Flaking of PEEK under one-point rolling contact fatigue using Al2O3 ball

The growth of flaking as tribological fatigue failure in PEEK was investigated through the one-point type rolling contact fatigue test between a machined PEEK polymer shaft and an alumina bearing's ball. Due to Hertzian contact of cyclic compressive stress, the subsurface fatigue cracks in the PEEK shaft propagated in rolling and axial directions. When the rolling fatigue life of the PEEK shaft reached 106 fatigue cycles, many narrow angled cracks occurred in the near-surface of the rolling track without flaking. On the other hand, when the flaking ocuurred on the PEEK shaft before 106 fatigue cycles, semicircular surface and subsurface crack propagations were observed. From these observations, it was found that micro-flaking occurred due to the linkages between subsurface and surface cracks. Flakingdeveloped due to the accumulation of these micro-flakings

PEEK樹脂の転がりならびに摺動下における強度に関する基礎的研究

序章 第I章 PEEKベアリング内輪とアルミナ玉の接触が内輪へ及ぼす影響 第II章 PEEKブッシュとチタン・アルミ合金の接触がロボット関節へ及ぼす影響 終章（結論）主1-参0工学府_機械工学Submitted by アルバイト QIR ([email protected]) on 2013-06-25T02:10:05Z No. of bitstreams: 2 eng2246.pdf: 12719158 bytes, checksum: b0b06f0e59f3111210579eaa9b6f5712 (MD5) eng2246_abstract.pdf: 158238 bytes, checksum: 3d0e365a052222faecbba1d7d4e9012b (MD5)Made available in DSpace on 2013-06-25T02:10:05Z (GMT). No. of bitstreams: 2 eng2246.pdf: 12719158 bytes, checksum: b0b06f0e59f3111210579eaa9b6f5712 (MD5) eng2246_abstract.pdf: 158238 bytes, checksum: 3d0e365a052222faecbba1d7d4e9012b (MD5) Previous issue date: 2013-03-26本研究では，機械加工によるポリエーテルエーテルケトン(PEEK)軸受・PEEKブッシュについて，摩耗や転がり疲労による損傷を調査した．特に，PEEK樹脂特有の摩耗や変形，摺動，き裂成長について，転がり疲労などの基礎的な実験・評価を通して軸受性能に与える影響を調べるとともに，ロボット関節に使用する際に必要となる揺動運動下での損傷についても調べた．多品種少量生産の加工プロセスとして，旋盤あるいはフライス加工による全機械加工での生産設計が考えられるが，PEEK樹脂を機械要素に用いるには，まだ十分な研究がおこなわれていないため，加工条件が強度・性能に及ぼす影響も評価した．ここでは，PEEK軸受を機械要素として使用する場合に重要な湿潤環境・無潤滑環境下で，焼付き，変形，はく離を評価した．また，PEEKブッシュをリンク機構部材に用いたロボット関節の性能評価に必要な試験機を製作し，損傷の進行が関節の性能に及ぼす影響について明らかにした． 第Ⅰ章第1節では，PEEK軸受にアルミナ玉の接触が及ぼす影響について，第Ⅰ章各節の構成が述べられている． 第Ⅰ章第2節では，PEEK軸受の自己潤滑，フィルムおよび焼付きの影響を明らかにするため，ラジアル型転がり深溝玉軸受を旋盤加工によって作製しドライ環境下での転がり疲労試験を行った．ラジアル荷重領域のうち80Nより下および100Nより上では，それぞれフィルム溶着および焼付けが発生するが，その間の領域では，自己潤滑作用により長寿命を示すことを明らかにした． 第Ⅰ章第3節では，PEEKラジアル玉軸受を旋盤加工によって異なる加工条件で作製し，水潤滑下で疲労テストを行った結果が述べられている．テスト前後の軸受軌道面の状態をレーザー顕微鏡によって観察し，さらに摩耗損失量を調べた結果，き裂が損傷を支配していることを明らかにした．また，ヘルツ接触圧と内部せん断応力分布について，水漬後の試験片を用いて測定したヤング率・ポアソン比をもとに，玉と軌道面の接触楕円の算出を行った．さらに，有限要素法による内部応力分布を計算し，実験で確認された事象と応力分布の比較を行い，き裂深さの力学的考察を行った． 第Ⅱ章第1節では，リンク機構を有するロボット関節に関して高精度・高強度・軽量の観点から，PEEKブッシュとチタン・アルミ合金の組み合わせに注目し，繰返し揺動運動による部材の疲労がロボット関節の強度・精度へ及ぼす影響について，第Ⅱ章各節の構成が述べられている． 第Ⅱ章第2節では，チタンクランクシャフトの接触がPEEKブッシュの摩耗と変形へ及ぼす影響を研究するために開発した計測機および強度疲労試験機について述べられている． 第Ⅱ章第3節では，PEEKブッシュと相手側部材であるチタンとの摩擦・摩耗によって生じるバックラッシを計測するシステムおよびリンク機構の疲労強度試験機が述べられている．さらにこれらの装置を用いて，PEEKブッシュの摩耗，変形，バックラッシの関係から角度に関する精度を整理している． 第Ⅱ章第4節では，PEEKブッシュとアルミ合金カムプレート間の摩耗・変形に起因するバックラッシの影響について述べている．強化PEEKブッシュと超々ジュラルミンのカムプレート間の摩擦が疲労に及ぼす影響を調べ，トルクを負荷させた状態では，バックラッシは疲労にしたがい増加することを明らかにした．さらに，これは，PEEKブッシュのシビア摩耗により表面粗さが大きくなったことが原因であることを明らかにした． 第Ⅱ章第5節では，PEEKブッシュを用いたリンク機構により従来の出力可能トルクの3倍にあたる88.2 Nmで1.0×10^4 cyclesまで関節を動かすことが可能であることを示した．これにより，強化PEEKのもつ摺動性と強度の双方を十分に活かしたリンク機構を有するロボット関節の設計が可能となった． 終章では本論文の総括が述べられている

Flaking of PEEK under one-point rolling contact fatigue using Al

The growth of flaking as tribological fatigue failure in PEEK was investigated through the one-point type rolling contact fatigue test between a machined PEEK polymer shaft and an alumina bearing's ball. Due to Hertzian contact of cyclic compressive stress, the subsurface fatigue cracks in the PEEK shaft propagated in rolling and axial directions. When the rolling fatigue life of the PEEK shaft reached 106 fatigue cycles, many narrow angled cracks occurred in the near-surface of the rolling track without flaking. On the other hand, when the flaking ocuurred on the PEEK shaft before 106 fatigue cycles, semicircular surface and subsurface crack propagations were observed. From these observations, it was found that micro-flaking occurred due to the linkages between subsurface and surface cracks. Flakingdeveloped due to the accumulation of these micro-flakings

Investigation of subsurface fatigue crack in PEEK shaft under one-point rolling contact by using 2.5D layer observation method

Subsurface fatigue cracks under rolling contact area of the PEEK shaft against an alumina bearing’s ball were investigated for application of frictional part in mechanical element in special situations such as chemical environments. In order to explore the flaking process of the PEEK shaft, the rolling contact fatigue tests were carried out by using a one-point radial loading rolling contact machine. The flaking occurred on the rolling track of the PEEK shaft at approximate 4⨉105 fatigue cycles. The subsurface fatigue crack propagation was investigated by using 2.5-Dimension layer observation method. The flaking was caused by the propagations of surface cracks and subsurface shear cracks, and the flaking shape was half-ellipse. Moreover, beach marks as fatigue crack propagation in the flaking were observed

Investigation of wear, groove shape and load capacity of PPS-PTFE hybrid radial ball bearings

In order to improve the radial load capacity and wear loss of the PPS-PTFE hybrid bearings, the groove shape of the PPS inner ring in the PPS-PTFE hybrid bearing was designed based on ceramic bearing’s ball radius (r). The rolling contact fatigue tests were performed by using the PPS-PTFE hybrid bearings with the original (r*1.0) and modified (r*1.1) inner rings. The radial load capacity of the bearing using the rl.1 inner ring was improved 150% over the capacity of the bearing using the r1.0 inner ring. While the operation temperature of the bearing with the r1.1 inner ring was stable at 40 °C, that of the bearing with the r1.0 inner ring incresed rapidly over 100 °C and thermal failure occurred. Moreover, the wear loss of the bearings with the r1.1 inner ring was lower than that of the r1.0. Thus the groove shape influenced the tribology performance of the PPS-PTFE hybrid bearings

Investigation of subsurface fatigue crack in PEEK shaft under one-point rolling contact by using 2.5D layer observation method

Subsurface fatigue cracks under rolling contact area of the PEEK shaft against an alumina bearing’s ball were investigated for application of frictional part in mechanical element in special situations such as chemical environments. In order to explore the flaking process of the PEEK shaft, the rolling contact fatigue tests were carried out by using a one-point radial loading rolling contact machine. The flaking occurred on the rolling track of the PEEK shaft at approximate 4⨉105 fatigue cycles. The subsurface fatigue crack propagation was investigated by using 2.5-Dimension layer observation method. The flaking was caused by the propagations of surface cracks and subsurface shear cracks, and the flaking shape was half-ellipse. Moreover, beach marks as fatigue crack propagation in the flaking were observed

Investigation of wear, groove shape and load capacity of PPS-PTFE hybrid radial ball bearings

In order to improve the radial load capacity and wear loss of the PPS-PTFE hybrid bearings, the groove shape of the PPS inner ring in the PPS-PTFE hybrid bearing was designed based on ceramic bearing’s ball radius (r). The rolling contact fatigue tests were performed by using the PPS-PTFE hybrid bearings with the original (r*1.0) and modified (r*1.1) inner rings. The radial load capacity of the bearing using the rl.1 inner ring was improved 150% over the capacity of the bearing using the r1.0 inner ring. While the operation temperature of the bearing with the r1.1 inner ring was stable at 40 °C, that of the bearing with the r1.0 inner ring incresed rapidly over 100 °C and thermal failure occurred. Moreover, the wear loss of the bearings with the r1.1 inner ring was lower than that of the r1.0. Thus the groove shape influenced the tribology performance of the PPS-PTFE hybrid bearings