As Light weighting is the top priority for the automotive industry today, the push for reducing overall vehicle weight will likely include the consideration of materials that have not previously been part of mainstream vehicle design and manufacturing, including carbon fiber composites. Therefore, the deformation characteristics and crush performance of carbon fiber reinforced polymer (CFRP) and steel front bumper crush-can (FBCC) assemblies in Quarter-point Impact Tests are investigated in this article. The experimental tests in this study were conducted using a sled-on-sled testing method. Force-time histories, kinematic data and videos for each test were recorded using several high-speed cameras (HSCs), accelerometers and a load cell wall. The collected data was filtered with SAEJ211 CFC 180 filter and sorted to ease the comparative analysis for the performance of the steel and CFRP bumper assemblies. A similar pattern was observed in the crashworthiness characteristics (i.e. force-time history, force-displacement, crash pulse and deformation patterns) of all steel and CFRP FBCC specimens. Typical failure modes of composite bumper assemblies, which were revealed by the high-speed videos were the failure of crush-can and failure of the bumper beam due to the generation of high stresses as it gets stretched due to its curvature after hitting the sled. On the contrary, local permanent deformation of the beam and crush-can was the predominant failure mode in steel FBCCs assemblies under quarter-point loading. Results obtained from the comparative investigation show that CFRP is a more efficient yet lighter material in regard to the absorption of the impact energy.

Conventional hypoid gear design approach utilizes specific commercial programs provided by gear machine providers. Those programs typically have a set of assumptions as the starting point for the hypoid gear design. That type of approach works well when the overall system performance matches the assumptions. The gearing systems have been evolving significantly to reach ever-higher customer demands. The condition challenges the engineering community to go beyond the conventional wisdom. As the breakthrough ideas come into the system concept, the conventional hypoid gear design assumptions might not be sufficient to represent the actual performance. Unexpected failure modes and reliability of the products could cause serious consequences. Hypoid gear design based on system concept becomes a more effective approach under such conditions. This paper presents examples of how system approach helped analyzing and designing hypoid gears for modern powertrain systems in heavy vehicle applications. The effectiveness of such approach makes those systems realistic and reliable to meet extremely strict customer demands. Conventional hypoid gear design tools require the system to be sufficiently rigid to duplicate the actual gear tooth contacts as observed on the gear tester. Typical relationship between the gear set is represented by E, P, G, and α, which represents three linear displacements and one angle displacement as shown in Figure 1 [1]. This approach works well if the system performance meets all the assumptions defined by the tools. As the complexity of the system increases, more considerations for hypoid gear design become critical. Analytical tools that take into consideration other components beyond the gear set provide an effective way to understand the hypoid gear performance in different conditions closer to the reality. Figure 2 is an example analytical model of a heavy vehicle carrier [2]. Gear performance could be predicted in advanced engineering stage and compared to experimental results at a later stage of the product development. This approach provides insight into potential risks earlier in a product development cycle and cuts the product development cycle time significantly. Another advantage of this type of approach is the possibility to understand the gear set performance under different operating conditions. Conventional hypoid gear design tools focus primarily on vehicle driving condition. The heavy vehicle industry faces more diversified operating conditions based on customer needs. Figure 3 is one example showing the analysis results of one testing condition where ring gear concave side drives pinion convex side (coast mode).

Reducing or eliminating seat noise and vibration are the main objectives of a semi-active damping system implemented in a commercial vehicle seat. The system must be developed such that control forces minimize seat motion. Abrupt motion with semi-active damping systems is typically called ‘dynamic jerk.’ Semi-active damping in a seat application places the control forces close to the seat occupant so there is less ‘filtering’ to protect the human from feeling dynamic jerk. Whereas in an automotive suspension there might be more tolerance for dynamic jerk because the comparatively heavy vehicle body acts to filter some of the dynamic jerk and the interaction of the tire and road input may also mask it. In this research, dynamic jerk has been addressed and studied for the advanced SEAT application. The seat has been tested with varying sine inputs at specific amplitudes. The response of the semi-active damping seat system has been analyzed to characterize dynamic jerk and a control algorithm has been developed to minimize this undesirable response. The conclusion is that dynamic jerk is dependent on the damper’s physical properties as well as the system’s sensors. A Design of Experiments statistical study was carried out to determine what are the most influencing factors. Limiting the range of damping force reduces the control authority; however, allowing full damping force may trigger dynamic jerk. Identifying the dynamic jerk plays an important role in order to have the indication of the properly tuned system. In this research, the identification strategy of the dynamic jerk is studied and developed.

A pitch cone design theory assuming line contact is formulated to analyze the tooth engagement behavior of crossed beveloid gears. The analysis applies the spatial gearing model and beveloid gear manufacturing technique to determine the cutter parameters and geometry. Using the proposed procedure, a crossed beveloid gear pair with small shaft angle is studied. Also, the proposed formulation is capable of quantifying the influence of misalignments including offset and angular position errors on the contour and position of contact path and lines over a complete mesh cycle. The results show that both offset and angular position errors of the mating members worsen the conjugate action of the mating tooth surfaces. Furthermore, both the contact path and the transmission error are more sensitive to the angular error than the offset error. The loaded tooth contact characteristics are subsequently modeled using the finite element method for comparison purpose. The proposed model is partially validated by comparing the numerical simulation results.

A synthesized gear mesh and dynamic model assuming line contact that is derived from a set of manufacturing parameters is formulated for analyzing the beveloid gear mesh-coupling mechanism. Using the proposed model, the effect of the dominant geometry design parameter that is the crossed angle between the first principal directions of the tooth surface curvatures (FPD-angle) on gear mesh characteristic and dynamic response is investigated. Also, the analysis of the gear mesh characteristic and dynamic response subject to torque load variation is performed. It is shown that the dynamic transmission error and dynamic mesh force worsen as the geometry FPD-angle increases for a specific torque load level. Furthermore, even though higher torque load can produce larger contact area, which is desirable, it also increases the gear mesh stiffness and transmission error that tend to aggravate dynamic response.

It is known that the tooth flank geometry, assembly errors and the operating conditions of a gear pair have significant influence on tooth contact, load distribution and dynamic response. However, the study of the effects of assembly errors on the mesh characteristics and dynamic response for crossed beveloid gears has been limited due to the complicated geometry and time-varying mesh characteristics. In this study, three types of assembly errors including shaft angle, offset and gear axial position error are examined based on a synthesized mesh model and a three-dimensional elastically coupled rigid-body dynamic model. Also, the relation between a dominant geometry design parameter that is the crossed angle between the first principal directions of the tooth surface curvatures (FPD-angle) and the sensitivity of mesh characteristics and dynamic response subject to assembly errors is investigated. Through the sensitivity analysis with different FPD-angles, the shaft angle error is found to be the most sensitive factor affecting the mesh and dynamic behaviors of crossed beveloid gear set. On the other hand, the gear axial position errors have the least influence on the mesh characteristics and dynamic response. In most cases, the influences of assembly errors on mesh characteristics and dynamics become weaker with the increase of FPD-angle.

Geometric eccentricity here refers to the radial deviation (radial runout) of pinion or gear geometric center off its rotational center or axis. Such a typical manufacturing or assembly error in gear transmission exhibits inherent effects on the gear dynamic responses. Modeling of eccentricity has rarely been done for high speed right-angle gears such as hypoid or spiral bevel gears. In this paper, two modeling methods are proposed to quantitatively represent the eccentricity in the hypoid/bevel gear dynamic analysis. The first method is based on the loaded tooth contact analysis (LTCA) for a long shaft period. The LTCA results are then used to synthesize the corresponding roll angle dependent varying mesh model parameters. A second simpler method using translational kinematic transmission error (TE) modification is proposed to reduce the computational time. The effects of eccentricity on the gear dynamic responses are then investigated. The eccentricity excited low frequency shaft order dynamics is found to affect not only the overall level of vibration but also the high frequency mesh order responses. The sideband responses are simulated and characterized. This study is expected to improve the right-angle gearing system dynamic analytical capability and assist in guiding the manufacturing or assembly error tolerance specification.

A three-dimensional elastic–plastic finite element model was used to investigate the relative effects of different joint forms on the welding distortion and residual stresses in an automotive differential assembly due to deep-penetration high-energy welding. Numerical studies were carried out to determine optimal selections of heat generation rate and the number of weld segments to ensure both computational efficiency and accuracy of the calculation. To model the constraints and boundary conditions realistically, contact elements were used at the mating surfaces of different structural components and the shrink fit between the gear and differential case was modeled using couple sets. Two situations representing welded gear-case assemblies where the weld joints were oriented at 0° and 30° with respect to the radial direction were analyzed. Predicted welding distortions and residual stresses are compared and discussed in detail. The results indicate that the residual tensile stresses in the 0° radial joint are larger than those in the 30° angled joint and that residual distortion is sensitive to joint form.