BACKGROUND Groove pancreatitis(GP)is a rare condition affecting the pancreatic groove region within the dorsal-cranial part of the pancreatic head,duodenum,and common bile duct.As a rare form of chronic pancreatitis,G...BACKGROUND Groove pancreatitis(GP)is a rare condition affecting the pancreatic groove region within the dorsal-cranial part of the pancreatic head,duodenum,and common bile duct.As a rare form of chronic pancreatitis,GP poses a diagnostic and therapeutic challenge for clinicians.GP is frequently misdiagnosed or not considered;thus,the diagnosis is often delayed by weeks or months.The treatment of GP is complicated and often requires surgical intervention,especially pancreatoduodenectomy.CASE SUMMARY A 66-year-old man with a history of long-term drinking was admitted to the gastroenterology department of our hospital,complaining of vomiting and acid reflux.Upper gastrointestinal endoscopy showed luminal stenosis in the descending part of the duodenum.Abdominal computed tomography showed slight exudation in the descending and horizontal parts of the duodenum with broadening of the groove region,indicating local pancreatitis.The symptoms of intestinal obstruction were not relieved with conservative therapy,and insertion of an enteral feeding tube was not successful.Exploratory laparoscopy was performed and revealed a hard mass with scarring in the horizontal part of the duodenum and stenosis.Intraoperative frozen section analysis showed no evidence of malignancy,and side-to-side duodenojejunostomy was performed.Routine pathologic examination showed massive proliferation of fibrous tissue,hyaline change,and the proliferation of spindle cells.Based on the radiologic and pathologic characteristics,a diagnosis of GP was made.The patient presented with anastomotic obstruction postoperatively and took a long time to recover,requiring supportive therapy.CONCLUSION GP often involves the descending and horizontal parts of the duodenum and causes duodenal stenosis,impaired duodenal motility,and gastric emptying due to fibrosis.展开更多
The aim of this work is to develop a three-dimensional model of deep groove ball bearing to investigate the loaded stresses and central displacements of bearing rings. The equivalent stresses and central displacements...The aim of this work is to develop a three-dimensional model of deep groove ball bearing to investigate the loaded stresses and central displacements of bearing rings. The equivalent stresses and central displacements of bearing rings are obtained based on the simulated analysis. Moreover, several parameters, such as load magnitude, raceway groove curvature radius(RGCR), thicknesses of outer and inner rings, are varied to investigate their effects on the equivalent stresses and central displacements of bearing rings. Research results provide useful guidelines for determining the design parameters.展开更多
In order to improve the efficiency of film cooling, numerical investigation was carried out to study the effects of different film-cooled plates on surface heat transfer. Both grooved and non-grooved surfaces were con...In order to improve the efficiency of film cooling, numerical investigation was carried out to study the effects of different film-cooled plates on surface heat transfer. Both grooved and non-grooved surfaces were concerned. The modeling was per- formed using Fluent software with the adoption of Shear-Stress Transport (SST) k-ωmodel as the turbulence closure. The coolant was supplied by a single film cooling hole with an inclination angle of 30°. The Mach numbers for the coolant flow and the mainstream flow were fixed at 0 and 0.6, respectively. At three blowing ratios of 0.5, 1.0 and 1.5, the aerodynamic behaviour of the mixing process as well as the heat transfer performance of the film cooling were presented. The numerical results were validated using experimental data extracted from a benchmark test. Good agreements between numerical results and the ex- perimental data were observed. For the film cooling efficiency, it shows that both local and laterally averaged cooling effectiveness can be improved by the non-smooth surface at different blowing ratios. Using the grooved surface, the turbulence intensity upon the plate can be reduced notably, and the mixing between the two flows is weakened due to the reduced turbu lence level. The results indicate that the cooling effectiveness of film cooling can be enhanced by applying the grooved surface.展开更多
Spiral groove dry gas seal(S?DGS), the most widely used DGS in the world, encounters the problem of high leakage rate and inferior film stability when used in high?speed machinery equipment, which could not be well so...Spiral groove dry gas seal(S?DGS), the most widely used DGS in the world, encounters the problem of high leakage rate and inferior film stability when used in high?speed machinery equipment, which could not be well solved by optimization of geometrical parameters and molded line of spiral groove. A new type of bionic cluster spiral groove DGS(CS?DGS) is proved to have superior film stability than S?DGS at the condition of high?speed and low?pressure numerically. A bionic CS?DGS is experimentally investigated and compared with common S?DGS in order to provide evidence for theoretical study. The film thickness and leakage rate of both bionic spiral groove and common spiral groove DGS are measured and compared with each other and with theoretical values under different closing force at the condition of static pressure, high?speed and low?pressure, and the film stiffness and stiffness?leakage ratio of these two face seals are derived by the relationship between closing force and film thickness at the steady state. Experimental results agree well with the theory that the leakage and stiffness of bionic CS?DGS are superior to that of common S?DGS under the condition of high?speed and low?pressure, with the decreasing amplitude of 20% to 40% and the growth amplitude of 20%, respectively. The opening performance and stiffness characteristics of bionic CS?DGS are inferior to that of common S?DGS when rotation speed equals to 0 r/min. The proposed research provides a new method to measure the axis film stiffness of DGS, and validates the superior performance of bionic CS?DGS at the condition of high?speed and low?pressure experimentally.展开更多
Dynamic failure and ejection characteristics of a periodic grooved Sn surface under unsupported shock loading are studied using a smoothed particle hydrodynamics method. An "Eiffel Tower" spatial structure is observ...Dynamic failure and ejection characteristics of a periodic grooved Sn surface under unsupported shock loading are studied using a smoothed particle hydrodynamics method. An "Eiffel Tower" spatial structure is observed, which is com- posed of high-speed jet tip, high-density jet slug, longitudinal tensile sparse zone, and complex broken zone between grooves. It is very different from the spike-bubble structure under supported shocks, and has been validated by detonation loading experiments. In comparison with that under supported shocks at the same peak pressure, the high-speed ejecta decreases obviously, whereas the truncated location of ejecta moves towards the interior of the sample and the total mass of ejecta increases due to the vast existence of low-speed broken materials. The shock wave profile determines mainly the total ejection amount, while the variation of V-groove angle will significantly alter the distribution of middle- and high-speed ejecta, and the maximum ejecta velocity has a linear corretation with the groove angle.展开更多
The current research on secondary O-ring seals used in mechanical seals has begun to focus on their dynamic properties. However, detailed analysis of the dynamic properties of O-ring seals in spiral groove gas face se...The current research on secondary O-ring seals used in mechanical seals has begun to focus on their dynamic properties. However, detailed analysis of the dynamic properties of O-ring seals in spiral groove gas face seals is lacking. In particular a transient study and a difference analysis of steady-state and transient performance are imperative. In this paper, a case study is performed to gauge the effect of secondary O-ring seals on the dynamic behavior(steady-state performance and transient performance) of face seals. A numerical finite element method(FEM) model is developed for the dynamic analysis of spiral groove gas face seals with a flexibly mounted stator in the axial and angular modes. The rotor tilt angle, static stator tilt angle and O-ring damping are selected to investigate the effect of O-ring seals on face seals during stable running operation. The results show that the angular factor can be ignored to save time in the simulation under small damping or undamped conditions. However, large O-ring damping has an enormous effect on the angular phase difference of mated rings, affecting the steady-state performance of face seals and largely increasing the possibility of face contact that reduces the service life of face seals. A pressure drop fluctuation is carried out to analyze the effect of O-ring seals on the transient performance of face seals. The results show that face seals could remain stable without support stiffness and O-ring damping during normal stable operation but may enter a large-leakage state when confronting instantaneous fluctuations. The oscillation-amplitude shortening effect of O-ring damping on the axial mode is much greater than that on the angular modes and O-ring damping prefers to cater for axial motion at the cost of angular motion. This research proposes a detailed dynamic-property study of O-ring seals in spiral groove gas face seals, to assist in the design of face seals.展开更多
BACKGROUND Groove pancreatitis(GP)is a type of chronic pancreatitis occurring in an anatomic area between the duodenum,head of the pancreas,and common bile duct.Duodenal obstruction is always caused by malignant pancr...BACKGROUND Groove pancreatitis(GP)is a type of chronic pancreatitis occurring in an anatomic area between the duodenum,head of the pancreas,and common bile duct.Duodenal obstruction is always caused by malignant pancreatic diseases,such as pancreatic head carcinoma,while is rarely induced by benign pancreatic diseases,such as pancreatitis.CASE SUMMARY A 39-year-old man presented with a 1-mo history of upper abdominal discomfort.His concomitant symptoms were abdominal distension,postprandial nausea,and vomiting.Contrast-enhanced computed tomography of the abdomen showed thickening of the intestinal wall with enhancement of the descending segment of the duodenum,which could not be clearly differentiated from the head of the pancreas.Upper gastrointestinal radiographs and gastrointestinal endoscopy showed a complete obstruction of the descending duodenum.An operation found that a 3-cm mass was located in the“groove part”of the pancreas and oppressing the descending duodenum.Pancreaticoduodenectomy was performed to relieve the obstruction and thoroughly remove the pancreatic lesions.The pathologic diagnosis was pancreatitis.The patient had an uneventful recovery with no complications.CONCLUSION Because of the special location and the contracture induced by long-term chronic inflammation,our case reminds surgeons that some benign pancreatic diseases,such as GP,can also present with symptoms similar to those of pancreatic cancer.This knowledge can help to avoid an unnecessary radical operation.展开更多
The relationship between pressure distribution and cavitation (noise) inside throttling groove is investigated by numerical simulation and experimental method. A valve pocket with several transducers is performed to...The relationship between pressure distribution and cavitation (noise) inside throttling groove is investigated by numerical simulation and experimental method. A valve pocket with several transducers is performed to detect the pressure distributions inside the valve chamber, and the results fit quite well with the computational fluid dynamics(CFD) analysis. High-speed imaging techniques are employed to investigate the cavitation mechanisms, in particular bubble inception and cluster formation near the throttling groove. A spectrum analyzer is used to measure the sound pressure level of noise generated by the bubble flow. It is found that the pressure distributions inside the groove are sensitive to the valve port configuration and back pressure. The pressure distribution determines the bubble size and number passing through the valve grooves and the sound pressure level of noise induced by collapsing bubbles. The inlet pressure mainly affects the saturation degree of bubbly flow inside the groove and the intensity of sound nressure level accordingly.展开更多
Annular grooved projectiles(AGPs)have drawn ongoing concerns as an advanced penetrator for their excellent anti-rebound capability in impacting metal plates.They could become embedded solidly in the target surface dur...Annular grooved projectiles(AGPs)have drawn ongoing concerns as an advanced penetrator for their excellent anti-rebound capability in impacting metal plates.They could become embedded solidly in the target surface during low-velocity impact.In this investigation,the firm embedding behavior of AGP was observed by impact experiments.Corresponding numerical simulations provided a better understanding of this process.Experimental and numerical results indicated that the firm embedding behavior of AGP was mainly due to the filling-material in the groove rather than the friction between the projectile and target,unlike traditional shape such as conical projectile.According to observation,firm embedding process can generally be subdivided into four stages:initial-cratering stage,groove-filling stage,fillingmaterial failure stage and rebound vibration stage.Moreover,the damage mechanics of target material around crater was obtained through microscopic tests.A comparison of the cross-sectional figures between the experiment and simulation proved that the analysis and the proposed method were reasonable and feasible,which further demonstrated that the firm embedding behavior has application potential in new concept warheads.展开更多
Gas Transmitting From West to East Project' is significant. It should ensure the welding quality and safety of pipeline. The task is very arduous to guarantee the quality of the project in the condition of long li...Gas Transmitting From West to East Project' is significant. It should ensure the welding quality and safety of pipeline. The task is very arduous to guarantee the quality of the project in the condition of long line, complex weather and geology features. In this paper, the welding cold cracking susceptibility of domestic X 70 pipeline steel adopted by the project, which is one of the most interesting questions of welding quality about petrol pipeline, was studied by means of oblique Y groove cracking test. The crack ratio of surface and section was tested under the conditions of different welding materials and preheat temperature .The thickness of plate steel was 14.7 mm and 10.3 mm . The results reveal that X 70 pipeline steel has good crack resistance. The research has important value for the construction of large scale pipeline engineering and the application of domestic X 70 pipeline steel.展开更多
Zhang Y J et al.[Zhang Y J,Zhang Z D,Zhu L Z and Xuan L 2011 Liquid Cryst.38 355] investigated the effects of finite polar anchoring on the azimuthal anchoring energy at a grooved interface,in which polar anchoring wa...Zhang Y J et al.[Zhang Y J,Zhang Z D,Zhu L Z and Xuan L 2011 Liquid Cryst.38 355] investigated the effects of finite polar anchoring on the azimuthal anchoring energy at a grooved interface,in which polar anchoring was isotropic in the local tangent plane of the surface.In this paper,we investigate the effects of both isotropic and anisotropic polar anchoring on the surface anchoring energy in the frame of Fukuda et al.’s theory.The results show that anisotropic polar anchoring strengthens the azimuthal anchoring of grooved surfaces.In the one-elastic-constant approximation(K11 = K22 = K33 = K),the surface-groove-induced azimuthal anchoring energy is entirely consistent with the result of Faetti,and it reduces to the original result of Berreman with an increase in polar anchoring.Moreover,the contribution of the surface-like elastic term to the Rapini-Papoular anchoring energy is zero.展开更多
The 30 mm thick ASTM4130 steel pipe was fabricated by gas tungsten arc welding and shielded metal arc welding under quenched and tempered conditions. Whereafier, the mechanical properties of welded joints of both V gr...The 30 mm thick ASTM4130 steel pipe was fabricated by gas tungsten arc welding and shielded metal arc welding under quenched and tempered conditions. Whereafier, the mechanical properties of welded joints of both V groove and combination double V groove were measured, while the microstructure feature and fracture morphology of both welded joints were investigated. Moreover, the effect of groove shapes on the properties of welded joints was explored. The results show that the welding efficiency of the combination double V groove joint is as two times as that of the V groove joint. But the hardness and toughness of the heat-affected zone (HAZ) with combination double V groove can not satisfy the requirements. Also, the coarse grain heat-affected zone (CGHAZ) of the cap layer is mainly composed of granular bainite, tempered martensite and a small amount of carbon-free bainite, and the fractured swface of the fusion line is entirely dominated by the quasi-cleavage mode. That the mechanical properties of the combination double V groove are lower than that of the V groove lie in the penetration ratio, welding heat input, and the areas and distribution feature of brittle zones. The combination double V groove is not suitable for the fabricating of ASTM4130 steel.展开更多
The effect of axial shallow groove on the nonlinear dynamic response and buckling of laminated cylindrical shells subjected to radial compression loading was investigated. Based on the first-order shear deformation th...The effect of axial shallow groove on the nonlinear dynamic response and buckling of laminated cylindrical shells subjected to radial compression loading was investigated. Based on the first-order shear deformation theory (FSDT), the nonlinear dynamic equations involving the transverse shear deformation and initial geometric imperfections were derived with the Hamilton philosophy. The axial shallow groove of the laminated composite cylindrical shell was treated as the initial geometric imperfections in the dynamic equations. A semi-analytical method of expanding displacements and loads along the circumferential direction and employing the finite difference method along the axial direction and in the time domain is used to solve the governing equations and obtain the dynamic response of the laminated shell. The B-R criterion was employed to determine the critical loads of dynamic buckling of the shell. The effects of the parameters of the shallow groove on the dynamic response and buckling were discussed in this paper and the results show that the axial shallow grooves greatly affect the dynamic response and buckling.展开更多
In working state, the dynamic performance of dry gas seal, generated by the rotating end face with spiral grooves, is determined by the open force of gas film and leakage flow rate. Generally, the open force and the l...In working state, the dynamic performance of dry gas seal, generated by the rotating end face with spiral grooves, is determined by the open force of gas film and leakage flow rate. Generally, the open force and the leakage flow rate can be obtained by finite element method, computational fluid dynamics method and experimental measurement method. However, it will take much time to carry out the above measurements and calculations. In this paper, the approximate model of parallel grooves based on the narrow groove theory is used to establish the dynamic equations of the gas film for the purpose of obtaining the dynamic parameters of gas film. The nonlinear differential equations of gas film model are solved by Runge-Kutta method and shooting method. The numerical values of the pressure profiles, leakage flux and opening force on the seal surface are integrated, and then compared to experimental data for the reliability of the numerical simulation. The results show that the numerical simulation curves are in good agreement with experimental values. Furthermore, the opening force and the leakage flux are proved to be strongly correlated with the operating parameters. Then, the function-coupling method is introduced to analyze the numerical results to obtain the correlation formulae of the opening force and leakage flux respectively with the operating parameters, i.e., the inlet pressure and the rotating speed. This study intends to provide an effective way to predict the aerodynamic performance for designing and optimizing the groove styles in dry gas seal rapidly and accurately.展开更多
Aluminum alloy plates were explosively cladded to stainless steel plates with trapezoidal grooves on the mating surface.The process parameters viz,loading ratio,standoff distance and flyer plate thickness were varied ...Aluminum alloy plates were explosively cladded to stainless steel plates with trapezoidal grooves on the mating surface.The process parameters viz,loading ratio,standoff distance and flyer plate thickness were varied based on the Taguchi analogy.The variation in the process parameters alters the kinetic energy dissipation and the deformation work performed at the interface,and dictates the interfacial wave amplitude and the mechanical strength of the dissimilar explosive clad.The optimum level of process parameters for attaining higher tensile and shear strength is computed by signal-to-noise ratio.Further,a mathematical model is developed for calculating tensile and shear strength of the clad,based on the regression analysis using statistical software Minitab-16,and the level of fit is determined by analysis of variance.展开更多
基金Supported by National Natural Science Foundation of China,No.82100568.
文摘BACKGROUND Groove pancreatitis(GP)is a rare condition affecting the pancreatic groove region within the dorsal-cranial part of the pancreatic head,duodenum,and common bile duct.As a rare form of chronic pancreatitis,GP poses a diagnostic and therapeutic challenge for clinicians.GP is frequently misdiagnosed or not considered;thus,the diagnosis is often delayed by weeks or months.The treatment of GP is complicated and often requires surgical intervention,especially pancreatoduodenectomy.CASE SUMMARY A 66-year-old man with a history of long-term drinking was admitted to the gastroenterology department of our hospital,complaining of vomiting and acid reflux.Upper gastrointestinal endoscopy showed luminal stenosis in the descending part of the duodenum.Abdominal computed tomography showed slight exudation in the descending and horizontal parts of the duodenum with broadening of the groove region,indicating local pancreatitis.The symptoms of intestinal obstruction were not relieved with conservative therapy,and insertion of an enteral feeding tube was not successful.Exploratory laparoscopy was performed and revealed a hard mass with scarring in the horizontal part of the duodenum and stenosis.Intraoperative frozen section analysis showed no evidence of malignancy,and side-to-side duodenojejunostomy was performed.Routine pathologic examination showed massive proliferation of fibrous tissue,hyaline change,and the proliferation of spindle cells.Based on the radiologic and pathologic characteristics,a diagnosis of GP was made.The patient presented with anastomotic obstruction postoperatively and took a long time to recover,requiring supportive therapy.CONCLUSION GP often involves the descending and horizontal parts of the duodenum and causes duodenal stenosis,impaired duodenal motility,and gastric emptying due to fibrosis.
基金the National Natural Science Foundation of China (No. 51605354)the Fundamental Research Funds for the Central Universities (WUT: 2015IVA021)+1 种基金the Innovative Research Team Development Program of Ministry of Education of China (No. IRT13087)the High-end Talent Leading Program of Hubei Province (No. 201286)
文摘The aim of this work is to develop a three-dimensional model of deep groove ball bearing to investigate the loaded stresses and central displacements of bearing rings. The equivalent stresses and central displacements of bearing rings are obtained based on the simulated analysis. Moreover, several parameters, such as load magnitude, raceway groove curvature radius(RGCR), thicknesses of outer and inner rings, are varied to investigate their effects on the equivalent stresses and central displacements of bearing rings. Research results provide useful guidelines for determining the design parameters.
文摘In order to improve the efficiency of film cooling, numerical investigation was carried out to study the effects of different film-cooled plates on surface heat transfer. Both grooved and non-grooved surfaces were concerned. The modeling was per- formed using Fluent software with the adoption of Shear-Stress Transport (SST) k-ωmodel as the turbulence closure. The coolant was supplied by a single film cooling hole with an inclination angle of 30°. The Mach numbers for the coolant flow and the mainstream flow were fixed at 0 and 0.6, respectively. At three blowing ratios of 0.5, 1.0 and 1.5, the aerodynamic behaviour of the mixing process as well as the heat transfer performance of the film cooling were presented. The numerical results were validated using experimental data extracted from a benchmark test. Good agreements between numerical results and the ex- perimental data were observed. For the film cooling efficiency, it shows that both local and laterally averaged cooling effectiveness can be improved by the non-smooth surface at different blowing ratios. Using the grooved surface, the turbulence intensity upon the plate can be reduced notably, and the mixing between the two flows is weakened due to the reduced turbu lence level. The results indicate that the cooling effectiveness of film cooling can be enhanced by applying the grooved surface.
基金Supported by National Natural Science Foundation of China(Grant No.51575490)National Key Basic Research Development Plan(973 Plan,Grant No.2014CB046404)+1 种基金Key Program of Zhejiang Provincial Natural Science Fund Project(Grant No.LZ15E050002)Zhejiang Provincial Natural Science Foundation of Youth Fund(Grant No.LQ17E050008)
文摘Spiral groove dry gas seal(S?DGS), the most widely used DGS in the world, encounters the problem of high leakage rate and inferior film stability when used in high?speed machinery equipment, which could not be well solved by optimization of geometrical parameters and molded line of spiral groove. A new type of bionic cluster spiral groove DGS(CS?DGS) is proved to have superior film stability than S?DGS at the condition of high?speed and low?pressure numerically. A bionic CS?DGS is experimentally investigated and compared with common S?DGS in order to provide evidence for theoretical study. The film thickness and leakage rate of both bionic spiral groove and common spiral groove DGS are measured and compared with each other and with theoretical values under different closing force at the condition of static pressure, high?speed and low?pressure, and the film stiffness and stiffness?leakage ratio of these two face seals are derived by the relationship between closing force and film thickness at the steady state. Experimental results agree well with the theory that the leakage and stiffness of bionic CS?DGS are superior to that of common S?DGS under the condition of high?speed and low?pressure, with the decreasing amplitude of 20% to 40% and the growth amplitude of 20%, respectively. The opening performance and stiffness characteristics of bionic CS?DGS are inferior to that of common S?DGS when rotation speed equals to 0 r/min. The proposed research provides a new method to measure the axis film stiffness of DGS, and validates the superior performance of bionic CS?DGS at the condition of high?speed and low?pressure experimentally.
基金Project supported by the Joint Fund of the National Natural Science Foundation of China and the China Academy of Engineering Physics(Grant No.U1530261)the National Natural Science Foundation of China(Grant Nos.11402032 and 11502030)the Science Challenge Project,China(Grant No.TZ2016001)
文摘Dynamic failure and ejection characteristics of a periodic grooved Sn surface under unsupported shock loading are studied using a smoothed particle hydrodynamics method. An "Eiffel Tower" spatial structure is observed, which is com- posed of high-speed jet tip, high-density jet slug, longitudinal tensile sparse zone, and complex broken zone between grooves. It is very different from the spike-bubble structure under supported shocks, and has been validated by detonation loading experiments. In comparison with that under supported shocks at the same peak pressure, the high-speed ejecta decreases obviously, whereas the truncated location of ejecta moves towards the interior of the sample and the total mass of ejecta increases due to the vast existence of low-speed broken materials. The shock wave profile determines mainly the total ejection amount, while the variation of V-groove angle will significantly alter the distribution of middle- and high-speed ejecta, and the maximum ejecta velocity has a linear corretation with the groove angle.
基金Supported by National Key Basic Research Program of China(973Program,Grant No.2012CB026003)National Science and Technology Major Project of China(Grant No.ZX06901)
文摘The current research on secondary O-ring seals used in mechanical seals has begun to focus on their dynamic properties. However, detailed analysis of the dynamic properties of O-ring seals in spiral groove gas face seals is lacking. In particular a transient study and a difference analysis of steady-state and transient performance are imperative. In this paper, a case study is performed to gauge the effect of secondary O-ring seals on the dynamic behavior(steady-state performance and transient performance) of face seals. A numerical finite element method(FEM) model is developed for the dynamic analysis of spiral groove gas face seals with a flexibly mounted stator in the axial and angular modes. The rotor tilt angle, static stator tilt angle and O-ring damping are selected to investigate the effect of O-ring seals on face seals during stable running operation. The results show that the angular factor can be ignored to save time in the simulation under small damping or undamped conditions. However, large O-ring damping has an enormous effect on the angular phase difference of mated rings, affecting the steady-state performance of face seals and largely increasing the possibility of face contact that reduces the service life of face seals. A pressure drop fluctuation is carried out to analyze the effect of O-ring seals on the transient performance of face seals. The results show that face seals could remain stable without support stiffness and O-ring damping during normal stable operation but may enter a large-leakage state when confronting instantaneous fluctuations. The oscillation-amplitude shortening effect of O-ring damping on the axial mode is much greater than that on the angular modes and O-ring damping prefers to cater for axial motion at the cost of angular motion. This research proposes a detailed dynamic-property study of O-ring seals in spiral groove gas face seals, to assist in the design of face seals.
基金National Natural Science Foundation of China,No.81602044Zhejiang Provincial Natural Science Foundation of China,No.LY19H160016 and No.LY17H030001+1 种基金Zhejiang Provincial Public Welfare Technology Application Research Projects,No.2015C33293Research Foundation of Health Bureau of Zhejiang Province,No.2014RCA031,No.2018RC077,No.2015KYA218,and No.2016KYB300
文摘BACKGROUND Groove pancreatitis(GP)is a type of chronic pancreatitis occurring in an anatomic area between the duodenum,head of the pancreas,and common bile duct.Duodenal obstruction is always caused by malignant pancreatic diseases,such as pancreatic head carcinoma,while is rarely induced by benign pancreatic diseases,such as pancreatitis.CASE SUMMARY A 39-year-old man presented with a 1-mo history of upper abdominal discomfort.His concomitant symptoms were abdominal distension,postprandial nausea,and vomiting.Contrast-enhanced computed tomography of the abdomen showed thickening of the intestinal wall with enhancement of the descending segment of the duodenum,which could not be clearly differentiated from the head of the pancreas.Upper gastrointestinal radiographs and gastrointestinal endoscopy showed a complete obstruction of the descending duodenum.An operation found that a 3-cm mass was located in the“groove part”of the pancreas and oppressing the descending duodenum.Pancreaticoduodenectomy was performed to relieve the obstruction and thoroughly remove the pancreatic lesions.The pathologic diagnosis was pancreatitis.The patient had an uneventful recovery with no complications.CONCLUSION Because of the special location and the contracture induced by long-term chronic inflammation,our case reminds surgeons that some benign pancreatic diseases,such as GP,can also present with symptoms similar to those of pancreatic cancer.This knowledge can help to avoid an unnecessary radical operation.
基金Selected from Proceedings of the 7th International Conference on Frontiers of DesignManufacturing(ICFDM'2006)This project is supported by National Basic Research Program of China(973 Program,No.2006CB705400)National Natural Science Foundation of China(No.50575200).
文摘The relationship between pressure distribution and cavitation (noise) inside throttling groove is investigated by numerical simulation and experimental method. A valve pocket with several transducers is performed to detect the pressure distributions inside the valve chamber, and the results fit quite well with the computational fluid dynamics(CFD) analysis. High-speed imaging techniques are employed to investigate the cavitation mechanisms, in particular bubble inception and cluster formation near the throttling groove. A spectrum analyzer is used to measure the sound pressure level of noise generated by the bubble flow. It is found that the pressure distributions inside the groove are sensitive to the valve port configuration and back pressure. The pressure distribution determines the bubble size and number passing through the valve grooves and the sound pressure level of noise induced by collapsing bubbles. The inlet pressure mainly affects the saturation degree of bubbly flow inside the groove and the intensity of sound nressure level accordingly.
基金financially supported by the National Natural Science Foundation of China [grant number 11472053]
文摘Annular grooved projectiles(AGPs)have drawn ongoing concerns as an advanced penetrator for their excellent anti-rebound capability in impacting metal plates.They could become embedded solidly in the target surface during low-velocity impact.In this investigation,the firm embedding behavior of AGP was observed by impact experiments.Corresponding numerical simulations provided a better understanding of this process.Experimental and numerical results indicated that the firm embedding behavior of AGP was mainly due to the filling-material in the groove rather than the friction between the projectile and target,unlike traditional shape such as conical projectile.According to observation,firm embedding process can generally be subdivided into four stages:initial-cratering stage,groove-filling stage,fillingmaterial failure stage and rebound vibration stage.Moreover,the damage mechanics of target material around crater was obtained through microscopic tests.A comparison of the cross-sectional figures between the experiment and simulation proved that the analysis and the proposed method were reasonable and feasible,which further demonstrated that the firm embedding behavior has application potential in new concept warheads.
文摘Gas Transmitting From West to East Project' is significant. It should ensure the welding quality and safety of pipeline. The task is very arduous to guarantee the quality of the project in the condition of long line, complex weather and geology features. In this paper, the welding cold cracking susceptibility of domestic X 70 pipeline steel adopted by the project, which is one of the most interesting questions of welding quality about petrol pipeline, was studied by means of oblique Y groove cracking test. The crack ratio of surface and section was tested under the conditions of different welding materials and preheat temperature .The thickness of plate steel was 14.7 mm and 10.3 mm . The results reveal that X 70 pipeline steel has good crack resistance. The research has important value for the construction of large scale pipeline engineering and the application of domestic X 70 pipeline steel.
基金Project supported by the Natural Science Foundation of Hebei Province,China (Grant No. A2010000004)the National Natural Science Foundation of China (Grant No. 60736042)the Key Subject Construction Project of Hebei Provincial University,China
文摘Zhang Y J et al.[Zhang Y J,Zhang Z D,Zhu L Z and Xuan L 2011 Liquid Cryst.38 355] investigated the effects of finite polar anchoring on the azimuthal anchoring energy at a grooved interface,in which polar anchoring was isotropic in the local tangent plane of the surface.In this paper,we investigate the effects of both isotropic and anisotropic polar anchoring on the surface anchoring energy in the frame of Fukuda et al.’s theory.The results show that anisotropic polar anchoring strengthens the azimuthal anchoring of grooved surfaces.In the one-elastic-constant approximation(K11 = K22 = K33 = K),the surface-groove-induced azimuthal anchoring energy is entirely consistent with the result of Faetti,and it reduces to the original result of Berreman with an increase in polar anchoring.Moreover,the contribution of the surface-like elastic term to the Rapini-Papoular anchoring energy is zero.
基金supported and funded in part by a grant(Project No.ZR2013EEQ027)from the Natural Science Foundation of Shandong Provincea grant(Project No.14CX02066A)from the Fundamental Research Funds for the Central Universities of China
文摘The 30 mm thick ASTM4130 steel pipe was fabricated by gas tungsten arc welding and shielded metal arc welding under quenched and tempered conditions. Whereafier, the mechanical properties of welded joints of both V groove and combination double V groove were measured, while the microstructure feature and fracture morphology of both welded joints were investigated. Moreover, the effect of groove shapes on the properties of welded joints was explored. The results show that the welding efficiency of the combination double V groove joint is as two times as that of the V groove joint. But the hardness and toughness of the heat-affected zone (HAZ) with combination double V groove can not satisfy the requirements. Also, the coarse grain heat-affected zone (CGHAZ) of the cap layer is mainly composed of granular bainite, tempered martensite and a small amount of carbon-free bainite, and the fractured swface of the fusion line is entirely dominated by the quasi-cleavage mode. That the mechanical properties of the combination double V groove are lower than that of the V groove lie in the penetration ratio, welding heat input, and the areas and distribution feature of brittle zones. The combination double V groove is not suitable for the fabricating of ASTM4130 steel.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10202013)
文摘The effect of axial shallow groove on the nonlinear dynamic response and buckling of laminated cylindrical shells subjected to radial compression loading was investigated. Based on the first-order shear deformation theory (FSDT), the nonlinear dynamic equations involving the transverse shear deformation and initial geometric imperfections were derived with the Hamilton philosophy. The axial shallow groove of the laminated composite cylindrical shell was treated as the initial geometric imperfections in the dynamic equations. A semi-analytical method of expanding displacements and loads along the circumferential direction and employing the finite difference method along the axial direction and in the time domain is used to solve the governing equations and obtain the dynamic response of the laminated shell. The B-R criterion was employed to determine the critical loads of dynamic buckling of the shell. The effects of the parameters of the shallow groove on the dynamic response and buckling were discussed in this paper and the results show that the axial shallow grooves greatly affect the dynamic response and buckling.
基金Supported by National Natural Science Foundation of China(Grant No.51276125)National Key Basic Research Development Program of China(973 Program,Grant No.2012CB720101)
文摘In working state, the dynamic performance of dry gas seal, generated by the rotating end face with spiral grooves, is determined by the open force of gas film and leakage flow rate. Generally, the open force and the leakage flow rate can be obtained by finite element method, computational fluid dynamics method and experimental measurement method. However, it will take much time to carry out the above measurements and calculations. In this paper, the approximate model of parallel grooves based on the narrow groove theory is used to establish the dynamic equations of the gas film for the purpose of obtaining the dynamic parameters of gas film. The nonlinear differential equations of gas film model are solved by Runge-Kutta method and shooting method. The numerical values of the pressure profiles, leakage flux and opening force on the seal surface are integrated, and then compared to experimental data for the reliability of the numerical simulation. The results show that the numerical simulation curves are in good agreement with experimental values. Furthermore, the opening force and the leakage flux are proved to be strongly correlated with the operating parameters. Then, the function-coupling method is introduced to analyze the numerical results to obtain the correlation formulae of the opening force and leakage flux respectively with the operating parameters, i.e., the inlet pressure and the rotating speed. This study intends to provide an effective way to predict the aerodynamic performance for designing and optimizing the groove styles in dry gas seal rapidly and accurately.
文摘Aluminum alloy plates were explosively cladded to stainless steel plates with trapezoidal grooves on the mating surface.The process parameters viz,loading ratio,standoff distance and flyer plate thickness were varied based on the Taguchi analogy.The variation in the process parameters alters the kinetic energy dissipation and the deformation work performed at the interface,and dictates the interfacial wave amplitude and the mechanical strength of the dissimilar explosive clad.The optimum level of process parameters for attaining higher tensile and shear strength is computed by signal-to-noise ratio.Further,a mathematical model is developed for calculating tensile and shear strength of the clad,based on the regression analysis using statistical software Minitab-16,and the level of fit is determined by analysis of variance.