The fatigue contrast tests of unload longitudinal direction comer joints asoriginal welded and treated by ultrasonic peening of Q235B in various stress ratio are directed. Theimprovements of fatigue performance of unl...The fatigue contrast tests of unload longitudinal direction comer joints asoriginal welded and treated by ultrasonic peening of Q235B in various stress ratio are directed. Theimprovements of fatigue performance of unload longitudinal direction corner joints resulted byultrasonic peening are studied. The effect pattern of stress ratio on fatigue performance of weldedjoints that are treated by ultrasonic peening is studied. As tests results indicate that: ① In thecondition of stress ratio .R=-l, the fatigue strength 'of specimen treated by ultrasonic peening isincreased by 165 percent of that of the original welded specimen. And the fatigue life of specimentreated by ultrasonic peening is as much as 75 approx 210 times of that of the latter. When R=0.1,the fatigue strength is increased by 87 percent and the fatigue life is extended by 21 approx 29times. When R=-0.5, the fatigue strength is increased by 123 percent and the fatigue life isextended by 42 approx 59 times. When R=0.45, the fatigue strength is increased by 51 percent and thefatigue life is extended by 3 approx 14 times. ② If the welded joints are treated by ultrasonicpeening, the fatigue strength is no longer independent on the applied mean stress. The more thestress ratio R, the less the fatigue stress range which can be sustained by the joints is. ③Whether the high value residual stress is in the joints or not, the dead load portion of the appliedload must be considered in the design of the joints which should be treated by ultrasonic peening.展开更多
People have many beliefs about the accuracy of language.But in fact, language is more often than not deceptive. In human language, many words with apparently precise meaning or definition often express uncertain conce...People have many beliefs about the accuracy of language.But in fact, language is more often than not deceptive. In human language, many words with apparently precise meaning or definition often express uncertain concept which suggests an inherent linguistic characteristic of language -- fuzziness.展开更多
The distributions of temperature and residual stresses in thin plates of BT20titanium alloy are numerically analyzed by three-dimensional finite element software duringelectron beam welding and electron beam local pos...The distributions of temperature and residual stresses in thin plates of BT20titanium alloy are numerically analyzed by three-dimensional finite element software duringelectron beam welding and electron beam local post-weld heat treatment (EBLPWHT). Combined withnumerical calculating results, the effects of different EBLPWHT mode and parameters, including heattreating position, heating width and heating time, on the distribution of welding residual stressesare analyzed. The results show that, the residual tensile stresses in weld center can be largelydecreased when the weld is heat treated at back preface of the plate. The numerical results alsoindicated that the magnitude of the residual longitudinal stresses of the weld and the zone vicinityof the weld is decreased, and the range of the residual longitudinal stresses is increased alongwith the increase of heating width and heating time.展开更多
The potential applications of some high tenologies in refractories,such as,nanotechnology,in-situ synthesis,self-propagating high-temperature synthesis,functional gradient materials,computer assisted design and some n...The potential applications of some high tenologies in refractories,such as,nanotechnology,in-situ synthesis,self-propagating high-temperature synthesis,functional gradient materials,computer assisted design and some new advanced refactories in Si-Al-O-N system are briefly described.The characteristics and preparation processes of these new refractories areintroduced,and the remaining problems awaiting effective solutions are pointed out .Some suggesions on future diection of research and development are fitly made.展开更多
Based on the tests of a build-up welding at plate edge (BWPE) and amulti-layer build-up welding on plate (MBWP), the article studies on the solid-state phasetransformations which affect welding distortion process and ...Based on the tests of a build-up welding at plate edge (BWPE) and amulti-layer build-up welding on plate (MBWP), the article studies on the solid-state phasetransformations which affect welding distortion process and on the influence rule of transformationstarting temperature (TST) of welded metal to the welding residual distortion. The weldingdistortion can be decreased or controlled by the transformation volume expansion caused bysolid-state phase transformation of welded metal during the cooling. The test results of BWPE showthat when TST is at about 190 deg C, the bending distortion of welded specimen is the smallest, andits displacements at free end are decreased to 58 percent and 67 percent compared with those ofconventional welding electrodes A102 and E5015, which TST are less than room temperature and equalto 758 deg C respectively. The test results of MBWP show that when TST were at 100 approx 250 deg C.the welded specimen would appear reversible bending distortion compared with those of A102 andE5015. The maximum deflection value of reversible bending distortion in 8 mm thick plate is -2.94 mmat about 170 deg C of TST. The test results provide a valuable method to decrease or to controlwelding residual distortion.展开更多
To investigate the effect of dynamic loading on fracture behavior of weldedjoints of structural steel Q235B and 16Mn in common use and compare the earthquake resistances ofthe two kinds of materials, dynamic tension a...To investigate the effect of dynamic loading on fracture behavior of weldedjoints of structural steel Q235B and 16Mn in common use and compare the earthquake resistances ofthe two kinds of materials, dynamic tension and fracture toughness tests are carried out at roomtemperature. On the basis of the tests, the stress-strain fields near the crack tip of the compactspecimens are analyzed by three-dimensional finite element model. The test results and finiteelement analysis results show that, the fracture toughness of welds and base metal of 16Mn steelincreases with the increment of loading rate. Compared with 16Mn steel, Q235B steel is moresensitive to dynamic loading. The fracture toughness of welds of Q235B is comparatively low understatic loading and dynamic loading at room temperature. Compared with the static loading, thefracture toughness of Q235B parent metal under dynamic loading decreases by about four times.Therefore, it can be concluded that compared with 16Mn steel, the earthquake resistances of weld andparent metal of Q235B are rather poor.展开更多
文摘The fatigue contrast tests of unload longitudinal direction comer joints asoriginal welded and treated by ultrasonic peening of Q235B in various stress ratio are directed. Theimprovements of fatigue performance of unload longitudinal direction corner joints resulted byultrasonic peening are studied. The effect pattern of stress ratio on fatigue performance of weldedjoints that are treated by ultrasonic peening is studied. As tests results indicate that: ① In thecondition of stress ratio .R=-l, the fatigue strength 'of specimen treated by ultrasonic peening isincreased by 165 percent of that of the original welded specimen. And the fatigue life of specimentreated by ultrasonic peening is as much as 75 approx 210 times of that of the latter. When R=0.1,the fatigue strength is increased by 87 percent and the fatigue life is extended by 21 approx 29times. When R=-0.5, the fatigue strength is increased by 123 percent and the fatigue life isextended by 42 approx 59 times. When R=0.45, the fatigue strength is increased by 51 percent and thefatigue life is extended by 3 approx 14 times. ② If the welded joints are treated by ultrasonicpeening, the fatigue strength is no longer independent on the applied mean stress. The more thestress ratio R, the less the fatigue stress range which can be sustained by the joints is. ③Whether the high value residual stress is in the joints or not, the dead load portion of the appliedload must be considered in the design of the joints which should be treated by ultrasonic peening.
文摘People have many beliefs about the accuracy of language.But in fact, language is more often than not deceptive. In human language, many words with apparently precise meaning or definition often express uncertain concept which suggests an inherent linguistic characteristic of language -- fuzziness.
基金This project is supported by Foundation of National Defense Technology Key Laboratory, China (No.99JS50.3.2JW1402).
文摘The distributions of temperature and residual stresses in thin plates of BT20titanium alloy are numerically analyzed by three-dimensional finite element software duringelectron beam welding and electron beam local post-weld heat treatment (EBLPWHT). Combined withnumerical calculating results, the effects of different EBLPWHT mode and parameters, including heattreating position, heating width and heating time, on the distribution of welding residual stressesare analyzed. The results show that, the residual tensile stresses in weld center can be largelydecreased when the weld is heat treated at back preface of the plate. The numerical results alsoindicated that the magnitude of the residual longitudinal stresses of the weld and the zone vicinityof the weld is decreased, and the range of the residual longitudinal stresses is increased alongwith the increase of heating width and heating time.
文摘The potential applications of some high tenologies in refractories,such as,nanotechnology,in-situ synthesis,self-propagating high-temperature synthesis,functional gradient materials,computer assisted design and some new advanced refactories in Si-Al-O-N system are briefly described.The characteristics and preparation processes of these new refractories areintroduced,and the remaining problems awaiting effective solutions are pointed out .Some suggesions on future diection of research and development are fitly made.
基金This project is supported by National Natural Science Foundation of China (No.50175079) China Postdoctoral Science Foundation (No.2003033348).
文摘Based on the tests of a build-up welding at plate edge (BWPE) and amulti-layer build-up welding on plate (MBWP), the article studies on the solid-state phasetransformations which affect welding distortion process and on the influence rule of transformationstarting temperature (TST) of welded metal to the welding residual distortion. The weldingdistortion can be decreased or controlled by the transformation volume expansion caused bysolid-state phase transformation of welded metal during the cooling. The test results of BWPE showthat when TST is at about 190 deg C, the bending distortion of welded specimen is the smallest, andits displacements at free end are decreased to 58 percent and 67 percent compared with those ofconventional welding electrodes A102 and E5015, which TST are less than room temperature and equalto 758 deg C respectively. The test results of MBWP show that when TST were at 100 approx 250 deg C.the welded specimen would appear reversible bending distortion compared with those of A102 andE5015. The maximum deflection value of reversible bending distortion in 8 mm thick plate is -2.94 mmat about 170 deg C of TST. The test results provide a valuable method to decrease or to controlwelding residual distortion.
基金This project is supported by National Natural Science Foundation of China (No.59975066).
文摘To investigate the effect of dynamic loading on fracture behavior of weldedjoints of structural steel Q235B and 16Mn in common use and compare the earthquake resistances ofthe two kinds of materials, dynamic tension and fracture toughness tests are carried out at roomtemperature. On the basis of the tests, the stress-strain fields near the crack tip of the compactspecimens are analyzed by three-dimensional finite element model. The test results and finiteelement analysis results show that, the fracture toughness of welds and base metal of 16Mn steelincreases with the increment of loading rate. Compared with 16Mn steel, Q235B steel is moresensitive to dynamic loading. The fracture toughness of welds of Q235B is comparatively low understatic loading and dynamic loading at room temperature. Compared with the static loading, thefracture toughness of Q235B parent metal under dynamic loading decreases by about four times.Therefore, it can be concluded that compared with 16Mn steel, the earthquake resistances of weld andparent metal of Q235B are rather poor.
