The type of failure in structure material:
1 Deformation failure
Tensile fracture
The material which is under stress in tension will be elongated and eventually fail at ultimate tensile strength. In the fracture of structure materials, tensile fracture is the most common fracture. A typical tensile fracture is the failure of reinforcing steel in concrete, for the steel in concrete plays the role of bearing bending, the tensile fracture is often resulted from the tension by the bending.
Shear fracture
When the stress applied parallel to the stress plane and the material yield to stress, it will cause shear fracture. Shear fracture often happens in bolts, rivets, screws and hinge. The shear fracture is accounted for the bolt failure, themost critical and most frequent failure in the steel structure.
Torsion fracture
When exceeding torque is applied to the material and caused twisting, the torsion fracture happens. The torsion fracture is uncommon in structure material for there are fewer scenarios for torque to be applied. However, torsion fracture is likely to be found during disaster such as earthquake.
Compression fracture
Under axial stress, the structure will have three modes of buckling: flexural buckling (or strut buckling), torsional buckling, and torsional-flexural buckling. The compression fracture often happened in column, which column structure often bear axial compression fracture.
Fatigue:
Fatigue is the weakening of a material caused by repeatedly applied loads. It is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values that cause such damage may be much less than the strength of the material typically quoted as the ultimate tensile stress limit, or the yield stress limit.
Corrosion:
There are several kinds of corrosions:
Uniform Corrosion:
Uniform corrosion is a general corrosion which takes place at the surface between metal and environment. It’s the most commonly observed corrosion and occurs at most corrosion scenario. In most corrosion case, uniform corrosion occurs along with other forms of corrosion, and the effect of different corrosions will effect with each other
Galvanic Corrosion:
Galvanic corrosion occurs at two metals or alloys which have different corrosion potential. In galvanic corrosion, the metal or alloy pairs will form a cell which the noble metal will be protected and the active metal will be corroded. The order that metal whether will be corroded is listed as galvanic series
Crevice Corrosion:
Crevice corrosion can be described as hole-effect corrosion. As a small volume space is created in the metal or alloys, the water or other solution is filling the small space. As the corrosion takes place in that small space, the hydrogen is exhausted and more negative charged ion will enter the space. This process creates an enrichment region of ions in liquid of that small space. With a rise in concentration of ions, the speed of corrosion reaction increases significantly
Pitting Corrosion:
Pitting corrosion often happens on protected alloys. The corrosion attacks crack or damaged point on the protect surface. As the uneven corrosion going on, a series of pits will be formed on the surface of the alloys. The theory behind pitting corrosion is similar with crevice corrosion, thus the pitting corrosion will be digging into the surface of alloys. At the pitting surface, a wide spread pitting corrosion hole will be found.
Environmentally Induced Cracking:
Corrosion is able to cause brittle failure in ductile material, which is a combination effect of corrosion effect and applied stress. There are three types of environmentally induced cracking: stress corrosion cracking, corrosion fatigue, hydrogen-induced cracking. As the static or cyclic stress is applied to the surface, a small crack and high diffusivity zone is created for accelerating the corrosion rate and the corrosion will also affect the mechanical behavior of alloys
Intergranular Corrosion:
The certain elements depletion in intergranular region, such as passivating elements or protecting elements, will result in less corrosion resistance of intergranular region. In alloys the intergranular corrosion is usual problems for most alloys consist of passivating elements such as Chromium. During certain tailoring process such as heat treatment, the Cr could be depleted by diffusion
De-alloying and Dezincification:
In the alloy which contains active elements for corrosion protection, the de-alloying is able carried out by depletion of protect elements. More reactive element is likely to react with the corroding media, the protecting elements moves to the corrosion area of alloys by diffusion thus cause the depletion.
Erosion-Corrosion and Fretting:
High speed fluid washing combined with electrochemical reaction is able to damage the alloys than by any of the effect if alone. As the high speed fluid will remove the disintegrated part of material, the passive layer will be peeled off thus result in a new routine. An erosion-corrosion is the highest rate corrosion process, where both mechanical and electrochemical take place。
Stress-corrosion (corrosion)
Stress corrosion cracking (SCC) is the growth of crack formation in a corrosive environment. SCC is highly chemically specific in that certain alloys are likely to undergo SCC only when exposed to a small number of chemical environments. The chemical environment that causes SCC for a given alloy is often one which is only mildly corrosive to the metal otherwise. Hence, metal parts with severe SCC can appear bright and shiny, while being filled with microscopic cracks.
1 Deformation failure
- Elastic
failure
Failure of a body to recover its original size and shape after a stress is removed. The material under simple or complex loaded condition is elastic in many ways and does not meet a failure but undergoes a failure. - Plastic
failure
Failure of a body which cannot recover its original size and shape after a stress is removed. At yield strength, the material will deform under plastically and fail t the plastic region.
- Fatigue
Fatigue is the weakening of a material caused by repeatedly applied loads. It is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values that cause such damage may be much less than the strength of the material typically quoted as the ultimate tensile stress limit, or the yield stress limit. - Stress-corrosion(corrosion)
Stress corrosion cracking (SCC) is the growth of crack formation in a corrosive environment. SCC is highly chemically specific in that certain alloys are likely to undergo SCC only when exposed to a small number of chemical environments. The chemical environment that causes SCC for a given alloy is often one which is only mildly corrosive to the metal otherwise. Hence, metal parts with severe SCC can appear bright and shiny, while being filled with microscopic cracks. - Plastic
fracture:
- Low
stress brittle fracture
Low-stress brittle fractures illustrate very clearly that the case of such premature failures lies in the impossibility for the material to sustain overall strains, which can normally be absorbed by the ductility of the steel. The reason for low-stress brittle fracture is: a. high stress rate; b. low temperature; c. preexisting plastic strain; d. high strain rate.
Overload:
There are two kinds of fracture:
Ductile fracture: In ductile fracture, extensive plastic deformation (necking) takes place before fracture. The terms rupture or ductile rupture describes the ultimate failure of tough ductile materials loaded in tension. Rather than cracking, the material "pulls apart," generally leaving a rough surface. In this case there is slow propagation and absorption of large amount energy before fracture
Brittle fracture: Brittle fracture is fracture that involves little or no plastic, or permanent, deformation. Brittle fracture of normally ductile steels has occurred primarily in large, continuous, box-like structures such as box beams, pressure vessels, tanks, pipes, ships, bridges, and other restrained structures, frequently joined with welded construction.
Tensile fracture
The material which is under stress in tension will be elongated and eventually fail at ultimate tensile strength. In the fracture of structure materials, tensile fracture is the most common fracture. A typical tensile fracture is the failure of reinforcing steel in concrete, for the steel in concrete plays the role of bearing bending, the tensile fracture is often resulted from the tension by the bending.
Shear fracture
When the stress applied parallel to the stress plane and the material yield to stress, it will cause shear fracture. Shear fracture often happens in bolts, rivets, screws and hinge. The shear fracture is accounted for the bolt failure, themost critical and most frequent failure in the steel structure.
Torsion fracture
When exceeding torque is applied to the material and caused twisting, the torsion fracture happens. The torsion fracture is uncommon in structure material for there are fewer scenarios for torque to be applied. However, torsion fracture is likely to be found during disaster such as earthquake.
Compression fracture
Under axial stress, the structure will have three modes of buckling: flexural buckling (or strut buckling), torsional buckling, and torsional-flexural buckling. The compression fracture often happened in column, which column structure often bear axial compression fracture.
Fatigue:
Fatigue is the weakening of a material caused by repeatedly applied loads. It is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values that cause such damage may be much less than the strength of the material typically quoted as the ultimate tensile stress limit, or the yield stress limit.
Corrosion:
There are several kinds of corrosions:
Uniform Corrosion:
Uniform corrosion is a general corrosion which takes place at the surface between metal and environment. It’s the most commonly observed corrosion and occurs at most corrosion scenario. In most corrosion case, uniform corrosion occurs along with other forms of corrosion, and the effect of different corrosions will effect with each other
Galvanic Corrosion:
Galvanic corrosion occurs at two metals or alloys which have different corrosion potential. In galvanic corrosion, the metal or alloy pairs will form a cell which the noble metal will be protected and the active metal will be corroded. The order that metal whether will be corroded is listed as galvanic series
Crevice Corrosion:
Crevice corrosion can be described as hole-effect corrosion. As a small volume space is created in the metal or alloys, the water or other solution is filling the small space. As the corrosion takes place in that small space, the hydrogen is exhausted and more negative charged ion will enter the space. This process creates an enrichment region of ions in liquid of that small space. With a rise in concentration of ions, the speed of corrosion reaction increases significantly
Pitting Corrosion:
Pitting corrosion often happens on protected alloys. The corrosion attacks crack or damaged point on the protect surface. As the uneven corrosion going on, a series of pits will be formed on the surface of the alloys. The theory behind pitting corrosion is similar with crevice corrosion, thus the pitting corrosion will be digging into the surface of alloys. At the pitting surface, a wide spread pitting corrosion hole will be found.
Environmentally Induced Cracking:
Corrosion is able to cause brittle failure in ductile material, which is a combination effect of corrosion effect and applied stress. There are three types of environmentally induced cracking: stress corrosion cracking, corrosion fatigue, hydrogen-induced cracking. As the static or cyclic stress is applied to the surface, a small crack and high diffusivity zone is created for accelerating the corrosion rate and the corrosion will also affect the mechanical behavior of alloys
Intergranular Corrosion:
The certain elements depletion in intergranular region, such as passivating elements or protecting elements, will result in less corrosion resistance of intergranular region. In alloys the intergranular corrosion is usual problems for most alloys consist of passivating elements such as Chromium. During certain tailoring process such as heat treatment, the Cr could be depleted by diffusion
De-alloying and Dezincification:
In the alloy which contains active elements for corrosion protection, the de-alloying is able carried out by depletion of protect elements. More reactive element is likely to react with the corroding media, the protecting elements moves to the corrosion area of alloys by diffusion thus cause the depletion.
Erosion-Corrosion and Fretting:
High speed fluid washing combined with electrochemical reaction is able to damage the alloys than by any of the effect if alone. As the high speed fluid will remove the disintegrated part of material, the passive layer will be peeled off thus result in a new routine. An erosion-corrosion is the highest rate corrosion process, where both mechanical and electrochemical take place。
Stress-corrosion (corrosion)
Stress corrosion cracking (SCC) is the growth of crack formation in a corrosive environment. SCC is highly chemically specific in that certain alloys are likely to undergo SCC only when exposed to a small number of chemical environments. The chemical environment that causes SCC for a given alloy is often one which is only mildly corrosive to the metal otherwise. Hence, metal parts with severe SCC can appear bright and shiny, while being filled with microscopic cracks.