Materials Database

Subzero's Materials (250lber)

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This is a brief database of useful properties for commonly used materials within battlebots as well as some background information and peoples' experience working with them. Some material properties have not been included but feel free to add anything important. Material properties usually vary slightly for a given material from vendor to vendor so in the majority of cases, trust specs given by the manufacturer or supplier over the specs in this database when they are given. In addition, some of these material properties can vary slightly depending on the data source and also other details such as heat treatment and the kind of sample the material data was acquired from.

Steels

Steels are strong, dense, iron-carbon alloys which come in a variety of material compositions and treatment standards. A variety of major and minor alloying elements are added to improve certain material properties, including strength, toughness, corrosion resistance, or machinability. When selecting a grade of steel to use for your robot, consider how the material properties of the steel address the design requirements. Listed below are some more common grades of steel:

Abrasion-Resistant (AR) Steel

"AR" Steel, or "Abrasion Resistant" Steel is a high-strength, low carbon hardened alloy designed to resist wear and stress. The "grade" of the abrasion-resistant steel correlates to the Brinell hardness rating.

AR500 Steel

Type Carbon Steel Modulus of Elasticity 30,000 ksi Poisson's Ratio 0.29 Density 0.29 lb/in^3 Ultimate Tensile Strength 225 ksi Tensile Yield Strength 200 ksi Brinell Hardness 450 HB Rockwell Hardness C47-48 Elongation at Break 12% Charpy Impact (V-notch) 24.4J Familiar Sellers McMaster Carr, MakeItRingTargets, Alro Steel, SendCutSend

Material Description:

• High strength, high hardness, abrasion resistant steel used in body armor and shooting targets
• Generally considered to be tougher than S7 tool steel but has lower hardness
• Hardened steel is very difficult to machine, is typically only used for Waterjet parts
• No further heat treatment needed
• Typically used for weapons and wedges due to it's high strength, toughness, and relatively high hardness
• Used more commonly as armor in higher weight classes
• Anecdotal experience from builders says that AR500 typically bends before it fractures
• Will rust over time when wet or exposed to air
• Important to select a supplier which gives you specifications and complies with specification codes. AR steels are not tightly regulated so the actual hardness and depth of hardening (completely through-hardened vs surface hardened) may vary by supplier.
  • Technically supposed to be through hardened but many sketchier suppliers will sell AR500 that is effectively only surface hardened (up to 1/8" depth from surface according to Seth from JustCuzRobotics/BloodSport) with decreasing hardness with depth and a soft core. This doesn't matter much for thinner parts 1/4" or thinner but matters alot for thicker parts.

AR400 Steel

Type Carbon Steel Modulus of Elasticity XX ksi Shear Modulus XX ksi Poisson's Ratio XX Density XX lb/in^3 Ultimate Tensile Strength XX ksi Tensile Yield Strength XX ksi Fracture Toughness (Riobotz Sample) XX ksi-in½ Calculated Toughness XX J/in^2 Charpy Impact (V-notch) ~XX J Brinell Hardness XXXX HB Rockwell Hardness CXX Elongation at Break ~XX% Familiar Sellers McMaster, Online Metals

Tool Steel

Unlike abrasion-resistant or carbon steels, tool steels are specialized grades of steel used primarily for tool production and cutting bits. Added alloying elements such as Cr, V, Co, W, or Mo are added to greatly increase the strength and wear resistance of the steel, but tool steels tend to be more expensive than standard carbon steels.

S7 Tool Steel (at 54 HRC)

Type Carbon Steel Modulus of Elasticity 30,000 ksi Shear Modulus ksi Poisson's Ratio 0.29 Density 0.282 lb/in^3 Ultimate Tensile Strength 284.9 ksi Tensile Yield Strength 220.4 ksi Fracture Toughness (Riobotz Sample) 50.0 ksi-in½ Calculated Toughness 9.42 J/in^2 Charpy Impact (V-notch) 16.3 J Brinell Hardness 543 HB Rockwell Hardness C54 Elongation at Break 6.5% Familiar Sellers McMaster Carr, OnlineMetals

• Shock resisting tool steel that has high strength and high impact toughness
• Usually used in weapons but has been used by some NHRL builders for shafts but with hardnesses much lower than 54 HRC
• Is machined in its annealed form and then heat treated, quenched, and tempered to exactly 54 HRC which is a value recommended by the Riobotz Combot Tutorial pg 59-60.
• Ray Billings, builder of Tombstone, also endorses exactly 54 HRC for S7
• Anecdotal experience from other builders shows it fails through fracture before bending
• Considered to be less tough than AR500 and is commonly used when the higher hardness (C54 vs C48) is desired like for weapon teeth
• Extra important to avoid sharp internal corners and stress concentrations to prevent cracks from forming

AISI Alloy Steels

(description here)

AISI (43 HRC)

Type Carbon Steel Modulus of Elasticity 29,732 ksi Shear Modulus ksi Poisson's Ratio 0.29 Density 0.283 lb/in^3 Ultimate Tensile Strength 210.0 ksi Tensile Yield Strength 194.9 ksi Fracture Toughness (Riobotz Sample) 80.1 ksi-in½ Calculated Toughness 24.38 J/in^2 Charpy Impact (V-notch) ~19 J Brinell Hardness 402 HB Rockwell Hardness C43 Elongation at Break ~9.6% Familiar Sellers McMaster, Online Metals

• Ultra high strength steel that is machined in its annealed state and is heat treated by quenching and tempering it to a desired hardness.
• Riobotz's recommended hardness for shafts is 40-43 HRC which will allow it to fail by bending before breaking
• Is often used by some builders for other parts such as beaterbars at higher hardnesses
• Relatively expensive

AISI (-- HRC)

Type Carbon Steel Modulus of Elasticity XX ksi Shear Modulus XX ksi Poisson's Ratio XX Density XX lb/in^3 Ultimate Tensile Strength XX ksi Tensile Yield Strength XX ksi Fracture Toughness (Riobotz Sample) XX ksi-in½ Calculated Toughness XX J/in^2 Charpy Impact (V-notch) ~XX J Brinell Hardness XXXX HB Rockwell Hardness CXX Elongation at Break ~XX% Familiar Sellers McMaster, Online Metals

Aluminum Alloys

Aluminum Parts

Aluminum -T6

Type Aluminum Alloy Modulus of Elasticity 10,000 ksi Shear Modulus ksi Poisson's Ratio 0.33 Density 0. lb/in^3 Ultimate Tensile Strength 45 ksi Tensile Yield Strength 39 ksi Fracture Toughness (T-L dir) 26.4 ksi-in½ Calculated Toughness 7.88 J/in^2 Charpy Impact Test (V-notch) 21.7 J Brinell Hardness 93 HB Rockwell Hardness B52 Elongation at Break 10% Machinability (Vs. Steel) 270% Familiar Sellers McMaster Carr, Midwest Steel Supply, SendCutSend

Material Description:

• Lightweight aluminum alloy that comes already pre-heat-treated T6 temper which gives it its strength
• Beware of tempers T4 and O which are weaker than -T6
• Typically used for frame rails, plates, pulleys, and armor for some bots
• Tends to fail in bending before fracturing
• Tends to "ablate" and may take gashes when hit directly by weapons
• Easy to machine and relatively cheap

Aluminum -T6

Contact us to discuss your requirements of density of ar500 steel. Our experienced sales team can help you identify the options that best suit your needs.

Type Aluminum Alloy Modulus of Elasticity 10,000 ksi Shear Modulus ksi Poisson's Ratio 0.32 Density 0.102 lb/in^3 Ultimate Tensile Strength 81 ksi Tensile Yield Strength 69 ksi Fracture Toughness (T-L dir) 22.8 ksi-in½ Calculated Toughness 5.87 J/in^2 Charpy Impact Test (V-notch) 5.4 J Brinell Hardness 150 HB Rockwell Hardness B87 Elongation at Break 7.9% Machinability (Vs. Steel) 170% Familiar Sellers McMaster Carr, Midwest Steel Supply, SendCutSend

Material Description:

• Aerospace grade aluminum alloy which is much stronger and harder than -T6
• Pre-heat-treated to T6 temper
• Past and anecdotal experience notes that it tends to fracture before it bends as it's more brittle than
• Some builders recommend avoiding using it as armor or for parts that take direct hits due to fracture risk
• Relatively easy to machine
• More expensive than -T6

Aluminum -H32

Type Aluminum Alloy Modulus of Elasticity XX ksi Shear Modulus XX ksi Poisson's Ratio XX Density XX lb/in^3 Ultimate Tensile Strength XX ksi Tensile Yield Strength XX ksi Fracture Toughness (T-L dir) XX ksi-in½ Calculated Toughness XX J/in^2 Charpy Impact Test (V-notch) XX J Brinell Hardness XX HB Rockwell Hardness BXX Elongation at Break XX% Machinability (Vs. Steel) XX% Familiar Sellers McMaster Carr, Midwest Steel Supply, SendCutSend

Material Description:

Aluminum -T6

Type Aluminum Alloy Modulus of Elasticity XX ksi Shear Modulus XX ksi Poisson's Ratio 0.XX Density XX lb/in^3 Ultimate Tensile Strength XX ksi Tensile Yield Strength XX ksi Fracture Toughness (T-L dir) XX ksi-in½ Calculated Toughness XX J/in^2 Charpy Impact Test (V-notch) XX J Brinell Hardness XX HB Rockwell Hardness BXX Elongation at Break XX% Machinability (Vs. Steel) XX% Familiar Sellers McMaster Carr, Midwest Steel Supply, SendCutSend

Material Description:

Other Metal Alloys

Grade 5 Titanium (Ti-6Al-4V)

Type Titanium Alloy Modulus of Elasticity ksi Shear Modulus ksi Poisson's Ratio 0.32 Density 0.160 lb/in^3 Ultimate Tensile Strength 138-150 ksi Tensile Yield Strength 128-140 ksi Fracture Toughness (Annealed Plate) 67.9 ksi-in½ Calculated Toughness 31.5 J/in^2 Charpy Impact Test (V-notch) 17 J Brinell Hardness 310 HB Rockwell Hardness C34 Elongation at Break 6.7% Machinability (Vs. Steel) 20% Familiar Sellers McMaster Carr, SendCutSend, TMS Titanium

Material Description:

• Very high strength and high toughness metal alloy
• Denser than aluminum but less dense than steel. May destroy tools if you're not careful
• Typically sold and used in its annealed state for high toughness. No heat treatment needed.
• Typically used for armor, structural plates, sometimes weapons, it's pretty versatile material overall
• Known to fail in bending before failing in fracture
• Very expensive, more so than most steels and aluminum alloys
• Very difficult to machine or drill due to work hardening properties
• In some cases, outsourcing to SendCutSend might be financial preferable to buying Ti stock so discuss with your PM

Plastics and Polymers

Plastics and other polymerized materials are significantly less dense than metals, and are generally more machinable or formable.

Ultra-High-Molecular-Weight-Polyethylene (UHMW)

High-Density-Polyethylene (HDPE)

Polycarbonate

Carbon Fiber

Acrylonitrile Butadiene Styrene (ABS)

Polylactide Plastic (PLA)

Thermoplastic Polyurethane (TPU)

Sources

• AR500 Steel:
  • SendCutSend: https://sendcutsend.com/materials/ar500/
  • Steel Warehouse: https://www.steelwarehouse.com/ar500/
  • Team Caustic Creations: https://www.arrow.com/en/research-and-events/articles/battlebot-episode-2

• AR400 Steel:
  • source

• S7 Tool Steel:
  • Riobotz Combot Tutorial (Pg. 82): https://www.riobotz.com/riobotz-combot-tutorial
  • Ansys Granta Edupack (Not 54 HRC but some properties are close enough): https://drive.google.com/file/d/1aNH_X-EIR3ae4Uacl5s5DzcEWLtHAgMG/view?usp=sharing
  • Team Caustic Creations: https://www.arrow.com/en/research-and-events/articles/battlebot-episode-2

• AISI Steel (43 HRC):
  • Riobotz Combot Tutorial
  • 'The quantitative relationship between fracture toughness and impact toughness in high-strength steels': https://www.researchgate.net/publication/_The_quantitative_relationship_between_fracture_toughness_and_impact_toughness_in_high-strength_steels

• AISI Steel:
  • source

• Al -H32:
  • source

• Al -T6:
  • source

• UHMW:
  • source

• HDPE:
  • source

• Polycarbonate:
  • source

• Carbon Fiber:
  • source

• ABS:
  • source

• PLA:
  • source

• TPU:
  • source

Notes

Want more information on why are cars not made of stainless steel? Feel free to contact us.

• The charpy impact data provided by Team Caustic Creations was "quick and dirty" and was hard to verify
  • They didn't specify how they got the data and where from
  • Their value for Ti-6Al-4V was off from the Matweb data page so take it with a grain of salt
  • Charpy impact data is pretty hard to find. It might be worth it for RoboJackets to our own Charpy impact tests

• The Plastics and Polymers section does not distinguish the material property differences between machined stock pieces and extruded 3D prints. Because of the layer-by-layer extrusion of 3D printers, it is vital to note that the material strength is directionally dependent, and depends on the infill style and percentage infill.