Hexagon helps YAMAS optimise anti-vibration rubbermetal suspension bushing design

YAMAS, a global leader in the production of rubber-based noise and vibration-damping elements for the automotive industry, has been serving customers with its strong R&D infrastructure and co-design competence since 2002.

YAMAS’s customers include automotive OEMs such as Volkswagen and Porsche. The company operates from two locations in Karacabey, Bursa, Turkey, with a total area of over 31,000 m² dedicated to production, testing, research & development, and warehousing. YAMAS’s product range covers various anti-vibration components for passenger, commercial, off-highway, rail, and industrial applications.

Challenge: Designing to withstand radial and cardanic movements

Control arm bushings, which connect the control arms to the frame or body of a vehicle, play a critical role in allowing suspension components to move easily when a vehicle encounters rough or uneven surfaces. Rubber — an inherently flexible material — minimises the transmission of noise and vibrations to the vehicle’s chassis.

However, YAMAS found its anti-vibration bushings faced challenges when operating under radial and cardanic movements. “Strain values are very high on the region where the bushing is subjected to tensile and shear forces during the simultaneous cardanic and radial movements. For this reason, cracking occurred in the specified region in the continuous dynamic movement of the bushing under vehicle service conditions,” explained Semih Koçak, R&D Engineer at YAMAS.

He continued, “Our main challenge was to design the weak area on the rubber during radial and cardanic movement while still meeting the static requirements of the bushing in all directions. The design constraints included the length of the inner tube, the outer tube diameter, and the inner tube diameter of the bushing. Independent of the vehicle assembly area, the design variables included the inner tube centre form diameter and inner tube centre form.”

Figure 1: Virtual testing of rubber materials.

Solution: Increasing bushing performance with simulation

To overcome this challenge, YAMAS employed advanced simulation tools and accurate material models. Koçak and his team knew that numerous key factors would contribute to the company’s ability to have good simulation results and develop an efficient engineering workflow, including:

• A robust simulation tool
• A well-proven Finite Element (FEA) solver
• Accurate rubber material models capable of simulating very large elastic deformation
• Accurate metal material models capturing elastoplastic behaviour
• A proper mathematical, numerical algorithm, such as Herrmann Reduced Integration for the elements modelling the rubber part

Three simulation steps

With these factors in mind, YAMAS used Marc, Hexagon’s advanced nonlinear simulation solution, to develop an engineering workflow that involved three simulation steps:

Step 1: Thermal analysis to simulate the cooling of the part after vulcanisation

Step 2: Swaging to simulate the swaging process applied to the part

Step 3: Related direction movement to simulate the statictests applied to the part, including radial, axial, cardanic, and torsional loading

YAMAS also prepared the mesh structure for the simulations using Apex, Hexagon’s CAE-specific direct modelling and meshing solution. This enabled efficient pre-processing and high-quality mesh generation. The company then leveraged symmetrical modelling capabilities to reduce the model size and simulation running time for loading conditions in the radial and axial directions.

Validating simulation results

One of the project’s most important parts was YAMAS’s ability to validate simulation results. To accomplish this, the company compared simulation outputs with data from physical tests to ensure the virtual models were accurate and reliable. “The validation process gave us confidence in the simulation methodology and the design decisions based on the results,” Koçak said.

An improved bushing configuration

The design optimisation process focused on two critical parameters identified as having the most significant impact on reducing strain values: the inner tube’s outer shape and the rubber thickness. Koçak explained, “By evaluating these two variables together, we were able to reduce strain values and increase the bushing’s operating performance under dynamic conditions. This targeted optimisation approach allowed us to efficiently explore the design space and arrive at an improved bushing configuration.” 

Figure 4: Typical loading conditions for the simulations.

Results: Accelerated development and improved product performance

By deploying advanced simulation tools and accurate material models, YAMAS significantly improved its engineering workflow and product performance. “The analyses that Hexagon solutions provided allowed us to validate components, reducing our development processes from a month down to a week one week,” Koçak said.

The optimised bushing design resulting from the simulation-driven approach exhibited reduced strain values and increased operating performance under dynamic conditions. Impressively, the simulation accuracy rate reached 93.5%, enabling YAMAS to minimise the time and resources spent on physical prototyping and manual design iterations.

Looking ahead with Hexagon

Looking ahead, YAMAS plans to build on this project’s success by further improving its bushings’ dynamic performance accuracy. “We’re going to pair the current study with dynamic finite element solutions to gain a deeper understanding of the relationship between strain rates and cracking on rubber,” he said.

But the company isn’t stopping there. Recognising the potential of emerging technologies to streamline its design processes even further, YAMAS plans to deploy Hexagon’s ODYSSEE platform. By leveraging ODYSSEE, YAMAS aims to integrate artificial intelligence and machine learning techniques into its workflow. “Ultimately, our goal is to get to optimal designs faster and accelerate our time-to-market for new products,” Koçak concluded.