Why, How and When do you perform Design Validation for Automotive Systems?

Overview

Automotive Industry is constantly looking at ways and means of reducing costs, delivering on time and staying profitable. Design is the common denominator in all these challenges and Design Validation has become mainstay. Companies investing in developing indigenous Design Technologies emerge successful in the world market. They are able to sustain and innovate at a higher pace than the rest of the competition. This is possible on account of the following capabilities:

  • Delivering products faster with up-front Engineering Design Validation as a part of the product development process
  • Compressing the product development cycle time
  • Developing lean design by incorporating value engineering of least cost alternatives for first prototype
  • Increasing reliability by design – an Initiative that will eliminate hidden costs associated with product recall, re-design and/ or replacement of parts – popularly referred to as the ‘Bottom of the Ice Berg

‘Valuefacture’ of a product ensures product acceptance by customer while assuring improvement in bottom line profitability. Companies that have identified design engineering as a profit center have continued to invest in tools and technologies that augment Design Validation with assured return on Investment.

Automotive Sub-Systems Design Validation
Design Validation of Automotive Sub-Systems

Challenges faced by the Automotive Industry

Increasing functional complexity, predatory pricing, compulsive cost reduction commitments, aggressive deadlines, field failures, warranty costs, product recalls are too familiar in the automotive sector. Almost all automotive Tier I and II suppliers and their vendors share these common issues.

Cross-functional teams in every organization deal with one thing in common – drawings. A reflection of perfection in design, drawings affect the profitability of any organization.  Perfection in design is achieved only by validating the design concept and continuously refining the design to enhance value and performance.

Imagine what a 10% weight reduction can do to a Company’s bottom line profitability. Add to it a 10% higher efficiency than a competitive product or technology and the company’s USP just got stronger. Now, choose alternate cost-effective material and the company has just got the winning combination it needed. This is possible if the design department is given Cost Reduction Targets & Performance Targets – initiatives that will go a long way in increasing the gap between the company and its competitors. Such targets are achievable ONLY by Design Validation.

What is Design Validation?

Ensuring the design meets the fit, form and functional requirements specified in the statement of requirement for a product, by means of analytical and / or physical testing, is commonly referred to as Design Validation.  Analytical methods include Finite Element Analysis (FEA), Computational Fluid Dynamics (CFD), Kinematic Analysis of Mechanisms and Tolerance Stack Up Analysis. Physical testing include measurements relating to deflection, strain measurements, tri-axial vibrations, fluid flow parameters, temperature, frequency response among others. This is accomplished by performing accelerated durability testing, on-road vehicle testing, four-post vehicle testing, hot-chamber and cold-chamber testing of component assemblies and sub-systems. For physical testing, a set of prototypes (preferred minimum number is 8) conforming to dimensional specifications are necessary. However, for analytical testing a 3-Dimensional CAD model of the design is sufficient.

Why Design Validation?

Imagine a situation wherein a product needs to be tested for tri-axial vibration response to meet functional requirements. After building a set of acceptable prototypes, the assemblies are tested individually on a shaker table, one direction at a time. At the end of the test, that could last anywhere between a few hours to a few days, if failures are witnessed, then design changes need to be effected. What caused the failure in the first place? One is left with only a failed prototype and not a solution! Add to this the predicament to deliver on time, tool change, cost implications, loss of confidence and above all, customer trust, we have a complex challenge of monstrous proportions.

On the contrary, if the design team had been able to validate the design using analytical methods the first prototypes would have passed the test, leading to a win-win situation for the Company and its customer. Evaluate alternatives that are cost-effective and predict the failure modes and ensure fatigue analysis yielded higher cycles than test requirements.

Every organization needs to give the best to the customer. On the same note, every employee needs to give his/ her best to the organization and the design team has to deliver the best products. This is possible only by constant innovation and design validation.

Basic objectives of any organization in terms of critical business issues are met by Design Validation.  Answers to any of the following questions, in affirmative, would emphasize the need for Design Validation as a part of the Design process.

  • Is profitability under threat from predatory pricing?
  • Have we developed the Best-in-class Cost effective product?
  • How important is Technology for product to survive?
  • Should we need to improve product performance?
  • Cost Reduction – is it a high Priority?

Functional Design Validation for Automotive Components & Systems

Stiffness & Deflection Analyses:

Stiffness of automotive parts is vital to meet performance criteria, especially in parts such as brackets, mounts, body structure components, machined castings among others. Such Stiffness studies find immediate relevance in following areas:

  • Anti-vibration Mount Design
  • Suspension attachment to body structure
  • Instrument Panel support structure
  • Brackets used in mounting sub-systems such as water pump, oil pump, radiator, cross-member reinforcements, steering attachment among others
  • Machining of casings – to maintain tolerance of straightness, flatness, location and orientation
  • Tyre deflection due to inflation and loading – for ride comfort and force transmissibility studies
Dynamic Stiffness of Engine Mount using Design Validation approach
Dynamic Stiffness and Point Mobility Studies in Engine Mount Design
Frequency & Buckling Analyses:

It is a well known fact that resonant conditions reduce component life. Systems designed for limit loads in axially-loaded members need to have buckling calculations done to ascertain safety and reliability. Some of the benefits of frequency & buckling analyses for automotive systems include:

  • Natural frequency calculations for body structures, mounts, support brackets, rotating components including fans, transmission elements, power-train among others
  • Limit load calculations using Linearized Buckling analysis for steering systems, suspension components, engine components, brackets and body structure sub-systems

Frequency calculations are a pre-requisite for performing response estimations for harmonic and random excitation.

Durability & Fatigue Analyses:

A vehicle is tested on a 4-post shaker system using road-loads as input. At the end of testing, components are found to have failed. Since loads transmitted to the failed components would not be known, re-design to overcome the failure is a daunting task. A system level analysis with fatigue calculations would throw light into vulnerable areas in the system and help address the failure issues. This is a powerful approach to solving such issues in addition to predicting possible modes of failure. DFMEA would then document the same along with mitigating factors and considerations.

Fatigue Life Calculation for High Cycle Fatigue of Aluminium Alloy Wheels using Design Validation
Alloy Wheel: High Cycle Fatigue Life Analysis

Components are subjected to cyclical load testing on test rigs to ensure required number of cycles are completed without evidence of failure. This requirement can be easily tested on a digital prototype virtually, to ascertain zones of failure, cycles to failure and modes of failure.

When this exercise is carried out at the design stage, it is possible to evaluate alternate designs to arrive at least cost designs for higher profitability.

Vibration & Dynamic Analyses:

Accelerated durability testing is conducted by placing automotive sub-systems on shaker tables and subjecting the same to varying base  excitation such as fixed-amplitude sine-sweep or random excitation.  Life is consumed in these tests rapidly, leading to a failure.  If no failures are evident after a stipulated duration, the component(s) are said to have passed the criteria.

This can be easily verified on digital designs using Simulation approach, first by extracting required number of eigen modes and then performing a post-dynamic analysis for computing the response characteristics.

Advantage of digital simulation is enhanced by performing a combination of what-if scenarios, that is generally, unavailable in test rigs, unless an expensive investment is made for special purpose testing equipment.

Thermal and Fluid Flow Analyses:

Estimation of temperature, pressure, velocity among other parameters can be computed using Computational Fluid Dynamics Software (CFD) in combination with Finite Element Analysis (FEA) for thermal deformation and effect of pressure on structural side.

Be they electronic thermal management of engine control systems, climate control devices, radiator circuit, fan studies, brake rotor cooling, hot- and cold- chamber testing, Simulation has come a long way in addressing critical performance challenges and optimization of design.

Several correlations between test and analysis data have revealed the powerful technological advantage a manufacturer enjoys by implementing these solutions effectively, early in the design cycle.

CFD is very useful to estimate characteristics of water pump, oil pump, fuel delivery devices and systems.

Non-linear Analysis:

Critical sealing systems, light weight composites, manufacturing process simulations require sophisticated Non-linear analytical treatment.  Effectiveness of sealing systems under assembled conditions involving initial deformation can be found using Non-linear Simulation Analysis.

Non-linear Analysis of Elastomer used in Ball-Joint Design Validation
Non-linear Analysis of Elastomer used in Ball-Joint

Large deformation analysis and Large displacement analyses ensure that product safety and performance are not affected during function.  Seals, Gaskets, Bellows, Hoses, Weather Beading, Tyre inflation and loading are some of the areas that Non-linear analysis finds application in the Automotive sector.

Kinematic Analysis:

Mechanisms find use in automotive industry extensively. Door closure, windows, accelerator, braking, fuel-trap-door opening, transmission gear selection, hood/ deck-lid opening, seat actuation are some of the areas where Kinematic analysis is important. This ensures fail-safe actuation and performance. Forces calculated using Kinematic analysis is used in FEA to estimate stresses and deflections.

Summary

Design Validation, integrated as a part of the design process, ensures that automotive products and systems produced are sustainable in the long run, in terms of :

  • Technological Ownership
  • Cost-effective Product Development
  • Increased Reliability and Quality

Additional benefits from Sustainable designs include conservation of:

  • Material
  • Resources
  • Energy

This would necessarily result in Least Cost Designs. It is the Need of the hour for the automotive sector whose profitability is under pressure due to cost, time and quality issues.

Natarajan Ramamoorthy
Design Professional with almost 3 decades of experience working with numerous companies, providing designs for new products, VAVE on existing products, conducting Design Audits and Dimensional Management programs. Teaching Finite Element Analysis, Geometric Dimensioning & Tolerancing (GD&T), Tolerance Stack Up Analysis for well over 2 decades. Certified ASME GDTP Technologist. Education: MSME from The University of Toledo, Toledo, OH, USA Past: Consultant, Ford Motor Company, Dearborn, MI, USA
Natarajan Ramamoorthy
Natarajan Ramamoorthy
Natarajan Ramamoorthy