## 4 Next Generation HSRS with Higher Speed
### Design Optimization of Service Car Body System
In order to ensure a weak coupling interface, the independent design of the equipment cabin under the floor frame mainly includes the following three points:  
(1) In order to avoid the negative impacts caused by the reciprocating lateral movement of the traction converter, e.g., skirt plate bracket cracks or bolt connection failure (loosed or broken), it is necessary to use the novel rubber hanging elements; as shown in Figure 8a,b, the proportional damping is set as (0.3-0.5)% for elastomers. (2) However, the necessary measures, such as bolt pre-tightening or self-weight wedge tightening, must be taken to raise the vertical hanging stiffness as much as possible so as to avoid the accompanying vibration of the traction converter and other equipment rolling repeatedly. (3) Since the traction converter has the largest generalized mass, the lateral modal frequency is the lowest. For this reason, the structural experts should manage the weak coupling interface, trying their best to raise the lateral modal frequency of the traction  
Figure 17: Self-cleaning of central hollow tread wear can be verified when M-T-M three-car trainset across over dedicated lines of 200 km/h grade, running at 200 km/h in curving negotiation with radius 3000 m, superelevation 150 mm and transition (500–700) m. (**a,b**) Distribution characteristics of left and right wheel wear index for 1 st and 4 th wheelsets of front motor vehicle. (**c,d**) Distribution characteristics of left and right wheel wear index for 1 st and 4 th wheelsets of middle trailer vehicle. (**e,f**) Distribution characteristics of left and right wheel wear index for 1 st and 4 th wheelsets of rear motor vehicle. converter to ca. 14 Hz. And the lateral modal frequency of other hanging equipment (\(m<1250\) kg) shall not be less than 12 Hz. Figure 18: Optimization design of rubber hanging parameters for equipment cabin under floor frame based on weak coupling interface is adopted for service car body system, so as to avoid internal lateral coupling resonance of traction converter as much as possible. (**a–c**) 1 st order lateral bending inherent mode of aluminium alloy car body has evolved into two critical modes, i.e., 1 st order lateral bending modes on lower and upper parts of service car body. (**d**) Safety assessment of lateral vibration for traction converter when running in a tangent line approaching to limit speed of 650 km/h under \(\lambda_{e}=0.06\) according to specified in IEC61373—2010. (**e,f**) Safety assessment of lateral vibration for traction converter when running in a tangent line with higher speeds of (420–550) km/h and near to limit speed of 650 km/h under \(\lambda_{e}=0.10\). (**g**) Safety assessment of lateral vibration for traction converter when running in a tangent line with service speeds of (300–380) km/h under \(\lambda_{e}=0.35\). (**h**) Safety assessment of lateral vibration for traction converter when running in a tangent line with three speed grades of 480/650/780 km/h when considering negative impacts of detrimental wear like central hollow tread wear. The independent design of the above equipment cabin is based on the following two guidelines to realize the weak coupling interface:  
(1) The improved transaction strategy of the flexible body to MBS interface is implemented by applying MMRT. Specifically, considering the low dynamic interaction requirements of both interfaces, including the floor frame under which equipment such as the traction converter is hanged and the roof on which the pantograph with fairing and the air conditioning unit are installed, the constrained DoF is set to zero. (2) As shown in Figure 18a-c, the 1 st lateral bending inherent mode of the aluminum alloy car body is transformed into the 1 st lateral bending modes of the service car body on the lower/upper parts; both modal frequencies are ca. 14.0/17.9 Hz. As shown in Formula (22), only when the constraint DoF is zero will the corresponding interface stiffness be enhanced and the relevant modal mass be reduced.