4.1 Properties of Materials
Essential idea:
Materials are selected for manufacturing products based primarily on their properties.
Nature and Aims of Design
Nature of Design
The rapid pace of scientific discovery and new technologies has had a major impact on material science, giving designers many more materials from which to choose for their products. These new materials have given scope for “smart” new products or enhanced classic designs. Choosing the right material is a complex and difficult task with physical, aesthetic, mechanical and appropriate properties to consider. Environmental, moral and ethical issues surrounding choice of materials for use in any product, service or system also need to be considered. (2.1)
Aims
Aim 2: Materials are often developed by materials engineers to have specific properties. The development of new materials allows designers to create new products, which solve old problems in new ways. For example, the explosion of plastic materials following the second world war enabled products to be made without using valuable metals.
Guidance
As DP Design Technology student you should:
Understand and identify the Physical properties: mass, weight, volume, density, electrical resistivity, thermal conductivity, thermal expansion and hardness
Understand and Identify Mechanical properties: tensile and compressive strength, stiffness, toughness, ductility, elasticity, plasticity, Young’s modulus, stress and strain
Understand and Identify Aesthetic characteristics: taste, smell, appearance and texture
Properties of smart materials: piezoelectricity, shape memory, photochromicity, magneto-rheostatic, electro-rheostatic and thermoelectricity
Guidance:
Design contexts where physical properties, mechanical properties and/or aesthetic characteristics are important
Design contexts where properties of smart materials are exploited
Using stress/strain graphs and material selection charts to identify appropriate materials
Korean text
Summary
제조에서 재료 선택은 특성과 동작에 기반합니다.
디자이너는 재료를 선택할 때 물리적, 미적, 기계적 및 적절한 특성을 고려합니다.
재료 엔지니어는 문제를 해결하기 위해 특정 속성을 가진 새로운 재료를 개발합니다.
재료의 특성을 이해하는 것은 디자이너가 혁신적인 제품을 만들 수 있도록 도와줍니다.
물리적 특성에는 질량, 무게, 부피, 밀도 및 전기 저항이 포함됩니다.
기계적 특성에는 인장 강도, 압축 강도, 강성, 인성 및 연성이 포함됩니다.
모양, 형태, 소리, 냄새, 질감 및 외관과 같은 미적 특성은 중요합니다.
압전 및 열전 효과와 같은 스마트 재료는 새로운 디자인 가능성을 제공합니다.
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제조업의 세계에서는 소재는 그들의 특성에 따라 선택됩니다. 디자이너들은 제품에 대한 소재를 그들의 행동 방식과 능력에 따라 선택합니다. 과학적 발견과 새로운 기술은 우리에게 혁신적인 제품과 개선된 디자인을 만들 수 있는 다양한 소재를 제공해 주었습니다. 그러나 적절한 소재를 선택하는 것은 쉽지 않습니다. 디자이너들은 자신들의 결정을 내릴 때 물리적, 미적, 기계적 및 적절한 특성을 고려해야 합니다. 그들은 또한 사용하는 소재와 관련된 환경, 도덕 및 윤리적 문제에 대해 생각해야 합니다.
소재 엔지니어들은 특정 특성을 가진 새로운 소재를 개발하는 데 있어서 중요한 역할을 합니다. 이를 통해 디자이너들은 과거의 문제에 대한 새로운 해결책을 찾을 수 있습니다. 예를 들어, 제2차 세계 대전 이후 플라스틱 소재의 개발로 귀중한 금속을 사용하지 않고 제품을 만들 수 있게 되었습니다.
디자인 기술 학생으로서, 소재의 다양한 특성을 이해하고 식별하는 것이 중요합니다. 이에는 질량, 무게, 부피, 밀도, 전기 저항성, 열 전도도, 열 팽창률 및 경도와 같은 물리적 특성이 포함됩니다. 인장 및 압축 강도, 강성, 인성, 연성, 탄성, 가소성, 영률, 응력 및 변형과 같은 기계적 특성도 고려해야 합니다. 또한 맛, 냄새, 외관 및 질감과 같은 미적 특성도 고려해야 합니다. 마지막으로, 피에조전기, 형상 기억 합금, 광변색, 자기유변유체, 전기유변유체 및 열전기와 같은 독특한 특성을 가진 스마트 소재도 있습니다.
디자인할 때, 프로젝트와 관련된 물리적 특성, 기계적 특성 및 미적 특성을 고려하는 것이 중요합니다. 스마트 소재가 디자인에 어떻게 활용될 수 있는지 탐색하는 것도 중요합니다. 응력/변형 그래프와 소재 선택 차트는 프로젝트에 가장 적합한 소재를 식별하는 데 도움이 될 수 있는 도구입니다.
디자이너들은 성공적인 디자인을 위해 소재의 특성에 대한 깊은 이해가 필요합니다. 성공적인 제품의 결과로써 이 지식을 활용하여 새롭고 혁신적인 것을 만들어냅니다. 많은 요소들을 고려해야 하는 복잡한 과정이지만, 성공적인 제품을 만들기 위해 필수적입니다.
소재의 물리적 특성에는 질량, 무게, 부피, 밀도 및 전기 저항성이 포함됩니다. 이러한 특성은 우리가 다른 소재를 이해하고 설명하는 데 도움을 줍니다. 질량은 물체 내의 물질의 양을 나타내며, 무게는 중력에 의해 물체에 가해지는 힘을 나타냅니다. 부피는 소재가 차지하는 공간의 양을 나타내며, 밀도는 질량과 부피 사이의 관계를 나타냅니다. 전기 저항성은 소재의 전기를 전도하거나 저항하는 능력을 측정합니다.
소재의 기계적 특성은 일반적으로 파괴적인 시험을 통해 측정됩니다. 인장 강도는 소재가 당기는 힘에 대한 저항력을 측정하며, 압축 강도는 밀어넣는 힘에 대한 저항력을 측정합니다. 강성은 물체가 굽히는 것에 대한 저항력을 나타내며, 인성은 충격에 의해 균열이나 파괴 없이 변형될 수 있는 능력을 나타냅니다. 연성은 소재가 철사 모양으로 끌어내거나 압출될 수 있는 능력을 나타냅니다.
디자이너들은 또한 소재의 형태, 형상, 소리, 냄새, 질감 및 외관과 같은 미적 특성도 고려해야 합니다. 다른 사용자들은 이러한 특성을 다르게 인식할 수 있으므로, 그들이 어떻게 해석될지 고려하는 것이 중요합니다. 피에조전기, 형상 기억 합금, 광변색, 자기유변유체, 전기유변유체 및 열전기와 같은 스마트 소재는 디자인에 새롭고 혁신적인 가능성을 제공할 수 있습니다.
열전기는 두 개의 다른 도체가 열이 가해질 때 전기를 생산할 수 있는 개념입니다. 이는 우주 탐사선이나 전기 자동차와 같은 발전 및 냉각에 응용됩니다.
Chinese text
Summary
制造业中的材料选择是基于其性质和行为。
设计师在选择材料时考虑物理、美观、机械和适当的性质。
材料工程师开发具有特定性能以解决问题的新材料。
了解材料性能有助于设计师创造创新产品。
物理性质包括质量、重量、体积、密度和电阻率。
机械性能包括抗拉强度、抗压强度、刚度、韧性和延展性。
形状、形式、声音、气味、质地和外观等美学性质非常重要。
压电和热电等智能材料为新的设计可能性提供了机会。
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在制造业的世界中，材料的选择是基于它们的特性。设计师根据材料的行为和功能来选择产品所用的材料。科学发现和新技术为我们提供了各种各样的材料，使创新产品和改进设计成为可能。然而，选择合适的材料并不容易。设计师在做出决策时必须考虑物理、美学、机械和适用性等特性。他们还需要考虑与所使用材料相关的环境、道德和伦理问题。
材料工程师在开发具有特定特性的新材料方面起着至关重要的作用。这使得设计师能够为旧问题提出新解决方案。例如，二战后，塑料材料的发展使得可以在不使用有价值的金属的情况下制造产品成为可能。
作为一名设计技术学生，了解和识别不同材料的特性非常重要。这包括质量、重量、体积、密度、电阻率、热导率、热膨胀和硬度等物理特性。机械特性，如抗拉强度、抗压强度、刚度、韧性、延展性、弹性、塑性、杨氏模量、应力和应变也是需要考虑的重要因素。此外，还应考虑审美特征，如口感、气味、外观和质地。最后，还有具有独特特性的智能材料，如压电效应、形状记忆、光致变色、磁流变、电流变和热电效应。
在设计过程中，考虑与项目相关的物理特性、机械特性和审美特征至关重要。探索智能材料在设计中的应用也很重要。应力/应变图和材料选择图可以帮助识别最适合项目的材料。
设计师需要深入了解材料特性，以选择最适合他们设计的材料。成功的设计往往是利用这些知识创造出新的创新产品的结果。这是一个复杂的过程，涉及考虑许多因素，但对于创造成功的产品至关重要。
材料的物理特性包括质量、重量、体积、密度和电阻率。这些特性帮助我们了解和描述不同的材料。质量指的是物体中的物质量，而重量是由于重力而施加在物体上的力。体积指的是材料所占据的空间量，而密度是质量和体积之间的关系。电阻率测量材料导电或抵抗电流的能力。
材料的机械特性通常通过破坏性测试来测量。抗拉强度测量材料对拉力的抵抗能力，而抗压强度测量材料对推力的抵抗能力。刚度是物体抵抗弯曲的能力，而韧性是在冲击下变形而不开裂或断裂的能力。延展性指的是材料被拉伸或挤压成线状形式的能力。
设计师还需要考虑材料的审美特性，如形状、形式、声音、气味、质地和外观。不同的用户可能会以不同的方式感知这些特性，因此考虑它们的解释方式非常重要。智能材料，如压电效应、形状记忆合金、光致变色、磁流变流体、电流变流体和热电效应，可以为设计提供新的创新可能性。
热电效应是指当施加热量时，两种不同的导体可以产生电力。这在发电和制冷方面有应用，例如在航天探测器和电动汽车中。
Concepts and Principles
Designers need to understand the properties of materials in order to select the most appropriate material to meet their design goals. Very successful designs leverage this knowledge to innovate. Through understanding the properties of materials and the related manufacturing processes, the design can be optimized to take advantage of the material. This is a complex process, with many factors to consider.
Physical Properties of Materials
The physical properties of materials are those that can be measured using non-destructive testing.
Mass
*Weight and Mass are often confused and used interchangeably.
The amount of matter contained in a space. Mass is constant and is measured in kg.
The mass of an object is constant, regardless of where it is measured. A 2kg object on Earth will have the same mass of 2kg on Mars.
Design Context:
From the perspective of ergonomics and performance, weight can be a very improtant factor. Bicycle frames, for instance, must balance weight with other factors such as stiffness in order to optimize ride performance. Thus balancing of two factors often leads to innovative and technically complex design solutions.
Weight
*Weight and Mass are often confused and used interchangeably.
Weight is technically a force and is measured in Newtons (N). Weight will change depending on the gravity. An object with a weight of 2N on Earth will have a weight of 0.7N on Mars.
Volume
Volume is the amount of 3-dimensional space a solid, gas, or liquid occupies.
Design Context:
Volume can be explored from many different perspectives: as a container of space. Some designs context may specify specific volume considerations that are related to performance needs. A interior volume of a technical backpack, for example, would be a key performance factor, and something that hikers may use to compare products. In addition, a market may have pre-established volumes that consumers expect products to follow - think drink containers or food packaging
Density
Density is the relationship between mass and unit of volume. It is measured in mass/volume such as 40kg/m2
Design Context:
From the perspective of design, density is an important property where mass and volume are important. This could include contexts such protective foams in bicycle helmets or foam mattresses.
The design of Aerotech bicycle shorts use foams of different densities in different parts to provide optimum comfort.
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Mattresses may use several layers of foam, each with a different density, to provide a long lasting comfort.
Electrical resistivity
Electrical resistivity is a materials ability to conduct or resist electricity.
Design Context:
This is an important material property when considering the design of an electrical component or safety equipment to be used around electricity. The Designer must know what the intended material will need to do: either insulate (have a high resistance, poorly conduct electricity); or conduct (low resistance, easily conduct electricity)
Fiberglass, because it is a poor conductor of electricity, is often used for ladders intended to be used for electrical work. Metal ladders are considered too dangerous to use in this context.
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Electrical cables feature different materials with different degrees of electrical resistivity. The bare copper wire has a low resistance, allowing electricity to flow easily. The wire insulation has very high resistance to insulate the wires from each other and prevent electrical shorts. The cable jacket on the outside also has high resistance to provide additional protection.
Thermal conductivity
Thermal conductivity measures how fast heat moves through a material.
For objects that are to be heated, or used around heat, thermal conductivity is important for designers to consider.
Design Context:
Wood handled cooking utensils are poor conductors of heat, and so are comfortable to use while cooking--metal handled cooking utensils conduct heat quickly and can be a safety hazard.
Metal utensils are obviously more durable but they conduct heat readily. Notice how the above design combines both metal and low thermal conductivity of wood to achieve a more ergonomic and safer design.
Thermal expansion
Thermal expansion is the degree to which a material increases its dimensions when heated. Different materials may expand at different rates. For designers, thermal expansion is important to consider when joining two different metals together such as when designing cooking ware or any items that receive heat or flame.
Design Context:
Pyrex glassware is made from borosilicate or soda-lime glass which have low thermal expansion rates. These objects can be used in ovens and on open flames for cooking.
Hardness
Hardness is the resistance of a material to scratching or penetration.
Design Context:
Ceramic tiles are very tough surfaces that are resistant to scratching, and as such are used in high-traffic public spaces like subway stations.
Mechanical Properties of Materials
These are the properties of materials that are usually measured through some form of destructive testing.
Tensile strength
The ability of a material to resist pulling forces.
Design Context:
Tensile strength is an important performance consideration for designs that need to resist pulling.
Elevator cables, for instance, need to have a high tensile strength in order to function safely and reliably.
Cables in suspension bridges need to support the deck of the bridge.
Compressive strength
The ability of a material to resist pushing forces.
Design Context:
When selecting materials that will support heavy loads, the ability of the material to resist being squashed is an important performance consideration.
In construction, concrete foundations are used to support the structure of the building.
Glass has a very high compressive strength and is used in modern buildings.
Stiffness
The ability to resist deflection (bending) by a force. the object can maintain its shape when a force is applied to it.
Design Context:
For objects where the shape needs to be maintained under high forces, stiffness is an important performance consideration.
Airplane wings need to maintain their shape in order to efficiently provide lift and control.
Bicycle frames need to maintain their shape so the rider can transfer as much of their pedal energy to the. If the frame is too "soft" it will flex, absorbing some of the energy. However, frames need to be flexible for comfort and handling. For this reason, frame designers may alter the thickness or shape of tubes in different parts of the bike frame. Learn more here: Read: Cyclist's guide to stiffness in frames.
https://www.cervelo.com/en/Engineering-Field-Notes/Engineering-Fundamentals/Stiffness
Toughness
The ability to deform (change shape) but resist cracking and not fracture under impact. If a material breaks into numerous small pieces when impacted, it has a low degree of toughness.
Design Context:
Toughness is performance consideration that is important where abrasion or cutting will take place.
Car bumpers need to be able to absorb energy from an impact but not crack or break.
Ductility
The ability to be drawn or extruded into a wire-like form.
*Ductility is different than malleability (the ability to be formed into a new shape; Clay is an example of a malleable material)
Design Context:
Ductility is usually a consideration in the manufacture of a material;
Extruded aluminum has a high level of ductility, which allows it to be manufactured into the shapes below:
Elasticity
The ability to a material to bend and then return to its original shape.
Design Context:
Elasticity is a performance consideration if the design must flex or bend when a force is applied, but return to its original shape.
A pole-vaulting poles need to flex when a force is applied to it in order to propel the athlete over the bar.
Plasticity
The ability of a material to be formed into a new shape. When the material is bent or deformed beyond its yield it does not return to its original shape.
Design Context:
Plasticity is an important consideration in the manufacture objects, particularly plastics and metals.
Metal casting
Plastic blow molding
Young's Modulus and Stress and Strain
Designers and engineers use Young's Modulus to select materials appropriate for the design context. Essentially, Young's Modulus will indicate when a material will bend, then break.
Young's Modulus is a measure of the stiffness of an elastic material. It is the ratio of stress to strain of a material as force is applied along its length. Each material has its own unique modulus.
Stress and Strain are usually plotted on a graph, as below, and show the relationship between the amount of force applied (Stress) to how much the materials changes in length.
Specifically,
Stress is the tensile force applied to a given area.
Strain is the percentage of change in length when a force is applied to the initial length
Video showing a material being tested to calculated the stress and strain on a material
Understanding a Stress-Strain graph
Think of the graph of telling a journey. As more force is applied to material sample, it will undergo a series of changes. It will move through different zones, each affecting its performance characteristics, until it reaches a failure point (it breaks)
A to B: Region of Elasticity. If the material was stretched and then the force was released, it would return to its original shape.
B: Yield Point. This is the point at which the material will no longer return to its original shape. It has now entered the plastic region.
C: Ultimate Tensile Strength (UTS). This is the point at which the material can maintain a maximum load. After this point, the material is moving towards its breaking or failure point. Necking occurs between point C and D.
D: Failure Point. This is the point at which the material actually breaks.
Comparison of different stress-strain profiles
As a student of design, it is necessary to understand what the graph represents, and how it would influence the choice of materials. As a designer, the goal is to find the ideal material for the design context.
Material A represents a material that can withstand a great amount of force, but then fails suddenly. It is brittle, and would likely break into many small pieces. Glass or ceramics would be a good example. There is no elastic zone.
Material B represents a material that is strong, but not ductile. Steel wires are very strong, but break suddenly. There is a small elastic zone.
Material C represents a material that is ductile, and could be extruded to create wires or cables.
Material D represents a very plastic material. It has almost no elastic zone, and a very large plastic zone.
Reading a Material Selection Chart
Material selection charts compare two material properties. The materials are plotted on the chart and displayed in groups.
Using the resources University of Cambridge Materials Engineering Department, you can explore different properties and materials to use in your design.
Aesthetic Properties of Materials
Aesthetic properties are those that are related to beauty and pleasure derived from a material.
Designers need to consider the aesthetic properties of the material they choose, and how these are perceived by different users. Remember, reactions to certain aesthetic properties are personal and change from person to person.
Form and shape
The shape and form of the material can influence how users interact and engage with it. We have different reactions to organic and geometric shapes.
The material can also determine the form or shape of a product. For example, plywood sheets used in furniture often give furniture a geometric form; while plastic, because of its plasticity, can allow an object to have organic forms.
Sound
The sound a material makes when it is touched or manipulated can also be part of the user experience. The noisy sound of a bag of chips opening is part of the eating experience -- it heightens expectations (article).
Car designers engineer the sounds of the car doors to create unique signatures for a particular car model or brand (article).
Smell
Smell has very powerful connections with memory. The smell of a material is largely a concern for food, however product designers should consider it.
The leather in Cadillac cars has a distinctive scent called Nuance. This scent was engineered by the company to provide a "new car smell" and to improve the driving experience.
https://www.caranddriver.com/features/secrets-of-that-new-car-smell-experiments-in-scent-page-2
PVC (poly vinyl chloride) is used in the manufacture of many inexpensive plastic children's toys. The strong smell can not only be off-putting, but also be unhealthy. In addition to the health concerns, designers should be aware of the smell of materials, particularly non-natural ones like plastics.
Texture
Texture is how something feels or looks.
Design Context:
Soft smooth textures might be desirable for a seat.
Textured surfaces can also provide improved grip, such as on a handle.
Depending on the finish of the surface, wood can have a visual texture (wood grain pattern) and/or a physical texture that can be felt.
Appearance
This refers to the color or pattern of the material.
There is much research about the psychological and cultural meanings of different colors. Designers should consider how their target users will interpret these meanings.
Colormatters.com: A useful primer and resource on the use of color in marketing, psychology of color, and science of color perception.
Properties of Smart Materials
Smart materials are reactive materials. They change their properties when exposed to stimuli such as electrical charges, moisture, or temperature. Their use be designers can open up new and innovative possibilities for product designs.
Catarina Mota is cofounder of OpenMaterials.org, a resource devoted to providing open and public access to smart materials.
Piezoelectricity
The ability to release an electric charge when deformed. When an electric current is passed through a piezoelectric material its volume will increase or it will vibrate.
Design Context:
Piezoelectric materials are often used in sensors and to generate electricity.
Piezoelectric sensors are used to measure the force of impact in airbag sensors. When the force exceeds a pre-determined value, the sensor sends a signal to activate the airbag.
Piezoelectric sensors are used to generate electricity while walking and running. See the Instructable for DIY instructions
Shape memory
Shape memory alloys (SMAs)have a pseudo-elastic property that allows them body to return to its original shape after deforming. Their shape changing property can be stimulated by either a change in temperature or the application of an electrical current. When the load is released, the body returns to its original shape.
Design Context:
The frames of some eyeglasses use SMAs to create a flexible frame
Medical devices such as Nitinol stents use SMAs to repair damaged blood vessels. to allow a thin device to be inserted into a vein. As the device heats up because of the body heat, it changes shape and keeps the blood vessel open.
Source: Wikimedia
Photochromacity
The ability to change color when exposed to light.
Design Context:
The most common application is in glasses to change the color or tint of the glass when exposed to UV light.
Many brands of sports glasses offer photochromatic lenses that adjust their tint depending on the brightness of the surroundings. In bright light like a sunny day the lenses darken; in overcast or dark conditions the lenses are lighten and become more transparent. the benefit for the user is that glasses will automatically adjust to changing light conditions.
Magneto-rheostatic
Fluids that undergo a change in their viscosity (thickness) when a magnetic force is applied. The change can change from a thick fluid to a solid almost almost instantaneously.
Design Context:
Maneto-rheostatic fluids are often used to dampen or absorb shock.
Shock absorbers in cars
Body armor can be flexible to allow for movement, but harden when an object hits it.
Electro-rheostatic
Fluids that undergo a change in their viscosity when an electrical force is applied. The change can be almost instantaneous. The change can change from a thick fluid to a solid almost almost instantaneously.
Design Context:
Due to the ability to be manufactured at small scale, electro-heostatic materials can be used to create very small valves.
Thermoelectricity
Two different conductors, that when joined together generate electricity when heat is applied. The materials of the conductors determine the amount of electricity generated. The most common material is Bismuth telluride (Bi2Te3)
Design Context:
The two main application of thermo-electrical devices is in power generation and refrigeration.
Space probes may use thermoelectric materials to power radio transmitters.
Some electric and hybrid cars have thermoelectric generators mounted in parts of the car where heat is generated in order to recapture the heat energy to use to recharge the battery.
