Metal Substitution in Railway Applications Using Function Driven Coupled Analysis

Created by Tamás Schmidt | | Technical Article

Using the capabilities of Altair’s and PART Engineering’ s software for customer specific simulation of composites.

This article will walk you through the process of how X-Plast successfully redesigned a highly stressed metal part for a railroad application using Altair and PART Engineering software.

X-Plast is a young and agile design and engineering company located in Hungary, specializing in injection-molded plastic product development and manufacturing. As a development partner of many international organizations ranging from start-ups to enterprises, X-Plast provides comprehensive solutions from the first conceptual design to the final assembly of high-quality products. Solving the majority of development challenges in-house, X-Plast offers its customers the huge benefit of a one-stop service.

X-Plast, which has won several international awards for its innovative plastic products, aims to offer its customers plastic solutions that are as sustainable as possible. To achieve this goal, the company is using state-of-the-art software, ensuring advanced design and meeting development requirements – building up a product-specific development strategy. This comprises the full range of highly complex function-driven design methods, covering nonlinearity, process simulation, and anisotropy, enabling a fully coupled analysis workflow. In many cases it is vital to perform physical component testing in addition to the digital validation before moving into serial production. Therefore X-Plast has heavily invested in their in-house 3D printing lab to build functional prototypes and small series production.

Since 2019, X-Plast has been using Altair and PART Engineering solutions for structural simulations to meet the increasing customer demands and trends. One of its longstanding customers is Knorr-Bremse, a leading supplier of safety-critical systems for rail and other applications. To reduce costs and weight of the railway components, they started a multi-year collaboration to replace metal parts with plastic ones. Until today, X-Plast has been involved in the development of more than 25 different structural components for Knorr-Bremse, substituting metal through a lightweight plastic solution. To ensure a safe and reliable operation of railway components for more than 30 years these parts have to be strong and durable to meet the many requirements. They must withstand extreme temperature and climate conditions, as well as vibrations and high mechanical loads, even impact from stones.

In a recent project, Knorr-Bremse tasked X-Plast with the redesign of a metal part that had to be lighter while meeting the original part’s performance and stiffness targets. Based on the inhouse experience and knowledge in finite element methods and simulation, X-Plast developed a simulation-driven integrated development process, which enables them to find the optimal structure. The engineers used the geometry of the original metal part as a starting point for the topology optimization in Altair®  Inspire™. In the intuitive Inspire interface manufacturing guides, design constraints and restrictions are easily applied to the model that led to preliminary rib structure. To evaluate design variants in a very short time X-Plast leveraged Altair®  Simsolid®, a powerful next generation simulation tool. Due to short communication channels within the company, the mold designer and simulation engineer were quickly able to find a feasible and manufacturable solution, while   further improving the final part’s stiffness. The simulation department also performed a traditional finite element analysis to fine-tune the structure, insert geometry and to validate the mechanical strength of the assembly. Altair®  SimLab® and Altair®  OptiStruct® enabled the team to consider real-life conditions and nonlinearities, such as closing and sliding contacts, the effects of bolt tightening, and different operating temperatures. Furthermore, these tools allowed for the analysis of small details like stress concentration in the metal inserts. The final step of the isotropic phase of the integrated design process, the stress-based lifetime assessment was carried out.

Integrative Simulation – represent the true nature of the material

To address the anisotropic properties of the part, X-Plast turned to PART Engineering, the expert for structural mechanics and developer of the software solutions Converse and S-Life Plastics. By integrating the capabilities of Converse into X-Plast’s development process, it was possible to bridge the gap between the injection molding software and the finiteimulation model. S-Life Plastics enables the engineers to perform a material data-based strength assessment to reach a high level of simulation accuracy and allow more reliable lifetime predictions of parts.

Injection molding simulation is an essential input for the part- and the tool designer as well. Shrinkage and warpage effects can be identified and corrected. There are several process relevant factors, which affect the parts physical and mechanical behavior. Several injection molding simulation software can be used to obtain the fiber orientations for the complex anisotropic analysis, but X-Plast relies on the industry standard Autodesk Moldflow Insight.  

Converse, through mapping and exporting the fiber orientation and other selected injection molding results, helps to convert the homogeneous isotropic finite element model into a standalone and ready-to-use anisotropic one. In addition to an element related orientation also an orientation dependent material model is required. Defining this manually from literature data is nearly impossible without MatScape®. MatScape® is the integrated material modeler and database that comes with every PART Engineering software. When combined with Converse, MatScape® creates an anisotropic material model from a simple stress-strain curve.

After mapping, the anisotropic analysis can be performed. S-Life Plastics also offers a fully automated strength assessment, accounting for all influence factors, allowing for a fiber orientation-based lifetime prediction and closing the loop of the integrated design process. At the end of the project, X-Plast design team was able to verify the mechanical behavior of the part under different temperature conditions to ensure the desired service life.

More sustainable and cost-effective than before

Using engineering expertise and state-of-the-art software solutions, X-Plast set up an integrated development process to create a highly engineered, durable, and sustainable plastic product that meets operation and manufacturing constraints as well as high quality standards. The comprehensive offering of PART Engineering, Altair and Autodesk enables holistic integrated product design that enables sustainability and impacts the bottom line. X-Plast was able to verify the part’s mechanical behavior under different temperature conditions and ensure the desired lifetime requirement. X-Plast reached the serial production within eight months, saved 35% of product costs, and reduced the weight by 25%, while ensuring 30 years of lifetime.

Best results and more to come

Digitization has become an important driver of innovation in the rail sector, offering great opportunities to improve component reliability and reduce sustainability burdens at one go. Using the PART Engineering and Altair solutions X-Plast reached the weight goals of the Knorr-Bremse component while meeting all other performance targets. While sustainability goals usually entail greater expense to meet all requirements, X-Plast’s highly engineered plastics design is even more cost-effective than the traditional metal part. Following this successful example, companies striving for sustainability won’t have to think twice before undertaking the challenge to replace metal parts with plastic ones. Using the right tools and the know-how of experts such as X-Plast they might be able to increase their ROI and achieve their sustainability goals at the same time.

Author: Tamás Schmidt, FEA Specialist, X-Plast, Székesfehérvár, Hungary