Report of NDT Winter School 2015

Sho TAKEDA, Shoichiro HARA,

Takanori MATSUMOTO,

WU XiaoYang, XIE Shuxiao

1. Introduction

Non-Destructive Testing(NDT) international winter school 2015 was held on February 22 to 28,

2015, in Saarland University, Saarbrücken, Germany. About 30 international students from Bulgaria,

China, France, Germany, India, Indonesia, Lebanon, Paraguay, Tunisia, and Japan participate in(Fig.

1). NDT winter school mainly driven by the four institutions: Saarland University (Germany),

INSA-Lyon (France), Nanjing University of Aeronautics and Astronautics (China), Tohoku

University (Japan), and it was sponsored partly by the JSPS core-to-core program, "International

research core on smart layered materials and structures for energy saving", The German Society for

Non-Destructive Testing (DGZfP), Verheyen Ingenieure, Vienna Consulting Engineers ZT GmbH,

Dillinger Hütte, and I-deal Technologies.

Main objective of NDT winter school is to provide the students with the chance to deepen

knowledge about NDT, and communicating among international colleagues.

Six academic lectures were given by professors of Saarland University, Tohoku University, or

Vienna consulting engineers. The participating students performed 4 group projects about quality

control, fatigue damage, structural health monitoring and inspection robotics. The students visited to

Dillinger Hütte, one of the most reputable international steel manufacturers.

Fig. 1 Group photo (teachers and students who participated in NDT winter school).

2. Schedule

NDT winter school 2015 was held on February 22 to 28, 2015, in Saarland University,

Saarbrücken, Germany. Fig. 2 shows the schedule of NDT winter school. There were six academic

lectures and four student projects. The students visited to Dillinger Hütte, the steel manufacturer in

Feb. 26. This schedule was so tight, but the participants went sightseeing tour in the last day.

Fig. 2 The schedule of NDT winter school 2015.

3. Academic lectures

Six academic lectures were given by professors of Saarland University, Tohoku University, or

Vienna consulting engineers. In addition, the presentation about introduction of NDT winter school

and 4 student projects were given by professors in the first day.

First academic lecture was about "Determination of steel properties based on electromagnetic".

This lecture was given by Prof. Dobmann, Saarland University(Fig. 3) and Prof. Uchimoto, Tohoku

University(Fig. 4). It contains various contests from objective of determination of material properties,

to the principles and the applications of 3MA(Micromagnetic, Multiparametric Microstructure and

stress Analysis) and ECT(Eddy Current Testing) (Fig. 5 and 6). The participants of this school were

not only experts in NDT, but also the researchers of another fields and the undergraduate students

who had not started their research yet. Therefore, this lecture was very fruitful for them.

Fig. 3 Prof. Dobmann Fig. 4 Prof. Uchimoto

Fig. 5 Principle of ECT Fig. 6 Robot-aided 3MA inspection

Second lecture was about "Materials properties in steel". This lecture was given by Dr. Schneider,

Saarland University(Fig. 7). The topics of the lecture were Ultrasonic Testing(UT). The

microstructures of steels are correlated with the ultrasonic velocity in steel, because the ultrasonic

velocity is changed by the precipitations or the crystal orientation of material. Therefore, the

mechanical properties of steel such as hardness can be investigated by UT. In addition, UT is easier

to use than other testing method such as X-ray, because equipment of UT is smaller than the others.

The handy type UT equipment was developed for stress analysis(Fig. 8).

Fig. 7 Dr. Schneider Fig. 8 Handy type UT equipment

Third lecture was about "Microstructure, fatigue and fracture in steels". This lecture was given by

Dr. Starke, Saarland University(Fig. 9). The topics of this lecture were elastic deformation, plastic

deformation, fatigue damage, and factors affecting the fracture resistance. A material becomes weak

by repeatedly applied load, and it is broken even if it applied the stress much less than the ultimate

tensile strength. Fatigue is this weakening phenomenon of a material. "Fatigue Damage" is a key

factor of performing a non-destructive inspection, because micromagnetic parameter is correlated

with mechanic parameter of material(Fig. 10).

Fig. 9 Dr. Starke Fig. 10 Analogy of two methods

Forth lecture was about “Condition analysis, life cycle prognosis and maintenance planning for

roadway and railway infrastructure assets”. This lecture was given by Dr.techn. Robert Veit-Egerer,

Vienna Consulting Engineers(Fig. 11). Life Cycle Engineering (LCE) contains Maintenance

Planning, Life Cycle Analysis (LCA) and Life Cycle Calculations (LCC), based on in-house

know-how for more than 10 years. The motivation is supporting decision process of strategic,

integrated asset management on a technically & empirically well founded basis. We found that this

lecture was very conducive because it is not only use for railway(Fig. 12) but also for nuclear power

plant.

Fifth lecture was originally planned as "Ultrasonics and Phased Array" by Prof. Guy, INSA Lyon.

However, this lecture vanished because Prof. Guy could not attend to the school. Therefore, Prof.

Boller, Saarland University(Fig. 13) gave the lecture on "Acoustics & Guided Waves". The elastic

waves are used for the applications of NDT such as the pipe inspection with guided waves or phased

array, and the propagation of the waves is analyzed in order to investigate the validity. Therefore, it

is founded that these techniques are useful and promising.

Final lecture was about "Basics and challenges with robotics based structural health monitoring".

In this lecture, Prof. Boller and Dr. Chen-Ming Kuo, Saarland University(Fig. 14) introduced us the

risk of the growing aged structure. In order to manage the fatigue damage, detection of the fatigue

crack of specific area is necessary. On the other hand, avoiding the safety problem in construction,

traffic problem and so on. It is necessary to use inspection robot to capture the picture of the fatigue

crack in civil engineering.

Fig. 11 Dr. techn. Robert Veit-Egerer Fig. 12 Railway infrastructure

Fig. 13 Prof. Boller Fig. 14 Dr. Chen-Ming Kuo and MAV

4. Student projects

The main objective of the student project is to find the solution of arising issue of ageing

infrastructure. The real steel bridge nearby Saarbrücken was targeted as a real infrastructure.

4.1 Project 1 : Determination of Elastic Properties and Stresses in Steel

4.1.1 Introduction

The determination of elastic properties and anisotropic behavior as well as stresses including

residual stresses followed by flaw detection using different techniques such as ultrasonic,

electromagnetic. The data will be generated that can be used for structural assessment.

4.1.2 Objective

Objective of this project is to characterise the structural material non-destructively with respect

elastic properties, stresses.

4.1.3 Results

(1) Understand how to use ultrasonic testing apparatus(Fig. 15) and MikroMach for

3MA-testing(Fig. 16).

(2) Calculate the velocities propagating an Al, Fe and Ta single crystal.

(3) Evaluate the relative differences of the max and min values of the longitudinal waves for each

material and for the shear waves of each material.

4.1.4 Future works

Today, various UT systems are used in the factories. The contact UT and 3MA system are used

in this project, but the studies for development non-contact UT system is required in the situation

that cannot use contact UT system such as inspection of high temperature equipment.

Fig. 15 Overview of ultrasonic testing

apparatus

Fig. 16 Overview of MikroMach for 3MA-testing

4.2 Project 2 : Determination of Fatigue Properties in Steel

4.2.1 Introduction

Determination of the fatigue properties of the materials is important for design and to predict the

residual life of the constructs or the machines. The fatigue of the steel is caused by the change of

microstructure of the steel due to the repeated load applied to the steel, and applying the repeated

load generates heat within the steel. Therefore, it seems that the fatigue properties of the steels can

be evaluated by NDT techniques such as electromagnetics and thermography.

4.2.2 Objective

Objectives of this project are to understand what fatigue is and to determine the fatigue properties

of the steels which have different compositions by fatigue test, and to investigate the correlation with

data determined by thermography(Fig. 17, Fig. 18).

4.2.3 Results

(1) Understand what fatigue is.

(2) The steels which have different compositions showed different fatigue properties.

(3) Confirm the correlation between the fatigue properties and changing of temperatures of the

steels.

4.2.4 Future works

This work is the first step of prediction the residual life and health monitoring of the steel

constructs. If you want to target a larger one such as an actual bridge, thermography system which

has finer resolution and load-applying system which can apply larger load are required. In addition,

it seems that more accurate fatigue properties of steels can be evaluated by changing the shapes of

the samples.

Fig. 17 Fatigue testing system Fig. 18 Specimen and thermography system

4.3 Project 3 : Robotics Inspection of an Ageing Steel Bridge

4.3.1 Introduction

Particularly in civil engineering, for purpose of discovering the damage of ageing infrastructure,

we use MAV(Fig. 20) to find the location of the damage and capture pictures of the damage instead

of manual climbing operation.

As times progress, a lot of ageing infrastructures have to been evaluated, even should be repaired.

In the case of elevated highway, aerial railway, high-rise building and bridge, damages always exist

on risky locations which an operator has to access to. What’s more, without huge equipments it will

be impossible for manual operation. On the other hand, using conventional methods will result in

traffic problem, like traffic jam and so on. Therefore, it’s an expensive and time-consuming task. For

fear of this situation, we want to apply a new technology on damage inspection. It will help us to

avoid facing up to previous embarrassing situation.

4.3.2 Objective

For concern of facing the safety problems, economic problems and traffic problems, this study is

proposed.

4.3.3 Results

(1) Image collection by MAV.

(2) Image correction by PC.

(3) Images results can be displayed in 3D models.

(4) Quantification of damage has been done successfully.

4.3.4 Future works

In the process of image selection, selecting useful image after correction is still a very

time-consuming job. In order to prevent selecting process from consuming much time, an

automotive benchmark is preferred.

Fig. 19 Picture of students Fig. 20 Overview of flying MAV

4.4 Project 4 : Simulation and Monitoring of Loads and Damage in Steel Structures

4.4.1 Introduction

The structural monitoring can find out whether the structures are damaged. When damaged,

ultrasonic testing is applied for detection of the damaged part. In complex geometries, the echo

signals are also complex, and it is difficult to interpret the signals. Therefore, it is necessary to

investigate what type of defect can be detected and to find out the minimum size of the crack by the

simulation.

4.4.2 Objective

The objective of this project is to understand the importance of the monitoring and the simulation

in steel structures. For the purpose, the deformation of the i-beam section when loaded is calculated,

and the behaviors of deformation between a structure with crack and without crack are compared(Fig.

21). In simulation of ultrasonic wave propagation, the propagation of the wave is simulated, and the

wave dispersion due to the crack size or shape is investigated(Fig. 22).

4.4.3 Results

The calculated deformation showed the different behavior due to the damage. Found the change

of wave dispersion pattern by the crack size or shape.

4.4.4 Future works

In order to know the minimum size of the crack and the type of detectable defects, it is necessary

to evaluate signals quantitatively affected by the crack size or shape. For the development of the new

method that allows to detect the defects which cannot be detected by the conventional method, the

dependence of probe location or number should be investigated.

Fig. 21. Calculated deformation of the i-beam

section.

Fig. 22. Simulation of the wave propagation in

ultrasonic testing.

5. Visit to Dillinger Hütte

The participants visited to Dillinger Hütte, one of the most reputable international steel

manufacturers(Fig. 23). Lecture on "Quality management, inspection processes and techniques

(destructive and non-destructive) and certification in a steel factory" was given by Dipl. -Ing.

Scherm, Dillinger Hütte, and lecture on "NDT on heavy plates - ultrasonics, magnetic powder,

mobile hardness testing, visual inspection" was given by Dipl. -Ing. Dussaulx and Dipl. -Ing.

Hofmann, Dillinger Hütte. After the lectures, we took a tour of the factory. That ultrasonic testing

equipment of the large steel plates left a deep impression. Using any machine is necessary to

efficiently inspect. For example, the arm-like machine upset in order to check the front and back,

machinery for lifting the iron plate, infrared device for adjusting the starting point. In other facilities,

there was such destructive testing equipment and high-cycle fatigue test equipment. To meet needs,

various tests had been carried out.

Fig. 23. Overview of factory Fig. 24. Group photo

6. Daily life

6.1 Climate

We prepared many protections against cold weather, because it was expected that coldness

of winter in Saarbrücken is more severe than in Sendai. But the weather of Saarbrücken was not

cold as Sendai, and the class room of Saarland University was much warmer than that of

Tohoku University. These comfortable indoor environments were realized by not only heating

equipment, but the double window and the triple window. A door to enter into the building was

heavy as compared to that of Japan.

Fig. 25 Sky at Saarbrücken

6.2 Meal

High-calorie diet is preferred for the maintenance of body temperature in Germany. So meat

is staple food, and potatoes always be served as a side dish. There is a preserved food

"sauerkraut", such as cabbage and carrots in vinegar. Germany is cold climate, so food is less

compared to south of France and Italy, especially in winter tend to lack of food, and preserved

food is developed.

Meat and Garman beer are best batteries. My favorite food is wiener. One of most delicious

wiener was Weisswurst, a kind of white wiener, which is merely in Japan. We enjoyed eating

wiener, but we got a little bit tired of monotonous taste in last days…

We drank beer every day. Germany is famous for beer. We enjoyed the taste of beer

contains a little sour, adding a lemon, black, and Pilsner as familiar in Japan. A student is very

like beer drank about 2L every day.

Fig. 26. Joy of dinner Fig. 27. Dinner with friends

6.3 Residence

During the first couple of days, we stayed at the guest house(Fig. 28). It takes 10 minutes to

walk from there to the university. The guest house was in the corner of the sports clubs for a lot

of future Olympic athletes. During the last days, we stayed in the youth hostel. The room we

stayed did not have an Internet connection.

Fig. 28 Guest house

6.4 Sightseeing

In the last day, the participants went sightseeing tour to Trier(Fig. 29). This spot was

strongly still much in evidence in the culture of the Roman empire era. German ancient ruin has

a different depth of atmosphere from Japanese.

Fig. 29 Group photo with a part of ancient stronghold

6.5 International Friends

The participating students have different cultures, so we were struggling to differences of

English accent which spoken by students.

Meanwhile, I hit it off with bachelor student from India, and he wants to learn his master

course in Japan. My English skill is not good, it would have been fun if I could have

communicated with the students more.

NDT school will inspire us for learning English and study.

7. Summary

Communicating among international colleagues and having deep knowledge about research is

important for the future researchers with international leadership. The participants extended their

knowledge and broadened their horizon by academic lectures and student projects in this one week.

Therefore, this winter school was very fruitful for the students who aspire to be a researcher of NDT.