Causes of abnormal spring fracture

Spring is one of the important basic parts in mechanical products. There are many types of it. According to the shape, it is divided into: spiral spring, plate (leaf) spring, disc spring, ring spring, flat (truncated cone) spiral spring, etc.; according to the bearing characteristics: compression, tension, torsion spring, etc. . The stresses the spring bears mainly include: bending stress, torsion stress, tension and compression stress and compound stress. The main failure modes of springs are: fracture, deformation, relaxation, and wear. The main analysis is fracture and deformation (relaxation).

1. Brittle fracture: most of the spring fractures are brittle fractures. Only when the working temperature is high, plastic fracture may occur. In engineering, fatigue fracture, stress corrosion fracture and hydrogen embrittlement fracture are called brittle fracture

2. Fatigue fracture: the fracture of a spring under cyclic loading.

3. Stress corrosion fracture: the spring fracture phenomenon caused by the combined action of tensile stress and corrosive media.

4. Corrosion fatigue fracture: the fracture of the spring under the combined action of cyclic load and corrosive medium.

5. Hydrogen embrittlement, cadmium embrittlement, black embrittlement: brittle fracture caused by high impurity content in the spring material.

6. Wear: Wear is divided into: abrasive, fatigue and corrosion wear fracture.

When the spring is heated to a certain temperature, its elasticity will be affected, and even segregation will occur, which will easily break. Of course, as you said, the ground wire is relatively thin, and the spring may not be heated too much, and the temperature during welding will not be too high. High, so that it will not affect its elasticity and will not break. Furthermore, electrical sparks will be generated due to poor contact during welding. If the spring is not burnt, there will be no problem. If there is damage, it is still invalid.

The main reason for spring machine out of control

Most of the spring machines are controlled by AC servos, and the computer on the spring machines is the control system. At that time, there were a variety of controllers that were not produced by manufacturers, and they were controlled by one of two methods: speed control and position control. Regarding the system out of control, that is, the (flying) defect mentioned by the tuning master, it is impossible to appear randomly in the position control upper computer (spring machine computer control device), at that time, it is in the upper position of speed control. The appearance of the aircraft is more random, and it is also more difficult to eliminate defects.

The main analysis below is the reason for the system out of control phenomenon that exists as a speed control host computer:

1, power supply problem;

2, servo motor encoder and echo related circuit problems;

3, there is a problem with the sequence of spring processing;

4, exchange servo control board and related circuit problems;

5. There are problems with various control wires and terminals.

International spring standardization technology

Although springs are widely used, in terms of varieties and specifications, they are basically non-standardized. They are designed for different host products and have poor interchangeability. Therefore, for a long time, the corresponding technology for spring standardization has not been established in the International Organization for Standardization. Committee, the standardization work of springs is limited. In recent years, due to the development of spring technology and the requirements of industrial technology development, the work of international unified standards around springs has been strengthened.

Before the establishment of the International Spring Standardization Technical Committee, the International Technical Standards Committee ISO/TC 10 formulated technical documents related to springs:

ISO 2162 production technical document-spring, including three parts:

ISO 2162.1 Part 1: Spring drawing

ISO 2162.2 Part 2: Data for cylindrical spiral compression springs

ISO 2162.3 Part 3: Glossary of spring terms

China has formulated GB/T4459.4 “Mechanical Drawing Method” with reference to the above-mentioned international standard ISO 2162.1. The application of rectangular cross-section compression springs for molds is becoming more and more extensive. Due to interchangeability requirements, the International Standards Organization has formulated ISO/DIS 10243 Installation dimensions and color signs of rectangular section compression springs. In reference to this standard, China has formulated JB/T 6653 “Flat Wire Cylindrical Helical Compression Springs”.

The Secretariat of the National Spring Technical Standardization Committee of China proposed to the International Spring Technical Standardization Committee (ISO/TC 227) in June 2007 an international standard proposal for the design, technical requirements and test methods of hot-coiled cylindrical springs and compression springs and automobile leaf springs. At the third (ISO/TC 227) conference attended by 12 member states held in Beijing on October 29, 2005, the international standard for the technical conditions of hot-rolled cylindrical spiral compression springs delivered by the secretariat of the China Spring Technical Standardization Committee was unanimously passed. Proposal. This marks a big step forward for China’s spring technology to the international level.

Application of spring of computer spring machine

Application of spring of computer spring machine:

Most materials have varying degrees of elasticity. If they are bent, they will restore their original shape with great strength. In human history, we must have noticed that the branches of saplings and young trees have great flexibility. Due to the use of this feature in many primitive cultures, the computer spring machine wedges a stick behind a special door or cage, or uses a slip knot to wrap a rod and pull it down; once the tension is released, the stick or rod will Rebound.

They used this method to capture birds and beasts. In fact, the bow uses the elastic spring of the young tree in this way; first pull the bow back, then let go to let it rebound. In the Middle Ages, computer springs Machines began to appear on machinery, such as textile machines, lathes, drilling machines, grinders, and saws. The computer spring machine operator gives a downward stroke by hand or pedal, and pulls the working machine down, and then fix it with a rope. A rod on the machine bounces back and produces reciprocating motion.

The torsion resistance of an elastic material is not lower than its flexibility. As early as the 4th century BC, a torsion spring tensioned with a twisted tendon rope or wool rope was invented to replace simple springs to strengthen the stone crossbow and throw The power of stone machines. At this time, people became familiar with that metal is more elastic than wood, horny, or any such organic substances. In order to find out why the sword is elastic, they conducted many experiments. As a result, his master Ketzibi The stone thrower was invented. The spring of the stone thrower was made of curved bronze plates-actually the earliest leaf springs.

Alligator clip spring

The alligator clip was invented by the scientific research on crocodile in nature. At first, scientists made a model of the crocodile’s head and tested its biting force; later, they wanted to bite the wax with the kind of force used in Humans can produce movable and fixed supplies in daily life, and finally produce alligator clips.

In the research process of the alligator clip, a large number of fixed devices have been used; in the end, it was decided to use a torsion spring in order to allow universal use and cost issues.

*Alligator clip torsion spring has two major characteristics

One, strength:

(1) Angle

Alligator clip springs are generally between 120° and 135°, and the installation angle is generally 45°. Let the spring itself store energy and stabilize it with the force during use.

(2) Outer diameter

The alligator clip has enough space for the spring to expand and contract. While making the outer diameter of the spring small, it will not affect the life of the spring; the smaller the outer diameter of the spring, the greater the strength of the spring.

2. Small space used:

The alligator clip is installed with a torsion spring, which does not take up surface space at all; only a drop point of the clip head is enough.

Inspection and determination of spring load and stiffness

1. Introduction to spring load inspection and measurement

The test and measurement of the spring tension and compression testing machine can be determined by the load of the tension spring and the compression spring. The large spring can be measured when the captain of the material tension and compression tester performs the load inspection. Most of it adopts the principle of leverage and converts the load value into a displacement value to indicate the value On the disk, the primary specifications and functions of the tensile and compression testing machine are actually subject to regulations.

Spring tension and compression load testing machine, spring tension and compression testing machine specifications and performance parameters are as follows:

GT-3(TL-0003)

GT-10(TL-00lA)

GT-100(TL-0lB)

TL-0.5

Maximum load/N

The maximum distance between two hooks in tensile test/mm

Maximum stroke of tensile and compression test/mm

Compression test two pressure plate diameter/mm

The maximum distance between two pressure plates in compression test/mm

shape size length × width × height, the unit is mm

mass/kg

2. Factors of precision of load test

The precision of the load test is not only related to the precision of the load measurement of the testing machine, but also related to the precision of the reading of the length (or the amount of deformation) of the compressed spring during loading. In the measurement of the small amount of deformation such as the injector spring, the precision For higher springs, a dry submeter can be attached to the testing machine to improve the precision of the deformation reading, thereby improving the precision of the load measurement.

3. Points to note about the precision of the load test

Whether it is a compression spring or a tension spring, when measuring the load, the load should be placed on the spring axis line, or perpendicular to the target of the spring axis line, so that the spring will not be twisted when it is deformed. It is a large amount of deformation, when a relatively large relative displacement occurs between the end face of the compression spring and the supporting platform of the testing machine, the method of light buckling can be adopted to relax the spring to reduce friction, and it can also be used on the pressure plate or support. The flat top is equipped with thrust bearings to eliminate the distortion of large deformation.

When measuring the load, attention should be paid to adjusting the “0” position of the testing machine, and the weight of the spring itself should be deducted. For slender springs that are not easy to erect, a mandrel can be added for testing. At this time, you should just stop or reduce The friction force between the spindle and the spring prevents it from affecting the accuracy of the load measurement.

Features and design principles of mold springs

1. Design principle of mold spring

①. The selection of allowable stress of spring materials should be mainly considered to ensure the fatigue life of the spring. The dynamic life of the spring is generally divided into three categories: Type Ⅰ, which bears alternating loads for 106 times; Type Ⅱ, which bears alternating loads The frequency is 103-105; Class Ⅲ, the number of alternating loads is less than 103;

②. The material width-thickness ratio (a/b) should not be too large, and the winding of the spring should not be too small.

③. When designing non-rectangular shaped cross-section springs, it is necessary to derive and draw curves or calculation formulas in different rotation ratios, different width to thickness ratios, deformation correction coefficients and shear stress correction coefficients.

④. According to the given conditions and constraints, choose a design method that is simple to calculate and select reasonable parameters.

2. Characteristics of mold spring

In recent years, with the development of the mold industry, the number and varieties of mold springs have been increasing. Special-shaped cross-section mold springs have the characteristics of long life, large rigidity, and small size. However, the development of design theory has been relatively slow. At present, except for square section strong springs In addition to the more mature design method, the design method of other cross-section strong springs is basically based on the empirical design formula obtained through the test of the specific section. Zhengyi Spring now gives an introduction to the characteristics and design problems of this type of spring.

Let’s first compare a square section with a round section coil spring. In the same space, the load-bearing capacity of a square section wire spring is 43-48% higher than that of a round section spring. Obviously, a rectangular spring is more than 50%.

It can be seen from the analysis that if the advantages of special-shaped cross-section material springs cannot be fully used, they will not produce economic benefits. Generally, they are often used in the following situations: the design load cannot be achieved with round cross-section materials; the spring installation space is small; instead of round Cross-section composite spring; when the required deformation cannot be achieved with the round material spring; where strict spring characteristics are required.

Detailed introduction of automobile spring

In recent years, with the improvement of people’s living standards, cars have entered the homes of ordinary people, and car springs are in short supply. Various springs have also made more people feel a little confused. Here, Zhengyi springs will give you a brief introduction. Various types of car springs.

●Torsion bar spring

Using a long rod made of spring steel with torsion rigidity. One end is fixed to the body and one end is connected to the upper arm of the suspension. When the wheel moves up and down, the torsion bar undergoes torsional deformation and acts as a spring.

●Spiral spring

The most used spring on modern cars has strong shock absorption capacity and good ride comfort; the disadvantage is that it is large in length, takes up more space, and the contact surface of the installation position is also large, making the layout of the suspension system difficult to achieve. compact.

●Leaf spring

Generally, considering the comfort of riding, it is hoped that the spring can be softer for ground impact with high frequency and small amplitude, and when the impact force is large, it can show greater rigidity and reduce the impact stroke, so springs are needed. There are two or more stiffnesses at the same time. Springs with different wire diameters or springs with different pitches can be used, and their stiffness increases with the increase of the load.

It is composed of several slender spring leaves with different lengths. It has a simpler structure and lower cost than a coil spring, and can be compactly assembled on the bottom of the car body. Friction occurs between the various pieces during work, so it has an attenuation effect. But if it produces serious Dry friction will affect the ability to absorb shocks. It is mostly used in vans and trucks, and modern cars that emphasize ride comfort are rarely used.

●Gas spring

The stiffness of the gas spring is controlled by a computer. It can be adjusted according to the required stiffness under the conditions of high and low speed, braking, acceleration and turning of the car. Through the use of the main and auxiliary air chambers, the spring can be in two working states of stiffness: The main and auxiliary air chambers are used at the same time, the gas capacity becomes larger, the rigidity becomes smaller, and vice versa. Gas springs also have weaknesses. The height of the car must be controlled by pressure changes. Air pumps must be equipped, as well as various control accessories, such as air dryers. Poor maintenance will cause the system to malfunction. In addition, if metal springs are not used at the same time, if air leakage occurs, the car will not be able to drive.

Using the compressibility of gas to replace metal springs. The biggest advantage of this discovery is that it has a variable stiffness, which gradually increases with the continuous compression of the gas, and this increase is a continuous gradual process, rather than a gradual change. Another advantage is that the stiffness of the spring and the height of the body can be actively adjusted.

●damping equipment

Although the spring can reduce the impact of the road on the body, if its vibration is not allowed to stop as soon as possible, we will be riding in a car that does not stop. Therefore, we must add a certain amount of resistance during the movement of the spring. The scientific name is damping, which makes the vibration of the spring attenuate quickly. Our usual damping equipment is a shock absorber.

How to choose spring material

First, an overview of spring material selection

The choice of spring material should be determined according to the nature of the spring load, working temperature, stress state, service life, requirements for electrical and magnetic conductivity, process performance, stress, environmental medium, material source and price.

Second, several important points for attention when selecting spring materials

Ⅰ. Material factors

Leaf springs generally use flat steels of 55SiMnVB, 55SiMnMoV, 55Si2Mn, 60Si2MnA, 60CrMnB, 60CrMn, etc.

Medium and small springs, especially helical tension springs, should be given priority to using strengthened steel wire, lead bath isothermal cold drawn steel wire and oil quenched tempered steel wire. Its strength and surface quality are higher, and its fatigue performance is higher than that of ordinary quenching. Fire steel wire, with good manufacturability, simple processing, and stable quality. For large and medium-sized springs, cold drawn or cold drawn steel should be used for high load accuracy and stress; for low load accuracy and stress, it can be Use hot rolled steel.

Electrical springs that use the spring itself as a conductor or springs that work under variable humidity conditions, such as water (including sea water) and water vapor environments, generally use copper and gold steel.

Springs that work under acid contact with other corrosive media are generally made of corrosion-resistant materials such as stainless acid-resistant steel or nickel alloy. For springs used under general environmental conditions, ordinary spring steel is selected, and the spring is made on its surface Anti-rust coating or electroplating (zinc plating, cadmium plating, copper plating) method to prevent corrosion.

The springs used in weighing instruments and instruments, in order to meet the accuracy of not being affected by temperature changes, generally use constant elastic alloys with minimal changes in elastic modulus and expansion coefficient.

Reinforced plastic can be selected for special purpose springs such as light weight, insulation, anti-collision, anti-corrosion, etc., and vibration-proof rubber can also be used to make various types of rubber springs.

Ⅱ. Characteristic factors

Strength and hardness have a great relationship with plane strain fracture toughness. Therefore, its selection should be based on the spring bearing properties and stress.

Hardenability, whether the cross-section of the spring material is hardened and the degree of hardening, have a great relationship with the quality of the spring.

●Special type, the material cross section of the coil spring should be preferred to use the circular cross section. Although the square and rectangular cross-section materials have strong bearing capacity and good impact resistance, they have less material sources and higher prices. Except for special needs, generally Try not to choose this material.

Ⅲ. Temperature factor

Spring materials that work at high temperatures require good thermal stability, resistance to relaxation or creep, resistance to oxidation, and resistance to certain medium corrosion.

Spring materials used at low temperatures should have good low temperature toughness. Austenitic stainless steel spring steel wires such as carbon spring steel wire, piano wire and 1Cr18Ni9, copper alloys, and nickel alloys have good low temperature toughness and strength. Because in low temperature conditions The brittleness of the material is very sensitive to surface defects. The environmental medium is much less corrosive to the material than in the greenhouse, and cadmium and zinc plating are easy to cause cold brittleness. The elastic modulus and expansion coefficient of the material do not change much. It can be ignored in the design.

The working temperature of the spring increases, and the elastic modulus of the spring material decreases, resulting in a decrease in stiffness and a smaller load-bearing capacity. According to GB1239, when the working temperature of ordinary coil springs exceeds 60°C, the shear modulus should be corrected. The formula is: Gt=KtG where G–the modulus of elasticity at room temperature; Gt–the shear modulus at the working temperature t; Kt–the temperature correction coefficient is selected according to Table 2-98. Therefore, the spring that works at high temperature must It is very important to understand the rate of change (value) of the elastic modulus and calculate the impact of the decrease in spring load capacity on the performance.

What are the performance requirements and composition characteristics of spring steel

General characteristics of spring steel:

Spring is an important part of various machinery and instruments. It mainly uses the energy stored during elastic deformation to relieve mechanical vibration and impact, and also uses the stored energy of elastic deformation to work. Because springs are generally under dynamic load Therefore, it is required that spring steel must first have high elastic limit a, high resistance strength b, high flexural strength (s/b), high fatigue strength r (especially notched fatigue strength), and Sufficient plasticity and toughness and good surface quality, while also requiring good hardenability and low decarburization sensitivity, easy to process and form in hot and cold conditions.

The chemical composition characteristics of spring steel:

In order to obtain the required performance of the spring, the carbon content of spring steel is higher than that of quenched and tempered steel, and carbon spring steel is usually in the range of 0.6% to 0.75% C. Due to the hardening of carbon spring steel (such as 65, 75 steel, etc.) The performance is poor. When the cross-sectional size exceeds 12mm, it cannot be quenched in oil. If it is quenched with water, cracks are prone to occur. Therefore, the springs with larger cross-sectional sizes and heavy loads are made of alloy spring steel.

The carbon content of alloy spring steel is generally between 0.46% and 0.70%. The alloying elements contained in alloy spring steel often include Si, Mn, Cr, V, etc., and their main function is to improve the hardenability and tempering of steel. Stability, ferrite strengthening and grain refinement, thereby effectively improving the mechanical properties of spring steel, increasing the elastic limit and yield ratio. Si and Mn mainly improve the hardenability, but also improve the yield ratio, and are better than Si The most prominent role, but it promotes surface decarburization during heat treatment, and Mn makes steel easy to overheat.

Therefore, spring steel for important uses must be added with elements such as Cr, V, W, such as Si-Cr spring steel, which is not easy to decarburize. ;Cr-V spring steel is not easy to overheat, has fine grains, is not easy to grow and coarsen, has good impact resistance, and high temperature strength. Among them, Cr and V are also conducive to improving the high temperature strength of spring steel.