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Geodesic Dome Invented by Buckminster Fuller. Have the advantage that these can be placed directly on the ground as a complete structure and have few limitations of size.

Geometric Model Elemental shape or form for imitation or comparison.

Geometry The shape or form of a surface, solid or frame.

Girder A beam that supports other beams; a very large beam, especially one that is built up from smaller elements.

Gravitational Potential Energy Work an object at height can do in falling.

Gypsum Board An interior facing panel consisting of a gypsum core sandwiched between paper faces. Also called drywall, plasterboard.

Hardness Measure of a material's resistance to localized plastic deformation. Most hardness tests involve indentation, but hardness may be reported as resistance to scratching (file test), or rebound of a projectile bounced off the material (scleroscope hardness). Some common measures of indentation hardness are Brinell Hardness Number, Rockwell Hardness Number, ASTM Hardness Number, Diamond Pyramid Impact Test Hardness Number, Durometer Hardness, Knoop Hardness, and Pfund Hardness. A table relating various types of hardness values of metals is given in ASTM E-140. Hardness often is a good indication of tensile and wear properties of a material.

Hexagon A plane figure with six straight sides. A regular hexagon is one with all six sides and all six angles equal, the angles all being 120°. Congruent regular hexagons can be fitted together to cover completely a plane surface. Apart from squares and equilateral triangles, these are the only regular polygons with this property.

Hexagonally Close-packed The closest packing of equal spheres is cubically close-packed when the result of connecting the centers of the spheres surrounding the center sphere with straight lines is the framework of a orthobicupola.

Hierachical Hierarchical solids can arise in natural and in man made materials and contain structural elements which themselves have structure. The hierarchical order of a structure or a material may be defined as the number n of levels of scale with recognized structure. n= 0 corresponds to a material viewed as a continuum for the purpose of analysis of physical properties, e.g., n = 1 (first order) could represent a latticework of continuous ribs or the atomic lattice of a crystal.

Holistic Greater than the sum of its parts.

Homogenous/heterogeneous Homogeneous means that the composition of a material is uniform or constant from one point to another: such as a monolithic materials. Heterogeneous means that the composition can vary, as with composite materials.

Hooke's Law Stress is directly proportional to strain. Hooke's law assumes perfectly elastic behavior. It does not take into account plastic or dynamic loss properties.

Horizontal Force A force whose direction of action is horizontal or nearly horizontal; also see lateral force.

Hysteresis The phenomenon by which the value of a physical property lags behind changes in the effect causing it.

Ideal (perfect) Triangulation State in which an assemblage or set of correlated members is organized as interdependent regular triangles.

Immobile, Immobilize Incapable of moving; to fix so as to be or become immovable.

Impact energy Energy required to fracture a part subjected to shock loading as in an impact test. Alternate terms are impact value, impact strength, impact resistance, and energy absorption.

Impact resistance The resistance of plastic articles to fracture under stresses applied at high speeds.

Impact Resistance, Designing for The impact resistance exhibited by an actual part depends on the design of the part, the material used, and the conditions of fabrication.

Designing for impact is complex. The shape and stiffness of the striking body, the shape of the part, the inertia of both, and end-use conditions can all affect impact strength. The following section gives you general design guidelines for improving impact strength. These guidelines comprise a sound approach to the design challenge, but are not a substitute for production of and testing for prototype parts in the actual conditions of use.

Part Design for Impact Resistance

Because the part must be able to absorb the energy of impact, part design is probably the greatest single factor – other than proper material selection – in determining impact strength. Part design will improve the impact resistance when you take care to:

Provide walls that flex rather than rigidly resist impact loading.

• Use rounded corners so that they can give with the impact and provide a smoother transfer of energy.
• Avoid any abrupt changes in stiffness (due to changes in wall thickness or structural reinforcement), which tend to concentrate impact loading. This includes such features as ribs, holes, and machined areas.

Mold Design

Impact strength can also be improved by good mold design. In this:

• Position gates away from high impact areas.
• Place weld lines, whenever possible, away from high impact areas.
• Core-out thick sections to reduce packing stresses and improve flexibility.

Assembly

The method of assembly can also affect a part's impact strength. Rigid joints can cause abrupt transitions in energy flow, which can break the joint. Joints, like walls and corners, should be flexible.

Impact test A method for determining behavior of material subjected to shock loading in bending, tension, or torsion. The quantity usually measured is the energy absorbed in breaking the specimen in a single blow, as in the Charpy Impact Test, Izod Impact Test, and Tension Impact Test. Impact tests also are performed by subjecting specimens to multiple blows of increasing intensity, as in the drop ball impact test, and repeated blow impact test. Impact resilience and scleroscope hardness are determined in nondestructive impact tests.

Impact strength The ability of material to withstand shock loading, i.e., the energy absorbed in breaking a material, under shock loading, calculated over the cross section of the specimen. Alternate terms are impact energy, impact value, impact resistance and energy absorption. It is an indication of the toughness of the material.

InTrials program UniStates’ Industrial Trials Program (InTrials^SM program) is a joint undertaking with your company to re-engineer selected commercial parts and components with Reflexive Materials Technologies (RMT™ technologies). The intent is to improve the in-service performance and marketability of these products. The first step is to work together to identify and prioritize a list of your company’s current commercial products that we would expect to produce the greatest gains in product performance and profitability through re-engineering with RMT™ technologies. For more information on UniStates' InTrials^SM program, please download a copy of the Briefing Paper on UniStates' InTrials^SM Program (Adobe Acrobat required).

Inorganic Designating or pertaining to the chemistry of all elements and compounds not classified as organic.

Inscribed Drawn or delineated within another figure so that the inner figure lies entirely within the boundary of the outer, touching it at as many points as possible.

Intelligent Intelligent material systems refers to the integrated use of structures, actuators, sensors, and control systems that allow the materials to adaptive to change or respond to external conditions.

Interfuse Blend or fuse, one with another.

Iron In pure form, a metallic element. In common usage, ferrous alloys other than steels, including cast iron and wrought iron.

Isostatic Characterized by the state in which pressures from every side, or direction, are equal.

Isotropic Having uniform properties in all direction. Exhibiting properties with the same values when measured along axes in all directions, because the measured properties of an isotropic material are independent of the axis of testing.

Izod impact test A test designed to determine the resistance of a plastics material to a shock loading. It involves the notching of a specimen, which is then placed in the jaws of the machine and struck with a weighted pendulum. See also Impact Strength.

kernel An essential subset of analytical and programming modules built into UniStates’ RMT2322 software that includes RMT-centric (a) design databases, (b) analytical tools and elements, and (c) virtual testing methodologies.