SME
Initiative
Materials properties requirements and associated test methods
for
metallic materials
ESA SME Initiative
Course D:Materials
Ton de Rooij
Principal Metallurgist
Materials and Processes Division
Product Assurance and Safety Department
Materials and Processes Division
ESA/ESTEC/TOS-QM
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SME
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Content of presentation
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Materials properties
Constraints on materials
Surface finishes
coatings
Joining
Corrosion testing
Mechanical testing
Macroscopic examination
Microscopic examination
Non-destructive examination
Failure analysis
Materials and Processes Division
ESA/ESTEC/TOS-QM
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Materials Properties
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Strength
Elastic modulus
Fatigue
Fracture toughness
Creep
Micro-yielding
Coefficient of thermal expansion
and coefficient of moisture
expansion
Stress corrosion
Corrosion fatigue
Hydrogen embrittlement
• Wear and fretting
• Surface finishes
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Anodising
Conversion
pickling/etching
mechanical
• Coatings
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hard
barriers
Materials and Processes Division
ESA/ESTEC/TOS-QM
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Metallic Materials used in space
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Light metals, such as beryllium, magnesium, aluminium and titanium
and their alloys
Steels, such as low-alloy, tool, corrosion resistant, precipitation
hardable, and maraging
Nickel and nickel base alloys, including pure nickel, Monel alloys,
Inconel alloys, and other nickel- and cobald-base superalloys
Refractory metals, principally niobium and molybdenum
Copper-base alloys, including pure coppers, beryllium coppers,
bronzes and brasses
Precious metals
Welding, brazing and soldering alloys
Various plating alloys
Materials and Processes Division
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Materials Properties cont..
• Fracture Toughness
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The fracture toughness is a measure of the damage
tolerance of a material containing initial flaws or
cracks. The fracture toughness in metallic materials
is described by the plain strain value of the critical
stress intensity factor. The fracture toughness
depends on the environment. Kic is the plain strain
critical stress intensity factor. Kiscc plain strain
critical stress intensity factor for a specified
environment in which environmentally induced
crack growth occurs.
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For homogeneous materials the Kic or Kiscc
shall be measured according to ECSS- Q- 7045.
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Metallic materials for use in corrosive surface
environments shall be tested for fracture
toughness under representative conditions
Typical subcritical crack propagation rate versus
stress intensity relationship. Stress intensity K, is
defined as K=A(C/B), where  is the total tensile
stress, C is the crack length, and A and B are
geometrical constants
Materials and Processes Division
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Initiative
Materials Properties cont..
• Coefficient of thermal expansion and coefficient of
moisture expansion
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The difference in thermal or moisture expansion between members of a construction or between the
constituents of a composite or a coated material can induce large stresses or strains and can
eventually lead to failures.
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The thermal mismatch between members shall be minimised to such a degree that stresses
generated in the experienced temperature domain are acceptable.
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The coefficient of thermal expansion (CTE) of composite materials intended for high stability structural
applications shall systematically be determined by means of dry test coupons and dry test conditions.
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For hygroscopic materials intended for high stability structural applications,the coefficient of moisture
expansion (CME) shall systematically be determined.
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For composite materials a sensitivity analysis shall be performed in relation with the inaccuracies due
to the manufacturing process.
Materials and Processes Division
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Materials Properties cont..
• Mechanical contact surface effects
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When clean surfaces are placed in contact they do not touch over the whole of their apparent area.
The load is supported by surface irregularities and the following interactions can occur:
• elastic or plastic deformation
• adhesion
• material transfer and removal
• heat transfer
• chemical reaction
• transformation of kinetic energy into heat energy
• diffusion/localised melting
For very clean surfaces strong adhesion occurs at regions of real contact, a part of which may be due
to cold-welding
The friction behaviour of polymers differs from that of metals. The surfaces left in contact under load
may creep and high local temperatures can be generated by frictional heating at regions of real
contact.
Wear is the progressive loss of material from the operating surface of a body occurring as a result of
relative motion at the surface. Wear is usually detrimental, but in mild form may be beneficial, e.g.,
during the running-in of engineering surfaces.
The major types of wear are abrasive wear, adhesive wear, erosive wear, rolling wear and fretting.
Materials and Processes Division
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Materials Properties cont..
• Stress Corrosion Cracking
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Stress corrosion maybe defined as the combined action of sustained tensile stress and corrosion that
may lead to the premature failure of materials. Certain materials are more susceptible than others. If
a susceptible material is placed in a corrosive environment under tension of sufficient magnitude, and
the duration of service is sufficient to permit the initiation and growth of cracks, failure will occur at a
stress lower than that which the material would normally be expected to withstand. The corrosive
environment need not be severe in terms of general corrosive attack.
Service failures due to stress corrosion are frequently encountered in cases where the surfaces of the
failed parts are not visibly corroded in a general sense.
If failure is to be avoided, the total tensile strength in service must be maintained at a safe level.
There is no absolute threshold stress for stress corrosion, but comparative stress-corrosion
thresholds can be determined for materials subjected to controlled conditions of test. Estimates of the
stress-corrosion threshold for a specific service application must be determined for each alloy and
heat treatment, using a test piece, stressing procedure and corrosive environment that are
appropriate for the intended service.
Materials and Processes Division
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Materials Properties cont..
• Stress corrosion
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Stress Corrosion Cracking (SCC), defined as the combined action of a sustained tensile stress and
corrosion, can cause the premature failure of metals. The metallic components proposed for use in
most spacecrafts must be screened to prevent failures resulting from SCC.
Only those products found to possess a high resistance to stress-corrosion cracking may have
unrestricted usage in structural applications.
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Materials intended for structural applications and likely to be exposed to a long-term terrestrial
storage or flown on the Space Transportation System, fracture critical items, all parts used or
associated with the fabrication of launch vehicles shall possess a high resistance to stress-corrosion
cracking.
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Structural products of a metallic nature shall be selected from the preferred list in Table I of ECSS- Q70- 36.
Materials and Processes Division
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Materials Properties cont..
Specimen orientation and fracture plane identification. L, length, longitudinal, principal direction of metal working (rolling, extrusion, axis of forging); T, width,
long-transverse grain direction; S, thickness, short-transverse grain direction; C, chord of cylindrical cross section; R, radius of cylindrical cross section. First letter:
normal to the fracture plane (loading direction); second letter: direction of crack propagation in fracture plane.
Materials and Processes Division
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Materials Properties cont..
• SCC table I
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Materials that testing and experience have shown to possess high resistance to stress- corrosion
cracking. Their use is given reference.
• SCC table II
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Alloys and tempers listed in table II are moderately resistant to stress- corrosion cracking. They
should be considered for use only in cases where a suitable alloy cannot be found in Table I.
• SCC table III
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Materials listed in table III have found to be highly susceptible to stress- corrosion cracking. They
should be considered for use only in applications where it can be demonstrated conclusively that the
probability of stress corrosion is remote because of low sustained tensile stress (whatever its origin)
in critical grain directions, suitable protective measures or an innocuous environment.
Materials and Processes Division
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Constraints on materials
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Temperature
Vacuum
Thermal cycling
Chemical (corrosion)
Galvanic compatibility
Atomic oxygen
Moisture absorption/desorption
Fluid compatibility
Materials and Processes Division
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Constraints on materials, cont..
• Temperature
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The range of temperatures experienced will play a large part in the materials selection. Extremes are
illustrated by the examples of cryogenic tanks and thermal protection systems for re-entry
applications. Temperatures below room temperature generally cause an increase in strength
properties, however the ductility decreases. Ductility and strength may increase or decrease at
temperatures above room temperature. This change depends on many factors, such as temperature
and time of exposure.
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Materials shall be compatible with the thermal environment to which they are exposed.
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Passage through transition temperatures (e.g., brittle-ductile transitions or glass transition
temperatures including the effects of moisture or other phase transitions) shall be taken into account.
Materials and Processes Division
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Constraints on materials cont..
• Thermal cycling
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Thermal cycling can induce thermal stresses and due to the difference in coefficient of thermal
expansion between fibres and matrix for composites and between base metal and coating microcracks can form which could jeopardise long-term properties.
• Materials subject to thermal cycling shall be assessed to ensure their capability to withstand the
induced thermal stresses and shall be tested according to ECSS- Q- 70- 04.
• Chemical (corrosion)
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The chemical environment to which a material is subjected in its life span may cause changes in the
material properties. Corrosion is the reaction of the engineering material with its environment with a
consequent deterioration in properties of the material. Corrosion will include the reaction of metals,
glasses, ionic solids, polymeric solids and composites with environments that embrace liquid metal,
gases, non-aqueous electrolytes and other non-aqueous solutions, coating systems and adhesion
systems.
Materials and Processes Division
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Constraints on materials cont..
• Galvanic compatibility
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If two or more dissimilar materials are in direct electrical contact in a corrosive solution or atmosphere
galvanic corrosion might occur. The less resistant material becomes the anode and the more resistant
the cathode. The cathodic material corrodes very little or not at all, while the corrosion of the anodic
material is greatly enhanced.
• Material compatibilities shall be selected in accordance with ECSS- Q-70-71,
• Maximum potential differences shall be in accordance with ECSS- Q-70-71,
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In the construction of a satellite, two metals that form a compatible couple may have to be placed in
close proximity to one another. Although this may not cause anomalies or malfunctions in the space
environment, it has to be borne in mind that spacecraft often have to be stored on earth for
considerable periods of time and that during storage they may inadvertently be exposed to
environments where galvanic corrosion can take place. In fact, this is known to have taken place on
several occasions and it is for this reason that the Agency has been studying the dangers involved.
• See also paragraph about Corrosion
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Constraints on materials cont..
• procedure
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a simplified procedure can be used to estimate the
compatibility of a bimetallic couple by taking into
account the difference between the two static potentials
of the materials involved.
The potentials were measured in a 3.5 % NaCl solution
representing a standard corroding atmosphere
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A difference in the static corrosion potential of the two
metals forming a bimetallic couple of less than 0.5 V is
acceptable if the item containing the couple is held in a
clean-room atmosphere at all times.
If the item containing the bimetallic couple is not held in
a clean-room atmosphere, the allowable difference in
static corrosion potential must be less than 0.25 V.
If it is not possible to follow guidelines 1 and 2, then it
will be necessary to provide for an insulation layer or
special packaging..
Materials and Processes Division
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Instrumentation setup for
electrochemical experiments
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Constraints on materials cont..
• Atomic oxygen
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Spacecraft in low earth orbit (LEO) at altitudes of between 200 km and 700 km are exposed to a flux
of atomic oxygen. The flux level varies with altitude, velocity vector and solar activity. The fluence
levels vary with the duration of exposure.
• Moisture absorption/desorption
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The properties of composite materials are susceptible to changes induced by the take-up of moisture.
Moisture absorption occurs during production of components and launch of the spacecraft, desorption
occurs in the space vacuum.
• Fluid compatibility
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In some occasions materials are in contact with liquid oxygen, gaseous oxygen or other reactive fluids
or could come into contact with such a fluid during an emergency situation.
Materials and Processes Division
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Interfaces (surfaces, layers)
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Anodising
Chemical conversion
metallic coatings (overlay and diffusion)
hard coatings
Diffusion barriers
High temperature oxidation protective coatings
Thermal barriers
Moisture barriers
coatings on CFRP
Materials and Processes Division
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Surface finishes
• The surface finish of a component can influence its
mechanical and environmental durability.
• Anodising (chromic, sulphuric, sulphuric+oxalic)
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Anodising is an electrolytic process for thickening and stabilising oxide films on base metals and
anodising grade alloys. It may be used as a pre-treatment for painting and dying or as a passivation
treatment for an electro-brightened surface.
Hard anodised layers are wear resistant and durable.
Black anodising with cobalt sulphide and nickel sulphide is used for controlling the optical properties
of surfaces.
• High solar absorptance, high emmitnace
The anodised layer is electrically non-conductive.
The bath constituents and process conditions may vary between organisations.
Caution should be exercised in anodising very thin products such as foils
Coatings are porous and needs sealing (coating can release water in vacuum)
Materials and Processes Division
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Surface finishes, cont..
• Chemical conversion (chromate, phosphate) –
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Commercial process (alodine , irridite, etc)
Chemical conversion depends upon the absorption of a protective metal oxide film into an existing
oxide film but may include non-metals in some cases.
Chromating involves the formation of a mixed metal-chromium oxide film. It has a good corrosion
resistance and an excellent bond to subsequent organic coatings.
Phosphating is primarily used as an underlayer for paint finishes. It finds little application for corrosion
protection.
Chemical conversion coatings can be either electrically conductive or non-conductive.
Temporary corrosion protection only
simple and cheap process
may be applied by immersion, praying, brushing, wiping or any other wetting method
Materials and Processes Division
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Coatings, cont..
• Metallic coatings (overlay and diffusion)
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Metallic overlay coatings can be applied in numerous ways to substrates (e.g. electroplating, chemical
evaporation and ion sputtering).
Metallic diffusion coatings modify the composition of the surface by enrichment with Cr, Al or Si and/or
formation of their stable oxides.
Cadmium and Zinc coatings shall not be used because of their high vapour pressure.
Silver, copper and osmium coatings shall not be used on external surfaces because they are sensitive
to atomic oxygen.
Electroplated tin can form whiskers
noble coatings such as gold and silver should be continuous (e.g. corrosion such as red plague)
• Hard coatings
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Hard coatings are used to improve the abrasive properties of the surface. Also, the ability to cold weld
is greatly reduced. The combination of a hard coating and a soft substrate is not desirable. The
coating can break under pressure.
• Diffusion barriers
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High temperature service operation can result in compositional changes of the bulk material and of
the coating due to diffusion. These compositional changes can result for example in formation of
intermetallic compounds, which are brittle and can break under cyclic stresses.
E.G. Cu or Ni layer as diffusion barrier between a brass (Cu-Zn) substrate and a Sn/Sn-Pb coating
Materials and Processes Division
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Coatings, cont..
evaporation
Materials and Processes Division
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Coating, cont..
Wear
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Coating, cont..
• Moisture barriers
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Coatings can be used to prevent moisture absorption or desorption of dimensionally stable structures
or to prevent the release of organic volatiles which could affect the performances of some
equipments.
• Coatings on CFRP
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Coatings on CFRP are used as moisture stoppers, as protection against atomic oxygen or for
adjusting optical properties. In most cases these coatings are metallic. In this dissimilar material
contact the CFRP usually behaves as the cathode and as such can corrodes the coating material.
• High Temp oxidation protective coatings (metallic)
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Protective coatings are important in high temperature applications, such as re-entry surfaces and
propulsion systems. Oxidation protection, thermal shock behaviour and erosion properties are
properties to consider.
• Thermal barriers (ceramic)
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Thermal barrier coatings are used to retard component overheating due to high heat fluxes. These
coatings are essentially ceramic overlay coatings, based on zirconia, where the coating thickness is
approximately 0.4 mm. They are applied to selected regions only. The coating process can modify the
condition of the substrate.
Materials and Processes Division
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Coating, cont..
• Depending on the design and service, the following
coatings are used:
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Paints
phosphate coatings
chromate coatings
electroless nickel
chromium, electroplated
oxides and black oxide
nickel/tin, electroplated
tin/lead
electroless nickel plus electroplated chromium
vapour-deposited aluminium
metals, such as gold, silver, palladium, rodium
lubrication coatings such as braycoat grease
molybdenum disulfide
carbides and nitrides or combination
Materials and Processes Division
ESA/ESTEC/TOS-QM
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Joining
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Mechanical fastening
Bonding
Combined bonding and fastening
Fusion, including welding, brazing, soldering and
diffusion bonding
Materials and Processes Division
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Joining cont..
• Bolted joints
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Bolts offer the greatest strength for mechanical fastened joints. Unless overtightened, no damage is
done to the structure during assembly.
Threaded fasteners shall conform to the minimum requirements of ECSS- E- 30- 07.
• Riveted joints
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Riveted joints are permanent. Disassembly requires removal of rivets by drilling out. Riveted joints
shall not be used where access to internal or adjacent parts of the structure is either needed or
expected.
• Inserts
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An insert system consists of a removable threaded fastener and a fixture embedded into the
honeycomb structure using a potting mass.
All inserts shall be surface protected to avoid corrosion
• Adhesive bonding
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The adhesives must attach the facings rigidly to the core to allow loads to be transmitted from one
facing to the other. Guidelines for adhesive bonding are found in ECSS- E- 30- 05.
Adhesives for load carrying structures shall have high strength and modulus. In addition, good
toughness and peel strength are important.
Materials and Processes Division
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Joining cont..
• Fusion techniques can be grouped as:
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soldering
brazing
welding, including diffusion bonding
• All fusion methods produce permanent joints.
Soldered, and some brazed joints may be
disassembled with care.
• All fusion techniques require extensive quality control
and inspection procedures.
Materials and Processes Division
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Joining cont..
• Soldering
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Soldering is commonly referred to as soft soldering in which low melting point alloys such as Tin-Lead
or Indium based alloys are used. Soldered joints are used for electrical and thermal conducting paths
and for low mechanical strength joints.
Soldering shall not be used for structural applications unless reviewed and approved by the
Customer.
See also next session
• Brazing
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Brazing is preferred to soldering in those cases where a strong joint, which is heat resistant is
required. As distinct from soft soldering brazing usually refers to joining with alloys of copper, silver
and zinc
• Welding
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Numerous welding techniques are available. In the aerospace industry the following techniques are
often used:
• Tungsten Inert Gas (TIG) welding
• Plasma-Arc welding
• Electron Beam (EB) welding , laser welding
• Resistance welding (induction, spot, seam welding), Diffusion welding
Materials and Processes Division
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Corrosion Testing
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General Corrosion
Stress Corrosion
Bimetallic Corrosion
Atomic Oxygen Corrosion
Red Plague Corrosion
Materials and Processes Division
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Corrosion-General
• Four systems for corrosion testing are available, each covering
a different area of corrosion evaluation
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Corrosion Units:
humidity test chamber, testing according to ASTM
salt spray test chamber, testing according to ASTM-B117
stress corrosion test rig, testing according to ASTM-G44
bimetallic corrosion set-up
atomic oxygen corrosion
red plague corrosion test unit, testing according to ESA PSS-01720
Materials and Processes Division
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General corrosion testing
Salt-spray-(foreground) and
Humidity Chamber- both
have temperature and
humidity regulators
Materials and Processes Division
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Stress corrosion testing
Al-Li stress corrosion
failure
Testing acc. to ESA
PSS-01-737
Test setup for the alternate immersion testing
of specimens in a 3.5% NaCl solution
Materials and Processes Division
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Bimetallic corrosion testing
The bimetallic
corrosion between
two materials can
tested in specific
liquids and under any
humidity levels.
The current and
voltage difference as
well as the EMK’s vs
Calomel as recorded
Materials and Processes Division
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Atomic Oxygen Corrosion
Materials for use in space
applications in low earth orbit and
exposed to the hostile combination
of atomic oxygen and thermal
cycling have to be screened for their
susceptibility to withstand this
environment over very long periods
Materials and Processes Division
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Red plague testing
Red plague testing (Anthony and Brown test) is performed according to ESA PSS01-720
Test conditions: 240 hrs at 58 oC
Materials and Processes Division
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Mechanical Testing
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Hardness testing
Tensile Testing
Compression testing
Fatigue testing
Fracture Toughness
Thermal cycling
Materials and Processes Division
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Mechanical Testing cont..
Load cells may be changed so that full
scale chart readings of between 2N and
100kN (maximum capacity) can be
achieved in both tension and
compression. This equipment will
investigate the mechanical properties of
all materials at temperatures ranging from
-150oC to +300oC
General view of Instron tensile test
equipment with custom built
environmental chamber, chart
recorder and control panel
Materials and Processes Division
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Mechanical Testing cont..
This equipment is more particularly
dedicated to the testing of thermostructural materials such as CMC
materials. It has been set up for
measuring tensile properties from
ambient temperature up to 1600oC under
air. Such a test is recognised to be the
most important for evaluating mechanical
properties of CMC.
A ceramic matrix composite specimen is
clamped into self-aligning water cooled
grips. It passes through a specially
designed furnace able to heat its
calibrated section to 1600oC. A high
temperature capacitive extensometer
made of ceramics probes permit strain
measurements.
Materials and Processes Division
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Mechanical Testing cont..
Two units, specially designed according to
to specification ESA PSS-01-704, operate
under vacuum. Two other units operate
under atmospheric pressure. The heating
and cooling is provided by nitrogen gas.
One of the two systems for
thermal cycling under vacuum
(VMDI is shown). The system is
provided with viewing ports and
electric feed through connection.
Materials and Processes Division
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Macro/Microscopic Examination
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Macroscopic (< X75)
Light microscopy
Confocal microscopy
Scanning Electron Microscopy
Materials and Processes Division
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Macroscopic Examination
Magnification < x75
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Visual Inspection
Stereozoom
Scanning Electron Microscopy at low
magnification
Photography
The diversity of samples submitted for
failure analysis is illustrated by this
photograph, which features part of a
defective spacecraft antenna, a nickel
cadmium battery cell, detector
electrodes, printed circuit boards,
fracture toughness specimen, part of a
dip brazed waveguide, sections through
a solar army hydrogen embrittled
springs and a composite structure
designed to withstand the impact of
particles travelling at 60 km/s.
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Microscopic Examination cont..
• Light Microscopy
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metallurgical microscopy
Optical Microscopes Reichert MeF2:
magn. X1 to X1500, It includes:
interferometer, polarised light
illumination, micro-hardness tester
Reichert MeF3a: magn. X1 to 1500
It includes: polarised light
illumination, dark and bright field
illumination, connection to Clemex
Image analyser
Materials and Processes Division
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Microscopic Examination cont..
Confocal microscopy
Confocal microscopy allows the us to obtain
depth-selective information on the threedimensionial structure of a microscopic object.
LEICA TCS NT with microscope
DM-RXE and galvanometer driven
Z-stage.
The x/y resolution is 0.18 m
(FWHM) and a corresponding zresolution of better than 0.35 m
(FWHM) at 488 nm
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Microscopic Examination cont..
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In many situations even greater
magnifications are useful. This capability
is provided by two Scanning Electron
Microscopes (SEM) which can magnify to
X200 000 with good resolution. (JEOL
T300 and Cambridge S360). The great
depth of field of these instruments and
the large specimen chamber of one of
these SEM's has made them particularly
useful in examining rough fracture
surfaces to determine the cause of a
component failure.
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View on Scanning Electron
Microscope Cambridge S360
Materials and Processes Division
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Non-Destructive Examination
• Scanning Laser Acoustic Microscopy (SLAM)
• C- Mode Scanning Acoustic Microscopy (C-SAM)
• Radiography (in TOS-QC)
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Non-Destructive Examination cont..
The Scanning Laser Acoustic Microscopy
(SLAM) produces images of the internal
structure of metals, ceramics and even
biological tissues, and these are
displayed in real time on a TV monitor.
The SLAM uses very high frequency
ultrasound in a transmission mode to
produce images. Acoustic waves are
transmitted into the bottom face of the
cell sample by means of a distilled-water
coupling medium. Using this instrument it
was possible to assess the quality of
solar cell interconnectors for the Space
Telescope.
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet47
SME
Initiative
Failure Analysis
• Under control of Material Review Board (MRB)
•
•
•
•
•
•
•
•
•
•
Collection of background data
visual examination
selection, identification, preservation of specimens
macroscopic examination and analysis
microscopic examination and analysis
metallographic sections examination
failure mechanism
chemical analysis
simulated testing
report
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet48
SME
Initiative
Materials Properties
annex cont..
• Corrosion fatigue
–
Corrosion fatigue indicates crack formation and propagation caused by the effect of alternating
loading in the presence of a corrosion process. Because of the time dependence of corrosion, the
number of cycles to failure depends on frequency. Since chemical attack requires time to take effect,
its influence is greater as the frequency becomes lower. No metals or alloys demonstrate complete
resistance to corrosion fatigue.
• Same requirement as with fatigue
• Hydrogen embrittlement
–
Metals can be embrittled by absorbed hydrogen to such a degree that the application of the smallest
tensile stress can cause the formation of cracking. The following are possible sources of hydrogen:
thermal dissociation of water in metallurgical processes (e.g., casting and welding), decomposition of
gases, pickling, corrosion, galvanic processes (e. g. plating) and ion bombardment.
• The possibility of hydrogen embrittlement during component manufacture and/or use shall be
assessed
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet49
SME
Initiative
Materials Properties
annex cont..
• Strength
–
Spacecraft design covers the survival of the structure under the worst feasible combination of
mechanical and thermal loads. All events of the complete lifetime of the spacecraft are addressed by
this design. The strength of a material is highly dependant on the direction as well as on the sign of
the applied load, e.g., axial tensile, transverse compressive, and others.
• positive margin of safety and shall include, if applicable, yield load analysis, ultimate load
analysis and bucking load analysis
• Elastic modulus
–
The elastic modulus defined as the ratio between the uniaxial stress and the strain (e.g., Young’s
modulus, compressive modulus, shear modulus) is for metals and alloys weakly dependant on heattreatment and orientation. However, for fibre reinforced materials, the elastic modulus depends on the
fibre orientation.
• For composites the required elastic modulus shall be verified.
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet50
SME
Initiative
Materials Properties
annex cont..
• Fatigue
–
Fatigue fracture can form in components which are subjected to alternating stresses. These stresses
may lie far below the allowed static strength of the material.
• For components experiencing alternating stresses, demonstration of the degradation of material
properties over the complete mission
• Fracture toughness
–
The fracture toughness is a measure of the damage tolerance of a material containing initial flaws or
cracks. The fracture toughness in metallic materials is described by the plain strain value of the
critical stress intensity factor. The fracture toughness depends on the environment. Kic is the plain
strain critical stress intensity factor. Kiscc plain strain critical stress intensity factor for a specified
environment in which environmentally induced crack growth occurs.
• Metallic materials for use in corrosive surface environments shall be tested for fracture
toughness under representative conditions
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet51
SME
Initiative
Materials Properties
annex cont..
• Creep
–
Creep is a time-dependant deformation of a material under an applied load. It usually occurs at
elevated temperature, although some materials creep at room temperature. If permitted to continue
indefinitely, creep terminates in rupture. Extrapolations from simple to complex stress-temperaturetime conditions are difficult.
• Testing under representative service conditions is necessary when creep is likely to occur.
• Micro-yielding
–
Some materials may exhibit residual strain after mechanical loading. The micro-yield is the force to be
applied to get a residual strain of 1x10-6 m/m along the tensile or compression loading direction. In
general, the most severe mechanical loading occurs during launch.
• Where dimensional stability requirements have to be met, micro-yielding shall be assessed.
• When it is likely to occur, testing and analysis in relation with the mechanical loading during the
life cycle of the hardware shall be performed.
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet52
SME
Initiative
Stress Corrosion Cracking, cont..
The relative influences of electrochemical and mechanical factors in
the corrosion and SCC damage of a susceptible material. The
shaded area represents the transition of driving force from
dominance by electrochemical factors to chiefly mechanical factors.
Precise separation of initiation and propagation stages is
experimentally difficult. Stimulation of cracking by atomic hydrogen
may also become involved in this transition region.
Effect of stress intensity on the kinetics of SCC.
Stages I and II may not always be straight lines but
may be strongly,curved, and one or the other may
be absent in some systems. Stage III is of little
interest and is generally absent in K-decreasing
tests.
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet53
SME
Initiative
Stress Corrosion Cracking, cont
Mean breaking stress versus exposure time for short-transverse 3.2-mm (0. 1 25-in.) diam aluminium alloy 7075 tension
specimens tested according to ASTM G 44 at various exposure stress levels. Each point represents an average of five
specimens.
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet54
SME
Initiative
Stress Corrosion Cracking, cont..
Effect of temper on SCC performance of aluminum
alloy 7075 subjected to alternate immersion in 3.5%
NaCl solution at a stress of 207 MPa (30 ksi). Mean
flaw depth was calculated from the average breaking
strength of five specimens subjected to identical
conditions. Source: Ref 17
Influence of specimen configuration on SCC test
performance (alternate immersion in 3.5% sodium chloride
per ASTM G 44). Aiuminum alloy 7075-T7X51 specimens
stressed 310 MPa (45 ksi); each point represents 60 to 90
specimens. Source: Ref 18
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet55
SME
Initiative
SCC Table I - Steel Alloys
Alloy
Carbon steel(1000 series)
Low alloy steel(4130,4340 etc)
(E) D6AC, H-11
Music wire(ASTM 228)
HY-80 steel
HY-130 steel
HY-140 steel
1095 spring steel
300 series stainless steel(unsensitised)2
400 series ferritic stainless steel
21-6-9 stainless steel
Carpenter 20 Cb Stainless steel
Carpenter 200 Cb-3 stainless steel
A286 stainless steel
AM350 stainless steel
AM355 stainless steel
Almar 362 stainless steel
Custom 450 stainless steel
Custom 455 stainless steel
15-5 PH stainless steel
PH 14-8 Mo stainless steel
PH 15-7 Mo stainless steel
17-7 PH stainless steel
Nitronic 33 (3)
(E) Maraging steel MARVAL X12
Condition
Below 125 kg/mm2; (180 ksi) UTS
Below 125 kg/mm2; (180 ksi) UTS (1)
Below 148 kg/mm2; (210 ksi) UTS
cold drawn
Quenched and tempered
Quenched and tempered
Quenched and tempered
Quenched and tempered
All
All
All
All
All
All
SCT 1000(4) and above
SCT 1000 and above
H1000 (5) and above
H1000 and above
H1000 and above
H1000 and above
CH900 and SRH950 and above (6,7)
CH900
CH900
All
All
Materials and Processes Division
ESA/ESTEC/TOS-QM
1) A small number of laboratory failures
of specimens cut from plate more than 2
inches thick have been observed at 75%
yield, even within this ultimate strength
range. The use of thick plate should
therefore be avoided in a corrosive
environment when sustained tensile stress
in the short transverse direction is
expected.
2) Including weldments of 304L, 316L,
321 and 347.
3) Including weldments.
4) SCT 1000 = sub-zero cooling and
tempering at 538&#176;C (1000F)
5) H1000 = hardened above 538C (1000F)
6) CH900 = cold worked and aged at
480C (1000;F)
7) SRH950 = solution treated and
tempered at 510C (950F)
(E) ESA classification - not in NASA
MSFC-SPEC-522A
sheet56
SME
Initiative
SCC Table I - Nickel Alloys
Alloy
Condition
Hastelloy C
Hastelloy X
Incoloy 800
Incoloy 901
Incoloy 903
Inconel 600 (3)
Inconel 625
Inconel 718 (3)
Inconel X-750
Monel K-500
NiSpan -C 902
Rene 41
Unitemp 212
Waspaloy
All
All
All
All
All
Annealed
Annealed
All
All
All
All
All
All
All
3) Including weldments
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet57
SME
Initiative
SCC Table I - Aluminium Alloys
Alloy,
Wrought(1,2)
Alloy, 1000 series
2011
2024, rod bar
2219
(E) 2419
(E) 2618
3000 series
5000 series
6000 series
(E)7020
7049
7149
7050
7075
7475
Condition
Cast (3)
Condition
All
355.0, C355.0
T6
356.0, A356.0
All
T8
357.0
All
T8
B358.0 (Tens-50)
All
T6, T8
359.0
All
T8
380.0, A380.0
As cast
T6, T8
514.0 (214)
As cast (5)
518.0 (218)
As cast (5)
All
535.0
(Almag
35)
As cast (5)
All (4,5)
A 712.0, C 712.0
As cast
All
T6 (6)
T73
T73
T73
T73
T73
1) Mechanical stress relieved (TX5X or TX5XX) where possible
2) Including weldments of the weldable alloys.
3) The former designation in shown in parenthesis when significantly different.
4) High magnesium content alloys 5456, 5083 and 5086 should be used only in controlled tempers (H111, H112, H116, H117, H323, H343) for
resistance to stress-corrosion cracking and exfoliation
5) Alloys with magnesium content greater than 3.0% are not recommended for high temperature application, 66C (150F) and above.
6) Excluding weldments.
(E) ESA classification - not in NASA MSFC-SPEC-522A
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet58
SME
Initiative
SCC Table I - Copper Alloys/ Misc. Alloys
CDA no (1)
110
170
172
194
195
230
422
443
510
521
619
619
688
706
725
280,524,606
632,655,705
710,715
(E)917, (E)937
Condition (% cold rolled) (2)
37
AT, HT (3)
AT, HT (3)
37
90
40
37
10
37
37
40(9% B phase)
40(95% B phase)
40
50
50, annealed
0
0
0
0
Alloy
Beryllium, S-200C
HS 25 (L605)
HS 188
MP35N
Titanium 3Al-2.5V
Titanium 6Al-4V
Titanium 13V-11Cr-3Al
(E)Titanium OMI 685, IMI 829
Magnesium, M1A Magnesium,
LA141 Magnesium, LAZ933
Condition
Annealed
All
All
All
All
All
All
All
All
Stabilised
All
1) Copper Development Association alloy number
2) Maximum per cent cold rolled for which stress-corrosion cracking data are available
3) AT = annealed and precepitation hardened, HT = work hardened and precepitation hardened
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet59
SME
Initiative
SCC Table II - Steel Alloys/Miscellaneous alloys
Alloy
Carbon steel (1000 series)
Low-alloy steel (4130,4340 etc)
Nitronic 32
Nitronic 60
400 series martensitic stainless steel (except 440)
PH 13-8 Mo stainless steel
15-5 PH stainless steel
17-4 PH stainless steel
Condition
1225 to 1370 MPa UTS
1225 to 1370 MPa UTS
All
All
(1)
All
Below H1000 (2)
All
1) Tempering between 370 and 600C should be avoided because corrosion and stress-corrosion resistance is lowered.
2) H1000 = hardened above 538C (1000F).
Alloy
Magnesium AZ31B
Magnesium ZK60A
Magnesium (E) ZW3
Condition
All
All
All
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet60
SME
Initiative
SCC Table II - Aluminium Alloys(1,2)
Alloy, wrough
2024 rod, bar, extrusion
2024 plate, extrusions
2124 plate
2048 plate
4032
5083
5086
5456
7001
(E) 7010
7049
7050
7075
7175
7475
7178
(E) Russian Al-Li 1420, 1421
Condition
T6, T62
T8
T8
T8
T6
All (3)
All (3)
All (3)
T75, T76
T74
T76
T74, T76
T76 T74,
T76
T76
T76
soln. treat+age
Alloy, cast
319.0, A319.0
333.0, A333.0
Condition
As cast
As cast
1) Mechanically stress relieved products (TX5X or TX5XX) should be
specified where possible.
2) Sheet, unmachined extrusion and unmachined plate are the most resistant
forms.
3) Except for controlled tempers listed in footnote 3 of Table I, aluminium
alloys. These alloys are not recommended for high-temperature applications.
66C (150F) and above.
(E) ESA classification - not in NASA MSFC-SPEC-522A.
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet61
SME
Initiative
SCC Table III - Steel Alloys
Alloy
Carbon steel(1000 series)
Low alloy steel(4130,4340 etc)
(E) D6AC, H-11steel
440C stainless steel
18 Ni Maraging steel, 200 grade
18 Ni Maraging steel, 250 grade
18 Ni Maraging steel, 300 grade
18 Ni Maraging steel, 350 grade
AM 350 stainless steel
AM 355 stainless steel
Custom 455 stainless steel
PH 15-7 Mo stainless steel
17-7 PH stainless steel CH900
(E) Kovar
Condition
Above 1370 Mpa UTS
Above 1370 Mpa UTS
Above 1370 Mpa UTS
All
Aged at 900F
Aged at 900F
Aged at 900F
Aged at 900F
Below SCT 1000
Below SCT 1000
Below H1000
All except CH900
All except CH900
All
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet62
SME
Initiative
SCC Table III - Aluminium Alloys
Alloy, Wrought (1,2)
2011
2014
2017
2024
2024 Forgings
2024 Plate
(E) Al-Li 2080
(E) 2618
7001
7005
(E) 7020
7039
7075
7175
7079
7178
7475
(E) Al-Li 8090
(E) BS L93
(E) Russian Al-Li 1441, 1460
Condition
T3, T4
All
All
T3, T4
T6, T62, T8
T62
T8
T3, T4
T6
All
Weldments
All
T6
T6
T6
T6
T6
All
T6
All
Alloy
295.0 (195)
B295.0 (B195)
520.0 (220)
707.0 (607, tern-alloy 7)
D712.0 (D612, 40E)
Condition
T6
T6
T4
T6
As cast
1) Mechanical stress relieved (TX5X or TX5XX) should be specified where possible.<br>
2) Sheet, unmachined extrusion and unmachined plate are the least susceptible forms.<br>
(E) ESA classification - not in NASA MSFC-SPEC-522A.
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet63
SME
Initiative
SCC Table III - Copper Alloys/ Magnesium alloys
CDA no (1)
260
353
443
672
687
762
766
770
782
Condition (% cold rolled) (2)
50
50
40
50, annealed
10, 40
A, 25, 50
38
38, 50, annealed
50
Alloy
Magnesium AZ61B
Magnesium AZ80A
Magnesium WE54
Magnesium ZCM711
Condition
All
All
All
All
1) Copper Development
Association alloy number
2) Rating based on listed
conditions only
Materials and Processes Division
ESA/ESTEC/TOS-QM
sheet64