Application for Optimization of Laser Beam Welding by Ultrasonic Wave Superposition

The potential of ultrasonic wave superposition to improve the properties of laser beam welding was investigated using stationary and moving Piezoshaker-System at the Department of Cutting and Joining Manufacturing Processes (tff) at the University of Kassel. An example of this is the test on the high-strength steel alloy 22MnB5, which is presented here. Adaptation to other welding processes and materials is possible.

The influences of the various excitation parameters of the Piezoshaker on the ultrasonic wave superposition were investigated, e.g. the distribution of the AlSi-coating particles within the joining zone as well as the weld seam properties [1].

The isi-sys Piezoshaker-System was used for the moving wave superposition, as shown in Fig. 1 The system contains a 2‑channel Piezoamplifier of the HPDA‑0–180-2C series and two Piezoshakers of the PS-W-02 series. The Piezoshakers are firmly connected to the laser optics via a mount and are moved relative to the component surface at a defined distance from the laser beam. These are pressed onto the component surface with a defined force using pneumatic cylinders. Unevenness and differences in the thickness of the joining partners can be compensated.

Fig. 1 (left): The distribution of the AlSi-coating in comparison without (a) and © and with (b) and (e) influence of an ultrasonic wave superposition by isi-sys Piezoshaker during laser beam welding with false-color images of EDS-analysis (d) and (f) [1]

Fig. 2 (right): Superimposed SEM-images and sectioned inverse pole figure mappings (IPFM) of a weld seam without (a) and with ultrasonic superposition (b) measured with electron backscatter diffraction shown as inverse pole figure in Z‑direction [1]

[1] Published in: C. Wolf, S. Völkers, I. Kryukov, M. Graß, N. Sommer, S. Böhm, M. Wunder, N. Köhler und P. Mäckel, „Enhancement of Weldability at Laser Beam Welding of 22MnB5 by an Entrained Ultrasonic Wave Superposition,“ In: Materials 2022, Bd. 15, 4800.

Strain Gauge Comparison

In this example a Vic-3D measurement with 5MP CMOS Camera was performed. The acryl specimen is fixed in a tensile testing machine. A strain gauge is attached at the back in combination with a SCAD 500 strain gauge amplifier. The output of the SCAD 500 was connected to the DAQ of the DIC system. The strain results are recorded parallel with the Vic-3D measurement and plotted in a diagram. The camera type is equipped with Sony 5Mpx Pregius sensor, 75 fps.

Strain Gauge Comparison-1 Strain Gauge Comparison-1a

Image 1: Vic-3D measurement of the acryl specimen

Strain Gauge Comparison-2

Image 2: Comparison of strain gauge data (red curve) and DIC Strain data (black curve)

The Vic-3D data match nearly perfect with the strain gauge data. Even at low strains the difference is less than 25 micro strain.

Strain Measurement — 2D Fatigue Test

Results of a 2D fartigue test on a thick piece of notched steel. With the use of a 2,3MP camera and Vic-2D a high strain resolution of approximate 5–10 microstrain can be archieved.

The video shows the results of this fartigue test.

Exx-Vs-Time-at-extraction-point

The graph demonstrates the bending load over time.

NDT of Carbon-NOMEX (honeycomb core) composite: Dynamic loading on a large yacht hull

Marine NDE (Spain) used the technical advantages of our Shearography-System especially in combination with the dynamic excitation for non-destructive examination (NDE) of large areas such as complete yacht hulls (see image below). The hull with a lenghts of 30,5m was a carbon-firber-composite and part of high performance sailing yacht in build. Because of the full-field method (100% of the inspected area is examined), the testing of the entire hull required only 240 shots, in three workdays.

The yacht hull consists of a sandwich construction, where are in particular used honeycomb cores (NOMEX).

Marine NDT1 Marine NDT2

On the left — A shearogram of a detected bonding defect (in red oval). The yellow X marks the location of the core sample shown at the right. The destructive test confirms the shearogram’s indication that there is a significant never-bond between the honeycomb core material and the film adhesive in this area.

Dynamic loading on a wind turbine blade and resin bridges

Analysis of a wind turbine blade

The test panel was an original section of a wind turbine blade with a defect (a foam block with bridges). Previously the defect was located by infiltration of color through small drilled holes. The sample is examined non-destructively by the SE-Sensor.

Section RotorBlade-a Section RotorBlade2

left: Set-up

right: Time average result at frequency of 2569Hz showing the debonding area.

Section RotorBlade3 Section RotorBlade4 left: Live view of surface including shearing.

right: Time average measurement from the marked area in the live image.

De-bonding of resin bridges

A GFRP sandwich with foam blocks and resin bridges should be examined. The detection of the defect type und structure is very quick and reliable in this case, because the defects are visible, not only at their local natural frequencies, but also due to their forced deflection shapes over a wide frequency bandwidth.

Section2 RotorBlade

The excitation frequencies of the selected measurements are 1398 Hz (1), 3133 Hz (2), 2442 Hz (3) and 4906 Hz (4) — numbering in following images:

Section2 RotorBlade2

Vakuum loading on battery packs

Air inclusion or air pockets in modern Li-battery packs is a serious and dangerous problem. The isi-sys SE2 sensor is able to detect tiny and large defects such as air bubbles, air pockets, cracks and other within a second. The defects can be far below or near to the surface. An example of a battery pack (test sample from University of Munich, IWB) and the measurement result is shown below.

Test setup:

The test has been done by SE2 sensor in combination with a glass vacuum chamber for a simple manual test. This is an economic solution for spot NDT by manual service. For automated series test in production different setups are required.

Test pocedure:

The battery packs are tested by small pressure differences of some mbar, which can be applied in seconds or below in small chambers. The sensor is monitoring the surface of the battery pack while the pressure is changed, measuring the differential deformation of the surface. Due to the expansion of the air bubbles and air pockets, the air inclusions can be located such as shown in the following images.

The first image shows the live view of the battery pack from the sensor. The second shows the recontructed phase, which is corresponding to the local deformation gradient.

Generally the required pressure difference depends on the defect depth, defect size an the mechanical stiffness of the tested structure, but in general the load is small due to the high sensitivity of the sensor detecting differential deformations of the surface.

Operation mode analysis on a mobile phone during vibration alert

Nokia3

Reference coordinates and contour of the mobile phone.

This article describes the measurement and analysis of the operation deflection shapes and rigid body vibration motions of a mobile phone excited by its vibration alert. The mearurement is done, using a non contact, 3D, full-field, high speed stereo image correlation system in combination with the new Vic-3D FFT module analyzes the recorded deformation data in the frequency domain by phase-separation method.

Nokia

The measured deformations and displacements during the vibration alert are evaluated against the reference state for each stereo image pair. In this case the recording time covers about 5,5 seconds with 1000 FPS corresponding to about 5500 single measurements.

The following figure show the average vibration amplitude U.

Nokia2

Dynamic Compression of Metals

Studying the behavior of metals during a high-speed dynamic compression event has always been challenging due to the complex test set up and fast data capture rates required. Currently, very little literature is available regarding deformation behavior at strain rates of 10 to 500s^-1. Utilizing high-speed cameras, the Vic-3D HS system can be used to quantify the surface displacements and strains in three dimensions over the entire field with great precision. Digital Image Correlation (DIC) has gained widespread popularity over recent years in such high-speed applications due to its high accuracy, flexibility and ease of use.

In this example, a 6mm diameter cylindrical specimen was compressed at a strain rate of 50s^-1. The Vic-3D HS system was used to capture the surface displacements and strains on the specimen during the event. A random speckle pattern is applied to the specimen that allows the analysis software to easily track the deformation to sub-pixel accuracy. Although the high- speed cameras are capable of much higher capture rates, for this test they were set to an appropriate frame rate of 14,400fps to maximize spatial resolution while acquiring an adequate number of images during the event. The cameras were post-trigger at a resolution of 1024 x 400 pixels. After the event, the images are transferred to the computer’s hard drive, and then post-processed using Vic-3D analysis software.

Images courtesy of Amos Gilat & Jeremy Seidt at Ohio State University.

Contractions of a Muscle

Biomechanic researchers were studying the contractions of a rat Tibialis Anterior muscle. It was desirable to quickly and accurately quantify the overall movements, as well as localized variations.

Challenges

Because the experiments involved live tissues, conventional gauges were difficult to apply and tended to interfere with the motion under study. It was important to capture data quickly, and for as many points as possible. Marker tracking had been used, but provided only gross averages. It was also time-consuming and tedious for the researchers to process this type of information.

Solution

The Vic-3D system was used to rapidly capture contraction data over the entire muscle surface. Due to the system’s speed and simplicity, it was possible to make numerous measurements at precisely timed intervals. There was no interaction with the specimen, and no need to guess which areas would be of greatest interest.

The resulting measurements provided high spatial resolution and made it possible to identify numerous areas where “bunching” of the muscle tissue caused significant variations in muscle contraction. These areas had not been previously identified with conventional methods. Finally, all calculations were done automatically. This saved considerable time and avoided the possibility of human error in the data processing.

Deformation Measurement

Aerospace Application Example

aerospace_1_notitle-300x247 Airbus has built a reputation for innovative aircraft, recognized around the world for their safety and efficiency. All of these attributes are driven by a top-notch testing program, whose innovative practice are evidenced by their use of the Vic-3D measurement system.

One of the goals of the Airbus testing program is to characterize the structural damage caused by collisions between the aircraft and small projectiles such as birds and other ground based debris, and to ensure that the structural integrity of the aircraft is maintained.

This type of event can be reproduced by firing a variety of different types of projectile at a piece of aircraft structure at a high velocity. The results obtained can be used to compare with computer models of the structure under impact loads, leading to more highly optimized and safer designs.

aerospace_2_notitle-300x224 Dr. Richard Burguete, experimental mechanics specialist at Airbus UK since 1997, explains the benefits of this approach as follows: “The VIC-3D system allows us to be sure we have captured all of the relevant data, some of which might have otherwise been unobtainable.”

Applications