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Definition: Failure investigation refers to the systematic examination of a technical failure case to determine the primary and secondary causes of failure. It combines materials analysis, fractography, load analysis and document review. The aim is the traceable reconstruction of the failure mechanism.

Practical relevance: The analysis covers fracture surfaces (e.g. by means of SEM), microstructural conditions, material composition (EDX/OES), mechanical properties and operating conditions. Typical mechanisms are fatigue fracture, stress corrosion cracking, overload or material mix-up (PMI). A structured approach in accordance with recognised standards increases the reliability of evidence and reproducibility.

Decision-making perspectives:

• Technical decision-makers: Derivation of technical corrective measures and prevention strategies.
• Purchasing/project management: Assessment of supplier responsibility and quality deviations.
• Science: Analysis of crack initiation, crack growth and microstructural influencing factors.
• Insurance/law: Court-proof documentation of the cause of failure and allocation of liability.

Typical testing or verification methods: Fractography in the SEM, metallography, hardness testing, tensile test, chemical analysis (EDX, OES), NDT.

FAQ:

• What is the aim of a failure investigation?
• The clear and traceable determination of the technical cause of failure as a basis for prevention or liability assessment.

Definition: FIB (Focused Ion Beam) is a microscopic technique in which a focused ion beam – usually gallium ions – is used for targeted material removal or deposition. It serves for high-precision sample preparation and microstructure investigation in the sub-micrometre to nanometre range. FIB is frequently combined with a scanning electron microscope (FIB-SEM).

Practical relevance: FIB enables the creation of local cross-sections, TEM lamellae or 3D tomographies through serial removal. Applications are found in failure analysis, semiconductor technology, coating evaluation and materials research. Beam current, accelerating voltage and the minimisation of ion implantation or beam damage are decisive factors.

Decision-making perspectives:

• Technical decision-makers: Investigation of local defects, interfaces and microcracks with high spatial resolution.
• Purchasing/project management: Commissioning of specialised analyses for complex failure or development questions.
• Science: Preparation of TEM samples, 3D reconstructions and nanoscale microstructure analyses.
• Insurance/law: Microscopic preservation of evidence in materials-related disputes.

Typical testing or verification methods: FIB cross-section analysis, TEM lamella preparation, 3D FIB tomography, combination with EDX or EBSD.

FAQ:

• What is a FIB system used for?
• For high-precision sample preparation, local microstructure analysis and investigation of nanoscale defects.

Definition: Fitness for Service (FFS) is the systematic assessment of whether a damaged or defective component can continue to be operated safely. It is based on analytical methods for evaluating corrosion, cracks or wall thickness loss. API 579-1/ASME FFS-1 is particularly internationally recognised.

Practical relevance: The assessment takes into account the damage mechanism, remaining wall thickness, material characteristics, loading and safety factors. Typical types of damage are local corrosion, crack formation or deformation. FFS analyses avoid unnecessary shutdowns, provided that structural integrity has been demonstrated by calculation.

Decision-making perspectives:

• Technical decision-makers: Defining continued-operation, repair or replacement strategies.
• Purchasing/project management: Economic trade-off between repair and replacement investment.
• Science: Application of fracture mechanics models and remaining service life calculations.
• Insurance/law: Demonstrating safe continued use despite documented damage.

Typical testing or verification methods: Wall thickness measurement (UT), fracture mechanics assessment, RBI analysis, materials testing.

FAQ:

• When is a fitness-for-service assessment carried out?
• When damage has been identified and the safe continued use of a component is to be assessed by calculation.

Definition: The fitness-for-service assessment is the systematic evaluation of whether a component or system can be operated permanently in a functional and safe manner under defined operating conditions. It takes into account mechanical, thermal, chemical and tribological loads. The objective is to demonstrate compliance with technical and normative requirements.

Practical relevance: The assessment evaluates load-bearing capacity, deformation behaviour, leak-tightness, corrosion resistance and fatigue strength. It may be based on standards, technical specifications or codes such as the Eurocodes, API standards or the Pressure Equipment Directive 2014/68/EU. The assessment draws on test reports, simulations and operating data.

Decision-making perspectives:

• Technical decision-makers: Approval for continued operation or definition of repair measures.
• Purchasing/project management: Evaluation of performance requirements and contractual warranties.
• Science: Validation of service-life models and load assumptions.
• Insurance/law: Demonstration of intended use and risk minimisation.

Typical testing or verification methods: Mechanical materials testing, non-destructive testing (NDT), FEM simulation, corrosion testing, functional and endurance tests.

FAQ:

• When is a fitness-for-service assessment required?
• In the case of deviations, damage or changed operating conditions, in order to assess safe continued use.

Definition: Forensic analysis is the court-proof investigation of technical failure cases for the evidence-secured clarification of cause, sequence of events and responsibility. It combines scientific analytics with a documented chain of custody. The aim is a comprehensible, reproducible and legally robust assessment.

Practical relevance: The objects of analysis are fracture surfaces (fractography in the SEM), material compositions (EDX, OES), microstructural conditions (metallography) and operating data. The methodology differs from purely technical failure analysis through increased requirements for documentation, sample identification and neutrality. The results serve as a basis for expert opinions and legal disputes.

Decision-making perspectives:

• Technical decision-makers: Technical clarification of causes and derivation of preventive measures.
• Purchasing/project management: Assessment of warranty or recourse claims.
• Science: Validation of analytical methods and reproducibility of the findings.
• Insurance/law: Court-proof presentation of evidence, allocation of liability and documentation security.

Typical testing or verification methods: SEM fractography, metallography, hardness testing, chemical analysis, non-destructive testing (NDT), document analysis.

FAQ:

• What distinguishes forensic analysis from a normal failure analysis?
• It is subject to increased requirements for evidence preservation, documentation and legal traceability.

Definition: Form and position tolerances are geometric tolerances used to limit the permissible deviations from the ideal forms and positions of a workpiece. They are part of the Geometrical Product Specification (GPS) and are governed by DIN EN ISO 1101. They supplement dimensional tolerances with functionally relevant geometric requirements.

Practical relevance: Form tolerances concern, for example, flatness, roundness or cylindricity, while position tolerances cover, among others, parallelism, perpendicularity or position. The assessment is carried out by comparison with defined tolerance zones. Incorrect tolerancing can lead to assembly problems, increased wear or malfunctions. Drawing entries must contain clearly referenced datum elements.

Decision-making perspectives:

• Technical decision-makers: Function-oriented tolerance definition taking into account manufacturability and costs.
• Purchasing/project management: Clear specifications to avoid scope for interpretation by suppliers.
• Science: Analysis of tolerance chains, measurement uncertainties and manufacturing variations.
• Insurance/law: Clear basis for assessing complaints and dimensional deviations.

Typical testing or verification methods: Coordinate measuring machine (CMM), roundness measurement, optical 3D measuring systems, evaluation in accordance with the GPS standards.

FAQ:

• Why are form and position tolerances more important than dimensional tolerances alone?
• They ensure that components fit together functionally, even when dimensions lie within the dimensional tolerance.

Definition: Form inspection is the metrological determination of deviations of a real workpiece from the ideal geometric form. Form characteristics such as roundness, flatness, straightness or cylindricity are assessed. The basis is the geometrical product specifications (GPS) according to DIN EN ISO 1101.

Practical relevance: Form deviations affect the fit, function and service life of technical components. The assessment is carried out by comparing the measured actual contour with defined tolerance zones. Measuring instruments are coordinate measuring machines (CMM), roundness measuring instruments or optical measuring systems. Compliance with form and position tolerances is often contractually stipulated.

Decision-making perspectives:

• Technical decision-makers: Ensuring functional fits and minimising wear or vibration.
• Purchasing/project management: Definition of clear tolerance requirements in technical drawings.
• Science: Analysis of manufacturing deviations and measurement uncertainties.
• Insurance/law: Proof of dimensional or tolerance deviations in the event of complaints.

Typical testing or verification methods: Coordinate metrology (CMM), roundness testing, profile and contour measurement, tactile or optical measuring methods.

FAQ:

• Which standard governs form and position tolerances?
• DIN EN ISO 1101 defines geometric tolerances within the framework of the GPS system.

Definition: The fracture mechanics assessment is the engineering evaluation of the crack safety of a component, taking into account existing or assumed flaws. It is based on characteristic values such as fracture toughness (K_Ic), CTOD (Crack Tip Opening Displacement) or the J-integral. Testing and evaluation methods are regulated, among others, in DIN EN ISO 12135.

Practical relevance: The assessment combines material characteristic values, crack size and loading (stress intensity factor K) to determine the critical crack length. It is central to pressure equipment, pipelines and welded structures. Safety factors and standards such as API 579 (Fitness for Service) or BS 7910 serve as the basis for assessment.

Decision-making perspectives:

• Technical decision-makers: Defining permissible flaws and inspection intervals.
• Purchasing/project management: Specifying fracture mechanics characteristic values in material or project requirements.
• Science: Modelling of crack propagation, numerical simulation (FEM).
• Insurance/law: Demonstrating sufficient safety margins in damage or liability questions.

Typical testing or verification methods: CTOD test, K_Ic determination, J-integral testing, non-destructive crack testing (e.g. UT, MT).

FAQ:

• Why is fracture toughness more important than tensile strength?
• Fracture toughness describes the resistance to crack propagation and is decisive for the assessment of existing flaws.

Definition: Fracture mechanics testing comprises standardised materials testing methods for determining the resistance to crack initiation and crack propagation. The values determined include the fracture toughness K_Ic, the crack tip opening displacement (CTOD) or the J-integral. The procedure is governed, among others, by DIN EN ISO 12135.

Practical relevance: The tests are carried out on notched and pre-cracked specimens under defined loading conditions. Critical stress intensity factors and crack resistance curves (R-curves) are evaluated. Areas of application include pressure equipment, pipelines, welded structures and safety-relevant components. Temperature, specimen geometry and type of loading have a significant influence on the results.

Decision-making perspectives:

• Technical decision-makers: Selection of suitable materials for crack-critical applications and definition of permissible flaws.
• Purchasing/project management: Specification of fracture mechanics values in technical delivery conditions.
• Science: Investigation of crack propagation mechanisms and validation of numerical simulations.
• Insurance/law: Demonstration of sufficient safety margins in the event of damage or dispute.

Typical testing or verification methods: CT specimen testing, SENB specimens, K_Ic determination, CTOD test, J-integral evaluation.

FAQ:

• What does a fracture mechanics test measure?
• It determines a material’s resistance to crack growth under defined mechanical loading.