Study on Vertical Vibration Characteristics of the 2-DOF Strip Rolling Mill Model with a Single Weak Defect on the Work Roll Bearing Outer Raceway

Considering the influence caused by a early single pit defect on the outer raceway of the work roll bearing, a 2-DOF plate strip rolling mill vertical vibration model with a single point weak fault on the outer raceway was established. With the practical parameters of the roughing mill of the 1780 hot continuous rolling mill, the vertical vibration characteristics of the rolling mill work roll with different rotating speed and different single pit defect area on the bearing outer raceway are analyzed by numerical simulation. It is found that with the change of the rotation speed of the work roll, different nonlinear vibration behaviors occurred, such as superharmonic resonance, main resonance, combined resonance and sub-harmonic resonance. Especially the subharmonic resonance of the work roll is more harmful than the main resonance when the work roll speed is twice the rotation speed corresponding to the first and second natural frequency of the rolling mill. This work provides a theoretical basis for further clarifying the effect caused by a early defect of the work roll bearing on the mill vibration.

SERANGAN KOROSI SUMURAN (PITTING CORROSION) PADA PIPA ROLL BEARING DISTRIBUSI

Dalam instalasi explorasi minyak, peralatan yang digunakan untuk menyalurkan minyak mentah dari sumur minyak ke tangki - tangki penampungan melalui pipa distribusi. Dimana untuk membagi ke masing-masing tanki penampungan pada pipa distribusi unit penyaluran minyak yang dibuat dapatberputar dengan menggunakan roll bearing.Pada penelitian ini telah diamati kerusakan yang terjadi pada disuatu instalasi explorasi minyak yang mengakibatkan kebocoran. Hasil penelitian menunjukkan bahwa penyebab utama kerusakan pada roll bearing karena adanyaserangan korosi sumuran . Pada bagian dalam bearing pada kondisi beroperasi selalu bersentuhan langsung dengan cairan / minyak secara terus menerus yang mengandung air danelemen-elemen yang bersifat korosif. Dalam keadaan demikian maka clearence pada bearing akan membesar dan pada akhirnya akan timbul kebocoran. Pemeriksaan dan pengujian yang dilakukan terhadap roll bearing, meliputi :pemeriksaan fraktografi dan metalografi, uji kekerasan, analisa komposisi kimia, serta pemeriksaan dengan SEM dan EDAX. Data dari hasil pemeriksaan dan pengujian tersebut kemudian di analisa untuk mengetahui penyebab terjadinya kebocoran pada roll bearing tersebut.

Non-Destructive Analysis of Surfaces after Hard Milling Based on Barkhausen Noise Technique

This paper deals with the non-destructive evaluation of surface made of hardened roll bearing steel after hard milling via Barkhausen noise technique. The paper discusses magnetic anisotropy linked with the structure transformations with regard to variable flank wear of cutting tool. Effective value of Barkhausen noise (BN) and Peak Position derived from the raw BN signal as well as BN envelopes are compared with metallographic observations and theoretical background about magnetic domains reconfiguration when the near surface undergoes severe plastic deformation at elevated temperatures.