SEF619 Phase Test - Sample Questions for Practice - NDT PDF

MM Oct 2024 SEF619 Analysis of Materials and Structures Phase Test/Exam Sample Questions Topic: Non-Destructive Testing Q.1: Types & characteristics of materials Compare and contrast the mechanical properties...

MM Oct 2024 SEF619 Analysis of Materials and Structures Phase Test/Exam Sample Questions Topic: Non-Destructive Testing Q.1: Types & characteristics of materials Compare and contrast the mechanical properties of metals, ceramics, and polymers. Discuss how these characteristic properties can be analysed for quality or product acceptance purposes using non-destructive testing methods. Q.2: Purpose of non-destructive testing State the purpose and key objectives of non-destructive testing applied to materials. Q.3: Damage identification – materials In the train industry, there are a number of typical defects that need to be detected during standard inspection and maintenance cycles. State 3 of these defects and how they can be inspected. Q.4: NDT tools, methods & procedures State four of the most common NDT methods for inspection and material testing. Briefly explain principle and application for each. Q.5: Quality assurance Discuss the role of non-destructive testing (NDT) in the quality assurance process of critical engineering components. Provide examples of different NDT techniques and explain how they contribute to ensuring the reliability and safety of materials in various industries/applications. Q.6: Penetration depth 304 stainless steel has a resistivity of 𝜌 = 690 × 10−9 Ω𝑚 (= 2.5% IACS) and relative permeability of 𝜇𝑟 = 1.05. a) Calculate the depth of penetration of eddy currents, 𝛿, when operating at a frequency of 35 kHz. Use the below formulae: 1 1 𝐻 𝜎= 𝛿= with 𝜇0 = 4𝜋 × 10−7 𝜌 √𝜋𝜇0 𝜇𝑟 𝑓𝜎 𝑚 b) For the above sample material, calculate the maximum allowed frequency to achieve a minimum penetration depth of 4.0 mm. Q.7: Material properties Explain how ultrasonic testing (UT) can be used to detect internal defects in metals. Discuss the types of defects that can be identified and the significance of detecting these defects in engineering applications. End of sample questions.  MM Oct 2024 Q.1 Answer Metals, ceramics, and polymers each have distinct mechanical properties that influence their applications in engineering design. 1. Metals: Mechanical Properties: Metals are generally characterized by high strength, ductility, and toughness. They have good electrical and thermal conductivity and can undergo significant plastic deformation before failure. Applications: Due to their strength and ductility, metals are widely used in structural applications, such as in the construction of buildings, bridges, and vehicles. Their conductivity makes them ideal for electrical wiring and components. Non-destructive Testing: 1. Ultrasonic Testing (UT): Uses high-frequency sound waves to detect internal flaws or characterize materials. 2. Electrical Conductivity Testing (ECT): Measures the conductivity (or resistance) of the material to detect internal non-homogenous areas. 3. Radiographic Testing (RT): Employs X-rays or gamma rays to view the internal structure of a material. 4. Magnetic Particle Testing (MT): Detects surface and near-surface discontinuities in ferromagnetic materials by applying a magnetic field and using iron particles. 5. Eddy Current Testing (ET): Uses electromagnetic induction to detect surface and sub-surface flaws in conductive materials. 6. Liquid Penetrant Testing (PT): Involves applying a liquid dye to the surface and then wiping surplice off and/or using a developer to draw out flaws which can be detected visually or under UV light. 2. Ceramics: Mechanical Properties: Ceramics are known for their high hardness, brittleness, and excellent thermal and chemical stability. They have high compressive strength but low tensile strength and are prone to fracture under stress. Applications: Ceramics are used in applications where hardness and thermal resistance are crucial, such as in cutting tools, refractory materials, and biomedical implants. Their brittleness limits their use in applications requiring high impact resistance. Non-destructive Testing: a) Ultrasonic Testing (UT): Effective for detecting internal cracks and voids in ceramics. b) Radiographic Testing (RT): Useful for identifying internal defects and structural integrity. c) Acoustic Emission Testing (AET): Monitors the release of energy from a material under stress, which can indicate crack formation and growth. d) Thermography: Uses infrared imaging to detect surface and subsurface defects based on temperature variations. e) Visual Inspection: Through the use of microscopes to detect surface defects in structure or micro-cracks.  MM Oct 2024 3. Polymers: Mechanical Properties: Polymers exhibit a wide range of properties depending on their composition. Generally, they are lightweight, have low strength compared to metals and ceramics, and can be very flexible or rigid. They have good corrosion resistance and insulating properties. Applications: Polymers are used in a variety of applications, including packaging, insulation, and consumer goods. Their lightweight and flexibility make them suitable for products like plastic bottles, containers, and automotive parts. Non-destructive testing: a) Ultrasonic Testing (UT): Can be used to detect internal defects and measure thickness. b) Radiographic Testing (RT): Helps in identifying internal flaws and verifying the integrity of polymer components. c) Thermography: Detects defects by observing thermal patterns on the material's surface. d) Visual Inspection: Often used for surface defect detection, especially in transparent or translucent polymers. Conclusion: The mechanical properties of these materials dictate their suitability for different engineering applications. Metals are preferred for structural and conductive applications due to their strength and ductility. Ceramics are chosen for their hardness and thermal stability, making them ideal for high-temperature and wear-resistant applications. Polymers, with their versatility and lightweight nature, are used in a broad range of products where flexibility and corrosion resistance are important.  MM Oct 2024 Q.2 Answer The purpose of non-destructive testing (NDT) of materials is to evaluate the properties and integrity of a material, component, or system without causing any damage. The key objectives of NDT are: 1. Detecting Flaws: Identifying internal and surface defects such as cracks, voids, inclusions, and other discontinuities that could compromise the material's performance. 2. Ensuring Quality: Verifying that materials and components meet specified standards and quality requirements before they are put into service. 3. Preventing Failures: Detecting potential issues early to prevent catastrophic failures, ensuring safety and reliability in critical applications. 4. Extending Lifespan: Monitoring the condition of materials and components over time to predict their remaining service life and plan maintenance or replacements. 5. Cost Efficiency: Reducing costs associated with destructive testing, material wastage, and downtime by allowing for in-service inspections and minimizing the need for repairs. 6. Compliance: Ensuring compliance with industry standards, regulations, and customer specifications. NDT is widely used across various industries, including aerospace, automotive, construction, and manufacturing, to maintain high safety and quality standards while preserving the integrity of the materials being tested. Q.3 Answer Non-destructive testing (NDT) is crucial for identifying various maintenance issues in railway carriage train wheel sets. Some typical problems that can be detected include: 1. Surface Cracks: These can develop due to wear and tear from regular use. Techniques like magnetic particle testing (MT) and liquid penetrant testing (PT) are effective for detecting surface cracks as well as visual inspection (VI). 2. Subsurface Cracks: These are often caused by rolling contact fatigue and can be detected using ultrasonic testing (UT) and eddy current testing (ET) 3. Wheel Tread Damage: This includes wear, spalling, and flat spots, which can be identified through visual inspection and ultrasonic testing (UT) 4. Corrosion: Corrosion can weaken the wheel structure and is typically detected using visual inspection and radiographic testing (RT) 5. Internal Defects: These include voids or inclusions within the wheel material, detectable by UT and RT and electromagnetic acoustic testing (EMAT) Regular NDT helps ensure the safety and reliability of railway operations by identifying these issues early, allowing for timely maintenance and repairs.  MM Oct 2024 Q.4 Answer 1. Ultrasonic Testing (UT) Principle: Uses high-frequency sound waves to detect internal flaws or measure material thickness. Applications: Commonly used in metals, composites, and ceramics to find cracks, voids, and other internal defects. 2. Radiographic Testing (RT) Principle: Employs X-rays or gamma rays to view the internal structure of a material. Applications: Ideal for detecting internal defects in welds, castings, and complex assemblies. 3. Magnetic Particle Testing (MT/MPT) Principle: Utilizes magnetic fields and ferromagnetic particles to detect surface and near-surface discontinuities in ferromagnetic materials. Applications: Effective for finding cracks, seams, and other defects in steel and iron components. 4. Liquid Penetrant Testing (PT) Principle: Involves applying a liquid dye to the surface of a non-porous material, which seeps into surface-breaking defects. A developer is then used to draw out the dye, making defects visible. Applications: Suitable for detecting surface cracks and porosity in metals, ceramics, and plastics. 5. Eddy Current Testing (ET) Principle: Uses electromagnetic induction to detect surface and near-surface flaws in conductive materials. Applications: Commonly used for inspecting non-ferrous metals and detecting cracks, corrosion, and conductivity variations. 6. Visual Inspection (VI) Principle: The simplest form of NDT, involving a thorough visual examination of the material or component. Applications: Used to identify surface defects, corrosion, and misalignments in various materials. 7. Acoustic Emission Testing (AET) Principle: Monitors the release of energy from a material under stress, which can indicate crack formation and growth. Applications: Useful for detecting active defects in structures like pressure vessels, pipelines, and bridges. 8. Thermography Principle: Uses infrared imaging to detect temperature variations on the surface of a material, which can indicate underlying defects. Applications: Effective for identifying delaminations, voids, and other defects in composites and electrical systems. 9. Electromagnetic acoustic testing (EMAT) Principle: Uses electromagnetic induction to induce and detect acoustic waveforms in a magnetisable material, similar to ultrasound but does not require a direct acoustic impedance matching interface to the material. Applications: Commonly used in metals to find cracks, voids, and other internal defects.  MM Oct 2024 Q.5 Answer This question allows a wider range of responses and individual written answers that demonstrate the thinking of how some of the above methods can be applied for quality assurance purposes in engineering. A typical answer may be along the lines of: Non-destructive testing (NDT) plays a crucial role in the quality assurance process of critical engineering components by ensuring their reliability and safety without causing damage. NDT techniques are essential for detecting defects, verifying material properties, and maintaining high standards in various industries. NDT is integral to quality assurance because it allows for the inspection and evaluation of materials and components without compromising their integrity. This is particularly important for critical engineering components where failure could lead to catastrophic consequences. By identifying defects early, NDT helps prevent failures, extend the lifespan of components, and ensure compliance with industry standards. Examples: UT is widely used in the aerospace and automotive industries to inspect critical components like aircraft wings and car axles. It helps ensure that these components are free from internal defects that could lead to failure under stress. RT is essential in the inspection of welds and castings in the construction and manufacturing industries. It helps detect internal defects such as voids and inclusions, ensuring the structural integrity of buildings and machinery. MT/MPT is commonly used in the railway and automotive industries to inspect components like train wheels and engine parts. It helps identify surface cracks and other defects that could lead to mechanical failure. PT is used in the aerospace and manufacturing industries to inspect non-porous materials like metals and ceramics. It helps ensure that components are free from surface cracks and porosity, which could compromise their performance. ET is widely used in the aerospace industry to inspect aircraft fuselage and wing structures. It helps detect cracks and corrosion, ensuring the safety and reliability of aircraft. Q.6 Answer 304 stainless steel has a resistivity of 𝜌 = 690 × 10−9 Ω𝑚 (= 2.5% IACS) and relative permeability of 𝜇𝑟 = 1.05. a) Calculate the depth of penetration of eddy currents, 𝛿, when operating at a frequency of 35 kHz. Use the below formulae: 1 1 𝐻 𝜎= 𝛿= with 𝜇0 = 4𝜋 × 10−7 𝜌 √𝜋𝜇0 𝜇𝑟 𝑓𝜎 𝑚 1 1 𝛿= = 1 2 √𝜋 × 4𝜋 × 10−7 × 1.05 × 35000 × √𝜋 2 × 4.2 × 35000 × 10 690 × 10−9 690 1 1 𝛿= = = 0.00218 𝑚 = 2.18 𝑚𝑚 √210265.485 458.54 b) For the above sample material, calculate the maximum allowed frequency to achieve a minimum penetration depth of 4.0 mm. 1 1 1 𝑓= = = = 0.0104 × 106 = 10400 𝐻𝑧 𝜋𝜇0 𝜇𝑟 𝜎𝛿 2 4𝜋 2 10−7 1.05 1 −3 )2 96.12 × 10−6 (4 × 10 690 × 10−9  MM Oct 2024 Q7 Answer Ultrasonic Testing (UT) for Detecting Internal Defects in Metals Ultrasonic testing (UT) is a widely used non-destructive testing (NDT) method that employs high- frequency sound waves to detect internal defects in metals. This technique is crucial for ensuring the integrity and reliability of metal components in various engineering applications. Principle of Ultrasonic Testing: UT involves transmitting ultrasonic waves into a material and analyzing the reflected waves to identify any discontinuities. A transducer generates the ultrasonic waves, which travel through the material. When these waves encounter a defect, such as a crack or void, they are reflected back to the transducer. The time it takes for the waves to return and the amplitude of the reflected signal provide information about the location and size of the defect. Types of Defects Detected by UT: 1. Cracks: UT can detect both surface and subsurface cracks, which are critical defects that can lead to catastrophic failure if not identified and repaired. 2. Voids and Inclusions: These are internal defects that occur during the manufacturing process. Voids are empty spaces within the material, while inclusions are foreign materials trapped inside the metal. 3. Laminations: These are planar defects that occur parallel to the surface of the material, often resulting from rolling processes in metal production. 4. Corrosion: UT can detect areas of corrosion that have thinned the material, which is essential for maintaining the structural integrity of components exposed to harsh environments. Significance of Detecting Defects: Detecting internal defects in metals is crucial for several reasons: 1. Safety: Identifying and addressing defects helps prevent failures that could lead to accidents, injuries, or fatalities, especially in critical applications like aerospace, automotive, and construction. 2. Reliability: Ensuring that metal components are free from defects enhances their reliability and performance, reducing the likelihood of unexpected breakdowns. 3. Cost Savings: Early detection of defects allows for timely repairs or replacements, minimizing downtime and maintenance costs. 4. Compliance: Many industries have stringent standards and regulations that require regular NDT inspections to ensure the quality and safety of metal components.