Come and answer 60: Basics of Mechanical Knowledge – Double points to celebrate the 60th anniversary!

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This post was last edited by zx9527007 on 2009-9-17 00:09. Thank you all for your continued support of 【Dou Lai Da Da】. On the occasion of the 60th anniversary of the founding of the country, Dou Lai Da Da is offering double points for the 60th issue (participants will receive a reward of 1 charm or more as per the rules). True or False: 1. A pump is a machine that converts the mechanical energy of a prime mover into the energy of a liquid. Based on their working principles, pumps can be roughly classified into four categories: centrifugal pumps, reciprocating pumps, rotary pumps, and fluid-action pumps. 2. A machining process system consists of a machine tool, fixture, cutting tool, and turner. 3. Bearings (short for rolling bearings) are components and basic parts that are widely used in the machinery industry and subject to strict requirements; they are referred to as the joints of machinery. The wide range of applications determines the diversity and complexity of bearing types. The bearing manufacturing industry is a type of precision-based component manufacturing; its accuracy is measured in 0.001 millimeters, whereas the manufacturing tolerances for ordinary mechanical parts are usually only 0.1 mm. 4. Cast iron is an alloy composed of iron, carbon, silicon, and other elements. It contains less impurity elements such as sulfur and phosphorus than carbon steel. 5. Annealing is a heat treatment process in which a metal material is heated to an appropriate temperature, held there for a certain period of time, and then cooled slowly. Common annealing processes include: recrystallization annealing, stress-relief annealing, spheroidizing annealing, full annealing, etc. The purpose of annealing is mainly to reduce the hardness of metal materials and increase their plasticity, thereby facilitating machining or forming; it also helps to reduce residual stresses and improve the homogeneity of the structure and composition. 6. Polytetrafluoroethylene (PTFE): Due to the characteristics of its molecular structure, PTFE possesses many excellent properties, such as a wide operating temperature range, an extremely low coefficient of friction and self-lubricating properties, as well as a surface that does not allow adhesion ； It has good chemical stability and can resist chlorides, high-boiling-point solvents, aqua regia, as well as sodium hydroxide, hydrofluoric acid, and so on. The only things that can erode this plastic are molten alkali metals and fluorine under high temperature and pressure. Under load, creep occurs at 40°C, and it decomposes to produce toxic fumes above 343 degrees Celsius. 7. Pressure welding is a type of welding method in which the joint area between two components is heated to a plastic state or to a state of local surface melting, and pressure is applied to join the components together; this method is known as pressure welding, or simply press welding. 8. During the solidification and cooling process of castings, the stress arising from uneven contraction in different parts is called shrinkage stress. 9. Stop the centrifugal pump. First close the outlet valve, then turn off the motor, to prevent high-pressure liquid from flowing back and causing the impeller to rotate in the reverse direction, which could lead to accidents. 10. Mechanical technology is the foundation of mechatronics. The focus of mechanical technology lies in how to adapt to mechatronic technologies, by utilizing other advanced technologies to update concepts and bring about changes in structure, materials, and performance, in order to meet the requirements of reducing weight, minimizing size, improving precision, enhancing stiffness, and optimizing performance. In the manufacturing process of mechatronic systems, classical mechanical theories and techniques should be supplemented by computer-aided technologies, along with the use of artificial intelligence and expert systems, to develop a new generation of mechanical manufacturing technologies. Reference answers for issue 60: √×××√ ×√×√√. When replying, please choose hidden mode; the method for hiding is as follows: do not hide – no scoring will be given. For this issue, there will be no awards for answering all questions correctly. Additionally, due to limited time, responses will stop after this issue; those who wish to create questions are invited to post in the thread dedicated to question submissions.