Inspection & Testing (ET105) key terms

The state of a product or process meeting all specified requirements, such as drawings, codes, and contract documents. Nonconformance means one or more requirements were not satisfied and typically triggers a documented disposition.

A distinguishing feature of a product or process that can be described or measured, such as dimension, hardness, or surface finish. Inspection plans list the characteristics to be verified and the method for each.

The total permissible variation between the upper and lower limits allowed for a dimension or property. A part is acceptable when its measured value falls within these limits, not necessarily on the nominal value.

The design value stated on a drawing or specification from which permissible limits are established. It is a reference number, not a guarantee that the finished feature will measure exactly that value.

A theoretically exact dimension shown on a drawing, usually enclosed in a box, used to locate features of size or establish datum-related geometry. It carries no tolerance itself; tolerance comes from feature control frames or general notes.

A theoretically exact point, axis, or plane established from a physical feature that serves as the origin for dimensional measurements and geometric tolerances. Inspection setups are commonly aligned to primary, secondary, and tertiary datums.

A permissible deviation from ideal form, orientation, or location of a feature, stated in a feature control frame with a symbol, tolerance zone, and datum references. Examples include flatness, perpendicularity, and position.

A rectangular drawing symbol containing the geometric characteristic symbol, the tolerance value, and any datum references. It tells the inspector which geometric control applies and how the tolerance zone is oriented.

A document established by consensus that defines technical requirements, methods, or terminology for products and processes. Standards become mandatory only when incorporated by reference into a code, contract, or regulation.

A body of rules adopted by a jurisdiction or authority that governs design, construction, or operation, often by referencing published standards. Compliance with an adopted code is legally enforceable, unlike voluntary guidance.

A document that states detailed requirements a product, material, or service must satisfy, including acceptance criteria and test methods. Specifications are usually project- or purchaser-specific and may invoke industry standards by reference.

The organization or individual responsible for enforcing code requirements and approving materials, installations, and inspection results. Their interpretation of an ambiguous code provision is generally binding on the project.

The ability to follow the history, application, or location of an item through recorded identification, such as heat numbers, lot codes, or calibration records. Traceability links test results and certificates back to the specific material or instrument used.

A document, often issued by the mill, listing chemical composition and mechanical test results for a lot of material. It supports verification that the delivered material matches the specified grade and is traceable to the heat.

Examination of an item by eye, with or without magnification and lighting aids, to detect surface defects, workmanship issues, and dimensional discrepancies. It is usually the first inspection performed and requires adequate illumination and access.

The condition of a surface described by roughness, waviness, and lay, often specified as an arithmetic average roughness value. It affects fatigue life, sealing, and coating adhesion, and is checked with profilometers or comparison standards.

The minimum light level or viewing condition specified for a visual or penetrant examination so that indications are reliably detectable. Insufficient lighting can cause defects to be missed and invalidates the inspection.

A hand tool with shaped edges or scales used to check weld features such as leg length, throat, reinforcement, undercut, and misalignment. It provides quick field measurements but must be verified and used correctly for the weld profile.

A group of inspection methods that reveal surface or internal discontinuities without damaging the item, including visual, penetrant, magnetic particle, ultrasonic, and radiographic techniques. Method selection depends on material, geometry, and defect type sought.

A method in which a liquid penetrant is applied to a cleaned surface, dwells in surface-breaking openings, and is drawn out by a developer to form visible indications. It works on nonporous materials of any composition but detects only surface-connected flaws.

A method that magnetizes ferromagnetic material and applies iron particles that collect at surface and near-surface discontinuities where flux leaks. It requires ferromagnetic material and detects flaws oriented roughly perpendicular to the magnetic flux.

A volumetric method that sends high-frequency sound waves into material and analyzes reflected or transmitted signals to locate internal discontinuities or measure thickness. It requires couplant, skilled interpretation, and reference standards for sizing.

A volumetric method that passes ionizing radiation through an item onto film or a digital detector, producing an image whose density changes reveal internal discontinuities. It requires radiation safety controls and image quality indicators.

A device, such as a wire or hole type, placed on the part or source side during radiography to demonstrate that the technique achieves the required image sensitivity. Acceptable visibility of the indicator confirms adequate contrast and resolution.

A known, characterized specimen or block containing artificial or documented flaws used to set up equipment and compare signal responses. It establishes sensitivity and helps size indications consistently between operators and inspections.

A destructive test in which a specimen is pulled until it fractures to determine properties such as yield strength, ultimate strength, elongation, and reduction of area. Results depend on specimen geometry, strain rate, and test temperature.

The stress at which a material exhibits a specified permanent deformation, determined from the stress-strain curve by an offset method or observed yield point. It indicates the stress level at which service deformation becomes significant.

The permanent increase in gauge length of a tensile specimen after fracture, usually expressed as a percentage of the original gauge length. It is a measure of ductility and depends strongly on gauge length and specimen type.

A destructive test that measures the energy absorbed when a notched specimen is struck by a swinging hammer, commonly the Charpy method. Results are sensitive to temperature, notch geometry, and specimen orientation.

A sample of material, often taken from the same lot or attached to the part during processing, that is tested to represent the finished item. Coupons must be prepared and tested under the same specified conditions.

The comparison of an instrument's indication against a reference of known accuracy to establish its deviation, usually documented in a certificate. Calibration alone does not guarantee fitness for use; adjustment and verification follow as needed.

A record stating the instrument tested, the reference standards used, environmental conditions, results, and the next due date. It provides evidence that measurement traceability was maintained at the time of calibration.

A quantified estimate of the range within which the true value is expected to lie, derived from instrument error, environment, operator, and repeatability contributions. Decisions near tolerance limits should account for it to avoid false accept or reject.

A defined rule specifying how many units to inspect from a lot and the acceptance number of nonconforming units allowed. It balances inspection cost against the risk of accepting a defective lot.

A defined quantity of material or product produced under essentially uniform conditions and treated as a single group for sampling and inspection. Clear lot identification is essential for valid sampling and traceability.

The stated limits or conditions that determine whether an item passes or fails inspection, such as maximum allowable indication size or minimum strength. Criteria should be objective, agreed before testing, and applied consistently.

A document that records a failure to meet a requirement, including the description, location, and disposition such as rework, repair, use-as-is, or scrap. It drives corrective action and provides an audit trail.

A stage in a process where work must stop and inspection or approval must occur before proceeding. Hold points are agreed with the customer or authority and cannot be bypassed without documented authorization.

A document listing the characteristics to be inspected, the methods and equipment, the acceptance criteria, and the records to be kept. It ensures inspection is planned, repeatable, and consistent with contract requirements.

A situation where an inspector's personal, financial, or organizational interest could improperly influence inspection judgments. It must be disclosed and managed so that results remain objective and independent.

The planned activities and systems that provide confidence that requirements will be met, distinct from inspection, which verifies results. It includes procedures, audits, training, and calibration programs.