# Durability Topics

**Abrasion Hardness**- Resistance to abrasive wear.
**Bending Stress**- Stress on the cross-sectional area of a beam due to the bending moment of the beam under load.
**Breaking Stress**- Also known as the ultimate tensile strength. This is the maximum stress that can be applied to a material.
**Brittle Crack Propagation**- A very sudden propagation of a crack with the absorption of no energy except that stored elastically in the body.
**Brittle Fracture**- Separation of a solid with little or no macroscopic plastic deformation.
**Brittleness**- The tendency of a material to fracture without first undergoing significant plastic deformation.
**Climate Chamber**- A test facility that can recreate different climatic conditions, often extreme conditions that allow a component, assembly or complete system to be tested to ensure it will perform correctly.
**Compressive Stress**- Stress on the cross-sectional area of a body normal to the compression force acting on the body
**Crack**- A fracture type discontinuity characterized by a sharp tip and high ratio of length and width to opening displacement.
**Crack Growth Analysis**- Fatigue analysis technique that assumes the existence of a crack or flaw and looks at this propagation.
**Critical Resolved Shear Stress**- The shear stress, resolved within a slip plane and direction, which is required to initiate slip.
**Cycle Counting**- Cycle counting is used to summarize lengthy, irregular load-versus-time histories by providing the number of times cycles of various amplitudes occur.
**Cyclic Loading**- The repeated loading and unloading of a structure to determine the fatigue lifetime.
**Durability Books**- Lists all Durability Books in the Encyclopaedia
**Durability Calculations**- Lists all Durability Calculations in the Encyclopaedia
**Durability Conversions**- Lists all Durability Conversions in the Encyclopaedia
**Durability Source Code**- Lists all Durability Source Code in the Encyclopaedia
**Durability Weblinks**- Lists all Durability Weblinks in the Encyclopaedia
**Engine Tuning to Increase Durability**- The adjustment, modification or design of internal combustion engines to increase durability.
**Fatigue**- An important mode of failure of engineering components subjected to dynamic stresses.
**Fatigue Analysis**- The anlysis of a particular design to understand how durable it will be over it′s lifetime.
**Fatigue Chunks**- Thick three-dimensional particles exceeding 50 microns indicating severe wear.
**Fatigue Corrosion**- The process in which a metal fractures prematurely under conditions of simultaneous corrosion and repeated cyclic loading at lower stress levels or fewer cycles than would be required in the absence of the corrosive environment.
**Fatigue Failure**- Failure occurs after a period of time even in cases of low stress, the component appears to get tired.
**Fatigue Life**- Number of cycles of fluctuating stress and strain of a specified nature that a material will sustain before failure occurs.
**Fatigue Limit**- In fatigue testing, the number of cycles which may be withstood without failure at a particular level of stress.
**Fatigue Notch Factor**- Ratio of fatigue strength of a specimen with no stress concentration to fatigue strength of a specimen with a notch or other stress raisers.
**Fatigue Ratio**- Ratio of fatigue strength or fatigue limit to tensile strength.
**Fatigue Resistance**- The ability of a material to withstand repeated and varying loads.
**Fatigue Strength**- Magnitude of fluctuating stress required to cause failure in a fatigue test specimen after a specified number of cycles of loading.
**Fatigue Strength Reduction Factor**- An alternate term for fatigue notch factor.
**Fatigue Test**- A method for determining the behaviour of materials under fluctuating loads.
**Fibre Stress**- Stress through a point in a part in which stress distribution is not uniform.
**Flow Stress**- The shear stress required to cause plastic deformation of solid metals.
**Fracture Stress**- True stress generated in a material at fracture.
**Heat Cracking**- A pattern of small, irregular cracks, that result from local heating of an object.
**Hoop Stress**- Circumferential stress in a cylindrically shaped part as a result of internal or external pressure.
**Hot Crack**- A crack that forms due to internal stresses developed from shrinkage during solidification of a metal casting.
**Level Cross Counting**- One count is recorded each time the positive sloped portion of the load exceeds a present level above the reference load, and each time the negative sloped portion of the load exceeds a present level below the reference load.
**Local Stress Relieving**- Stress relieving heat treatment of a specific portion of a structure.
**Mean Stress**- Algebraic difference between maximum and minimum stress in one cycle of fluctuating loading, as in a fatigue test.
**Nominal Stress**- Stress calculated on the basis of the net cross section of a specimen without taking into account the effect of geometric discontinuities such as holes, grooves, fillets, etc.
**Normal Stress**- Stress acting perpendicular to an imaginary plane cutting through an object.
**Operating Stress**- Stress imposed on a part in service.
**Overstressing**- Application of high fluctuating loads at the beginning of a fatigue test and lower loads toward the end.
**Peak Counting**- This method identifies the occurrence of a relative maximum or minimum load value.
**Peierls Stress**- The stress required to move a dislocation.
**Proof Stress**- Stress that will cause a specified permanent deformation.
**Rainflow Analysis**- A method of representing a random signal by various numbers of sinusoids that would produce the same amount of fatigue damage.
**Residual Stress**- Internal stress in a material often resulting from thermal or mechanical straining.
**Shear Stress**- Stress in the cross-sectional plane of a material that is in the same plane as the shearing force acting on it.
**Simple-Range Counting**- Range is the difference between two successive reversals. The range is positive when a valley is followed by a peak. The range is negative when a peak is followed by a valley.
**SN Curve**- High-cycle fatigue situations, materials performance is commonly characterized by an S-N curve, also known as a Wöhler curve . This is a graph of the magnitude of a cyclic stress (S) against the logarithmic scale of cycles to failure (N).
**Static Failure**- Failure when stress exceeds tensile strength in a single pass.
**Step Stressing**- stresses in a series of pre-selected increments.
**Strain-Life Analysis**- Models plasticity and low cycle fatigue.
**Stress**- Defined as the force per unit area of cross-section.
**Stress Amplitude**- One-half the range of fluctuating stress developed in a specimen in a fatigue test.
**Stress Concentration**- A condition in which a stress distribution has high localized stresses; usually induced by an abrupt change in the shape of the part (eg holes, corners, necks).
**Stress Corrosion**- Preferential attack of areas under stress in a corrosive environment, where such an environment alone would not have caused corrosion.
**Stress Corrosion Cracking**- Material deterioration due to cracking, by being under static stress either applied or residual.
**Stress Intensity Factor**- A scale factor to define the magnitude of the crack-tip stress field.
**Stress Raisers**- Changes in contour or discontinuities in a structure that cause local increases in stress.
**Stress Ratio**- Ratio of minimum stress to maximum stress in one cycle of loading in a fatigue test.
**Stress Relaxation**- Rate of reduction of stress in a material due to creep.
**Stress Relieving**- Heating to a suitable temperature, holding long enough to reduce residual stresses and then cooling slowly enough to minimize the development of new residual stresses.
**Stress Resultant**- A system of forces which is statically equivalent to a stress distribution over an area.
**Stress Rupture Strength**- Alternative name for Creep Rupture Strength.
**Stress-Life Analysis**- Analysis technique works best for high cycle fatigue.
**Stress-Rupture Test**- A tension test performed at constant temperature, the load being held at such a level as to cause rupture.
**Stress-Strain Diagram**- Graph of stress as a function of strain.
**Stress-Strain Ratio**- Stress divided by strain at any load or deflection, below the elastic limit of a material it is equal to tangent modulus of elasticity.
**Tensile Stress**- Stress acting on the cross-sectional area of a body normal to the tension force acting on the body.
**Thermal Fatigue**- A type of fatigue failure that introduces the cyclic stresses by fluctuating thermal stresses.
**Thermal Stress**- A residual stress introduced within a body resulting from a change in temperature.
**Torsional Stress**- Shear stress developed in a material subjected to a specified torque in torsion test.
**True Stress**- The load applied to a material divided by the cross sectional area over which it acts.
**Viscous Stresses**- The components of the stress tensor when the pressure, i.e., the mean of the three normal stresses, has been subtracted out from each of the normal stresses.
**Working Stress**- The allowable stress considered to be safe in the design of part. It is the ultimate stress of the material divided by a safety factor.

**Subjects: ** Materials Mechanical Engineering Noise & Vibration