayers and in individual layers during annealing, and their relationships to the microstructures and optical properties are examined.