Forgings are designed to achieve the highest performance with minimal materials and to meet the requirements of load, process performance and expected service life. Therefore, the reasonable forging design requires that the material be able to work under greater stress.
In order to adapt the material to the designed forgings, it is necessary to see whether the material can meet the requirements of strength and toughness, and secondly, the stability of temperature and environment. As for the base is not the most suitable material to analyze its process, and finally to see how the economy.
Requirements for forgings include,
1. Bearing mode
(1) One-way load, divided into tensile load and compressive load or under the operating conditions of the alternating load.
(2) The multi-directional or composite load is divided into stretching, compressing, shearing, bending, torsion and bearing load. They may be parallel to the central axis, or to a certain angle, in the shape of the change in the part should be a uniform transition of the circular solitary, to reduce stress concentration. When stress concentration is unavoidable, the notch toughness of forgings is usually an important factor in material selection.
(3) The periodic load can have high cycle load and low cycle load.
(4) Continuous load, if it is tensile load, may accelerate stress corrosion. The interference fit and residual stress will increase the continuous load.
(5) Thermal load This is caused by temperature changes.
2. Load size and additive status
(2) Increasing or impacting the loading speed.
(3) Forging temperature should be determined at that temperature (minimum, normal and maximum temperature) of the accumulated work time longer.
(4) The environment includes the cycle of the condensation of forgings in the atmosphere, the chemical composition of the environment, and the corrosion, wear, erosion or other friction,
3, special requirements of forgings, special mechanical, physical or chemical performance requirements.
4, life expectancy or reliability, should be defined including the service life. The possibility of rework of forgings should also be considered.
Fault analysis can provide useful information to meet the requirements of material performance. Forgings may be damaged in the design stress range, one of the reasons for premature failure is that the critical design stress is inconsistent with the main streamline direction of forgings.
The deterioration of material performance as the use of time increases may also cause unexpected damage. For example, even in a typical atmospheric environment, stress corrosion cracks resulting from continuous tensile stress 迨. In this case, most of the damage appears on the forgings and exposes the end of the streamline.
Failure analysis may not include other causes of early destruction, such as too large grains, non-metallic inclusions, due to improper forging methods caused by backflow defects, casting deformation is insufficient, as well as due to the mechanical processing of too sharp fillet and assembly-inch with bad and so on inadvertently caused by the stress source.