Browse Publications Technical Papers 2003-01-1732

NVH Experimental Analyses for an Engine Structure Model Assembled with Ordinary Tap Bolts and with Through Bolts 2003-01-1732

A series of NVH experiments were performed for a set of single cylinder engine models made of aluminum, consisting of a cylinder head, a cylinder block and a bed-plate. Each has the same outer size of 150mm × 150mm; the different heights are 100mm, 200mm and 80mm respectively. Those dimensions were determined following the dimensions for a diesel engine in lightweight commercial vehicle with the bore size of 100mm and the crankshaft main bearing diameter of 60mm.
We chose 112 of measuring points on the structure surfaces and performed a series of impact tests, for the following cases:
  • (a)
    When the cylinder head and the bed-plate were fastened to the cylinder block by two sets of four ISO M10 tap-bolts, each with the lengths 1 =117mm and 2 =97mm.
  • (b)
    When the cylinder head and the bed-plate were fastened to the cylinder block together by a set of four ISO M10 through-bolts of grip length 3 =380mm.
By measurement the accelerations of the structure surfaces, the transfer functions and the mode shapes were defined successfully. Furthermore, we found significant differences for the case (b) compared to the case (a),
  1. (1)
    In the frequency range below 7000 Hz, the number of predominant resonance peaks in the case (b) was smaller than in the case (a).
  2. (2)
    From the summation of the square values of “Mobility Transfer Functions”, the vibration energy for the total structure surface can be estimated; we found that the vibration energy in the case (b) was much less than that in the case (a).
We investigated carefully the changes in the mode shapes for the two cases. Thus we found some reasons for the above differences and the merit of the through-bolts fastening.


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