滑动摩擦力影响因素解析

摩擦力就是两个互相接触的物体，当它们要发生或已经发生相对运动时，就会在接触面上产生阻碍相对运动的力，这种力叫摩擦力。摩擦力可分为动摩擦和静摩擦，动摩擦又可分为滑动摩擦和滚动摩擦。一个物体在另一个物体表面滑动时产生的摩擦力叫滑动摩擦力；一个物体在另一个物体表面滚动时产生的摩擦力叫滚动摩擦力。一个物体在另一个物体表面有相对运动的趋势时产生的摩擦力叫静摩擦力。     

运用平衡条件计算摩擦力

摩擦力的计算分成两大类：一是求相对静止物体受到的摩擦力；二是求匀速直线运动物体受到的摩擦力．当物体处于静止状态或匀速直线运动状态时，我们可通过力的平衡条件来计算摩擦力．一、求相对静止物体受到的摩擦力例１如图１所示，用F＝１０N的力拉一重４０N的物体，物体没动，则物体受到的摩擦力的大小是；若改用２０N的力来拉该物体，仍未动，则此时摩擦力的大小应为．分析：首先要明确静摩擦力的方向．由于放在水平面上的物体受到向右的拉力，物体有向右运动的趋势，故静摩擦力的方向向左，其次抓住本题中的关键词“没动”，即物体处…     

跳出误区 再议摩擦

摩擦力有动摩擦力和静摩擦力之分．解题时要弄清是哪一种，要对照摩擦力产生的条件或物体的平衡条件去考虑物体向有无摩擦力，再考虑它的方向、大小、种类问题．     

探究高中物理——摩擦力

<正>摩擦力是高考必考的一个考点,同时也是难点,正确认识并掌握摩擦力的相关概念,对解题思路有极大的提升。在摩擦力分析过程中,涉及静动摩擦力的方向及摩擦力做正功还是负功,因此对摩擦力进行分析是非常有必要的。一、摩擦力产生的条件1.物体接触且存在弹性力:在判断物体之间是否存在摩擦力的方法,可以把一个物体去掉,看是否会改变另一个物体的运动状态。若物体运动状态发生变化,则两个物体之间存在一定的弹性力;若物体仍然保持原     

摩擦力的三个性质

1．摩擦力的方向,有相对性 摩擦力总是阻碍物体的相对运动或相对运动趋势．这里的“相对”是指相对于提供摩擦力的施力物体．无论相互接触的物体如何运动和受力,都应该选择施力物体为参考系来讨论摩擦力的方向．     

“弹力与摩擦力”的确定性和不确定性

由于弹力和摩擦力都为被动力，因此存在着应变性。当物体运动情景和受力情况明确时，弹力和摩擦力方向及相应的大小具有确定性。当物体运动情景不明或受除弹力、摩擦力以外的力大小无法确定时，相应情景下弹力和摩擦力方向及相应的大小具有不确定性，在某些习题上表现为存在多个可能的正确选项，这一点是高考对弹力和摩擦力考查的热点。     

摩擦力方向的投影演示

摩擦力方向的投影演示杨泽南，贾彩娟长期以来，物体受到的摩擦力方向在课堂上无法演示，因此教学效果很不理想。我们经过多年的探索，利用常见的材料制作了一只摩擦力方向投影演示教具，既能直观地演示物体受到的滑动摩擦力方向与其运动方向相反的物理现象，又能直观地演...     

谈谈课堂教学中钓预设和生威——从一堂“问题课”说起

事情发生在“摩擦力”这节课上。……“滑动摩擦力的大小与接触物体间的压力成正比，与接触面的粗糙程度有关。物体表面越粗糙，同样压力下摩擦力越大；物体表面越光滑，摩擦力就越小。”说这段话的时候，我很自信，因为实在是太熟悉了，我也丝毫没有对这句话的科学性产生过怀疑。但接下来发生的事让我大感意外。     

《摩擦力》教学故事

“上节课同学们已经验证了摩擦力大小与物体重量有关系：物体越重,摩擦力越大;物体越轻,摩擦力越小。摩擦力大小可能还与什么因素有关？”一上课,我就抛出了新的研究问题。     

有无相对运动的判定及应用

一、问题提出将一物体迭放到(或滑上去)另一物体的表面上,如果两物体的接触面是粗糙的,两物体间可能就会产生摩擦力的作用。两物体间摩擦力的有无与两物体的运动状态密切相关,而摩擦力的有无及大小的变化又会反过来对物体的运动状态产生重要的影响。物体的运动状态与摩擦力之间的这种制约关系,在一定条件下就会造成迭放到一起的两物体问有时存在相对运动,而有时又不存在相对运动。     

Modeling and analysis of wet clutch engagement characteristics

A mathematical model was developed to analyze the characteristics of the wet clutch during engagement. The lubricant squeeze action was simulated with Patir and Cheng average flow model in which the permeability of friction material is taken into account, and the asperity load is calculated according to the Greenwood and Tripp approach. In this model, effects of friction material permeability, applied load and driving velocity on the engagement characteristics of the wet clutch were studied. The results show that friction material with high permeability reduces the film thickness rapidly and increases the torque peak; the applied load increases the asperity contact pressure and the friction torque, and reduces the engagement time; the driving velocity mainly increases the engagement time. The theoretical torque and relative velocity curves agree qualitatively with the experimental ones, which verifies the wet clutch engagement model.     

非晶材料弛豫过程中内耗的唯象描述

本文从晶态材料弛豫过程中内耗的唯象描述的基本思想出发,同时考虑到近年来对非晶材料结构弛豫规律的种种描述,将传统的构造力学参数模型作为弛豫单元的作法与现在流行的双能级模型统一起来,对非晶材料弛豫过程中的内耗进行了唯象处理,得到了新的弛豫规律。     

分形理论在摩擦表面研究中的应用

引入分形理论来研究摩擦表面 .根据摩擦表面几何特征、形貌参数建立分形布朗运动模型 ,对分形数的求解进行了探讨 ,重点阐述分形数的物理意义和在摩擦表面形貌研究中运用分形数的优点     

摩擦摆支座在钢管混凝土拱桥中减震效果研究

以跨度为120m的刚性拱肋柔性系杆的下承式钢管混凝土拱桥为分析模型,利用摩擦摆减震隔震支座对简支体系的桥跨结构进行减震研究,运用MIDAS有限元软件模拟多维人工地震波输入以检验摩擦摆系统的减震效果。分析结果证明了在大跨度钢管混凝土拱桥中应用摩擦摆隔震支座系统的有效性。     

Hypoplasticmodeling of soil-structure interfaces in offshore applications

Cyclic and monotonic loaded offshore structures (e.g. piles, pipelines, cables, and suction-buckets) must be designed and calculated considering the effects of the soil-structure interaction. An advanced constitutive soil model must be used, but a simplified Mohr-Coulomb friction law is applied for the soil-structure interface. The Mohr- Coulomb model is a simple bilinear friction model that cannot take into account monotonic and cyclic interface phenomena. These include hardening, softening, and stiffness degradation under loading. However, we propose two advanced hypoplastic interface models for fine- and coarse-grained soils with intergranular strain concept. The intergranular strain concept has been proven to be an efficient way to model the small-strain deformation and un/reloading behavior of soils. The intergranular strain concept is therefore used to enhance the prediction capabilities of the hypoplastic interface models. Differences of the recent model formulation compared with previous versions are presented and discussed based on simulation. This is followed by an application of different models in finite-element simulations. The new models are used to simulate cyclic direct shear interface tests. Furthermore, the advanced interface model is used for simulation of a torodial penetrometer penetration problem. Several aspects, which are particularly important for offshore structures, are compared with the simple Mohr-Coulomb friction model.     

Hybrid adaptive compensation control scheme for high-precision servo system

In this paper,a hybrid adaptive compensation control scheme is proposed to compensate the friction occurrence and other nonlinear disturbance factors that exist in the high-precision servo system.An adaptive compensation controller with a dual-observer structure is designed,while the LuGre dynamic friction model with non-uniform parametric uncertainties characterizes the friction torque.Considering the influence of the periodic disturbance torque and parametric uncertainties,fuzzy systems and a robust term are employed.In this way,the whole system can be treated as a simple linear model after being compensated,then the proportional-derivative (PD) control law is applied to enhancing the control performance.On the basis of Lyapunov stability theory,the global stability and the asymptotic convergence of the tracking error are proved.Numerical simulations demonstrate that the proposed scheme has potentials to restrain the impact of disturbance and improving the tracking performance.     

Non-linear 2-DOF model and centre manifold theory to study limit cycle oscillations caused by drum-brake judder

This paper presents the research on the laws of systematic-parameter dependent variation in the vibration amplitude of drum-brake limit cycle oscillations (LCO). We established a two-degree non-linear dynamic model to describe the low-frequency vibration of the drum brake, applied the centre manifold theory to simplify the system, and obtained the LCO amplitude by calculating the normal form of the simplified system at the Hopf bifurcation point. It is indicated that when the friction coefficient is smaller than the friction coefficient at the bifurcation point, the amplitude decreases; whereas with a friction coefficient larger than the friction coefficient of bifurcation point, LCO occurs. The results suggest that it is applicable to suppress the LCO amplitude by changing systematic parameters, and thus improve the safety and ride comfort when applying brake. These findings can be applied to guiding the design of drum brakes.     

Numerical Analysis of Soil Plug Inside Suction Foundations During Suction Penetration by Discrete Element Method

The phenomenon of the soil plug usually rising inside the suction foundations during suction penetration was quantitatively described and predicted. The formation process of the soil plug was simulated and calculated by DEM （discrete element method） model. The seepage flow, the self-weight of soil, the friction on the chamber wall as well as the suction inside the chamber are considered as the main external forces in the process. The results are compared with a set of laboratory model tests performed by using three soil types （sand, silty clay and clay） in the Bohai Sea area. The heights of soil plug from numerical estimations are lower than those from model test results, mainly because the suction pressure and friction resistance are applied in an ideal way under the numerical simulation.     

Reinforcement Efficiency Analysis of Geosynthetic-Reinforced Embankment with Different Soil Properties

The use of high strength geosynthetic in the base ofembankments constructed over soft soil layers is a commonpractice.Those embankments are called geosynthetic-rein-forced embankments (GRE) . Geosynthetic reinforcementcanimprove stability,decrease lateral and vertical soil de-formations under working conditions , and allow embank-ments to be constructedto greater height[1].However ,the effectiveness of geosynthetic reinforce-mentin GREvaries greatlyin different cases .Despitethereare many s…     

Excitation prediction by dynamic transmission error under sliding friction in helical gear system

Monte Carlo method was adopted to calculate the meshing error considering the manufacture error and assembly error of the meshing point along the time-varying contact line for helical gear pair. The flexural-torsion-axis dynamic model coupled was established under the tooth friction force and solved by the perturbation method to compute real dynamic tooth load. The change laws of the friction force and friction torque were obtained in a meshing period. The transmission error formulation was analyzed to introduce meshing excitations. The maximum dynamic transmission error, the maximum meshing force and the maximum dynamic factor were calculated under different speeds, external loads and damping factors. The conclusions can provide theoretical basis for the gear design especially in tooth profile correction.