Ultrasonic metal welding Citation for published version (APA): Harthoorn, J. L. (1978). Ultrasonic metal welding. Technische Hogeschool Eindhoven. https://doi.org/10.6100/IR161561 DOI: 10.6100/IR161561 Document status and date: Published: 01/01/1978 Document Version: Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, please follow below link for the End User Agreement: www.tue.nl/taverne Take down policy If you believe that this document breaches copyright please contact us at: [email protected] providing details and we will investigate your claim. Download date: 29. Sep. 2021 ULTRASONIC METAL WELDING PROEFSCHRIFT TER VERKRIJGING VAN DE GRAAD VAN DOCTOR IN DE TECHNISCHE WETENSCHAPPEN AAN DE TECHNISCHE HOGESCHOOL EINDHOVEN OP GEZAG VAN DE RECTOR MAGNIFICUS, PROF. DR. P. VANDER LEEDEN, VOOR EEN COMMISSIE AANGEWEZEN DOOR HET COLLEGE VAN DEKANEN IN HET OPENBAAR TE VERDEDIGEN OP VRIJDAG 14 APRIL 1978 TE 16.00 UUR DOOR JOHANNES LEENDERT HARTHOORN GEBOREN TE 'S-HEERENHOEK DIT PROEFSCHRIFT IS GOEDGEKEURD DOOR DE PROMOTOREN PROF. DR. P.C. VEENSTRA EN PROF. IR. B.L. TEN HORN CONTENTS Contents List of symbols 1. INTRODUCTION 1 1.1. Ultrasonic metal welding ................................. 1 1.2. Historical background ................................... 3 1.3. Aim and contents ofthe present study ........................ 4 2. A REVIEW OF LITERATURE ON THE PHENOMENA ASSOCIATED WITH ULTRASONIC WELDS AND MECHANISMS OF WELD FOR· MATION . 7 2.1. Mechanical properties of ultrasonic welds . 7 2 .1.1. Tensile shear strength . 7 2.1.2. Cross-tension strength . 8 2 .1.3. Fatigue strength . 8 2.1.4. Leak tightness . 8 2 .1 .5. Reproducibility . 8 2.2. The influence of machine settings on tensile shear strength . 9 2.3. Metallographic studies . 10 2.3.1. Thermal effects .................................. 10 2.3.2. Plastic deformation and hardness measurements in the weld zone; cracks . 10 2.3.3. Contaminating surface layers . 11 2.4. Quantities measured during welding . 12 2.4.1. Temperature .................................... 12 2.4.2. Acoustic power and vibrational amplitude . 13 2.5. Weldingmechanism ..................................... 13 2.5 .1. Welding mechanism and possible welding operations . 13 2.5.2. Mechanism of ultrasonic welding ...................... 14 2.5 .3. Metallic adhesion . 15 2.5 .3 .1. The area of real contact . 15 2.5 .3 .2. Surface contaminants . 17 2.5 .3 .3. Formation of metal to metal bonds . 17 2.5 .3.4. Residual stresses . 19 2.5 .3 .5. Conclusions . 20 3. WELDING AND MEASURING EQUIPMENT .................... 21 3.1. Ultrasonic welding equipment . .. 21 3.1.1. The generator and power amplifier ..................... 21 3.1.2. The vibrating system . 21 3 .1.3. The anvil and the clamping mechanism . 22 3.2. Theoretical description of the vibrating system . 2: 3.2.1. The mechanical transformer . 2· 3.2.1.1. The cylindrical rod as a transformer ............. ·2· 3.2.1.2. The hi-cylindrical transformer ................. 2: 3.2.1.3. Series connection of a transformer and a waveguide . 2: 3.2.2. Mechanical losses in the transformer and waveguide . 2l 3.2.3. The complete vibrator . 2• 3.2.3.1. The ultrasonic transducer . 2• 3.2.3.2. The frequency adjustment system . 3 3.2 .3 .3. The real part of the load . 3: 3.2 .3 .4. The imaginary part of the load . 3. 3.2 .3 .5. The force and velocity at the load . 3: 3.3. Measuring equipment . 3· 3.3.1. The 'Fotonic sensor' ............................... 3· 3.3.2. The frequency deviation meter . 3· 3.4. Quality of a weld and the test method . 3· 3.5. Subsonic welding equipment . 3: 4. ULTRASONIC WELDING EXPERIMENTS AND RESULTS . 3' 4.1. The specimens . 3' 4.2. The development of a weld . 3' 4.2 .1. The breaking force in a tensile shear test as a function of welding time and vibrational amplitude ........... ; . 3: 4.2.1.1. The clamping force . 3: 4.2.1.2. Observations . 41 4.2.1.3. The breaking stress . 4: 4.2.1.4. Discussion . 4• 4.2 .2. The appearance of the welded interface . 4: 4.2.3. The microwelds .................................. 6: 4.2.3.1. Length of the microwelds as a function of vibrational amplitude and welding time . 6 4.2 .3 .2. Influence of surface conditions on weld formation . 7 4.3. The alternating force exerted on the workpieces . 7 4.3.1. Esperiments ...............·. .. 7 4.3.2. The area of real contact ............................ 7 4.4. The relative displacement between the welded surfaces . 7 4.4.1. Equipment and experiments . 8 4.4.2. Results and discussion . 8 4.4.3. Further experiments, results and conclusion . 8 5. SUBSONIC WELDING, EXPERIMENTS AND RESULTS .. 8 5.1. Parameters in subsonic welding .............................. 8 5 .2. Properties of subsonic welds . 9 5.3. The alternating tangential force during subsonic welding and the energy dissipation . 94 5 .4. Conclusions . 97 6. THE ULTRASONIC METAL WELDING PROCESS A MODEL, DIS- CUSSIONS AND CONCLUSIONS . 98 6.1. Outline of the model . 98 6.2. The model . 99 6.2.1. The area of real contact . 99 6.2.2. The microwelds .................................. 99 6.2.3. The number ofmicrowelds .......................... 101 6.2.4. The growth of the welded area ........................ 102 6.2.5. Determination of the fmal value of the tensile shear force Fb(oo) 103 6.2.6. Evaluation of the constant of the model K ................ 104 6.3. Verification of the model and discussion ....................... 105 6.3.1. The values of Fh(oo) and K .......................... 105 6.3.2. Agreement between the model and the experiments .......... 110 6.3.3. Discussion ..................................... 112 7. SUMMARY .......................................... 116 SAMENVATTING ...................................... 119 Appendices . ......... 122 Al. Acoustic softening and diffusion under the influence of ultrasound ...... 122 A2. Relation between adhesion and physical or chemical properties of metals .. 124 A3. Numerical data for calculation of the alternating force .............. 127 A4. Estimate of the inertial forces acting on the workpiece contacting the welding tip ........................................... 127 AS. Calculation of the energy dissipation in subsonic and ultrasonic welding ... 128 A6. Temperature in the welding zone .............. ,, ............. 129 A6.1. Temperature rise caused by a circular heat source in an infmite medium ....................................... 129 A6.2. Temperature flashes in ultrasonic aild subsonic welding ...· ..... 132 A6.3. Estimate of the temperature in the welding zone during ultrasonic welding ....................................... 133 REFERENCES ............................................ 137 LIST OF SYMBOLS a ratio ~/~s ......................................... (-) 2 a acceleration . (m s· ) 2 A area (cross section) . (m ) 2 An nominal area of contact . (m ) 2 Am area of a microweld . (m ) 2 Ar area of real contact . (m ) 2 A(t) welded area after welding timet . (m ) 2 A(oo) final value of the welded area . (m ) B weighted sum of characteristic impedance (see eq. 3.21) . (kg s -I) 1 c propagation velocity oflongitudinal waves . (m s· ) 1 1 c thermal capacity ............................... (J kg" °K" ) c capacitance of the transducer . (F) 2 c effective stress at 8 = 1 . (Nm " ) D diameter . (m) 3 E energy dissipation per unit volume per oscillation ............. (Jm- ) 2 E Young's modulus . (Nm" ) F force . (N) Fa alternating tangential force in subsonic welding . (N) Fa adhesion force . t'N) Fb(t) breaking force in the tensile-shear test, of a weld produced in t sec. (N) Fb(oo) final value of the breaking force . t'N) Fe clamping force . (N) Fl alternating force exerted on the load by the welding tip . (N) Fn force, normal to the plane of contact . (N) Fs force, tangential to the plane of contact . t'N) Fw alternating tangential force in the welded interface . (N) F(ft) error function . ( - ) 2 Hv Vickers hardness.