Road Load Data What you need to know for automotive and component testing and simulation. Bangkok, Thailand

Transcription

1 Road Load Data What you need to know for automotive and component testing and simulation Friday, 10th June 2011, Bangkok, Thailand

2 Introduction to Durability Testing

3 What is Durability? Ability of a vehicle to survive an expected service life Reliability is the probability of a product s successful performance of an intended function up to a pre-determined life. Quality is the consistency with which h a population of products perform throughout their life. Durability is a subjective term relating to the useful life of a product and is the term given to the type of testing used to determine the objective measures mentioned above. What are the major durability issues: Often relate to reliability issues with components Less often are structural

4 What is Durability? Durability How long will it last? What is the fatigue life? Repetitive loading emphasis Performance Does it behave as expected? What are the characteristics? Measurement emphasis

5 Durability Specifications Durability is the ability to survive an expected service life Warranty period such as 3 years or 50,000 miles 150,000 miles, 6000 hours of targeted customer usage Safety Critical parts 3-4 targeted customer lifetimes

6 Why Do We Need To Test?

7 Test Topics Next we will go on to discuss the: why, who, when, what, where, & how of testing.

8 Why Do We Test? Confirm physical performance meets predicted design targets Ensure correct operation throughout the service life of our products Identify and correct manufacturing and assembly incidents prior to final vehicle release Provide complete durability coverage Significant recall and customer perception costs g p p associated with field failure

9 Why Do We Test? The variability of end-users, manufacturing processes, materials, etc. can severely impact durability Durability Loads Geometry ls Material To efficiently address durability issues we must first understand and replicate the durability phenomenon

10 Why Do We Test? Consider the impact of a component failure: Ignition switch failure ($15 part) $15 (part) + $35 (labor) * 8M (vehicles) = $400M Recall Notice $0.39 Postage stamp * 8M (vehicles) = $3.1 Million Just for the Stamps!

11 Who Tests? Vehicle Manufacturers (OEMs) Tier 1 suppliers (suppliers to OEMs) Tier 2 suppliers (suppliers to Tier 1) Independent test houses Government agencies

12 Who Tests? Vehicle manufacturers (OEMs) passing test responsibility to Suppliers Testing required to confirm manufactured components and sub-assemblies bli meet OEM performance goals Suppliers increasingly have to accept consequential liability for non-performance of products in service More testing on components and sub-systems, less testing ti on full vehicles.

13 Who Tests? Suppliers need to test both for validation of product performance and to protect against warranty liability Testing to OEM requirements will show specification conformance Testing is necessary to support quality improvements and cost reduction activities Component reliability evaluated through testing

14 When Do We Need To Test? Committed $ C o n c e p t Design Tooling Sub-system Manufacture Vehicle Manufacture P r o d u c t i o n 1. Design Confirmation 2. Sub-system Validation 3. Product Validation 4. Quality

15 Where Do We test?

16 Where Do We Test? Proving Ground Testing Full vehicle testing on the Proving Ground ~$3/mile 3 months Functional running vehicle required

17 Where Do We Test? Proving Ground Activity (Customer Correlation) Pave or Belgian Block Washboard Pot Holes Curb Strikes Rough Road Cross Country Ride & Handling Other Special Events

18 Where Do We Test? Laboratory Testing Full vehicle testing in the Laboratory ~$0.70/mile 3 weeks Functional running vehicle NOT required

19 Where Do We Test? Laboratory testing moves into the Computer Laboratory and Proving Ground Testing is testing of physical prototypes, sub-systems and components Computer methods are performance evaluation of virtual prototypes using analytical testing

20 Where Do We Test? Virtual Tools commonly employed today: Finite Element Analysis Life Predication Multi Body Dynamics Analytical = Prediction Analytical Prediction Physical = Confirmation

21 What Do We Test? Durability is not the only Vehicle attribute, testing is also conducted for: Crash Powertrain NVH Ride and Handling Testing occurs at the component, sub-system, and full vehicle levels

22 What Do We Test? Full Vehicle System or Component

23 What Do We Expect From Test? Functional Evaluation Confirmation of the basic kinematics of the specimen (e.g. suspension, window winding mechanism) Parameter Evaluation Measurement of the characteristics of the specimen (e.g. roll steer, modal survey) Durability Evaluation Confirmation that the wear and fatigue properties of the specimen meet design goals

24 What Do We Test What Are The Objectives? Target mismatch Design Engineer Targets Determine average service load then keep all stresses below 2/3 of Yield keep maximum identified stress using Finite Element analysis below fatigue limit Test Engineer Targets With 99% confidence assure that less than 5 parts in 100 will fail in service Service is defined as 95th percentile customer, 160,000km usage Does meeting the design targets necessarily mean meeting the test targets?

25 What Do We Test What Are The Objectives? For each durability test we must define failure. A few possible definitions of failure: - Fracture of the specimen into two or more pieces. - Development of visible cracks of a certain size. - Large-scale yielding of the specimen. - Change in stiffness of the specimen. - Excessive deflection of the specimen. - Excessive wear of the specimen. Design tests so that failure is detectable.

26 What Do We Need to Achieve? P(x) Safety Factor Service loading Strength

27 What Do We Need to Achieve? P(x) Safety Factor Service loading Strength Over-design

28 What Do We Need to Achieve? P(x) Safety Factor Service loading Strength Under-design

29 What Do We Include in Test What Are The Environmental Considerations? Mechanical Loading Forces applied to the specimen and reacted either inertially or though a fixed load path Thermal Load and Humidity Thermal environment, ambient, under-hood, sun load and humidity may need to be applied if specimen durability is sensitive to these effects (e.g. thermoplastics) Corrosion and Abrasion Salt spray may be needed to correctly evaluate durability for ferrous materials Dust may need to be introduced to correctly evaluate wear

30 What is Fatigue? Fatigue of a metal is a process in which the metal experiences progressive structural damage from repeated cyclic loading. Fatigue results in the formation and growth of cracks. The cracks may propagate to cause complete fracture of the component.

31 What is Fatigue? Fatigue life is a measure of the duration of cyclic loading required to form and grow cracks to a predetermined size. Log (Alternati Log ( σ ng Stress) σ a ) Life to Failure (Cycles) Fatigue life consists of two principle stages: Crack initiation Crack propagation

32 Test Loading Methodologies Descending order of realism and time Customer Usage Proving Ground Road Simulation Shaped Random Noise End-Level Sequence Block Cycle Constant Amplitude The challenge to test engineering is to achieve an acceptable level of realism in the time allotted to be economically competitive!

33 How Do We Test? Durability Testing Approaches Success Testing (no failures occur) Failure Testing Large sample size required to achieve confidence Little understanding of product behavior Smaller sample size (more practical). Understand product weaknesses (make continual improvements). Ensure that lab tests duplicate field failure modes.

34 How Do We Test? Success Testing Example Field Testing: Assess reliability by testing numerous parts up to one design life, with no failures. Downfalls: 1. Sample size: How many samples must be tested without failure to have 90% confidence of 98% reliability? n = (1 0.90) n = 113 parts!!! 1 (YOU tell the boss!) 2. No information on product behavior, weaknesses, failure modes. R 1 n+ 1 = ( 1 C) R = C = n = Estimate of reliability of population. Confidence (I.e., probability that the population reliability is at least as high as the estimate, R). Number of specimens tested.

35 How Do We Test? Failure Testing If failures occur, can estimate life distribution using Weibull distribution. Now, reliability for any time, t, can be estimated. Ideally, want 6-10 samples tested to failure, but can estimate Weibull parameters with fewer samples (lower confidence) lity Scale) ibull Probabil Unre eliability (Wei Time to Failure (log scale) F ( t) = (1 e) γ t α F(t) = γ = α = fraction that fails by time t ( Unreliability ) shape parameter characteristic life

36 Test Types Laboratory Durability Test Acceleration The goal of testing ti is to induce fatigue damage faster than in service (or on the proving ground)

37 Test Types Accelerating accumulation of damage achieved by: Increasing amplitude Increasing frequency Removing non-damaging content Main approaches Cyclic Block Cycle Shaped Random Noise End Level Sequence Simulation

38 Accelerated Durability Testing Simple Cyclic Measured Service Strain Range-Mean Rainflow Matrix ε m Material Properties ε ε r N Calculate fraction of fatigue life used ε S Adjust applied load to achieve N selected strain level Select strain level Cyclic Test and cycle count Load t

39 Accelerated Durability Testing Simple Cyclic Advantages Test Acceleration (1000 x real time) due to increased average amplitude of applied load and increased rate of strain cycle application Disadvantages Multi-axial loading not possible Dynamic load amplification (frequency effects) due to specimen resonance not replicated Test results may be a poor indicator of service life if the material properties, manufacturing process or design of the specimen changes Not suitable for inertially-reacted systems.

40 Accelerated Durability Testing Block Cycle Measured Service Strain Range-Mean Rainflow Matrix ε m Material Properties ε εr ε 0 N ε m ε 0 ε ε r t S Remove strain ranges below fatigue limit Develop equivalent block cycle strain history Adjust applied loads to achieve selected strain levels Block cycle test load t

41 Accelerated Durability Testing Block Cycle Advantages Test Acceleration (100 x real time) due to removal of non-damaging cycles and increased rate of strain cycle application Relatively l insensitive iti to material and manufacturing process changes Multi-axial loading possible Disadvantages True multi-axial loading not possible Dynamic load amplification (frequency effects) due to specimen resonance not replicated Not suitable for inertially-reacted systems.

42 Accelerated Durability Testing End-Level Sequence Loading Description Sequence of end-levels Amplitude t Applications Specimens subjected to variable amplitude loading (uniaxial and multiaxial). When sequence effects are important. When phase relationship between channels must be maintained. Fixed-reaction i component testing.

43 Accelerated Durability Testing End-Level Sequence Loading Advantages Reproduces realistic sequence of amplitudes. Allows simulation of sequence effects. Maintains approximately correct phasing between channels. Allows frequency acceleration (fixed-reaction tests). Disadvantages Some errors in phase simulation in multi-axial tests. Not as easy to accelerate as block cycle tests. Not suitable for inertially-reacted systems.

44 Accelerated Durability Testing Shaped Random Noise Loading Amplitud de f plitude Am t Description Random signal with specified spectral shape. Applications Specimens subjected to variable amplitude loading (uniaxial or uncorrelated multiaxial). Single axis vibration tests. Squeak and rattle

45 Accelerated Durability Testing Shaped Random Noise Loading Advantages Easy to specify. Minimal specification and storage. Replicates a wide variety of natural vibrations. Disadvantages No control of end levels. Uncorrelated multi-channel tests may not induce realistic fatigue damage. Does not well-represent periodic overload conditions and their associated sequence effects.

46 Accelerated Durability Testing Road Simulation ε Measure rig transfer Measured Service Strains and Loads (y n ) ε ε 0 Material Properties N y n ε t function H xy between drives x n and responses y n Remote Parameter Control (RPC) process compensates for multi-axial dynamic test system response y n t x n t Desired Responses Simulation Loads

47 Accelerated Durability Testing Response Simulation Advantages Test Acceleration (10 x real time) due to removal of non-damaging events Multi-axial loading effects correctly replicated Dynamic loading effects correctly replicated Minimal modification of real road data Correct sequence of loading reproduced Accurate replication of failure mode and failure location Disadvantages Currently requires instrumentation and measured loads data for different test specimens (e.g. different vehicles)

48 Challenges with Durability Assessment Validation of durability targets occurs late in the development program The inherent lack of confidence in current predictive tools necessitates t physical testt Most automotive components under go multi-axial variable amplitude loading

49 Global Durability Trends Testing is expensive but testing is necessary Lack of experience can result in expensive mistakes Increased focus on CAE generates greater demand for component data and validation tests Increased reuse of existing test data requires test focused data management

50 MTS Systems Corporation Global Market leader in testing systems and software in Durability and Ride & Handling. 6DOF Long Stroke Road Simulator High Frequency MAST SWIFT Wheel Force Transducer

51 MTS Systems Corporation Broad Testing Solutions

52 MTS Systems Corporation MTS Product Line Durability Test Type Full Vehicle System Component 4-Poster / Spindle Coupled Simulator Drivetrain MAST Damper / Shock & Elastomer Ball Joint, Exhaust & Steer TestStand & Testline RPC & MPT Software

53 4-Poster / Spindle Coupled Simulators Full Vehicle System Component MTS Model 320 Tire Coupled Road Simulator (Four Poster) Fast setup time Able to produce results quickly. Actuators can be mounted below floor level - Drive-on simulators - Able to interface with environmental chambers MTS Model 329 Spindle-Coupled Road Simulator Up to 6 DOF Control at each wheel Highest degree of simulation accuracy available Configurations available to reproduce - Body roll (slalom events) -Body yp pitch (brake events)

54 MAST Systems Full Vehicle System Component MTS MAST (Multi-Axial Simulation Table) Systems Accelerated replication of service data for - Body components and assemblies - Seats - Fuel Tanks - Radiators - Engine mounts - Exhaust systems - and more! Model High Frequency MAST Controlled frequency exceeding 100 Hz 2 meter table Compact design Applications include - Seats - Radiators - Instrument Panels - HVAC Systems

55 Shock, Damper & Elastomer Systems Full Vehicle System Component MTS Model 835, 849, 850 and 851 systems Performance characterization & durability testing for - Shock absorbers - Dampers - Struts MTS Models 831 and 833 Systems Characterization ti and durability testingti 100 to 400 Hz typical High Frequency system.01 to 1000 Hz

56 Ball Joint, Exhaust and Steer Systems Full Vehicle System Component MTS Model 324 Exhaust Test Systems Valves to tailpipe Full Simulation Testing Based on proven MTS MAST Technology MTS Steering Test Systems Several systems to choose from including - Model 335 & 337 Rack & Pinion Systems Lateral, Vertical and Steering Loads Block cycle or Time History Reproduction

57 TestStand & Testline Systems Full Vehicle System Component TestLine For the Do It Yourselfer Versatile and reliable array of test components Cost Effective TestStand Solutions Test system design and consulting services Acquire leading-edge technology - In a cost-effective manner Collaborative process to augments in-house skills.

58 RPC & MPT Software Full Vehicle System Component RPC Pro Software (Remote Parameter Control) Full-featured Road Simulation Advances signal processing and editing Fatigue Analysis State of the art simulation technologies MPT (Multi-Purpose TestWare) Software Easy to use For creating and automating many test types Test Procedures can be built that include - Function Generation - Data Acquisition - Event Action - Triggers

59 MTS Systems Corporation MTS Simulation Test Consultants Instrumentation and Data Acquisition Analysis and Editing Fatigue Correlation Test Development Fixture Design Global Support Training

60 m Engineering a better world for ground vehicles