These two Case Studies come from a National Center on Case Studies. I think that a case study approach is very useful in applying knowledge and this is what makes….
Failure of materials is an analysis in engineering world, to approach and determining about how and why a materials has failed, like iron bar, why it can crocked or porous. Some general causes of failure are structural leading, wear corrosion and latent defects.
Failure of materials must be known by an engineer, safety is the first word when engineer working building structure. They can not take random about materials that is used. They must know strength, flexibility, and endure of materials.
For adding, with developing and updating software or research that had be done by company, we’ll more easy to know the characteristic of materials that we use.
TYPICAL OF FAILURE OF MATERIALS
Metal fatigue is caused by repeated cycling of the load below its static yield strength. It is a progressive localized damage due to fluctuating stresses and strains on the material. Metal fatigue cracks initiate and propagate in regions where the strain is most severe. The process of fatigue consists of three stages – Initial crack initiation, Progressive crack growth across the part, and Final sudden fracture of the remaining cross section.
Corrosion is chemically induced damage to a material that results in deterioration of the material and its properties. It is most coming from environment. Corrosion is normal, it is can not be removed, but can be minimized with several strategy like proper choice of material, design, coatings, and occasionally by changing the environment. Various types of metallic and nonmetallic coatings are regularly used to protect metal parts from corrosion. If corrosion can be minimized, materials be able to use and more advantage.
Ductile and Brittle Metal Failures
Ductile metals experience observable plastic deformation prior to fracture. Brittle metals experience little or no plastic deformation prior to fracture. At times metals behave in a transitional manner – partially ductile/brittle. Ductile fracture is characterized by tearing of metal and significant plastic deformation. The ductile fracture may have a gray, fibrous appearance. Ductile fractures are associated with overload of the structure or large discontinuities.
High Temperature Failures
In physics theory, when a materials is being warm, they will expand than original size. We know about boilers, gas turbine engines, and ovens are some of the systems that have components that experience creep. An understanding of high temperature materials behavior is beneficial
Failures involving creep are usually easy to identify due to the deformation that occurs. Failures may appear ductile or brittle. While creep testing is done at constant temperature and constant load actual components may experience damage at various temperatures and loading conditions. in evaluating failures in these types of systems. High temperature progressive deformation of a material at constant stress is called creep. High temperature is a relative term that is dependent on the materials being evaluated.
Liquid Metal and Hydrogen embitterment Failures
Liquid metal embitterment is the decrease in ductility of a metal caused by contact with liquid metal. The decrease in ductility can result in catastrophic brittle failure of a normally ductile material. Very small amounts of liquid metal are sufficient to result in embitterment.
The liquid metal can not only reduce the ductility but significantly reduce tensile strength. Liquid metal embitterment is an insidious type of failure as it can occur at loads below yield stress. Thus, catastrophic failure can occur without significant deformation or obvious deterioration of the component.
Hydrogen embitterment failures are frequently unexpected and sometimes catastrophic. An externally applied load is not required as the tensile stresses may be due to residual stresses in the material. The threshold stresses to cause cracking are commonly below the yield stress of the material.
Very small amounts of hydrogen can cause hydrogen embitterment in high strength steels. Common causes of hydrogen embitterment are pickling, electroplating and welding, however hydrogen embitterment is not limited to these processes.
There are causes of materials failure, but not disease that not have medicine. Every materials that we use have a protection, protection come from our knowledge about characteristic of materials as chemical composition, using guide or calculation and appointment the materials for our structure.
Addition, many factory, metal – producing majority, also publish list of their product that have content about characteristic ( strength, elasticity, endure and treatment).
Omens, J. H., MacKenna, D. A., and McCulloch, A. D. Measurement of Strain and Analysis of Stress in Resting Rat Left Ventricular Myocardium. J. Biomech Press,1993.
TCR Engineering Services Technical Team. White Paper: Investigating Material and Component Failure. TCR Engineering Services Pvt. Ltd. India, 2004.
Haut Donahue, T. L., Gregersen, C., Hull, M. L., and Howell, S. M. Comparison of Viscoelastic, Structural, and Material Properties. ASME, 1994.