Large-tonnage testing solution of electro-hydraulic servo fatigue testing machine in automobile manufacturing, plane strain fracture toughness KIC test

1. Large-tonnage fatigue testing requirements under the trend of large-scale automobile manufacturing

As new energy vehicles develop toward larger sizes and higher endurance, fatigue performance verification of large structural components such as axles, frames, subframes, and battery pack casings has become increasingly important.These components bear large loads and complex stress conditions. Traditional small-tonnageFatigue testing machineTesting needs can no longer be met.Electro-hydraulic servo fatigue testing machineWith its large load output, high frequency response, and multi-mode loading capabilities, it has become the preferred solution for large-tonnage fatigue testing in automobile manufacturing.

Shandong Huayan Intelligent Equipment Group Co., Ltd. deeply cultivatesElectro-hydraulic servo fatigue testing machineHaving been in the field for many years, it has launched large-tonnage products such as the HYYL-4000 multi-oil circuit dynamic hydraulic loading system and a six-channel axle fatigue test bench, with loads covering 10KN to 4000KN, providing automobile manufacturing companies with full-scenario large-tonnage fatigue testing solutions from the material level to the vehicle level.

2. Common standards for large-tonnage fatigue testing

2.1 Basic standards for fatigue of metallic materials

• GB/T 3075-2020 "Metallic Materials Fatigue Test Axial Force Control Method"
• GB/T 15248-2008 "Metallic Materials - Axial Constant Amplitude Low Cycle Fatigue Test Method"
• GB/T 6398-2000 "Metallic Materials - Test Method for Fatigue Crack Growth Rate"
• GB/T 4161-2007 "Metal Materials - Plane Strain Fracture Toughness KIC Test Method"
• ASTM E466, ASTM E606, ASTM E647 (international standards)

2.2 Special standards for automobile structural parts

• GB/T 47315-2026"Road Simulation Bench Test Methods for Vehicle Structural Durability": Newly released in 2026, it stipulates the axle coupling and wheel coupling test methods for the durability of vehicle structures and is the core standard for large-tonnage bench tests.
• QC/T 1037-2016"Metal Materials for Automotive Fatigue Test Methods": Emphasis on road spectrum load simulation.
• GB/T 30793"Automotive Structural Strength Test Methods".
• ISO 16750 series: Road vehicle environmental reliability.
• Corporate standards of various OEMs (BYD, SAIC, GAC, Geely, Great Wall, Tesla engineering specifications).

2.3 Specific standards for axles and frames

• Bench test method for electric truck frame performance(Group Standard): Specifies the calculation method of frame torsional fatigue load, taking 1/2 of the maximum dynamic load as the torsional fatigue load.
• QC/T 533"Automotive Transaxle Bench Test Method".
• QC/T 29037"Automobile front axle bench test method".

2.4 Testing machine equipment standards

• JB 9397"Technical Conditions of Tension and Compression Fatigue Testing Machine".
• JJG 556"Calibration Regulations for Axial Forced Fatigue Testing Machines".
• GB/T 2611"General Technical Requirements for Testing Machines".

3. Requirements for large-tonnage test specimens

3.1 Material-level large specimens

• For large-section materials such as thick plates and forgings, large-size axial specimens (diameter ≥ 20mm) can be used.
• The length of the gauge section is ≥3 times the diameter, and the surface roughness Ra≤0.8μm.
• If greater clamping force is required, hydraulic wedge clamps are usually used.

3.2 Axle sample

• Sample form: Actual axle assembly (including axle housing, axle shaft, main reducer, etc.).
• Installation requirements: Simulate the actual vehicle installation status, including suspension connection points, wheel hub bearing preload, etc.
• loading point: The wheel grounding point or the wheel hub flange surface applies vertical force, braking force, and lateral force.
• Sample quantity: At least 3 pieces are required for life verification, and more are required for S-N curves.

3.3 Frame/subframe specimen

• Sample form: Actual frame welding assembly or subframe assembly.
• boundary conditions: Simulate the constraints of suspension mounting points, powertrain mounting points, and body connection points.
• Loading method: Multi-channel coordinated loading to simulate turning, braking, bumping and other working conditions.
• torsional fatigue load: Take 1/2 of the maximum dynamic load of the front axle as the torsional fatigue load (according to the frame bench test method).

3.4 Battery pack shell sample (new energy vehicle)

• Sample form: Actual battery pack lower case or tray assembly.
• Test content: Vibration fatigue, fatigue after mechanical impact, fatigue after bottom ball impact.
• Standard reference: GB/T 31467.3, ISO 12405-3, specifications of each OEM.
• Loading method: Multi-axis vibrating table or electro-hydraulic servo multi-channel loading system.

4. Large tonnage testing method

4.1 Constant amplitude fatigue test

• load pattern: Constant amplitude sine wave loading.
• stress ratio: R=0.1 (pulsating cycle) or R=-1 (symmetrical cycle), determined according to the actual stress of the component.
• Frequency: Large-tonnage components are usually 1-5Hz to avoid the influence of inertial force and component heating.
• Number of cycles: According to product specifications, usually 10^5-10^6 times.
• Termination condition: Visible cracks appear in the component, complete fracture occurs, and the stiffness decreases exceeds the threshold or reaches a predetermined number of times.

4.2 Program block spectrum fatigue test

• Load spectrum source: Actual vehicle road load collection (testing site or public road).
• Load spectrum editor: Rainflow counting, damage preservation, small load filtering, time compression.
• Loading method: Divide the edited load spectrum into several load blocks and load them cyclically in proportion.
• Advantages: It reflects actual working conditions more truly than constant-amplitude fatigue and is the mainstream method for durability verification of automobile structural parts.
• GB/T 47315-2026Bench test methods based on road load signals are clearly recommended.

4.3 Multi-channel coordinated loading test

• Applicable objects: Axles, frames, subframes and other complex components subject to multi-directional forces.
• Load channel: 2-6 channels or even more, each channel controls load/displacement independently.
• coordinated control: Each channel is loaded synchronously according to the set phase relationship and load ratio.
• Typical working conditions: Vertical jump (the wheels on both sides move up and down in the same phase); roll and twist (the wheels on both sides move up and down in anti-phase); braking/driving (longitudinal force loading); turning (lateral force loading).
• Shandong HuayanSix-channel axle fatigue test benchSimulation of complex multi-axis working conditions can be realized.

4.4 Axle coupling/wheel coupling road simulation test

• shaft coupling: The actuator is directly connected to the axle and exerts six components of force (three-way force + three-way torque).
• wheel coupling: The actuator applies load through the tire contact point, which is closer to the actual vehicle state.
• GB/T 47315-2026Both test methods are specified.
• A large-tonnage, multi-channel, high-precision electro-hydraulic servo loading system is required.

4.5 Fatigue crack growth and fracture toughness testing

• The large-tonnage electro-hydraulic servo fatigue testing machine can complete the crack growth test of large CT specimens.
• Precast crack → Constant ΔK cycle → Monitor crack length → Calculate da/dN.
• KIC fracture toughness test (GB/T 4161, ASTM E399) can be completed at the same time.

5. Things to note when selecting large-tonnage electro-hydraulic servo fatigue testing machines

5.1 Load capacity and margin

• Select the rated load of the equipment based on the maximum test force, and it is recommended to leave a 30%-50% margin.
• Axle vertical fatigue usually requires 50-200KN/channel.
• Frame torsional fatigue requires 100-500KN.
• Vehicle-level road simulation requires more than 500KN/channel.
• The maximum load of Shandong Huayan HYYL-4000 system can reach 4000KN.

5.2 Frequency and dynamic response

• The testing frequency of large-tonnage components is usually not high (1-10Hz), but attention needs to be paid to the load control accuracy at low frequencies.
• The frequency response characteristics of the electro-hydraulic servo system depend on the servo valve flow, hydraulic cylinder area and oil source pressure.
• It is necessary to confirm the frequency output capability and waveform distortion of the equipment under maximum load.

5.3 Multi-channel coordination capability

• Complex component testing requires coordinated loading of multiple channels, and the maximum number of channels supported by the device must be confirmed.
• Inter-channel synchronization accuracy should be better than ±1ms.
• The control system should support inter-channel load decoupling and cross-coupling compensation.
• Shandong Huayan's six-channel axle fatigue test bed supports 6-channel independent control and coordinated loading.

5.4 Oil source and hydraulic system

• Large-tonnage electro-hydraulic servo fatigue testing machines require high-power hydraulic oil sources.
• The oil source flow should meet the needs of multiple channels working at full load at the same time.
• A cooling system is required to ensure stable oil temperature for long-term continuous testing.
• Accumulator configuration affects instantaneous large flow output capability and system stability.

5.5 Fixture and tooling design

• Fixtures and tooling for large-tonnage testing are the key to successful testing.
• Special connection tooling needs to be designed according to specific components to ensure a clear load transfer path.
• The strength and stiffness of the tooling itself need to be checked to prevent the tooling from failing first during the test.
• Shandong Huayan has rich experience in large-tonnage tooling design and can provideCustomized solutions.

5.6 Security protection

• Large-tonnage tests are highly destructive, and safety protection is crucial.
• Must have: overload protection, over-travel protection, abnormal oil pressure protection, excessive oil temperature protection, power-off protection, and automatic shutdown due to rupture.
• The test area needs to be equipped with safety nets and safety interlocking doors.
• Emergency stop buttons should be installed at multiple points near the operating position and test area.

5.7 Data acquisition and control system

• Synchronous collection of multi-channel data, sampling rate ≥1kHz.
• Supports multi-parameter synchronous recording of load, displacement, strain (external channel).
• The control system should support multiple modes such as constant amplitude loading, program block loading, random loading, and road spectrum reproduction.
• The software supports real-time monitoring, data playback, fatigue damage calculation, and report generation.

6. Shandong Huayan large-tonnage electro-hydraulic servo fatigue testing solution

6.1 Core products

6.2 Solution advantages

1. Extra large tonnage capacity: Maximum 4000KN, meeting the testing needs of most large automotive structural parts.
2. Multi-channel coordination: Six channels of independent control, supporting complex multi-axis working condition simulation.
3. High precision control: Force control accuracy ±0.5%, displacement resolution 0.001mm.
4. road spectrum recurrence: Supports the import and reproduction of real vehicle road load spectrum, compliant with GB/T 47315-2026.
5. Customization capabilities: Design special tooling and testing plans based on customer specific components.
6. Own metering: Ensure equipment accuracy and data traceability through its own measurement and testing company.
7. Patented technology: It has many patents such as electro-hydraulic servo steel fatigue testing machine and has strong technical strength.

6.3 Service process

Demand communication (1-3 working days) → Scheme design (load calculation, tooling design, system configuration) → Production and manufacturing (30-60 days, strict quality control in our own factory) → Installation, debugging and operation training (2-5 days) → Measurement calibration (certificate issued by our own measurement company) → After-sales guarantee (lifelong maintenance, quick response).

Professional manufacturer of large-tonnage electro-hydraulic servo fatigue testing machines, an overall solution for fatigue testing of large structural parts in automobile manufacturing.

Consultation hotline: 13465928815

Company official website: www.huayantest.cn