Accelerated Durability Testing Methods for Critical Components of Vehicles and Aircraft in Complex Operational Environments: Failure Mechanism Analysis Based on HALT and Case Study Validation

I. Introduction: The Severe Challenges Posed by Complex Operational Environments to Product Reliability

As the electrification of automobiles and the increasing adoption of electric propulsion in aircraft accelerate, the environmental stresses endured by critical components throughout their service life are becoming increasingly complex. Coupled effects from multiple physical fields—such as thermal shock, random vibration, and damp heat corrosion—have created bottlenecks for traditional durability verification methods based on life multiplication: long test durations and insufficient fault coverage make it difficult to identify design weaknesses early in the R&D phase.

Highly Accelerated Life Testing (HALT), as a qualitative stress testing method grounded in the Physics of Failure, applies stepped temperature and six‑degree‑of‑freedom random vibration stresses that far exceed product specification limits. In a remarkably short time, this approach induces the manifestation of latent defects, thereby providing precise guidance for design improvements. ^[1] The latest HALT guidelines released by NASA in February 2025 once again emphasize that the core value of HALT lies not in “pass/fail” assessments, but in identifying and understanding failure mechanisms. ^[2] 。

II. HALT Methodology and Accelerated Stress Mechanisms

2.1 Step-Stress Acceleration Strategy

The core of HALT lies in progressively increasing environmental stresses to identify a product’s operating limits and destruction limits. Wei et al. (2025) conducted a series of HALT tests on the active frequency selective surface (AFSS) structure of aircraft, providing a prime example: the tests began with low-temperature step stress (initial temperature: -40°C, step size: -5°C), followed by high-temperature step stress (initial temperature: 70°C, step size: 10°C, up to 270°C), rapid thermal cycling (temperature change rate: 40°C/min), three-axis six‑degree‑of‑freedom random vibration stepping (initial level: 10 GRMS, step size: 5 GRMS, peaking at 50 GRMS), and combined temperature–vibration excitation—comprising six sub‑tests in total. ^[3] 。

2.2 Failure Physics and Acceleration Models

The scientific validity of accelerated testing hinges on whether the acceleration model can accurately reflect the actual failure mechanisms. The Arrhenius equation and the Eyring model are classic tools for analyzing thermally activated failure. Hölscher et al. (2025) pointed out that estimating the lifespan of aluminum electrolytic capacitors requires simultaneously accounting for the temperature factor, the voltage factor, and the self‑heating effect caused by ripple current. ^[4] However, the study also issued an important warning:

This viewpoint reminds the engineering community that engineering interpretations of HALT results must return to the underlying physics of failure, avoiding simplistic extrapolation.

III. Empirical Evidence on Durability Testing of Key Automotive Components

3.1 Assessment of Component Fatigue Durability

Szymczak et al. (2025) with 2×10 ⁶ Cyclic Load As a benchmark for evaluating the durability of automotive structural components, systematic tests were conducted on the traction frame, coupling adapter, and load platform. The tests were carried out continuously under loading amplitudes of ±18.6 kN and a frequency of 6 Hz. The results indicate that the SUV coupling adapter… 1.7×10 ⁶ Next loop Cracks subsequently appeared (load amplitude ±12.33 kN, frequency 5 Hz); the aluminum alloy and steel platform in… 2.24×10 ⁶ Next loop Cracks subsequently appeared. ^[5] 。

It is worth noting that the ratio of the fatigue limit to the tensile strength of the S700MC high‑strength steel substrate is 0.66 …while in the welding area, this ratio plummets to… 0.36 , the fatigue limits of the two differ by 290 MPa —The detrimental effects of welding processes on structural durability cannot be ignored. ^[5] 。

3.2 Nonlinear Effects of Temperature Cycling Degradation in Electronic Components

Banerjee et al. (2024) conducted temperature cycling accelerated degradation tests on a 16 MHz quartz crystal oscillator used in automotive automatic braking systems, based on the AEC-Q200 Level 3 standard. The results revealed a key phenomenon: the degradation of the crystal oscillator is positively correlated with an increase in braking distance. Nonlinear relationship After 458 temperature cycles, the braking distance at a 75% duty cycle deviated from the baseline. 16.46 cm increased to 19.78 cm (an increase of 3.32 cm), and the PWM overshoot voltage surged from 0.32 V to… 2.96V ^[6] 。

3.3 Durability of Brake Friction Materials

The study by Essam et al. (2025) shows that materials containing SiC and ZrO… ₂ The brake pad formulation (BP1) achieves a braking force of… at 8 bar operating conditions. 640.99 N , coefficient of friction 0.3873 , which are 7.7% higher than the formulations without SiC and without ZrO. ₂ The formulation contains 13.6%, but its wear rate (1.2 g/h) is also about 20% higher—while the tribo‑abrasive wear mechanism enhances braking performance, it also accelerates material consumption. ^[7] 。

4. Verification of Environmental Adaptability for Aircraft Electrical Systems

Schefer et al. (2025) focused on the power electronic system of the ATR 72-600 hybrid-electric aircraft, based in North America. 10 years (2013–2022) CAMS EAC4 reanalysis atmospheric data were used to construct mission profiles, and the system evaluated the impact of multiple environmental stresses—such as temperature (5°C to 95°C), humidity (10% to 95% RH), and atmospheric pressure—on creepage distance. ^[8] 。

The study found that creepage distance is the most significant factor influencing breakdown voltage (p-value = 2×10 ^-6 ); at the same time, the higher switching frequencies enabled by wide-bandgap semiconductors actually help suppress electrical treeing caused by dendrite growth—this positive effect offers a new perspective for the reliability design of electrically powered aircraft. ^[8] 。

5. Cross-Scale Failure Analysis and Process Defect Tracing

The failure modes observed in HALT testing must be traced back to their underlying mechanisms through a systematic, multi-scale analysis approach. Wei et al. identified, in the HALT testing of AFSS structures, 15 Typical Failure Modes …covering levels such as PIN diodes, solder joints, PCB substrates, and multilayer structures. The key finding is that the primary cause of failure is not the failure of the PIN diode itself, but rather… Solder joint failure and short circuits caused by exceeding the solder’s melting point —The melting point of Sn63Pb37 solder is 183°C, while the high-temperature step test raises the temperature to 270°C. ^[3] 。

In addition, SMT process defects—such as diode–pad misalignment, skew, voids, and cold solder joints—have been shown to be the primary sites for crack initiation under rapid thermal cycling and vibration conditions. Analytical methods employed include stereomicroscopy, X‑ray systems, C‑SAM (C‑Scan Acoustic Microscopy), SEM/EDS, and metallographic microscopy. ^[3] 。

VI. Conclusion and Outlook

Based on the above studies, it can be concluded that HALT, as a core tool for enhancing product reliability in complex operational environments, has expanded its value beyond mere “defect triggering” to… “Failure Physics – Accelerated Modeling – Process Traceability” a closed-loop methodology. Fatigue testing of automotive structural components, temperature cycling degradation analysis of electronic components, and mission profile–driven assessments of aircraft electrical systems all collectively corroborate the following key conclusions:

(1) Accelerated testing must be anchored in genuine failure mechanisms to avoid result bias caused by incorrect acceleration models. (2) Degradation behavior often exhibits nonlinear characteristics, and linear extrapolation may severely underestimate reliability risks. (3) Cross-scale failure analysis is the crucial bridge that enables HALT to move from “identifying problems” to “solving problems.”

Looking to the future, with the advancement of multiphysics coupled simulation and digital twin technologies, HALT is poised to become deeply integrated with virtual testing, further shortening product reliability verification cycles and driving high‑quality development in the automotive and aerospace industries.