Lesson

Lesson

Our goal is, that after this lesson, students are able to recognize the importance of affecting loading cases, optional manufacturing technologies and the reliability based aspects for material selection.

Note! The key for proper material selection based on the required strength properties is to recognize the affecting loading cases! Tensile Compression Bending Shear Combined loading Dynamic / static loading, fatigue Thermal loading, corrosion assisted loading

DIFFERENT LOADING CASES A= STATIC LOADING B= DYNAMIC LOADING/ PULSATING LOADING C= DYNAMIC LOADING/ REPEATED LOADING D= DYNAMIC LOADING/ ASYMMETRIC REVERSED LOADING E= DYNAMIC LOADING/ SYMMETRIC REVERSED LOADING TIME FORCE

LOADING CASE: PULSATING LOADING LOADING CASE: REVERSED LOADING σ a = stress amplitude σ m = mean stress σ σmσm σaσa σaσa t σ σmσm σaσa σaσa t σ a = stress amplitude σ m = mean stress

CASE: FATIGUE FAILURE OF A SPRING

DIMENSIONS - Effective cross- sectional area - Thickness, diameter - Geometrical restrictions - Weight GEOMETRY - Changes of cross- section areas - Joints - Groves, shoulders, threads holes, notches - Geometry related to the loading angle MATERIAL PROPERTIES - Tensile, compression, bending, torque - Fatigue failure - Strength, ductility - Notch sensitivity - Yeld strength ratio - Environmental conditions

Key seat Circlip seat Relief groove End of the worm gear thread

STRESS TEMPERATURE

1400 MPa 1800 MPa

TOTAL WEIGHT BODY WEIGHT FUEL CONSUMPTION CO 2 -EMISSIONS MANUFACTURING COSTS -10% -20% -5% -6% 0% -11% -3% -2% -3% + 65% EFFECTS OF CHANGING THE CAR BODY MATERIAL CHANGE: STEEL  AHSS-STEEL CHANGE: AHSS-STEEL  ALUMINIUM CHANGE % TOTAL WEIGHT BODY WEIGHT FUEL CONSUMPTION CO 2 -EMISSIONS MANUFACTURING COSTS

Note! Typically the increase of the strength of the material requires some compromises with other material properties! Remember that the increase of the strength of the material is NOT the only option to increase the strength of the construction! E.g. the by changing the direction of the affecting load some materials become acceptable (e.g. ceramic materials withstand compression loading better than tensile loading)

PROPERTIES GET WORSE STRENGHT RANGE DECREASES PROPERTIES GET WORSE PROPERTIES IMPROVE STRENGTH RANGE INCREASES MACHINABILITY HEAT CHANGE RESISTANCE ABILITY TO ABSORB VIBRATIONS CASTABILITY THINNEST POSSIBLE WALL THICKNESS SURFACE ROUGHNESS HEAT RESISTING STRENGTH MODULUS OF ELASTICITY WEAR RESISTANCE MACHINABILITY HEAT CHANGE RESISTANCE ABILITY TO ABSORB VIBRATIONS CASTABILITY THINNEST POSSIBLE WALL THICKNESS SURFACE ROUGHNESS HEAT RESISTING STRENGTH MODULUS OF ELASTICITY WEAR RESISTANCE COMPARISON OF CAST IRONS

Note! For objective and systematic material comparison and selection numerical characteristics are required to describe manufacturability: Machinability (cutting, milling, drilling etc.) Weldability Formability (bending, deep drawing etc.) Castability Aspects of powder metallurgy Aspects of polymer and composite technology

PRODUCT DESIGN OPTIONAL MATERIALS OF THE PRODUCT OPTIONAL MANUFACTURING TECHNOLOGIES CHARACTERISTICS FOR COMPARISON DETAILED DESIGN OF MANUFACTURING

MAXMAX MINMIN CHARACTERISTICS AND NUMERICAL VALUES TO DESCRIBE MACHINABILITY Cutting speed v, cutting depth a, feed s, wear of the cutting edge Cutting power P, cutting forces F, tolerance grade IT, surface roughness Ra, chip size

MATERIAL: ALUMEC® COPPER ALLOYED COLD-DRAWN ALUMINIUM ALLOY WITH HIGH STRENGTH AND GOOD MACHINABILITY EFFECTS OF CUTTING FORCES ON THE PERPENDICULARITY OF THE MW-FILTER’S RESONATOR PINS SHOULD BE TAKEN INTO CONSIDERATION IN MATERIAL SELECTION

Type of joint Heat input min/max Filler material Weld protection Suitability of the welding process Heat treatments Quality control Required actions before welding Welded product or material Required actions during welding Required actions after welding Effective welding time (burn time ratio) Joint and process preparations Groove preparations

F RIP GLUED SEAM F PEELING GLUED SEAM SURFACE LAYER BASIC MATERIAL (THE BODY) Example of glued components

MATERIAL A: THE ELONGATION OF BOTH PARTS IS L 3  L 4 STRETCHED SEAM L 1  L 2 (GLUED JOINT) L3L3 L4L4 L1L1 L2L2 F F

MATERIAL B THE ELONGNATION IS LARGER THAN IN MATERIAL A L 5  L 6 AND L 3 =L 5, BUT L 6 >L 4 STRETCHED SEAM L 1  L 2 (GLUED JOINT) L3L3 L4L4 L1L1 L2L2 F F MATERIAL A THE ELONGNATION IS L 3  L 4 L5L5 L6L6

F F The thickness ”a” of the glued seam Plate thickness ”t” Overlapping length ”l” Shear modulus ”G” of the glued seam Plate’s modulus of elasticity ”E”

F F τ max

χ × τ m / τ max

Basic material 1 Basic material 2 Glued seam Coating 1 Coating 2

Requirements profile Properties profile Deriving the necessary material properties of the glued seam from the requirements of the joint

Original milled MW-filter construction with the fitting joint of the SMA- connector pin Developed sheet metal construction with a glued joint Special geometry of the centre pin for the glued joint Glued joint (Elecolit® conductive adhesive)

Note! Sometimes optional materials can be selected by utilizing appropriate coatings for cost effective base materials Analogic to the previous glued joint of two different materials, the properties of the coating and the base material should be tuned to match with each other!

Material characteristics to describe material’s formability Smallest allowed bending radius r min Required number of forming stages Required forming force Required elevated forming temperature Smallest allowed wall thickness in deep drawing related to the drawing speed Produced maximum decrease of the cross- section [%] by one forming stage r min1 r min2 A2A2 A1A1 F req T 1 [°C] F T 2 [°C] F T 1 >> T 2 N= s min v, F

Note! Both the material properties and the affecting loads vary based on the given limits in material standards and during the different functional conditions! Therefore there is a real risk that the failure might take place when the material properties are at their minimum and the affecting load is at its maximum! Reliability based material selection offers a tool to estimate the probability of the failure risk.

Gathering the statistical data to describe the variation of the component’s load bearing capacity Gathering the statistical data to describe the load variation of the component Distribution curve fits for the variations of load and load bearing capacity Calculation of the wanted size of the overlapping area of the distributions to find out the reliability level Stage 1 Stage 2Stage 3Stage 4

DISTRIBUTION OF THE LOAD BEARING CAPACITY f(R) DISTRIBUTION OF THE AFFECTING LOAD f(S) RR SS ADAD STRESS RESISTANCE PROBABILITY f(S) f(R) ENDURANCE CONDITION R>S <

Parameter ƞ ”sharpness” Parameter β ”shape” Parameter γ ”position” 3-PARAMETER WEIBULL-DISTRIBUTION CURVE

 =1.17  =3.57 f(x) xoxo x THE SHAPE OF THE WEIBULL DISTRIBUTION CURVE WITH DIFFERENT SHAPE PARAMETER VALUES Almost normal distribution

FAILURE NORMAL DISTRIBUTION LOAD WEIBULL DISTRIBUTION MATERIAL PROPERTIES

TOOLS FOR RISK ANALYSIS Risk analysis of dangerous scenarios Effect tree analysis (ETA) Failure analysis Forecasting potential damages and failures Failure mode and effects analysis (FMEA) Reaction matrix Malfunction analysis Why-because analysis (WBA) and Cause-effect analysis (CEA) Fault tree analysis (FTA) Analysis of consequences