Unit 2.1 Statics - Key terms
Cable
A strong rope, usually made of metal, designed to have great tensile strength and to be used in structures. Centroid The geometric center of an area. Compression Force A body subjected to a push. Concurrent Force Systems A force system where all of the forces are applied at a common point on the body or having their lines of action with a common intersection point. Cross-Sectional Area A surface or shape exposed by making a straight cut through something at right angles to the axis. Direction The direction of a vector is defined by the angle between a reference axis and the arrow’s line of direction. Fixed Support A support that prevents translation and rotation in a beam. Flange A broad ridge or pair of ridges projecting at a right angle from the edge of a structural shape in order to strengthen or stiffen it. Free Body Diagram A diagram used to isolate a body from its environment, showing all external forces acting upon it. Gusset A plate or bracket for strengthening an angle in framework. Joint The connection points of members of a truss. Magnitude The absolute value of a number. Member Slender straight pieces of a truss connected by joints. |
Method of Joints
A method of analysis of trusses which constructs free body diagrams of each joint and determines the forces acting in that joint by considering equilibrium of the joint pin. Moment The turning effect of a force about a point equal to the magnitude of the force times the perpendicular distance from the point to the line of action from the force. Moment of Inertia A mathematical property of a cross section that is concerned with a surface area and how that area is distributed about a centroidal axis. Newton’s First Law Every body or particle continues at a state of rest or uniform motion in a straight line, unless it is compelled to change that state by forces acting upon it. Newton’s Second Law The change of motion of the body is proportional to the net force imposed on the body and is in the direction of the net force. Newton’s Third Law If one body exerts a force on a second body, then the second body exerts a force on the first body which is equal in magnitude, opposite in direction, and collinear. Pinned Support A support that prevents translation in any direction. Planar Truss A truss that lies in a single plane often used to support roofs and bridges. Resultant Force The resultant of a system of force is the vector sum of all forces. |
Roller Support
A support that only prevents a beam from translating in one direction. Scalar A physical quantity that has magnitude only. Sense The sense of a vector is the direction of the vector relative to its path and indicated by the location of the arrow. Simple Truss A truss composed of triangles, which will retain its shape even when removed from supports. Static Equilibrium A condition where there are no net external forces acting upon a particle or rigid body and the body remains at rest or continues at a constant velocity. Statically Indeterminate A structure or body which is over-constrained such that there are more unknown supports than there are equations of static equilibrium. Structure Something made up of interdependent parts in a definite pattern of organization, such as trusses, frames, or machines. Tension Force A body subjected to a pull. Vector Quantity A quantity that has both a magnitude and direction. |
Unit 2.2 Material Properties
Additive Process
The process of creating an object by adding small pieces or layers together to make a final product. Ceramic Of or relating to the manufacture of any product (as earthenware, porcelain, or brick) made essentially from a nonmetallic mineral (as clay) by firing at a high temperature. Codes A systemized body of laws; a set of principles, as of ethics. Composite Solid material which is composed of two or more substances having different physical characteristics and in which each substance retains its identity while contributing desirable properties to the whole; especially, a structural material made of plastic within which a fibrous material (as silicon carbide) is embedded. Decision Matrix A tool for systematically ranking alternatives according to a set of criteria. Finishing Machining a surface to size with a fine feed produced in a lathe, milling machine, or grinder. Forming A process that changes the size and shape of a material by a combination of force and a shaped form. Liability Anything for which a person is legally bound or responsible. Manufacturing To make into a product suitable for use; to make from raw materials by hand or by machinery; to produce according to an organized plan and with division of labor. Material The elements, constituents, or substances of which something is composed or can be made; matter that has qualities which give it individuality and by which it may be categorized. Mechanical Properties Those properties of a material that reveal the elastic and inelastic reaction when force is applied, or that involve the relationship between stress and strain; for example, the modulus of elasticity, tensile strength, and fatigue limit. Metals Any of various opaque, fusible, ductile, and typically lustrous substances that are good conductors of electricity and heat. Physical Properties Properties other than mechanical properties that pertain to the physics of a material and can usually be measured without the application of force. |
Polymers
Any of numerous natural and synthetic compounds of usually high molecular weight consisting of up to millions of repeated linked units, each a relatively light and simple molecule. Product Life Cycle Stages a product goes through from concept and use to eventual withdrawal from the marketplace. Raw Material Crude or processed material that can be converted by manufacture, processing, or combination into a new and useful product; something with a potential for improvement, development, or elaboration. Recycling Returning to an original condition. The extraction and recovery of valuable materials from scrap or other discarded materials. Subtractive Processes that remove material to change the size, shape, or surface of a part. There are two groups of separating processes: machining and shearing. Synthetic Produced by the combining of parts or elements to form a whole, rather than of natural origin; not real, artificial. |
Unit 2.3.3 Material Testing
Axial Stress A force with its resultant passing through the centroid of a particular section and being perpendicular to the plane of the section.A force in a direction parallel to the long axis of the structure. Breaking Stress The stress required to fracture a material whether by compression, tension, or shear. Compression When a material is reduced in volume by the application of pressure; the reciprocal of the bulk modulus. Deformation Any alteration of shape or dimensions of a body caused by stresses, thermal expansion or contraction, chemical or metallurgical transformations, or shrinkage and expansions due to moisture change. Destructive Testing Test methods used to examine an object, material, or system causing permanent damage to its usefulness. Elastic Limit Maximum stress that a material will withstand without permanent deformation. Elongation The fractional increase in a material’s length due to stress in tension or thermal expansion. Factor of Safety The ratio of actual strength to required strength Failure Point Condition caused by collapse, break, or bending, so that a structure or structural element can no longer fulfill its purpose. Fatigue The loss of the load-bearing ability of a material under repeated load application, as opposed to a single load. Hooke’s Law The law stating that the stress of a solid is directly proportional to the strain applied to it. Modulus of Elasticity The ratio of the increment of some specified form of stress to the increment of some specified form of strain, such as Young's modulus, the bulk modulus, or the shear modulus. Also known as coefficient of elasticity, elasticity modulus, elastic modulus. Toughness Mechanical property of a material that indicates the ability of the material to handle overloading before it fractures. Ultimate Stress Sometimes referred to as tensile strength; determined by measuring the maximum load a material specimen can carry when in the shape of a rectangular bar or cylindrical can. Variance The average of the squared differences from the mean. |
Nondestructive Testing
Test methods used to examine an object, material, or system without impairing its future usefulness. Problem Solving The ability to get answers to questions through a conscious, organized process. The answers are usually, but not necessarily, quantitative. Proportional Limit Point at which the deformation is no longer directly proportional to the applied force. Hooke’s Law no longer applies. Quality Control Operational techniques necessary to satisfy all quality requirements; includes process monitoring and the elimination of root causes of unsatisfactory product or service quality performance. Reliability The probability that a component part, equipment, or system will satisfactorily perform its intended function under given circumstances, such as environmental conditions, limitations as to operating time, and frequency and thoroughness of maintenance for a specified period of time. Resilience A mechanical property of a material that shows how effective the material is absorbing mechanical energy without sustaining any permanent damage. Rupture Strength Nominal stress developed in a material at rupture. Not necessarily equal to ultimate strength. Since necking is not taken into account in determining rupture strength, seldom indicates true stress at rupture. Shear Stress A measure of how easily a material can be twisted. Standard Deviation A statistical measurement of variability. Statistics The collection and analysis of numerical data in large quantities. Strain Change in the length of an object in some direction per unit. Stress The force acting across a unit area in a solid material resisting the separation, compacting, or sliding that tends to be induced by external forces. Stress-Strain Curve Graphical representation of a material’s mechanical properties. Tension The condition of a string, wire, or rod that is stretched between two points. |