专业英语第三次作业,第四次作业

第三次作业

翻译下列句子

1. The simplest closed-loop linkage is the four-bar linkage, which has three moving links (plus one fixed link) and four pin joints.

2. Although the four-bar linkage and slider-crank mechanism are very useful and found in thousands of applications, we can see that these linkages have limited performance level

3. The process of drawing kinematic diagrams and determining degrees of freedom of

mechanisms are the first steps in both the kinematic analysis and synthesis process. 4. The ability to visualize relative motion, to reason why a mechanism is designed the way it is, and the ability to improve on a particular design are marks of a successful kinematician.

5.Kinematic inversion is the process of fixing different links of a chain to create different mechanisms.

第四次作业

翻译下列短文

1. A kinematic chain is a system of links, that is, rigid bodies, which are either jointed together or are in contact with one another in a manner that permits them to move relative to one another. If one of the links is fixed and the movement of any other link to a new position will cause each of the other links to move to definite predictable position, the system is a constrained kinematic chain. If one of the links is held fixed and the movement of any other link to a new position will not cause each of the other links to move to a definite predictable position, then the system is an unconstrained kinematic chain.

2. A mechanism or linkage is a constrained kinematic chain, and is a mechanical device that has the purpose of transferring motion and/or force from a source to an output. A linkage consists of links (or bars), generally considered rigid, which are connected by joints, such as pin (or revolute) or prismatic joints, to form open or closed chains (or loops). Such kinematic chains, with at least one link fixed, become (1) mechanisms if at least two other links remain mobility, or (2) structures if no mobility remains. In other words, a mechanism permits relative motion between its "rigid links"; a structure does not. Since linkages make simple mechanisms and can be designed to perform complex tasks, such as nonlinear motion and force transmission, they will receive much attention in mechanism study.