ASQ Reliability Division October 10, 2019 Timothy M. Hicks, P.E. (Mechanical Performance) Roch J. Shipley, Ph.D., PE, FASM (Materials)
Structural integrity is ensured in the design phase by a thorough review of a product’s intended use and foreseeable misuse ◦ Testing is performed for verification ◦ Materials of construction are reviewed ◦ Manufacturing process controls ensure that the design intent is met ◦ Documentation addresses operation, maintenance, and inspection, with warnings The testing methods utilized for design verification and validation are also critical when it comes to analyzing failures Today’s focus will be to: ◦ Discuss some different aspects of structural integrity testing ◦ Provide an overview of processes utilized to ensure a successful and safe design ◦ Provide guidance to get it right the first time, avoiding any need for failure analysis
Timothy M. Hicks, PE (Tim) ◦ Mechanical Engineer ▪ BS - Michigan Technological University ▪ MS – Rensselaer Polytechnic Institute ◦ Industry – 36 years experience ▪ 27 years in design, testing, and manufacturing ▪ 9 years in engineering consulting
Roch J. Shipley, PhD, PE, FASM ◦ Materials Engineer ▪ BS and PhD – Illinois Institute of Technology ◦ Industry – 39 years experience ▪ 10 years in manufacturing and corporate research ▪ 29 years in engineering consulting
General overview ◦ Wide variety of companies and industries on call Please ask questions during or after presentation Broad overview of topics Don’t hesitate to seek out more information from ◦ colleagues ◦ suppliers ◦ industry groups ◦ technical societies ◦ additional experts ◦ follow-up with us afterwards (contact info at the end)
Requirements Design concept Detailed design Failure Mode Effects Analysis (FMEA) ◦ So issues are recognized and avoided to the fullest extent possible Assess, test, and validate ◦ Software modelling ◦ Full scale prototypes ◦ Materials samples Goal is to be both efficient AND complete
Design still in concept phase – Low Manufacturing in progress – Medium Products in distribution chain – High Products in the field – Even higher Failures have occurred in the field - Highest Therefore, test early and often!
Thousands of recalls per year Recalls.Gov combines ◦ CPSC (Consumer Product Safety Commission) ◦ NHTSA SA (National Highway Traffic Safety Admin) 914 recalls of 29 million motor vehicles in 2018 ◦ USCG (United States Coast Guard) ◦ EPA EPA (Environmental Protection Agency) ◦ USDA (United States Department of Agriculture) ◦ FDA (Food and Drug Administration) Compilations on sites such as ◦ https://www.statista.com/topics/3798/product-recalls- in-the-united-states/ ◦ Again, test early and often!
Dimensional Appearance Load → Stress ◦ Specification ◦ Reasonably foreseeable Usage / Wear Maintenance, inspections, service ◦ Consequences of deviations
Temperature ◦ Operation ◦ Shipment, storage, etc. ◦ Washing, sterilization (medical devices) Chemical ◦ Operation ◦ Biocompatibility ◦ Washing, including adjacent components, sterilization, etc. UV ◦ Natural ◦ Sterilization Radiation ◦ Sterilization ◦ Again, specified vs. reasonably foreseeable ◦ Nuclear – another whole area
Metal Plastic / Polymers Ceramic Composite material ◦ Concrete ◦ Wood Concepts apply to all materials, details differ
Casting Forging Molding Welding Machining ◦ Surface finish ◦ Stress concentrators ◦ Might remove beneficial grain flow in formed parts ◦ Residual stress Heat treatment Stamping Additive (3D printing)
Evaluates all possible failure modes for manufacturing processes and product useage Critical dimensions, surface finish, etc. Materials / components themselves do not fail ◦ Respond to environment – predictable ways (engineer’s responsibility) Load / stress – including complex stress states, residual stress Chemical / Corrosion Temperature Wear
Testing to address potential materials “failures” Mechanical loads → stress ◦ Processing → may introduce residual stress Residual stress – heating – thermal expansion etc. Shot peening (beneficial) Again, verify ◦ Deformation Elastic Plastic (permanent) ◦ Buckling ◦ Fracture Chemical environment Wear
Temperature – high or low ◦ Thermal expansion and stress Varies with material ◦ Change in mechanical properties ◦ Change in lubricant performance ◦ Enable or accelerate chemical reactions E.g. Oxidation, changes in material
TESTING ESTABLISHES ABLISHES & QUANTI NTIFIES FIES ◦ Feasibility ◦ Product specifications TESTING VA VALIDAT DATES ES ◦ Product concepts - prototypes ◦ Product specifications ◦ Product performance ◦ Manufacturing processes ◦ Aging/wear-out mechanisms ◦ Failure modes TESTING MONITORS ITORS ◦ Manufacturing processes ◦ Product aging / wear ◦ Product performance
Standard properties and test methods ◦ Publicly available ◦ Or company standards ◦ Clear communication all along the supply chain Not handbook and similar “typical” or average properties. Not supplier typicals ◦ What happens when supplier changes?
ASTM (American Society for Testing and Materials) – 12,500+ documents ANSI (American National Standards Institute) 9,500+ documents SAE (Society for Automotive Engineers) 10,000+ documents IEEE (Institute of Electrical and Electronics Engineers) – 1,100+ documents
ISO (International Organization for Standardization) – 22,600+ documents International Electrotechnical Commission (IEC) – 9,000+ documents International Telecommunications Union (ITU) 4,000+ documents
Chemical composition ◦ Plastics less standardized than metals ◦ Plasticizers, additives for UV exposure Mechanical properties Heat treatment Microstructural requirements Non-destructive examination Manufacturing processes ◦ Including personnel, e.g. welding certifications Surface finish, coatings, friction Corrosion and wear resistance At temperatures of interest And more Control with test program
Materials Test procedures ◦ Match functional requirements Accredited laboratory Supplier certification with every order, if feasible ◦ Protect yourself and your company ◦ Avoid misunderstandings ◦ Keep on file
Component Sub-system System Full product Cyclic or peak load Accelerated durability Field performance Dormant state shelf life (e.g. airbags, oxygen system on aircraft, fire detection systems)
Functional testing Performance testing Reliability testing Environmental testing Mechanical testing Mean time between failures (MTBF) prediction ◦ Many product lives follow Weibull distribution ◦ Important for setting warranty terms Conformance testing Safety certification ◦ Determine useful life and factor of safety
Product Testing (Mechanical Lab/Field) ◦ Functional Testing ◦ Stress Testing ◦ Performance Testing ◦ Environmental Testing Materials Characterization (Analytical Lab) ◦ Analytical Chemistry ◦ Chemical composition and microstructure ◦ Microscopy ◦ Surface Analysis ◦ Mechanical Property Testing
Finite Element Analysis/Modeling (FEA) Experimental Stress Analysis ◦ Strain gages ◦ Various coatings Component Testing ◦ Prototype ◦ Early production System Testing ◦ Prototype ◦ Early production ◦ Audit
Powerful tool to evaluate design alternatives Inputs must match real world Material properties, grid size, boundary conditions, temperature, etc. Validate model with physical test to obtain correlation
Do the materials of construction ◦ Meet specification? ◦ Appropriate for the application? ◦ Behave as expected? Much can often be learned through examination of failed test specimens ◦ Loads ◦ Temperature ◦ Chemical environment ◦ Weld process ◦ Contact/witness marks, wear, etc. ◦ Assembly
Scientific Method – hypothesis testing ◦ Has anything changed? Many tests are destructive, so statistical analysis is necessary ◦ Integrate with Statistical Process Control (SPC), etc.
Yield ◦ Affected by temperature, strain rate Ultimate ◦ Affected by temperature In aggressive environment ◦ Stronger is not always better! Fatigue ◦ Affected by corrosion
* Force/Area Change / Original Length From Instron, one supplier of testing machines
Location is part of specification Separately manufactured test bars ◦ Castings, forgings, etc. ◦ Avoid misinterpretation – properties may vary Directionality may be important Hardness correlated with tensile strength ◦ Considered non-destructive
Goal – reproducible results – material property Specimen geometries (proportional) Test as received or after environmental exposure
Recommend
More recommend
