In order to enhance the contact fatigue performance of the Cr12Mo1V1 die steel component, the ultrasonic impact surface-modification process was introduced into the heat treatment process of 1060 °C quenching + cryogenic treatment (−150 °C × 2 h) + two times of tempering at 520 °C × 2 h in this paper. The influence of the ultrasonic impact number on the surface morphology, roughness, micro-hardness value, residual stress, microscopic morphology of spalling pits, contact fatigue life, and EBSD inverse pole figure of the Cr12Mo1V1 die steel component were investigated utilizing a laser confocal microscope, 3D laser confocal microscope, micro-hardness tester, X-ray stress meter, scanning electron microscope, rolling contact fatigue testing machine, and EDAX-TSL system equipped with a field-emission scanning electron microscope, respectively. In comparison to other ultrasonic impact numbers, the Cr12Mo1V1 die steel component owned the smallest roughness of 0.027 μm, the highest micro-hardness value of 867 Hv_0.1 and the largest residual compressive stress of −1318 MPa, respectively. Meanwhile, the contact fatigue life of the Cr12Mo1V1 die steel component was significantly improved by 223% to 5.231 × 10⁷ cycles. After ultrasonic impact treatment, the spalling pits revealed that the crack propagation angle increased from 28° to 34°, the depth increased from 153 μm to 175 μm, and the failure mode consisted of Hertz’s contact theory. This study provides an effective surface strengthening solution for enhancing the contact fatigue performance of Cr12Mo1V1 die steel components.

In order to improve ride comfort, mounting system was required to effectively isolate the vibrations generated by the engine, preventing them from being transmitted to the vehicle body and the cabin, while ensuring that the displacement of the powertrain remains within controllable limits under various operating conditions. This study investigated the vibration isolation performance of single bell plate hydraulic mount in a quarter‑car model. Key parameters including force transmissibility and relative displacement transmissibility were analyzed under varying damping of the main rubber spring, different mass combinations (engine, body, wheel) and different road excitations. The results showed that with optimized parameters ( K u = 3.39×10 ⁴ N/m, B u = 2500 N·s/m, K t = 2.5×10 ⁵ N/m, B r = 100 N·s/m), minimum force transmissibility in the low‑frequency region and low relative‑displacement transmissibility in the high‑frequency region can be achieved. Appropriate matching of M b , M w , and M e further reduced both force and relative‑displacement transmissibility. Under random road excitation, force transmissibility, mount stroke, and suspension stroke increased with road roughness, whereas relative displacement transmissibility between engine and frame decreased significantly (by 67.0 % on Grade B and 85.5 % on Grade C compared to Grade A). With impact excitation, force transmissibility changed variably with grade, while mount and suspension displacements were markedly amplified; nevertheless, the mount maintained effective control across all roughness levels.