摘要：Wear and scuffing failures often occur in marine transmission gears due to high friction and flash temperature at the interface between the *** this paper,a numerical solution procedure was developed for the predictions of transient friction and flash temperature in the marine timing gears during one meshing circle based on the 3D line contact mixed lubrication simulation,which had been verified by comparing the flash temperature with those from Blok’s *** effect of machined surface roughness on the mixed lubrication characteristics is *** obtained results for several typical gear pairs indicate that gear pair 4-6 exhibits the largest friction and the highest interfacial temperature increase due to severe rough surface asperity contacts,while the polished gear surfaces yield the smallest friction and the lowest interfacial *** addition,the influences of the operating conditions and the gear design parameters on the friction-temperature behaviors are *** is observed that the conditions of heavy load and low rotational velocity usually lead to significantly increased friction and *** the meantime,by optimizing the gear design parameters,such as the modulus and the pressure angle,the performance of interfacial friction and temperature can be significantly improved.

摘要：Laboratory tests were conducted at the Irrigation Devices and Equipment’s Test Laboratory, Agricultural Engineering Research Institute, Agriculture Research Center, Giza, Egypt. The experimental design of laboratory experiments was split in randomized complete block design with three replicates. Laboratory tests carried out on three irrigation lateral lines of 40, 60, 80 m under the following three drip irrigation circuit (DIC) designs;1) one manifold for lateral lines or closed circuits with one manifold of drip irrigation system (CM1DIS);2) closed circuits with two manifolds for lateral lines (CM2DIS), and 3) traditional drip irrigation system (TDIS) as a control. The aims of the work were to study the effect of drip irrigation circuits (DIC) and lateral lines lengths (LLL;where): (LLL1 = 40 m, LLL2 = 60 m, and LLL3 = 80 m) on pressure head (PH) and friction loss (FL). Regarding to LLL and according to PH values, DIC designs could be ranked in the following ascending order: TDIS 1DIS 2DIS. The differences in PH among DIC designs were significant at the 1% level. The depressive effects of LLL on PH could be ranked in the following ascending order: LLL1 2 ≤ LLL3. Differences in PH among LLL treatments were significant at the 1% level except that between LLL2 and LLL3. The effects of interactions among: DIC × LLL on PH were significant at the 1% level with some exceptions. The highest value of PH (9.5 m) and the lowest one (6.05 m) were achieved in the interactions of CM2DIS × LLL1 and TDIS × LLL3, respectively. The shapes of the energy gradient lines were affected by DIC and LLL treatments used through their effect on ?H/H ratio. However, they followed similar trends. According to the FL values, DIC and LLL treatments could be ranked in the following descending orders TDIS > CM1DIS > CM2DIS and LLL1 > LLL2 > LLL3. The differences in FL among DIC and LLL were significant and the effects of interactions among DIC × LLL on FL were significant at the 1% level. The maxim

摘要：Split Hopkinson pressure bar (SHPB) has become a frequently used technique to measure the uniaxial compressive stress-strain relation of various engineering materials at high strain-rates. The accuracy of an SHPB test is based on the assumption of uniaxial and uniform stress distribution within the specimen, which, however, is not always satisfied in an actual SHPB test due to the existence of some unavoidable negative factors, e.g., interface friction constrains. Kinetic interface friction tests based on a simple device for engineering materials testing on SHPB tests are performed. A kinetic interface friction model is proposed and validated by implementing it into a numerical model. It shows that the proposed simple device is sufficient to obtain kinetic interface friction results for common SHPB tests. The kinetic friction model should be used instead of the frequently used constant friction model for more accurate numerical simulation of SHPB tests.

摘要：A macro-micro dual-drive positioning system showing good potential for high acceleration and high precision positioning required in IC packaging applications is devised in this paper. The dual-drive positioning stage uses a VCM (voice coil motor) driven macro positioning stage and a PZT piezo-electric driven micro positioning stage. The coupling characteristics of the system are analyzed to produce a control structure with a micro positioning stage that can dynamically compensate for the positioning error produced by the macro positioning stage. Models of the two positioning stages are described. The models cover both the mechanism and the actuator. For the macro positioning stage, friction characteristics are taken into account, and a controller with an LQG (linear-quadratic-Gaussian) control algorithm combining a feed-forward compensation algorithm is derived. A PID controller is used to control the micro positioning stage. Detailed designs are derived for the proposed approach, and the performance is validated by simulation.

摘要：Jet pulse assembly is one of the main components of jet hydraulic *** pressure wave characteristics produced by jet pulse assembly have an important influence on the performance of the *** this paper,the structure and working principle of jet pulse assembly are studied,the mechanical analysis model of piston rod is established,the dynamic resistance ratio formula of jet pulse assembly is deduced,and the numerical simulation test of 89-mm jet pulse assembly structure parameters is carried *** results show that the piston rod downward stroke is driven by both the jet element driving force and the throttle plate load driving force,and can stably *** driving force of the piston rod upward stroke jet element is opposite to the load acting force of the throttle disc,and the jet driving force needs to be greater than the load resistance of the throttle disc to stably *** dynamic resistance ratio formula is *** the area of the end of the piston rod is reduced,the resistance of the throttle disc is reduced and the jet power is increased,thus solving the problem of insufficient power of the piston rod in the upstroke and ensuring the normal operation of the *** groups of numerical simulation tests were carried out,and it was found that the pressure amplitude and pressure drop of the tool decreased significantly with the increase of the tool size,and the error between the numerical simulation value and the theoretical calculation value was less than 9%,which verified the correctness of the *** is suggested to select tools on site according to the drilling construction situation to ensure the drilling effect.

摘要：The forming performance of sheet metals in the deep-drawing process with ultrasonic vibrations can be improved by the surface effect between the sheet metal and the die.A sheet metal friction test with ultrasonic vibrations is performed to explore the cause of the surface *** frictional characteristics are investigated,and the corresponding friction expressions are established based on the contact mechanics and the elastic–plastic contact model for rough *** is caused by the elastic–plastic deformation of contacting asperities under normal *** actual contacting region between two surfaces increases with normal loads,whereas the normal distance *** normal distance between the contacting surfaces is changed,asperities generate a tangential deformation with ultrasonic vibrations,and the friction coefficient is eventually *** vibrations are applied on a 40Cr steel punch at the frequency of 20 kHz and the amplitude of 4.2μ*** the friction tests,the punch is perpendicular to the surface of the magnesium alloy AZ31B sheet metals and is sliding with a relative velocity of 1 mm/*** test results show that the friction coefficient is decreased by approximately 40%and the theoretical values are in accordance with the test values;Ultrasonic vibrations can clearly reduce wear and improve the surface quality of parts.

摘要：Experimental and numerical analyses for the effect of the thickness of gap generator blank（GGB） on the formability of the outer blanks were investigated. The thickness of the GGB has the greatest impact on the thinning of the lowest blank. In addition, the friction at different regions and the additional interlayer contacts can also affect the thinning of different regions as well as increase the punch force. This work will enhance the understanding of simultaneous multi-layered blanks forming and will help the composite design engineers to tailor requirement-specific hybrid parts such as fiber metal laminates（FMLs） and functionally graded structures（FGSs） for hi-tech applications.

摘要：Ultra strong polyethylene fibers can be made by gel-spinning of Ultra High Molecular Weight Polyethylene (UHMWPE). Such fibers exhibit extraordinary properties. They show very high tensile strength and stiffness and low density. On the other hand, the axial and transverse compression strength is low. This is a large difference with other advanced fibers like glass and carbon fibers. Additionally, the fibers are chemically inert and the bonding strength to other materials like resins is weak. Moreover, the coefficient of friction is very low, so the fiber is extremely slippery. Another property is viscoelasticity;the fiber elongates due to creep at higher loads or temperatures. This exceptional combination of properties explains why gel-spun UHMWPE fibers are not always applied in straight forward ways, e.g. like glass and carbon fibers in composites. On the other hand, weaknesses like the limited compression strength are related to very damage tolerant behavior on a micro scale. This opened application areas like providing of cut resistance. This paper describes some established applications and shows the relationship between the properties and the applications. Furthermore, some emerging applications are discussed and it is demonstrated how weaknesses can be turned into advantages.