Engineering Materials and its Properties PDF

CE 405 - CONSTRUCTION MATERIALS AND TESTING LESSON I ENGINEERING BEHAVIOR OF MATERIALS ENGR. RANDEL LUIS I PANGAN INTENDED LEARNING OUTCOME I. Understanding Material Properties: Students will be able to describe the fundamental mechanical properties of construction materials, such as strengt...

CE 405 - CONSTRUCTION MATERIALS AND TESTING LESSON I ENGINEERING BEHAVIOR OF MATERIALS ENGR. RANDEL LUIS I PANGAN INTENDED LEARNING OUTCOME I. Understanding Material Properties: Students will be able to describe the fundamental mechanical properties of construction materials, such as strength, elasticity, ductility, and hardness. II\. Material Testing Methods: Students will demonstrate knowledge of various testing methods (e.g., tensile, compression, shear, and impact tests) and explain their significance in evaluating material behavior. III\. Stress-Strain Relationships: Students will be able to analyze and interpret stress-strain curves. Identifying key points such as the proportional limit. **Introduction** A basic function of civil and construction engineering is to provide and maintain the infrastructure needs of society. The infrastructure includes buildings, water treatment and distribution systems, waste water removal and processing, dams, and highway and airport bridges and pavements. Although some civil and construction engineers are involved in the planning process, most are concerned with the design, construction, and maintenance of facilities. The common denominator among these responsibilities is the need to understand the behavior and performance of materials. **MATERIAL ENGINEERING CONCEPTS** Materials engineers are responsible for the selection, specification, and quality control of materials to be used in a job. These materials must meet certain classes of criteria or materials properties (Ashby and Jones, 2011). In addition to this traditional list of criteria, civil engineers must be concerned with environmental quality. In 1997, the ASCE Code of Ethics was modified to include \"sustainable development\" as an ethics issue. Civil and construction engineers must be familiar with materials used in the construction of a wide range of structures. Materials most frequently used include steel, aggregate, concrete, masonry, asphalt, and wood. Materials used to a lesser extent include aluminum, glass, plastics, and fiber-reinforced composites. **I.I ECONOMIC FACTORS** The economics of the material selection process are affected by much more than just the cost of the material. Factors that should be considered in the selection of the material include: - AVAILABILITY AND COST OF RAW MATERIALS - MANUFACTURING COST - TRANSPORTATION COST - PLACING - MAINTENANCE **1.2 MECHANICAL PROPERTIES** The mechanical behavior of materials is the response of the material to external loads. All materials deform in response to loads; however, the specific response of a material depends on its properties, the magnitude and type of load, and the geometry of the element. Whether the material "fails" under the load conditions depends on the failure criterion. Catastrophic failure of a structural member, resulting in the collapse of the structure, is an obvious material failure. **1.2.1 LOADING CONDITIONS** The two basic types of loads are static and dynamic. Each type affects the material differently, and frequently the interactions between the load types are important. Civil engineers encounter both when designing a structure. Static loading implies a sustained loading of the structure over a period of time. Once applied, the static load may remain in place or be removed slowly. Loads that generate a shock or vibration in the structure are dynamic loads. Dynamic loads can be classified as periodic, random, or transient **1.2.2 STRESS-STRAIN RELATIONSHIP** Materials deform in response to loads or forces. In 1678, Robert Hooke published the first findings that documented a linear relationship between the amount of force applied to a member and its deformation. The amount of deformation is proportional to the properties of the material and its dimensions. The effect of the dimensions can be normalized. Dividing the force by the cross-sectional area of the specimen normalizes the effect of the loaded area. The force per unit area is defined as the stress in the specimen (i.e., s = force/area). Dividing the deformation by the original length is defined as strain? of the specimen (i.e., e = change in length/original length). 1.2.3 ELASTIC BEHAVIOR If a material exhibits true elastic behavior, it must have an instantaneous response (deformation) to load, and the material must return to its original shape when the load is removed. Many materials, including most metals, exhibit elastic behavior, at least at low stress levels. Elastic deformation does not change the arrangement of atoms within the material, but rather it stretches the bonds between atoms. When the load is removed, the atomic bonds return to their original position. 1.2.3 ELASTIC BEHAVIOR Young observed that different elastic materials have different proportional constants between stress and strain. For a homogeneous, isotropic, and linear elastic material, the proportional constant between normal stress and normal strain of an axially loaded member is the modulus of elasticity or Young\'s modulus, E, and is equal to 1.2.3 ELASTIC BEHAVIOR In the axial tension test, as the material is elongated, there is a reduction of the cross section in the lateral direction. In the axial compression test, the opposite is true. The ratio of the lateral strain, ?I, to the axial strain, ?a, is Poisson\'s ratio, 1.2.4 ELASTOPLASTIC BEHAVIOR For some materials, as the stress applied on the specimen is increased, the strain will proportionally increase up to a point; after this point, the strain will increase with little additional stress. In this case, the material exhibits linear elastic behavior followed by plastic response. 1.2.5 VISCOELASTIC BEHAVIOR This is an assumption for elastic and elastoplastic materials. However, no material has this property under all conditions. In some cases, materials exhibit both viscous and elastic responses, which are known as viscoelastic. Typical viscoelastic materials used in construction applications are asphalt and plastics. TIME-DEPENDENT RESPONSE - Viscoelastic materials have a delayed response to load application. For example, Figure 1.8(a) shows a sinusoidal axial load applied on a viscoelastic material, such as asphalt concrete, versus time. Figure 1.8(b) shows the resulting deformation versus time.  1.3 **NON-MECHANICAL PROPERTIES** Non-mechanical properties refer to characteristics of the material, other than load response, that affect selection, use, and performance. **1.3 DENSITY AND UNIT WEIGHT** Density is the mass per unit volume of material. Unit weight is the weight per unit volume of material. Specific gravity is the ratio of the mass of a substance relative to the mass of an equal volume of water at a specified temperature. **1.3.2 THERMAL EXPANSION** The coefficient of thermal expansion is very important in the design of structures. Generally, structures are composed of many materials that are bound together. If the coefficients of thermal expansion are different, the materials will strain at different rates. The material with the lesser expansion will restrict the straining of other materials. This constraining effect will cause stresses in the materials that can lead directly to fracture.  **1.3.3 SURFACE CHARACTERISTICS** Corrosion and Degradation - Nearly all materials deteriorate over their service lives. The mechanisms contributing to the deterioration of a material differ depending on the characteristics of the material and the environment. Abrasion and Wear Resistance - Since most structures in civil engineering are static, the abrasion or wear resistance is of less importance than in other fields of engineering. For example, mechanical engineers must be concerned with the wear of parts in the design of machinery.