The steady laminar mixed convection boundary layer flow and heat transfer of a micropolar fluid near the stagnation point on a stretched vertical surface with prescribed skin friction were considered.The governing par...The steady laminar mixed convection boundary layer flow and heat transfer of a micropolar fluid near the stagnation point on a stretched vertical surface with prescribed skin friction were considered.The governing partial differential equations were transformed into a system of ordinary differential equations,which were then solved numerically using the shooting method.Results for the stretching velocity,the local Nusselt number,the temperature,and the velocity profiles are presented for various values of the mixed convection parameter λ and material parameter K when the Prandtl number is equal to 1.Both assisting（heated plate） and opposing（cooled plate） flow regions are considered.It is found that dual solutions exist for both assisting and opposing flows.展开更多
In this paper,we firstly review the carbon layered surface prepared with electron cyclotron resonance (ECR) plasma sputtering. Secondly,the friction behavior of carbon layered surface under pin-on-disk testing is desc...In this paper,we firstly review the carbon layered surface prepared with electron cyclotron resonance (ECR) plasma sputtering. Secondly,the friction behavior of carbon layered surface under pin-on-disk testing is described. Furthermore,the contact stress evolution processes of layered surface with and without transfer layer during wear are given for understanding the contact mechanisms. Finally,a three-dimension (3D) local yield map of layered surface is introduced,which is useful to predict the possible contact mechanisms.展开更多
Based on Zeevaert＇s method, a theoretical formula was developed to calculate the negative skin friction of pile in layered soil. For practical purpose,a cut-and-try method was proposed to determine neutral point. Cas...Based on Zeevaert＇s method, a theoretical formula was developed to calculate the negative skin friction of pile in layered soil. For practical purpose,a cut-and-try method was proposed to determine neutral point. Case studies indicate that the total calculated negative skin friction was in agreement with the measured one, which verifies the feasibility and practicability of theoretical formula. Furthermore, the methods for calculating efficiency factor of drag load and settlement were also given.展开更多
Application of powder boronizing to mechanical industry has been restricted because of the brittleness of boronized layer, which inevitably leads to decrease of service life of boronized parts. Therefore, attention sh...Application of powder boronizing to mechanical industry has been restricted because of the brittleness of boronized layer, which inevitably leads to decrease of service life of boronized parts. Therefore, attention should be paid to reducing the brittleness of boronized layer without decreasing its high hardness. In the present paper, a study on the effect of micro-addition rare earth and chrome on friction and wear behavior of boronized layer was carried out using an MM-200 wear test machine. Compared with that of pure single Fe2B phase, the brittleness of the boronized layer containing minim rare earth and chrome elements, obtained by powder RE-chrome-boronizing, is reduced, which results in increasing the bearing capacity and wear resistance of the boronized layer. The friction and wear mechanism is also briefly analyzed.展开更多
A new technique was introduced that TiN permeation layer composed of diffusion and deposition layer was synthesized on the surface of Q235 steel using plasma point discharge and hollow cathode effect, and then TiB2 fi...A new technique was introduced that TiN permeation layer composed of diffusion and deposition layer was synthesized on the surface of Q235 steel using plasma point discharge and hollow cathode effect, and then TiB2 film was deposited （PVD） on newly-formed surface to create TiN/TiB2 multi-permeation layer. The thickness of this multi-permeation layer is above 10μm and the composition and hardness have graded distribution. It has metallurgical bonding with substrate and the bonding strength is high without any spallation phenomenon. In addition comparative research, between TiN/TiB2 multi-permeation layer and TiB2 film which is directly deposited （PVD） on Q235 steel substrate, on surface appearance, microhardness and friction-abrasion property was carried out. The results show that both of surface consist of uniform, compact and fine cellular structure. Surface microhardness of TiN/TiB2 multi-permeation layer is higher, reaching HV2600; but its average friction coefficient is lower, abrasion crack is shallower and wear resistance is better.展开更多
基金the financial supports received in the form of fundamental research grant scheme (FRGS)the financial supports received in the form of research university grant (GUP)
文摘The steady laminar mixed convection boundary layer flow and heat transfer of a micropolar fluid near the stagnation point on a stretched vertical surface with prescribed skin friction were considered.The governing partial differential equations were transformed into a system of ordinary differential equations,which were then solved numerically using the shooting method.Results for the stretching velocity,the local Nusselt number,the temperature,and the velocity profiles are presented for various values of the mixed convection parameter λ and material parameter K when the Prandtl number is equal to 1.Both assisting（heated plate） and opposing（cooled plate） flow regions are considered.It is found that dual solutions exist for both assisting and opposing flows.
基金National Natural Science Foundation of China(No.90923027No.51175405)
文摘In this paper,we firstly review the carbon layered surface prepared with electron cyclotron resonance (ECR) plasma sputtering. Secondly,the friction behavior of carbon layered surface under pin-on-disk testing is described. Furthermore,the contact stress evolution processes of layered surface with and without transfer layer during wear are given for understanding the contact mechanisms. Finally,a three-dimension (3D) local yield map of layered surface is introduced,which is useful to predict the possible contact mechanisms.
基金Shandong Provincial Education Department Fund (No.J09LE05)
文摘Based on Zeevaert＇s method, a theoretical formula was developed to calculate the negative skin friction of pile in layered soil. For practical purpose,a cut-and-try method was proposed to determine neutral point. Case studies indicate that the total calculated negative skin friction was in agreement with the measured one, which verifies the feasibility and practicability of theoretical formula. Furthermore, the methods for calculating efficiency factor of drag load and settlement were also given.
文摘Application of powder boronizing to mechanical industry has been restricted because of the brittleness of boronized layer, which inevitably leads to decrease of service life of boronized parts. Therefore, attention should be paid to reducing the brittleness of boronized layer without decreasing its high hardness. In the present paper, a study on the effect of micro-addition rare earth and chrome on friction and wear behavior of boronized layer was carried out using an MM-200 wear test machine. Compared with that of pure single Fe2B phase, the brittleness of the boronized layer containing minim rare earth and chrome elements, obtained by powder RE-chrome-boronizing, is reduced, which results in increasing the bearing capacity and wear resistance of the boronized layer. The friction and wear mechanism is also briefly analyzed.
文摘A new technique was introduced that TiN permeation layer composed of diffusion and deposition layer was synthesized on the surface of Q235 steel using plasma point discharge and hollow cathode effect, and then TiB2 film was deposited （PVD） on newly-formed surface to create TiN/TiB2 multi-permeation layer. The thickness of this multi-permeation layer is above 10μm and the composition and hardness have graded distribution. It has metallurgical bonding with substrate and the bonding strength is high without any spallation phenomenon. In addition comparative research, between TiN/TiB2 multi-permeation layer and TiB2 film which is directly deposited （PVD） on Q235 steel substrate, on surface appearance, microhardness and friction-abrasion property was carried out. The results show that both of surface consist of uniform, compact and fine cellular structure. Surface microhardness of TiN/TiB2 multi-permeation layer is higher, reaching HV2600; but its average friction coefficient is lower, abrasion crack is shallower and wear resistance is better.
