Brittle materials include glass, ceramic, graphite, and some alloys with extremely low plasticity, in which cracks can initiate without plastic deformation and can soon evolve into brittle breakage.

Brittleness describes the property of a material that fractures when subjected to stress but has a little tendency to deform before rupture. Brittle materials are characterized by little deformation, poor capacity to resist impact and vibration of load, high compressive strength, and low tensile strength.

Brittle fracture means fracture of material without plastic deformation or with very small plastic deformation before fracture. Rock, concrete, glass, and cast iron all have such property, so they are called brittle materials. Ductile fracture means fracture of material with large plastic deformation before fracture.

Brittle materials are extensively used in many civil and military applications involving high-strain-rate loadings such as: blasting or percussive drilling of rocks, ballistic impact against ceramic armour or transparent windshields, plastic explosives used to damage or destroy concrete structures, soft or hard impacts …

Toughness is related to the area under the stress–strain curve. In order to be tough, a material must be both strong and ductile. For example, brittle materials (like ceramics) that are strong but with limited ductility are not tough; conversely, very ductile materials with low strengths are also not tough.

Concrete may be referred to as a brittle material. This is because concrete’s behaviour under loading is completely different from that of ductile materials like steel. In modern fracture mechanics concrete is considered as a quasi-brittle material.

Brittle materials do not undergo significant plastic deformation. They thus fail by breaking of the bonds between atoms, which usually requires a tensile stress along the bond. Micromechanically, the breaking of the bonds is aided by presence of cracks which cause stress concentration.

To find yield strength, the predetermined amount of permanent strain is set along the strain axis of the graph, to the right of the origin (zero). It is indicated in Figure 5 as Point (D). A straight line is drawn through Point (D) at the same slope as the initial portion of the stress-strain curve.

steel

Forged steel is generally stronger and more reliable than castings and plate steel due to the fact that the grain flows of the steel are altered, conforming to the shape of the part. The advantages of forging include: The tight grain structure of forgings making it mechanically strong.

Water is an effective medium when the goal is to have the steel to reach maximum hardness. However, using water can lead to metal cracking or becoming distorted. If extreme hardness isn’t necessary, mineral oil, whale oil, or cottonseed oil may be used in the quenching process instead.

Annealing. Annealing is frequently used to soften metals including iron, steel, copper, brass and silver. Annealing alters the physical and chemical properties of the metal to increase ductility and reduce hardness. This facilitates shaping, stamping or forming processes, and allows the metal to be cut more easily.

It’s common that a metal expands when it is heated, whereas it shrinks when it is cooled.

Applying heat with a propane torch can expand a nut (or threaded opening) and loosen it. If you’ve tried everything and still can’t free a bolt or nut, try heat. Once you’ve established that it’s safe, aim the flame at the bolt head or nut, not the surrounding metal.

Heat up the bolt with your heat gun This can be done indirectly by using heat. Once the rust bond has broken, or at least weakened, you can begin loosening up the bolt.

When the bolt is heated, it expands. Since the shaft of the bolt is constrained, it can’t expand inside the hole. As the bolt cools, it contracts. This means that the bolt can shrink in all directions, making the bolt slightly smaller.