Whew kali ini saya lagi mencoba belajar teori dari awal, berbekal sebuah buku soal material untuk anak sipil saya nyoba deh baca dan kerjain test nya.
Ini dia latihan dari charter dua yang soalnya sudah saya modifikasi biar gak make rumus fisika.
Chapter 2 Questions
What are density, apparent density and bulk density?
Ans:
Density is the dry mass per unit volume of a substance under absolute compact conditions.
Apparent density is the dry mass per unit volume of a substance under natural conditions
Bulk density refers to the per unit volume of a substance under the conditions that powdery or granular materials are packed.
What are solidity and voidage?
Ans :
Solidity refers to the degree how the volume of a material is packed with solid substances, which is the ratio of the solid volume to the total volume
Porosity (P) is the percentage of the pores volume to the total volume with the volume of a substance.
Both solidity and porosity reflect the compactness of materials. Porosity and characteristics of pores (including size, connectivity, distribution, etc.) affect the properties of materials greatly. Generally, for the same material, the lower the porosity is, the less the connected pores are. Thus the strength will be higher, the water absorption will be smaller, and the permeability and frost resistance will be better, but the thermal conductivity will be greater
What’s the difference between hydrophilic and hydrophobic materials?
Ans :
When materials are exposed to water droplets in the air, there will be two cases, When angle 0 is smaller than or equals to 90" (O<90°), the material is hydrophilic, such as wood, brick, concrete and stone. The atttactive force between materials molecules and water molecules is stronger than the cohesive force between water molecules, so the materials can be wetted by water. When angle 0 is bigger than 90" (R>9Oo), the material is hydrophobic, such as asphalt, wax, and plastic. The attractive force between material molecules and water molecules is weaker than the cohesive force between water molecules, so the material cannot be wetted by water.
What is used to express the water absorption of materials?And what are the factors influencing the water absorption?
Ans :
Specific Absorption of Quality Specific absorption of quality refers to the percentage of the absorbed water to the dry mass when the material absorbs water to saturation
The specific absorption of volume refers to the percentage of the absorbed water's volume to the material's natural volume when the material absorbs water to saturation.
The water absorption depends on not only hydrophilicity and hydrophobicity of the material but also the porosity and characteristics of the pores.
What are the definitions and indexes of hygroscopicity, water resistance, impermeability and frost resistance respectively?
Ans :
Hygroscopicity is the property of materials to absorb water in the air. It can be expressed by moisture content. Moisture content is the percentage of the water quality contained in a material to its dry mass.
Water resistance is the ability to maintain its original properties when the material is affected by water in a long-term.
Impermeability is the ability of a material to resist the pressure water or the infiltration of other liquids.
Frost resistance is the property that a material can withstand several freeze-thaw cycles without being destroyed and its strength does not decrease seriously when the material absorbs water to saturation.
What influences do porosity and the characteristics of pores play on density, apparent density, water resistance, impermeability, frost resistance, thermal conductivity, strength and othcr properties?
Porosity play in every properties of materials, the more porosity weaker the materials and higher water absorption and lower water resistance, impermeability, frost resistance and etc.
What is strength of a material?
Ans :
Strength is the greatest stress that a substance can bear under external forces (loads) without destruction. According to different forms of external forces, the strength includes tensile strength, compressive strength, bend strength, shear strength and others.
What is strength grade?
Ans :
The strength can be divided into a number of different grades in accordance with the ultimate strength of most building materials, known as strength grade. The grades of brittle materials are mainly divided based on their compressive strength, such ordinary clay brick, stone, cement and concrete; and those of plastic materials and ductile materials depcnd on their tensile strength, such as steel. It is significant to classify the strength grades for mastering functions and choosing proper materials.
What is elasticity? What is plasticity?
Ans :
The elasticity is the property of a substance to deform with external forces and return to its original shape when the stress is removed.
The plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to external forces. This non-reversible deformation is called plastic deformation.
What is brittleness? What is toughness? What kinds of brittle and tough materials are often used in projects?
Ans:
Brittleness describes the property of a material that fractures when subjected to stress but has a little tendency to deform before rupture.
Most of inorganic non-metallic materials are brittle materials.
Toughness Impacted or vibrated by stress, a material is able to absorb much energy and deform greatly without rupture, which is known as toughness, also called impact toughness. such as construction steel, wood and rubber. Tough materials should be used in the structures bearing impact and vibration, such as roads, bridges, cranes and beams.
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