Summary of test methods and standards for dynamic fatigue testing machines: special article on automobile manufacturing and auto parts scenarios

1. Dynamic fatigue testing machine—the core tool for reliability verification in the automotive industry

In the automobile manufacturing and auto parts industry, the fatigue life of products is a key indicator of quality level.Dynamic fatigue testing machineBy applying cyclic alternating loads to the specimen, the repeated stress conditions of the product in actual use are simulated, and the fatigue life, fatigue limit and S-N curve of the material or component are measured. It is an indispensable testing equipment for automobile R&D and quality control.

Produced by Shandong Huayan Intelligent Equipment Group Co., Ltd.Dynamic fatigue testing machineseries, covering two major technical lines of electronic servo and electro-hydraulic servo, with loads ranging from 10KN to 4000KN, and are widely used in fatigue performance testing of automobile body sheets, chassis structural parts, fasteners, elastic components and other products.System summary of this articleDynamic fatigue testing machineTest standards, sample requirements, test methods and selection considerations in automobile manufacturing and auto parts scenarios.

2. Automobile manufacturing scene testing standard system

2.1 Basic fatigue standards for metallic materials

Axial force control fatigue: GB/T 3075-2020 "Metallic Materials Fatigue Testing Axial Force Control Method" - the core axial fatigue testing standard, stipulating the constant amplitude fatigue test method under stress control; ASTM E466 "Metallic Materials Axial Force Control Constant Amplitude Fatigue Testing Standard Method" - internationally used, necessary for compliance testing of export models and foreign brands.

rotational bending fatigue: GB/T 4337-2025 "Metal Materials - Fatigue Test - Rotational Bending Method" - 2025 updated version, applicable to shafts and pins.

low cycle fatigue: GB/T 15248-2008 "Metallic Materials Axial Constant Amplitude Low Cycle Fatigue Test Method" - suitable for high plastic deformation zones; ASTM E606-2021 "Standard Practice for Strain Controlled Fatigue Testing" - international standard for low cycle fatigue.

fracture mechanics: GB/T 6398-2000 "Metallic Materials - Fatigue Crack Growth Rate Test Method"; GB/T 4161-2007 "Metallic Materials - Plane Strain Fracture Toughness KIC Test Method"; ASTM E647 "Fatigue Crack Growth Rate Test Method".

2.2 Specific standards for the automotive industry

• QC/T 1037-2016"Metal Materials for Automotive Fatigue Test Methods": The core fatigue testing specification in the automotive industry, emphasizing "working condition simulation fatigue testing" - using road spectrum loads instead of constant amplitude loads to more realistically simulate actual working conditions such as bumpy road impacts, turning lateral loads, etc.
• T/CSTM 00790.2-2022"Thin Steel Plate for Automotive Part 2: Axial Force Control Fatigue Test Method": Special for vehicle body thin plate (thickness 0.5-2.5mm).
• GB/T 47315-2026"Road Simulation Bench Test Method for Vehicle Structural Durability": A new national standard will be released in 2026, stipulating the axle coupling and wheel coupling test methods for vehicle structure durability, applicable to M and N class vehicles.
• ISO 16750 series: Road vehicle environmental conditions and electrical and electronic equipment testing, including environmental reliability testing such as mechanical shock and vibration.

2.3 Special standards for automobile parts

3. Detailed explanation of sample requirements

3.1 Axial fatigue specimen (GB/T 3075)

Size requirements: The diameter of the gauge section is 6~10mm (round bar specimen); the length of the gauge section is ≥ 3 times the diameter; the clamping end is coaxial with the specimen axis, and the transition fillet radius is ≥ 4 times the diameter.

surface quality: The surface roughness of the gauge section is Ra≤0.8μm; circumferential grinding, the grinding direction is parallel to the axis; no scratches, burrs, folds and other surface defects.

Batch requirements: The same batch of samples must have the same shape, size, and surface condition; each group must have at least 3 to 5 samples (different stress levels); the samples must be marked with a unique number.

3.2 Automobile thin steel plate specimen (T/CSTM 00790.2)

Recommended size(Thickness t=1.0~2.5mm): test section width w=(1~3)t; parallel section length Lp=(1~3)w; transition fillet radius r=(3~10)t.

special request: When the thickness is <1mm, attention should be paid to the jitter problem of the time-displacement curve during the test; a reinforcing piece can be pasted on the clamping end of the sample to prevent damage to the clamping end.

3.3 Welded joint specimens

• Welds and heat-affected zones (HAZ) must be included.
• The weld is located at the center of the gauge length section of the specimen.
• After welding, heat treatment is required according to product specifications (if any).
• The surface needs to be polished until it is flush with the base metal, but excessive polishing must not weaken the weld.

3.4 Physical samples of automobile parts

• Use actual parts and retain the original manufacturing process.
• Design special fixtures to simulate actual installation boundary conditions (restraint methods, pre-tightening force, etc.).
• The loading point should be consistent with the actual stress point.
• Conduct non-destructive testing before testing and record the initial defect status.

4. Detailed explanation of test methods

4.1 Stress control method (high cycle fatigue)

Principle: Apply alternating stress of constant amplitude and record the number of cycles when the sample breaks.

Parameter settings: The stress ratio R is usually R=0.1 (tension-pull), R=-1 (symmetrical cycle); the frequency is 10-100Hz, selected according to the material and sample size to avoid heating; the waveform adopts sine wave (standard requirement).

Termination condition: The specimen is completely broken; the predetermined number of cycles is reached (usually 10^7 times, that is, "out"); the load cannot be maintained (the stiffness decreases beyond the threshold).

4.2 Strain control method (low cycle fatigue)

Principle: Apply alternating strain of constant amplitude, suitable for scenes with large plastic deformation.

Parameter settings: Strain ratio Rε=-1 (symmetric strain cycle); total strain range 0.2%-2% (equal cross-section specimen) or >2% (funnel-shaped specimen); frequency is usually ≤1Hz to avoid strain lag and heat generation.

Measurement requirements: Must be equipped with an extensometer to accurately control strain; record cyclic stress response curve (hysteresis loop).

4.3 Road spectrum load simulation method

Principle: Use the road load spectrum collected by the actual vehicle and simulate the real working conditions through program block loading.

Implementation steps: Actual vehicle road load collection (strain gauges, acceleration sensors) → load spectrum editing and compression (rain flow counting, damage retention) → import into the testing machine control system and load cyclically according to program blocks → real-time monitoring of the response of key parts and benchmarking with actual vehicle data.

Advantages: Compared with constant amplitude fatigue, it more truly reflects the fatigue damage in actual use of automobiles. It is the recommended method of QC/T 1037.

4.4 S-N curve measurement method

Group method: Select 3-5 stress levels, test 3-5 samples at each level; use stress S as the ordinate and logarithmic life N as the abscissa to fit the S-N curve; suitable for medium and short life areas (10^4-10^6 times).

Lifting method: Determine the fatigue limit (maximum stress under a specified life); adjust the stress level step by step, downgrading one level if the previous one fails, and upgrading one level if it does not fail; usually 10-15 samples are needed, and the fatigue limit is obtained through statistical analysis.

4.5 Crack growth rate test (da/dN)

• Use standard CT (compact tensile) specimens or CCT specimens.
• After prefabricating fatigue cracks, cyclic loading is performed at constant ΔK.
• Monitor the crack length in real time and calculate the crack expansion rate da/dN.
• Draw the da/dN-ΔK curve to determine the fatigue threshold value ΔKth and Paris formula parameters.

5. Precautions for model selection

5.1 Load and frequency

• Load matching: Select according to the maximum test force, and it is recommended to leave a 30% margin.Automobile sheets are less than 10KN, chassis parts are 50-200KN, and axles are more than 200KN.
• frequency range: High-cycle fatigue requires high frequency (≥50Hz), while low-cycle fatigue requires low frequency (≤10Hz).Confirm the frequency output capability of the device within the full load range.

5.2 Control mode and waveform

• Both stress control and strain control modes must be supported.
• Waveforms include at least sine waves, triangle waves, and square waves.
• High-end requirements need to support program block spectrum loading and random loading.

5.3 Fixtures and tooling

• Auto parts have different shapes, requiring manufacturers to have the ability to customize fixtures.
• Wedge clamps, hydraulic clamps, centering clamps and other options.
• Shandong Huayan can provideOne customer, one planCustomized tooling design.

5.4 Data collection and software

• Sampling rate ≥1kHz, real-time recording of load, displacement and strain data.
• The software supports automatic drawing of S-N curves, fatigue limit calculation, and crack growth analysis.
• Supports data export (Excel, CSV) and automatic report generation.
• Comply with GB/T 2611 general technical requirements for testing machines.

5.5 Environment and safety

• If high and low temperature fatigue testing is required, an environmental chamber (-70℃~+200℃) is required.
• The equipment should have overload protection, over-travel protection, and automatic shutdown functions in case of breakage.
• The electronic servo model has no oil stains and low noise, and is suitable for clean laboratories; the electro-hydraulic servo model needs to consider the noise and oil temperature of the hydraulic station.

5.6 Manufacturer strength and after-sales service

• Choose those with independent research and development capabilitiesFatigue testing machine manufacturer, rather than traders.
• Confirm whether the manufacturer has its own measurement and testing capabilities to ensure equipment accuracy and traceability.
• After-sales service response time, spare parts supply, and technical support capabilities are the keys to long-term use.
• Shandong Huayan is a national high-tech enterprise with its own measurement and testing company and guaranteed after-sales service.

6. Shandong Huayan dynamic fatigue testing machine product matrix

Source manufacturer of dynamic fatigue testing machines, professional solutions for fatigue testing of automobile manufacturing and automobile parts.

Consultation hotline: 13465928815

Company official website: www.huayantest.cn