Q&A on Practical Mechanical Knowledge 2

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1: When two conical tubes intersect obliquely, what method is used to find their line of intersection? Answer: Use the auxiliary spherical method. 2: What are the two conditions that must be satisfied when using the auxiliary spherical method to find the intersection line? Answer: It is satisfied if, first, the solids are in intersection, and second, their axes intersect and reflect the actual lengths. 3: When a straight line is parallel to a projection plane, what property does the projection of that line have? Answer: It is authentic. 4: What methods can be used to create an exploded view of a round-to-square transition joint? Answer: It can be drawn using the triangle method. 5: What is the main equipment used for punching, a press? Answer: Mainly crank presses and friction presses. 6: During blanking, into which three stages is the deformation process of the sheet metal divided? Answer: Elastic deformation stage ； Plastic deformation stage ； Shearing stage. 7: What is used by a hydraulic press to transmit motion and increase force? Answer: By utilizing the hydrostatic pressure of water and oil. 8: What kind of die is generally used for mass production of stamped parts? Answer: Use a punching die with guide pillars. 9: How to prevent deviation during the bending of materials? Answer: The pressure correction method is used. 10: What are the common methods for stripping the edge? Answer: There are universal tools for stripping the insulation ； Flange removal of the mold tire. 11: What are the main methods for edge finishing? Answer: There is thinning and drawing. 12: What is edge finishing? Answer: The task of bending a right-angled sheet into a convex curved edge. 13: What are the main equipment used for pressure die casting? Answer: It is a falling weight. 14: There are many methods of correction. According to the source and nature of the external force, into how many categories can they be divided? Answer: It can be divided into manual correction, mechanical correction, and flame correction. 15: What are the common equipment used for sheet metal correction? Answer: There are steel plate straightening machines, coil rolling machines, and presses. 16: What are the causes of deformation in steel structures? Answer: One type is deformation caused by external forces, and the other is deformation caused by internal stresses. 17: What are the main methods for eliminating residual welding stresses? Answer: There are overall high-temperature tempering and local high-temperature tempering, differential tension method, mechanical tension method, and vibration method. 18: For which materials is cold correction applicable? Answer: Due to the phenomenon of cold work hardening, it is only applicable to materials with good plasticity and minimal deformation. 19: What are the common welding methods used by sheet metal workers? Answer: There are arc welding, gas welding, resistance welding, and brazing. 20: What are the common connection methods used by sheet metal workers? Answer: Mortise and tenon joint, riveting, bolt connection, welding. 21: What is the key to achieving strong brazed joints? Answer: On the one hand, the melted filler metal can flow well into the joint gap; on the other hand, once it enters the joint gap, it can interact with the metal of the workpieces and then cool and crystallize, forming a strong joint. 22: What are the two welding methods used when welding with a DC arc welder? Which connection method results in higher heat being absorbed by the welded parts? Answer: There are two types: DC positive connection and DC reverse connection. The heat obtained in direct mode is high. 23: What is the purpose of beveling welded joints? Answer: To achieve a weld of a certain width and ensure full penetration. 24: What is clamping? Answer: It involves using external forces to fix the positioned part, so that it remains in its position during the processing. 25: What is an intersection line? Answer: The line formed by the intersection of a cutting plane and the surface of a solid is called the intersection line. 26: Within one lead, if the lead is denoted by S and the circumference by L, how is the length of a cylindrical helix calculated? Answer: Its length is: L*L+S*S. 27: What are the common methods of connecting metal structural components? Answer: There are riveting and welding. 28: What forces do ordinary rivets withstand? Answer: It withstands shear force and compressive force. 29: What are the four common types of weld joints? Answer: There are lap joints, butt joints, T-joints, and corner joints. 30: Depending on the thickness of the welded parts and the type of groove, according to GB985—88, what are the different types of butt joints? Answer: They are divided into I-groove, V-groove, double V-groove, single U-groove, and double U-groove. 31: What steel is the rivet used for cold riveting made of, and what treatment is it subjected to? Answer: It is made of low-carbon steel and undergoes annealing treatment. 32 What are the components that make up the entire welded joint of a welded part? Answer: It consists of weld metal, fusion zone, heat-affected zone, and base metal. 33: According to the discontinuity of the welded joint, into which two forms can it be divided? Answer: They are divided into continuous welds and intermittent welds. 34: What are the basic characteristics of mass production? Answer: The production volume of the products is high, and in most work sites, the same processing step for a particular part is carried out repeatedly over a long period of time. 35: What are the three principles of the manufacturing process? Answer: High quality, high yield, low consumption. 36: What is labor time consumption? Answer: It refers to the total amount of time workers spend on work during production. 37: What is process consumption? Answer: Losses that occur during the production process due to technical requirements. 38: What is a process specification? Answer: It is a process document that specifies the manufacturing processes and operating methods for products or components. 39: What is a process? Answer: It refers to the portion of a manufacturing process that is continuously carried out by one or a group of workers at a work site on one or several workpieces. 40: What is tank assembly? Answer: The process of assembling the formed lobes and their attachments into a spherical shape. 41: What is the assembly sequence of the spherical tank? Answer: First, install the equatorial band, and then expand from there toward both ends. This allows the gravity to be supported directly by the base of the columns, enabling the sphere to be positioned more easily and ensuring better stability. 42: What components make up the main structure of a vaulted oil storage tank? Answer: It consists of the tank bottom, cylindrical tank wall, spherical tank, and tank top. 43: How to assemble large, complex structural components? Answer: Divide the overall structure into several components; after assembling and welding these components together, carry out the final assembly. 44: Based on the number of structural layers of the housing, into which two categories can containers be divided? Answer: Single-layer containers, multi-layer containers. 45: What are the two common methods for unfolding ball flaps for drafting? Answer: There are the development diagram method and the central angle arc length method. 46: What are the two main aspects of inspecting the surface quality after gas cutting? Answer: There is flatness and surface roughness. 47: What are the three main inspection items for cylinders formed by roll bending? Answer: Tolerance of diameter, roundness of the cylinder body, and bend angle of the butt weld. 48: Into which two main categories can the inspection of welded joints be divided? Answer: Non-destructive testing and destructive testing. 49: Into which two categories can weld defects be classified based on their location within the weld? Large: internal defects and external defects. 50: What are the three common methods for testing the density of welds? Answer: Water pressure test, air pressure test, kerosene test. 51: What are the common non-destructive testing methods? Answer: Ultrasonic testing, radiographic testing, magnetic particle testing, leak detection testing, visual inspection. 52: What method is used in plasma arc cutting to compress the arc into a plasma arc? Answer: Mechanical compression, thermal compression, electromagnetic compression. 53: What tasks does the cutting torch of a CNC cutting machine perform after moving one step during cutting? Answer: Deviation judgment – the cutting torch performs deviation calculations and endpoint judgment. 54: What are the characteristics of crystal diodes? Answer: Forward conduction, reverse cut-off, reverse breakdown. 56: What are the common low-voltage electrical appliances? Answer: Fuses, thermal relays, switches, buttons, contactors. 57: What is the main function of a spring? Answer ； Buffering and shock absorption, controlling motion, storing energy, measuring force and torque. 58: What are the main components of a rolling bearing? Answer: Inner ring, outer ring, cage, rolling elements. 59: Based on the loads applied to them, into which categories can shafts be divided? Answer: Mandrel, light shaft, drive shaft. 60: What is the main function of a pin connection? Answer: Positioning and transmitting loads. 61: What are the three forms of threaded connections? Answer: Bolt connection, double-headed stud connection, screw connection. 62: What are the three basic components of a cam mechanism? Answer: Cam, driven component, and frame. 63: What are the four basic deformations of a workpiece during operation? Answer: Tensile deformation, compressive deformation, shear deformation, torsional deformation, bending deformation. 64: What are the common constraints in engineering? Answer: Flexible body constraints, smooth surface constraints, hinge constraints, fixed-end constraints. 65: What are the three elements of force? Answer: Size, direction, point of application. 66: What are the methods for density tests? Answer: Airtightness test, kerosene penetration test. 67: What are the two types of pressure tests? Answer: Water pressure test and air pressure test. 68: What are the common defects in cold-formed components? Answer: Dimensional errors, shape errors, surface defects. 69: What are the three types of inspection templates? Answer: Inner template, outer template, main template. 70: Into which two main categories are fixtures classified according to their purpose? Answer: Universal fixtures and assembly jigs. 71: What are the three elements of assembly? Answer: Support, positioning, clamping. 72: What are the general principles of mold design? Answer: On the premise of ensuring the quality of stamped parts, efforts are made to design molds that are easy to manufacture, have simple manufacturing processes, low costs, are convenient to use, and also possess a certain service life. 73: What issues should be considered when formulating process specifications? Answer: Technical advancement ； Economic rationality ； Good and safe working conditions. 74: What should be included in the inspection of cold-worked products? Answer: Composite inspection of raw materials ； Dimension inspection of raw materials, components, and products ； Material property inspection ； Non-destructive testing ； Pressure test inspection ； Density test examination. 75: What is non-destructive testing? Answer: A general term for various non-destructive methods used to detect internal defects in materials and products. 76 ； Briefly describe the points to note when performing force analysis on an object and drawing analysis diagrams. Answer: First, the object of study should be identified, and it is necessary to analyze which objects exert an influence on it ； When performing force analysis, primary forces should be analyzed first, followed by constraint forces ； The forces exerted by the object under study on other objects should not be drawn. 77: What are the main uses of gear trains? Answer: A larger gear ratio can be achieved ； A larger center distance can be achieved ； It can change speed ； Can change direction ； Movement can be synthesized or decomposed. 78: Why is the speed of the rotor in a three-phase asynchronous motor always lower than the synchronous speed? Answer: Since a relative motion must exist between the rotor of a three-phase asynchronous motor and the rotating magnetic field in order to maintain electromagnetic torque, the speed of its rotor is always lower than the synchronous speed. 79: What are the components of the time quota? Answer: There is a basic time, time for arranging work tasks, time for rest and meeting physiological needs, and a time to wrap things up. 80: What is the purpose of non-destructive testing in production? Answer: Used by manufacturers for quality control of products ； Used by product users for product acceptance ； Monitor and inspect the equipment in use. 81: What information is necessary when preparing a process specification? Answer: The complete set of working drawings for the product ； Quality standards for product inspection ； Product production schedule and production type ； Production status of rough products ； The production conditions of our factory ； An overview of the development of production technologies at home and abroad. 82: What is used as the shielding gas in TIG welding? Answer: Argon is used as the welding medium. 83: According to their nature, into which two categories can dimension references be divided? Answer: Design criteria and process criteria. 85: What are the two components of the cutting motion? Answer: It consists of the main motion and the feed motion. 86: What are the usual components of an electrical control circuit? Answer: Power circuit ； Control circuit ； Signal circuit ； Lighting circuit. 87: What is a basic hydraulic circuit? Answer: A typical circuit composed of hydraulic components that can perform a specific function. 88: What factors determine the diameter of the welding rod during welding? Answer: Depending on the thickness of the welded piece ； Joint type ； Weld position ； Selection of weld bead layers, etc. 89: What methods can be used for bending steel sections? Answer: Roll bending can be used ； bending ； Bending and other methods. 90: How many main components does a centrifugal ventilator consist of? Answer: It mainly consists of an organic shell, an air inlet, and an impeller. 91: What are the main causes of residual stress and deformation in steel structures after welding? Answer: Uneven heating and cooling. 92: What is the general shape of the intersection line? Answer: A closed planar figure. 93: What is the main purpose of studying the intersection of planar and solid surfaces? Answer: Find the intersection line. 94: What kind of surface is a sphere? Answer: A sphere is a typical non-developable surface. 95: What are the two types of helical surfaces? Answer: They are divided into right helical surfaces and oblique helical surfaces. 96: What is a helical surface? Answer: The surface formed by the helical motion of the busbar. 97: What does \"expand\" mean? Answer: The process of laying out the surface or a portion of a metal structural component on a flat surface, in accordance with its actual shape and size. 98: What is the purpose of drawing lofting diagrams? Answer: Determine the lines and dimensions required to draw the unfolded diagram. 99: What are the methods for drawing exploded views? Answer: There is the parallel lines method ； Radiation method ； Triangle method. 100: What are the methods for finding the actual length of a line segment? Answer: There is the rotation method ； Right triangle method ； The face-changing method and the branch method. 101: What is an intersection? Answer: A component composed of two or more basic geometric shapes. 102: What is an intersection line? Answer: The line of intersection between the surfaces of two solids in a solid of intersection. 103: What are the methods for finding the actual length of a curve? Answer: There are the face-replacement method and the unfolding method. 104: What is generally used as a method to unfold prisms and cylinders? Answer: The parallel lines method. 105: When a circular tube and a conical tube intersect horizontally, what is their intersection line? Answer: A closed spatial curve. 106: Do the projections of spatial curves in various views reflect their true length? Answer ； None reflect the actual length. 107: What does thickness treatment mainly include? Answer: Determine the neutral layer of the bent part and eliminate thickness interference. 108: What is related to the change in the position of the neutral layer? Answer: It is related to the ratio of the bending radius to the plate thickness. 109: How is the unfolded length calculated for a bent part with a rectangular cross-section? Answer: Calculate based on the surface layer of the sheet metal. 110: What problems must be solved before developing interpenetrating solids? Answer: Precisely determine the common lines of intersecting shapes. 111: What are the common shearing devices used by riveters? Answer: Gantry shearing machine ； Bevel shear machine ； Double-disc plate shear ； Punching shearing machine ； Combined punching and shearing machine. 112: What are the main equipment used for blanking? Answer: Crank press ； Friction press. 113: What are the transmission methods of pipe benders? Answer: There are mechanical transmission and hydraulic transmission. 114: Into which three categories can roll formers be divided based on the number and arrangement of their shaft rollers? Answer: Symmetric three-roller ； Asymmetric three-roll ； Four rolls. 115: Into which categories can punching dies be classified based on their structure? Answer: Simple modulus ； Mold with guide posts ； Composite mold. 116: What are the three stages in the bending deformation process of materials? Answer: Contact bending ； Correcting curvature ； Free bending. 117: What are the three stages in the deformation process of metal materials during blanking? Answer: Elastic deformation stage ； Plastic deformation stage ； Shearing stage. 118: What are the common methods used to reduce the springback of bent parts? Answer: Modified mold method and pressure correction method. 119: What is the purpose of using a flange ring during drawing? Answer: To prevent wrinkling at the edges. 120: On which die is the flanging ring usually installed? Answer: It is on the punch. 121: What is the relationship between the drawing coefficient and material plasticity? Answer: The better the plasticity, the smaller the drawing coefficient can be. 122: What is the purpose of expanding a template? Answer: Used for marking materials ； Manufacture separation molds ； Manufacture milling templates. 123: What are the two main methods for trimming edges? Answer: Thinning and drawing. 124: What is pulling the edge? Answer: The edges of the sheet metal are shaped into curves using corner bending and edge trimming methods. 125: What is gapping? Large: A manufacturing method that involves folding and pressing the edges of two sheet pieces together. 126: To which category of measuring tools do templates belong for workpieces? Answer: Rigid measuring tools for size and shape. 127: What are the different shapes that tooth gaps can take? Answer: Vertical double interlock ； corner joint ； Vertical single-joint seam ； Horizontal flat joint. 128: What types of workpieces generally require edge trimming? Answer: Concave curve. 129: What are the two methods for stripping the edge? Answer: Use a tool to pull the edge off ； Pull the edge using a mold tire. 130 Which workpieces can be directly curved on a mold core? Answer: Workpieces that are large in size and shallow in depth. 131: What are the applications of rubber molding? Answer ； drawling ； expansion jointing ； Drop hammer forming. 132: Into which categories can rubber molding dies be classified based on their structure? Answer: One-time molding ； secondary molding ； Mold with side pressure blocks. 133: Into which categories can pressure die molds be classified according to their use? Answer: Molding die ； Transition mold ； Orthotic mold. 134: Into which processes can the deformation of material during drawing be divided? Answer: Material bending ； The material is deformed by drawing ； Additional pull. 135: What are the characteristics of the spinning method? Answer: Hollow rotors of various shapes can be manufactured. 136: What is another name for strong spinning? Answer ； Thinning spin forming. 137: What are the characteristics of rubber molding? Answer: It can simplify the installation and adjustment of the mold. 138: What factors determine the selection of spinning die materials? Answer: It depends on the production volume of the workpieces ； Size ； Shape. 139: What is the purpose of clicking the hammer? Answer: To perform local blanking and wrinkle removal on sheet metal or workpieces. 140: What are the two aspects involved in the drawing deformation process? 140: What are the two aspects involved in the drawing deformation process? Answer: Degree of mold adhesion ； Degree of deformation allowed. 141: How many types can correction methods be divided into based on the source and nature of the external force? Large: Divided into flame correction and mechanical correction. 142: How many types are there of deformation in metallic materials? Answer: Elastic deformation and plastic deformation. 143: What type of deformation is correction for metal materials? Answer: Yes, to plastic deformation. 144: How many types are there for heating correction? Answer: Full heating correction and partial heating correction. 145: What are the common types of corrective devices? Answer: Steel plate straightening machine ； Rolling machine ； Press. 146: What are the different shapes of the heating zone in flame correction? Answer: Spot heating ； linear heating ； Triangle heating. 147: What determines the effectiveness of local heating correction? Answer: It depends on the heating location and the shape of the heating area. 148: What is the typical heating temperature for flame correction? Answer: 600–800 degrees Celsius. 149: How should the correction area be selected when eliminating stress deformation? Answer: Choose a location with stress concentration. 150: How to improve the correction effect when using flame correction? Answer: The two ends of the workpiece are often supported to enhance the correction effect by utilizing the workpiece’s own weight. 151: What are the main causes of workpiece deformation? Answer: It is caused by external forces or internal stresses in the workpiece. 152: What are the main types of deformation in box girders? Answer: Twisting and warping. 153: What are the methods for correcting residual deformation in steel structural members? Answer: Mechanical correction method and flame correction method. 154: What are the methods to prevent and reduce welding deformation? Answer: A reasonable welding sequence is adopted ； Rigid fixation method ； Inverse deformation method ； Hammer welding method. 155: What are the common connection methods used by sheet metal workers? Answer: Tenon joint ； riveting ； Bolt connection ； Welding. 156: What is another name for butt joint? Answer: Tenon joint or mortise and tenon joint. 157: What are the two parts that make up a rivet? Answer: The nail head and the nail shank. 158: What are the two types of rivets? Answer: There are hollow and solid ones. 159: What type of rivet is commonly used by sheet metal workers? Answer: Solid rivet. 160: What materials are suitable for corner butt joint connections? Answer: Plates with a thickness of 1–1.5 millimeters. 161: What determines the arrangement of rivets? Answer: It is determined based on the strength of the connecting elements. 162: What are the adverse effects of riveting defects? Answer: It will weaken the riveting strength. 163: What types of components are composite angle joints generally used to connect? Answer ； Used for connecting square tubes. 164: What determines the diameter of the rivets and the center distance between them during riveting? Answer: Based on the stress conditions of the structural components and the required strength. 165: Why should excessive hammering be avoided when performing manual cold riveting? Answer: Excessive hammering can cause cold working hardening in the material, leading to cracks in the nail head. 167: What is positioning? Answer: Determine the position of a part in space or the relative positions between parts. 168: What is measurement? Answer: It refers to a series of technical measurements taken during the assembly process to determine the relative positions of the parts and their respective dimensions. 169: How to determine the position of a part in space? Answer: To constrain its six degrees of freedom in space. 170: How many degrees of freedom does any spatial rigid body have when it is not positioned? Answer: Six. 171: What is relative parallelism? Answer: It refers to the parallelism of the line or surface being measured on the part with respect to the measurement reference line or surface. 172: What is relative perpendicularity? Answer: It refers to the perpendicularity of the line or surface being measured on a part with respect to the measurement reference line or surface. 173: What is an assembly tool? Answer: A general term for tools used in assembly for the positioning, alignment, measurement of components, and related auxiliary tasks. 174: What is the main purpose of a level? Answer: Measure the inclination and height of the workpiece. 175: What components does a level consist of? Answer: Level, telescope, base. 176: What is a mounting fixture? Answer: A general term for tools used in assembly to apply external force to components in order to achieve precise positioning. 177: What are the commonly used lifting tools in assembly? Answer: Steel wire ropes, chains, hand chain hoists, specialized lifting gear, etc. 178: Why do the parts of metal structural products need to be selected or adjusted during assembly? Answer: Because of its low precision and poor interchangeability. 179: How many categories can the assembly methods of metal structures be divided into, based on the position of the structure during assembly? Answer: Formal attire ； Inversion ； Pajamas. 180: What is the common method used for assembling angle steel frames? Answer: Ground sample assembly method. 181: What are the two parts that make up a T-beam? Answer: Wing plates and web plates. 183: What methods are commonly used to assemble roof trusses? Answer: The ground sample assembly method and the profiling assembly method are combined. 184: What are the common methods for calculating the dimensions of blank materials for drawing? Answer: The equal area method. 185: What is the function of the drawing die clearance? Answer: Reduce friction between the material and the die. 186: Into which categories can blanking dies be classified based on the combination of processes? Answer: Simple blanking die ； Continuous blanking die ； Compound punching die. 187: What role do buffer parts play in impact wear? Answer: Material pressing function ； Unloading and ejecting functions. 188: How many parts does a stamping die usually consist of? Answer: Positioning section ； Material positioning section ； Accumulation section ； Mold base. 189: What criteria should be used to choose a mold? Answer: Based on the production batch size of stamped parts ； Size ； Precision requirements ； Complexity of shape and production conditions, etc. 190: What are the requirements for the vulnerable parts of the mold? Answer: It should be easy to disassemble and assemble during maintenance. 191: The top of the sphere unfolds into a circular disk; how is its diameter determined? Answer: Its diameter is a circle with the arc length as its radius. 192: How is a helical surface unrolled? Answer: A helical surface is a non-developable surface, and it can only be developed using approximate methods. 193: What is the shape of the intersection formed when a plane intersects a sphere? Answer: It is a circle. 194: What are the basic properties of intersection lines? Answer: The intersection line is the common line of the basic shape and the cutting plane. 195: Please give a few examples of non-developable surfaces. Answer: Sphere ； paraboloid ； Hypersurfaces, etc. 196: When the cutting plane intersects the cylinder axis at an angle, what is the shape of the intersection line? Answer: It is an ellipse. 197: What is the shape of the intersection when the cutting plane is parallel to the axis of the cone? Answer: It is a hyperbola. 198: What is the junction line where a square tube intersects a square cone tube? Answer: It is a spatial polyline. 199: What is an intersection line? Answer: The intersection line of the cutting plane and the surface of the solid. 1: Into which categories are fixtures classified according to their purpose? Answer: (1) General fixtures (2) Assembly jigs. II: What are the categories of inspection templates? Answer: (1) Inner template, (2) Outer template, (3) Three-dimensional template. III: What are the common defects in cold-formed components? Answer: (1) Dimensional errors (2) Shape errors (3) Surface defects. IV: What are the types of pressure tests? Answer: (1) Hydrostatic test; (2) Pneumatic test. V: What are the common non-destructive testing methods? Answer: (1) Radiographic testing (2) Ultrasonic testing (3) Magnetic particle testing (4) Penetrant testing. 6: What are the three elements of force? Answer: (1) The magnitude of the force; (2) The direction of the force; (3) The point of application of the force. 7: What rule must be followed when adding two forces whose lines of action are not on the same straight line? Answer: The triangle rule. 8: What are the common constraints in engineering? Answer: (1) Flexible constraint, (2) Smooth surface constraint, (3) Hinge constraint, (4) Fixed end constraint. 9: What are the four basic types of deformation of components in engineering? Answer: (1) Tensile deformation, (2) Shear deformation, (3) Torsional deformation, (4) Bending deformation. 10: What is the formula for estimating the transmission ratio in belt drives? Answer: i = n/N = D/d. 11: What are the main types of threaded connections? Answer: (1) Bolt connection (2) Double-headed stud connection (3) Screw connection. Twelve: What are the main functions of pin connections? Answer: (1) Positioning (2) Transmitting loads. Thirteen: What are the main components of a rolling bearing? Answer: (1) Inner ring (2) Outer ring (3) Retainer (4) Rolling elements. 14: What are the characteristics of a crystal diode? Answer: (1) Forward conduction (2) Reverse cutoff (3) Reverse breakdown. 15: What are the four tasks that the control unit of a CNC gas cutting machine performs after each movement of the cutting torch? Answer: (1) Deviation detection, (2) Torch feeding, (3) Deviation calculation, (4) End-point detection. 16: How is an arc compressed into a plasma arc in plasma arc cutting? Answer: (1) Mechanical compression (2) Thermal compression (3) Electromagnetic compression. 17: What is the actual shape of the cross-section when a plane parallel to the axis of the cone cuts through the cone? Answer: Hyperbola. 18: What are the common internal defects in welds? Answer: (1) Pores (2) Slag inclusions. 19: What are the common surface defects in welds? Answer: (1) Lack of fusion; (2) Undercutting. 20: What type of transmission mechanism can ensure a stable instantaneous gear ratio? Answer: Gear transmission. 41: When a cylinder is intersected by a plane, and the intersection line consists of two parallel straight lines, what is the relationship between the intersecting plane and the cylinder’s generatrices? Answer: Parallel. 42: What types of workpieces are electric slag welding generally used for? Answer: Thick-walled workpieces. 43: What methods are used to check for cracks on the surface of workpieces? Answer: Magnetic particle testing. 44: What is the term used to refer to the choice of a reference plane upon which the installation surfaces of the assembled metal components are supported? Answer: Support 45: What methods are commonly used in the manufacture of large and complex structural components nowadays? Answer: Component assembly method. 46: What are the two basic conditions required for assembly operations? Answer: 1: Positioning, 2: Benchmark. 47: What heat treatment should be used to eliminate the internal stresses generated during welding? Answer: Annealing. 48: What should be included in the inspection of cold-worked products? Answer: 1: Quality inspection and verification of raw materials; 2: Inspection of the geometric dimensions of raw material components and products; 3: Testing of material properties; 4: Non-destructive testing; 5: Pressure test; 6: Integrity test. 49: What are the original documents that must be available when preparing process specifications? Answer: 1: The complete set of working drawings for the product; 2: The quality standards for product inspection; 3: The production schedule and type of the product; 4: The production status of the raw materials; 5: The production conditions of the factory, as well as an overview of the development of production technologies at home and abroad. 50: What line is used to represent the break in a local view? Answer: Indicated with a wavy line. 51: Under what conditions do metal materials achieve high forming precision for stamped parts? Answer: Low shear strength, good plasticity, uniform microstructure, and low notch sensitivity. 52: What are the three surfaces formed during excessive cutting? Answer: They are respectively: (1) the surface to be processed. (2) Machined surface, (3) Unmachined surface. 53: How many parts does the working part of a twist drill consist of? Answer: It consists of a guiding part and a cutting part. 54: What are the main causes of pipe cracking? Answer: The clamping force is too high. 55: What is the main reason why the cross-section at the elbow becomes elliptical when pipes are mechanically cold-formed? Answer: Insufficient counterbending amount. 56: When using a steel plate roller, how is the cutting length calculated? Answer: Calculate based on the neutral layer of the steel plate. 57: What is expansion joining? Answer: Expansion joining involves using an expansion tool to cause plastic deformation in the tube, while the wall of the tube sheet undergoes elastic deformation. The rebound of the tube sheet wall exerts a radial pressure on the tube, thereby achieving a permanent connection. 58: For welding alloy steel, what measures should be taken to prevent welding cracks? Answer: The workpiece should be heated to a certain temperature before welding. 59: Under what circumstances can assembled measuring tools be used? Answer: Regular testing must be carried out to ensure accuracy. Tools, fixtures, and molds should be inspected before use, and only after passing the inspection can they be utilized. 60: What is the main reason for the conical defects that occur in workpieces during sheet metal rolling? Answer: It is caused by the upper shaft and side shaft of the coiler not being parallel. 61: What is an intersection line? Answer: The line of intersection between the surfaces of two or more intersecting solids. 62: Under what circumstances in actual operation should an estimated value be used for the machining allowance of the workpiece? Answer: For single pieces and small-batch production, the estimation method is used. 63: Under normal circumstances, the strength of riveting is proportional to what aspect of the rivet? Answer: It is proportional to the diameter and quantity of rivets. 64: What are the general categories of structural types for expansion joints? Answer: Generally, there are methods such as optical hole expansion welding, flanging expansion welding, grooving expansion welding, and expansion welding combined with end face welding. 65: What factors should determine the magnitude of the welding current? Answer: It is determined by factors such as the type of electrode, electrode diameter, thickness of the workpiece, joint configuration, position of the weld, and number of weld passes. 66: What should be considered during assembly for welded parts with high technical requirements? Answer: Assembly clearance, weld shrinkage. 67: What determines the diameter of the welding rod during welding? Answer: Weldment thickness, joint type, weld position, number of weld passes. 68: Into which two main categories are welding machines used for manual arc welding divided? Answer: There are two main categories: AC arc welders and DC arc welders. 69: What are the common defects in bent pipes? Answer: Yes: bulges, flattening, folding, oval shape, cracks, etc. 70: What are the common shape defects that occur when sheet metal is rolled into circles? Answer: Conical, drum-shaped, waisted, twisted. 71: What methods can be used to bend steel sections? Answer: Roll bending, press bending, draw bending. 72: What are the methods for bending pipes? Answer: Compression (bending under pressure), rolling bending, reverse bending, extrusion bending. 73: Into which categories are welding electrodes classified based on the characteristics of the slag formed after the melting of their flux? Answer: They are divided into two main categories: acidic electrodes and basic electrodes. 74: How many orientation references does a plane figure have? Answer: There are references in both horizontal and vertical directions. 75: Into which parts is a basic view divided? Answer: They are divided into the front view, back view, top view, bottom view, left view, and right view. 76: According to their nature, into which two categories can dimension references be divided? Answer: It can be divided into two categories: design criteria and process criteria. 77: How many ways can cold-formed structural diagrams be represented? Answer: It can be divided into three types: structural schematic diagrams, simple structural diagrams, and complex structural diagrams. 78: What determines the weldability of metal materials? Answer: It is determined by physicochemical weldability and process weldability. 79: What movements does the cutting motion consist of? Answer: It consists of the main motion and the feed motion. 80: What are the cutting elements when cutting metal? Answer: Yes: cutting speed, feed rate, depth of cut. 81: What metal material is used to make twist drills? Answer: It is composed of high-speed steel. 82: What are the two types of machining allowances? Answer: There are two types: process margin and total margin. 83: What are the usual components of an electrical control circuit? Answer: It consists of lighting circuits such as the power circuit, control circuit, and signal circuit. 84: What is a hydraulic circuit? Answer: A typical circuit composed of hydraulic components that can perform a specific function. 85: What are the aspects of mechanical processing accuracy for parts? Answer: There is dimensional accuracy, shape accuracy, and positional accuracy. 86: What are low-voltage electrical appliances? Answer: Electrical appliances that operate at an AC voltage of 1000V or less are low-voltage electrical appliances. 87: What is sheet metal rolling? Answer: It is a plastic deformation process in which the sheet metal is continuously bent at points using a roll bending machine. 88: What are the main causes of residual stress and deformation in steel structures after welding? Answer: Steel structural components experience local heating and cooling; the thermal expansion and contraction of the metal in the high-temperature areas are hindered by the surrounding cold metal. 89: What is the production technology preparation process? Answer: All the production and technical preparation work carried out before a product goes into production. 90: What are the methods for roll bending steel plates with a conical surface? Answer: There are methods such as the small-gap deceleration method, dual-speed roller winding method, rotating feeding method, rectangular feeding method, and segmented winding method. 91: What are the defects in the roll bending of steel plate columns? Answer: Yes, there are (1) dimensional defects, (2) surface dents, and (3) cracking. 92: What are the methods for pre-bending sheet metal? Answer: (1) Pre-bending by manual hammering; (2) Pre-bending using press machinery molds or universal molds; (3) Pre-bending with templates or shims used on roll formers, as well as wedge-shaped shims. 93: What are the measures to improve the small bending radius of machine bends and thin-walled steel pipe elbows? Answer: Yes. (1) Use curved chutes or rollers; (2) Adopt the method of adding padding to the inner wall; (3) Use a pipe bender with a low speed for curves; (4) Use a push-bending pipe bender. 94: Briefly explain the principle of flame correction? Answer: Flame correction involves using a flame to heat the bulged parts of a deformed component; this heating causes the metal in those bulged areas to expand, but this expansion is restricted, resulting in compressive stresses. When these compressive stresses exceed the yield point of the heated metal, the metal fibers in those bulged areas undergo plastic deformation, thereby achieving the purpose of correction. 95: What are the three views? Answer: The three basic views, namely the front view, top view, and left view, are commonly referred to as the three-view projection. 96: What are the three essential elements for a riveter to carry out assembly? Answer: It is for support, positioning, and clamping. 97: What is correction? Answer: Correction involves inducing plastic deformation in the steel under external forces, so that the fibers that are contracted locally are stretched, while those that are stretched are shortened. This process ensures that the fiber lengths in the metal part are uniform, thereby eliminating defects such as surface irregularities, bending, twisting, and wavy deformations, and achieving the correct shape. 98: What is the principle behind the unfolding of triangles? Answer: The principle is to divide the surface of the part into one or multiple groups of triangles, then determine the actual length of each side of these triangles, and draw their shapes sequentially on a plane to obtain the development diagram.