1、兰州交通大学毕业设计（论文） 1 Mechanical Design Abstract A machine is a combination of mechanisms and other components which transforms, transmits. Examples are engines, turbines, vehicles, hoists, printing presses, washing machines, and movie cameras. Many of the principles and methods of design that apply to m
2、achines also apply to manufactured articles that are not true machines. The term mechanical design is used in a broader sense than machine design to include their design. the motion and structural aspects and the provisions for retention and enclosure are considerations in mechanical design. Applica
3、tions occur in the field of mechanical engineering, and in other engineering fields as well, all of which require mechanical devices, such as switches, cams, valves, vessels, and mixers. Keywords Design Process Design Rules Mechine Design The Design Process Designing starts with a need real.Existing
4、 apparatus may need improvements in durability, efficiency, weight, speed, or cost. New apparatus may be needed to perform a function previously done by men, such as computation, assembly, or servicing. With the objective wholly or partly. In the design preliminary stage, should allow to design the
5、personnel fully to display the creativity, not each kind of restraint. Even if has had many impractical ideas, also can in the design early time, namely in front of the plan blueprint is corrected. Only then, only then does not send to stops up the innovation the mentality. Usually, must propose sev
6、eral sets of design proposals, then perform the comparison. Has the possibility very much in the plan which finally designated, has used certain not in plan some ideas which accepts. When the general shape and a few dimensions of the several components become apparent, analysis can begin in earnest.
7、 The analysis will have as its objective satisfactory or superior performance, plus safety and durability with minimum weight, and a competitive cost. Optimum proportions and dimensions will be sought for each critically loaded section, together with a balance between the strengths of the several co
8、mponents. Materials and their treatment will be chosen. These important objectives can be attained only by analysis based upon the principles of mechanics, such as those of static for reaction forces and for the optimum utilization of friction； of dynamics for inertia, acceleration, and energy； of e
9、lasticity 兰州交通大学毕业设计（论文） 2 and strength of materials for stress and deflection； of physical behavior of materials； and of fluid mechanics for lubrication and hydrodynamic drives. The analyses may be made by the same engineer who conceived the arrangement of mechanisms, or, in a large company, they m
10、ay be made by a separate analysis division or research group. Design is a reiterative and cooperative process, whether done formally or informally, and the analyst can contribute to phases other than his own. Product design requires much research and development. Many Concepts of an idea must be stu
11、died, tried, and then either used or discarded. Although the content of each engineering problem is unique, the designers follow the similar process to solve the problems. Product liability suits designers and forced in material selection, using the best program. In the process of material, the most
12、 common problems for five (a) dont understand or not use about the latest application materials to the best information, (b) failed to foresee and consider the reasonable use material may (such as possible, designers should further forecast and consider due to improper use products. In recent years,
13、 many products liability in litigation, the use of products and hurt the plaintiff accused manufacturer, and won the decision), (c) of the materials used all or some of the data, data, especially when the uncertainty long-term performance data is so, (d) quality control method is not suitable and un
14、proven, (e) by some completely incompetent persons choose materials. Through to the above five questions analysis, may obtain these questions is does not have the sufficient reason existence the conclusion. May for avoid these questions to these questions research analyses the appearance indicating
15、the direction. Although uses the best choice of material method not to be able to avoid having the product responsibility lawsuit, designs the personnel and the industry carries on the choice of material according to the suitable procedure, may greatly reduce the lawsuit the quantity. May see from t
16、he above discussion, the choice material people should to the material nature, the characteristic and the processing method have comprehensive and the basic understanding. Finally, a design based upon function, and a prototype may be built. If its tests are satisfactory, the initial design will unde
17、rgo certain modifications that enable it to be manufactured in quantity at a lower cost. During subsequent years of manufacture and service, 兰州交通大学毕业设计（论文） 3 the design is likely to undergo changes as new ideas are conceived or as further analyses based upon tests and experience indicate alterations
18、. Sales appeal. Some Rules for Design In this section it is suggested that, applied with a creative attitude, analyses can lead to important improvements and to the conception and perfection of alternate, perhaps more functional, economical,and durable products. To stimulate creative thought, the fo
19、llowing rules are suggested for the designer and analyst. The first six rules are particularly applicable for the analyst. 1. A creative use of need of physical properties and control process. 2. Recognize functional loads and their significance. 3. Anticipate unintentional loads. 4. Devise more fav
20、orable loading conditions. 5. Provide for favorable stress distribution and stiffness with minimum weight. 6. Use basic equations to proportion and optimize dimensions. 7. Choose materials for a combination of properties. 8. Select carefully, stock and integral components. 9. Modify a functional des
21、ign to fit the manufacturing process and reduce cost. 10. Provide for accurate location and noninterference of parts in assembly. Machinery design covers the following contents. 1. Provides an introduction to the design process , problem formulation ,safety factors. 2. Reviews the material propertie
22、s and static and dynamic loading analysis ,Including beam , vibration and impact loading. 3. Reviews the fundamentals of stress and defection analysis. 4. Introduces fatigue-failure theory with the emphasis on stress-life approaches to high-cycle fatigue design, which is commonly used in the design of rotation machinery. 5. Discusses thoroughly the phenomena of wear mechanisms, surface contact stresses ,and surface fatigue. 6. Investigates shaft design using the fatigue-analysis techniques. 7. Discusses fluid-film and rolling-element bearing theory and application
