02 MJP questions

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DOMANDE MJP 2023-07-20 Consider the lap joint spot welding of thin metal sheets. Both in electric resistance spot welding and in ultrasonic spot welding a vertical clamping force F is required. Which of the following sentences is NOT correct? o If the force F is set too high, there can be projections of material and the joint can be weakened. o If the force F is set too low, the contact pressure at the interface can be too low and this might produce a weakened joint o The proper value of force F also depends on the thickness of both the top and bottom sheets o The proper value of force F does not depend on the duration of the spot welding process 2022-06-17 Consider the Ultrasonic Welding process of two thin pure copper sheet samples. Does the USW Process change the metallurgical microstructure of the base copper? o Yes, because a full thermal recrystallization takes place and the grains become thinner o No, because the process is "cold" and the grains are unaltered o No, because the diffusion bonding phenomenon takes place inside identical crystal o structure, which are unaltered o Yes, but only the interface microstructure is limitedly refined by a mechanical "mixing" 2022-09-09 The sonotrode in USM can have different tapers and shapes. Mark the WRONG sentence: o The magnification factor of a linear taper sonotrode is proportional to D/d o Changing its shape and length, the amplitude can be varied to a limited extent o The sonotrodes are made of metals that have low acoustic losses. Fatigue is not a strict problem in designing the component because the tool operates under very small oscillations (less than 1 mm). o The total tool length should be designed so that the tool tip is located at a loop OLD EXAMS – JUNE 2021 The energy required for an ultrasonic welding…