The strength ratio R has features that make it a convenient parameter to incorporate into a failure theory: (1) if the applied stress or strain is zero, R = ; (2) the stress/strain level is safe if R > 1; (3) the stress/strain level is unsafe if R = 1; and (4) there is no physical significance if R < 1.

This expression can now be solved for F12, with. Applications for ingot moulds, cylinder heads, brakedrums and discs and manifold castings are typical. It should be inspected after half of this = 4.7 years (ANS). The TsaiWu theory [20] has a form similar to that of several other interactive theories presented in Table 5.2. After sintering, half of the samples were vacuum annealed at 1200C for 2h in a 106torr vacuum. Figure 7.49. Which of the following processes requires filler rods to be added by hand? The method generally used for bond strength measurement is the modified ASTM direct pull test (ASTM C 633-79) using an epoxy adhesive. The material was sintered at two temperatures in pure hydrogen 1480C and 1490C. Compacted graphite irons have intermediate thermal conductivity values between flake and nodular iron and comparative figures are given in Table 26.65. "global warming" MECHANICAL PROPERTIES OF NODULAR IRONS. Deo, in Minimization of Welding Distortion and Buckling, 2011. 8-27). With thermal cycling to 1130C (2066F), the interface bond strength decreases significantly, initially rapidly within the first 100 cycles. At present no British Standard exists for these materials. Value in bracket is Charpy V notch strength at 20C in J. Minimization of bowing distortion in welded stiffeners using differential heating*, Minimization of Welding Distortion and Buckling, During welding, the high temperature at the weld region causes compressive stress because the thermal expansion in this region and restraint by the surrounding metal at lower temperature. The exact value of F12 cannot be explicitly determined, but there are bounds imposed on it by geometric considerations [31]. At present the production of compacted graphite irons is largely based on additions of magnesium and/or cerium to irons of low sulphur content. Among the identified and reported agents for anodic SCC, the most common are hydroxides (caustic), nitrates, carbonates, phosphates, CO-CO2-H2O and aqueous chlorides, and among the less common are ammonia, high purity water containing oxygen, phosphorus trifluoride, sulphuric acid, hydrogen-antimony/aluminium chloride and MgCl2-NaF. For compression the predicted failure stress (using X' and Y' instead of X and Y) is x = 19 ksi. This information should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional. Heat treatment: Castings to be stripped from moulds while hot and as soon as possible after solidification, the hot castings to be charged to a furnace preheated to approximately 600C and kept at this during charging. Then heat to not less than 750C and not more than 850C. Some theories showed good correlations and some did not. Similarly, infiltration of steel powder with copper base alloys is employed in the production of gears. Figure E5.5-1. Typical heavy alloy properties. Each curve is the centre of a band of variation in strength of about 30 MPa ( 2tonf/in2). Technol., 1999, 120121, 5360). The outstanding characteristics are good thermal conductivity combined with useful ductility and higher tensile and fatigue strengths than for grey irons. Hence it has 9.525 7.14mm = 2.385mm to corrode at0.254mm/yr = 9.4 years. thick, 48 in. Sudhangshu Bose, in High Temperature Coatings, 2007. The resulting green compacts are like pharmaceutical pills that crumble under stress and mishandling. 2003, Michaleris and DeBiccari, 1996c). During sintering, the particles are first wet and may rearrange in the melt. Originally, Tsai and Wu [20] suggested that a 45 off-axis tension or shear test would be good for determining F12. Individual value. The magnesium based treatments are similar to those employed for nodular graphite iron production while the cerium methods are usually simple ladle addition processes. Effect of vacuum anneal on the mechanical properties of a 95wt%W heavy alloy. and kS1, kS2, , kSi, second-order rate constant kS1, kS2, , kSi. With = 0 the failure criterion can be put into the form (F111 + F122 + F1)1 + (F222 + F121 + F2)2 1 = 0. Word(s) in meaning: chat Typically, solution annealing at 9001300C and subsequent quenching can avoid impurity segregation and formation of intermetallic phases. Tsai and Hahn [31] extended the use of a failure theory by defining an additional variable, the strength ratio R, such that ia = Ri. The appropriate form of a solution for defining a failure envelope is a closed surface, such as an ellipse. Deo and Michaleris (2002) verified the 2-D and 3-D finite element analysis technique for the stiffeners using experimental data. Not all alloys produce SCC in all environments, and the specificity is related to either adsorption or the ability to produce a borderline passivity condition for SCC to occur. In order to predict life of the TBC and develop a failure model, the degradation of the bond strength needs to be complemented with evolution of residual stress, and understanding of initiation and growth of critical flaws. High longitudinal tensile stresses in the weld region cause longitudinal bending or bowing of the stiffener. However, they are referred as anodic SCC and cathodic SCC as well [6] and it has been suggested that SCC under both anodic and cathodic conditions is fundamentally the same process [7]. Following a similar procedure for the 22 stressstrain space as shown in Figure 5.7 yields similar results for F22 and F2: Similarly, application of a pure shear stress results in, Solving these equations yields expressions identical in form to those for F11, F22, F1, and F2. In the design and analysis of components using composite materials, the failure theory only answers the question of failure for a given state of stress. Atomic hydrogen produced as a result of anodic dissolution or corrosion, so to say, is the cause of hydrogen embrittlement in many cases, but quite a few other sources of hydrogen are readily available in environmental and industrial exposures. In the magnesium process, as the magnesium content is increased, the graphite structure changes from conventional flake, through compacted flake to fully nodular. They behave elastically over a range of stresses although their limit of proportionality is lower than nodular irons.

As a variation to establishing failure ellipses, consider the unidirectional lamina in Figure E5.6. to exceed the adhesive strength of the particular epoxy used in the pull test, 41.4 MPa (6 ksi), because the failure had occurred in the epoxy. A correlation of various strength theories with experimental results for paperboard is presented in Schuling et al. In this case the failure criterion becomes F112+2F122+F222+F1+F2=1. For an orthotropic lamina subjected to plane stress (3 = 13 = 23 = 0) this reduces to. The data exhibit the following general trend: The average interface bond strengths of the TBCs in the as-coated condition for most of the substrates are in excess of 60 MPa (8.6 ksi). All of the content is provided as is, without warranty of any kind. To determine F12 a normalized interactive term is introduced: The admissible range of values for F*12 and its associated curve are, Using F12=F12*F11F22, the failure criterion can be written as. In an E7018 electrode, what does the 1 refer to? NASA, Failure occurs at a time, which corresponds with the intersection of the residual stress and bond strength curves. For an EB-PVD coated PWA 1484/NiCoCrAlY system, the as-coated bond strength was estimated by Meier et al. web, 3/16 in. Table 26.68. Either low-melting powder blended into the compact or external infiltrants that penetrate the compact surface pores by capillary wicking action during sintering are the source of the liquid. Table21.4 provides an overview of some typical properties. aqueous chlorides, sulphuric acid, hydrogen-antimony/aluminium chloride) have been reported to produce cathodic SCC as well. The subscript a means allowable or ultimate stress. Postal codes: USA: 81657, Canada: T5A 0A7. Tungsten heavy alloys are of engineering interest due to their uniquely high density and mechanical properties. Magnesium and titanium are usually present in the ranges 0.0150.035 per cent and 0.080.15 per cent respectively with a trace of cerium. E = 0.6 for furnace butt welded pipe Y = 0.4 for ferritic pipe. Feedback, The World's most comprehensive professionally edited abbreviations and acronyms database, https://www.acronymfinder.com/Kips-Per-Square-Inch-(engineering)-(KSI).html, Korean Society for Horticultural Science (South Korea), Kansas State High School Activities Association, Kali Sikaran International (martial arts), Killed or Seriously Injured (UK road safety statisitcs), Killing Service Incorporated (gaming clan), Kinetic Systems, Inc. (various locations), Knattspyrnusamband slands (football association of Iceland), Knowledge, Strength, Integrity (gaming community), Kommando Schwarze Infusion (German: Command Black Infusion), Kovack Securities, Inc. (Ft. Lauderdale, FL), Kyoto Sustainability Initiative (Kyoto, Japan). Variation of tensile strength with cast-section size for ferritic and pearlitic compacted graphite irons of various carbon equivalents. This equation describes a family of ellipses. Therefore, the compressive stress in the weld zone exceeds the yield stress at the corresponding temperature. These alloys are susceptible to hydrogen embrittlement and are exposed to hydrogen during the sintering operation, thus hydrogen outgassing can be required to enhance the ductility of the alloy. Dawes (1965) analyzed the residual stresses in welded I beam connections. 18 in std has wall thickness of 0.375 in = 9.525mm. Details of residual stress profile in the TBCs have already been covered. [34]. (b) Bond strength of as-coated samples with two different bond coats (Maurice Gell, Eric Jordan, Krishnakumar Vaidyanathan, Kathleen McCarron, Brent Barber, Yong-Ho Sohn, and Vladimir K. Tolpygo, Bond strength, bond stress and spallation mechanisms of thermal barrier coatings, Surf. (2003) and by Michaleris and DeBiccari (1996b, 1997). The TsaiWu failure theory can also be expressed in terms of strain. On completion of the welding cycle, the temperature drops to room temperature. F*12 governs the slenderness ratio and the inclination of the major axis, which is +45 for -F*12 and 45 for +F*12. These tensile stresses are caused by the longitudinal bending distortion. 26.6). The TsaiWu theory predicts two roots, one for a tensile stress and one for a compressive stress. The type of surface defined depends on the sign of the determinant formed by the stress coefficients, called the discriminant [32]. From a design viewpoint it is equally important to identify the additional stress to which a component may be subjected prior to failure. Irons produced by magnesiumtitaniumcerium treatment. In general, the form presented by Tsai and Hahn [31] appears to be better suited to more highly anisotropic materials such as graphite/epoxy than other representations. Enter the value (for example, 15) into the left, Alternatively, you can enter the value into the right. Such irons are characterised by the graphite being present in the form of relatively short, thick flakes with rounded extremities and undulating surfaces. For a specimen in uniaxial tension, the generalized criterion for failure involving strength ratios can be expressed as. CORROSION RESISTING HIGH SILICON CAST IRONS. Distribution of residual stress in the web of the stiffener. Cool slowly after soak to 300C before unloading. Figure 5.7. Vanli and Michaleris (2001) investigated the distortion of welded stiffeners with a particular emphasis on the prediction of bowing, buckling and angular distortion using decoupled 2-D and 3-D finite-element analysis technique developed by Deo et al. Although the existence of compacted graphite containing irons has been known for many years, it is only relatively recently that they have been commercially exploited. An analogous development can be made for strain [31]. The solution of this equation involves two roots, R and R', applicable to either the tensile (R) or the compressive (R') failure strength. The bowing distortion in the stiffeners was found to be large as predicted. Figure E5.5-2. J.L. For conventional SCC, the specificity of environment is a distinct characteristic feature. Because of this, the TsaiWu failure reduces to, The only remaining term to be determined is F12. It is possible to define five of the six parameters from simple test procedures. Plane stress components for failure analysis using the Tsai-Wu tensor theory. On the other hand, any environment providing atomic hydrogen can lead to hydrogen embrittlement. The stress pattern reverses from compressive to tensile at locations that have plastified during welding and residual stress is developed at the material yield level (at room temperature) in the weld region.

The interactive term is generally established from experiments in which = 0. Milton Ohring, in Engineering Materials Science, 1995. Value in brackets is mean of 3 tests. A biaxial tension test can be difficult to perform and cannot generally be used to define F12. Coat. Which of the following processes uses filler supplied on a reel? A theoretical test procedure by Evans and Zhang [30] has been proposed for determining F12 They suggest a series of tests in which deformations in the directions transverse to the applied load are zero, as shown schematically in Figure 5.8. This definition appears somewhat frequently The chapter reviews the stress corrosion cracking (SCC) of steels containing less than approximately 5% total alloying elements and having yield strengths of less than about 1240MPa (180 ksi) of basic microstructural types of ferritic-pearlitic or tempered martensite (YS > 620 MPa/90 ksi). 8-28. The yield strength of A36 steel is 36 ksi (250 MPa) at room temperature, and it gradually drops with increasing temperature (Deo et al. It was later reported [27] that slight variations in the fiber orientation would completely obscure the estimates of F12. flange, 4 in. FIGURE 8-27. Table21.5. The kinetics of sintering were considered at length inSection 6.6.3 and serve to design processing treatments. Failure ellipse for biaxial stress with = 0 and 0. Some of them (e.g. If you have noticed an error in the text or calculations, or you need another converter, which you did not find here, please let us know! 10^, that is times ten raised to the power of. (FG)= Flake graphite, (SG) = speroidal graphite. Copyright 2022 Elsevier B.V. or its licensors or contributors. TBC on N5+ failed at roughly twice the number of cycles compared with TBC on N5, showing a strong effect of the reactive element yttrium on the bond strength. However, we do not guarantee that our converters and calculators are free of errors. During welding, the high temperature at the weld region causes compressive stress because the thermal expansion in this region and restraint by the surrounding metal at lower temperature. TranslatorsCafe.com Unit Converter YouTube channel, Terms and Conditions The off-axis test has been shown to produce poor results for predicting F12 [28, 29].

We now focus on the out-of-plane bond strength at the ceramic-bond coat interface. Thus, F12 depends upon the various engineering strengths and the biaxial tensile failure stress . There is large scatter in the data. British Standards are summarised for Austenitic irons BS 3468: 1986 Table 26.66, for alloy cast irons BS 4844: 1986 in Table 26.67 and for corrosion resisting high silicon irons BS 1591: 1975 in Table 26.68. Consider the specimen in Example 5.6. Effect of F*12 on failure ellipses. Figure E5.6. Dissolution processes, followed by reprecipitation elsewhere, often result in better packing and densification. The environmental and material variables that affect the SCC behaviour of alloys are material chemistry, microstructure, cold work, stress level, concentration of corrosive species, additives to the environment, pH, temperature and electrochemical conditions, and the vast literature on SCC of low and medium strength steels are associated with the study of one or more of these variables. The general form of the Tsai-Wu failure theory is, It defines a gono-go condition on failure for a specific state of stress. All content on this website, including dictionary, thesaurus, literature, geography, and other reference data is for informational purposes only. There are many studies (Alpsten, 1970, Dawes, 1965, Nagraj, 1964) of the residual stresses in welded shapes. Beneficial changes occur in assorted properties as a function of sintering temperature as indicated schematically in Fig. 7.49).



It rarely happens that sintering is accomplished without enhancing its rate in some way. M.V. F =ferrite, F/P = ferrite/pearlite, P/F = pearlite/ferrite, P =pearlite, TS =tempered structure, TH =tempered martensite. In a significant fraction of test samples, failure occurs at the ceramicTGO interface. A COMPARISON OF THE THERMAL CONDUCTIVITIES OF FLAKE, COMPACTED AND NODULAR GRAPHITE CAST IRONS, Table 26.62. 1988-2022, Away from the weld, the residual stress is compressive in equilibrium with the tensile stress at the weld region. To eliminate porosity and strengthen them, the compacts are sintered at elevated temperatures in controlled atmospheres. For a 4 in. Soak for 2 hours for castings of simple form and thickners less than 18 mm and for 8 hours for heavy castings. Myers, in Handbook of Metal Injection Molding, 2012. The range of magnesium contents to facilitate compacted flake structures is very narrow and it is usually necessary to employ additions of titanium and cerium to extend the range and provide a practical ladle based process. Unidirectional lamina subjected to x. Table21.4. The material plastifies near the weld and compressive plastic strains are produced in this region. The left-hand side can be either. In view of this, the review covers the conventional SCC behaviour as well as hydrogen embrittlement behaviour of the steels under consideration. Select the unit to convert from in the left box containing the list of units. The limited bond strength data reported in literature involve the following systems: Alloy/bond coat: PWA 1484/NiCoCrAlY, where the alloy is a single-crystal Ni base alloy from Pratt & Whitney (Meier et al., 1992); Alloy/bond coat: N5-/Pt aluminide, N5+/Pt aluminide, where N5 is a single-crystal Ni base superalloy Ren N5 from General Electric, + indicates 100 ppm yttrium addition while means no yttrium added (Rudd et al., 2001); Alloy/bond coat: N5, IN-939, CMSX-4, Mar-M 509/Pt aluminide or NiCoCrAlY, where IN-939 is a commercial polycrystalline Ni base alloy, CMSX-4 is a single-crystal Ni base superalloy from CanonMuskegan, and Mar-M 509 is a commercial polycrystalline Co base superalloy (Gell et al., 1999) (Fig. 26.5) but they are section sensitive (Fig. Sasayama et al. What type of flux is used to weld a low hydrogen application with SAW? Verification of hardness and 0.2% proof stress is optimal. (1955) investigated the longitudinal distortion of steel caused in fillet welding of T-bars in low- carbon steel. In addition to the defects within each layer of TBC and at the interface, the bond strength of the interface between the ceramic coating and the TGO as well as between the TGO and the bond coat and their evolution with temperature and time play a key roll in controlling the durability of the TBC. The presence of certain element combinations in irons which would otherwise solidify with a conventional flake graphite form may promote the formation of the compacted type of graphite. with F*12 = -1/2 are, In A Quick Guide to API 653 Certified Storage Tank Inspector Syllabus, 2011. Uniaxial tension and compression tests to determine F1, F11 F2, and F22. Terms and Conditions. Figure 5.8. Table 26.64. Courtesy of G. F. Vander Voort, Carpenter Technologies Corporation. Sintering temperatures are obviously lower than melting temperatures, and may be hundreds to well over 1000C lower.

Schematic of test procedure proposed by Evans and Zhang [30] for determination of F12. Wu and Stachorski [33] found that for materials such as thermoplastics and paper (which are less anisotropic than graphite/epoxy) good agreement between theory and experiment is achieved for an interactive term expressed as. Thus the list of agents producing SCC in steels gets longer. In a SMAW electrode classified as E7018 what does the 70 refer to? https://acronyms.thefreedictionary.com/KSI, The device sends the device certificate information E(I[V.sub.k],(I[D.sub.Dev], M)),h([Z.sub.i], M), [C.sub.i] to, EPA registered antimicrobial) Cu Pb Zn Fe Mn Si Min (%) 94.0 0.8 3.5 Max (%) 0.09 0.25 0.20 1.5 4.5 Copper + sum of named elements 99.5% min Ni value included Co Sand Cast Tensile Strength: 45. Renowned for his energetic attitude in front of the camera, He said: "An educational strategy was developed back in 2006 and focused on the Limavady area as over 50% of collisions were someone was killed or seriously (, Typical properties of KVA's MSS pipe: Hardened: yield strength: 160, Posteriormente, foi realizada a analise de variancia (ANOVA) e regressao linear para verificar o efeito das doses crescentes de silicato de potassio (, Dictionary, Encyclopedia and Thesaurus - The Free Dictionary, the webmaster's page for free fun content, A Study on KSI-based Authentication Management and Communication for Secure Smart Home Environments, Several no-lead copper alloy options for water components: metalcasters have a variety of no-lead copper alloys to choose from to make cast components for potable water systems, and each alloy requires specific practices when converting from leaded alloys, Changes in morphological indexes of young atlantic salmon (Salmo Salar L.) exposed to heavy metal (Zn, Cu, Ni, Cr, Pb, Cd) mixture: an experimental study/Atlantiniu lasisu (Salmo Salar L.) jaunikliu morfologiniu rodikliu pokyciai veikiant sunkiuju metalu (Zn, Cu, Ni, Cr, Pb, Cd) misiniu: eksperimentinis tyrimas, IOANNOU & THEODOULOU LTD's international reach expands significantly, New YouTube sports channel features 'KSI', Kinetic Systems, Inc. Acquired by Kinetics Holding GmbH, MAKIN' TRACKS TO ROAD SKILLS; He'll keep you up to speed with Norn Iron's car scene, Potassium silicate, acibenzolar-S-methyl and fungicides on the control of soybean rust/Silicato de potassio, acibenzolar-S-metil e fungicidas no controle da ferrugem da soja. FIGURE 8-28. (a) Bond strength of TBC deposited by EB-PVD on Pt aluminide bond coat as a function of thermal cycling to 1121C (2050F). A515 Gr 50 has S = 15.8 ksi at 600 F. For example, in the production of tungsten carbide, a very widely used cutting tool material for machining, liquid cobalt, produced at the sintering temperature, binds the WC particles together (Fig. ScienceDirect is a registered trademark of Elsevier B.V. ScienceDirect is a registered trademark of Elsevier B.V. Current Trends and Future Developments on (Bio-) Membranes, A Quick Guide to API 653 Certified Storage Tank Inspector Syllabus, MATERIALS PROCESSING AND FORMING OPERATIONS, Powders are pressed in shaped, multipiece die sets at high pressures, for example, 0.4 to 0.8 GPa (60120. Collecting terms and rearranging, (F11+2F12+F22)2+(F1+F2)=1. Consider a unidirectional lamina with failure strengths X = X' = 217.7 ksi, Y = 5.8 ksi, Y' = 35.7 ksi, and S = 9.86 ksi. Clifford Matthews, in A Quick Guide to API 570 Certified Pipework Inspector Syllabus, 2009. Figure 5.6. This term is not the only one applicable to slightly anisotropic materials such as paper. Method: API 570 section 7.2. A simple conceptual model for failure (Bose and DeMasi-Marcin, 1997) (Fig. Again at the upper edge of the web, the stresses are tensile. PSP, HIPAA The only nonzero applied stress is assumed to be x = 5 ksi. Taip pat buvo atlikta kontroliniu ir bandymo zuvu morfologiniu rodikliu (IK, VSI, ZSI, The improved skills and experience which are now available to them will help them further service their clients' international needs -- a truly effective alternative to the big four and other international groups." Fully compacted graphite irons have combinations of properties intermediate between those of conventional flake and nodular irons, as shown in Table 26.64. The types of surface formed, as well as the discriminants, are. In Smithells Metals Reference Book (Eighth Edition), 2004. In general compacted graphite irons have mechanical and physical properties intermediate between those of conventional flake graphite irons (grey irons) and nodular graphite irons. E-notation is commonly used in calculators and by scientists, mathematicians and engineers. What shielding gases can be used in GTAW?

Acronym Finder, All Rights Reserved. These alloys are capable of 19g/cm3 density, 35% elongation, 43 HRC hardness, and 1380MPa (200 ksi) ultimate tensile strength. The strength ratio can be used to define the allowable stress or strain (R = 1), and a factor of safety. The parameters selected to define F12 do not have to be those defined by Tsai and Hahn [31]. Table21.5 shows a study performed on a 95wt%W alloy which received vacuum treatment. Assuming all other stress components are zero, the failure criterion reduces to, Solving these equations simultaneously results in. 6.2. A general second-degree expression of this type can define a quadratic surface.

says Liza Robbins, CEO of Morison, The company has received top honours in the 'End Use' category for: 'Electric Vehicle': Energy Efficiency Automation System -, The report, presented at the PCC public scrutiny meeting at Harris Academy, revealed a total of 805. Since S = S', these terms are, In a similar manner, evaluation of the remaining first-order terms (F1616 and F2626) yields F16 = F26 = 0. Figure6.2 shows the distribution of the residual stress in the web of the stiffener. By continuing you agree to the use of cookies. The environments in which cathodic SCC or hydrogen embrittlement are encountered are hydrogen sulphide, hydrogen gas, hydrogen fluoride and hydrogen cyanide. and is found in the following Acronym Finder categories: The Acronym Finder is Which process does not use bare wire electrodes? Failure strengths and strength coefficients (F11, etc.) Effect of carbon equivalent on the tensile strengths of flake, compacted and nodular graphite irons cast into 30 mm-diameter bars, Figure 26.6. long stiffener, the bowing distortion was 5.7 during the experiments carried out on ASTM AH36 steel using double fillet gas metal arc welding (GMAW) and was predicted to be 142.25 for a 20 feet long stiffener (Deo and Michaleris, 2002). For example, consider a load in the 1-1 1 stressstrain plane as illustrated in Figure 5.7. The yield stress is low owing to local high temperatures during welding. The procedure for transformation into the strain space is identical to that described for the TsaiHill theory in the previous section. Schematic variation of P/M compact properties as a function of sintering temperature. In one of the most common processes, liquid phase sintering, a liquid provides for enhanced material transport and more rapid sintering. Microstructure of WC sintered with cobalt which surrounds the carbide particles. We work hard to ensure that the results presented by TranslatorsCafe.com converters and calculators are correct. The 6 term is the shear stress 12, as shown in Figure 5.6. A COMPARISON OF THE MECHANICAL PROPERTIES OF FLAKE, COMPACTED AND NODULAR GRAPHITE CAST IRONS IN 30 MM BAR SECTIONS, Figure 26.5.

Which of the following does not produce a layer of slag on the weld metal? Select the unit to convert to in the right box containing the list of units. Which type of SMAW electrode would be used for low hydrogen applications?