How many questions can you answer for the interview of Mechanical Engineer?

Long working hours , It is inevitable to interview new people . Today, I would like to share some of the questions I used to ask when interviewing Mechanical Engineers . Let's compare each other , And whether these questions represent your ability and level .

What questions do mechanical engineers ask during an interview

First ask what you are good at , Then start with the following categories ： Transmission 、 structure 、 sheet metal 、 Shaft parts 、 Plate parts , Knowledge of material selection （ All kinds of steel 、 aluminum 、 Alloys and other metals 、 Plastic parts and other non-metallic materials ）, Heat treatment of parts , electroplate 、 Paint and other surface treatment . The transmission will be from several aspects ： Gear drive 、 Sprocket drive 、 Pulley 、 Synchronous pulley drive ;

such as ：

1、 An example is given to illustrate the application of dimension chain

Dimension chain ： In the process of part processing or machine assembly , A closed size group consisting of interconnected sizes arranged end to end in a certain order . The dimensions that make up the dimension chain are called the rings of the dimension chain . among , The dimension whose accuracy is finally indirectly guaranteed in the assembly or processing process is called a closed ring , The remaining dimensions are called constituent rings .

Using dimension chains , It can analyze and determine the dimensional accuracy of machine parts , Ensure machining accuracy and assembly accuracy .

2、 What kinds of ferrous materials are commonly used ？ What is high quality carbon steel ？

Ferrous metals usually refer to steel and cast iron ; Steel is divided into carbon steel （ Carbon steel for short ） And alloy steel . Carbon steel according to the quality of steel （ That is, steel contains harmful elements S、P The amount of ） It is divided into ordinary carbon steel 、 High quality carbon steel 、 High grade carbon steel class III . High quality carbon steel , In steel S、P Average content ≤0.040%.

3、 What are the common heat treatment methods ？（ Name at least three ） What is tempering ？

Anneal , Normalize , quench , Temper , Conditioning, etc .

Quenching and tempering ： High temperature tempering after quenching , High temperature tempering means tempering at 500-650℃ Tempering between .

4、 Closed gear （ soft 、 Hard tooth surface ） What is the main failure mode of transmission ？ What are the principles of design verification ？

The main failure form of closed soft tooth surface gear transmission is tooth surface fatigue pitting , The design calculation shall be carried out according to the tooth contact strength calculation formula , Check according to the tooth root bending fatigue strength calculation formula ;

The main failure form of closed hard tooth surface gear transmission is tooth root fatigue fracture , The design calculation shall be carried out according to the tooth root bending fatigue strength calculation formula , Check according to the tooth contact strength calculation formula .

5、 What is the function of the reducer ？

Change the speed and torque transmitted by the prime mover to the working machine . mechanical 、 Hydraulically coupled ; Fixed speed ratio 、 Adjustable speed ratio .

6、 One hydraulic cylinder , Strong impact from external load , What might be the most extreme case ？

De cylinder ; Blast steel ; deformation .

7、 The part is subjected to the combined load of bending and torsion , Which strength theory should be selected for checking ？

According to the third strength theory , Calculate bending stress .

8、 What is the development trend of modern machining ？

Manufacturing automation technology is developing in depth ： Precision 、 Integration 、 Flexibility 、 Networking 、 virtualization 、 Intelligent 、 Cleaning .

9、45 What is the carbon content of Steel No ？

45 The carbon content of No. steel is 0.45%

10、 What are the common casting defects ？

Mainly in ：1 sand holes 2 Sticky sand 3 Blowholes 4 Shrinkage cavity 、 Shrink loose 5 Sand inclusion 、 to scar 6 Crack, etc .

11、 What is the function of adding cutting fluid in the process of metal cutting ？

cooling 、 lubrication 、 Cleaning and rust prevention 4 A role .

12、 What is the difference between rolling bearings and plain bearings ？ For what occasion ？

The rolling bearing has high running accuracy 、 Some rolling bearings can bear both radial and axial loads 、 Less consumption of lubricating oil 、 Easy to install 、 The friction coefficient of rolling bearings is smaller than that of plain bearings 、 Standardization has been achieved 、 serialization 、 Generalization , It is very convenient to use and maintain 、 It can save the expensive non-ferrous metals used in the manufacture of sliding bearings ; However, foreign matters such as metal chips of rolling bearings are particularly sensitive , The service life of rolling bearings is shorter than that of plain bearings , The load bearing capacity of rolling bearings is much smaller than that of plain bearings with the same volume , therefore , The radial dimension of rolling bearings is large . therefore , It is required to have small radial size in the case of large load 、 Occasions requiring compact structure 〈 Such as crankshaft bearing of internal combustion engine 、 Rolling mill roll bearing ), Sliding bearings are often used ; The vibration and noise of rolling bearings are large , therefore , High precision is required 、 No vibration is allowed , Ordinary rolling bearings are not competent , Sliding bearings are often used .

13、 What is the difference between DC motor and AC motor ？

The DC motor has a stationary magnetic field , A conductor moves in a magnetic field ; AC motor is a rotating motion of magnetic field , And the conductor doesn't move .

The DC motor can change the speed of the meter by changing the input current , Good speed regulation performance . AC motor can adjust motor output speed by changing magnetic field change frequency .

When the DC motor with the same power starts at low speed, the torque is larger than that of the AC motor . Generally, the maintenance workload of DC motor is larger than that of AC motor .