When using 3003 aluminum sheets to manufacture mechanical end caps and support gaskets, will the stress concentration areas of the sheets be prone to fatigue cracks after being stamped and bent?

1. Introduction: Application Value and Fatigue Risks of the 3003 Aluminum Disc Manufacturing Process for Mechanical Products

Mechanical end caps (e.g., motor end caps, hydraulic valve end caps) and bracket gaskets (e.g., engine bracket gaskets, shock-absorbing gaskets) primarily use 3003 aluminum discs as their core raw material. The 3003 aluminum disc manufacturing process for mechanical products mainly includes “raw aluminum disc cutting → stamping forming (contour/hole punching) → bending processing (flanges/support edges) → post-processing (deburring/annealing) → finished product assembly”. This process accounts for approximately 35% of the mechanical manufacturing sector due to its “lightweight nature and high qualification rate (≥95%)”.

However, the stamping and bending stages in the 3003 aluminum disc manufacturing process for mechanical products easily cause stress concentration at the edges, corners, and holes of mechanical end caps and bracket gaskets. As 3003 aluminum alloy is a non-heat-treatable strengthened Al-Mn alloy with high sensitivity to fatigue performance, fatigue cracks tend to initiate at these sites. Statistics show that 60% of mechanical component failures stem from fatigue issues caused by this process, and 80% of fatigue cracks concentrate in stress zones formed by stamping and bending during the process. Therefore, analyzing the correlation between the 3003 aluminum disc manufacturing process for mechanical products and fatigue cracks is crucial for improving the reliability of mechanical products.

2. Impact of the 3003 Aluminum Disc Manufacturing Process for Mechanical Products on Material Stress State

The two core stages—stamping and bending—in the 3003 aluminum disc manufacturing process for mechanical products directly alter the local stress state of the material, laying hidden risks for fatigue cracks:

(1) Stamping Stage: Stress Changes During Hole Punching and Contour Forming

In the stamping stage of the 3003 aluminum disc manufacturing process for mechanical products, the main tasks are punching bolt holes in mechanical end caps and cutting contours of bracket gaskets:

• During hole punching (e.g., 10mm bolt holes in end caps), the edge of the hole undergoes 8%-12% radial shrinkage plastic deformation, forming radial residual tensile stress of 80-100MPa (close to the fatigue limit of 3003 aluminum alloy, 80-90MPa). This is the primary source of stress concentration in the process;

• During contour stamping (e.g., rectangular contours of gaskets), insufficient fillet radius (R < 1mm) leads to a stress concentration factor Kt of 2.5-3.0, laying the groundwork for stress superposition in the subsequent bending stage. This highlights the importance of stamping parameter control in the 3003 aluminum disc manufacturing process for mechanical products.

(2) Bending Stage: Stress Superposition During Shape Forming

As a key shaping stage in the 3003 aluminum disc manufacturing process for mechanical products, bending (e.g., 90° flanges for end caps, 120° support edges for gaskets) further intensifies stress concentration:

• The outer side of the bending angle is in tension (elongation rate 5%-7%), while the inner side is in compression (shrinkage rate 3%-5%). Tangential residual tensile stress of 60-80MPa forms at the angle, accompanied by work hardening (hardness increases from HV45 to HV60), reducing the local plastic deformation capacity;

• If the stress directions of stamping and bending align in the 3003 aluminum disc manufacturing process for mechanical products (e.g., overlapping hole edges and bending angles), stress superposition occurs. The local actual stress can reach 100-120MPa, far exceeding the fatigue limit, directly inducing microcracks.

3. Fatigue Crack Initiation Mechanism in the 3003 Aluminum Disc Manufacturing Process for Mechanical Products

Residual stress and processing defects introduced by the 3003 aluminum disc manufacturing process for mechanical products accelerate the evolution of fatigue cracks during the service of mechanical products (under alternating loads), which can be divided into three stages:

(1) Initiation Site Formation: Synergy Between Process Defects and Material Properties

The stamping stage of the 3003 aluminum disc manufacturing process for mechanical products easily produces burrs at hole edges (height 10-20μm), and the bending stage tends to form surface microcracks (depth 5-8μm). These defects combine with Al₆Mn precipitates at the grain boundaries of 3003 aluminum alloy to become fatigue crack initiation sites. Tests show that the crack initiation life of hole samples with burrs is only 58% of that of burr-free samples, confirming the accelerating effect of process defects on fatigue.

(2) Microcrack Propagation: Superposition of Process Stress and Load

Alternating loads during the service of mechanical products (e.g., R=-1 vibration loads for end caps, R=0.1 compressive stress for gaskets) superimpose with residual tensile stress remaining from the 3003 aluminum disc manufacturing process for mechanical products, increasing the stress intensity factor range ΔK. The crack propagation rate follows the Paris equation (m≈3.5):

• Superposition of residual tensile stress (80-100MPa) from stamped holes in the process and vibration loads increases ΔK by 40% compared to the stress-free state, accelerating the propagation rate by 1.8 times;

• If no stress relief treatment is performed in the 3003 aluminum disc manufacturing process for mechanical products, moisture, oil, or corrosive gases in the environment penetrate microcracks, triggering stress corrosion fatigue and further increasing the propagation rate by 2-3 times.

4. Experimental Verification of Fatigue Performance in the 3003 Aluminum Disc Manufacturing Process for Mechanical Products

To quantify the impact of the 3003 aluminum disc manufacturing process for mechanical products on fatigue cracks, simulated samples were prepared according to the process and tested:

(1) Sample Preparation: Following Actual Process Stages

1. Raw material: 3003 aluminum discs (3mm thick, 150mm diameter, H14 temper), compliant with GB/T 3880.2-2012;

2. Process replication:

• • Sample A (end cap simulation): Completed “10mm hole stamping (burr ≤5μm) → 90° flange bending (R1mm)” according to the 3003 aluminum disc manufacturing process for mechanical products;

• • Sample B (gasket simulation): Completed “rectangular contour stamping (R2mm) → 120° support edge bending” according to the process;

3. Control group: Smooth 3003 aluminum sheets excluding the stamping and bending stages of the process.

(2) Test Results: Correlation Between Process Stages and Fatigue Life

Results indicate that the stamping and bending stages in the 3003 aluminum disc manufacturing process for mechanical products reduce the crack initiation life of samples by over 90%, making them the core cause of fatigue risks.

5. Optimization Strategies for the 3003 Aluminum Disc Manufacturing Process for Mechanical Products

To address fatigue issues caused by stamping and bending in the 3003 aluminum disc manufacturing process for mechanical products, solutions are proposed from two aspects: process stage optimization and post-processing:

(1) Process Stage Optimization: Reducing Stress Concentration

1. Stamping optimization (core improvement in the 3003 aluminum disc manufacturing process for mechanical products):

• • Adopt “stepped hole design” for hole punching (transition from 10mm to 12mm, fillet R0.5mm), reducing the stress concentration factor Kt from 2.0 to 1.3 and residual tensile stress by 30%;

• • Increase the fillet radius of stamped contours to R≥2mm to avoid stress superposition in subsequent bending.

2. Bending optimization (adapting to process characteristics):

• • Use “gradual bending” for end cap flanges (gradual transition from 0° to 90°) instead of one-step 90° bending, reducing tangential residual tensile stress from 60-80MPa to 30-40MPa;

• • Adjust the bending angle of gasket support edges from 120° to 135°, reducing the outer tensile deformation rate from 7% to 4%.

(2) Process Post-Processing: Eliminating Residual Stress and Defects

1. Stress relief annealing: Add a “280-320℃ heat preservation for 1-2h” stage (per GB/T 12608-2023) after stamping and bending in the 3003 aluminum disc manufacturing process for mechanical products, reducing residual tensile stress to 30-40MPa and increasing fatigue life by 2-3 times;

2. Burr control: Add “electropolishing” (10-15A/dm², 5-10min) to the process to reduce hole edge burrs to ≤1μm, eliminating fatigue crack initiation sites;

3. Surface strengthening: Perform “shot peening” (0.4-0.6MPa, stainless steel shots) on key parts of finished products (hole edges, bending angles) made by the process, forming a 50-100μm surface compressive stress layer to offset residual tensile stress.

6. Conclusion: Fatigue Risk Management Logic for the 3003 Aluminum Disc Manufacturing Process for Mechanical Products

Although the 3003 aluminum disc manufacturing process for mechanical products (aluminum disc → stamping → bending → post-processing) is an efficient method for producing mechanical end caps and bracket gaskets, the stamping and bending stages in the process easily cause stress concentration and fatigue cracks. The core management logic is as follows:

1. Adapt process stages to material properties: Optimize the fillet radius of stamped holes and bending angles in the process according to the low fatigue limit (80-90MPa) of 3003 aluminum alloy to prevent stress from exceeding the limit;

2. Strengthen post-processing to make up for shortcomings: Add annealing and shot peening stages to the process to offset residual tensile stress introduced by stamping and bending, and eliminate processing defects;

3. Monitor the process to ensure reliability: Add stress testing (e.g., X-ray stress analyzer) at key nodes (after stamping, after bending) in the 3003 aluminum disc manufacturing process for mechanical products to ensure residual stress ≤40MPa, controlling fatigue risks from the process source.

In the future, “AI parameter prediction” can be further integrated into the 3003 aluminum disc manufacturing process for mechanical products to dynamically adjust stamping pressure and bending speed, achieving real-time control of stress concentration and promoting the upgrading of mechanical products toward “low fatigue risk and long service life”.