JC Engineering key terms

The ratio of a material's or component's failure strength to the maximum stress it is expected to carry in service, expressing how much reserve capacity remains before failure occurs.

The stress at which a material begins to deform permanently, marking the boundary between elastic and plastic behaviour and commonly used as the basis for design limits.

A plot of applied stress against resulting strain for a material under load, revealing stiffness, yield point, ultimate strength, and ductility characteristics used in design decisions.

The slope of the linear elastic portion of a stress-strain curve, quantifying a material's stiffness as the ratio of stress to strain within the elastic range.

Progressive cracking and fracture of a component caused by repeated or fluctuating stress cycles below the material's static strength, often initiating at stress concentrations.

Localised elevation of stress near geometric discontinuities such as holes, notches, or sharp corners, quantified by a factor applied to nominal stress in design calculations.

A numerical method that divides a structure into small elements, solves governing equations for each, and assembles results to predict stress, strain, and deflection under defined loads.

The specified constraints, supports, loads, and environmental assumptions applied to a model or design, which define how a system behaves and strongly influence analysis results.

A design method in which computed service stresses are kept below a permissible stress obtained by dividing material strength by a safety factor.

A limit-states design approach that applies separate statistical factors to loads and to resistances, accounting for different levels of uncertainty in each.

The documented set of requirements, assumptions, loads, codes, and operating conditions against which an engineering design is developed and later verified.

The permissible variation in a dimension or property of a manufactured part, specifying the upper and lower limits within which the item is accepted.

The relationship between mating part sizes, determining whether an assembly has intentional looseness, interference, or a transition between the two.

Controlled heating and cooling of a material to alter its microstructure and thereby change properties such as hardness, strength, toughness, or machinability.

Measurement of a material's resistance to localised indentation or scratching, used as an indicator of strength, wear resistance, and heat treatment effectiveness.

The capacity of a material to be welded into a sound joint under specified procedures without unacceptable cracking, porosity, or loss of properties.

A documented set of qualified welding parameters, including materials, joint preparation, filler, current, and preheat, that must be followed to produce compliant welds.

Inspection methods such as ultrasonic, radiographic, magnetic particle, and dye penetrant testing that reveal internal or surface defects without damaging the component.

A statistical measure of whether a stable process can consistently produce output within specification limits, usually expressed as capability indices comparing spread to tolerance width.

Use of control charts and statistical methods to monitor a process over time, distinguish normal variation from special causes, and trigger corrective action.

A structured investigation technique, such as the five-whys or fishbone diagram, used to identify the underlying reason a defect or failure occurred rather than only its symptoms.

A formal process for eliminating the cause of a detected nonconformity and preventing recurrence or occurrence of similar problems elsewhere in the system.

The documented organisational structure, responsibilities, procedures, and resources established to direct and control quality activities and achieve stated quality objectives.

Two complementary checks confirming that a design or product meets its specified requirements and that it fulfils its intended use in the actual operating environment.

A scheduling technique that identifies the longest sequence of dependent activities, thereby determining the minimum project duration and where delay directly affects completion.

The amount of time an activity can be delayed without delaying the project completion date or a successor activity, also called slack.

A bar chart displaying scheduled activities against a calendar timeline, commonly used to communicate progress, sequence, and resource allocation to project stakeholders.

A project control technique comparing planned value, earned value, and actual cost to forecast cost and schedule performance through indices and variance analysis.

Uncontrolled expansion of project requirements without corresponding adjustment to time, cost, or resources, often eroding schedule and budget performance.

A formal procedure for proposing, reviewing, approving, and documenting modifications to a design, scope, or contract so that impacts are assessed before implementation.

A systematic process of identifying hazards, evaluating the likelihood and severity of harm, and determining controls needed to reduce risk to an acceptable level.

A ranked order of risk reduction measures, from elimination and substitution through engineering controls and administration to personal protective equipment as the last resort.

A formal written authorisation specifying the conditions, precautions, and supervision required before high-risk work such as hot work or confined space entry may proceed.

A controlled procedure for isolating and securing energy sources, applying locks and warning tags, so equipment cannot be energised or started during maintenance.

A written, approved instruction describing the steps and responsibilities for performing a routine task safely and consistently to an agreed standard.

Scheduled servicing and replacement of equipment based on time or usage intervals, intended to reduce unexpected failures and extend asset life.

Periodic or continuous measurement of parameters such as vibration, temperature, and oil analysis to detect developing faults and schedule maintenance before functional failure.

A maintenance strategy that selects tasks according to the failure modes and consequences of each asset, aiming to preserve required function at least total cost.

A structured team method that lists potential failure modes of a design or process, rates their severity, occurrence, and detectability, and prioritises corrective actions.

The average operating time between successive failures of a repairable asset, commonly used to compare reliability and plan maintenance resources.

The sum of a project's future cash flows discounted to present value at a chosen rate, minus the initial investment; a positive result indicates value creation.

The rate used to convert future cash amounts to present value, reflecting the time value of money and the risk or cost of capital for the investment.

The time required for cumulative cash inflows to recover the initial investment, a simple screening measure that ignores cash flows after the break-even point.

The total cost of an asset over its whole life, including acquisition, operation, maintenance, and disposal, used to compare alternatives on a whole-of-life basis.

A formal statement of the principles and expected conduct for engineers, typically covering public safety, competence, honesty, confidentiality, and avoidance of conflicts of interest.

A situation where personal, financial, or other interests could improperly influence professional judgement, requiring disclosure and appropriate management or withdrawal.

Reporting a genuine concern about illegal, unsafe, or unethical conduct to an appropriate internal or external authority, ideally after internal channels have been exhausted.

Failure to exercise the degree of care and skill reasonably expected of a competent professional in similar circumstances, resulting in loss or harm.

The level of diligence, skill, and judgement that a reasonable and competent practitioner would apply under comparable conditions, used to judge professional conduct.