《冲压与塑料成形设备》是高职院校模具设计与制造专业的一门专业基础课程,为了更好地提升课程的教学效果,从教学内容的选取与重构、教学模式与方法改革、多元化课程考核体系的构建等方面开展了课程改革的应对措施.

It's important to research on tactical application of Poised Depth Charge(PDC)for surface ship against torpedo.First,the assault rules of wake homing torpedo are introduced.Second,the math model on advance angle at self-guided system of torpedo searching target is established.Third,the occasion of applying stern-dropped PDC is discussed,and a pertinent math model is established.Fourth,the simulation test is performed.The application rules and the interception probability of two types of PDC are analyzed.The result proves that the interception probability of stern-dropped PDC is greater,and the interception optimum effect can be acquired by the combined application of two types of PDC.

A time-dependent EHL problem of a ball impacting a plate by a cyclic approach-separation motion has been solved. Previous experimental findings by some of the authors have been numerically confirmed,i.e.,the nearly constant central film thickness during the load-sustaining stage,and the linear relationship between this constant film thickness and the frequency in a log-log scale. The numerical results show a constriction in the trace of central film thickness versus time. Similar to the experiments,numerical results give a dimple film shape,which is caused by the high pressure induced within the contact region. The influences of the frequency,the static contact load on the film thickness and the film pressure have also been investigated.

Studies about pure squeeze elastohydrodynamic lubrication(EHL) have disclosed a film profile with a central dimple.In this study,the steel ball impacts the steel plate with an oil layer thickness of hoil under an initial impact gap of hini,a circumferential dimple is formed at the periphery of the contact instead of the familiar central dimple,parameter studies show that When the initial central impact gap is large,the film pressure and the film thickness are similar to those in previous free ball dropping problems,including the spike in the central pressure time trace and the central dimple formed at the end of the approach.As the initial impact gap decreases,the maximum pressure changes its location from the contact center to the periphery,correspondingly,the central dimple becomes less distinct and another circumferential dimple appears at the periphery of the contact.Further numerical calculations,under a small initial impact gap the periphery dimple appears when the oil layer is thick enough.In cases where the initial impact gap is small,the central oil film is much thinner than that under large initial impact gaps when the lubricant is "frozen",and then no marked central dimple can be formed.In the periphery region,the surface gap is closing at a small initial gap and the local squeeze effect in the periphery region becomes strong,and therefore a periphery dimple is generated.

Flow of the entrapped lubricant formed by impacting in elastohydrodynamic contact region was observed by optical interferometry,and the movement of the entrapped lubricant core was measured in different conditons.Results show that the entrapped lubricant moved at the same velocity as the entrainment velocity under pure rolling condition.Under pure glass disc sliding,the velocity of the entrapped lubricant was much slower than that under pure rolling,however under pure steel ball sliding condition,the velocity of the entrapped lubrication was a little more smaller than the entrainment velocity.The present results confirm the existence of wall slippage in elastohydrodynamic lubrication contact,and the stress of the interface was larger than the bond of the solid and the lubricant which caused the slippage.