Case Studies

Chery deploys LMS Samtech Tea Pipe as mandatory validation tool for every new vehicle development project

Siemens PLM Software helps Chinese carmaker significantly cut development time and costs using an accurate and comprehensive method for detailed brake hose design.

Incorrectly designed brake components can have dramatic consequences
Good brakes are essential for a safe drive. But do drivers really know what happens when they press the pedal, or consider the many technologies involved? Over decades, engineers have been developing systems that use the brakes to increase safety, driver comfort and vehicle handling. Booster systems powered by the engine reduce the force applied to decelerate the car. An anti-lock braking system (ABS) avoids uncontrolled skidding by preventing the wheels from completely locking up and allowing them to maintain tractive contact with the road surface. A system such as an electronic stability program (ESP) uses sensors that detect traction loss and activate the brakes to help steer the car in the direction the driver intends to go. And even more advanced active safety systems can make fully autonomous braking decisions based on information they gather from the environment.

In all processes that involve the brakes, a fast system response is essential. Any signal and applied pressure need to activate the brake calipers instantly and without loss. This is enabled by a hydraulic circuit that includes flexible hoses, usually made of rubber combined with a multi-layer fabric. The hoses must be positioned in a limited space and can undergo large deformations when driving, especially when steering. It is very important to provide them sufficient clearance during any maneuver – if they wear because of repeated abrasion, they may eventually get damaged, affecting the performance of the entire system. Or the hoses could even break. The consequences of incorrectly designed brake hoses can be dramatic, for both the driver and the manufacturer. If problems with the brakes emerge after delivery, they usually lead to a recall, which is a terribly expensive operation and absolutely to be avoided. To avoid these problems, during final prototype testing the displacements and deformations of the brake hoses are thoroughly inspected.

The need for a more effective design process
“Problems with brake hoses on prototype cars were unfortunately quite common,” says Hu Benbo, chief engineer of the brake department at Chery Automobile Company Limited (Chery), China’s leading passenger vehicle exporter. “We had issues, for example, before launching two of our sports utility vehicles, the Tiggo 5 and the Tiggo 7. Fixing those took time and was expensive. Although the brake pipe is actually a small component, it is a very important one with a complex layout. The problem is that once the vehicle development process is in the prototype phase, any adjustment you must make directly affects the time-to-market. So discovering problems at this point is by definition a costly affair, not to mention what the consequence could have been if we had not noticed there was something wrong.”

Chery had a design process that was based on computer-aided design (CAD) and spline curves. The engineers then defined a set of load cases and manually checked the clearance for each of them. This was a very labor-intensive and error-prone procedure, says Benbo: “We could not take into account nonlinear phenomena such as large displacements and rotations, and related buckling and torsion. As a result, the mounting positions we theoretically designed were not optimal and the curvature of the flexible pipes turned out to be very different in reality compared to what we calculated. Moreover, our validation work was far from complete. Brake hoses move with suspension and steering, so what we actually needed was the ability to do full kinematics analysis.”

Chery engineers realized that their method required an update. “The workload was heavy and the design cycle too long,” confirms Benbo. “And on top of that, it was hard to evaluate risk, let alone to avoid it. We often hit situations where the design passed our validations, but presented problems on the test bench.”

The solution: LMS Samtech Tea Pipe
Siemens PLM Software presented to Chery engineers the LMS SamtechTM Tea Pipe software, a comprehensive solution dedicated for mechanical simulation of hoses, cables and pipes. With LMS Tea Pipe, engineers can include the complex hose material behavior and define pipe connectors and support geometries from CAD to determine the optimal length, the connector positions and orientation while checking collisions and curvatures. Simulations can be performed for quasi-static or both linear and nonlinear dynamics loading. The solution is a perfect fit for brake hose design by simulation, and helps Chery engineers decrease their workload, shorten the design cycle and reduce development costs. Using LMS Tea Pipe, engineers can conduct more accurate and more complete studies before the prototype phase. In addition, they can optimize the design and reduce the required length of the pipes, which is also a big cost saver. The Chery engineers validated LMS Tea Pipe for the first time on a complete new vehicle project, and were immediately impressed by the accuracy of the results.

Successfully evaluating the new approach
The validation work started with building a digital mockup (DMU) in CAD that is suitable for dynamics analysis of all the components that surround the hoses, including suspension, brake system assembly, steering link, drive shaft assembly, body and more. Then the engineers defined the hose material, geometric parameters and the clearance requirements in LMS Tea Pipe, and used the software to generate an initial version of the hose in 3D. The 3D model was used in a dynamic validation analysis. LMS Tea Pipe can visualize the hoses in different dynamic states, displaying in 3D how they deform, and whether collisions occur. All results have been compared to test results that were scanned on different real vehicles for various states of suspension and steering. The Chery engineers were very satisfied by the accuracy. “The difference between the scanned results and simulation was never larger than a few millimeters, which is very good given the scale of the surrounding components and the large displacements and deformations of the hoses,” says Brenbo. “The accuracy of LMS Tea Pipe really outperformed our previous process. That was very important for us because it proved that this software is a really good guideline for design and can save us a lot of time and cost. We can do optimization, which allows us to reduce the design margins, for example. In addition, the analysis we can do now is far more complete. Instead of considering a limited amount of load cases, we can evaluate the entire motion behavior of the hose. In this way, LMS Tea Pipe revealed to us some load cases that we never investigated before in simulation, but which could lead to collision. So the software really puts us in a better position before starting the prototype phase.”

LMS Tea Pipe as standard part of future vehicle development
LMS Tea Pipe has now become part of the standard development process at Chery, where safety and reliability are held as most important brand values. “For any new vehicle, it is mandatory to use LMS Tea Pipe during detailed design, and we can only move to the next development stage if the results are satisfactory,” confirms Brenbo, who is really happy that Siemens PLM Software crossed his path. “Before, we didn’t have such a powerful solution as LMS Tea Pipe,” he says. “We used to make lots of mistakes. But having this dedicated software for flexible pipe design has really changed a lot.” Brenbo could significantly increase the productivity of his team. Whenever he has questions or doubts, he can get in touch with Siemens PLM Software specialists to help him out. “It’s a very big advantage that the people from Siemens PLM Software know what they are talking about. They provide high-quality technical support and training sessions that really help our engineers in their daily activities.”

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