Hydraulic press screw fracture analysis
Abstract
Hydraulic press screw fracture analysis is an important part of the routine maintenance and repair of the hydraulic press equipment. Hydraulic press screw fracture includes many affected factors, such as surface defects, fatigue, material selection, lubrication, and more. To properly analyze the fracture, a complete examination of the screw’s aging condition and inspection of its screw profile need to be performed. Furthermore, fracture surface analysis must be conducted to determine if the fracture was caused by overload, material defects or exhaustion. This final evaluation will provide an insight on how to prevent further failure and aid in creating more reliable hydraulic press screws.
1 Introduction
A hydraulic press is a machine designed to transfer pressurized fluid into mechanical force to shape and cut various materials. The press is composed of two main components, the cylinder and the screw. The cylinder is the body of the press and the screw, also known as the power screw, is the driving force of the hydraulic press. The screw serves as a joint between the cylinder and the output shaft, converting rotary motion from the motor into linear motion and acting as a bridge between the power transfer from the motor to the workpiece (Miyagi et al, 2003).
Screw fracture is a common problem encountered in press machinery. It is a mechanical failure of the screw due to stress or fatigue. The major cause of screw fracture is overload and fatigue related failure. Other causes of screw fracture include initial defects, material failure, periodical overload, improper lubrication, and incorrect surface finish.
2. The Causes of Screw Fracture
2.1 Material Defects
The material used in the manufacturing of the screw determines its fatigue strength, which is closely related to the fracture of the screw. Therefore, the choice of material is a key factor of screw fracture. The most common screw fracture materials are steel and aluminum. Each material has its own advantage and disadvantage. Steel screws are more durable while aluminum has its lighter weight, making it more suitable for lightweight projects. However, improper choice of material can be harmful in the long term, leading to screw fracture.
2.2 Surface Defects
Surface defects can be caused by chemical reactions, improper lubrication, or contamination. These defects will affect the screw’s fatigue strength, leading to premature fracture of the screw. Improper surface finish will cause fatigue failure due to localized stress concentration. Therefore, it is important to make sure proper surface finish and lubrication is used during the manufacturing process of the screw.
2.3 Fatigue
Fatigue is an important factor that affects the fatigue strength of screws. When the screw is subjected to cyclic external load, this will cause plastic deformation of the screw and its fatigue strength will decrease. The fatigue strength of a screw can be further reduced if its service life is too long or if it is subjected to periodical overload.
2.4 Lubrication
Improper lubrication can lead to screw fracture. Lubrication is important to reduce friction stiffening, corrosion and wear. Inadequate lubrication will cause premature fracture of the screw due to insufficient lubrication.
3. Fracture Analysis of the Screw
3.1 Examination of Screw Aging Condition
To analyze the cause of screw fracture, a complete examination of the screw aging condition needs to be performed. This includes inspection of the screw profile, thread pitches, and dimensions. The condition of the surface of the screw should also be examined for any signs of fatigue and wear causing the screw fatigue strength to decrease. This can often be the cause of the screw fracture.
3.2 Fracture Surface Analysis
Fracture surface analysis is an essential step in analyzing the cause of screw fracture. It is important to understand the type of fracture (overload vs. plastic deformation) and identify the primary cause of the fracture. This can be determined by examining the fracture surface for signs of material defects or fatigue failure.
4. Conclusion
Screw fracture can be a major problem encountered in press machinery due to various factors such as material defects, fatigue, and lubrication. A comprehensive examination of the screw aging condition and a detailed fracture surface analysis should be conducted in order to better analyze the cause of the screw fracture. By understanding the cause of the screw fracture, proper preventive measures can be taken to prevent further damage of the screw and create a more reliable hydraulic press system.
