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Mechanical common sense more than 100 questions (Part 2)

101. What kinds of cast iron can be divided into

answer: white cast iron, gray cast iron, ductile iron, alloy cast iron, parallel and then stretch; What are the types of malleable cast iron

102 and aluminum alloy

answer: it can be divided into deformed aluminum alloy and cast aluminum alloy

103. What are the types of copper alloys

answer: it can be divided into bronze, red copper and brass

104. What are the functions of welding rods

answer: it has the function of conducting current and providing filler metal to the molten pool

105. What are the forces on the droplet

answer: there are gravity, surface tension, electromagnetic compression force, spot pressure, plasma flow force, arc gas blowing force

106. What are the defects that are easy to occur when gas welding cast iron

answer: mainly white spots, cracks, pores, refractory oxides, etc

107. What is weldability

answer: it refers to the adaptability of metal materials to welding processing, mainly refers to the difficulty of obtaining high-quality welded joints under certain welding process conditions

108. What are the main reasons for stress and deformation during welding

answer: uneven heating and cooling

109. What are the common types of steels with special properties

answer: there are stainless steel, heat-resistant steel and corrosion-resistant steel

110. What is screw connection

answer: it is a removable fixed connection made of threaded parts

111. What are the common forms of threaded connection

answer: there are bolt connection, stud connection, and screw connection

112. How many kinds of washers are there? What is its function

answer: it can be divided into general gasket, anti loosening gasket and special purpose gasket. The function is to increase the support surface, cover the larger holes, and prevent damage to the surface of parts and leveling

113. What are the washers to prevent loosening

answer: there are spring washers, round nut retaining washers, single lug retaining washers, and double lug retaining washers

114. What is the equipment work before gas cutting

answer: with site preparation, check the cutting oxygen flow line (i.e. wind line)

115. What is the preheating flame energy rate

answer: it is the unit expressed by the hourly consumption of combustible gas

116. How many preheating flames can be divided? Answer: neutral flame, carbonization flame, oxidation flame

117. What is tempering

answer: when cutting, the mouth is blocked due to overheating or splashing of iron oxide slag, or acetylene supply is not timely, and the mouth produces explosion and tempering

118. What method should be taken in case of tempering

answer: the valves for preheating oxygen and cutting oxygen should be closed quickly to prevent oxygen from flowing back into the acetylene pipe to extinguish the tempering

119. What kinds of drills are there? A: drill bits include fried dough twist drill, flat drill, center drill, etc

120. What is the role of the shank of the drill

answer: torque and axial force required for clamping and transmitting drilling

for the wall thickness of formed parts 121. What is the role of the guide part in the drill

answer: it can maintain the straight drilling direction of the drill bit during the cutting process. At the same time, it has the function of polishing the hole wall and is also the backup part of the cutting part

122. What adverse phenomena will appear when the hole is about to be drilled

answer: when the drill bit just penetrates the workpiece, the axial resistance suddenly decreases. Due to the sudden recovery of the gap and elastic deformation of the drilling machine, the drill bit will automatically cut in with a large feed, resulting in the breaking of the drill bit or the reduction of drilling quality

123. What is grinding

answer: it is the method of machining the workpiece surface with grinding wheel

124. What are the anti loosening measures for bolted connections

answer: increase friction; Mechanical locking

125. What are the methods of mechanical locking

answer: cotter pin; Retaining washer; Lock washer; Wire in series

126. What is welding arc

answer: strong and lasting discharge occurs in the gas medium between the two electrodes

127. What are the three directions of electrode movement

3. Frequent use for a long time may reduce or deteriorate the oil quantity

answer: move towards the molten pool; Move along the welding direction; Swing sideways

128. How is the internal stress in steel structural members produced

answer: the welding process is an uneven heating and cooling process for the riveted structure, which is the main reason for the internal stress in the riveted structure. In addition, each part in the steel structure may have residual stresses in its blank state or after being processed into parts. After being assembled and welded into a whole, these residual stresses may be integrated into the new internal stress of the component

129. Why should some steel structures be stress relieved after welding

answer: some steel structures have no obvious welding deformation due to their good rigidity after welding, but the welding stress is quite large. After the steel structure is used for a period of time, it may be released for some reason to cause deformation and damage. Therefore, for some important steel structures, such as high-pressure vessels, vessels of dangerous media, boilers, etc., various methods are used for stress relief treatment after welding, in order to prevent the internal stress in the steel structure from harming the members

130. What are the factors that affect the welding deformation of steel structures

answer: there are two factors affecting the welding deformation of steel structures: design and process. The design aspect refers to the rationality of the structural design, the position of the weld, the form of the welding groove, etc. In terms of process, it refers to the reasonable welding process specification, assembly and welding sequence, the adoption of various anti deformation and anti deformation methods, as well as the stress relief measures taken

131. In multi-layer welding, the shrinkage caused by the first layer is the largest, and the shrinkage of the second layer is about dozens of percent of that of the first layer? The third floor is about tens of percent of the first floor

answer: (1) twentypercent (2) five to ten percent

132. What is the purpose of beveling weldments

answer: obtain a certain width of weld and ensure penetration

133. What are the parts of the whole welded joint of the weldment

answer: it is composed of weld metal, fusion zone, heat affected zone and matrix

134. What are the two types of weld defects according to their positions in the weld

answer: internal defects and external defects

135. Which three methods are usually used to inspect the tightness of welds

answer: hydraulic test, pneumatic test, kerosene test

136. What are the commonly used nondestructive testing methods

answer: ultrasonic flaw detection, radiographic flaw detection, magnetic particle flaw detection, leakage flaw detection, visual flaw detection

137. What are the characteristics of crystal diodes

answer: forward conduction, reverse cut-off, reverse breakdown

138. What are the commonly used low-voltage electrical appliances

answer: fuses, thermal relays, switches, buttons, contactors

139. What is the main function of the spring

answer; Buffer and shock absorption, control movement, store energy, measure force and torque

140. What are the main parts of rolling bearings

answer: inner ring, outer ring, cage, rolling element

141. According to the different loads on the shafts, which types of shafts can be divided

answer: spindle, light shaft, transmission shaft

142. What is the main function of pin connection

answer: locate and transfer the load

143. What are the three forms of threaded connection

answer: bolt connection, double stud connection, screw connection

144. Why is the rotor speed of three-phase asynchronous motor always lower than the synchronous speed

answer: since the electromagnetic torque can be maintained only by maintaining relative motion between the rotor and rotating magnetic field of three-phase asynchronous motor, the rotor speed is always lower than the synchronous speed

145. What is argon arc welding with as shielding gas

answer: argon is used as the welding medium

146. Which parts does the electrical control circuit usually consist of

answer: power circuit; Control circuit; Signal circuit; Lighting circuit

147. How many main parts does the centrifugal fan consist of

answer: it is mainly composed of casing, air inlet and impeller

148. What are the main reasons for the residual stress and deformation of steel structure after welding

answer: uneven heating and cooling

149. What are the common weld internal defects

answer: (1) pores (2) slag inclusion

after the air is exhausted

150, what are the common weld surface defects

answer: (1) incomplete fusion (2) undercut

151. What kinds of three-phase asynchronous motors can be divided according to rotor structure

answer: wire wound, cage type

how much is 152 and 1kgf

answer: 9.8N

153. What test should be done to check the tightness of containers containing inflammables and explosives

answer: air tightness test

154. How many parts of magnetic pump oil

answer: motor, impeller, seal, rotor, shell, etc

155. What are the main types of equipment in the extraction plant

answer: container equipment, extraction equipment, concentration equipment, separation equipment, conveying equipment, drying equipment, heat exchange equipment, special equipment (pressure vessels, hoists), vacuum equipment, air compressors, etc

156. What kind of cable should be used in the explosion-proof area for the lines of mobile or portable electrical equipment

answer: rubber sheathed cable,

157. In the whole process system, what equipment should be maintained

answer: 1. Public system equipment: boilers, circulating water equipment, vacuum equipment, air compressors, hoists; 2. Process equipment: material conveying equipment, extraction equipment, separation equipment, concentration equipment, heat exchange equipment, etc.

158. What safety precautions should be paid attention to in the maintenance process

answer: 1. Try to avoid maintenance in the explosion-proof area; 2. In the explosion-proof area, attention should be paid to avoid sparks caused by violent collision between tools and metal parts; 3. The power distribution shall be turned off during the maintenance of electromechanical equipment; 4. Wear safety belts when working at heights; 5. After the rotating equipment is assembled, it should be manually cranked, and the commissioning can be carried out without collision and friction; 6. Pay attention to whether there is pressure or material in the equipment or pipeline before maintenance; 7. Do not use electric tools at will in the explosion-proof area; 8. The electrical circuit shall be tested after maintenance

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