The pre tightening force of the threaded fastener connection is to make the threaded fastener connection receive the force in advance before bearing the working load, and this pre applied force is the pre tightening force. Proper pre tightening force is an important prerequisite to enhance the reliability and tightness of fastener connection. If the pre tightening force fails to meet the specified requirements, there will be gaps or relative slippage between the connected parts after loading, resulting in looseness of fasteners and even making the whole machine unable to work normally. If the pre tightening force is too large, it will cause artificial damage to parts. For example, if the pre tightening force is too large, the O-ring will be crushed and the seal will fail.
Improper pre tightening force of threaded fastener connection will lead to the following consequences:
1. Static failure of connecting parts of threaded fasteners
If the threaded fastener is tightened too tightly, i.e. the pre tightening force is too large, it will cause artificial damage to the parts and components. The bolt may be broken, the connection parts may be crushed, bitten, twisted or broken, or the thread profile may be cut off and released.
2. Slippage, separation or looseness of fasteners by connecting parts
For the common bolt connection bearing the transverse load, the preload causes the positive pressure between the connected parts and relies on the friction force to resist the external load. Therefore, the magnitude of the preload determines its bearing capacity. If the pre tightening force is insufficient, the connected parts will slip, resulting in dislocation, skew and wrinkle of the connected parts, and the bolts may be cut. For the bolt connection subjected to axial load, the pre tightening force causes the pressing force on the joint surface. The residual pre tightening force after the external load is the pressing force when working on the joint surface. If the pre tightening force is insufficient, it will lead to the loosening of the joint surface and even the serious consequences of the separation of the two connected parts. At the same time, the insufficient pre tightening force will also cause strong lateral vibration, resulting in loosening of the nut and other phenomena.
3. Fatigue failure of bolts
In most cases, improper preload will cause the bolt to fail due to fatigue. Although reducing the preload can reduce the average value of the total load on the bolt, it can increase the load amplitude. Therefore, the total effect is to reduce the fatigue life of the bolt and cause fatigue damage.
Therefore, the range of pre tightening force must be determined in the assembly process. JinRui reminds us here that we must determine the scientific and reasonable pre tightening torque range according to the importance of the connected parts, the stress situation, the movement mode, the structural characteristics, the thread specification and grade, the material of the connected parts and the purpose of the connection; The torque requirements specified in the process shall be strictly observed during assembly. Only in this way can the reliability of threaded connection and the fatigue strength of the connection be really improved.
About Jinrui, whether you are a fastener demander / dealer / supplier, if you want to know more, you can visit the official website of Jinrui:www.chinajinrui.net
Display of some products of Jinrui Jiangsu Jinrui metal products Co., Ltd. is the production base of Shanghai Jinrui standard parts. The factory covers an area of more than 20000 square meters, the registered capital is 50 million yuan, the total investment is more than 100 million yuan, the annual output is more than 20000 tons, and the products are exported to more than 40 countries. Since its establishment in 2001, after more than 20 years of unremitting efforts, Jinrui company has developed into a new layout with Jiangsu Haian as the production base and Shanghai Baoshan and Henan Nanyang as the sales center. At present, Jinrui's main products include the following six categories: 1. The main products of bolts include: metric and American round head oval neck bolts (also known as fishtail bolts), inner and outer hexagon bolts, hexagon flange bolts, carriage bolts, hub bolts, etc 2. Stud products: full thread thread thread, double headed studs, etc 3. Nut products: hex nuts, flange nuts, heavy nuts, square nuts, butterfly nuts, etc 4. Screw products: self tapping screws, self tapping and self drilling screws, wood screws, various machine screws, etc 5. Washer products: flat washer, spring washer, square washer, locking washer, etc 6. Non standard products related to fasteners Jinrui's wire drawing plant also provides processing services such as fine drawing, rough drawing and spheroidization of wire rod, and supplies finished wire rod of various domestic large brand steel plants. Based on the business philosophy of "development and innovation, pursuit of excellence", Jinrui has successively introduced multiple models of head forming machines, thread rolling machines, nut machines, hot heading rolling machines, lathes, large-scale hot heading machines and their supporting testing equipment, such as magnetic particle flaw detection machines, metallographic analyzers, salt spray testing machines, direct reading spectrometers and optical screening machines, tensile machines, Vickers hardness meters, Rockwell hardness meters, etc., and has established independent R & D departments, It can produce various high-quality fasteners such as GB, DIN, ANSI, JIS and ISO international standards. The products are widely used in petroleum, chemical industry, boiler, wind power generation, expressway guardrail, elevator guide rail, machinery manufacturing, construction sites, auto parts and medical devices. Since its establishment, Jinrui has developed vigorously. It integrates the advantages of each family, careful design and strict selection of materials to make the products more durable and won the praise and praise of the majority of users. Jinrui won the ISO9001:2000 international quality system certification in 2001, the special equipment manufacturing license in 2010, and the TS16949 automobile quality management system certification in 2012. Moreover, the products are covered by the people's Insurance Company of China "global product liability insurance", to ensure that every screw can be used with confidence, firmness and peace of mind! No matter now or in the future, Jinrui will always adhere to the core service concept of "quality first, science and technology to prosper the enterprise, users first, and considerate service", and sincerely provide you with high-quality services and high-quality products. Jinrui will also become your most loyal and long-term partner.
