This article provides answers to the following questions, among others:
- What type of loads do exist?
- What is dimensioning?
- What is the primary purpose of destructive testing?
- In which cases is non-destructive testing preferable?
Category: Material testing
Tensile test
This article provides answers to the following questions, among others:
- What kind of tensile specimens are usually used?
- Why must the tensile specimens not be deformed too quickly?
- Which quantities are measured during the tensile test?
- Why does the yield strength play a central role in mechanical engineering?
- Which material property is described by the elastic modulus?
- What is the “yield strength effect”?
- What is “yield point elongation” and what is the role of “Cottrell atmosphere”?
- What are Lüder bands (stretcher strain marks)?
- How does the “Portevin-Le Chatelier effect” (dynamic strain aging) occur?
- Why does “uniform elongation” play an important role in forming technology?
- Why does the tension curve drop during necking?
- Why do shorter tensile specimens show higher elongation at break than longer ones?
- Which statement can be made on the basis of the area under the stress-strain curve?
- What is the difference between the strength values and the deformation values with regard to their influence on the design of components?
- What is an “offset yield strength” and for which materials is it used?
Compression test
This article provides answers to the following questions, among others:
- Why are no longish specimens used in the compression test?
- Why is the true compressive stress lower than the engineering stress?
- What is the difference between the “compressive yield strength” and the “compressive offset yield strength”?
- What causes the formation of pressure cones in the material?
- Why does a crack usually form at an angle of 45°?
Hardness test
This article provides answers to the following questions, among others:
- How is the hardness of materials defined?
- On which principles are all hardness testing methods based?
- Which indenter is used for Brinell hardness testing?
- What is the load factor and what is it used for?
- For which materials is Brinell testing particularly suitable?
- Which indenter is used for the Vickers hardness test?
- Under what conditions can Vickers hardness values only be compared with each other?
- For which materials is Vickers testing particularly suitable?
- Which indenters are used for Rockwell hardness testing and for which materials are they used?
- What is the purpose of applying the preload?
- What are the advantages and disadvantages of Rockwell testing?
Flexural test
This article provides answers to the following questions, among others:
- How does the flexural stress distribution in the cross-section of a specimen subjected to bend loading look like?
- Where does the maximum bending stress occur?
- What characterizes the “neutral axis”?
- What role does the “axial section modulus” play in a bending load?
- What is the “flexural yield strength”?
- Why does the “flexural yield strength” has a higher value than the “tensile yield strength”?
- For which materials is a “ultimate flexural strength” used instead of a “flexural yield strength”?
- Why does the flexural test usually offer better results than the tensile test for determining the strength of brittle materials?
- How can the modulus of elasticity (Youngs modulus) be determined?
- How do residual stresses occur in the material?
- Why does the neutral axis shift into the area of compression in grey cast iron?
Charpy impact test
This article provides answers to the following questions, among others:
- What are the objectives of the “Charpy impact test”?
- Why does “notch impact energy” represent a measure of the toughness of a test specimen?
- What external influences effect the notch impact energy?
- What are “upper shelf”, “lower shelf” and “transition temperature”?
- Which lattice structures show a pronounced upper shelf and lower shelf and which do not?
- What is a ductile fracture, sliding fracture, brittle fracture and cleavage fracture?
- How does the fracture speed influence the notch impact energy?
Fatigue test
This article provides answers to the following questions, among others:
- What are the objectives of the fatigue test and how is it carried out?
- Why should the test frequencies not be set too high in the fatigue test?
- What is a stress cycle?
- How is the stress ratio defined?
- What is the difference between alternating stress and pulsating stress?
- What information can be obtained from the Wöhler curve?
- What are the characteristics of “low cycle fatigue”, “high cycle fatigue” and “fatigue strength”?
- Why does an increase of the mean stress in the compression range lead to larger bearable stress amplitudes?
- What is the difference between “fatigue strength” and “fatigue limit”?
- What are the characteristics of “alternating fatigue limit” and “pulsating fatigue limit”?
- What are two typical characteristics of the fracture surface of a fatigue fracture?
- What is the difference between “beach marks” and “fatigue striations”?
- How can the fatigue strength of components be increased?
- How to create the Haigh diagram and the Smith diagram and how can they be read?
- How is the “rotating bending test” and the “reverse bend test” carried out?
Stress rupture test (creep rupture test)
This article provides answers to the following questions, among others:
- What is a hot yield strength?
- What is creep?
- What factors influence the intensity of creep?
- At what temperatures is a technically relevant creep to be expected?
- What is the difference between the “stress-rupture-test” and the “creep rupture test”?
- What process do creep curves represent?
- What statement do “creep limits” “and “creep strengths” provide?
- Why are coarse-grained materials better suited than fine-grained materials for high-temperature applications?
- What are the characteristics of primary, secondary and tertiary creep?
Stress-relaxation test
This article provides answers to the following questions, among others:
- How is the stress-relaxation test performed?
- For which applications is the stress-relaxation test of great importance?
- What is relaxation strength?
Cupping test
This article provides answers to the following questions, among others:
- What is the cupping test (according to Erichsen)?
- What is cold formability?
Ultrasonic testing (UT)
This article provides answers to the following questions, among others:
- What is the measurement principle behind ultrasonic testing?
- What is the coupling agent used for?
- How are ultrasound waves generated and received?
- What is the difference between longitudinal waves and transverse waves?
- What types of ultrasonic probes are used?
- What is the dead zone?
- Which probes are used for weld inspection?
- What are phased array probes and what special advantages do they offer?
- What is the minimum size of imperfections that can be detected by ultrasonic waves?
Dye penetrant inspection (DPI)
This article provides answers to the following questions, among others:
- How is dye penetrant inspection carried out and where is it used?
- What is the purpose of applying the developer?
- Which types of cracks can only be tested with the liquid penetrant inspection?
Magnetic particle inspection (MPI)
This article provides answers to the following questions, among others:
- What is the principle behind magnetic particle inspection?
- How should flaws be aligned with respect to the magnetic field direction so that they are optimally visible?
- Why are components tested both in the mode of magnetic field flow and in the mode of current flow?
Eddy current testing (ECT)
This article provides answers to the following questions, among others:
- How does eddy current testing work?
- Why are two induction coils often connected against to each other?