Tensile Test Method for Roller Chains
Tensile test is one of important measurements to review the chain quality. Through the test, we can inspect whether the finished chains have any defects after production and assembly; the possible defects might include poor or inappropriate materials, heat treatment, components, and assembly.
Tensile testing standard for chains are specified by multiple international standards except for the stainless steel chain.
Tensile strength test method
ISO 606 standardization (Short-pitch transmission precision roller and bush chains, attachments and associated chain sprockets) is one of the most commonly adopted testing standards for the tensile testing. Below are some key points when carrying out the test.
1. The chain to be tested for tensile strength should be at least five pitches in length.
2. When testing, the connecting between the specimen and the testing machine, apply a tensile force slowly to the ends of chain by using fixtures which permit free movement on both sides of the chain centerline, in the normal plane of articulation.
3. During the testing, the tensile force should be increased slowly. The extending speed should not exceed 50.8mm/min.
As the tensile force increases, the chain will be elongated at the same time, until the highest tensile force to break the chain. The ultimate tensile strength is the maximum stress that the chain can withstand while being stretched before breaking. This can also be reviewed from force/extension diagram; the highest point on stress curve is the tensile strength of the chain.
4. If the fracture or breaking occurs on the position where the chain and grip is connected, the test should be considered invalid.
5. Tensile test is a destructive test, which means that the test is accomplished by forcing the chain to fail under stress factors. Even though there is no visibly crack on the surface, the chain should not be used after testing.
Tensile Test Standard
Except welded steel chain, plastic chain, most of the international standards stipulate the tensile strength of the chain. The main standards are listed below:
1. Roller chain: ISO 606, ASME B29.1, JIS B1801
2. Double pitch roller chain: ISO 1275, ASME B29.100, JIS B 1803
3. Leaf chain: ISO 4347, ASME B29.8, JIS B 1804
4. Motorcycle chain: ISO 10190
5. Stainless steel: Currently, only ASME B29.21 (700 Class Chains, Attachments, and Sprocket Teeth for Water and Sewage Treatment Plants) stipulates the tensile strength of stainless steel chain.
Chain manufacturers usually produce stainless steel chain referring to the sizes of carbon steel / alloy steel chain standards. However, the tensile strength of stainless steel chain is lower than carbon steel chain. Thus, they are not able to meet the tensile strength standards.
6. Following is the tensile strength comparison table for ISO 606, JIB B1801, ASME B29.1 standards and MCC chain average tensile strength.
|Tensile strength of roller chain stipulated by ISO 606, JIS B 1801 and ASME B29.1 |
MCC’s Tensile testing machines
The tensile testing machine is driven by oil pressure or electric power. The strength is sensed through oil pressure or load cell. Currently, MCC has two novel tensile testing machines. One is horizontal tensile testing machine with 200 tons (2000kn) and the other is a 20 tons (200kn) vertical tensile testing machine. Both machines are able to test the full range of standard roller chains and leaf chains.
Other features include:
1. The testing machines are equipped with the latest computer-controlled models.
2. They are able to measure the relationship between stress and strain (stress- strain curve), elastic limit, yield point and other data when testing tensile strength.
3. They are able to set up different testing condition such as speed, displacement, load rate, and so on.
4. All the data are able to be collected and save on the data collection device. The data of the chain tensile strength are used to review and control the chain quality and improvement.
Applications and benefits of tensile test
1. To ensure the quality of the MCC’s chains exceed the standard requirements.
2. To continually improve and inspect the chain quality. If any abnormality is found in the tensile test result, it can be further analyzed and improved. Possible abnormal causes are listed below.
- Material problem: Poor-quality material, using wrong material.
- Heat treatment problem: Wrong heat treatment condition, abnormal heat treatment equipment.
- Parts: Punching position of the plate hole is deviated, short pins.
- Assembly problem: Missing parts, material mixture.
3. To improve the strength of the chain by testing new material and new heat treatment method.
4. New product development: Testing the strength of the new chain to make sure if it meets the related requirements.