Abstract: A probability in which a stress amplitude ?p of an operating stress exceeds a stress amplitude ?w of a fatigue strength (a fatigue strength excess probability pV0 of a virtual cell) at each virtual cell in which a region of a machine component is equally divided so that one inclusion is contained therein and having a virtual unit volume V0 is derived on an assumption that a distribution function of an inclusion size ?{square root over ( )}area follows a generalized Pareto distribution. Then a probability in which the stress amplitude ?p of the operating stress exceeds the stress amplitude ?w of the fatigue strength (a fatigue strength excess probability pfV of the machine component) in at least one virtual cell is derived from the fatigue strength excess probability pV0.

Abstract: A probability in which a stress amplitude ?p of an operating stress exceeds a stress amplitude ?w of a fatigue strength (a fatigue strength excess probability pV0 of a virtual cell) at each virtual cell in which a region of a machine component is equally divided so that one inclusion is contained therein and having a virtual unit volume V0 is derived on an assumption that a distribution function of an inclusion size ?{square root over ( )}area follows a generalized Pareto distribution. Then a probability in which the stress amplitude ?p of the operating stress exceeds the stress amplitude ?w of the fatigue strength (a fatigue strength excess probability pfV of the machine component) in at least one virtual cell is derived from the fatigue strength excess probability pV0.

Abstract: An impact treatment method for improving fatigue characteristics of a welded joint comprising pressing an impact pin against the surface of a base metal material near a toe of a weld bead and making it move relatively to the weld line direction to apply hammer peening treatment or ultrasonic impact treatment, characterized by using as the impact pin an impact pin having a tip curvature radius of ½ or less of a thickness of the metal material and between 2 to 10 mm and, on a surface of a base metal material up to a range where a distance from the toe of the weld bead to the center of the impact treatment position is within 2.5 times the tip curvature radius of the impact pin and where the impact pin does not contact the weld metal during impact treatment, applying hammer peening or ultrasonic impact treatment so as to cause by the impact pin residual plastic deformation where an impact dent has a groove depth of 0.

Abstract: There is derived an index FS (P) obtained by integrating the product of a probability distribution function f (?{square root over ( )}areamax) of an inclusion size ?{square root over ( )}areamax of a part and a “size S (P, ?{square root over ( )}?{square root over ( )}areamax) of a region of the part” where a stress amplitude ? of an acting stress exceeds a stress amplitude ?w of a fatigue strength at each location in the case of a load being applied under a loading condition P set previously by an operator over the inclusion size ?{square root over ( )}?{square root over ( )}areamax of the part with the whole region of a range where a probability distribution of the inclusion size ?{square root over ( )}areamax exists set as an integral range.

Abstract: An effective volume Vep of a member is calculated with a stress correction amount ?corr added to an effective stress (stress amplitude) ?ip at each position of the member so that a fatigue strength of the member varying corresponding to an average stress varying depending on the position of the member is apparently constant at a value when the average stress on the member is 0 (zero) irrespective of the position of the member, and a cumulative fracture probability Pfp due to fatigue of the member is derived using the effective volume Vep of the member.

Abstract: An impact treatment method for improving fatigue characteristics of a welded joint comprising pressing an impact pin against the surface of a base metal material near a toe of a weld bead and making it move relatively to the weld line direction to apply hammer peening treatment or ultrasonic impact treatment, characterized by using as the impact pin an impact pin having a tip curvature radius of ½ or less of a thickness of the metal material and between 2 to 10 mm and, on a surface of a base metal material up to a range where a distance from the toe of the weld bead to the center of the impact treatment position is within 2.5 times the tip curvature radius of the impact pin and where the impact pin does not contact the weld metal during impact treatment, applying hammer peening or ultrasonic impact treatment so as to cause by the impact pin residual plastic deformation where an impact dent has a groove depth of 0.

Abstract: A large-heat-input butt-welded joint of welded structures prepared by butt-welding high-strength steel plates over 50 mm in thickness, having excellent brittle fracture resistance, is characterized by: (a1) the hardness of the weld metal is not more than 110% of the hardness of the base metal or (a2) the hardness of the weld metal is not less than 70% and not more than 110% of the hardness of the base metal, and, as required, (b) the width of the weld metal is not more than 70% of the plate thickness of the base metal, (c) the width of the region affected by welding whose hardness is softened to not more than 95% of the hardness of the non-heat-affected base metal has a width not less than 5 mm, and/or (d) the prior austenite grain size in the heat-affected zone (HAZ) contacting the welding fusion line is not more than 200 ?m.

Abstract: A welding method for manufacturing welded structures having excellent properties to prevent the propagation of brittle fracture occurring in welded joints, characterized by the step of forming a repair weld having a greater toughness than that of a butt weld and an outer edge whose angle ? with respect to the longitudinal direction of the butt weld is not less than 10 degrees and not more than 60 degrees, by applying repair welding to a region to arrest a brittle crack in a butt-welded joint where a brittle crack is likely to propagate after removing part of the butt-welded joint, in said region, by gouging or machining.

Abstract: A fuel cell stack 1 in a fuel-circulating fuel cell system is supplied with fuel and an oxidizing agent to generate electricity. The fuel discharged from the fuel cell stack 1 is supplied to the fuel cell stack 1 again through a fuel-circulating passage 6. In the fuel-circulating passage 6 is provided a fuel pump 3 powered from an outside source to circulate the fuel through the fuel-circulating passage 6 at a predetermined circulation rate. An ECU 4 transmits an output instruction value to the fuel cell stack 1 and regulates a circulation rate of the fuel in the fuel-circulating passage 6 according to the output instruction value.

Abstract: A fuel cell system includes a fuel cell for generating power by being supplied with a fuel gas and an oxidizing gas, a fuel gas supply path for supplying a fuel gas to the fuel cell, a fuel off-gas circulation path for returning a fuel off-gas discharged from the fuel cell to the fuel gas supply path, an ejector, provided in the fuel gas supply path and driven by fluid flow energy, for supplying the fuel off-gas in the fuel off-gas circulation path flow to the fuel gas supply path, a fuel pump, provided in the fuel off-gas circulation path or on the fuel gas supply path and downstream with respect to the ejector, and driven by a rotating machine, for pressurizing the fuel off-gas, a discharge valve for discharging the fuel off-gas from the fuel off-gas circulation path; and a control device operatively connected to the fuel pump and to the discharge valve.

Abstract: A method for warming up a fuel cell system comprising; a fuel cell which generates electric current due to an electrochemical reaction between hydrogen and oxygen, and which supplies the electric current to a load, an air supply pipe for supplying air to the fuel cell as an oxidant gas, an air exhaust pipe for discharging exhaust air from the fuel cell to an atmosphere, a compressor provided on either of air supply pipe and air exhaust pipe, which carries the air and a communication pipe which returns exhaust air to air supply pipe, and which communicates exhaust air pipe with air supply pipe to form a circulation cycle including compressor.

Abstract: A large-heat-input butt-welded joint of welded structures prepared by butt-welding high-strength steel plates over 50 mm in thickness, having excellent brittle fracture resistance, is characterized by: (a1) the hardness of the weld metal is not more than 110% of the hardness of the base metal or (a2) the hardness of the weld metal is not less than 70% and not more than 110% of the hardness of the base metal, and, as required, (b) the width of the weld metal is not more than 70% of the plate thickness of the base metal, (c) the width of the region affected by welding whose hardness is softened to not more than 95% of the hardness of the non-heat-affected base metal has a width not less than 5 mm, and/or (d) the prior austenite grain size in the heat-affected zone (HAZ) contacting the welding fusion line is not more than 200 ?m.

Abstract: A welding method for manufacturing welded structures having excellent properties to prevent the propagation of brittle fracture occurring in welded joints, characterized by the step of forming a repair weld having a greater toughness than that of a butt weld and an outer edge whose angle ? with respect to the longitudinal direction of the butt weld is not less than 10 degrees and not more than 60 degrees, by applying repair welding to a region to arrest a brittle crack in a butt-welded joint where a brittle crack is likely to propagate after removing part of the butt-welded joint, in said region, by gouging or machining.

Abstract: A welding method for manufacturing welded structures having excellent properties to prevent the propagation of brittle fracture occurring in welded joints, characterized by the step of forming a repair weld having a greater toughness than that of a butt weld and an outer edge whose angle ? with respect to the longitudinal direction of the butt weld is not less than 10 degrees and not more than 60 degrees, by applying repair welding to a region to arrest a brittle crack in a butt-welded joint where a brittle crack is likely to propagate after removing part of the butt-welded joint, in said region, by gouging or machining.

Abstract: The invention provides a fuel cell system, which has a humidifying apparatus to supply the sufficient moisture to the solid electrolyte membrane of a fuel cell and is capable of preventing the mixture of fuel and oxidant gases in the apparatus. The hydrogen gas supplied to the anode of the fuel cell is humidified in the first humidifier and the air Ad supplied to the cathode is humidified in the second humidifier. The first humidifier has the non-porous water permeable membrane, which is permeable only to the moisture of the cathode off-gas discharged from the cathode of the fuel cell, on the other hand the second humidifier has the porous water permeable membrane, which is permeable to the moisture of the cathode off-gas.

Abstract: A method for warming up a fuel cell system comprising; a fuel cell which generates electric current due to an electrochemical reaction between hydrogen and oxygen, and which supplies the electric current to a load, an air supply pipe for supplying air to the fuel cell as an oxidant gas, an air exhaust pipe for discharging exhaust air from the fuel cell to an atmosphere, a compressor provided on either of air supply pipe and air exhaust pipe, which carries the air and a communication pipe which returns exhaust air to air supply pipe, and which communicates exhaust air pipe with air supply pipe to form a circulation cycle including compressor.

Abstract: A humidifier for fuel cell of the present invention comprises a hollow fiber membrane module in which a hollow fiber membrane bundle, comprising hollow fiber membranes bundled together, is accommodated inside a housing. The module comprises an entrance head which supplies off-gas inside the hollow fiber membranes, an exit head which converges off-gas, which has passed through the hollow fiber membranes, at another end of the hollow fiber membrane module, and an exhaust exit which exhausts liquid, accumulated in the entrance head. According to this humidifier, it is possible to prevent the hollow fiber membranes from becoming blocked by water.

Abstract: A humidifying system for a fuel cell includes: a fuel cell having an anode and a cathode, the anode being supplied with a fuel gas and the cathode being supplied with an oxidant gas so that the fuel gas and the oxidant gas chemically react within the fuel cell to generate electricity; a first humidifier transferring moisture of cathode exhaust gas discharged from the cathode of the fuel cell to the fuel gas through hollow fiber membranes; a second humidifier transferring moisture of cathode exhaust gas discharged from the first humidifier to the oxidant gas through hollow fiber membranes; and a reduced pressure generating device arranged downstream of the first humidifier and between the first humidifier and the fuel cell to mix part of anode exhaust gas discharged from the anode of the fuel cell with the fuel gas using negative pressure resulting from a flow of the fuel gas.

Abstract: An apparatus for warming-up a fuel cell has means for returning an exhaust gas which returns the exhaust gas to the supply gas depending upon the warning-up conditions of the fuel cell at the time when the supply gas is supplied into the fuel cell and it is discharged as the exhaust gas after utilizing the supply gas in the fuel cell.

Abstract: A fuel cell includes an anode and a cathode, and a fuel gas supplied to the anode and an oxidant gas supplied to the cathode chemically react with each other to generate electricity. Moisture contained in a cathode exhaust gas discharged from the cathode is transferred to the fuel gas in a first humidifier and then to the oxidant gas in a second humidifier. The cathode exhaust gas flows through a cathode exhaust gas passage from the cathode via the first humidifier to the second humidifier. A bypass is provided to the cathode exhaust gas passage to allow part of the cathode exhaust gas to detour round the first humidifier and flow to the second humidifier. Accordingly, the balance between humidification levels of fuel gas and oxidant gas each supplied to the fuel cell may be kept and adjusted properly even when the output of the fuel cell gets higher.