Specification for shot peening of springs
1 Scope
This standard specifies the scope, terms and medium of, and technical requirements and inspection methods for shot peening of cylindrical spiral compression springs (referred to as coil springs) and automotive leaf springs (referred to as leaf springs).
This standard is applicable to the shot peening technics for the purpose of raising and improving the fatigue life of cylindrical spiral compression springs and automotive leaf springs. It may be referenced by the shot peening of other springs.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this standard. For dated references, subsequent amendments (excluding corrections), or revisions, of any of these publications do not apply to this standard. However parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition applies.
GB/T 1805 Nomenclature of springs
3 Terms and definitions
For the purposes of this standard, the terms and definitions specified in GB/T 1805 and the following apply.
3.1
technics parameter
No. Technics parameters Definition
3.1.1 Shot material Processed shot material to be used for shot peening
3.1.2 Shot dimension Shot diameter
3.1.3 Shot hardness Hardness of shot peening medium, abbreviated to HRC
3.1.4 Shot velocity The velocity at which the shot leaves the centrifugal wheel or peening gun
3.1.5 Shot flow rate Shot mass flow per unit time, in kg/min or kg/s
3.1.6 Peening angle The angle between the motion track of the shot and the surface of the target material
3.1.7 Peening time Duration during which shot peening is carried out, in s.
3.1.8 Peening distance The distance from the centrifugal wheel of a peening gun or shot blasting machine to the surface of the part
3.2
almen strip
a type of special strip for comprehensive measurement of the parameters of shot peening technics, referred to as strip.
3.3
strip jig
a tool used for fixing strips.
3.4
arc height
the surface layer of a strip undergoes plastic rheology under the impact of a shot, which causes the strip to be spherically curved toward the peened shot surface. Cut into the deformed sphere surface from a plane, which is taken as the reference plane. The distance from this plane to the highest point of the sphere surface is called the arc height
3.5
arc height gage
a special measuring tool for determining the arc height value of a strip after subjected to shot peening.
3.6
arc height curve
the curve drawn with a set of data indicating the variation of arc height value f dependent on peening time t obtained while a group of strips of the same type undergoes shot peening for different time (or the number of peening times n) respectively provided that other shot peening technics parameters are constant.
3.7
peening strength
there is only one saturation point on the arc height curve under any set of technics parameters, and the arc height value over this saturation point increases slowly as the shot peening time (or the number of peening times) increases. For doubled shot peening time at the saturation point, the arc height value does not exceed 10% of that at the saturation point, and the arc height value at the saturation point is defined as the peening strength under the set of technics parameters.
Foreword I
1 Scope
2 Normative references
3 Terms and definitions
4 Principle of shot peening
5 Requirements for shot peening medium
6 Strips
7 Strip fixture and arc height gage
8 Technical requirements
9 Inspection methods
Annex A (Informative) Shot peening equipment
Annex B (Informative) Adjustment to peening strength and coverage percentage
Figure 1 Shapes of acceptable shots
Figure 2 Shapes of rejected shots
Figure 3 Strip jig and structural and dimensional drawings
Figure 4 Structural and dimensional drawings of an arc height gage
Figure 5 Schematic diagram for arc height measurement
Figure 6 Arc height curve graph
Figure 7 50%
Figure 8 70%
Figure 9 90%
Figure 10 98%
Figure B.1 Conversion chart
